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PC3000 User guide Book 2 iss 3.1 - Elektro

1. Instance Name Type Purpose setpoint Select_Real Provides a setpoint value for each segment rate Select_Real Provides a rate value for each segment dwell Select_Time Provides the dwell duration for a dwell segment segno Integer Stores the current segment number segmax Integer Stores the maximum segments in use rampl Ramp Provides the ramping function when in RUN mode Table 5 3 Ramp Dwell Programmer Function Blocks E 0 c S a 2 oO fa PC 3000 User Guide 5 13 Program Development Select Real setpoint Index Output Input_1 Input_2 Input_3 Input 4 Input 5 Input 6 Input 7 Input 8 Ramp ramp 1 up to Input 16 Mode Output Setpoint Rate Select_Real 20 0 Reset Ouput rate Inde x Output Input_1 Input_2 Input_3 Input_4 Input_5 Input_6 Input 7 Input 8 up to Input 16 Selkct Time dwell Index Output T 000 ms Input_1 T 20s Input 2 T 000 ms Input_3 T 000 ms Input 4 T 000ms Input 5 T 000ms Input_6 T 000ms Input_7 T 000ms Input_8 up to Input 16 Figure 5 3 Ramp Dwell Programmer Function Block Diagram The ST soft wiring assignments required are setpoint Index segno Val rate Index segno Val dwell Index segno Val The index parameter of the select functions are all driven by the segno integer user variable By setting a given segment number in segno the outputs of the select blocks provide the setpoint
2. 2 E 6 Eg Soft Wiring D E Dg Task2 100ms o D Seguential function chart Setup Loopl Setpoint 20 0 ABS_REAL Temp1 Process_Val Loopl Setpoint lt 2 0 Heatup Loopl Setpoint 60 0 Temp1l1 Process_Val gt 56 0 AND Heatup Time gt T 30S Cool Loop Set point 20 0 Temp 1 Process_Val lt 24 0 Finish Figure 2 4 Simple Program Example PV_Max PV_Min set these to define the acceptable range of values for the input eg 0 to 100 Note If PV_Max is left at 0 the analogue input status Act_Status may be set to NOGO because the input value is out of range The analogue output channel function block requires a value for Output_type to define the range of the output actuator or drive e g mA4_20 for 4 to 20 milliamps 3 The PID function block also reguires the following configuration parameters pan High Span low set these to match the range of the analogue input Output High Output Low ensure these are set to 100 and 0 percent If Output Low is set to 100 percent the PID will function in dual channel mode heat cool Prop_Band Integral and Derivative set these as required by the controlled process PC 3000 User Guide 2 13 Programming Concepts Manual set to Auto to switch the PID into automatic mode 4 Construct the soft wiring to link the three function blocks i e Loop1 Process_Val Temp1 Process_Val and Heat1 Process_Val Loop1 Ch
3. 5 4 PC3000 User Guide Program Development Stage 4 Create sequencing control strategy S d Start StopPump Heat M Shut_Off Eo Stir Settle T Drain Eee a Lo S Start Macro step The main actions are 1 Create the Main top level SFC Each step should represent a primary process phase Typically steps in the Main chart are defined as macro steps This allows the important process phases to be clearly visible this is especially useful during commissioning 2 Decompose each macro step into yet lower level macros and finally steps to complete the sequence program E 0 c S a 2 oO fa PC 3000 User Guide 5 5 Program Development Stage 5 Create transitions and step actions l BEGIN Heat Loop1 Setpoint 200 0 Valve3 Process_Val 1 OPEN END F Heat Time gt T 30s AND ProdType Val 1 Settle Stir Settle l The main actions are 1 Create the ST for the transition conditions Note Transitions that are not defined will default to 1 i e true or on 2 Create the step actions Note For timing reasons it is acceptable to have steps with no ST actions For example a null step can be used as a wait if it is followed by a transition condition that waits for the step to be active for a defined duration DESIGN OF
4. EUROTHERM CONTROLS PROCESS AUTOMATION RECORDERS PC3000 USER GUIDE Book 2 Languages Copyright Eurotherm Controls Limited 1993 All rights strictly reserved No part of this document may be stored in a retrieval system or any form or by any means without prior written permission from Eurotherm Controls Limited Every effort has been taken to ensure the accuracy of this specification However in order to maintain our technological lead we are continuously improving our products which could without notice result in amendments or omissions to this specification We cannot accept responsibility for damage injury loss or expenses resulting therefrom HA022932 Iss 3 1 CONTENTS Chapter 1 INTRO DUCTION Chapter 2 PROGRAMMING CONCEPTS Chapter 3 STRUCTURED TEXT Chapter 4 SEQUENTIAL FUNCTION CHARTS Chapter 5 PRO G RAM DEVELO PMENT Index PC3000 User Guide Contents Chapter 1 INTRODUCTION Edition 1 Contents OVERVIEW 2s oo ais dei hel ath iin eg ees e 1 1 PC3000 USER G UIDES pinadietan n 1 1 Book 1 PC3000 programming esse ee 1 1 Book 2 PC3000 language ese ee ke ee 1 1 Book 3 PC3000 in application ek 1 2 PC3000 REFERENC ES oe ees ee ee dee 1 2 PC3000 real time operating system reference 1 2 PC 3000 hardware reference ese ke 1 2 PC 3000 functions reference ees 1 2 PC3000 function block reterence ee ee 1 3 ABOUT THIS GUIDE
5. END IF In this case if count is zero the first set of assignments are made if the count is less than 10 but not zero the second set of assignments are made Otherwise the last set are made Where there is an IF THEN construct followed by multiple ELSIF THEN constructs only the set of statements associated with the first true conditional expression is evaluated Note It is good practice to ensure that multiple ELSIF constructs have mutually exclusive conditions to ease program readability PC 3000 User Guide 3 13 Structured Text Further conditional statements can be used within any set of statements of a conditional statement In other words statements using IF constructs can be used within other IF constructs This allows very complex conditional statements to be constructed Each nested IF statement must be terminated with END_IF Example IF zonel Process_Val gt 300 THEN timer Prog_Time T 4s cool Output High 90 0 IF zonel Process_Val gt 310 THEN boost Process_Val 400 0 ELSE boost Process_Val 350 0 END_IF END_IF OPERATORS The operators shown in Tables 3 3 3 4 and 3 5 can be used in PC3000 Structured Text expressions Arithemetic operation Operation Symbol Data Types Addition af Floating point REAL Integer DINT Subtraction Floating point REAL Integer DINT Note 1 Multiplication Floating point REAL Integer DINT Di
6. Output Testing By placing output channel function blocks in a test mode it is possible to directly provide test values to the physical outputs irrespective of the state of the normal PC3000 control program This can be useful when testing physical wiring and the connection between hardware channels and the physical actuators When output channels are in the test mode the values written to the channel function blocks by the program are not written out to the physical outputs Caution Ensure that all test enable parameters of all input and output channel function blocks are set to off in PC3000 programs that are running production processes 5 18 PC 3000 User Guide Index INDEX Action Oualifier Pulse IEC 1131 3 4 7 Actions steps 3 2 terminology 1 4 Actions 4 2 Addition 3 15 ATOS8 5 3 Alarm condition 2 15 monitoring 5 1 signal 2 15 Alarms 2 1 Alternative sequences 4 2 Alternative transitions 4 3 Analogue input 2 12 Analogue control continuous 5 3 Analogue control 2 15 Analogue output channel 2 14 Applications 2 1 Assignment terminology 1 4 Assignment 3 9 10 Boolean BOOL 3 4 expression 1 4 expressions 3 19 Boolean expression 4 2 Brackets 3 18 Calendar date DATE 3 6 Calendar Date and Time of day DATE_AND_TIME 3 6 Character non printable 3 7 Chart MAIN 4 11 terminology 1 4 Class COMMS 5 9 CONTROL 5 9 COUNTERS 5 11 FILTERS 5 11 INPUTS
7. BOO Executing TIME TIME Finished H Boor Figure 4 12 Step and Macro Function Blocks The macro function block is used for macro and abortable macro steps Both blocks have Executing and Time parameters The Executing parameter abbreviated X is set whenever the step or macro is active The Time parameter abbreviated T provides the duration of the step or macro The value of this parameter is reset when the step is first activated and then increases while the step is active When the step is deactivated the value is frozen This parameter can be used to time the duration of a step It is also a useful diagnostic aid because it records the length of time a program was in a given step the last time it ran The Finished parameter abbreviated F provided with the Macro function block is set when the macro chart reaches the end step It is always cleared when the macro step is not active It can be used in transition conditions to test whether a particular macro chart has finished SFC PROGRAMMING RULES Rules for using charts The following points always apply to charts 1 The top chart called MAIN provides the top level overview of the entire sequence program 2 A lower level chart is associated with a macro step or an abortable macro step in the next higher level chart 4 12 PC 3000 User Guide Seguential Function Charts 3 A chart may contain a number of steps and transitions connected by
8. Instantiation The process of creating Function Blocks of a particular function block type PID Proportional Integral and Derivative control algorithm SFC Refers to the IEC Sequential Function Charts language and construction ST Refers to the IEC Structured Text high level language Statement A Structured Text language statement is a collection of language keywords operators and functions that performs a specific purpose and is terminated with a semicolon Step A Step within the Sequential Function Chart that defines a particular process state or phase and is represented by a rectangular box Transition A short horizontal line that represents the point where there is a change ie transition from a step s to another step s It represents a decision point at some stage in the process On meeting the condition control passes from the current step s to the next step s Transition Condition The condition that when true causes the transition between active steps When using the PC3000 Programming Station is defined as a boolean expression in Structured Text On meeting the transition condition control passes from the current set of steps to a new set of steps 1 4 PC 3000 User Guide Programming Concepts Chapter 2 PROGRAMMING CONCEPTS Edition 2 Contents OMERVIEW ES ees 2 1 Background i e EE ER RE Ee RE Ee Re a 2 1 IEG 1131 3PLC STANDARD ies see eis sees ee Ge SERE Ge geen 2 2 Mullistaskin
9. Sequential Function Charts SELECTING ALTERNATIVE SEQUENCES Alternative parts of a sequence can be selected by having multiple transitions from a step as shown in the figure 4 3 example a From Step Load there are three possible alternative steps that can be activated The selection depends on which one of the three transitions is true first while Load is active Examples where alternative sequences are useful When the process phases need to vary depending on the type of product being made such as depicted in the figure 4 3 e Where a special set of actions are needed following a process failure i e fault recovery e Where it is necessary to repeat a set of steps a number of times and then enter an alternative sequence when the end condition is reached The PC3000 operating system evaluates transitions from left to right In this example if all three transition conditions are true only the Heat step will be selected Note Where there are alternative transitions only one of the successive steps will be activated even when more than one transition condition is true Load a E Ke Heat Press Cool 2 S e 7s E fa e E a Settle Thaw k fo Unload Figure 4 3 Alternative Sequence Selection Alternative sequences can re join other sequences by linking the transition of the last step to a step in a different sequence see figure 4 3b
10. USER_VAR User variable Function Blocks are Boolean Real Integer provided to hold internal values all Time String data types including floating point integer time and string are available REMOTE_VARS Remote variables allow parameters Remote_Bool of various data types to be read from Remote_Real external equipment using specific Remote_Str communications drivers SLAVE_VARS Slave Variables provide values that Slave_Bool are addressable by specific Slave_Real Slave_Int communications protocols i e by Slave_Real_8 external equipment RECIPE Recipe Function Blocks provide RecipeMan recipe storage and selection StageMan facilities Name_1x128 Real_16x128 5 10 PC 3000 User Guide Program Development Class Purpose Examples STEPS The steps Function Blocks are Macro Step Created automatically when a SFC is developed There are two types Step Macro COUNTERS Provides Function Blocks for Up Counter counting both up down and Dn Counter up down Up Dn Count SELECT The select Function Blocks allow Select Real one of a set of values to be selected Select Int by a single integer input A variety Select Time of data types are provided Select Bool Select Str FILTERS Provides Function Blocks for Lag freguency filtering of analogue signals LOADS These Function Blocks provide PID_Load VP_Load simulutaions of different types of control loads Used with PID b
11. all input parameters are given a standard set of default values In many cases these values can be left unchanged where the default values suit your application or if a particular feature of the function block is not required All values assigned to input parameters as constants e g setting a PID Prop_Band parameter to 6 00 are used to reset the function block when it is initialised i e used for Cold Start values When PC3000 runs each function block copy or instance runs entirely independantly of any other instance For example RampPump could be in Hold state while RampTemp and RampPres are ramping to different setpoint values When a function block executes the output values will in many cases change for each execution even when the value of all the function block s input parameters are left unchanged This is because the function block has internally stored variables that are used to accummulate values for counters integrated values etc For example while the Ramp function block is in Run mode the Output will increase on each subsequent function block execution until the ramp setpoint is reached although all the input parameters remain unchanged VO Function blocks For consistency the gathering of input values from sensors and delivering output signals to actuators heaters etc is handled by input output I O function blocks For example the analogue input function block Analog_In provides a range of input parameters
12. and c PC 3000 User Guide 4 3 Sequential Function Charts PARALLEL SEQUENCES Sequences to run in parallel can be defined by linking them with a double horizontal line which follows a single transition see Figure 4 4 a Start a Purge Load Pres_Chk f f Heat HoldLoad Shut_Off F F Stir Unload Finish Figure 4 4 Parallel Sequences In figure 4 4 when step Start is active and the condition for transition at a is true steps Purge Load and Pres_Chk are activated simultaneously This initiates three sequences to run in parallel Parallel sequences may be required where there are a number of process operations that can proceed independently Figure 4 4 shows three sequences to control a reactor vessel a job loading mechanism and pressure checks The Programming Station allows up to 12 parallel sequences to be initiated from one transition Other transitions can initiate further parallel sequences on the same chart if required In many control applications there is often the need to wait for a number of parallel sequences to end before proceeding with the next part of the main sequence This can be achieved using a parallel sequence rendezvous as depicted in figure 4 4b by a double horizontal line joining a number of parallel sequences A rendezvous is always followed by a single transition 4 4 PC3
13. ramp rate and dwell values for a selected 5 14 PC 3000 User Guide Program Development segment A dwell segment is characterised by the rate Select Real function block producing an output of 0 0 i e a null ramp rate In figure 5 3 the select function blocks are set up to have 4 segments Segment 1 Ramp to 100 at 1 1 units seconds Segment 2 Dwell for 20 seconds Segment 3 Ramp to 200 at 2 5 units seconds Segment 4 Ramp to 300 at 3 2 units seconds BEGIN segro Val 0 Setup ramp1 Mode 0 Reset rate Output gt 0 0 AND END NextSeg Time gt Task2 Interval Setup Time gt Task Interval BEGIN BEGIN ramp1 Setpoint setpoint Output NextSeg segno Val segno 1 ramp1 Rate rate Output END ramp1 Mode 1 RUN END rate Output lt 0 0 AND segno Val gt segmax Val NextSeg Time gt Task2 Interval BEGIN Finish Ramping Dwelling ramp1 Mode 2 Hold END ramp1 Sepoint ramp1 Output dwelling Time gt dwell Output NextSeg e NextSeg Figure 5 4 Ramp dwell Programmer SFC Figure 5 4 depicts the steps and transitions reguired to control the ramp dwell programmer and should be regarded as part of a larger SFC The Setup step resets the segment number to zero and puts the ramp1 function block into RESET mode At this point the output of ramp1 function block will be reset to the value of the Reset_Output parameter which in
