DRM135 DRM135, 3-Phase BLDC Sensorless Control with MQX
Contents
1. 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 34 Freescale Semiconductor Inc Chapter 6 Software Design 6 1 Introduction This section describes the design of the drive s software blocks The software description comprises these topics e Application software main processes e Processes flow charts e Free MASTER software e Software setting overview and application parameters A basic data flow diagram and software interconnection are shown in Figure 6 1 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 35 Introduction Phase A B C voltage Buttons API FreeMASTER Ethernet Speed Command speed_req Scaling amp Speed Ramp Flex Timer 1 speed measure speed_measured speed_scaled Speed PI Controller Commutation amp PVVM Generation PTA PTC PTD Output Gate Signals Figure 6 1 Data flow diagram 6 1 1 Application software main processes The PK60N512VMD100 MCU runs the main control algorithm According to the user interface and feedback signals it generates 3 phase PWM output signals for a three phase inverter The whole application runs on interrupts for ease of use under MQX In the main routine there is only initialization of the microcontroller and an endless loop with a FreeMASTER poll function to control the application When the required speed is oth2. Increase speed 100rpm 2500 Decrease speed 100rpm Deceleration ramp setting Automatic demo test sequence 4 m http www freescale com La Internet Protected Mode Off fq gt Sion Figure 7 2 Web page for application control For more information about the web server setting and application configuration see BLDCSLK60UG which is available at http www freescale com 7 4 Integration of the motor control driver into other applications Both versions of the motor control driver can be part of other applications The API is defined by the following six functions 1 void Set_speed int motor_number signed short speed_input First parameter is the number of the motor which receives the command This demo has only one motor so enter 1 Second parameter is the input speed in signed short format The input value is in rpm Return void 2 unsigned char Get_status void Return Status of the application 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 57 Integration of the motor control driver into other applications 0 IDLE 1 STOP 2 RUNNING 3 ALIGNMENT 6 EMERGENCY_STOP 7 UNDER_VOLTAGE_FAULT 8 OVER_VOLTAGE_FAULT 9 OVER_CURRENT_FAULT 3 signed short Get_speed int motor_number First parameter is the number of the motor which receives the command This demo has only one motor so enter
3. Freescale Semiconductor Inc 2005 3 Phase BLDC Motor Sensorless Control using MC9SOSMP 16 DRM117 by Freescale Semiconductor Inc 2009 3 Phase BLDC Sensorless Control using MCF51AG128 DRM123 by Freescale Semiconductor Inc 2011 BLDC Motor Control with Hall Effect Sensors Using MQX on Kinetis AN4376 by Freescale Semiconductor Inc 2011 For the above list of documentation see http www freescale com 9 2 Acronyms and abbreviations Table 9 1 Acronyms O ig AC Alternating current ADC Analog to digital converter API Application interface ASM Application state machine BDM Background debug mode BEMF Back electromotive force Table continues on the next page 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 65 SS al Acronyms and abbreviations Table 9 1 Acronyms continued Y ig BLDC Brushless DC motor CCW Counter clockwise direction CW Clockwise direction DAC Digital to analog converter DC Direct current DMA Direct memory access module DRM Design reference manual DT Dead time a short time that must be inserted between the turning off of one transistor in the inverter half bridge and turning on of the complementary transistor because of the limited switching speed of the transistors FTM FlexTimer module GPIO General purpose input output 1 0 Input output in
4. 7 2 BLDC drive operational modes 7 2 1 Speed closed loop If the application is set to the speed closed loop mode the user can set the required speed by the Free MASTER or web server The DC bus current torque is automatically limited according the potentiometer on the TWR MC LV3PH board In this case the BLDC drive maintains the required speed until the maximal DC bus current torque is exceeded 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 53 Control interfaces 7 2 2 Speed open loop Enables or disables the speed regulator To switch to this mode it is necessary to change the parameter Closed Loop to disable in the Free MASTER control interface Switching to this mode is possible only when the required speed is other than zero because the start up sequence depends on the required speed variations In this mode the duty cycle parameter can be changed from 50 to 100 7 2 3 Standstill detection If a rotor is locked the software periodically tries to restart 1t If the required speed is equal to zero the software turns off the PWM if a motor is stopped for more than 2 s To switch to this mode it is necessary to change the parameter Standstill Detection to disable in the Free MASTER control interface 7 3 Control interfaces 7 3 1 FreeMASTER control Remote operation can be provided by Free MASTER software via the SCI to USB in
5. The PI controller routine is calculated in the interrupt routine of the PIT device in PITO_isr which is called every 1 ms The integral part of the PI controller is disabled at low speeds under 299 RPM because in that case measurement of speed is not accurate and the PI controller can be unstable In the program there are two macros MIN_CW_SPEED_32 and MIN_CWW_SPEED_32 to determine when the integral part of PI should be disabled The first input value of the PI controller is the variable speed_scaled that is the output from the ramp algorithm The second input is the actual speed_measured The other two inputs are pointers to the structure of the PI controller parameters trMyPI All these parameters are used by the PI controller function GFLIB_ControllerPIp The output of this function is s32Output It is scaled to the PWM scale as delta_duty and is added to half_duty The result of this process is duty_cycle which is loaded into the Flex Timer registers The PI speed controller parameters must be configured each time the speed scale is changed or when the motor is changed 6 4 Interrupt installation The difference between the bare metal version and the MQX version is only in the method used to install interrupts The method used depends on whether MQX or Bare_Metal is predefined in the IAR project options Options C C Compiler Preprocessor Defined symbols 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0
6. The alignment state performs the alignment in two sectors to avoid a bad alignment The duration of alignment depends on the value of ALIGNMENT_CYCLE macro in the BLDC h This value is in PIT timer cycles The default value is 6 which means the duration of the alignment is about 6 ms The applied voltage can be changed using parameter START_DUTY_CYCLE in BLDC_config h This value is a percentage of input voltage After the motor is in a known position the next sector is applied to the motor according to the desired motor direction Then the ASM goes into the run state where zero crossing is employed and the control loop is closed During the run state requests for new speeds and torques are accepted and maintained by the PI controllers If a standstill of the rotor is detected the ASM goes again into the alignment state and tries to execute a new start up sequence In the case of any fault the ASM goes into the error state The ZC detection process compares the actual BEMF voltage phase_bemf with half of the DC bus voltage half_dc_bus The appropriate phase voltage vector is chosen based on the sector sector The ZC detection process defines the start interval of BEMF integration The required value of the speed speed_req is updated based on commands from the user The required speed slope is limited by a ramp to avoid exceeding the maximal motor current The speed controller output together with the current limit defines the duty cyc
7. constants Table 8 1 main h application constants FMSTR_UART_PORT UART3_BASE_PTR FreeMASTER port set up FMSTR_UART_VECTOR 67 FreeMASTER interrupt vector set up FMSTR_UART_BAUD 19200 FreeMASTER speed set up CORE_CLK_KHZ 48000 Core clock set up The application header file BLDC h includes the following application constants See BLDC motor parameters BLDC h e FULL_DUTY e HALF_DUTY e MIN MAX_CW CCW_SPEED FRACI16 e MIN MAX_MES_CW CCW_SPEED FRACI16 e MIN_CW CCW_SPEED_32 e RAMP_SCALE_CONST e SPEED_TO_RPM_SCALE e SCALE_CONST e PHASE_A B C_FALLING RISING e SKIP_PWM_CYCLE e STAND_THRESHOLD e ENABLE DISABLE_PWM_OUTPUT_PADS e ALIGNMENT_CYCLE e MIN_DC_BUS e MAX_DC_BUS e OVER_CURRENT_TIME_THRESHOLD Application Status e IDLE 0 e STOP 1 e RUN 2 e ALIGNMENT 3 e EMERGENCY_STOP 6 e UNDER_VOLTAGE_FAULT 7 e OVER_VOLTAGE_FAULT 8 e OVER_CURRENT_FAULT 9 The application header file BLDC_config h includes the following application constants See BLDC motor parameters BLDC_config h e PP 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 61 A AA Microcontroller memory usage e TPM_C e MAX_SCALED_SPEED e PWM_FREO e BEMF_THRESHOLD e START_DUTY_CYCLE e SPEED_RAMP_UP e SPEED_RAMP_DOWN e PL PROP_GAIN e PLINTEG_GAIN e PLINTEG_GAIN_SHIFT e PI INTEG_PART The application header file freemaster_cfg h includes Free MA
