Puma/Cougar Implementor`s Guide
Contents
1. return packet operation unless the form manip dont return pkt packet is used The background process docs not expect any return value from the handler When the background process looks for a handler for a response packet it looks at the manip response type list for the response handler types and uses the first handler it can find by looking down that list 10 5 PROCESSES Thus the order of the types matters Furthermore a handler may allow handlers defined by other types to participate in the handling of the response by calling the form manip continue manipulator response handler manipulator packet queue Note that the handler functions which are defined by the Manip system simply send a message to the manipulator with the name io handle all of which are combined using OR method combination Thus it would be quite simple to slightly modify the handling of these responses by suitably defining methods in the appropriate mixin The handling of responses may be further customized or radically altered by suitable definition of over riding methods for the io handle packet or io handle response code messages See the code The following are a few functions which the implementor may find useful in implementing responses All are in the MANIP package For details see the code find matching request response packet string signal error for request signal error for request 1 signal error for out of sequence request 4 Puma Speci2. the addresses and vectors of the various interrupt driven routines it initializes the DRV 11J and the clock and prints a wake up message on the terminal if one is connected to port 0 of the MXV 11AA It then sets a low priority in the processor and jumps to JACOB B 2 JACOB The Jacobian routine JACOB runs continuously subject to interruption from any of the interrupt driven processes The MACRO 11 code which actually executes the Jacobian calculation is produced by a micro compiler written in lisp JACL LISP This compiler operates on code modified somewhat from a Jacobian routine originally written in Pascal The transpose of the Jacobian is stored explicitly immediately following the Jacobian B 3 JMOVE Jmove repositions the Jacobian and its transpose For historical reasons the Jacobian is computed in the region labeled J then moved to either jtmp1 or jtmp2 B 4 ADC8 23 B 4 ADC8 ADC3 at once acquires and filters force data from the wrist For each of eight channels it initiates a conversion waits for completion and processes the result according to the formula Y uz ur 1 6Y4 1 8 Where Y is the kth output value ux is the kth force sample uz is the previous sample and Y is the previous output value The equation is implemented in such a way that floating point operations are not required The arithmetic is done with shifts and adds When the servo rate is 60 Hz a cutoff of 2 8 Hz is obtained in the force infor
3. CSR 170420 2 VEC 440 Slot 4 right DRV 11C compatible 16 bit parallel line interface This interface once was the connection to Cougar but now is used for finger data Currently it is unconnected CSR 167760 3 VEC 210 Slot 4 left DRV 11C 16 bit parallel line interface The interface to the Unimation controller box CSR 167770 3 VEC 200 Slot 5 left DRV 11J fancy 16 bit parallel line interface Connection to Cougar Ports C and D are used to communicate to Cougar Some places in the code use port A for metering flipping bits for an oscilloscope otherwise ports A and B are free CSR 164160 8 VEC programmable 220 port C 224 port D 26 Name Label NOP noop WINIT noop SEN noop FINIT noop NPR newpr NFC noop NK newk NB newb NBJI newbji NFV newfv RST resetw DPST dep EXMN exp VERS verson RFRC rfrc NEWEWC newewc GUARDS guards GUARDC guardc RRAW reraw WGOV noop Puma Request Code Data Cougar Response Code Data 6 fvec 6 fvec 36 fmat 6 fvec 3 fvec none none 2 words none 2 words gt 2 words none wt 1 frum cg 3 fvec type index dvec 6 fvec tol 1 fnum index none 8 vec D PUMA HARDWARE COMPONENTS No operation Useful for recovering from synchronization errors Wrist Init an obsolete command Theta Sensed Tells the wrist where the arm is so that grav
4. Unimation Controller New joint angle commands to the Unimation controller every sixteen milliseconds Motion completed Figure 4 Example timeline for a Set Joint Angles request A move request 16 6 EXAMPLES Puma 11 Unimation LispM Main proc Moveproc Controller Set Joint Angles Send a bad motion request Another request Error Joint out of range Panic button pressed N Error No Arm Arm Power off Power Error forwarded to user Motion aborted Figure 5 Example timeline for the Set Joint Angles request in the presence of an error 6 4 Compliance 17 Puma 11 LispM Main proc Wrist Output Wrist Input Cougar Read Forces request Sensed Angles Read forces Commands Waits for data Force data Response Figure 6 Example timeline for a Read Forces request for the force data It then waits for the data to be returned The wrist output process notices the queues requests and forwards them to Cougar through the parallel interface interrupt ring buffers When Cougar responds with the current forces and torques the wrist input process fields the response stores the data into the buffer supplied by the main process and notifies the main process that the data has arrived The main process then reawakens and forwards the data hack to the user in a response packet If Cougar should not respond within a reasonable amount of time the main process
5. bit floating point number it should be in the range 0 lt n lt 1 Simple response Opcode 217 Enable high power No data Enables arm power if arm power has to be enabled to work Simple response Opcode 220 Solve forwards Data are a transform and then a set of joint angles The joint angles are taken to be the current joint angles if the solution code cares about them The solution is done and a set of six joint angles are returned Opcode 221 Solve backwards Data are six joint angles A transformation is returned This is mostly useful for debugging the backwards solution code Opcodes 250 277 are reserved for nongeneral arm specific operations Note Currently the Puma uses opcodes 240 and up for some Puma specific codes This will be fixed in the future E 2 Server Responses Packets from the server to the Lisp Machine fall into two categories responses and errors Responses contain an opcode the Chaos packet opcode possibly followed by the data for the response The particular data i defined by the reponse and by the request it is a response for All server error messages must conform to a simple format The body of the response after the request number must contain an ascii string The string will contain ascii characters possibly followed by a null and a sequence of 16 bit numbers The ascii message must look as follows where severity code message The where should be a short indication of where in the se
6. giving position information representing a 3 x 4 matrix as in opcode 201 here The manipulator moves to the specified position using joint interpolated motion The response is a done The single word in the data section of the response is the segment number Opcode 205 Straight line move The data are 12 PDP 11 style floating point numbers giving posi tion information representing a 3 x 4 matrix as in opcode 201 here The manipulator moves to the specified position using straight line motion produced by interpolation between the current position and the destination position The response is a done The single word in the data section of the response is the segment number Opcode 206 Kill power There is no data section Arm power is killed The response is a done and is also empty Opcode 207 Set configuration The data section is handled per arm on the Puma it is one byte long with the low bit a 1 for lefty and a 0 for righty The response is a done and is also empty Actually on the Puma it is currently unimplemented and the definition will probably change when it is finally implemented Opcode 210 Open or close hand The datum is a single 16 bit number representing the amount to close or open the hand On a binary hand a value of 0 means to close the hand and any other value means to open the hand The response is a done with no data Opcode 211 Incremental move The dat