14. 5 9 LOADS 5 11 MODULES 5 9 OTHERS 5 11 OUTPUTS 5 9 RECIPE 5 11 REMOTE_VARS 5 9 SELECT 5 11 SLAVE_VARS 5 9 STEPS 5 11 SYSTEM 5 9 TIMERS 5 9 USER VAR 5 9 Closed Loop Control 2 1 Comments 3 2 Commissioning 5 1 17 Conditional expressions 3 1 Conditions 3 2 Configuration parameters 2 12 Continuous control 2 11 Continuous steps 4 9 Control closed loop 2 1 continuous 2 11 continuous digital 5 5 long loop 2 2 overview 1 2 PID loops phases 5 1 strategy 5 1 sequencing strategy 5 5 statistical process 2 2 7 strategies 5 9 Counters 1 3 PC 3000 User Guide Index 1 Index Data type 3 3 9 types 3 2 7 Default communications 2 11 Deterministic performance 2 5 Digital inputs 2 15 Logic 2 15 Discrete instruments 2 5 Discrete instruments 5 2 Division 3 15 Drives 5 2 Duration TIME 3 5 ELSE 3 12 ELSIF 3 12 13 END_IF 3 12 Engineering units 2 12 Enumerated Integer DINT 3 3 Eurotherm communications protocol Bisync 2 11 Executing parameter 4 7 8 Execution order 2 17 Expression terminology 1 4 Expressions complex 3 12 sub 3 12 Expressions 3 10 21 External devices 2 11 External drives 2 7 Fault recovery 4 2 FBD 2 2 Feedback soft wiring 5 8 Feedback 5 7 Filters 1 3 Floating point REAL 3 3 calculations 2 17 type of data 3 1 Function DINT_TO_REAL 3 9 Function block concept 2 7 diagram 2 2 diagrams 2 11 example 2 7
15. Load on the higher level chart to the start step Pump on the macro chart when the transition from Load to Process becomes true The transition from Process to Unload is only evaluated when the macro chart end step Depress is reached When this transition is true and step Depress is active the sequence returns to the top level chart at step Unload Macro charts can call further macro charts to a level of 20 so that complex hierarchies of sequences can be created PC3000 User Guide 4 5 Seguential Function Charts Note It is good practice to ensure that the main chart only depicts the primary process steps Typically the primary steps will be macro steps which represent lower level charts Abortable macro steps An Abortable Macro Step provides a mechanism to deactivate all steps in lower level macro charts When an abortable macro step is active the lower level macro chart is activated from the start step i e as for a normal macro step However in this case transition following the macro step is continually evaluated If the transition condition becomes true all steps in the lower level macro chart including those in yet lower level macro charts arising from macro steps are deactivated This can be useful where a complex sequence needs to be cleared down rapidly for example to shut down an automatic load sequence when a manual switch is depressed Macro chart L
16. are Batch 723XA Current Batch Identity 0A01 PV Address Port OA instrument 1 PV ADD REAGENT X1 Operator Message Strings in ST are enclosed between apostrophe characters These characters are automatically inserted by the Programming Station when a string constant is created It is possible to insert a non printable character into a string by typing a dollar sign followed by the ASCII code in hexadecimal E g to insert the bell character that will produce an audible sound on some operator stations type 07 The full ASCII code is given in the PC3000 Function Block Reference Non printable characters may be required to format textual messages to be issued to a printer Additional Integer Data Types The majority of integers used in PC3000 function blocks and functions are of the DINT data type However in a few rare cases parameters can be defined using integer data types listed in table 3 1 PC 3000 User Guide 3 7 Structured Text IEC Data Type Description Size in Bits Range SINT Unsigned Short 8 128 to 127 Integer USINT Unsigned Short 8 0 to 255 Integer INT Unsigned Integer 16 32768 to 32767 UDINT Unsigned Double 32 0 to 42944967296 Integer Table 3 1 Additional Integer Data Types for Function Block Parameters The Table 3 1 data types described as unsigned imply that only positive values can be stored Caution Care should be taken whe
17. date and times ADD DATE AND TIME T SUB DATE AND TIME T ADD TOD TIME Compact Functions allow multiple EXT REAL FROM STR values to be compacted to REP REAL IN STR and from long strings for EXT TIME FROM STR serial communication REP TIME IN STR Table 3 8 ST Function Categories Continued 3 20 PC3000 User Guide Structured Text Many of the mathematical functions involve complex floating point arithmetic and therefore in order to minimise performance overheads these functions should only be used sparingly in soft wiring associated with function blocks running at high scan rates e g in soft wiring to digital function blocks A full list of functions is provided in the PC3000 Functions Reference Examples of ST using functions light Process_Val EXPT BASE 2 0 POWER rate Val GI light is given by raising two to the power of ee SEH upTime Val UDINT TO TIME Text IN pulses Val spaces Val Structured pulses scaled by spaces gives milliseconds upTime The function parameter names are inserted automatically by the Programming Station when a function is inserted The values provided to function parameters may involve complex ST expressions providing the result of the expression is the same data type as the particular function parameter The Programming Station will check that the expressions generate the correct data type for the fun
18. execution order 5 7 Instance 1 4 library 2 7 macro step 4 12 Ramp 2 7 Ramp 5 12 reference 1 3 SFC Interaction 4 10 step 4 12 String user variable 3 7 type 5 11 Function Block 2 5 Function blocks functionality 5 16 T O 2 8 input channel 2 16 inter connected 2 9 software overview 2 11 Function blocks 2 1 Function key Main feedback 5 7 Functions categories numerical 3 20 compact 3 20 mathematical 3 21 selection 3 20 21 string 3 20 string conversion 3 20 time arithmetic 3 20 type conversion 3 20 Functions 3 2 Functions 5 16 Index 2 PC3000 User Guide Index Grafcet 2 2 Hardware modules 1 2 Hardware modules 2 12 VO channels 5 2 3 VO Address 3 8 VO function blocks 2 8 11 ICM 5 3 IEC 1131 3 multi tasking 2 5 PLC Standard 2 2 standard 3 22 Structured Text 3 1 system 3 23 TEC 1131 3 2 1 IF 3 12 IF construct 3 23 IF THEN 3 23 Incomplete rendezvous 4 17 Instantiation 1 4 INT 3 8 Integer DINT 3 3 Integrity 5 9 Interfaces to VO 2 11 Interlocks 2 1 Interlocks 5 1 JBus 2 11 Logic functions 2 11 Long loop control 2 2 Macro abortable 4 11 abortable step 4 6 steps charts 4 5 steps 5 5 Macro step 4 2 Main process phases 5 6 SFC 5 6 MAIN 4 12 Main chart 4 5 Main chart 5 5 16 Mathematic calculations 3 1 Microcell Programming Station 1 1 Microcell Programming Station 2 11 Modbus 2 11 M
19. first and has higher precedence than the addition operator Operators of equal precedence are evaluated left to right The precedence can be modified by inserting brackets round expressions that should be evaluated first Example total Val a Val 10 b Val 20 In this case b Val is multiplied by 20 10 is then added and the result is multiplied by a Val If you have any doubts about evaluation order insert brackets round expressions that you expect to be evaluated together Operator Symbol Precedence Parenthesization C HIGHEST Negation Complement NOT Multiply Divide Modulo MOD Add Substract Comparison lt gt lt gt Equality Inequality lt gt Boolean AND AND Boolean Exclusive OR XOR Boolean OR OR LOWEST Table 3 6 ST O perator Precedence BOOLEAN EXPRESSIONS Boolean Expressions always produce a boolean BOOL result i e the value is either 1 for true or 0 for false This type of expression can be used to describe process boundary conditions or events within conditional statements or SFC transitions A boolean expression can involve any of ST operators and functions but must result in a final boolean value 3 18 PC3000 User Guide Structured Text Examples gasFlow Process Val gt valvePos Process_val 300 0 flow Val diginl Process_Val AND heat1 Process_Val lt 250 0 AND soak Time gt T 40m v
20. formalised by the IEC 1131 3 standard allows proven software components with functionality similar to PC 3000 User Guide 2 5 Programming Concepts real instruments to be connected together to form complex control systems simply by software a concept called soft wiring A function block contains an encapsulated program or algorithm which can be accessed and controlled externally by a set of parameters It is encapsulated so that the systems engineer need not be aware of the way the function block has been designed internally In fact the only access to the function block is via a set of formal parameters provided by the original designer Normally a function block will have a set of input parameters which can be used to connect or soft wire to other function blocks Input parameters can be driven from live control signals originating from the plant or assigned values by external devices such as operator stations and supervisory systems The input parameters can be used to modify the function block s behaviour Each time a function block executes which depends on the task it is associated with it is run using the current input parameters and other internally stored data The internal algorithm then updates the output parameters Function blocks in some form have been used in control instrumentation for many years For example the PID algorithms that run is discrete instruments such as Eurotherm Controls 818 and 900 EP
21. input and output using the hardware configuration screen for example using modules such as AI4 and AO4 In this example the analogue input is driven by channel 1 of module 2 and the output drives channel 2 of module 4 both in rack 1 2 Assign values for the configuration parameters to customize the input and output The analogue input channel will normally require values for the following parameters Input_type e g Range_3 Check the Data sheet for the range supported by a particular hardware module In this case Range_3 selects 10 to 5OmV operation Lin_Type to set the linearisation type e g J for a type J thermocouple CJC_Type to set the type of Cold Junction Compensation e g intern for internal Pre_Scaler Pre_Offset Post_Scaler Post_Offset to set the scalers to scale and offset the input signal before and after linearisation These parameters are used in conjunction with PV_Max and PV_Min to produce the required engineering units ie 0 to 100 degrees C The values 1 0 and 0 0 for both scalers and offsets should be suitable for this example E g Post_Scaler to 9 5 and Post_Offset to 32 would produce a value in degrees F With Post_Scaler set to 1 and Post_Offset to 0 will produce a value in degrees C 2 12 PC 3000 User Guide Programming Concepts Task2 100ms Analog In PID Analog Out Templ Loopl Heatl IO Address Process Val Process Val TO Address Ch1 Output Process Val Set point
22. of an active continuous step are executed every time the SFC is scanned However note that actions are also executed once more after the 4 8 PC 3000 User Guide Seguential Function Charts step has been deactivated see figure 4 10 This facility is provided so that continuous steps can have actions to close down certain functions on exit IF Pumping Executing 1 ON THEN Pump Process Val input Process Val c Pumping ELSE Pump Process_Val 100 0 END_IF Pumping Time gt T 1h Figure 4 10 Execution of Continuous Step Actions on Exit Figure 4 10 depicts an example of a continuous step where an assignment is made when the step is deactivated While the step Pumping is active the Pump Process Val is continually updated from input Process_Val However when the step is deactivated the Pump Process_val is reset to 100 0 The step parameter Executing abbreviated X is used to select actions to occur when the step is active and those that occur once when the step is deactivated i e when it is off also see Step and Macro Function Blocks Timing actions within continuous steps The Time parameter of a Continuous step is continually updated while the Continuous step is active This can be used to cause certain actions to occur at various times after the step has started Example c IF shutdown Time lt T 1m THEN 2 9 pumpl Process Val 30 6 cs ELSE ET pumpl Process Val
23. this example has the value 20 0 PJ c O 2 S D a The transition from the Setup step waits for the step to be active for one task scan to ensure that the function blocks have executed before proceeding This example assumes that the SFC is executed in Task_2 the normal default In which case the step should wait for the duration of one scan of Task_2 The task scan time is provided by the parameter Task 2 Interval PC3000 User Guide 5 15 Program Development In step NextSeg the segment number held in user variable segno is incremented Following NextSeg there are transitions to three alternative steps Remember that the transitions are evaluated from left to right The left most transition checks whether the end segment has been reached by comparing the segment number with the user variable segmax The other two transitions wait for Nextseg step to be active for one task scan to allow the select function blocks to execute to produce the correct outputs for the current segment The middle transition then checks whether the currently selected segment has a non zero rate in order to select the ramping step The right most transition checks whether the rate is zero in order to select the dwelling step The ramping step sets up the ramp1 function block to increment its output to the setpoint and rate as produced by the select function blocks The ramp1 function block is then switched into R
24. this is discussed in Chapter 4 SFC Programming The PC3000 mode is displayed on the main menu of the PC3000 Programming Station when in on line mode Use the command RUN to switch the PC3000 into the RUNNING mode All the function blocks in this example are associated with analogue control and all execute in Task2 which by default runs every 100 ms The SFC also executes in the same task but remember that only the active step and it s associated transition conditions are evaluated every 100 ms g 8 D E E re ey H KE ou For further system details on timing and execution of SFCs and function blocks refer to PC3000 Real Time Operating System Manual Digital Logic To complete this example figure 2 5 shows how a simple alarm condition can be added by using digital function blocks These are inter connected using soft wiring in exactly the same way as the analogue blocks The example assumes that an alarm signal is required to switch off power to the process whenever either of two doors Door1 and Door2 are opened and the temperature of the process is greater than 50 0 VO channel function blocks for digital inputs Door and Door2 provide the state of doors for example by connecting the hardware digital inputs to micro switches The alarm output signal is driven by a digital output function block Alarm The Alarm Process_Val input parameter is soft wired using an ST expression that involves both the process value
25. transition may to be true immediately after the step is active This is due to the rampSP Ramp_End parameter still being true from a previous execution of the rampSP function block In the second case the transition condition has been modified to ensure that the rampSP executes as least once before testing the Ramp_End parameter This example assumes that the rampSP function block is in a 100 ms task Note Always ensure that time is allowed for function blocks to execute after setting input parameters and then testing the values of function block output parameters 4 10 PC 3000 User Guide Seguential Function Charts STEP ATTRIBUTES Start Specifies that the step will be made active when the chart that contains it becomes active End Normally the last step of a macro step The condition of the transition following a macro step will be tested when the End step in the associated macro chart becomes active If the transition condition is true the End step becomes inactive and the macro chart that contains it completes execution However the End step of the MAIN chart is a special case which when active executes once and the entire SFC is then completed A normal non abortable macro must contain one end step An abortable chart may contain one or zero end steps Normal This is the default attribute which is not explicitly set on the default Programming Station implies that the step is neither a start nor an e