8. 1 Return Measured speed in signed short data format The value is in rpm 4 signed short Get_req_speed int motor_number First parameter is the number of the motor which receives the command Return Required speed in signed short data format The value is in rpm 5 void Set_ramp_up int motor_number int ramp_up First parameter is the number of the motor which receives the command Second parameter Ramp up profile The value is in rpm per second Return void 6 void Set_ramp_down int motor_number int ramp_down First parameter is the number of the motor which receives the command Second parameter Ramp down Profile The value is in rpm per second Return void 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 58 Freescale Semiconductor Inc Chapter 8 Software And Peripherals Overview 8 1 Software listing The code is written in C IAR Embedded Workbench for ARM 6 3 The software consists of the following code files e application source code files e main c e BLDC C e Demonstration c e peripheral c e MC33927 c e application header files e main h BLDC h e BLDC_config h e peripheral h e MC33927 h e freemaster_cfg h The application source file main c contains the following software routines e main This is the entry point following a Reset It calls the initialization routines e FreeMasterInit Initialization of FreeMASTER The application source file BLDC c inclu
9. 4 System Concept The first three samples after commutation are not considered for Back EMF voltage detection because of transient event The freewheeling delay can be changed in the reference design S W in the SKIP_PWM_CYCLE constant in the BLDC h file The zero crossing detection process can be seen in Figure 4 5 PWM Switching Phase Voltage Commutation threshold Freewheeling interval Figure 4 5 Zero crossing detection process 4 5 Sensorless commutation control This section presents a sensorless BLDC motor commutation with the Back EMF zero crossing technique and the Back EMF integration technique In order to start and run the BLDC motor the control algorithm has to go through the following processes e Stop e Alignment e Run First the rotor is aligned to a known position without the positional feedback When the rotor moves the Back EMF is induced on the non fed phase and sensorless position detection can be employed As a result the position is known and can be used to calculate the speed and process the commutation in the Run state 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 27 Current Torque limitation Zero crossing Low speed Medium speed High speed Figure 4 6 BEMF integration method In this technique the commutation instant is determined by integration of the non fed phase s Back EMF that is the unexcited
10. Blue lines determine the time when the Back EME voltage can be sensed during the designated intervals Green lines determine the 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 17 Mathematical description of a brushless DC motor time when the zero crossing detection can be enabled The red line shows when the BEMF voltage is integrated and at the end of the red interval there is the next commutation Electric Angle Real BEMF Voltage Ideal BEMF Voltage ADC measuring interval phase unpowerea Conduction interval phase powered mw Searching for zero cross a Integration of BEMF Figure 2 8 Single phase voltage waveform For more detailed information about BEMF sensing see References 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc Chapter 3 Motor Control With The MXQ RTOS 3 1 What is MQX Freescale s MQX Software Solutions offer a straightforward API with a modular architecture making it simple to fine tune custom applications and scalable to fit most requirements The combination of market proven Freescale MQX Software Solutions and silicon portfolio provides a streamlined and powerful platform by creating a comprehensive source for hardware software tools and services needs 3 2 When to use motor control with the MQX RTOS MQX is not a typical operating sys
11. WANNA yy PA i ini M M Vy ny iH whey mW WHEY Ny NAW WA AA A LTVWIW SN AAA A Ne SL O 7 1 00 Y 3 MEAT Z 10 0ms 5 00MS s F 0 0mv 10M points 20 Aug 2010 09 17 30 Figure 6 7 Motor BEMF voltage Table 6 1 Commutation table A B C 1 DCB DCB NC PHASE_C_RISING 5 NC DCB DCB PHASE_A_FALLING 4 DCB NC DCB PHASE_B_RISING 6 DCB DCB NC PHASE_C_FALLING 2 NC DCB DCB PHASE_A_RISING 3 DCB NC DCB PHASE_B_FALLING 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 44 Freescale Semiconductor Inc Ey Chapter 6 Software Design The application constants are split into BLDC h and BLDCconfig h File BLDCconfig h deals with main motor parameters such as electrical and mechanical parameters of the BLDC the speed scale and parameters of particular states like alignment start up and run File BLDC h deals with the application parameters which are needed only for a detailed setting of the application 6 1 9 Process sequence error and current measurement PDB_error_isr is used for two purposes The first function of this interrupt is to clear an error flag which can occur because of a sequence error A sequence error typically happens because a delay is set too short and a pre trigger asserts before the previously triggered ADC conversion has completed For example a sequence error occur when a breakpoint is included into the program It is necessary to dis
12. angle between the stator flux and the rotor flux is kept close to 90 to get the maximum generated torque Because of this fact the motor requires electronic control for proper operation Voltage tase Phase A Una Ube Phase B Uaa L Phase C 30 60 90 120 150 180 210 240 270 300 330 Electrical angle Figure 2 2 Voltage strokes applied to the 3 phase BLDC motor For the common 3 phase BLDC motor a standard 3 phase power stage is used as is illustrated in Figure 2 3 The power stage utilizes six power transistors 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 12 Freescale Semiconductor Inc Chapter 2 Control Theory Phase_A Phase_B Phase_C Figure 2 3 3 phase BLDC power stage In both modes the 3 phase power stage energizes two motor phases concurrently The third phase is unpowered see Figure 2 2 Thus we get six possible voltage vectors that are applied to the BLDC motor using a PWM technique There are two basic types of power transistor switching independent switching and complementary switching 2 3 Complementary versus independent switching With complementary switching two transistors are switched on when the phase of the BLDC motor is connected to the power supply But there is a difference during freewheeling With independent switching all the transistors are switched off and the current continues to flow in the same dir
13. minimal execution duration The disadvantage of the kernel interrupt is that no MQX functionalities such as events or semaphores are supported For a better understanding of how to use kernel interrupts see the following example Installation of interrupts _int_install_kernel_isr INT_PITO PITO isr _int_install_ kernel isr INT_ADCO ADCO _isr _int_install_ kernel isr INT_ADC1 ADC1_isr _int_install_ kernel _isr INT_PDBO PDB error_isr Set priority of interrupts _bsp_ int init IRQInterruptIndex INT _PITO 1 0 1 _bsp_ int init IRQInterruptIndex INT _PDBO 2 0 1 0 0 0 0 _bsp_int_init IRQInterruptIndex INT_ADCO 1 _bsp_int_init IRQInterruptIndex INT_ADC1 Is 6 5 BLDC motor parameters BLDCconfig h 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 47 AE Applications parameters BLDC h 6 5 1 Speed scale parameters The following parameters are used for the speed_ measured scaling An incorrect setting of these parameters will also cause an incorrect functioning of the speed regulator define PP 2 Number of motor pole pairs 1 8 define TPM_C 48e6 Flex Timer 1 input clock define TPM P 128 Prescaler of Flex Timer 1 1 128 define MAX SCALED SPEED 5000 0 Maximal theoretic speed include reserve Decimal point is necessary 6 5 2 Applications parameters define USE _FREEMASTER 1 FreeMASTER usage
14. the ADC1_isr or ADCO_isr interrupt The process is called after the A D conversion when a new sample of phase voltage BEMF is available This new sample is compared to the midpoint of the DC bus voltage Details of zero crossing detection are described in Back EMF sensing If zero crossing is detected the integration of the BEMF voltage is started Every new sample is added to the integral_bemf after the half_dc_bus is subtracted Then the new commutation event occurs after bemf_threshold is reached ADC1_isr is more complex because ADC1 is used for DC bus current and DC bus voltage measurement It is very important to recognize which result is in the result register Flow charts of each service routine are shown in Figure 6 4 and Figure 6 5 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 38 Freescale Semiconductor Inc AAA AA AA Chapter 6 Software Design Figure 6 4 ADCO interrupt service routine 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 39 Introduction Figure 6 5 ADC1 interrupt service routine 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 40 Freescale Semiconductor Inc E Chapter 6 Software Design 6 1 3 Process speed calculation The commutation period is filtered to get suitable input values to the speed PI controller The value is calculated as the average from the la