7. manual Request packets are sent to the manipulator controller by the background process The interface to the specific communication protocol used for communcation e g Chaosnet is provided by the flavor instance See below for more information Response packets and errors are received by the background process using the flavor instance for instruc tions on dealing with the communications protocol and are handled according to what handlers are defined for the specific manipulator protocol in use Errors too can be handled and signalled by the background process according to the descriptions provided in the Puma protocol sce below and the users manual Sce the Puma users manual for information on the structure and implementation of homogeneous trans forms aud transform like objects 3 Defining a new protocol The Manip system is extremely flexible The background process is controlled by the flavor instance it is serving In particular whenever the background process attempts to communicate with the actual manipu lator server it does so by sending a message to the manipulator flavor instance Thus the exact operation performed may be controlled by suitably defining or redefining the method handling that message The Manip system is designed to support directly any protocol satsifying the following characteristics e For each request packet sent from the lisp machine to the manipulator controller a reply is sent back The reply may co
8. number of data words If the buffer is non empty COMINT checks the first word in a look up table to see how much data this command requires On finding at least that many words in the buffer COMINT removes the command from the buffer and transfers its data to a location also found from a table Finally COMINT calls the subroutine which will execute this particular command When it terminates COMINT looks for more complete commands in the buffer If none are found COMINT returns All available commands are listed in Table t If COMINT detects an unrecognized code word it takes drastic action It assumes that it has lost sync with Puma and so dumps the input buffer and sends an out of sync message to Puma B 8 GRAVTY At any instant the forces reported by the wrist will be the sum of gravitational and contact forces operating on the hand Compliant motion strategies require that the robot respond to contact forces so it is convenient to remove the component of force due to gravity This the GRAVTY routine docs by keeping track of the orientation of the hand and subtracting from the measured force the part for which gravity is responsible The gravity correction code uscs a simple model of the hand and the object it holds to compute the expected forces Each is modeled as a point mass at some position in the frame specified by the frame vector Whenever a new object is picked up or the frame vector is changed NEWEWC must be called to record the weight
9. ss 0 0 eo 4 oo lt o e 0 lt o 0 o 0 0 CONTENTS Force Sensing Wrist Lisp Machine Chaos Net Puma System Connections Figure 1 Block diagram of the Puma control system Part I The Lisp Puma System 1 Basic structure The Puma system is really a combination of two systems the Manip system and the Puma system The Manip system provides a generic interface to almost any type of manipulator The Puma system provides a small amount of customization to the Manip system for specifics of the Unimation Puma arm Most of this part of the document describes the Manip system in general The Manip system is comprised of a set of mixin flavors which describe the Lisp object representing the actual manipulator These flavors may be combined to provide just the functionality necessary to run a specific manipulator The pre defined flavors will be described presently The intermediary between the user and the manipulator is a background process that forwards requests from the user to the manipulator and fields responses from the manipulator Exactly how the communication with the manipulator takes place is controlled by the flavors Information as to the disposition of each request is stored in a request object q v which is passed to the b
10. to the underlying communications The packet should be returned to a resource or whatever If no manual memory management is used or necessary this operation may do nothing The packet is this operation s only argument response available Should return T if and only if there is a connection to the manipulator controller and there are data packets available to be read connection open Returns true if and only if there is an open connection to the manipulator controller shandle closed connection This operation is called with no arguments when the background process detects the connection to the manipulator controller has been closed for whatever reason This operation may do whatever it needs to clean up Also as in the case of manip network protocol mixin the user may be notified of the connection loss and the reason if such can be determined send user request This operation is given one argument the request structure It is responsible for mak ing a packet go out over the communications link to the manipulator controller It is also responsible for setting the request packet number slot of the request structure This is the sequence number which is compared to the value in the response The request opcode and request data may be found in the appropriate slots of the request structure get response info When given a response packet from the manipulator controller this operation returns values which allow the data extractor o
11. two chronic maladies drift and offset Simply reading the raw data from the wrist with no force applied including gravity would not result in a value of 0 from each of the strain gauges The non zero values one reads in the absence of forces are the gauge offsets Also taking the same reading on different days would produce different values this is the drift To correct for the offset an eight element vector is subtracted from the gauge readings prior to any other processing Unfortunately because of drift this value cannot simply be stored in Cougar for all time but must be recomputed periodically This is the purpose of the Calibrate Wrist command It computes a gauge offset by reading the wrist force sensor in two positions to compensate for gravity 8 4 Data Transfer If IDXS the interrupt driven transfer send routine is running then each time Puma receives a character it sends a control signal back to Cougar which causes and interrupt that initiates the sending of the next character If however the routine is not running it will never get an interrupt to start a new transfer this would mean that characters for transfer would pile up in the output buffer It is necessary then to turn on 8 4 Data Transfer 21 IDXS whenever data needs to be sent But this must not be done blindly if IDXS is restarted when it is already running i e las just sent a character and is waiting for an interrupt then it would send the next character befo
12. which may be set 7 4 Communication Certain commands can be passed between Puma and Cougar The data which constitutes these commands travels between the DRV 11J cards in the two computers Interrupt driven routines which trigger on the completion of the previous transfer send and receive data words Buffers are used to hold data going in each direction As a part of the main Puma triggered interrupt routine the input buffer is checked for complete commands which are executed as they are found 20 8 COMPLICATIONS 7 5 Utility Many subprograms serve as utility routines These include in particular the routines in the math package 8 Complications Not all of the Cougar system operates in as straight forward a manner as would be desired This sections outlines some of the difficulties 8 1 Intermediate Values The Jacobian its transpose and several intermediate values for the compliance equation are computed by a background operation As they are used by an interrupt driven routine we must guard against the possibility that they will be referenced when only partially computed This is accomplished by keeping two versions of each object one for the background and one for the foreground process When the background process finishes each computation it switches the pointers which define background and foreground for that object 8 2 Wrist Data The RTI force sensing wrist provides analog data in the range of 10 to 10 volts This
13. will give up and return a non fatal error message to the foreign host 6 4 Compliance Not surprisingly compliant motion causes the most interaction between the various components of the system The main process treats a compliant motion request as it docs any other motion request It copies the desired joint angles into a move packet along with the compliant move interpolation vector and queues it to the move process The move process too treats compliant motion segments no differently than normal motion When the segment s turn comes up it dispatches through the move interpolation vector to initialize the segment interpolate to the desired position and clean up after the segment The interpolation routine for compliant motion however does more In the course of calculating the set of joint angles for the next servo period it calls the normal motion interpolation routine to determine the nominal position but then involves the two wrist processes and Cougar On each servo cycle the compliance interpolation routine causes a New Position and Rate command to be sent to Cougar It will do this itself if the wrist output process is quiescent or will sct the flag to inform that process that it needs to be done The command is sent to Cougar who then calculates and returns 18 6 EXAMPLES Puma 11 i Unimation LispM Main proc Move proc Wrist I O Cougar Controller Response E Joint angles second cycle y m lt eee