26. wiring i e graphical lines that define the flow of control from one set of active steps and their associated transitions to the next 4 A chart must have exactly one start step 5 A chart must have one or zero end steps An active chart is one that has one or more active steps Rules for using Steps The following points always apply to steps 1 A step may be a Macro that represents another SFC chart or it may be defined as a set of actions using the ST language 2 A step normally has one or more following transitions except a End steps which never have a following transition and b a step may optionally have no succeeding transitions if it is always required to stay active once reached A Continuous step with no following transition stays active 3 A step cannot be immediately followed by another step without an intervening transition 4 A step may have an attribute that defines how it is executed Rules for using transitions The following points always apply to transitions 1 Every transition must always have one or more preceding steps and one or more succeeding steps S 8 5 T e K 2 A transition can never be connected to another transition A transition represents a condition that must be fulfilled before its associated preceding step s are deactivated 4 A transition condition is described using a boolean expression in ST UNSAFE SFC DESIGN The Programming Station c
27. 0 amp END_IF Valvel Process_Val shutdown Time gt T 2m In this example assume that shutdown is a Continuous step that is active for say 4 minutes timed by the step s following transition The Structure Text statements for the step actions ensure that process value of pump is set to 30 during the first minute thereafter set to 0 The Valvel process val is true i e the valve is switched ON after two minutes PC 3000 User Guide 4 9 Seguential Function Charts SFC AND FUNCTION BLOCK INTERACTION Care should be taken in cases where function block parameter values are set up in a step that is immediately followed by a transition that tests whether the function block has completed a particular operation Remember that a particular function block may not have time to execute between setting values in the step and testing the result in the transition R rampSP Setpoint 300 x Seam rampSP Mode 1 RUN rampSP Ramp_End 1 True R rampSP Setpoint 300 Be amp rampSP Mode 1 RUN rampSP Ramp End 1 True AND StrtRamp Time gt T 100ms Figure 4 11 SFC and Function Block Interaction Figure 4 11 depicts a common problem that can occur The step actions set up a ramp function block rampSP to ramp to a particular setpoint The transition is required to wait for the ramp to complete In the first example the transition may fail to detect the end of the ramp because the
28. 000 User Guide Seguential Function Charts Note The condition for the rendezvous transition is only evaluated when all connected preceding steps are active When it is true all preceding steps are deactivated and the following step or steps is activated A rendezvous may be reguired where several seguences must be finished before proceeding For example you may need to ensure that a reactor vessel is drained the product has been unloaded and pressure checks have been shut off before opening a vessel door MACRO STEPS AND MACRO CHARTS The Programming Station allows complex sequences to be built up from a hierarchy of Sequential Function Charts The top level chart is displayed when the SFC editor is first viewed on the Programming Station and is referred to as the Main chart A step can be created as a Macro step by assigning the Macro attribute This implies that the step represents a lower level macro chart Each macro chart must have a single step identified as the start step When a macro step is activated it causes the start step of the lower level macro step to become active Macro chart Load y j Pump E T E SI M Process Anneal E e rs wes n Ke Unload sE Depress Figure 4 5 Calling a Macro Chart from a Macro Step Figure 4 5 shows a simple example of a macro Step Process that represents a lower level macro chart The sequence transfers from step
29. 1 Integer DINT All time and date data types Greater than or gt Floating point REAL equal Integer DINT All time and date data types Less than or equal lt Floating point REAL to Integer DINT All time and date data types Table 3 4 Structured Text Comparison Operators Note 1 It is normally not advisable to test equality of floating point values as smalling rounding errors can cause the test to fail unexpectedly e g 3 43212 2 6 86424 may be false These operators can be used to compare the values of floating point integer and time and date data types i e the IEC data types REAL DINT TIME TIME_OF_DAY DATE DATE_AND_TIME The two values being compared must be the same data type These operators always return a result of boolean BOOL data type and are typically used to define process boundary conditions Examples purge Time gt T 4m Purge step duration greater than or equal to 4 minutes loop1 Setpoint gt 300 0 Loop Setpoint over 300 0 3 16 PC3000 User Guide Structured Text Boolean operators Operation Symbol Data Types Boolean AND AND Boolean BOOL Boolean OR OR Boolean BOOL Boolean XOR Boolean BOOL Exclusive OR Note 1 Inverse or contrary NOT Boolean BOOL Boolean sense Note 2 Table 3 5 Structured Text Boolean O perators Note 1 The exclusive OR operator XOR is useful where it is necessary to evaluate whether o
30. 1_Output When using the PC3000 Programming Station these statements are attached to the input parameter of the function block to receive the value in this case Loop and Heatl Note Wiring statements are created at the DESTINATION parameter Further details on hardware configuration may be found in the PC3000 Hardware Reference handbook The continuous control part of this simple example is now complete and if this program is now compiled built and downloaded into the PC3000 the three functions blocks will behave as a simple single loop controller The loop setpoint can be set by changing the PID input parameter Loop1 Setpoint Sequencing The control loop is sequenced by a small SFC with steps Setup Heatup Cool and Finish The Structured Text for each Step and Transition is shown alongside the SFC in figure 2 4 The Setup step establishes an initial setpoint of 20 0 and waits for the process value to settle During the Heatup step the process is driven to a higher setpoint of 60 0 The Heatup step continues until the process value has reached a threshold value of 56 0 and has been active for period of more than 30 minutes The Cool step is then activated which changes the setpoint back to 20 0 When the process value has cooled to below 24 0 the SFC terminates by entering the Finish step To program the SFC using the Programming Station the following actions are required 1 Use the SFC editor to create a four step SFC in th
31. C instruments behave as function blocks The PC3000 has an extensive library of function blocks from which the systems and control engineer can build complex applications The library includes PID and Valve Positioner function blocks with auto and adaptive tune Timers Counters Filters and Bistables There are also blocks for specific applications for example for building Recipe Management systems for communicating with other proprietary devices such as PLCs and for real time Statistical Process Control SPC With function blocks you are able to plug and play and develop new and novel solutions to process problems 2 6 PC 3000 User Guide Programming Concepts Function block example Parameter data types Figure 2 2 depicts a Ramp Function Block which can be used wherever there is a reguirement to generate a value that increases at a constant rate The Ramp function block will ramp the output parameter actually called Output towards the value of the Setpoint input parameter at rate determined by the Rate input parameter Function block type Inputs O utputs ENUM REAL REAL REAL ENUM REAL REAL ENUM ode REAL Setpoint F BOOL Rate Ramp_Act BOOL Reset_Out put HB_Active LG BOOL HB Mode HD Deviation process Val Rate Units Parameter data types Figure 2 2 Function Block Example The function block also supports a hold back mode whereby the Output can track the v
32. Ee ee Ge ge GER ve Ge ERK ee ee 3 12 Conditional Ssatements A 3 12 OPERATO RS 3 see EEUE ee GER DER Des peed Ee Ee eende 3 14 Arithmetic operation ee ee ee Re ke 3 14 Comparison Operators ke ee ke ee 3 16 Boolean Operators ee ke ee ke ke ee 3 17 O perator precedance ee ke ke ee 3 18 BO O LEAN EXPRESSIONS ee ee ede ee ee ee ee ee ee ee 3 19 ENGEN SEE GE EE EER EE 3 20 VALUE SELECTION eed ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee 3 21 Selection fUNCHONS ee ee Re AR RR AR Re ee 3 21 Value selection using IF construct 3 23 RULES FOR WRITING VALID STRUCTURED TEXT 3 24 PC3000 User Guide Cont i Structured 3 Structured Text OVERVIEW This Chapter discusses The features of the Structured Text language Where Structured Text can be used in PC3000 programs e How different types of data can be handled in Structured Text e How to use functions within Structured Text e Good Programming style for Structured Text Introduction to structured text Structured Text abbreviated as ST is a high level textual language which has been formalised by the IEC 1131 3 PLC Programming Languages standard for use in programming controllers for industrial manufacturing processes ST provides a wide range of features that make it particularly suitable for programming the control of industrial processes E e e All variables used within the language can be given meaningful names such as g d pumpRate Set
33. Guide Program Development values It is then possible to change the values when the system is being commissioned 7 Become acquainted with the functionality of all the different types of function blocks and functions In many cases complex problems can be solved using existing functionality COMMISSIONING PROGRAMS The PC3000 Programming Station provides on line access to all function block parameters This allows the PC3000 control program to be monitored as it operates in real time The various Sequence Function Charts can be viewed to identify active steps and macro steps This provides a good indication of the process or machine state Sequence held up If a particular sequence is held up at a certain step view the ST defining the condition of each transition that follows the step This will allow the reason to be rapidly located Identify the ST boolean expression that you would expect to be true On the PC3000 Programming Station the live value of each function block parameter used in the expression is displayed on the bottom line of the Transition ST screen If the sequence is held up by a macro step view the lower level macro chart until the faulty step is located If this is also a macro step continue down the chart hierarchy until the step that is held up is located then check each of its transition conditions If a rendezvous transition fails to cause its following step to be activated check that each step lea
34. Guide 3 23 Structured Text RULES FOR WRITING VALID STRUCTURED TEXT The Programming Station checks that all Structured Text statements have the correct structure i e syntax and in some cases that data types used in expressions are consistent However it is good practice to always write correctly structured ST and use the operators with the correct data types The main points to be considered are 1 Ensure that each statement is terminated with a semi colon including each conditional statement 2 Check that constructs such as IF THEN are correctly structured and terminate with END_IF 3 Expressions should deal with consistent data types 4 Operators should be used correctly For example all operators except and NOT should be between two parameters constants or expressions Examples of invalid expressions switch Val a Val AND OR b Val xX heat Val 100 0 O2flow Val 5 Use operators with matched data types This may require the use of TYPE_CONVERSION functions to ensure that parameters or expressions are converted to the correct data type 3 24 PC 3000 User Guide Chapter 4 SEQUENTIAL FUNCTION CHARTS Edition 2 Contents OVERVIEW EE 4 1 Introduction to sequential function hart 4 1 SELECTING ALTERNATIVE SEQ UEN CES 4 3 PARALLEL SEO UENCES ureien ninani 4 4 MACRO STEPS AND MACRO CHARTS ees see ee 4 5 Abortable macro siet 4 6 Deactivating Steps te
35. Purpose Gerneral purpose data type for all floating point i e decimal values This data type is used for storing all analogue floating point values both positive and negative values and large and very small fractional values e g 100 56 100245 21 0 000233 Integer DINT Range Size in Bits Purpose 2147483648 to 32 Gerneral purpose data type for 42147483647 holding integer values eg for counters E 5 This is used for holding integer values i e whole numbers and is used for counts g d batch numbers etc A large range of positive and negative values can be stored F e g 12 1235687 100040 ID Enumerated Integer DINT Range Size in Bits Purpose 2147483648 to 32 Gerneral purpose data type for 42147483647 holding integer values that have a defined set of named values eg for modes status This data type sometimes abbreviated as ENUM uses the same storage size as a the integer DINT but has names associated with a defined set of values These names are displayed on the PC3000 Programming Station and are provided to aid readability PC 3000 User Guide 3 3 Structured Text For example the PcsSTATE function block which defines the current state of the PC3000 control system has an output parameter Battery Cond battery condition that is an enumerated integer This has named states Good 0 Low 1 Faulty 2 The appropriate name is
36. SS ese ig se E eg Re ds eed ge Ee 1 3 TERMINO LOGY AND ABBREVIATIONS ee ee 1 4 PC3000 User Guide HA022932 Iss 3 Cont i Introduction OVERVIEW PC3000 is the first of a new generation of programmable process controllers which can be used to control both production and prototype processes To develop control programs for the PC3000 Eurotherm Controls provide two advanced programming stations the DOS based Programming Station which is fully described in this User Guide and the Microcell Programming Station which provides full graphical and spreadsheet programming along with integrated mimic screens and recipe management Both Programming Stations offer a full repetoire of facilities accessed by menus and user friendly screens These both provide the control and system engineer with a work station that is specifically designed to ease the task of developing control programs through all phases from initial concept development commissioning to on line operation Each system also provides built in help information so that descriptions of many functions and editors can be accessed directly from the screen In order to allow you to fully exploit the rich functionality of PC3000 further information is also provided by a suite of user guides and reference manuals PC3000 USER GUIDES To help you use the PC3000 Programming Station the user guides are arranged as a set of four books Each book contains one or more manuals and is str
37. THE MAIN SFC It is good programming practice to follow top down design principles This implies that the Main SFC should represent the main process phases or primary control sequences S d ReStart SE A VesselA A VesselB A PanelCon EN ar mas Je ReStart Goto returns to ReStart Figure 5 1 Main SFC Example 5 6 PC 3000 User Guide Program Development Figure 5 1 is an example of a Main top level SFC for a control program that handles two reactor vessels Each of which are independantly controlled by two abortable macro steps VesselA and VesselB A third abortable macro step PanelCon controls a operator panel that provides a real time display of selected control parameters for both vessels These steps run in parallel and have no direct interaction The control program is initialised by macro step ReStart that sets up the control loop setpoints etc The transition a waits for the operator to acknowledge that process can re start by typing in a command on the operator panel The condition for the transition at b tests a digital input that is connected to a manual shut off key On detecting that the key is made this transition causes all three parallel steps to be aborted The sequence then returns via a goto to the start step ReStart FEEDBACK IN FUNCTION BLOCK SOFT WIRING Normally the function block execution order in any scan is such that function bl