15. value 6 define ALIGNMENT CYCLE 6 In this application an alignment in two sectors is performed This constant defines the time when the alignment is switched to the second sector define ALIGNMENT CYCLE HALF ALIGNMENT CYCLE 2 This constant defines the minimal DC bus voltage Constant is not scaled so it is a relative value Default value 170 is adequate to 12 V define MIN _DC BUS 170 Minimal DC BUS voltage 12 V This constant defines the minimal DC bus voltage Constant is not scaled so it is a relative value Default value 410 is adequate to 29 V define MAX DC BUS 410 Maximal DC BUS voltage 29 V 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 49 Speed scale This constant defines the time period when an overcurrent fault is triggered Depends on the PIT timer frequency Default value 400 ms define OVER CURRENT TIME THRESHOLD 400 6 7 Speed scale This application uses a fractional representation for speed The N bit signed fractional format is represented using thel N 1 format 1 sign bit N 1 fractional bits Signed fractional numbers SF lie in the following range _10 lt SF lt 10 2 47 For words and long word signed fractions the most negative number that can be represented is 1 0 whose internal representation is 8000 and 80000000 respectively The most positive word is 7FFF or 1 0 2 15 and the most positi
16. 06 2012 46 Freescale Semiconductor Inc EES EE ass Chapter 6 Software Design In the bare metal version we can install an interrupt directly You can simply allow an interrupt by setting the right bit in the NVICISER register Priority of the interrupt can be configured using the register NVIC_IP For a better understanding see the following example Installation of interrupts NVICICPR1 1 lt lt 25 clear a possible pending interrupt first NVICISER1 1 lt lt 25 enable ADCO interrupt NVICICPR1 1 lt lt 26 clear a possible pending interrupt first NVICISER1 1 lt lt 26 enable ADC1 interrupt NVICICPR2 1 lt lt 4 clear a possible pending interrupt first NVICISER2 1 lt lt 4 enable PITO interrupt NVICICPR2 1 lt lt 8 clear a possible pending interrupt first NVICISER2 1 lt lt 8 enable PDB interrupt Setup priority of interrupts NVIC_IP 68 0xC0 set priority for PITO NVIC_IP 58 0x90 set priority for ADC1 NVIC_IP 57 OxA0 set priority for ADCO NVIC_IP 72 0x80 set priority for PDB If the installation of interrupts in MQX is the same as in the bare metal version MQX would not work correctly The MQX s own interrupts are quite slow for motor control applications The best solution for high speed applications is kernel interrupts The kernel interrupts are natural CPU interrupts with no MQX overhead and
17. 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Document Number DRM135 Rev 0 06 2012 V Wo freescale 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc Contents Section number Title Page Chapter 1 Introduction A e o EE EAIRT 1 2 Freescale KoQ advantages and TS a 8 Chapter 2 Control Theory 21 Brushes DC moni BEDE MOOT onre n unas aneniabincadsGuincdacaink capleneliauaycneledaiasanaataccaraesoasscecs 11 22 Digital coutolota BLDC Md E E 11 2 Complementary versus independente ERE id a einem ebabeeits 13 al AUR Pida 13 24 Mathematical description of a brushless DC Molins 16 24 1 Power stage motor system model escri 16 DAZ Back EMF songing a A 17 Chapter 3 Motor Control With The MXQ RTOS TL IS A ca 19 3 2 When to use motor control with the MOX RTOS ina 19 gt Howto impiement molor Geir and MOX A A aa 19 Chapter 4 System Concept AENSONES DIN CODE A An aii 21 4 to blocks eo la E E O E E E E O E 23 Azi PWM vols seneration tora brushless DC mOr miswier sea iE a R RaT 23 Le ADC t0 PWM ii 23 AA Back EMF TELE A ds 26 23 Serea pAn OO a A 27 206 Current Tague MNAO ds 28 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc Section number Title Page Chapter 5 Hardware A ati ldide embed a Gu ahbuss ese naiaicdibeamaduesdunaeds 31 E A A O quae sedactanss ase 31 L T
18. LY en ecesccccceccecccscceccescesceeecesceacceccecee 2 ina PDB_DLY1 FTMO_CNTIN i PDB_DLYO Trigger 0 Trigger 1 PDB Interrupt DCB voltage BEMF voltage DCB current Figure 4 4 FTM PWM to ADC Synchronization with PDB 4 4 Back EMF zero crossing sensing The Back EMF zero crossing is detected by sensing the motor s non fed phase branch voltage u in Back EMF sensing and the DC bus voltage ud using the ADC To get the right Back EMF voltage two assumptions have to be made e Top and bottom switches in diagonal are driven by the same PWM signal e No current is going through the non fed phase used to sense the Back EMF The first assumption is achieved by the FTM PWM module The FTM ADC synchronization at the centre of the PWM ON pulse is done by the PDB module The second condition can be detected directly from the sensed Back EMF voltage As soon as the phase is disconnected from the DC bus current still flows through the freewheeling diode The conduction time depends on the momentary load of the motor In some circumstances the conduction time is so long that it does not allow for detection of Back EME voltage The conduction freewheeling diode connects the released phase to either a positive or a negative DC bus voltage The next step taken is done to detect current in the non fed phase 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 26 Freescale Semiconductor Inc Chapter
19. MQX in a time critical application The application contains two versions of the application software One is with the MQX RTOS and the other is bare metal Both use the same source code for motor control The MQX version contains a web server to demonstrate the benefits of an MQX based solution This reference design includes a basic motor theory the system design concept hardware implementation and software design including the FreeMASTER software visualization tool The hardware is built on the Freescale Tower rapid prototyping system and contains the following modules e TWR Elevator e TWR K60N512 e TWR MC LV3PH e TWR SER 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 7 IEA A Freescale K60 advantages and features This design shows the advantages of the motor control peripherals of the Kinetis microcontrollers The control algorithm will include e start up with rotor alignment e sensorless position detection using integration of Back EMF voltage e speed closed loop e current limitation e fault protection 1 2 Freescale K60 advantages and features The 32 bit Kinetis MCUs represent the most scalable portfolio of ARMY Cortex M4 MCUs in the industry The first phase of the portfolio consists of five MCU families with over 200 pin peripheral and software compatible devices with outstanding performance memory and feature scalability Enabled by inn
20. STER settings The application header file MC33927 h includes MOSFET driver settings 8 2 Microcontroller memory usage Table 8 2 shows how much memory is needed to run the 3 phase BLDC sensorless drive without FreeMaster and MQX using the PK60N512VMD100 microcontroller A significant part of the microcontroller memory is still available for other tasks Table 8 2 Memory usage FLASH 512 KB 8 5 KB RAM 128 KB 0 4 KB 8 3 Peripherals usage For the proper functioning of this application the following peripherals must be used It is not allowed to use these peripherals for any other purpose Table 8 3 Peripherals usage e JA Timer PIT O Periodic call of the speed control loop application state machine speed ramp etc e Period of an interrupt is 1 04 ms at 48 MHz core clock Flex Timer FTM O Generate a PWM signal Run in combine mode Switching frequency is 16 kHz on a 48 MHz core clock Dead time 800 ms Table continues on the next page 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 62 Freescale Semiconductor Inc SSS ee ee AA Chapter 8 Software And Peripherals Overview Table 8 3 Peripherals usage continued ee pos Flex Timer FTM 1 e Speed measurement e Prescaler is set to 128 e Modulo is OxFFFF e Period of overflow is 175 ms ADCO e Channel 19 Used for the BEMF phase C sensing ADC 1 e Channel 19 Used for the BEMF phase A sensing e C
21. YR KOONS cui lid da 3A Mota LINA WNA Aio aore i e anaa a E iaia iia 34 Chapter 6 Software Design A A 3 61 1 Applicaton SO DE main ORB A A A aE ER E oea Eaa 36 01 2 Process Zeno CRS MIE CONE RMD A A E EEA ANE EEE ERA 38 Us Toces poel et aN aT I ssaa a tad pbs Melk aed ude anicsanesas blu buecupdeceoubunsalseed 40 Lidl Trocess RU AO ia 41 GLa SP Ome es COMICO petiso idas aplican 41 Go Pea o a 42 GET a FEREENA ITER sienn E RO 43 5 1 9 Process PWM update ir AA 43 6 1 9 Process sequence error and current MEASUILEMENL iii A 45 G2 Process manta COOL AA Ai 46 0o Process speed PLONE fs iccasjcccsescisnagdseapasts eacdcomndauesions ouanes ean tonibecnteians qaapeceeebantapidasstesaieiaissanleduituaiecapissgaaeciesutlvaniedaiia 46 6 Lisa pias LICL Tn pr ad 46 65 BLDC motor parameters CALC SO aria id A 47 0l Speed scale PAR a 47 A AAA PU iaa 48 6 Appliconons parameters BLDC Di ia 48 6 7 pepsi AA ia 50 Chapter 7 Sensorless BLDC Demo Operation Fed PABA at COI anria a aE A ia 53 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 4 Freescale Semiconductor Inc Section number Title Page T2 BLDC Give Operatic Ai 53 HAL SAPO CIO ad fr ici 53 O O 54 Pes IAS ASE ad RA AAA A AAA 54 e A A eee eededs 54 To RENTAS TER ii 54 A E aE 56 7A Integration of the motor control driver into other appl Catron vig ccssasaccsisecasosnenancusowoessoreveettscaiisacnienstastsnesdbenseiaueunenoaice S7 Chapter 8 Software And Periphera