14. DR These are the Interrupt Driven Routines They now include only the data send and receive routines IDXS and IDXR B 12 RATEO RATEO does nothing more than to put the newly computed compliance rates into the buffer from which they will be sent to Puma B 13 NEWPR The most important command the one executed every cycle during compliant motions is NEWPR It gets from Puma the currently sensed and commanded position and the difference between sensed and commanded rate and computes an incremental velocity to send to back to Puma The equation it implements is the compliance equation discussed in section 1 B 14 NEWFV Newfv which stands for New Frame Vector changes the compliance center to the point specified in hand coordinates It can only cause a translation It forces a recomputation of the strain gauge calibration matrix as explained in the Complications section and causes the model of hand object combination in GRAVTY to be redone B 15 MISCOM The routines in the file MISCOM execute miscellaneous commands which are explained below in the Remarks column of the Command Protocol section B 16 MATH 25 B 16 MATH The MATH file holds numerous mathematical routines In particular it has routines for vector and matrix multiplication and routines for finding sine and cosine B 17 END End contains the Palx statement end without which the assembler would complain C Command Protocol Table 1 gives the protocol for passi
15. DRV 11J programmable 240 PIRQ not handled 244 Floating point exception 250 Memory management not handled 270 274 Chaosnet interface 300 304 Teach box serial line MXV 11 line 0 440 444 Real time clock KWV 11C Aia Table 3 Known nsed interrupt vector addresses This also includes trap addresses for completeness o brand name is a Lisp Machine Lisp readable string i e delimited by double quotes etc that contains the name of the manipulator E g Unimation Puma 600 Purbrick Arm Salisbury Hand Finger 1 l y sunique name is like BRAND NAME but should be a unique identifier of the robot Thus if the AI Lab had two Puma 600s their UNIQUE NAMEs might be Puma 600 1 and Puma 600 2 or Trurl and Foo degrees of freedom should be an octal number giving the number of degrees of freedom of the manipulator Examples the Puma returns 6 for this so would the Purbrick arm operations Should be a list of opcodes supported by the server An opcode is normally an octal number e g 200 In the case of escape codes an opcode can be a dotted pair e g 277 0 software version is manipulator dependent It should be either a number indicating the version of software being run on the server host or a list of alternating keyword and version number pairs For instance the keywords may indicate the module name and the version number would indicate the version of that module pro
16. MPLY PALX Calibration routines are in CALINF PALX 5 1 The Main Process When a request for connection is received by the Puma 11 the main server process is created and started The process initializes the Unimation hardware sets up the software database creates the ancillary processes and enters a loop waiting for request packets from the foreign host When a request packet is received the process dispatches to the appropriate handler routine for the request performs whatever actions are necessary to satisfy the request then sends a response packet to the foreign host If a condition arises or is discovered which prevents successful completion of the request the response will be indicate an error The main process is also responsible for reporting error conditions discovered by the remaining three processes it is the only process which actually communicates to the network The ancillary processes store error information in a buffer which is checked each time through the main loop Any errors which are found there are passed on to the the foreign host If the connection is closed cither by the foreign host or by a fatal error condition the main process shuts down the system It informs the two wrist processes that they should log themsclves out turns off clock interrupts which effectively shuts down the move process makes sure the connection is closed and released to the Minits Chaosnet code then logs itself out When a request is
17. Massachusetts Institute of Technology Artificial Intelligence Laboratory Working Paper 272 April 1985 Puma Cougar Implementor s Guide Joe L Jones Patrick A O Donnell This document is intended to be a guide to assist a programmer in modifying or extending the Lisp Puma system the Puma PDP 11 system or the Cougar PDP 11 system It consists mostly of short descriptions or hints and is not intended to be a polished manual The reader is expected to be familiar with the use of the Puma system as described in Using the PUMA System and the Lisp flavor system as described in the Lisp Machine Manual A I Laboratory Working Papers are produced for internal circulation and may contain infermaiton that is for example too preliminary or too detailed for formal publication It is not intended that reference be made to them in the literature 2 CONTENTS Contents I The Lisp Puma System 5 1 Basic structure 5 1 1 File Organization A GE ae a A S 5 1 2 Flavors sci od en ea es a A A ei 5 2 Purpose 6 3 Defining a new protocol 7 3 1 Implementing a protocol 6 ee ete ees 7 3 2 Implementing new Request Response codes o o ooo ooo o 9 4 Puma Specifics 10 II Puma PDP 11 System 10 5 Processes 10 5 1 Whe Main Process susa airaa a A A ERE eee a a 12 5 2 The Move Proc ss o ows es i sitie a ae a a OR He eae 12 5 3 The Wrist processes s e nia ia i Kaon aTa n E a ee ee ees pane 19 6 Examples 13 6 1 A
18. Move packet Beginning q irst cycle Esa NewPR NewT Dle ee third cycle _ lt A Figure 7 Example timeline for a Comply request Note This diagram assumes that the Wrist output process is quiescent when the move process whishes to transmit New Position and Rate requests to Cougar Tf the output process should be in the midst of transmitting data the NewPR requests would first go the the output process then on to Cougar 19 the next velocity modification The input process receives the New Theta Dot command and stores the data in a buffer from which the interpolation routine will use them This interaction takes time however it takes longer than the servo rate Thus on the same cycle that the interpolation sends a NEWPR command it uses NEWTD data from a previous cycle the latest that Cougar has sent This interaction continues to occur for each servo cycle until the motion is complete at which time the normal clean up handling takes place and a new segment is started or the arm brought to a smooth stop Note also that while the compliance is taking place other interactions may be taking place between the user and Cougar involving the wrist input and output processes Part III Cougar PDP 11 System 7 Overview of Cougar Software The routines running in Cougar can be roughly divided into five classifications They are the background task a data acquisition module a data processing module a communica
19. a are six floating point numbers representing dX dY dZ dO dA and dT where O A and T are pseudo Euler angles as described in VALOAT these are the Euler angles used by Unimation The manipulator moves to the new position using joint interpolated motion The response is a done The single word in the data section of the response is the segment number Opcode 212 Incremental straight line move The data are six floating point numbers representing dX dY dZ dO dA and dT The manipulator moves along a straight line to the new position and terminal device orientation The response is a done The single word in the data section of the response is the segment number Opcode 213 Free joint The first byte in the packet contains a number 1 based thus joint numbers on the Puma range from 1 to 6 not from 0 to 5 giving the joint to free The manipulator controller will then await another packet Upon receiving one it will un free the joint and discard the packet Opcode 214 Move to ready position Empty data section Manipulator moves to ready position pointing straight up The single word in the data section of the response is the segment number 30 E THE CHAOS MANIPULATOR PROTOCOL Opcode 215 Set joint angles The data are 6 floating point numbers representing desired joint angles The single word in the data section of the response is the segment number Opcode 216 Set speed factor The datum is a single 32