38. UN mode The transition from the Ramping step simply waits for the output of the ramp function block to reach the setpoint value and then returns to NextSeg for the next segment The dwelling step switches the ramp1 function block into HOLD mode so that the output remains unchanged The transition from this step waits for the dwelling step to last for the segment dwell time and then returns to NextSeg GOOD PROGRAMMING STYLE When developing programs the following points should be considered to improve program readibility and consequently make the program easier to commission and maintain 1 Where possible use meaningful names for function blocks and steps 2 Use meaningful sense names for digital values e g UP DOWN SHUT OPEN This is particularly important if a digital input or output has inverted logic such as 1 meaning OFF 3 Insert comments to describe complex pieces of Structured Text 4 Use a top down approach to the SFC structure with the Main chart depicting the primary process states 5 Use sequences wherever possible in place of state machines built from logic in continuous soft wiring For example use a step in place of setting a boolean user variable to define that a machine or process is in a certain state 6 Avoid having constants in ST that may need to be changed when the system is commissioned Instead use User Variable function blocks to hold the constant 5 16 PC 3000 User
39. X Val Y Val Y Val In general fairly simple Structured Text statements are adequate when programming the majority of PC3000 control applications However the PC3000 Programming Station does allow large complex pieces Structured Text to be created if required There are limits to the maximum size of an individual piece of ST but this is sufficiently generous that normally it is of no practical significance When programming PC3000 ST is used to describe a soft wiring to inter connect function blocks b the actions within SFC steps c the conditions for SFC transitions Certain restrictions apply to ST when used for these different purposes these are discussed in more detail later in this chapter Comments To aid readibility comments can be freely added to ST statements by enclosing text with the characters and Examples are This step starts up reactor 2 Modified to optimise energy usage DATA TYPES PC3000 supports a range of data types within Structured Text that cover most of the processing requirements for production process control Writing ST expressions that use these different types of data is discussed in later sections of this chapter Note throughout this user guide where an informal data type decription is given the formal IEC data type name is sometimes given in parenthesis 3 2 PC 3000 User Guide Structured Text Floating Point REAL Range Size in Bits 41038 32
40. _Val j In this example the PID loop1 is connected to analogue input while the status of input is 1 i e GO However if input develops a fault such as a sensor break the status changes to 0 i e NOGO and loop continues with the process value from input2 Value selection using IF construct A second method which is not compliant with the IEC 1131 3 standard provides value selection using the IF THEN construct to aid program readibility Use of this construct is not recommended if any part of the program is intended to be used on a fully IEC 1131 3 compliant system in the future The previous example can be expressed as 3 Structured loop1 Process_Val IF inputl Status THEN input1 Process_Val ELSE input2 Process_Val END IF The IF THEN requires a boolean expression which when 1 i e true causes the parameter on the left hand side of the assignment to be assigned the first value otherwise it is assigned the second value Like the selection function the boolean expression can be complex The alternate values can be provided by complex expressions as long as they yield a value which is the same data type as the assigned parameter Note In the Structured Text the value that is assigned when the boolean expression is 1 true comes after the value assigned when 0 false when using the selection function but this order is reversed when using the IF THEN construct PC 3000 User
41. al function blocks and Task_2 running at a 100ms scan rate for analogue function blocks and SFC execution The default tasks provide digital input to output response times throughput latency of between 15 ms and 25 ms Up to 32 PID control loops can be configured each running at a 100 ms scan rate and capable of controlling loads with primary time constants of greater than 10 seconds An alternative task configuration should be considered if a a digital input to output response less than 25 ms is required b there is a requirement to run more than 32 PID control loops c there is a requirement to run PID control loops for loads with primary time constants shorter than 10 seconds d the sequencing is required to respond more rapidly than every 100 ms e the program requires a large number of function blocks or has complex soft wiring which results in either of the tasks overrunning That is a task is unable to complete the execution of all function blocks and soft wiring within the task scan time You are advised to refer to the chapter Real Time Task Scheduler and Appendix D Example Task Configurations in the PC3000 Real Time Operating System Reference for further details on task configuration Caution An incorrect task configuration can have have a detrimental effect on the performance and integrity of the PC3000 control system TYPES OF FUNCTION BLOCK A wide range of different types of function block can be instan
42. ally inserted by the Programming Station Time of day TIME_OF_DAY Range Size in Bits Purpose 00 00 00 to 32 Used specifically for storing values 23 59 59 for the time of day i e 24 hour clock This data type is used wherever there is a need to store the time of day For example to define the time of day to start a particular job or task Values are stored to an accuracy of one second and displayed on the Programming Station in 24 hour clock format Examples are TOD 09 30 9 30 in the morning TOD 13 45 1 45 in the afternoon Si The use of the prefix TOD in ST indicates that these are TIME_OF_DAY constants The prefix is automatically inserted by the Programming Station PC 3000 User Guide 3 5 Structured Text Calendar Date DATE Range Size in Bits Purpose 01 Jan 1970 to 32 Used specifically for storing values 01 Jan 2136 for calendar dates This data type is used for storing calendar dates A wide range of dates are supported Examples are D 28 Jul 1992 D 01 Jan 1993 The use of the prefix D in ST indicates that these are date constants The prefix is automatically inserted by the Programming Station Calendar Date and Time of day DATE_AND_TIME Range Size in Bits Purpose 01 Jan 1970 32 Used specifically for storing values 00 00 00 to for calendar dates combined with 01 Jan 2136 time otday 23 59 59 This data type is used fo
43. alue of the process value i e the Process_Val parameter within a given deviation This may be useful for example when ramping a furnace temperature when the difference between the furnace setpoint temperature and actual temperature should stay within certain limits Each function block parameter is associated with a particular data type which defines the type and range of values that the parameter can store A wide range of data types are provided including REAL parameters which are used for decimal floating point values such as 12 54 0 0541 1220 1 BOOL parameters which have two states such as ON OFF TRUE FALSE UP DOWN ENUM parameters which can have a number of named or enumerated states for example the Mode parameter of the Ramp function block has states Reset Run and Hold Other data types are provided for holding counts messages and dates and times Full details on Data types are given in chapter 3 In PC3000 it is possible to create many copies of the same function block type For example you may wish to have three ramp function blocks to control three different control variables such as pump rate temperature and pressure The PC 3000 User Guide 2 7 D 3 3 d ke D d 8 Programming Concepts copies can be given unique names e g RampPump RampTemp RampPres Copies of a particular type of function block are referred to as function block Instances When a new copy of a function block is created
44. alve Process Val gt SORT IN loadSize Process_val 1 234 Structured Text PC 3000 User Guide 3 19 Structured Text FUNCTIONS PC3000 provides a wide range of standard functions which can be used in ST expressions to simplify complex operations You are advised to become familiar with the types of functions that are available remember that functions can often simplify and minimise the ST reguired to solve a particular problem A function has one or more parameters and always returns a single result of a particular data type Function categories are listed in tables 3 7 and 3 8 Category Purpose Examples Numerical Provides a wide range of ABS_REAL SQRT LOG common mathematical EXP SIN ACOS functions including trignometric and logarithmic Selection Used to select values SEL_BOOL SEL_REAL depending on a condition SEL_DATE MAX_REAL String Comprehensive set of EQUAL LEFT CONCAT functions for manipulating REPLACE JUSTIFY_RIGHT textual strings including joining strings inserting text Table 3 7 ST Function Categories Category Purpose Examples Type Conversion Conversion between data types DINT_TO_REAL REAL_TO_TIME TIME_TO_UDINT String Conversion Conversion of values of various data types to and from textual string format STRING_TO_DINT STRING_TO_REAL DINT_TO_STRING DATE_TO_US_STRING Time Arithmetic Used to add and subtract times dates
45. and Function Block Diagrams SOFTWARE OVERVIEW An application program for PC3000 consists of two main sections 1 Function Blocks and their associated wiring to provide the continuous control and logic functions and 2 Sequential Function Charts to handle sequencing g 8 D E E od ey H KE ou Figure 2 1 shows how these program sections interact with the PC3000 hardware that provides the interfaces to I O sensors and actuators and communications with external devices The figure shows a few examples of the many different types of function blocks provided with PC3000 The interfaces to I O is provided by I O function blocks such as Digital_In and Analog Out The PC3000 I OBus provides a two way information exchange between these function blocks within the PC3000 application program and the I O channels of the hardware I O modules The PC3000 Programming Station and MicroCell has access to all Function Block parameters while the PC3000 is running using the Eurotherm communications protocol Bisync This facility is referred to as default communications and is always available for diagnostic and program development purposes Communications with other external devices is provided by communications driver function blocks such as Bisync_M and Euro_Panel In figure 2 1 the Bisync_M function block is associated with a communications port linked to a number of multi dropped instruments in this case using the Eurotherm Bis
46. at other scan rates by changing the task scan times or by creating additional tasks This may be necessary for example when there is a need to increase the responsiveness of certain inputs by shortening the task scan times or alternatively a need to reduce system overheads by increasing the scan rates of certain function blocks Caution Care should be taken when modifying task configuration parameters or task assignments as this may affect the control system responsiveness or produce unexpected side effects The PC3000 Programming Station automatically assigns function blocks to the two default tasks Therefore modification to the task configuration is not normally required Refer to the PC3000 Real Time Operating System Reference Chapter Real Time Task Scheduler for details on configuring tasks PC 3000 User Guide 2 9 Programming Concepts SEQUENTIAL FUNCTION CHARTS Sequential Function Charts SFCs consist of two basic constructs steps and transitions as depicted in Figure 2 3 A Step defines a set of RN Step A actions that are performed when the control program is Step A Transition in a certain state A step remains active until a gt Step_B following Transition J becomes true A transition is defined by a test condition which must result in a true or false result for example that a particular digital input from a micro switch is on Figure 2 3 Sequential Function Charts Construct
47. configured by having both modular hardware and software it can be applied to both prototype and main stream production processes The PC3000 programming languages have been designed to be compliant with the IEC 1131 3 Programmable Controller languages standard The languages are suitable for programming the diverse range of applications for PC3000 These include furnace control for heat treatment cable manufacture water treatment and fermentation through to advanced hi tech applications such as super plastic forming presses for aircraft turbine blades and molecular beam epitaxy MBE systems In addition the languages are ideal for creating control programs on small Personal Computer based programming stations A typical production process control system must handle a range of different control problems that include Interlocks that control the conditions under which certain activities or processes can operate For example a steam valve may not be activated unless sensors indicate that steam pressure is above a certain threshold value and steam is required by the process Alarms that are triggered when certain boundary conditions are exceeded For example an alarm signal that is triggered when a temperature of a process vessel exceeds normal working temperatures Closed Loop Control for ensuring that processes are run under optimal conditions For example PID loops can be used to ensure that a furnace temperature is kept to within a
48. ction parameters VALUE SELECTION Two methods are provided to allow alternative values to be selected in ST assignments and expressions Selection functions This type of function allows one of two alternative values INO and IN1 to be selected depending on the value of a boolean BOOL input G The result is the value of INO if the value of G is 0 false otherwise the result is the value of IN1 if the value of G is 1 true Selection functions for all the PC3000 data types are provided The selection input G can take a value derived from any boolean expression PC 3000 User Guide 3 21 Structured Text SEL REAL BOOL REAL REAL REAL Figure 3 1 Selection Function Example Examples speed Val SEL_REAL G sensor Val INO 20 0 IN1 30 0 If sensor Val is true value is 30 0 otherwise the value it is 20 0 Taj G rate Val gt 100 0 INO T 5s IN1 T 2s500ms pulse is 2 5 seconds for rate greater than pulse Prog_Time SEL_TIM 100 0 otherwise pulse is 5 seconds Selection Functions are defined within the IEC 1131 3 standard and are particularly useful in soft wiring where there is a requirement to change the assigned value depending on some special condition 3 22 PC 3000 User Guide Structured Text Example loopl Process_Val SEL REAL G inputl1 Status Oo ll input2 Process_Val_ e oe ll input1l Process
49. ding into the rendezvous i e entering the double horizontal lines is active User screens User Screens can be created on the Programming Station while the PC3000 is running to view selected parameters This allows critical parameters to viewed simultaneously for diagnostic and commissioning purposes User screens can also be used to provide an operator interface for applications where a simple man machine interface is adequate E 0 Zb S a 2 oO fa Plant simulation During system commissioning it is unlikely that all plant I O is available for program testing In some cases it may be inconvenient or even dangerous to drive the physical outputs PC3000 provides facilities to test programs without being directly connected to the plant or controlled machine Most PC3000 input channels have a test mode which allows the value of the physical input to be replaced by a test value It is also possible to replace the channel status with a test status Consequently the behaviour of the program can PC 3000 User Guide 5 17 Program Development be tested by simulating different plant input values and fault conditions such as overrange sensor readings A part of the sequence program typically running as another parallel sequence can be used to provide multiple test values to the I O channels to build a plant simulation test bed that exercises the control program This can be removed when the program is fully commissioned