22. _ _ _ _ _ _ _ _ _ _ Chapter 1 Introduction e Micrium uC OS III e Express Logic ThreadX e SEGGER embOS e freeRTOS e Mocana security e Full ARM ecosystem 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 9 Freescale K60 advantages and features 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 10 Freescale Semiconductor Inc Chapter 2 Control Theory 2 1 Brushless DC motor BLDC motor A BLDC motor is a rotating electric machine where the stator is a classic 3 phase stator like that of an induction motor and the rotor has surface mounted permanent magnets see Figure 2 1 The same arrangement is used in the Linix 45ZWN24 40 Permanent magnets Stator Stator winding Shaft Rotor Air gap Motor center point Figure 2 1 BLDC motor cross section 2 2 Digital control of a BLDC motor The BLDC motor is driven by rectangular voltage strokes coupled with the given rotor position see Figure 2 2 The generated stator flux interacts with the rotor flux which is generated by a rotor magnet defines the torque and thus the speed of the motor The voltage strokes must be properly applied to the two phases of the 3 phase winding system 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 11 Digital control of a BLDC motor so that the
23. able the PBD block clear the error flag and enable the PDB block again m Figure 6 8 PDB interrupt service routine flow chart The second purpose of this interrupt is for current measurement When the PDB_IDLY is reached the PDB_error_isr interrupt is called In this process the ADC is reconfigured to Software Trigger mode The measurement is started on ADC1 channel 12 where a DCB current signal is connected When the conversion has completed the result of the DCB current is saved and the ADC1 is reconfigured back to DCB voltage measurement Flow charts of this process are shown in Figure 6 8 and Figure 6 5 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 45 Process manual control 6 2 Process manual control Software can be controlled by three buttons that are periodically scanned in the PIT_isr loop All buttons are placed on the TWR K60N512 board Button SW1 is used for an emergency stop of the motor Button SW2 is used for demonstration of the application The last button is SW3 which is used for a processor reset There is also a potentiometer on the TWR MC LV3PH board used for the overcurrent level setting 6 3 Process speed PI controller The speed PI control algorithm processes the speed_error between speed_scaled and speed_measured The PI controller output is passed to the PWM generator as a newly corrected value of the applied motor voltage
24. d ADC triggering A ADC Trigger 2 50GS s E 20M points s00vv E 2 00v SF 1 64V ae Timing Resolution 2 00ns Coupling Invert 3 Wi ve peng Bandwidth 3 Label o 2 Mar 2012 DC AC on Off Full drli 15 05 10 Figure 4 3 BEMF voltage spikes and ADC triggering B 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 24 Freescale Semiconductor Inc ET Chapter 4 System Concept The non fed phase branch voltage is disturbed at the PWM switching edges Therefore the presented BLDC motor control application synchronizes the Back EMF zero crossing detection with the PWM The A D conversion of phase branch voltages is triggered at the centre of a PWM pulse Then the voltage for Back EMF is sensed at those time moments when the non fed phase branch voltage is already stabilized The K60N512 is equipped with a Programmable Delay Block PDB synchronization of the FTM PWM and ADC modules Therefore several assumptions have to be considered during the ADC sampling implementation The first factor is the choice of PWM modulation From this point of view the complementary bipolar switching is the best choice This PWM switching can be implemented in such a way that the duty cycle is in the range of 50 100 at any time of motor operation With unipolar switching the duty cycle starts from 0 It means that there is limitation for ADC sampling at narrow pulses regardless of whether hardware sy
25. des the following software routines e SPI_Send For communication with the MC33937 e MCU_init Initialization routine for peripherals and interrupts e Clock_init Initialization of the peripherals clock e Variables_reset Initialization of variables after a reset e App_state_machine State machine execution e Commutation Reconfigure and update the Flex Timer registers for PWM generation 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 59 LT Software listing e PITO_isr Periodic interrupt timer service routine 1 ms Executes the major part of the motor control algorithm Speed controller fault protection ramp execution speed scaling standstill detection and so on e ADCO_isr ADCO conversion complete e ADCI_isr ADC1 conversion complete e PDB_error_isr Service for the PDB error and for the ADC channel switch for current measurement e Threshold_rising_bemf Observing the BEMF voltage up slope Searching for a zero crossing integrating the BEMF voltage and performing commutation after the threshold is reached e Threshold_falling_bemf Observing the BEMF voltage down slope Searching for zero crossing integrating the BEMF voltage and performing commutation after the threshold is reached e Speed_measure Save the FlexTimer 1 output value for computing the speed e Emergency_Stop Service of hazardous states
26. e Set_duty_cycle Update the duty cycle of the PWM e Mask_Swap Reconfigure PWM output channel according to commutation table e Demonstration Test sequence API see also Integration of the motor control driver into other applications e Set_speed e Set_ramp_down e Set_ramp_up e Get_req_speed e Get_speed e Get_status The application source file Demonstration c contains the following software routine e Demonstration Only for demonstration of the demo with a button A sequence of speed changes and ramp changes for demonstration The application source file peripheral c contains the following software routines e PIT_init Periodic interrupt timer init e INT_init Interrupt initialization e FTMO_init Flex Timer 0 initialization for 3 phase PWM signal generation e FTMI_init Flex Timer 1 initialization for speed measure e SPI_init SPI module for communication with a driver e GPIO_init GPIO initialization e MC33927Config Configuration of driver e ADCinit Analogue converters initialization e PDBinit Programmable delay block initialization 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 60 Freescale Semiconductor Inc yyy eS ae a Chapter 8 Software And Peripherals Overview The application source file MC33927 c contains the configuration of the 3 phase MOSFET driver The application header file main h includes the following application
27. ection through freewheeling diodes until it falls to zero Contrary to this with complementary switching the complementary transistors are switched on during freewheeling Thus the current may be able to flow in the opposite direction Figure 2 4 depicts the complementary switching 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 13 Complementary versus independent switching P VWV sw itching on PWM Q1 OFF on PWM Q2 OFF ON PWM 03 OFF on PWM Q4 OFF ON PWM QS OFF ON PWM 06 OF ADIOS NADIA NAM DAN UUW UU LOU UUUUUUUUUUUUUUUUUUUL UL 10 20 30 40 50 60 70 80 80 Figure 2 4 Complementary switching of power transistors Dead Dead Dead Dead Dead Dead Time Time Time Time Time Time IiI I Dead Dead Time Time Swap Figure 2 5 Bipolar PWM switching detail Bectrical angle Dea d Dea d Time Time 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc E Chapter 2 Control Theory Details of the technique are shown in Figure 2 5 From Figure 2 5 we can see the characteristic of the bipolar 4 quadrant complementary switching The bipolar switching requires that the top and bottom switch PWM signals need to be swapped Another important detail is the introduction of dead time insertion in the complementary top and bottom signals This dead t
28. ector Overcurrent threshold Brake Resistor Connector Primary Elevator Figure 5 2 TWR MC LV3PH Image 5 3 TWR K60N512 The TWR K60N512 microcontroller module is part of the Freescale Tower System a modular development platform that enables rapid prototyping and tool re use through reconfigurable hardware e Kinetis K60N512 device Cortex M4 e Tower connectivity for access to USB Ethernet RS232 RS485 CAN SPI PC TWR Serial e Touch TWRPI socket adds support for various capacitive touch boards key pads rotary dials and sliders TWR MC LV3PH e Capacitive touch pads e Integrated open source JTAG e SD card slot e MMA7660 3 axis accelerometer e Tower plug in TWRPI socket for expansion sensors e flexbus e Potentiometer four LEDs two pushbuttons infrared port 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 33 AAA TA Motor LINIX 45ZWN24 40 Figure 5 3 Image of TWR K60N512 5 4 Motor LINIX 45ZWN24 40 The following motor is used by the BLDC Sensorless application Of course other motors can also be adapted to the application just by defining and changing the motor related parameters A detailed motor specification is shown below Table 5 1 Motor parameters Rated Voltage Vt 24 V Rated Speed Vt 4000 rpm Rated torque T 0 0924 Nm Rated power P 40 WwW Continuous Current Ics 2 34 A Number of Pole Pairs PP 2