20. ackground process through a queue stored in the flavor instance corresponding to the manipulator 1 1 File Organization The Manipulator system is divided into several files all of which are accessed on the manip logical host directory source as in manip source defs lisp defs Contains the main definitions of the macros and flavors used throughout the Manip system Includes the definitions of the Request Defstruct Manipulator Request Codes and Manipulator Response Codes errors Contains the definitions of the error flavors and error functions used in the Manip system Also contains the definitions of the special forms used to handle manipulator non fatal errors in a user process math Contains the definition of transforms and a few other random mathematical operations useful for manipulators or the protocol bekgnd This file contains the definition of the background process and the basic communication protocol This is the fundamental definition of the protocol network This short file contains the definition of the flavor mixin used to communicate with a maniuplator over the Chaosnet It serves as an example for other possible implementations user The default implementations of user operations on the Manipulator flavor instance This includes such operations as request initialize disconnect move here etc utils Contains various debugging utilities 1 2 Flavors The defined flavors and their purposes ar
21. and center of gravity vector of that object 24 B COMPONENTS OF THE COUGAR SOFTWARE B 9 GUARD Two types of guards are allowed The first type instructs Puma to stop moving immediately The second just informs Puma that a guard has tripped In either case Cougar reports the number of the guard which tripped That guard then becomes inactive and will not trip again unless another GUARDS command is issued The high byte of the first data word in the GUARDS command determines which type of guard is activated A maximum of 16 guards may be active at any time The number of the guard to activate occupics the low 4 bits of the first data word The Lisp Machine must keep track of which guards are in use and provide a number when the user wants to activate a new one The guard code uses the gravitationally corrected sensed forces to decide if a trip has occurred so the NEWFV and NEWEWC commands should not be used while a guard is active B 10 FILTER FILTER is an output routine which smoothes the output It computes a weighted sum of the derivative and integral of the controlled quantity using the formulas AO Filtered con AB sample Ab Previous Sample cong Ab Fitered Adoutput cong AO Filtered cong Ab Sample Where con 2 aT 2 cong aT 2 aT 2 T Sample Period a cutoff frequency and a lt 1 2T The constants cons and con determine the relative importance of the raw quantity and the filtered quantity B 11 I
22. angles together with the desired interpolation scheme are stored in a move packet and queued to the move process The main process now responds to the user with a motion segment sequence number As far as it is concerned handling of the request is completed 14 6 EXAMPLES LispM Puma 11 Here Request Calculate transform from current joint angles Transform response Figure 3 Example timeline for the Here request The move process notices the new packet on its queue and begins processing the segment Based on the interpolation type the process dispatches to an initialization routine which may set up the interrupt processes global database to handle the interpolation from the arm s current position to the desired position from the move packet Then on each servo cycle new intermediate joint angles are calculated by the interrupt service routine and sent to the Unimation controller This will continue until the arm reaches the desired position The move packct is then returned to free storage the handling of the original request is complete Let us here consider the effect of error conditions on the above behavior First assume one or more of the joint angles requested by the foreign host are out of range This would be detected by the main process before queueing the move packet Instead of a normal response the user would receive a non fatal error message _ Now let us assume that the angles are valid and the a
23. e It also attempts to provide a unified interface to a manipulator object which would allow a single program to be useable with many different manipulators with possibly only calibration differences The Manip system meets this purpose by providing the following e A request structure that can be used in common among different types of manipulators and which contains instructions for transmitting the request and associated data to the manipulator controller and for retrieving any response data e The code necessary to transmit the request packet to the controller e The handlers for dealing with response packets o Handlers and support functions for dealing with errors both as signalled by the manipulator controller and as encountered in the Manip system itself e Functions and data structures for dealing with homogeneous transformations A set of common operations on a manipulator object Request structures can be created and used by the user program under control of the manipulator flavor instance using the make request send request and request operations and it is through these operations that the user program communicates with the background process its desire to send such requests to the manipulator controller The request is also used for communication between the background process and the user program for the purposes of crror handling and retrieving data from the responses For more details on requests see the Puma user
24. e as follows all symbols in the manipulator package basic manipulator The minimum it takes to be a manipulator This defines some of the primitive opera tions such as move here etc 6 2 PURPOSE basic protocol mixin This defines how the background process behaves It is controlled through the methods io process top level loop for the top level processing and dispatching io handle packet for handling each incoming packet io handle response data called by the handle packet method for a normal response and io handle request interrupt for handling the request interrupt feature of a request see the users manual It also defines how requests are created and processed through make request send request and request network protocol mixin This defines the interface between the background process and the communi cation medium for the Chaosnet It or a mixin like it controls the background process through the methods described below in the section Defining a new protocol notify trivial errors mixin This flavor supplies some control on how some so called trivial errors are handled See the code for more details 2 Purpose The basic purpose of the Manip system is to provide a convenient interface between the Lisp environment and a non Lisp Machine manipulator controller This allows high level computations to be performed on the Lisp Machine and the low level control of the manipulator on another machin
25. eclares the symbol to be a name for the given opcode Then when sending a request via the request operation using the symbol will cause the request to have the specified opcode The interpretation of the request data will be the same regardless of the opcode unless the send user request message whose responsibility it is to create and send the communication packet see previous section makes some differentiation The manip define manipulator request code form also takes a couple optional arguments The first optional argument should be a symbol refering to the type of manipulator which implements this opera tion An example would be puma for the special compliance operations implemented by that manipulator controller If the argument is not specified or NIL then the request code is a generic code common to manipulators This manipulator type is used in this context mainly to select an appropriate symbol when given an opcode This is mostly used for printing things for the user The second optional argument should be a keyword which describes the default data extractor function to use if none is specified when the request is created Sce the code for what keywords are defined and how to define new ones Creating new response codes is almost as trivial First a symbolic name for the response code must be declared using manip define manipulator response code symbol code analagous to manip define manipulator request code There a