50. displayed on the PC3000 Programming Station when the value of the parameter is viewed Enumerated integers can be freely used together with normal integers in ST expressions Boolean BOO L Range Size in Bits Purpose Oorl 1 Gerneral purpose data type for storing boolean values i e 0 or 1 This data type is used to store boolean values such as those associated with digital inputs for switch contacts which can have two states of value 0 and 1 Normally 0 is associated with Off or False and 1 is associated with On or True The PC3000 Programming Station however allows boolean values to be given alternative sense names if required The sense names are used to aid program readibility 3 4 PC 3000 User Guide Structured Text Examples are Down 0 Up 1 In 0 Out 1 Duration TIME Range Size in Bits Purpose Up to 49 days 32 Used specifically for storing time durations such as job durations PID time constants This data type is used to store time durations accurately to the nearest millisecond Any duration for up to 49 days can be stored When viewed on the 9 Programming Station durations are displayed using the IEC format Examples 5 x are 9 CH T 2d O1h 30m 2 days 1 hour 30 minutes Li T 3s200ms 3 seconds and 200 milliseconds The use of the prefix T in ST indicates that these are constants of TIME data type The prefix is automatic
51. e main chart The first step should be defined as a start step and given the name Setup Also name the other steps Heatup Cool and Finish The Finish step should be defined as an end step 2 All three steps should be defined as single shot implying that they will only execute once when the steps are first entered 3 Enter the Structured Text for each step and transition as shown in figure 2 4 Note that the transition from Start to Heat uses the function ABS_REAL which is used to calculate the absolute value of the PID error parameter The condition for the second transition uses the AND operator to check that a the process value is greater then 56 0 and b the Heatup step has been active for longer than 30 minutes The duration of any active step is provided by the step s Time abbreviated T output parameter 2 14 PC 3000 User Guide Programming Concepts To test the program compile build and download the program into the PC3000 With the PC3000 switched into RUNNING mode the program will execute by seguencing through steps Setup to Finish setting the PID setpoint Note that on reaching the Finish step the SFC terminates with no further active steps However the function blocks for the control loop continue to execute With this simple example it is necessary to RESET the PC3000 and then switch the PC3000 back into RUNNING mode to re start the SFC It is possible to construct the SFC so that it always re starts
52. ead Note Each soft wiring ST statement is executed at the same rate and in the same task as the function block receiving the value produced by the soft wiring Care should therefore be taken to minimise the number and complexity of soft wiring statements assigned to function blocks that have a high scan rate particularly digital function blocks Soft wiring containing a large number of operations involving floating point values such as comparing Temp1 Process_val with 50 0 used in the previous program example presents a significant performance overhead With good program design the number of floating point calculations can be reduced In contrast a large number of operations involving digital parameters such as the OR of door1 Process_val and door2 Process_val used in this example can be executed without any significant overhead More guidance on good program design is given in Chapter 5 Program Development Detailed information on performance is also given in the PC3000 Real Time Operating System Reference Appendix C PC3000 User Guide 2 17 Chapter 3 STRUCTURED TEXT Edition 1 Contents OVERVIEW SG ES ERG Me Ge EE dE 3 1 Introduction to structured Text 3 1 COMMONS EE ENESTENSEEEEEES ENKE KEEN 3 2 DATA TYPES RS EE n e e deeg 3 2 WHERE TO USE STRUCTURED T NT 3 9 ASSIGNMENTS se oe ER ES ie he Ee ee PR oe WERE ee Se Gee 3 10 EXPIeSSIONS ni Ee ee AS a ei de 3 10 Complex expresSiONS ie ek Re ke ee 3 11 STATEMENTS EE
53. ects The SFCs contain actions that can modify the values of function block input parameters in response to certain events SFCs are therefore able modify the system behaviour according to well defined changes in specific process conditions such as reaching operating temperature or emptying a reactor vessel The function blocks are partitioned into tasks that execute at fixed scan rates The default task configuration which is suitable for a large number of PC3000 applications has two tasks named Task_1 and Task_2 which execute every 10 ms and 100 ms respectively Most function blocks associated with analogue I O and analogue control are run every 100 ms this includes the PID function blocks The rest i e those associated with digital signals and therefore requiring a faster system response are run every 10 ms The Sequential Function Charts SFCs by default are run in the slower 100 ms task g 8 D 3 3 d ke D d Task Name Task Scan Rate Purpose Task_2 100 ms All analogue related function blocks Most analogue I O function blocks All Sequential Function Charts Task_1 10 ms All digital related function blocks All digital I O function blocks Fast analogue I O function blocks Table 2 1 Default Task Configuration However the default task configuration can be modified if the control problem has some special requirements All function blocks including those for I O can be assigned to run
54. ed to connect function blocks Start Fo gt Step_A Step lt b Transition gt Step_B er End Figure 4 1 Basic SFC Elements S 8 5 T e K o gt A Step which is depicted as a box surrounding a step name defines a set of actions that are performed when the controlled plant or machine is in a defined state The step remains active until the condition associated with a following Transition which is depicted by a short horizontal line becomes true For example when controlling a furnace a step could establish setpoint temperatures for PID control loops and the following transition could have a condition that waits for the control loops to be stable A series of of steps and transitions are linked by lines as shown in figure 1 to form a sequence When a sequence is executed the first step in this case step Start is PC 3000 User Guide 4 1 Seguential Function Charts activated It remains active until the condition for the following transition is true i e transition a When the condition for transition a is true the following step Step_A is activated and step Start is deactivated In the same way sequence will process through all the linked steps In this example only one step is active at any time Typically a step contains actions that change the values of function block input parameters in order to modify the behaviour of t
55. ensors can be scanned more slowly Typically analogue inputs are scanned more slowly than digital inputs There may also be parts of the application required to analyse long term trends In such cases tasks can be configured to execute at much slower rates such as every 5 minutes or longer Deterministic performance Unlike many PLCs PC3000 provides tasks that have fixed scan rates For example providing certain performance considerations are followed it is possible to build a control system in which function blocks assigned to run in a 100 ms task will always execute every 100 ms Deterministic Performance is important for stable and predictable control system behaviour If too many function blocks are assigned to a task PC3000 may overrun i e the task scan time has to be extended to ensure that the task completes correctly This is regarded as an exceptional situation that requires modification of the function block task assignments Further information on using tasks is provided in the PC3000 Real Time Operating System Reference FUNCTION BLOCKS Traditionally control systems have been constructed by physically wiring together a number of discrete instruments such as temperature controllers timers displays and so on However systems of this type are costly to install and are extremely inflexible In constrast PC3000 allows control programs to be built up from soft instruments called function blocks This powerful concept
56. erpress Process_Val AND noAlarm Val PC 3000 User Guide 3 11 Structured Text STATEMENTS A section of Structured Text is composed of a number of statements An assignment is one example of a simple ST statement Conditional Statements are more complex and allow sets of ST statements to be selectively executed as described in the next section In an SFC step a variety of statements can be used to set up the values of function block input parameters as required for the particular process phase or state Example BEGIN heaterl Process_Val 123 0 heater2 Process_Val 130 0 fan Process_Val 1 ON END Note The keywords BEGIN and END are automatically added by the Programming Station when Structured Text for a step is created They indicate that the ST defines step actions Conditional statements A set of statements can be conditionally evaluated using a conditional statement structure The PC3000 Structured Text provides the IF THEN ELSIF ELSE and END_IF keywords to allow you to conditionally select statements according to certain control criteria In the simplest form IF THEN and END_IF can be used to conditionally select a set of statements Example IF switch Process Val 1 COOL zi THEN fan Process Val 1 ON fanSpeed Process_Val 230 0 END_IF The expression between the IF and THEN keywords can be either simple or complex but must result in a boolean BOOL res
57. es to be written to Function Block input parameters These values can be constants the value of other parameters or derived from other parameters using expressions Assignments are used to inter connect function blocks i e in soft wiring and to define new parameter values in SFC steps PC3000 User Guide 3 9 Structured Text Examples are loopl Setpoint 30 5 Ccountl1 Process Val 300 pulse3 Prog Time T ls heat1 Process Val loopl Output speed Process_Val rate Process_Val 20 An assignment always starts with the name of the Function Block input parameter on the left hand side followed by the symbol The value of the right hand side i e following the symbol should result in a value of the same data type as the function block input parameter The assignment an text is always terminated by a semicolon When creating soft wiring assignments the Programming Station automatically inserts the and symbols Note The Programming Station will report Error Invalid ST if an assignment is made to any function block output parameter Assignments to input output parameters are allowed When an assignment is used to inter connect or soft wire function blocks as part of the continous control strategy remember that the assignment will be evaluated continously That is at the task scan rate of the function block to which the asignment is being made Expressions A wide ran
58. f temporary soft wiring IF input Process Val High ValTHEN HighScan High Val input Process_Val END IF a HighScan Time gt T 30m Figure 4 8 Continuous Step g 2 5 T e K CH In figure 4 8 a continuous step is used to monitor the value of an analogue input over a period of 30 minutes and record the highest value reached in parameter High Val PC 3000 User Guide 4 7 Sequential Function Charts Note The actions of a continuous step are executed one further time after the step s following transition becomes true this is discussed in the next section STEP EXECUTION TIMING All the charts are scanned repetitively at the scan rate set by the task assigned to the SFC All active steps are evaluated and the associated step actions are executed according to each step s execution mode SFC executes HHH Step active LX flag Fr Transition condition Continuous step actions executed Single shot step actions executed Figure 4 9 Step Execution Timing Figure 4 9 is a timing diagram that depicts the differences between single shot and continuous step execution A step is active until a following transition becomes true it is then deactivated The step s Executing parameter remains true while the step is active also see section Step and Macro Function Blocks The actions of a single shot step are executed once when the step first becomes active In contrast the actions
59. g is ashes BEE tit EE ee 2 5 Deterministic performance ese ke 2 5 FUNCTION BLOCKS ecese 2 5 Function block example ese ee ee 2 7 VO function block eter ke eee 2 8 PRO GRAM EXECUTION PRINCIPLES 2 9 SEQUENTIAL FUNCTION CHARTS cece 2 10 SO FTWARE O VERVIEW A 2 11 PRO GRAM EXAMPLE ee ed ese kg ee es ed eie ds 2 12 Continuous Control 2 12 SCQUENCING EER OR ER OE Rd a 2 14 Digitall Le UE 2 15 SO FT WIRING PERFO RMAN CE CONSIDERATIONG 2 17 D 3 3 d ke D d PC3000 User Guide Cont i g 8 Programming Concepts OVERVIEW The following programming concepts of the PC3000 are described in this chapter 1 The design of PC3000 programming languages and how they are based on international standards 2 How complex control programs can be built by connecting soft instruments or Function Blocks together by software 3 The purpose of PC3000 Function Blocks and how they are described 4 The advantages of using PC3000 s multi tasking system that allows different parts of the control program to run at different scan rates g 8 5 How you can use Function Blocks and Sequential Function Charts SFCs to operate together when building a control program eil E E od ey H KE A Background The PC3000 is a new generation highly configurable Programmable Controller which is suitable for the automation of a wide range of industrial processes Because PC3000 can easily be
60. ge of expressions can be created using the standard ST operators so that derived values can be calculated from parameters of the various ST data types Expressions are used in the right hand side of assignments and in conditional expressions A typical simple expression involves one or two parameters or constants and an operator Examples of simple expressions 123 34 6 10000 count Process_Val loopl Setpoint NOT switch Process_Val 3 10 PC 3000 User Guide Structured Text Examples using simple expressions in assignments Add 120 0 degrees to the current soak temperature soakTemp Setpoint soakTemp Setpoint 120 0 The line rate is 2 M S plus 50 the conveyor speed lineRate Process Val 2 0 conveyor Process_Val 0 5 Valve is ON if O2 supply is OFF and H2 is ON valve Process_Val NOT 02 Process_Val AND H2 Process_Val Complex expressions In some cases it may be necessary to build up complex expressions involving many parameters and operators A complex expression is composed of many sub expressions each of which in turn may be composed of further sub expressions or simple expressions To clarify the execution order of complex expressions round brackets can be used to identify the sub expressions Examples Structured airPress Val 13 54 gasPress Val 34 32 vapPress Val 0 5 switch Process_Val AND dig3 Process_Val OR ov
61. he continuous control part of the program A step usually defines actions in Structured Text but can represent another SFC using the Macro Step concept as discussed later in this chapter The condition associated with a transition is defined using a boolean expression written in the Structured Text language see Chapter 3 Structured Text A condition can define any time related process event or boundary condition Figure 4 2 depicts an example of simple sequence and its associated step actions and transitions defined using ST this is taken from the example program discussed in Chapter 2 Setup Loop1 Setpoint 20 0 ABS_REAL Temp1 Process_ValLoop1 Setpoint lt 2 0 j Heatup Loop1 Setpoint 60 0 Temp1 Process Vab 56 0 AND Heatup Time gt T 30s l Cool Loop1 Setpoint 20 0 Temp1 Process Val 24 0 Finish Figure 4 2 Example of a Seguence with ST In Figure 4 2 assuming that the step Setup is active the Heatup step is activated when the transition condition ABS REAL emp Process Val Loopl Setpoint lt 2 0 becomes true i e the absolute value of the PID control loop error is less than 2 0 As soon a s Heatup is activated the Setup step is deactivated and its associated transition is no longer evaluated Note It is only necessary for the condition of a transition that follows an active step to be evaluated as true once in order to cause the succeeding step to be activated 4 2 PC 3000 User Guide