29. ed fully by the SCI interface Free MASTER writes new values through the SCI interface into data RAM where particular variables are located This operation is executed every time the Free MASTER FMSTR_Poll and FMSTR_Recorder functions are executed 6 1 8 Process PWM update This process generates the correct voltage pattern on the motor based on the actual PWM sector and required output voltage The process is called every 1 ms in the PITO_isr interrupt The commutation table is derived from Back EMF voltage measured on the motor see Figure 6 7 Besides the proper commutation pattern the Back EMF sensing can be evaluated from Figure 6 7 For example if phase C is connected to a positive DC bus voltage and phase B is connected to a negative DC bus voltage the falling Back EMF voltage of phase A has to be evaluated for zero crossing The resultant commutation table includes sensing of the Back EMF voltage as can be seen in Table 6 1 Commutation table for counter clockwise direction 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 43 Introduction LINIX 45ZWN24 40 BLDC motor Counter Clockwise direction A TOP A TOP C TOP C TOP B TOP B TOP Phase A white yellow motor picture Phase State C BOT B BOT B BOT ABOT A BOT C BOT Phase B blue cyan B OFF COFF A OFF B OFF C OFF A OFF Phase C green violet Vector Number 3 1 5 4 6 2 Tek AN M MANN if ANY M
30. ed speed Ramp Output Speed Speed Required Duty cycle 20 40 Time sec algorithm block description__osciloscope Speed Reguired a0 Value j Commutation Threshold 2000 DEC Unit a Standstill Detection Ready R5232 COM1 speed 19200 Scope Running Figure 7 1 FreeMASTER control interface Description of variables Speed Required This variable serves for entering the required speed of the motor and the direction of motion If the number is negative the motor runs in a counter clockwise direction and when it is positive the motor runs clockwise You can modify this variable from 400 to 4000 and from 400 to 4000 Any other numbers will be ignored Commutation Threshold For commutation timing BEMF integral threshold Measured Speed Variable shows the actual motor speed Standstill Detection Detection of a rotor standstill If a rotor is locked the software periodically tries to restart it If the required speed is equal to zero the software turns off the PWM if a motor is stopped for more than 2 s 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 55 Control interfaces Closed Loop Enable or disable the speed regulator If it is disabled the Duty cycle parameter can be changed from 50 to 100 Integral Gain Proportional Gain S
31. er than zero the application enables PWM output and starts a motor The speed control loop 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 36 Freescale Semiconductor Inc Ey Chapter 6 Software Design is called periodically by a PIT 0 In this periodic loop there is the major part of the software a speed ramp speed regulator fault protection application state machine and so on ADC measurement is called by the ADC to PWM synchronization every 62 5 us After a conversion has completed ADCO_isr or ADC1_isr is called The application data flow diagram with the main processes is shown in Figure 6 2 The variables are described at the end of this section Endless loop Figure 6 2 Main loop flow chart As mentioned before the complete motor control algorithm is driven by interrupts The main function is used only for the MCU and application initialization see Figure 6 2 When initialization terminates the program goes into an endless loop For all periodic functions the periodic interrupt service routine is used A flow chart of the periodic interrupt timer service routine is shown in Figure 6 3 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 37 Introduction Figure 6 3 Periodic interrupt timer service routine flow chart 6 1 2 Process zero crossing detection This process is called every 62 5 ms in
32. ervals by 6 because in SCALE_CONST this is already included Finally the speed_measured is calculated by this equation 1 measured speed _ SCALE CONST time measured 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 51 Speed scale 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 52 Freescale Semiconductor Inc Chapter 7 Sensorless BLDC Demo Operation 7 1 Application control There are two versions of the application software BLDC under the MQX RTOS and web server e BLDC on bare metal Both applications can be also controlled by the FreeMASTER software This FreeMASTER PC application allows real time monitoring or modification of all required variables through an easy and user friendly graphical user interface Selected variables can be also monitored in a time domain scope representation The MQX version can be controlled from any web browser on a PC via the Ethernet communication interface because in this version the web server is implemented Both versions of the software can be controlled by three buttons on the TWR K60N512 board Button SW1 is used for an emergency stop of the motor Button SW2 is used for demonstration of the application The last button is SW3 which is used for a processor reset There is also a potentiometer the TWR MC LV3PH board used for the overcurrent level setting
33. ev 0 06 2012 48 Freescale Semiconductor Inc Chapter 6 Software Design This constant defines when the integral part of regulator is disabled for better stability default value 299 define MIN_CW SPEED 32 299 0 define MIN _CWW SPEED 32 299 0 This constant is used to scale fraction parameters of the speed ramp to real physical units rpm s It depends on the frequency of the PIT Number 0 00104 means a period PIT 1 04 ms define RAMP SCALE CONST 0 00104 MAX SCALED SPEED This constant is used to scale fraction parameters of the speed to real physical units rpm Number 32768 is the maximum value of a signed integer define SPEED _ TO RPM SCALE 32768 0 MAX SCALED SPEED This is the speed scale constant For more information see Speed scale define SCALE CONST unsigned long 6 60 PP TPM_P TPM_C MAX SCALED SPEED This constant defines how many PWM cycles are skipped during a freewheel diode interval before a BEMF measurement starts To that value is always added the number 1 Thus the minimal possible output value is 1 when a zero is entered into this constant Default value 2 define SKIP PWM CYCLE 2 This constant defines the maximal time between two commutations for the rotor standstill detection Depends on the PIT timer frequency Default value 25 ms define STAND THRESHOLD 25 This constant defines the time to make an alignment Depends on the PIT timer frequency Default
34. frica Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen Germany 44 1296 380 456 English 46 8 52200080 English 49 89 92103 559 German 33 1 69 35 48 48 French www freescale com support Japan Freescale Semiconductor Japan Ltd Headquarters ARCO Tower 15F 1 8 1 Shimo Meguro Meguro ku Tokyo 153 0064 Japan 0120 191014 or 81 3 5437 9125 support japan Ofreescale com Asia Pacific Freescale Semiconductor China Ltd Exchange Building 23F No 118 Jianguo Road Chaoyang District Beijing 100022 China 86 10 5879 8000 support asia freescale com Document Number DRM135 Rev 0 06 2012 Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductors products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Freescale Semiconductor reserves the right to make changes without further notice to any products herein Freescale Semiconductor makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Freescale Semiconductor assume any liability arising out of the application or use of any product or circuit and specifically disclaims any liability including without limitation consequential or incidental damages T
35. hannel 10 Used for the DCB voltage sensing e Channel 0 Used for the BEMF phase B sensing e Channel 12 Used for the DCB current sensing SPI 2 e Communication with the MC33937 MOSFET predriver Ethernet e Web control SCI O e FreeMASTER interface PDB O e ADCO and the ADC1 to PWM synchronization PTA 10 e Used to indicate the first level of overcurrent on the MC33937 MOSFET predriver PTA 11 e Used to indicate FAULT mode PTA 19 Used for the emergency stop button PTA 27 e Used to read the overcurrent pin on the MC33937 PTA 28 e Used to indicate the demonstration of the application PTA 29 e Used to indicate RUN mode PTE 26 e Used for the demonstration button 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 63 Peripherals usage 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 64 Freescale Semiconductor Inc Chapter 9 References 9 1 References 1 Ze 3 3 Phase BLDC PMSM Low Voltage Motor Control Drive User s Manual LVMCDBLDCPMSMUG Initial version by Freescale Semiconductor Inc 2009 K60 Sub Family Reference Manual K60P144M100SF2RM by Freescale Semiconductor Inc 2011 Set of General Math and Motor Control Functions for Cortex M4 Core MCLIBCORETXM4UG by Freescale Semiconductor Inc 2011 3 Phase BLDC Motor Sensorless Control using MC9SOSAW60 DRMOS6 by