26. fics There is very little that is really specific to the puma except for certain customizations of various operations and compliance All the compliance operations are specific to the Puma but they mostly consist of merely passing matrices and information to the wrist 11 through the Puma 11 Part II Puma PDP 11 System This part is a brief overview of the control system running in the Puma PDP 11 23 It is intended as an introduction for prospective programmers to become acquainted with the overall structure of the system More detailed information is available in the comments in the actual code This document assumes that the reader is familiar with the structure of the network protocol used to communicate with the Puma 5 Processes The system is built on the Minits operating system Minits provides a handy facility for very simply configuring a PDP 11 system with various hardware components Of interest to the Puma system is the Chaosnet support and Minits multiprocessing capabilities Minits has a rather simple scheduler which selects a process to run based roughly on a priority using a round robin selection between processes with the same priority The Puma system runs in four separate pro cesses a main process which communicates with the foreign host over the network and handles its requests and three ancillary processes Two processes communicate with Cougar the wrist PDP 11 one handling data transmitted from Cougar and one se
27. hat does not close the connection The packet contains the error string This is sent only in response to a request This serves as the response to the request asynchronous error Opcode 4 This is just like non fatal error but is sent because of a condition arising not directly in the processing of a request The defined data extractor functions may be found in the BCKGND file just after the comment Define a few useful data extractor functions along with the contract they or new ones must fulfill The next section provides the details of implementing a new protocol using the same response codes as the Puma protocol A later section will detail how to implement new response handlers 3 1 Implementing a protocol To implement a new communications protocol there are just a few methods that need to be provided by a mixin flavor to manip basic manipulator See the file NETWORK for an example implementation of the communication protocol may transmit This operation takes no arguments and returns non NIL if it is safe or reasonable to transmit a packet to the manipulator controller This is used to allow the underlying communcations to implement a flow control scheme and not let the background process get caught in a deadlock 8 3 DEFINING A NEW PROTOCOL sget next packet Returns the next packet from the manipulator controller Returns NIL if none return packet This operation allows the background process to hand a used packet back
28. ia the two wrist processes Each servo cycle it requests the output wrist process to send a New Position and Rate command to Cougar The input wrist process will accept New Theta Dot commands from Cougar and will store the velocity modifications in a buffer from which the compliant interpolation scheme will accept the information to use in its calculations See the code for more details 5 3 The Wrist processes The two wrist processes handle all communication with Cougar One process handles commands and data to be sent to Cougar and the other accepts commands and data from Cougar and interprets them There are two types of command which may be passed between Puma and Cougar commands directly associated with servoing the arm under compliance and commands in response to user requests Of the former examples are the New Position and Rate Reset Wrist and New Theta Dot commands of the latter examples are Read Forces Sct Wrist Gauge Offsets and Force Data Processing the commands associated with the servo loop is optimized for better response time from Cougar Unlike user requests which are queued as packets to be sent to Cougar move process requests are queued merely by setting a bit in the wrist process tlag word These flag bits receive higher priority handling than mere user requests Further if the wrist output process is quicscent the interrupt routine itself will put the data i
29. is converted by the ADC to a 12 bit range The data thus presented however is not the force nor is it directly interpretable as a voltage it is just a set of cight numbers one for each strain gauge with values between 2048 and 2047 To get the force information these must be converted by applying the wrist s calibration matrix In order to avoid a multiplication each servo cycle the calibration matrix is premultiplied by a conversion constant 10 2048 which by itself would convert the gauge readings into values in the range of 10 to 10 But this is not all For compliant motion it should seem to the robot that any force read from the sensor are forces which 1t has applied rather than forces applied to it To achieve this we further multiply the calibration matrix by 1 And finally we want the capability to choose the center of compliance to have the forces reported and used by the system be the forces that it would read directly if the wrist was at the center of compliance This requires another transformation matrix which is multiplied into the previous one It turns out that only certain of the elements of this final matrix depend on the position of the compliance center so rather than actually perform another matrix multiplication the proper elements are modified individually This is done automatically cach time the frame vector the position of the center of compliance is changed 8 3 Drift and Offset The force sensing wrist suffers from
30. ity compensation will work even while compliance is inactive Full Init data is sensed position an obso lete command New Position and Rate Gives sensed and commanded position and the difference of the sensed and commanded rate Response is AO New Force Commanded New Spring Constant a matrix of diagonal terms only New Damping Matrix a 36 element matrix New Joint Damping Matrix Inverse diag onal terms only New Frame Vector a vector offset from the intersection of joints 4 5 and 6 This defines the center of compliance Reset Wrist set all velocities to zero Deposit deposits the second word into the location specified by the first word Examine start at first word return sec ond word number of words Response first word number of words retrieved rest data words Version Number intended to ensure con sistency between Cougar and Puma it is not currently used by either side Report Forces report most recent sensed force from wrist New Effective Weight and Center of Gravity The cg is the offset from the frame vector Weight of object in ounces Guard Set ist word hi bit set gt trip stops move response 6 Clear gt con tinue move response 7 dvec vector to dot with force tol scalar to test index number of guard Guard Clear Ignore guard specified by in dex Read Raw Wrist Gauges returns readings from each of the 8 wrist strain gauge
31. mation It would be possible to operate the ADC on an interrupt driven basis but as the conversion delay is a minor part of the total computation time this has not been done B 5 LIMIT To promote stability LIMIT puts bounds on the minimum and maximum forces to which the system is sensitive Any force torques below an absolute value of 5 oz 5 oz in are set to 0 and any above 500 oz 500 oz in are set to 500 These limits are easily changed by altering the tol or dead constants in LIMIT At present the LIMIT code while available in the system is not actually used B 6 GUTS When Puma s clock ticks the interrupt routine GUTS is called in Cougar GUTS in turn calls ADC8 to get the filtered strain gauge readings converts them to floating point and multiplies by voltmat to get the forces Subsequently GUTS calls GRAVTY to make the gravitational correction calls GUARDM to check for tripped guards and calls COMINT to process any commands that may be in the input buffer GUTS is non reentrant and so must never interrupt itself This condition is checked for on entry into GUTS and if detected a character is sent to the terminal and a return from interrupt instruction is executed B 7 COMINT As data is transferred from Puma to Cougar it is stored in an input buffer When COMINT is called it examines that buffer to see if any data is there Commands consist of a code word unique to the particular command followed by some characteristic