62. hecks each chart and ensures that the basic construction of each SFC is correct before allowing a program to be built e g that each chart must have a start step However it is possible to construct a chart that can behave incorrectly for two main reasons 1 There may be steps that can never be activated 2 Steps or sequences may unintentionally remain active This can occur when re entering a sequence especially if it involves parallel sequences that do not terminate at a rendezvous correctly PC 3000 User Guide 4 13 Sequential Function Charts Purge Pres_Chk T Cool Heat Shut_Off UnLoad Stir E Finish Figure 4 13 Unsafe SFC Construction Figure 4 13 depicts an unsafe SFC because if sequence a is selected it is possible that steps Pres Chk or Shut_off remain active when step ReStart is re activated 4 14 PC 3000 User Guide Seguential Function Charte S Init ReStart a xX Purge Convey ie L E Finish Heat Position U nLoad Figure 4 14 Unreachable rendezvous Figure 4 14 depicts another example of an unsafe chart assume that the chart has been called by a macro step The rendezvous at d may never be reached if sequence at b or the end step c are selected Because the step Position is not activated the step St
63. how the PC3000 can be programmed to solve control problems A simple program example is described that depicts many of these concepts Chapter 3 provides a detailed description of the Structured Text language with examples Chapter 4 describes how to use the PC3000 Sequential Function Charts to program all the sequencing needs of both simple and complex control systems Chapter 5 is particularly important You are advised to read Chapter 5 sections Program Design Considerations and Program Development Stages before starting a major programming project PC 3000 User Guide 1 3 Introduction TERMINOLOGY AND ABBREVIATIONS The following abbreviations are used in this user guide Actions The Structured Text statements including assignments that are evaluated when a specific step is active Assignment A Structured Text statement that produces a value that is written to a specified function block parameter Boolean Expression A Structured Text expression that produces a true or false result Chart A Sequential Function Chart is a collection of graphically connected wired steps and transitions that form one or more sequences It always has a single start step Expression A Structured Text construct that produces a value of a specific data type Function Block Instance A Function Block that has been created to be of a particular Function Block type and has a unique name
64. in parallel and do not directly interact For example handling an operator display and ramping control loop setpoints could be controlled by sequences that run in parallel PC 3000 User Guide 5 1 Program Development 8 Identify all requirements for communications with external equipment including SCADA systems other PC3000s PLCs and Eurotherm discrete instruments and drives 9 Identify key parameter values of the control system that may need to be modified when the control system is being commissioned Performance optimisation through sequencing It is important to consider all the sequencing aspects of the control program You should avoid having unnecessary soft wiring in the continuous control strategy as this may present a significant performance overhead In constrast the control strategy provided by actions within SFC steps only present a performance overhead while particular steps are active Note Unlike PLC ladder programming where sequencing and continuous control are combined PC3000 allows sequencing and continuous control to be separated This reduces the performance requirements and makes the control program easier to develop commission and maintain PROGRAM DEVELOPMENT STAGES It is recommended that a PC3000 program is developed in a number of clear stages However remember that these stages are only advisory and you are free to develop any part of the program at any time The program example given in chap
65. ions 4 2 UDINT 3 8 Unreachable rendezvous 4 15 Unsafe chart 4 15 Index 6 PC 3000 User Guide
66. ir will never be reached It is also possible for the end step Finish to be reached while other steps are still active i e steps Purge or Heat This may result in returning to the macro step in the higher level chart with steps still active d e d Note On macro charts always ensure that all parallel seguences rendezvous before reaching the end step PC3000 User Guide 4 15 Seguential Function Charts Unsafe SFC D imt Convey Position Reverse E Finish Figure 4 15a Incomplete Rendezvous 4 16 PC3000 User Guide Seguential Function Charts Safe SFC S imt J ReStart Purge Convey Heat Position Reverse Ready E E Finish Figure 4 15b Complete Rendezvous Figure 4 15a depicts an unsafe SFC and an equivalent safe SFC in figure 4 15b In the unsafe SFC the rendezvous transition before step Stir will never be evaluated because it will wait for all steps Heat Position and Reverse to be active This can never occur because steps Position and Reverse are alternatives d e d PC3000 User Guide 4 17 Chapter 5 PROGRAM DEVELOPMENT Edition 2 Contents OVERVIEW 4 ase ee ere ee ee ee De ee be ee Gee At 5 1 PRO GRAM DESIGN CONSIDERATIONS occse 5 1 Performance optimisation through sequenci
67. l loads To complete the simulation the process value Main PV from the Load1 is fed back as the process value Process_Val to the Loop PID block using soft wiring marked as feedback This results in the following execution order being created when the program is built 1 Execute soft wiring to create new value of Loop1 Process_Val using the value of Loadl Main PV from the last scan 2 Execute Loop PID control block and update Loop Output 3 Execute soft wiring to create new value for Load1l Input from Loop1 Output created in current scan 4 Execute the Load1 block and update the Main PV parameter Any ST soft wiring assignment that is marked as feedback when it is not actually part of a feedback loop will cause the Programming Station to issue a Redundant Feedback Mark error message when the program is compiled The positioning of feedback mark in soft wiring does not normally have a significant effect when constructing analogue feedback loops Especially in control situations where time constants are significantly longer than the task scan times However with digital logic care is required when positioning the feedback soft wiring as this can sometimes have a significant effect 5 8 PC 3000 User Guide Program Development CHANGING TASK CONFIGURATION For the majority of PC3000 programs the default task configuration is suitable This provides two tasks Task_1 running at a 10ms scan rate for digit
68. locks to simulate control loops OTHERS Provides a variety of miscellaneous Shift_16 Rate_Limit Function Blocks including shift Ramp Shift_Real register ramp alarm control Alarm Cntrl bistable Bistable SD Table 5 1 Function Block Type Classes Note 1 The channel input and output function blocks are created via the hardware configuration screens PC 3000 User Guide 5 11 G E 0 c S a 2 oO fa Program Development Assignment of function blocks to tasks Bistable RD Bistable SD Boolean Debounce In Digital In Table 5 2 lists the standard Function Blocks that are assigned to Task 1 by default The rest of the function blocks in the standard library are assigned to Task 2 By default Task 1 scans every 10ms Task 2 scans every 100ms Do not modify these task assignments without Digital Out understanding the performance implications Before modifying the task configuration you are Dn_Counter advised to refer to the chapter Real Time Task EI Bisync M Scheduler and Appendix D Example Task EL_Bisync_S Configurations in the PC3000 Real Time Operating System JBus_M d ie It is always possible to see which task a function block JBus_S is assigned to by viewing the function block Instance Off_Delay List menu on the Programming Station On_Delay Pulse_timer Select_Bool Shift_16 Siemens_M_S Stopwatch Toshiba_M Up_Counter Up_Dn_Count Table 5 2 Default assignment of Functio
69. n Blocks to Task_1 BUILDING A RAMP DWELL PROGRAMMER This section describes how a simple ramp dwell programmer can be constructed from standard function blocks and controlled by a few steps in a Sequential Function Chart The example provides a ramp dwell programmer that can have up to 16 segments Each segment can be either a ramp or a dwell and the number of segments in the program can be set from 1 to 16 During a ramping segment a Ramp function block is used to increment an output to a setpoint value at a prescribed rate A dwelling segment holds the current output from the Ramp function block for a prescribed duration 5 12 PC 3000 User Guide Program Development Steps in a SFC use values generated by select function blocks to set up the Ramp function block to create the ramp and dwell functions The output of the Ramp in the example parameter ramp1 Output provides the ramp dwell profiled value that can be used to drive physical outputs or PID setpoints etc For example by soft wiring a number of different PID setpoints to this parameter it is possible to construct a multi zone programmer The techniques described here can be extended to provide other features such as more segments further segment parameters etc Figure 5 3 depicts the function blocks and soft wiring required to create the ramp dwell programmer Some of the parameters that are not relevant to this example are not shown for clarity
70. n acceptable band i e within particular high and low limits while the furnace is loaded Sequencing to facilitate the initiation and termination of key phases of a process under well defined conditions For example an ingot in a heat treatment furnace PC3000 User Guide 2 1 Programming Concepts should be removed when the furnace has been at or above a prescribed temperature for a given period Long Loop Control where long term conditions are monitored and actions taken to optimise process yield For example the efficiency of a pump may gradually deteriorate due to impeller wear This can be detected by monitoring the mean power consumption of the pump over a long period of time using Statistical Process Control techniques The pump rate can then be adjusted to compensate for wear The languages adopted for PC3000 allow you to describe all of these aspects of the control program in a consistent and natural way These languages are easy to read and maintain and are in a form that can be understood by people with different levels of computer expertise IEC 1131 3 PLC STANDARD Figure 2 1 depicts the main components of a PC3000 program The International Electrotechnical Commission IEC have produced a set of standards for Programmable Controllers identified as IEC 1131 Part 3 of this standard termed IEC 1131 3 specifically addresses PLC languages and the way PLCs operate and run control programs Many of the concepts of this
71. n assigning integer values created by ST expressions to integer parameters that are not of the normal DINT data type The range of the integer value created by the ST must be within the range of the data type of the parameter to receive the value If the value is out of range an incorrect value may be assigned e g assigning the DINT value 300 to a USINT will fail because the USINT maximum value is 255 Note These additional integer data types are not used in any of the standard PC3000 function blocks or functions with the exception of the string functions LEN LEFT RIGHT MID INSERT DELETE REPLACE FIND JUSTIFY_LEFT JUSTIFY_RIGHT JUSTIFY_CENTRE which have some USINT integer parameters Descriptions of functions and function blocks in the PC3000 Functions and Function Blocks References include the data type of each parameter IO Address The I O Address data type is used to store the physical position of an I O channel function block This is a special PC3000 data type which is not defined by the IEC standard It is not possible to manipulate parameters of this type in ST since this would serve no practical purpose Note that I O channel function blocks can be assigned to different physical addresses by using facilities provided by the Programming Station on the Hardware Definition screen VO Address parameters are discussed in Chapter 2 PC3000 Programming Concepts 3 8 PC 3000 User Guide Structured Text Data Type Con
72. nction blocks to handle each control loop 2 Configure the operating mode for each PID e g dual channel heat cool valve positioner auto tune 3 Use Structured Text soft wiring to connect the process value of analogue output channels or of time proportional digital output channels and the output of PID function blocks sed E E 0 Input channel function blocks O uput channel function blocks D Do PID Analog_Out Ke 9 D 4 loopt heat ou 3 Actuators D Sensors loop1 Process_Val zone1 Process Val heat1 Process_Val loop1 Output PC 3000 User Guide 5 3 Program Development 4 Also soft wire the process value of each PID function block to the appropriate analogue input process value 5 Create other function blocks and use soft wiring to create other aspects of the continuous analogue control Stage 3 Configure the continuous digital control ae Digital In Digital Out d Switch N valvel Sensors valve1 Process_Val switch1 Process_Val AND switch2 Process Val XH Actuators The main actions are 1 Use soft wiring to create the digital continuous control strategy i e the digital logic 2 Try to avoid ST that involves numerous floating point REAL expressions or functions in soft wiring to digital function blocks This will lessen the digital soft wiring performance overhead which normally runs in the task that scans at the highest frequency
73. nd step Table 4 1 Step Attributes Macro Specifies that the step activates a non abortable macro chart The transition s that follows a macro step will only be tested when the associated macro chart has reached the end step Abortable Specifies that the step activates an abortable macro chart The Macro transition s that follow an abortable macro step are tested e continuously while the macro chart is active If one of the S transitions have a condition that is true the entire macro chart is e p deactivated D se One shot Specifies that the actions of the step are only executed once when E default the step is first activated 8 Continuous Specifies that the actions of the step are continually executed while the step is active The actions are executed one further time after the step has been deactivated Table 4 2 Step Attributes When setting step attributes a step may have one attribute from table 4 1 and one attribute from table 4 2 Examples are Start One shot Normal Continuous Normal Abortable Macro End Macro PC 3000 User Guide 4 11 Seguential Function Charts STEP AND MACRO FUNCTION BLOCKS Each step macro and abortable macro step is represented in the PC3000 system as a function block This allows parameters that give the state and step duration to be used in ST i e in soft wiring step actions and transition conditions BOOL Executing
74. ng 5 2 PRO GRAM DEVELOPMENT STAGES oos 5 2 Select and configure the UO channels es 5 2 Configure the continuous analogue control 5 3 Configure the continuous digital control ese 5 4 Create sequencing control strategy 5 5 Create transitions and step actions cece 5 6 DESIGN OF THE MAIN SFC AAA 5 6 FEEDBACK IN FUNCTION BLOCK SOFT WIRING 5 7 CHANGING TASK CONFIGURATION ee ee 5 9 TYPES OF FUNCTION BUODCK ese esse ee ee ee ee ee ee ee 5 9 Assignment of function blocks to tasks ee se 5 12 BUILDING A RAMP DWELL PRO GRAMMER 5 12 A4 PROGRAMMING ert 5 16 PA COMMISSIONING PROGRAMS ee 5 17 E Sequence held Up ceecee 5 17 E g User SC NS ee ee ee ee ee ee 5 17 a Plant simulation s e 5 17 D utputtesting n a 5 18 PC3000 User Guide Cont i Program Development OVERVIEW This Chapter describes the following aspects of program development for the PC3000 e How to structure a PC3000 program by analysing the different requirements of a control system Good programming practice e How to use the PC3000 control system efficiently e How to develop programs that are easy to read and maintain e How to commission PC3000 programs e How to use function blocks together with SFC to solve control problems PROGRAM DESIGN CONSIDERATIONS A PC3000 program like any piece of software needs to be carefully designed to ensure that the program functions correctly and makes best u
75. nly one of two parameters are on or true but not both It produces a false result if both parameters are true 5 Note 2 The NOT operator is used with a single boolean value or 9 g expression to negate the boolean sense This operator can be used g D after and inconjunction with other boolean operators see earlier 5 k boolean operator examples Li These operators are used to create expressions involving boolean BOOL data types Although they are primarily used with digital inputs and outputs they are also useful when used with comparison operators to create expressions that describe complex conditions Examples vent Process Val switchl Process Val AND heatFlag Val OR overPres Val alarm Val NOT pressure Val AND NOT airValve Process_Val AND zonel Process_Val gt 500 0 Example outl Process_Val inl Val XOR in2 Val AND NOT in3 Val OR in3 Val outl1 Process Val is set to 1 ON when only one of the parameters inl Val in2 Val or in3 Val are 1 ON Operator precedence Operators have different precedence to ensure that where there are complex expressions involving many operators the order of evaluation is consistent PC3000 User Guide 3 17 Structured Text Example total Val a Val 10 b Val 20 When this expression is evaluated a Val is multiplied by 10 b Val is multiplied by 20 and the two values are added together In other words the multiplication occurs