36. he system possibilities One approach is ramp generation This ramp implements steps between the actual speed and the speed command The process is executed every 1 ms in the P TO_isr interrupt In this application a ramp is used from the library GFLIB This ramp needs three parameters The first two parameters are the up and down angles of the ramp The last parameter is the required speed All three parameters are in 32 bit fractional data format It is possible to enter the first two parameters in BLDC_config h as integers in rpm s but they are recalculated back to frac32 during application initialization The parameters are named SPEED_RAMP_UP and SPEED_RAMP_DOWN The ramp execution is highly dependent on the PIT period The default value is 1 ms If the period of PIT is changed it is necessary to change the PIT period in the RAMP_SCALE_CONST macro This macro is used to compute SPEED_RAMP_UP and SPEED_RAMP_DOWN from int to frac32 The second possibility for entering the speed ramp parameters is to use FreeMASTER In FreeMASTER data can be entered as an integer in rpm s at program runtime In the MQX version ramp parameters can be changed using web server buttons 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 42 Freescale Semiconductor Inc a Chapter 6 Software Design 6 1 7 Process FreeMASTER The Free MASTER process is part of the application software Free MASTER communication is implement
37. ime insertion is typical for all 4 quadrant power stage operations The 4 quadrant operation is enabled by the complementary operation of the top and bottom switches The bottom switch of one phase is almost the negative of the top switch This requires the insertion of a dead time because the switching transient will cause a DC bus short circuit with fatal power stage damage The bipolar PWM switching is not as popular as the unipolar switching because of a worse electromagnetic emission of the motor This is because the PWM ripple is twice that of the DC bus voltage On the other hand this switching is better for sensorless rotor position sensing Details are described in the documentation see References 2 3 1 The 4 quadrant operation As described in the previous sections the amplitude of a 3 phase voltage system needs to be controlled The most common BLDC control topology uses the power stage with a constant POWER SOURCE DC VOLTAGE Therefore the 3 phase average voltage amplitude is controlled by a PWM technique of the top and bottom transistors As described the 6 step controller uses one of the two PWM techniques 1 Bipolar PWM switching 2 Unipolar PWM switching There are a few derivatives of the two PWM switching techniques according to the operating quadrants of the power stage voltage and current 1 4 quadrant power stage control 2 2 quadrant power stage control The 2 quadrant operation provides a defined voltage a
38. in application 0 1 define PWM FREQ 16000 PWM frequency 5000 20000 define BEMF_THRESHOLD 2000 Commutation threshold define START DUTY CYCLE 25 0 Duty cycle during alignment 0 100 Decimal point is NECESSARY Ramp settings define SPEED RAMP UP 4000 Speed up ramp coefficient 100 20000 define SPEED RAMP DOWN 4000 Speed down ramp coefficient 100 20000 PI controller setting define PI PROP GAIN 0 33 P parameter of PI define PI_INTEG GAIN 0 0035 I parameter of PI define PI PROP GAIN SHIFT 1 Proportional Gain Shift define PI_INTEG GAIN SHIFT 1 Integral Gain Shift define PI_INTEG PART 0 Integral part of PI 6 6 Applications parameters BLDC h define FULL DUTY TPM_C PWM FREQ 100 duty cycle define HALF DUTY FULL DUTY 2 50 duty cycle This constant defines the value of the minimal required speed default value 400 rpm define MIN_CW_SPEED FRAC16 400 0 MAX_SCALED SPEED define MIN_CWW_SPEED FRAC16 400 0 MAX SCALED SPEED This constant defines the value of the maximal required speed default value 80 of the MAX_SCALED_SPEED define MAX CW SPEED FRAC16 0 8 define MAX CWW_SPEED FRAC16 0 8 This constant defines the value of the minimal measurable speed default value 200 rpm define MIN MES CW_SPEED FRAC16 200 0 MAX SCALED SPEED define MIN MES CWW_SPEED FRAC16 200 0 MAX SCALED SPEED 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 R
39. in the idea of the Back EMF sensing technique the basic circuit topology see Figure 2 7 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc Chapter 2 Control Theory o 0 0 o o Sat Sst Sct ZA ZA A m HH HL e e e e VDCB E Sab Spb Scb m lt A A A T a A o 0 0 Rshunt Figure 2 7 Power stage and motor topology The motor drive model consists of a 3 phase power stage plus a brushless DC motor The power for the system is provided by a voltage source VDCB Six semiconductor switches SA B C t b controlled elsewhere allow the rectangular voltage waveforms see Figure 2 2 to be applied The semiconductor switches and diodes are considered as ideal switches 2 4 2 Back EMF sensing The Back EMF sensing technique is based on the fact that only two phases of a brushless DC motor are energized at a time The third phase is a non fed phase that can be used to sense the Back EMF voltage The Figure 2 8 shows branch and motor phase winding voltages during a 0O 360 electrical interval The yellow interval means a conduction interval of a phase During this time current flows through the winding and BEMF voltage is impossible to measure After the commutation transient there is a current recirculation At this time the fly back diodes conduct the decaying phase current
40. le duty_cycle for the FIM PWM module The integral part of the PI controller is limited if the overcurrent flag from the MC33937 driver is triggered Once a fault condition occurs the application switches to the Fault state stops the motor and waits for a fault reset via the Reset switch on the TWR K60N512 board Beyond this the FreeMASTER interface enables monitoring and adjustment of all system variables 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 22 Freescale Semiconductor Inc SSS yy Chapter 4 System Concept 4 2 System blocks concept 4 2 1 PWM voltage generation for a brushless DC motor A 3 phase voltage system as described in Brushless DC motor BLDC motor needs to be created to run the BLDC motor This is provided by a 3 phase power stage with six power switches IGBTs or MOSFETs controlled by the Kinetis K60 on chip FTM PWM module When generating PWM signals for the BLDC motor control application the Bottom and Top power switches of the non fed phase must be switched off See Figure 2 5 For the BLDC motor control application PWM signals can be created in two ways Complementary PWM mode and Independent PWM mode Both these modes are available in Kinetis K60 FTM PWM module In complementary PWM mode the top and bottom switches of a phase are operated complementarily This mode has to be used if four quadrant drive operation is required This mode needs dead time insertion bet
41. lities such as events or semaphores are supported 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 20 Freescale Semiconductor Inc Chapter 4 System Concept 4 1 Sensorless drive concept The concept of this system is described below in the block diagram Figure 4 1 Input voltage BLDC Sensorless Motor Control Demo for K60 3ph low ds MC33927 voltage MOS FET ma power 3PH BLDC A motor driver stage Browser 1 Teal aad 139 Hel gt PBD App state PWM ADC Ethernet machine FlexTimer2 BEMF sense Commutation Buttons Speed computing FlexTimer1 and scaling Fault protection PI controller Speed Ramp Free MASTER Figure 4 1 Block diagram of system the concept The basic state machine operation of the system is as follows 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 21 po Sensorless drive concept The periodic interrupt timer service routine executes the application state machine ASM consisting of these states e stop e alignment e run e emergency stop e overcurrent e overvoltage e undervoltage After an MCU reset the application goes through the MCU_init function into the stop state The change of the speed_scaled is continuously monitored As soon as the user enters a value other than zero into speed_req the ASM switches the state to alignment
42. ls Overview AE T EE O E A T A A P ET O O AE E EE 59 6 2 Microcontroller memory IE di cal 62 E ANG GAGs acc E E E T E A E E A N E T E snd 62 Chapter 9 References oT REE 65 92 Acronyms and ADDIE UAB ecceri oraaa near ia 65 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 5 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc Chapter 1 Introduction 1 1 Introduction This design reference manual DRM describes the design of a sensorless 3 phase brushless DC BLDC motor drive based on Freescale s 32 bit Kinetis K60 device BLDC motors are very popular in a wide application area The BLDC motor lacks a commutator and is therefore more reliable than the DC motor The BLDC motor also has advantages when compared to an AC induction motor Because it achieves a higher efficiency by generating the rotor magnetic flux with rotor magnets a BLDC motor is used in high end white goods such as refrigerators washing machines dishwashers high end pumps fans and in other appliances that require a high reliability and efficiency The concept of the application is a speed closed loop BLDC drive using a sensorless BEMF zero crossing technique It serves as an example of a BLDC motor control design using a Freescale K60 device MCU It is focused on a simple and easy to understand control approach to BLDC and using
43. n RoHS complaint and or non Pb free counterparts For further information see http www freescale com or contact your Freescale sales representative For information on Freescale s Environmental Products program go to http www freescale com epp Freescale and the Freescale logo are trademarks of Freescale Semiconductor Inc All other product or service names are the property of their respective owners 2012 Freescale Semiconductor Inc te freescale K