32. n the outgoing ring buffer This saves process switching time and the associated latentcy The move process also briefly handles some user requests those which must be synchronized with move segments These requests are queued by the move interrupt routine for the wrist output process to send to the wrist A separate queue is kept for requests coming directly from the user through the main process The priority order for dealing with requests for sending commands and data to Cougar is as follows First New Position and Rate commands next Reset Wrist commands then the two wrist packet queues the interrupt queue and the normal user process queue 6 Examples What follows are a few examples of the life history of a request from the foreign host through the main Puma process and possibly through the ancillary processes and Cougar See the accompanying figures 6 1 A simple informative request Here The Here request is received by the Puma 11 The top level loop dispatches to the HERE handler routine The current joint angles are retrieved from the global data buffer where they are always stored the move process updates them every servo cycle and the forward kinematics are applied to them resulting in the desired transform The 3x4 transform is then returned to the foreign host 6 2 A motion request Set Joint Angles The main process verifies that the desired joint angles are in range for each of the joints Then the
33. nding requests to Cougar One process the move process han dles communication with the Unimation controller and calculates the trajectory for the manipulator The latter process is not scheduled by Minits but is interrupt driven basically it is the interrupt service routine for servoing the arm The move process also provides support for compliant motion 11 Requests Responses Main process Chaosnet l lt gt To User Data requests Move packets Newmatrices Force data Bine a Gauge data Guard hit information o New joint PS i To Cougar l Parallel interface j Wrist Input Current joint positions Arm status To Unimation controller N New Theta Dot commands NX Position Rate info Figure 2 Block diagram of the Puma processes 12 5 PROCESSES These processes are created only when the connection is established between the forcign host and the Puma server The main process is created through instructions provided to the Chaosnet software it in turn creates the wrist and move processes When the connection is closed all the processes are destroyed The main process is defined in the file PUMA PALX The move process is defined in MVPROC PALX Low level utility routines including all the routines used to communicate to the Unimation controller are found in PMUTIL PALX arithmetic utilities are in ARITH PALX The compliance support and wrist PDP 11 communication processes are defined in CO
34. ng commands between Cougar and Puma In the Name column is the name which Puma gives to the command The letters in parentheses in that column form the label of the subroutine in Cougar which executes the command All commands whether a Puma Request or a Cougar Response consist of two parts a one word code that specifies the command and a characteristic number of data words Note that subroutine NOOP which is a return statement is called for several of the commands This does not signify a dummy command in these cases the purpose the command is only to transfer data to some location D Puma Hardware Components The following is a description of the hardware of which the Puma PDP 11 is composed They are listed in the order they appear in the backplane as of 16 April 1985 All addresses are in octal Numbers in parentheses after the CSR addresses indicate the number of consecutive words used by the device Table 2 lists the addresses used on the I O page including all internally used addresses This is a complete list of all words in the range 760000 777776 which respond to a TST instruction Table 3 lists the known used interrupt vectors The devices by QBUS slot Slot 1 left KDF 11 LSI 11 23 CPU M8186 Slot 1 right Empty Slot 2 FPF 11 Floating point processor M8188 Slot 3 left 256K bytes MOS memory Slot 3 right KWV 11C Programmable real time clock M4002 The clock output is connected to Cougar s clock input
35. nsist of one or many packets but there must be at least one There must be a way of detecting the last packet of a multiple packet response in the last packet of that response e g an empty packet e Each packet sent must contain a sequence number either as part of the underlying communication protocol or as part of the defined protocol for the manipulator e Any packet sent to the lisp machine as a response must contain the sequence number from the request This is to match it up e Each request packet and response packet contains an operation code identifying what type of request or response it is Implementing such a protocol in the Manip system requires definition of appropriate response data extractors and respuiuse handlers as well as manipulator request codes Tliis is made as easy as possible However several response handlers and data extractors are provided by the Manip system Use of this already existing support requires adherence to the following defined response opcodes For m more detail consult the protocol description for the Puma robot later in this document normal response Opcode 0 A normal response This contains whatever data are expected from the request that was sent fatal error Opcode 1 A fatal error condition This contains an error string and implies that the data connection between the lisp machine and the controller is or will be broken closed non fatal error Opcode 2 An error condition t
36. perations to get the data from the packet There are four values which are e The response opcode an integer e The request sequence number e The index into the packet where the data starts The packet is ART 16B e The number of bytes of response data in the packet This may be zero get response opcode This is defined by default to be just get response info as it is expected to return the opcode which is the first value returned by the info message lt may be redefined by a mixin for efficiency set up communications This message takes no arguments and no return values are expected This operation must see to it that the connection to the manipulator controller is successfully established The background process is not running at the time this method gets called if that makes a difference disconnect NOTE WELL This method is pre defined by manip basic protocol mixin Its mention here is to say that a daemon method should probably be put on this message to make the connection to the manipulator controller go away In addition to the required methods described above there are a few that it is useful to put daemons on for various actions queue request This method is defined by basic protocol mixin and makes the request get put on the user request queue Its two arguments are the request and the queue A before daemon is useful here to allocate a network packet store the request data into it and save it in the request packe
37. re Puma was ready This problem is handled by adding an in progress bit to IDXS This bit is turned on when the routine is initially called and turned off by IDXS when it empties the output buffer The turn on routine never starts IDXS if the in progress bit is set There are no such problems with IDXR the receive counterpart of this routine 22 B COMPONENTS OF THE COUGAR SOFTWARE Appendix A Cougar Hardware Components The Cougar system is composed of these hardware components e An SA BA11 N 8 slot backplane with power supply and line time clock e An LSI 11 23 processor with FPF 11 Hoating point accelerator board e An MXV 11AA board with bootstrap ROM and terminal port e A Data Translation DT 2762 A D converter e A KWV 11C programmable clock e A DRV 11J four port parallel 16 bit IO board e A Chaos net board e A 128k memory board with memory management e An RTI Force Sensing Wrist Physically port C of the DRV 11J is used for input and port D for output each being connected to its counterpart on Puma s DRV 11J The KWV 11C is operated as a slave and is driven by the KWV 11C in Puma Cougar should be operated with the line time clock switched to off B Components of the Cougar Software Each of the following subheadings is a PALX file in the Cougar system Most are also the label of the principal subroutine in that file B 1 INIT The INIT routine is executed exactly once when the Cougar system is loaded Among other duties it sets up