76. nment 2 9 creating SFC 4 4 hardware definition 3 8 program build 2 17 selecting hardware modules 5 3 time constants 3 6 Programming Station 1 1 Programming Station 3 5 21 Programming Station 5 17 Ramp Function block 2 7 Ramps 1 3 Recipe management 2 7 Rendevous transition 4 5 Rendezvous 4 13 Response times 5 9 Rules SFC programming 4 12 Structured text 3 24 using steps 4 13 using transitions 4 13 Running mode 2 15 17 SCADA 1 2 SCADA systems 5 2 Scaling 5 3 Scan rate 2 17 Scan rates execution 2 5 Sense names 5 16 Sequence Index 4 PC3000 User Guide Index held up 5 17 Seguences parallel 4 4 Sequencial Function charts 2 8 Sequencing 2 1 14 Sequential Function chart 2 2 Sequential Function charts IEC 1131 3 4 1 step 2 10 transition 2 10 Sequential Function charts 2 1 Sequential Function charts 4 1 SFC 1 4 SFC 2 2 SFC 4 1 SFC structure 5 16 Simulation load 5 8 SINT 3 8 soft instruments 2 1 5 Soft wiring concept 2 6 continuous control 2 12 continuous step 4 7 feedback 5 7 multi zone 5 13 performance 2 17 ST 3 2 ST 4 12 Soft wiring 2 14 Soft wiring 3 9 10 21 22 Soft wiring 4 1 Soft wiring 5 2 3 16 programmer 5 13 Software Overview 2 11 ST 1 4 ST 2 2 ST 3 1 2 ST syntax 3 operators 3 24 Statement 1 4 Statements conditional 3 12 13 Statements 3 9 12 Statistical process control 2 2 7 Step abortable macr
77. o 4 6 abortable macro 5 6 actions 3 9 actions 4 7 actions 5 6 attributes 4 10 11 continuous 4 7 8 11 13 control program 4 1 deactivating 4 6 End 4 11 13 execution timing 4 8 finish 2 15 macro 4 2 11 macro 5 11 one shot 4 11 rules 4 13 sequential function charts 2 10 single shot 2 15 single shot 4 6 7 8 Step 1 4 Structured Text tules 3 24 Structured Text 2 2 10 Structured Text 3 2 Subtraction 3 15 Supervisory systems 1 2 Supervisory systems 2 7 Systems multi tasking 2 1 Task scan time 5 15 Tasks assignments 5 12 PC 3000 User Guide Index 5 Index configuration 5 9 SFC 4 17 default 5 9 SFC construction 4 14 incorrect configuration 5 9 Unsafe SFC construction 4 13 Real Time Scheduler 5 9 Tasks 2 5 Unsigned Integer double 3 8 Test short 3 8 mode 5 17 User screens 5 17 output 5 17 physical wiring 5 17 USINT 3 8 status 5 17 Value selection 3 23 value 5 17 Variables 3 1 Test_Enable parameter 2 16 Ta S VP 5 9 D extual messages 3 VP_AUTO 5 9 Textual strings STRING 3 7 THEN 3 12 Time of day TIME OF DAY 3 5 Time parameter 2 15 Time proportional outputs 5 1 Time stamps 3 6 Timers 1 3 Top down design 5 6 Transition condition 1 4 rendevous 4 5 rendezvous 5 17 terminology 1 4 Transition 2 10 Transition 4 13 Transitions alternative 4 3 conditions 3 9 conditions 5 6 create 5 6 Transitions 3 2 Transit
78. oad Eh j Pump Al Process cl Anneal Fro F Unload Depress Figure 4 6 Using an Abortable Macro Step In figure 4 6 Process is an abortable macro step When Process is activated the macro chart is entered from the start step Pump The condition for the transition from Process is continually evaluated while the macro chart sequence is active The dotted line depicts the case where the step Anneal is aborted because the transition from Process has become true The sequence in the upper level chart continues from the step Unload that follows Process It is possible for an end step to be an abortable macro In which case it is the transition s of the macro step in the next higher level chart that is tested and when true aborts the lower level chart Deactivating steps When steps are deactivated as a result of aborting a macro chart actions of a step are always executed completely That is it is never possible for a step to be deactivated while actions are being executed A single shot step is deactivated after executing all the actions once 4 6 PC3000 User Guide Seguential Function Charts A continuous step is deactivated after the actions have been executed at least once The actions are executed one further time after the step has been deactivated During this last execution of the continuous step the step s Executing parameter is false This is described in more detail in the follo
79. ocks associated with parameters in soft wiring assignments always execute ahead of the function block to receive the soft wiring value There are situations as depicted in figure 5 2 where it is necessary to soft wire function blocks together to form a feedback loop In such cases the function block execution order can be modified by identifying one of the soft wiring expressions forming the loop as being the feedback soft wiring Programming Station Wiring Editor provides a Mark Feedback function key that allows any ST wiring assignment to be marked by inserting the text feedback as a comment When the program is compiled and built this causes the function block being assigned the feedback soft wiring to be executed before the function blocks referenced in the right hand side of the soft wiring assignment Note A function block receiving a value from a Soft wiring assignment marked as feedback always executes before function blocks whose parameters are referenced in the right hand side of the assignment PJ c O 2 S D a PC3000 User Guide 5 7 Program Development Load1 Input Looo1 Output 3 s PID Loop X PID Load Process Val Output Main DV l i Loop1 Process_Val Load1 Main_PV Feedoack Figure 5 2 Feedback in Function Block Soft wiring Figure 5 2 depicts an example where a PID control loop Loop1 is connected to a PID_Load Load1 that simulates various plant contro
80. odulo 3 15 Modulos 3 16 Multi tasking 2 5 Multiplication 3 15 Offsets 5 3 Operator 19 Boolean AND 3 17 Exclusive OR 3 17 Inverse 3 17 NOT 3 17 OR 3 17 XOR 3 17 comparison equal 3 16 greater than 3 16 greater than or equal 3 16 Less than 3 16 less than or equal to 3 16 not equal 3 16 complement 3 19 divide 3 19 floating point 3 17 interface 5 17 modulo 3 19 multiply 3 19 negation 3 19 precedence 3 18 stations 2 7 Operator 3 1 10 Operators 3 15 PC3000 User Guide Index 3 Index Parameter Executing 4 12 Finished 4 12 Time 4 12 executing 4 9 PC3000 Communications overview 1 2 languages 1 1 programming 1 1 PC3000 mode 2 15 PC3000 Programming Station 2 14 PC3000 reference functions 1 2 functions block 1 2 hardware 1 2 manuals 1 2 real time operating system 1 2 Performance 2 5 Performance 5 1 9 Performance implications 5 12 PID control loops 5 9 PID 1 2 3 4 PID 2 1 7 PID 3 23 PID 5 9 PID control loop example 2 12 PID control loop 2 12 PID function block configuration parameters 2 14 PID function blocks 5 3 PID AUTO 5 9 PLC 2 5 PLC 5 2 PLC ladder programming 5 2 Program development 5 1 practice 5 1 readability 5 16 Program building 2 15 Programmable Controller 2 1 Programmable controllers process 1 1 Programmable controllers 1 2 Programmer ramp dwell 5 15 Programming Station assig
81. of the digital input function block and the Temp function block Soft wiring can either provide direct point to point links as used to construct the control loop or can involve complex expressions with both digital and analogue function block parameters PC 3000 User Guide 2 15 Programming Concepts 1 03 01 1 03 02 Task 10 ms N 50 0 Templ Process val Digital In Door1 Process Val TO Address Digital Out Alarm 1 05 01 TO Address Process Val Soft wiring Digital_In Alarm Process_val Doorl Process_Val OR Door2 Door2 Process_Val AND Process_Val TO Address Templ Process Val 50 0 Figure 2 5 Digital Logic Example To create these function blocks and soft wiring the following actions are reguired 1 Create two UO digital input channel function blocks named Door and Door2 using a hardware module such as DI14 CON There are no channel configuration parameters to set up Ensure that the Test Enable parameter for each block is Off ie the default value 2 Create a digital output channel function block named Alarm using a hardware module such as DO12_RLY Ensure that the Test Enable parameter is Off i e the default value 3 Select the Alarm Process Val parameter and attach the soft wiring Structured Text statement as shown in figure 2 5 The digital function blocks are assigned to Task 1 which runs every 10 ms The soft wiring connected to the process value of the ou
82. point 5 Du heat1 Output Type Both simple and complex expressions for mathematical calculations can be clearly expressed e g FlowRate Val FanSpeed Process Val 3 5 Conditional expressions i e for values that are derived from tests of some form are well supported For example to deal with requirements such as The motor speed is 200 r p m when the casting is less than 5 Metres from the tool head otherwise the speed is 20 r p m can be expressed as IF Position Val lt 5 0 THEN Motor Process_Val 200 ELSE Motor Process_Val 20 0 END_IF e A wide range of different types of data can be used including floating point and digital values times time of day and dates There is also provision for handling textual messages Expressions involving different types of data are possible e g gas Process_Val Zonel Process_Val gt 310 4 e A wide range of range of standard built in operators are provided such as gt lt AND OR NOT PC 3000 User Guide 3 1 Structured Text The language has built in safe guards to prevent illogical operations between different types of data For example it is not possible use mathematical operations with digital input values or logical operators such as AND with analogue values e Functions can be used to ease otherwise complex program expressions eg position Val SORT X Val X Val Y Val Y Val position Val SORT X Val
83. r storing calendar dates along with time of day and is typically used to store time stamps for key events such as when jobs start when alarms are raised when operator shifts are changed etc Examples are DT 02 Sep 1992 20 30 00 DT 25 Jan 1991 23 00 30 The use of the prefix DT in ST indicates that these are date DATE AND TIME constants The prefix is automatically inserted by the Programming Station 3 6 PC 3000 User Guide Structured Text Textual strings STRING Range Size Purpose Each character can The length of a General purpose data type used for hold any character textual string is storing textual information consisting from the ASCII variable see of a string of characters code set Non description ASCII codes from hexadecimal values 80 to FF are also supported This data type is used for holding textual information such as operator messages printer report messages communication addresses batch descriptions etc The length of the string i e the maximum number of letters and digits characters that can be stored depends on usage For example the String User Variable function block can store textual strings of up to 80 characters whereas the Long_String User Variable function block can 9 be used for strings up to 255 characters ek v For further information on User Variable function blocks refer to the PC3000 g eg Function Block Reference b Du Examples of textual strings
84. re ke ee ke ee ke 4 6 EXECUTION OF STEP ACTION 4 7 Single shot Step AAA 4 7 CONTINUOUS SEED ooo etter teeter ke ee 4 7 STEP EXECUTION TIMING ee ees ee ee ee ee ee ee ke 4 8 Timing actions within continuous Steps seene 4 9 SFC AND FUNCTION BLOCK INTERACTION nce 4 10 STEP ATTRIBUTES ese ee ee ee ee ee ee ee ek ke ee ee ek ee ee 4 11 STEP AND MACRO FUNCTION BLOCKS eee 4 12 SFC PRO GRAMMING BULES ese ee ee ee ek ee ee ee 4 12 Rules for using Charts 4 12 Rules for USING StEpS eccerre 4 13 Rules for using transitions 4 13 UNSAFE SFC DESIGN ese ee ee ee ee aeae ee aasi 4 13 PC3000 User Guide Cont i Seq Function Charts Seguential Function Charte OVERVIEW This Chapter describes the following e The reasons for using Sequential Function Charts SFCs e The main SFC concepts e Using Structured Text to define SFC steps and transitions e The relationship between SFC execution and the execution of function blocks for continuous control e Safe and unsafe SFC design Introduction to sequential function charts Sequential Function Chart abbreviated SFC is a graphical programming language formalised by the IEC 1131 3 standard for describing the sequential aspects of a control program in terms of discrete steps and transitions A sequence is built up by graphically linking two basic program elements steps and transitions as shown in figure 4 1 The graphical links are analogous to the Soft wiring us
85. s In Figure 2 3 if Step_A is active then Step_B will become active and Step_A inactive when the condition for the Transition from Step_A to Step_B becomes true When the SFCs are evaluated normally by default every 100 ms only the conditions of transitions from active steps are tested In a well designed program it is generally found that only a small number of steps are actually active at any time As a consequence PC3000 is able to execute complex programs having SFCs with a large number of steps and transitions without any significant performance overhead Actions within steps can be defined in Structured Text ST or in terms of further SFCs Examples of ST statements to define actions within steps are loop1l Setpoint 400 0 tempRamp Mode 1 Run vacpump Process Val vacpump Process_Val B250 y Each Transition is defined by a condition expressed in Structured Text such as pumpswt Process_Val 1 On AND O2valve Process_Val 1 Open zi 2 10 PC3000 User Guide Programming Concepts In this example two digital inputs pumpswt and O2valve provide the states of two digital process variables So the transition condition can be read as pump switch is on and oxygen valve is open For further details refer to Chapter 3 Structured Text and Chapter 4 SFC Programming Note On the Microcell Programming Station alternative graphical programming methods are provided including Spreadsheets
86. s include PC3000 real time operating system reference provides a detailed description of the PC3000 real time system and related topics including multi tasking performance memory lay out and fault detection PC3000 hardware reference provides detailed information on all the PC3000 hardware modules including calibration wiring and physical configuration details PC3000 functions reference describes all the functions that can be called within the Structured Text ST language 1 2 PC 3000 User Guide Introduction PC3000 function block reference describes the numerous function blocks available to be incorporated into your control program for PID control Ramps Counters Filters Timers etc Note as it is the policy of Eurotherm Controls to continually refine and provide additional product information the list and description of manuals provided for your system may differ slightly from those described ABOUT THIS GUIDE You are advised read this guide before developing a PC3000 control program PC3000 performance can be optimised and the integrity of the program ensured if a few simple principles are followed This guide is written to supplement the PC3000 User Guide Book 1 Programmimg It is envisaged that you may need to reference both user guides when developing programs for the first time Chapter 2 provides an overview of the PC3000 languages and concepts and is useful if you wish to quickly understand
87. se of the PC3000 resources and performance If the program is being used to control a production process it is also important that the program is easy to read and understood by commissioning and maintenance engineers Although PC3000 is a flexible control system which allows programs to be built up piecemeal it is recommended that all the aspects of the control system application are understood and considered before starting program development It is recommended that the following procedures are adhered to 1 Produce a complete inventory of all inputs and outputs required by the system It is recommended that some extra inputs and outputs are added for contingencies and for future enhancements 2 Analyse all the analogue inputs and outputs and identify those associated with PID control loops Identify any digital outputs to be used for time proportional outputs 3 Identify the response times range and accuracy of all analogue inputs and outputs 4 Identify the response times required for digital inputs and outputs E 0 Zb S a 2 oO fa 5 Identify aspects of the control strategy that are always applicable and are therefore part of the continuous control strategy e g PID control loops interlocks alarm monitoring 6 Identify the main sequential control phases process initialisation calibration shut down standby are examples of clearly separate control phases 7 Identify control phases that can operate