44. nchronization is available or not In this case a different sensing method has to be chosen where the Back EMF voltage is compared to zero instead of the half DC bus voltage The right setting for the FTM PWM module is shown in Figure 4 4 The FTM PWM module is configured to run in complementary combined mode The PDB channel 1 can generate two triggers Trigger0 and Triggerl and one PDB interrupt Trigger 0 is used for DC bus voltage and Trigger 1 is used for BEMF voltage of phase A and phase B The DC bus current measurement is done by a PDB interrupt using an ADC software trigger After PDBO_IDLY is reached the PDB calls interrupt service routine which switches a channel of the ADC to measure the DCB current and then calls the ADC software trigger After conversion has completed and the result is read the ADC channel is switched back to the BEMF measurement mode PDB channel 0 generates one trigger Trigger 0 used for Back EMF sensing of phase C This arrangement is appropriate because of the hardware interconnections The result of the conversions can be read on the ADCO_isr or ADC1_isr interrupt The sampling process can seen in Figure 4 4 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 25 A Back EMF zero crossing sensing Phase A PWM Phase A PWM 1 FTMOMOD a eo i PDB_MOD FTM PDB Counter i FTMOC1V sn en Ow lt lt _ PDB_ID
45. nd current of the same polarity that is positive voltage with positive current or negative voltage and negative current which are the operating quadrants I and III in Figure 2 6 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 15 FE Mathematical description of a brushless DC motor Second Quadrant negative speed positive torque reverse braking _ First Quadrant positive speed positive torque forward accelerating Current Torque Generating Motoring IfI sen Motoring MI IV Third Quadrant negative speed negative torque 7 X s 3 reverse accelerating Generating Fourth Quadrant Positive speed pees torque z forward brakin Figure 2 6 The 4 quadrant operation The 4 quadrant PWM switching covers the operation of the generated voltage in all four quadrants This is provided using complementary switching of the top and bottom transistors The benefits of the 4 quadrant PWM operation are e Motoring and generating mode control possibility of braking the motor e Linear operation in all four quadrants The K60N512 is able to control the 3 phase power stage with unipolar and bipolar PWM with the more advanced 4 quadrant operation Therefore the 4 quadrant PWM technique will be used in this application 2 4 Mathematical description of a brushless DC motor 2 4 1 Power stage motor system model In order to expla
46. observed the integral part of the speed controller is divided by three to limit the output 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 28 Freescale Semiconductor Inc EEA Chapter 4 System Concept duty cycle If an overcurrent takes more than 400 ms a fault has occurred This value can be adjusted by OVER_CURRENT_TIME_THRESHOLD in the BLDC h file Overcurrent limitation is also performed by the MC33937 driver 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 29 Current Torque limitation 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 30 Freescale Semiconductor Inc Chapter 5 Hardware 5 1 Hardware The following hardware modules are needed for this application to function properly e TWR K60N512 e TWR Serial e TWR MC LV3PH e TWR Elevator e TAR J Link LITE cortex e BLDC Motor LINIX 45ZWN24 40 For a proper functioning of the hardware use the user manual BLDCSLK60UG to configure the jumpers on all the hardware modules This manual is available at http www freescale com 5 2 TWR MC LV3PH The 3 phase Low Voltage Motor Control board TWR MC LV3PH is a peripheral Tower System Module with one of the available MCU tower modules accommodating a selected microcontroller and provides a ready made software development platform for one third horsepower off line motors Feedback signal
47. ovative 90 nm Thin Film Storage flash technology with unique FlexMemory Kinetis features the latest low power innovations and high performance high precision mixed signal capability Kinetis MCUs are supported by a market leading enablement bundle from Freescale and ARM third party ecosystem partners The K60 MCU family includes IEEE 1588 Ethernet full and high speed USB 2 0 On The Go with device charge detect capability hardware encryption and tamper detection capabilities Devices start from 256 KB of flash in 100 pin LQFP packages extending up to 1 MB in a 256 pin MAPBGA package with a rich suite of analogue communication timing and control peripherals High memory density K60 family devices include an optional single precision floating point unit NAND flash controller and DRAM controller Freescale Tower System hardware development environment e Integrated development environments e Eclipse based CodeWarrior V10 x IDE and Processor Expert e AR Embedded Workbench e Keil MDK e CodeSourcery Sourcery G GNU e Runtime software and RTOS e Maths DSP and encryption libraries e Motor control libraries e Complimentary bootloaders USB Ethernet RF serial e Complimentary Freescale embedded GUI e Complimentary Freescale MQX e Cost effective NanoSSL NanoSSH for Freescale MQX RTOS 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 8 Freescale Semiconductor Inc _ _
48. peed PI controller setting trMyRamp s32RampDown Motor acceleration Can be set in rpm s trMyRamp s32RampUp Motor deceleration Can be set in rpm s 7 3 2 Web server control The MQX version of the application can be controlled through a web server The following setting must be done for a proper web server function 1 Disconnect the computer from any other network both wired and wireless Enable automatic IP configuration on your computer Turn off all proxy servers Connect the demo to the computer through an Ethernet cable Restart the Ethernet adapter Wait to establish a connection Write the IP address of the demo device into Internet Explorer The default IP address is 169 254 3 3 And then press enter NOTE The web server is optimized only for MS Internet Explorer 8 ZO UU DN 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 56 Freescale Semiconductor Inc Chapter 7 Sensorless BLDC Demo Operation Freescale MQX Webserver Internet Explorer provided by Microsoft Internet Explorer provided by Freescal kad GO gt E no 1c025433 8L0C htm 8 4 x 29 coogte ee File Edit View Favorites Tools Help Jer reescal le MOX Webserver l Ss 2 freescale semiconductor Webserver Home BLDC Motor Control Speed Ramp Setting Network Status Analog Data Sargraph Acceleration System Run Time RTC j ramp setting BLDC Control
49. phase s Back EMF The main characteristic is that the integrated area of the Back EMFs shown in Figure 4 6 is approximately the same at all speeds S1 S2 S3 The integration starts when the non fed phase s Back EMF crosses zero When the integrated value reaches a predefined threshold value which corresponds to a commutation point the phase current is commutated If a flux weakening operation is required current advance can be achieved by changing the threshold voltage The integration approach is less sensitive to switching noise and automatically adjusts for speed changes but low speed operation can be poor because of the error accumulation and offset voltage problems such as resistance precisions noise and so on In some ways this technique has a better performance than the standard BEMF zero crossing technique but is more difficult for the CPU bandwidth Therefore this technique is subjected to a higher performance CPU where the system application is not overloaded with other tasks This technique can also be optimized for high speed using some multisampling methods 4 6 Current Torque limitation Besides the speed control the drive has torque limitation In this mode the torque is limited to the desired value which can be adjusted by the trimmer on the TWRMCLV3PH board For overcurrent limit the MC33937 overcurrent output pin is used This output pin is periodically scanned in the PIT service routine If an overcurrent is
50. s are provided that allow a variety of algorithms to control 3 phase PMSM and BLDC motors The TWR MC LV3PH module features e Power supply voltage input of 12 24 V DC extended up to 50 V e Output current up to 8 A e Power supply reverse polarity protection circuitry e 3 phase bridge inverter 6 MOSFETs e 3 phase MOSFET gate driver with overcurrent and undervoltage protection e 3 phase and DC bus current sensing shunts e DC bus voltage sensing 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 31 TWR MC LV3PH e 3 phase Back EMF voltage sensing circuitry e Low voltage on board power supplies e Encoder Hall sensor sensing circuitry e Motor power and signal connectors e User LED power on LED 6 PWM LED diodes PWM LEDs Motor User LED Connector Motor Phases 6x PAMI 3 Phase MOSFET INT HBidge S A g il E E S fa Q ADC Sgnal Conditioning O O Sones anes S a S 3 Power m Supplies gt gt ta tao oO wT Analog Rower E Supply 3 3V O B Brake Control Driver amp MOSFET Figure 5 1 TWR MC LV3PH block diagram 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 32 Freescale Semiconductor Inc Chapter 5 Hardware MOSFET H Bridge Secondary Elevator Motor Connector Power Supply Connector Encoder HS Connector BEMF Currents Sensing Header Analogue Voltage Sel