38. re no optional arguments Second a handler must be defined for the response This is where it gets slightly tricky When a response packet comes back from the manipulator controller it contains a numeric opcode However different manipulator protocols may use the same numeric opcode for different responses Thus to define handlers for the response in a new protocol you must first define a response handler type This is done using manip define response handler type symbol This response handler type must be supplied to the manipulator flavor instance in order for the background process to look at the new type for response handlers The instance variable manip response type list of manip basic protocol mixin is a list of the response types the manipulator recognizes By default this list consists of only one type manip generic A handler function is created using manip define manipulator response handler response code type arglist amp body body This will define a function to handle that response The response code is the symbol defined by manip define manipulator response code and the type should be one defined by manip define response handler type The function is passed three arguments the manipulator in stance the response packet and the requests in process queue The body of the handler is expected to do whatever is necessary to process the response packet However the background process itself will return the packet using the
39. received which requires action from any of the ancillary processes such as a request to move the arm or to send a new matrix to Cougar the data portion of the request is copied into a move packet or a wrist packet as necessary and linked onto a queue of similar requests to be handled by the appropriate process Once this is done the main process returns a response to the user without waiting for the request actually to be handled by the move or wrist process This is so that the foreign host may send several such requests in succession allowing the Puma 11 to process all the motion requests and provide smooth transitions between requested segments However if the request itself requires information from the appropriate ancillary process for example an Examine Wrist command the main process will indeed wait for the data to be returned 5 2 The Move Process The move process is actually the interrupt service routine for the programmable clock It is activated every sixteen milliseconds performs the calculations necessary to keep the arm moving or stationary in the requested trajectory checking for possible collisions with the environment calculating the next set of joint angles communicating with the Wrist 11 for compliance and sending new joint angles to the Unimation controller Collisions are tested for by checking that the arm actually arrived at the joint angles that were requested of the controller in the previous
40. rm starts moving but that in the midst of the inotion the user presses the panic button shutting off power to the arm The main process has in fact returned a positive response to the user indicating that the motion segment has becn successfully queued The move process however will detect the power off condition on the next servo loop and will cause an asynchronous error to be signalled to the user It will also abort the current segment as well as any further queued move packets Further motion requests will be refused until the abort condition is reset Then operations will proceed as before 6 3 A Wrist 11 request Read Forces When the user requires data from Cougar the main process must send the request for the data to Cougar then wait for a response The sequence of operations is as follows The request is reccived by the main process which translates it into a request to Cougar In this case before Cougar can return accurate gravity compensated force and torque information the current arm position must be supplied to it Thus the request handler first queues the the current joint angles to be sent to Cougar followed by the request 6 3 A Wrist 11 request Read Forces Puma 11 LispM Main proc Move proc Set Joint Angles request Move packet queued Response Here request Other requests may be serviced while motion is in progress including more move requests which are queued Response 15
41. rver the error occured It should not contain a colon character Severity is a short one or two characters indication of how severe the error is Code is a three letter code for the error The user end of the protocol may make use of the severity and code fields The message is free format and if a null is present then special characters are significant in the string Each special character is a place where one or more numbers should be substituted in the string Ascii 176 means that a raw 16 bit number should be substituted in ascii 44 means that the 16 bit number is a bit mask describing joint numbers a 6 would signify joints 2 and 3 a 1 would signify joint 1 etc The hairy error string cruft is meant to make it easy for the server to return meaningful error messages It is assumed that the user has better string processing facilities than PALX 11 at his her end Example During calibration F NZI No zero index found on joint s lt null gt lt 16b joint mask gt Where the lt null gt and lt 16b joint mask gt are single bytes a zero byte and joint mask Defined severity codes F Fatal error E Non fatal error C Error in the format or data of a response Command error W Warning BF Bug in the software Fatal BE Bug in the software non fatal The following error codes are defined by the protocol but others may be used by specific manipulators E 3 Server Opcodes 31 NAP No arm po
42. s Write Gauge Offset Vector Specifies the vector which is subtracted from the raw gauge readings Table 1 Puma Cougar protocol commands 27 Address Device 764140 764152 Chaosnet interface 764156 22 764160 764176 Cougar interface DRV 11J 767760 767764 Finger interface DRV 11C 767770 767774 Unimation interface DRV 11C 770420 770422 Real time clock KWV 1iC 772300 772316 Mem Mgt Kernel PDR 772340 772356 MM Kernel PAR 772516 MM Status register SR3 773000 773776 Boot ROM MXV 11 776500 776506 Serial line 0 teach box MXV 11 777546 Line time clock internal 777560 777566 Serial line 1 console MXV 11 777572 777576 MM Status registers 777600 777616 MM User PDR 777640 777656 MM User PAR 777776 Processor Status Word Table 2 I O Page addresses Slot 5 right MXV 11AA Multi purpose module Contains bootstrap ROM for network bootstrap two asynchronous serial lines and unused memory The two serial lines are used as the console line and for the teach box Both serial lines are configured to be 9600 baud eight data bits no parity one stop bit Serial line 0 CSR 176500 4 VEC 300 Serial line 1 CSR 177560 4 VEC 60 Slot 6 Chaosnet interface CSR 164140 6 VEC 270 E The Chaos Manipulator Protocol This section is a slightly edited version of an unpublished document written by Patrick Sobalvarro A connection is opened by connecting to the server for the robot on that machine There
43. servo cycle If the current angles are not within a small tolerance the arm is stopped where it is and an error indication is queued to be sent to the foreign host However under compliance we do not expect the arm to necessarily get within the tolerance limit so the collision test is inhibited We depend on the compliance calculations to handle interaction with firm objects in the environment There are five interpolation schemes available in the move process a linear interpolation with quadratic transitions betwcen segments a fifth degree polynomial interpolation providing zero velocity and acceleration at the endpoints of the segment a cosine wave interpolation which varies a single joint s angle along a cosine curve this is intended for debugging only and should not be used in normal operation aud two compliant 5 3 The Wrist processes 13 motion interpolations one for debugging the compliance code and one for motion The compliant motion interpolation calculates the trajectory based on the linear quadratic interpolation then adjusts it based on its communcation with Cougar Each segment of the trajectory may use any one of the interpolation schemes although some of them are not compatible for smooth motion To calculate the next joint angle vector to send to the Unimation controller the move process merely dispatches to the appropriate interpolation routine When performing coinpliance the move process communicates with Cougar v
