PRIOR ART Before an industrial robot is to be put in operation for a certain task, it must be programmed to carry out the task. When pro- gramming an industrial robot, a robot language is used. There exist a plurality of different robot languages, since each robot supplier has developed its own robot language. The robot lan- guage is formed such that it is simple to use for the robot user, who may be a person without knowledge or experience of pro- gramming. A robot language may consist of two types of robot instructions; fixed robot instructions and shell instructions. The fixed robot instructions consist of calls to fixed routines, com- prising a set of instructions written in a general high-level lan- guage. The shell instructions consist of calls to so-called shell routines, comprising a set of instructions written in the robot lan- guage. A shell routine can easily be created be the robot user.

The concept of shell routines is described in more detail in the patent application EP0673726A2. A robot program may com- prise calls to routines such as subroutines, functions, and shell

routines, each written in a robot language and stored in the pro- gram storage. A function is a subroutine that always returns a value when called at.

A robot program comprises a series of robot instruction written in a robot language. Normally, a robot program comprises a main routine having a number of calls to subroutines, function and shell routines. The subroutines, functions and shell routines are written in the robot language. A robot language must be de- signed to handle interactive operations from the user. The robot user is for example the robot programmer or operator. During execution of the robot program a program counter, pointing at the program instruction being currently executed, is displayed to the user. Before the robot program is used it should be test run.

During the test run, the user often has to interrupt the robot pro- gram, and restart it from another point in the program, for exam- ple restart it from the beginning of the main routine. Thus, for testing purpose and production management it must be possible to stop the program execution and move the program counter to the main routine or some other routine and restart the execution from that point. Also for automatic error recovery in the program, the execution and the program counter can be transferred to some other routine for continue of the execution.

For all these type of more and less unexpected move of the pro- gram counter without complete execution of the program routine, there is a need of cleaning up and resetting of allocated system or program resources. Example of things that need to be han- dled after an unexpected move of the program counter is reset of program variables, reset of modal program settings for robot movement such as velocity override, acceleration limitation, configuration supervision, program displacement, soft servo and servo tuning, reset of synchronized movement of several robots, close of open files and serial. channels, unload of program mod-

ules, user interaction and cancel of subscription of interrupts for 1/0, timer, execution error and variable change.

A problem is how to take care of these suddenly and unexpected move of the program counter and how to do the cleanup and re- set. Today, when the program counter has unexpectedly been moved out of a program routine, the control system of the robot tries to foresee which recourses have been allocated and take care of the cleaning and resetting. However, this solution is not satisfying since the control system is not aware of all the sys- tems and program resources allocated by the user's program.

Consequently the control system cannot do all the necessary cleaning, resulting in that some recourses allocated by a par- tially executed or aborted routine remains allocated even after the routine is abandoned.

OBJECTS AND SUMMARY OF THE INVENTION The object of the present invention is to provide a control sys- tem for an industrial robot, which in an improved way takes care of the cleaning up after partially executed or aborted routines of a robot program.

This object is achieved by means of the initially defined control system, which is characterized in that it further comprises a cleanup executer for cleaning up after partially executed or aborted routines, wherein the cleanup executer is adapted to upon activation, determine whether the partially executed or aborted routine comprises a cleanup handler having a series of robot program instructions for cleaning up and/or resetting re- sources allocated by the routine, and if the routine comprises a cleanup handler, to execute the robot program instructions of the cleanup handler. The cleanup handler either comprises the program instructions for cleanup and/or reset or comprises a call to another routine comprising the program instructions for cleanup and/or resetting. The object of the cleanup handler is to

cleanup remaining side effects after partially executed routines, e. g. canceling modal instructions, such as opening a file. A mo- dal instruction is an instruction that performs a lasting adjust- ment of the system or the user program, for example sets one or more global parameters, functions or allocate external re- sources. A cleanup handler can access any variable or symbol reachable from the normal routine body, i. e. from the normal program code of the routine, including locally declared vari- ables.. For instance, the routine comprising the cleanup handler is a main routine, a subroutine, a shell routine or a function or any other routine.

The problem is solved by introducing a cleanup handler in the robot language. In the cleanup handler the programmer of the robot program can put robot instructions of any kind from the robot language. The robot instructions of the cleanup handler should typically perform clean-up actions, for instance closing a file. Upon activation of the cleanup executer, for example at an unexpected move of the program counter from the routine, the cleanup handler is executed and necessary cleanup and reset is done. Not all routines need to have a cleanup handler. It is op- tional to provide a routine with a cleanup handler or not. Thus, it is up to the programmer to decide whether a routine should have a cleanup handler or not. The cleanup handler belongs to the routine and is written in the robot language. Thanks to the fact that the cleanup handler is written by the robot programmer, who is aware of what the routine does and which resources is allocates, it possible to write in advance a cleanup handler that takes care of all the necessary cleanup.

The purpose of the cleanup functionality is to support automatic deactivation of modal instructions when aborting a routine, for example when moving the program counter out of the current routine. A cleanup handler is a list of instructions that are exe- cuted by the program executor on certain system events that leaves the routine only partly executed. An activation event is

for example when the program counter is moved out of a rou- tine.

A program routine can be aborted at any point by moving the program counter out of the routine. In some cases, when the program is executing certain sensitive routines, it is unsuitable to abort. Using the cleanup executer it is possible. to protect such sensitive routines against unexpected program reset. With the cleanup executer it is possible to have certain code exe- cuted automatically if the routine is aborted.