51. st six commutation events Then the averaged commutation period is recalculated as the motor speed This process is executed every ms in the P TO_isr interrupt 6 1 4 Process standstill detection This process is used to measure time between two commutations If the time between commutations is higher than defined a standstill is detected It also detects time of standstill duration At any error the motor is stopped and the start up sequence is repeated When the standstill detection is enabled this process is executed every ms in the PITO_isr interrupt 6 1 5 Process commutation This process updates the variable observed_sector updates the PWM period and reconfigures the ADC and PDB modules for another phase measurement The PWM update based on the new commutation sector is performed in the Mask_Swap process The commutation process is called on every new commutation event So the execution period depends on the motor speed Commutation is processed only if no fault has occurred The flow chart of each service routine is shown in Figure 6 6 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 41 Introduction _Setup FTM OUTMASK _ ADC channel switch Figure 6 6 Commutation process 6 1 6 Process ramp Since the overall application is a system with large inertia it is necessary to profile the speed command when applying otherwise it could overload t
52. tem for motor control applications The MQX OS is suitable for large applications with advanced features such as web control USB displays and SDHC card reading running on a dedicated device usually one core The primary strength of MQX is that it includes libraries for RTCS Ethernet USB communication the MFS file system and many other applications 3 3 How to implement motor control and MQX The MQX RTOS is a complex system with dynamic allocations and POSIX scheduling It has a system default tick duration of 5 ms This is ideal for the majority of applications However this also means that the MQX task time resolution is more than 1000 times longer when compared to the motor control requirements Therefore it is evident that the motor control process needs to be serviced with interrupts of a high priority This can be provided with standard MQX interrupt routines The time duration from the interrupt request to the service routines execution is usually units of a microsecond depending on the CPU version and clock speed And if necessary the motor control algorithms can be 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 19 How to implement motor control and MQX implemented using the kernel interrupts The kernel interrupts are natural CPU interrupts with no MQX overhead and minimal execution duration The disadvantage of the kernel interrupt is that no MQX functiona
53. terface For a correct Free MASTER operation follow the given steps 1 Open Free MASTER and go to Project Options Comm and set communication via to the Direct RS232 2 Select the COM port where the TWR SERIAL is connected see System Properties Device Manager Ports The communication speed is 19200 Bd 3 The next step is to toggle the communication button After that in the bottom right hand corner there should be RS232 COMxx 19200 which means that communication has been established 4 If not toggle STOP the communication and unplug plug the FreeMASTER USB cable Then toggle START the communication button Detailed information about the set up can be found in the user guide BLDCSLK60UG available at http www freescale com 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 54 Freescale Semiconductor Inc Chapter 7 Sensorless BLDC Demo Operation After launching the application and performing all necessary settings click the scope BLDC item in the project tree structure of the FreeMASTER application window as shown in Figure 7 1 In this view variables used for the application state speed PI controller and ramp settings are visible For the demonstration purposes this is sufficient F TWR_BLDC_BM pmp FreeMASTER E 2181 xi File Edit View Scope Item Project Tools Help SRO ala 29 01 215 2212 12 18 fin 214 se Es BLDC_EXAMPLE emy Say a R pl Measur
54. terfaces between a computer system and the external world a CPU reads an input to sense the level of an external signal and writes to an output to change the level of an external signal ISR Interrupt Service Routine PK60N512 Freescale 32 bit ARM based microcontroller MCU Microcontroller PDB Programmable delay block module POSIX Portable Operating System Interface produced by IEEE and standardized by ANSI and ISO MQX conforms to POSIX 4 real time extensions and POSIX 4a threads extensions PWM Pulse width modulation RPM Revolutions per minute RTOS Real Time Operating System RTCS Embedded Internet stack provides IP networking for the MQX platform RTCS is provided with a rich assortment of TCP IP networking application protocols and uses the MQX RTOS drivers for Ethernet or serial connectivity SCI Serial communication interface module a module that supports asynchronous communication SPI Serial peripheral interface module 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 66 Freescale Semiconductor Inc How to Reach Us Home Page www freescale com Web Support http www freescale com support USA Europe or Locations Not Listed Freescale Semiconductor Technical Information Center EL516 2100 East Elliot Road Tempe Arizona 85284 1 800 521 6274 or 1 480 768 2130 www freescale com support Europe Middle East and A
55. ve long word is 7FFFFFFF or 1 0 2 31 The following equation shows the relationship between a real and a fractional representation eerie Real Value ractional Value gt Quatity Range Fractional Value Fractional representation of speed quantities Real Value Real speed quantities in physical units rpm Real Quantity Range Max defined speed used for scaling in physical units rpm In this application the scale constant is calculated by this equation e 60 6 60 NST pg x 39 13500 SCALE CONST MAX SCALED_SPEED ppTPM_P 5000 128 TPM_C 48000000 The following macro is used to compute the speed scale SCALE CONST tFrac32 6 60 PP TPM_P TPM_C MAX _SCALED SPEED 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 50 Freescale Semiconductor Inc y Chapter 6 Software Design PP Number of pole pairs of the motor used Default value is 2 TPM_C Input clock of the timer in Hz Default value is 48e6 TPM_P Prescaler of the timer input clock Default value is 128 MAX_SCALED_SPEED Maximal speed with reserve Default value is 5000 As you can see from the previous equation this scale constant is multiplied by 6 This is done for the average compute The time_measured variable is used to store the sum of 6 time intervals for int g 1 g lt 7 g time_measured time_measured period g Then there is no need to divide the sum of the time int
56. ween the top and bottom switches to avoid any phase short circuit The complementary switching can be implemented in both a bipolar or unipolar manner The unipolar switching leads to lower switching losses and current ripple However from a Back EMF point of view the bipolar switching is a better choice since this allows having a duty cycle in the range of 50 100 This significantly simplifies the Back EMF voltage and current sensing The complementary bipolar switching is selected for this sensorless BLDC drive because of easy implementation of the Back EMF voltage sensing method and the Kinetis K60 features point of view The details of the Back EMF voltage sensing method can be seen in ADC to PWM synchronization 4 3 ADC to PWM synchronization The power stage PWM switching causes voltage spikes on the phase voltages These voltage spikes are generated on the non fed phase because of mutual inductances and mutual capacitor couplings between the motor windings Non fed phase branch voltage is then disturbed by PWM switching Figure 4 2 and Figure 4 3 show the effect on the non fed phase because of the mutual inductance 3 Phase BLDC Sensorless Control with MQX RTOS Using the K60N512 Rev 0 06 2012 Freescale Semiconductor Inc 23 ADC to PWM synchronization nk l lll ii 00v a 5 00v 400us 2 50GS s O 7 11 7v 91 10 20M points D15 DO Timing Resolution 2 00ns 1 Mar 2012 23 49 08 Figure 4 2 BEMF voltage spikes an
57. ypical parameters that may be provided in Freescale Semiconductor data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Freescale Semiconductor does not convey any license under its patent rights nor the rights of others Freescale Semiconductor products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which failure of the Freescale Semiconductor product could create a situation where personal injury or death may occur Should Buyer purchase or use Freescale Semiconductor products for any such unintended or unauthorized application Buyer shall indemnify Freescale Semiconductor and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claims alleges that Freescale Semiconductor was negligent regarding the design or manufacture of the part RoHS compliant and or Pb free versions of Freescale products have the functionality and electrical characteristics as their no
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