44. should be one server for each robot on the machine Once the connection has been established the user should wait for the server to send a RESPONSE packet and then it s no holds barred The rest of the protocol can be described with opcodes We use the 8 bit data series opcodes 200 277 as commands from the user Information is returned as described per opcode below NOTE Where floating point data are specified the format used is PDP 11 single precision 32 bits E 1 User Opcodes Opcode 200 describe self The manipulator should respond with a stream of response packets termi nated with an empty response packet The packets should contain a Lisp readable ascii description of the manipulator connected to We use an ascii description for clarity and because speed is not terribly important in a describe self operation The description is an alist Following is a list of allowable descriptors and their definitions 28 E THE CHAOS MANIPULATOR PROTOCOL Address i Time out not normally handled Ilegal instruction not handled BPT instruction debugging IOT instruction MINITS scheduler Power fail Not yet handled will be in future EMT instruction MINITS system calls TRAP instruction MINITS unexpected interrupt handler Console serial line MXV 11 line 1 Line clock used by MINITS Memory parity error unhandled 200 204 Unimation interface DRV 11C 210 214 Finger interface DRV 11C as E 220 224 Cougar interface
45. simple informative request Here es 13 6 2 A motion request Set Joint Angles o o o 13 6 3 A Wrist 11 request Read Forces o o o 14 6d Compliance 5 se ea oaa RA A RA O A SS 17 HI Cougar PDP 11 System 19 7 Overview of Cougar Software 19 Tl Background Task oo rom ea e A Bie A ae A ae 19 7 2 Data Acquisition o teetan ea o 2 a 19 7 3 Data Processing lt ooooocooooocrrsscrrcra rss ase 19 7 4 Communication s 26 66 ee ee o o se isa ss 19 AA RAR a Baal 20 8 Complications 20 8 1 Intermediate Values ee 9 20 8 2 Wrist Data elena Das er E a ada elite e os 20 8 3 Drift and Offset o oco ness ds aa a a a 20 8 4 Data Transfer 4 2 0 2 20 A Cougar Hardware Components 22 CONTENTS B Components of the Cougar Software Bil INT a Pb as Aven ithe Se Ae ae a B 2 JACOB i acted LAA ass Wena ah Bid IMOVE a A a ae a ee ee S BA ADC ni ae Sita a OE ee ee oe EA BILIDR a O is Wa teres A ta BAS MISCOM a ds a a e ela Soa se BLOMA TH AA AT AO EA Bil PEND 50000 os Di ad Command Protocol D Puma Hardware Components E The Chaos Manipulator Protocol Eid User Opcodes vicio a a Kw E 2 Server Responses o o o E 3 Server Opcodes o o ooooo ooo o Ce a so ro a
46. t slot of the request structure The advantage of this is that any problems in this activity are found in the user process at the time the request is created rather than in the background process at some later time 3 2 Implementing new Request Response codes 9 sinitialize This method is used to initialize operation of the manipulator Useful daemons to put on this method are clean up operations to make sure everything is in a pristene state or to make sure that old connections are gracefully closed if necessary Sec the network example Useful functions which may be used by a protocol implementation copy manipulator request data This function accepts the request a packet array ART 16B and a starting index in the array and copies the request data into the packet The operation is fairly intelli gent in that it will attempt to interpret the data and store in the packet appropriately For example for a list of objects each element of the list is stored in the packet in sequence Note however that a fixnum is always stored as a 16 bit quantitiy and a flonum is always stored as a 32 bit PDP 11 style floating point quantity The correct type of number must always be passed to copy manipulator request data This function returns the index following the last one stored into 3 2 Implementing new Request Response codes Creating new request codes is easy Simply use the form manip define manipulator request code symbol opcode which d
47. t of its reach a non fatal error response is generated If the arm power is turned off a non fatal error is generated Opcode 203 Asynchronous response This response may be sent when a condition becomes true asynchronously with command requests and responses Examples of this would be hitting a guard or completing a trajectory segment These would only be sent when requested by the user end in an earlier request The first word of the response is a code indicating the condition that elicited the response The defined codes are 1 guard hit 2 move segment completed The subsequent words are additional data for the response Second word Third word Guard hit 1 stop trajectory Guard number 2 continue Segment end reserved Segment number Opcode 204 Asynchronous non fatal error The format is exactly like the normal non fatal error The request number is the last request that was processed Opcode 205 Asynchronous warning Like an error but not serious Should not interfere with on going computation but the human user should be alterted to the condition Opcodes 250 277 are reserved for non general i e arm specific applications
48. tions module and a package of utility programs 7 1 Background Task In order to convert between joint and cartesian space as the processes in Cougar must do it is necessary to have an up to date Jacobian transformation matrix available Cougar is given joint position information by Puma from which it computes the Jacobian The subroutine which does this runs continuously even recomputing the Jacobian when no new data have been received All interrupt driven routines however have priority over it 7 2 Data Acquisition The prime function of Cougar is to acquire data from the force sensing wrist This it does under the control of an interrupt driven routine operating at the servo rate That rate is decided by Puma which provides the clock signal to trigger Cougar The force sensing wrist has eight strain gauges each of which is connected to a channel of the A D converter in Cougar When gathering data from the wrist each channel in turn is triggered to start a conversion Cougar waits for the conversion to finish and the result is stored for later processing 7 3 Data Processing Following its acquisition the digitized strain gauge data is multiplied by a conversion matrix to transform it into force torque vector This along with other data from Puma is entered into the compliance equation to compute a new incremental velocity vector Also in this process is the computation of the gravitational correction and and a test of any motion guards
49. tocol version is the version number of this protocol The version described here is version number 1 All protocol versions must support the describe self operation identically There should probably be more stuff here like things to describe the geometry and touch and force sensing so that a program could conclude whether a manipulator is capable of performing a function but I haven t given much thought to that yet Opcode 201 Here The response contains a sequence of floating point numbers giving position infor mation The position information returned is a 3x4 matrix the first three columns being a rotation matrix and position in the fourth column represented in column major order Thus if we represent the rotation matrix as E 1 User Opcodes 29 Nz Oz Az Pz Ny Oy Ay Py 1 Nz Oz Az Pz It will be sent in this order NrNyNzOzOy PyPz Opcode 202 Joint angles The data in the packet are floating point numbers representing the angles of the manipulator s joints starting at the base The values returned by manipulators with extensile degrees of freedom e g the Purbrick arm are interpreted as being cartesian for those degrees of freedom Opcode 203 Calibrate Manipulators that do not need calibration should send a positive response to this packet The data section is empty The returned packet is essentially a done and is empty Opcode 204 Move The data are 12 PDP 11 style floating point numbers
50. wer AWA Arm motion was aborted no further commands will be processed until a reset operation is requested JOR Joint out of range TOR Solution of a transform resulted in out of range joints There are more see the Puma PDP 11 code E 3 Server Opcodes Opcode 200 Response The first two bytes of data contain the number of the packet that this one is a response to If the response is a simple done there are no further data Otherwise the data are per opcode as described above Opcode 201 Fatal error The first two bytes contain the number of the packet last received when the fatal error was encountered The data section contains a string describing the nature of the lossage as described above After transmitting an error packet the server will send a CLS and kill the server process Fatal errors are usually generated when the server is in a state such that it cannot reasonably execute any further commands until remedial action is taken Opcode 202 Non fatal error response The first two bytes of data are the number of the packet that this one is a response to the rest of the data section is an error string as described above A non fatal error response is generated in response to a command and indicates that while this command cannot be performed successfully there is no reason to believe that further commands cannot be performed successfully For example if the manipulator is told to move somewhere ou
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