88. standard are used both in PC3000 and also in other Eurotherm Controls products including the Production Orchestrator cell controller The following languages are available for programming the PC3000 Structured Text or ST a high level language which can be used to express complex analogue and digital expressions The language includes support for complex arithmetic operations calculations involving times and dates and conditional expressions using constructs such as IF THEN and ELSE There is also a comprehensive library that provides functions such as SQRT SINO MAX Sequential Function Chart or SFC a graphical language which provides a diagramatic representation of sequences shown as a series of linked steps and transitions SFC is based on the now well accepted Grafcet standard but with some additional features It is provides a highly visible method for defining and during operation for analysing the behaviour of the control system by showing the active states of the system in the context of all the possible alternative and parallel sequences Function Block Diagram or FBD a graphical language which allows program elements called Function Blocks to be interconnected by simply drawing wires on the screen i e in a form analogous to designing a circuit diagram using a CAD system 2 2 PC 3000 User Guide Programming Concepis SEGUENTIAL FUNCTION CHARTS ae 0 Reset ES SEQ3 COUNT CHECK ee PID Reset O
89. ter 2 follows these guidelines The stages recommended to develop a PC3000 program using the PC3000 Programming Station are summarised as follows Stage 1 Select and configure the I O channels Input channel function blocks Output channel function blocks Analog_In zone1 Sensors Actuators Digital In Digital Out ME switch1 valvel 5 2 PC3000 User Guide Program Development The main actions reguired are 1 Using the PC3000 Programming Station select the hardware modules reguired based on the I O inventory If several racks are required the I O throughput can be optimized by ensuring that digital inputs are in separate racks to digital outputs Also where possible avoid having digital and analogue modules in the same rack 2 Assign names to all I O channels Use names that are meaningful and not arbitary Ideally use names that appear on wiring or control diagrams 3 Set up the channel ranges offsets and scaling In some cases this may be left until the system is being commissioned 4 Remember that specialist modules such as the ICM and AIO8 can only be positioned in the first 5 slots in the first rack So leave these slots free if any of these modules are to be added later Stage 2 Configure the continuous analogue control Input channel function blocks O utput channel function blocks PID Xx d loop1 Ne Actuators Sensors The main actions reguired are 1 Create PID fu
90. that configure the sensor type and scale the input value to handle a wide range of input sensor types including most types of thermocouple The input sensor value is provided by the function block s Process_Val output parameter in process units such as degrees C millibars etc Note that this function block also provides a test facility to override the current plant input value with a test value Each I O function block is associated with a particular hardware I O channel defined by an input parameter called IO Address This defines the I O channel s physical location by rack number module number and channel For example an I O channel function block for the second channel of a hardware module in position 3 of rack 1 has an I O address 1 03 02 VO addresses are automatically given by the PC3000 Programming Station when a channel is assigned It is not possible to directly change the value of the I O address parameter but the I O channel function block can be moved to a different hardware module For further information on the Ramp and Analog In function blocks refer to the PC3000 Function Block Reference 2 8 PC 3000 User Guide Programming Concepts PROGRAM EXECUTION PRINCIPLES The PC3000 user program for a particular control application consists of a number of inter connected function blocks to provide the continuous control aspects of the system and one or more Sequential Function Charts SFCs to define the sequential asp
91. tiated and inter connected to solve both simple and complex control problems In many cases this allows completely new and novel control strategies to be developed E 0 Zb S a 2 oO fa For a full description of the standard function blocks provided by the Programming Station refer to the PC3000 Function Block Reference handbook The function blocks types are organised into different classes to ease selection as shown in the following table PC 3000 User Guide 5 9 Program Development Class Purpose Examples SYSTEM Provides Function Blocks that PcsSTATE Task interface with the PC3000 Real RT Clock Time Operating System including the Real Time Clock and the task management COMMS Provides communications driver EI_Bisync_M Function Blocks for protocols EI_Bisync_S including JBus EI Bisync and JBus M JBus S Euro Panel Euro Panel MODULES Function Blocks to support PPM PIM2 intelligent hardware modules INPUTS Function Blocks that represent input Digital In Analog In channels Notel OUTPUTS Function Blocks that represent Digital_Out output channels Note Analog Out 1 CONTROL Control Loop Function Blocks PID VP PID_Auto including PID and Valve Positioner VP_Auto and versions with auto tuning TIMERS Provides Function Blocks for Pulse_Timer various timing purposes including On_Delay Off_Delay pulse generation delay timing and Stopwatch stopwatch
92. tput function block Alarm is also evaluated every 10 ms i e the same as the Alarm function block The example program is now complete and can be compiled built and downloaded into the PC3000 The control loop and alarm digital logic are 2 16 PC 3000 User Guide Programming Concepts executed continously while PC3000 is in RUNNING mode The seguencing will proceed through the four steps starting from Setup Table 2 2 depicts the execution order that is automatically created by the Programming Station to run the program In most cases detailed knowledge of the execution order is not reguired Every 10 milliseconds Read the hardware digital input channels Doorl and Door2 Execute the digital I O channel function blocks and the alarm digital logic soft wiring Write the Alarm output value to the digital hardware channel Every 100 milliseconds Read the hardware analogue input channel Temp1 g 8 D 3 3 d ke D d Execute function blocks Temp1 Loop1 and Heat1 and the soft wiring forming the control loop Execute active SFC steps and evaluate transition conditions following active steps Write out the output value to the analogue hardware channel Table 2 2 Example Program Execution O rder SOFT WIRING PERFORMANCE CONSIDERATIONS When designing large PC3000 programs it is important to appreciate that a large number of soft wiring statements can present a significant performance overh
93. uctured to answer specific basic questions Book 1 PC3000 programming How do you use PC3000 Book 1 will tell you how to use all the facilities of the programming station to develop and commission your control programs Book 2 PC3000 languages What facilities does PC3000 provide This user guide introduces the programming languages and concepts used by PC3000 It also provides some simple examples of the languages PC 3000 User Guide 1 1 Introduction Book 3 PC3000 in application Why are certain facilities provided and how can they be used This book contains a number of overviews on specific topics including PC 3000 Communications overview introduces facilities and special function blocks which enable PC3000 to exchange control information and real time data with other PC3000s and other proprietary equipment such as Programmable Controllers SCADA and Supervisory systems PC 3000 Control overview describes some of the standard methods and techniques used for the control of processes using the PC3000 built in and user programmable function blocks specically those concerned with PID PC3000 REFERENCES In addition to the user guides a number of reference manuals are provided to give detailed information on a wide range of topics These manuals are not intended to be read cover to cover but are structured so that specific information can be located quickly The PC3000 Reference manual
94. ult i e the expression must generate a value that can only be True 1 or False 0 This is known as a boolean expression In the example the assignments to fan Process_Val and fanSpeed Process_Val only occur when switch Process_Val has the value 1 otherwise the assignments are ignored All the ST between the IF and the END_IF is known as a conditional IF statement and like other statements it must be terminated with semicolon H 3 12 PC3000 User Guide Structured Text Using the ELSE keyword alternative statements can be evaluated Example IF switch Process Val THEN gasFlow Process Val 100 0 almEnable Val 1 ON ELSE gasFlow Process_Val 30 0 almEnable Val 0 OFF report Val STANDBY END_IF In this example the assignments to gasFlow Process_Val almEnable Val and report Val are only evaluated if the switch Process_Val is off Because switch Process_Val produces a boolean value it can be used as the conditional expression in the IF THEN construct The ELSIF THEN construct can be used to select one or more further sets of alternative statements 3 Structured Example IF count 0 THEN speed Process_Val 20 0 doorl Process Val 0 SHUT ELSIF count lt 10 THEN speed Process_Val 40 0 door2 Process Val 0 SHUT ELSE speed Process_Val 60 0 door3 Process Val 0 SHUT
95. utput PID Process Val Se PULSE1 AMP2 PID Output 0 0 a Manual PULSE S 3 2 JNA sy AAA FUNCTION BLOCKS Concepts E LI DW DW Ai Programming EuroPanel Programming Station has access to all data on line Digital In PV DY _ gh A de AC EE Digital In Digital In Digital Out PY PV PV Ki Y OO PC3000 User Guide 2 3 4 Programming Concepts Note FBD programming is only provided by the Microcell Programming Station Multi tasking In accordance with IEC 1131 3 PC3000 allows the control program to be organised into tasks that run at different execution rates Normally PC3000 has two tasks that run every 10ms and 100ms but extra tasks can be created or task execution rates can be modified to suit the particular process reguirements A task is a part of a program that is executed periodically Many PLCs have a very simple strategy where all the PLC program normally ladder logic expressions are scanned i e executed at a fixed scan rate However with PC3000 a program can use processing resources more efficiently if different parts of the program execute at different scan rates as dictated by the responsiveness of the associated plant g 8 D E E re ey H KE ou For example some digital inputs dealing with fast mechanical interlocks may need to be scanned very rapidly other digital inputs concerned with say over temperature s
96. version A wide range of functions are provided to convert between data types refer to the PC3000 Functions Reference Chapter Type Conversion Functions for the full list For example a count held as an integer may be reguired in an expression to calculate the value of an analogue output In this case the function DINT_TO_REAL can be used to convert the integer value into a floating point REAL value i e height Process_val DINT_TO_REAL count 100 5 WHERE TO USE STRUCTURED TEXT Structured Text can be used for three different purposes in a PC3000 program but in each case the basic structure of the language is the same 9 5 Usage Purpose Language Constructs F Soft wiring Inter connection of Function Assignments F Blocks Expressions a Step Actions Assigning new values to Assignments Function Block Parameters Expressions Statements Conditional Statements Transition Defining a condition that Expressions conditions when true causes a new step or steps to be active Table 3 2 Use of Structured Text Structured Text provides a few simple easy to learn constructs Assignments Statements Expressions and Conditional Statements which when used together result in a flexible and expressive language In order to produce efficient PC3000 programs you are advised to become familiar with the following language constructs ASSIGNMENTS Structured Text assignments allow new valu
97. vision Floating point REAL Integer DINT Note 2 Modulo MOD Integer DINT Note 3 Table 3 3 Structured Text Arithmetic O perators Note 1 The symbol can also be used for negation i e to convert a value to the opposite sign 3 14 PC 3000 User Guide Structured Text For example loop Setpoint SPlow Val Note 2 The division operator can be used with two integer data type parameters or constants The result is always integer and any fractional part of the result is discarded For example V2 fe This will yield 2 as the integer result Note 3 The modulus operator produces the remainder of an integer division It can be only be used with integer data types and is typically used to count to a certain modulus Examples 12 MOD 4 Result is 0 14 MOD 4 Result is 2 4 MOD 3 Result is 1 gearPos Val gearPos Val pulses Val MOD 7 Text The value of gearPos Val is always between 0 and 6 for any value of pulses Val Structured PC 3000 User Guide 3 15 Structured Text Comparison operators Operation Symbol Data Types Greater than gt Floating point REAL Integer DINT All time and date data types Less than lt Floating point REAL Integer DINT All time and date data types Equal Floating point REAL Note 1 Integer DINT All time and date data types Not equal lt gt Floating point REAL Note
98. wing text EXECUTION OF STEP ACTIONS The actions within any step that is described in ST can be executed in two modes i e single shot or continuous Single shot step This is the normal default execution mode where all the actions within the step are executed once when the step is first activated Heatup Loop1 Setpoint 60 0 Loop2 Setpoint 70 0 Temp1 Process_Val gt 56 0 AND Heatup Time gt T 30s Figure 4 7 Single Shot Step Figure 4 7 depicts a single shot step Heatup The assignments to Loop1 Setpoint and Loop2 Setpoint only occur when the step is first activated The transition condition waits for the step to be active for at least 30 seconds However although the step remains active the assignments are only made at the beginning and have no effect for the rest of this time This execution mode is suitable for the majority of steps where there is a requirement to simply set up function block parameters for a particular process state or operation Note This mode is equivalent to the Action Qualifier Pulse defined in the IEC 1131 3 standard Continuous step This execution mode which can be set by the continuous step attribute causes the step actions to be repetitively executed while the step is active This may be required where for example there is a need to monitor input values for a period of time or continuously modify output values In effect a continuous step behaves as a piece o
99. ync protocol The figure also shows an operator panel connected using the EuroPanel function block A wide range Function Blocks for other protocols such as JBus Modbus are also provided This allows a large number of different types communicating devices to be connected to PC3000 Refer to the PC3000 Communications Overview document for further information on communicating with external devices PC 3000 User Guide 2 11 Programming Concepts PROGRAM EXAMPLE Figure 2 4 depicts a simple program example that demonstrates many the PC3000 programming concepts The program uses a single PID control loop to drive a heat process and changes the setpoint for the control loop by a small sequence program This program is used to introduce the PC3000 programming techniques and is therefore intentionally simplistic but it will function Continuous Control The single channel control loop is constructed by soft wiring an analogue input channel function block Temp1 to a PID block Loop1 which in turn then provides an output signal to an analogue output channel function block Heat1 The configuration parameters which are required to customise the input and output channel blocks to match the sensor and actuator characteristics and the PID tuning parameters are not shown in figure 2 4 to aid clarity To construct the continous control part of the program the main actions are 1 Allocate hardware modules and channels for the analogue

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