It is advantageous to activate the cleanup executer upon an un- expected movement of the program counter. The cleanup han- dler is then executed before the program counter is moved. It is particularly advantageous to activate the cleanup executer upon receiving a move program counter command from the user, for instance if the user moves the program counter from a sub rou- tine to the main routine. However, the cleanup executer is also activated if an exit-instruction is executed, causing the program to reset, if the program is reset for some other reason, for in- stance when changing some configuration, or if the program or any routine of the program is deleted. The cleanup executer should not be activated if the program returns as usual form the routine, for example if the program reaches the end of the rou- tine or on a return statement.

According to an embodiment of the invention the program exe- cuter comprises means for locking the position of the user pro- gram counter during execution of the cleanup handler. The pro- gram counter shall be invisible for the user when executing a cleanup handler. This is achieved by locking the position of the user program counter. When the cleanup handler is executed the program counter remain in its old location, but is updated when the cleanup handler is finished.

According to an embodiment of the invention each cleanup han- dler comprises a word reserved for identifying that it is a cleanup handler, and the cleanup executer is adapted to deter- mine whether the currently executed routine includes a cleanup handler by determining whether the currently executed routine comprises said reserved word or not. According to the invention, the robot language is provided with a reserved word, i. e. a word not allowed to be used for any other purpose in the routine, for identifying that a procedure or routine comprises a cleanup han- dler. Having a reserved word in the cleanup handler makes it easy for the cleanup executer to identify if the routine has a cleanup handler or not.

According to an embodiment of the invention, the cleanup exe- cuter is adapted to determine whether said partially executed or aborted routine has been called at from a previously executed routine, to determine whether the previously executed routine comprises a cleanup handler and to execute the robot program instructions of the cleanup handler of the previously executed routine. Preferably, the cleanup executer is adapted to upon ac- tivation detect and run all cleanup handlers in all routines in a call-chain from a main routine to the partially executed or aborted routine. If the partially executed or aborted routine is a part of a chain of routine calls, the other routines of the call chain have also been invoked, but not yet terminated. According to this embodiment all cleanup handlers in the routines of the can-chain is executed when the cleanup executer is activated.

Thus, all resources allocated by the program are cleaned up upon activation of the cleanup executer.

According to an embodiment of the invention the program exe- cuter is adapted to disregard any program instruction in the cleanup handler involving moving the robot. By not allowing any instructions causing movements of the robot, collisions are avoided and the security of the user is guaranteed.

Another object of the present invention is to provide an im- proved method for cleaning up after partially executed or aborted routines of a robot program for an industrial robot during running of the robot program. This object is achieved by the method of the invention as defined in claim 10.

This object is also achieved by a computer program directly loadable into the internal memory of the computer or a proces- sor, comprising software code portions for performing the steps of the method according to the invention, when said program is run on a computer. The computer program product is provided either on a computer readable medium or through a network, such as the Internet.

The object is also achieved by a computer readable medium having a program recorded thereon, when the program is to make a computer perform the steps of the method according to the invention, and said program is run on the computer.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained more closely by the descrip- tion of different embodiments of the invention and with reference to the appended figures.

Fig. 1 shows part of a control system according to the inven- tion.

Fig. 2 shows an example of a procedure of a robot program having a cleanup handler according to an embodiment of the invention.

Fig. 3 shows an example of a call-chain of procedures, in which some of the procedures have a cleanup handler.

Fig. 4 shows in the form of a flow diagram an example of how the cleanup executer cleans up partially executed rou- tines.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION An industrial robot comprises a manipulator 1 and a control sys- tem 2 for controlling the movements of the manipulator. Fig. 1 shows a block scheme of those parts of the control system 2, which are of interest to the invention. During programming and testing of a robot program, the robot operator communicates with the control system 2 via a teach pendant 3. The operator inputs commands to the control system, for example, for starting and stopping the user program, for moving the program counter to another position of the user program and for restarting execu- tion of the user program from the new position of the program counter. The control system 2 comprises a compiler 4 for com- piling the robot program, a linker 5 for linking the robot program, a program storage 6 for storage of the robot program, and a pro- gram executor 7 for executing the robot program. The program executor 7 is also adapted to provide a program counter, point- ing at the program instruction being currently executed.

The control system further comprises a cleanup executor 8 for cleaning up after partially executed or aborted routines. Pref- erably, the cleanup executor 8 is a part of the program executor 7. A user program comprises one or more program routines in- cluding a series of robot program instructions written in a robot language. The robot instructions may be of two types, fixed ro- bot instructions or shell instructions. The shell instructions con- sist of calls to shell routines comprising a set of robot instruc- tions. A shell routine is translated into an intermediate code by the compiler 4 and is stored in the program storage 6. In the same way, a user program is translated by the compiler. and stored in the program storage. The program executor 7 then

executes the user program. A robot program may comprise calls to routines such as subroutines, functions, and shell routines, each written in a robot language and stored in the program stor- age 6. A function is a subroutine that always returns a value when called at.

A cleanup handler is an optional part of a routine containing program instructions for performing cleanup actions. According to the invention, the robot language is provided with a reserved word, i. e. a word not allowed to be used for any other purpose in the routine, for identifying that a procedure or routine comprises a cleanup handler. Fig. 2 shows a robot program 10 having a cleanup handler 12. The cleanup handler 12 is located in the bottom of the program routine"Proc Main". The cleanup handler 12 comprises robot program instructions written by the robot programmer specifically for that routine. Thus, each cleanup routine is individually written to be adapted to the routine, to which it belongs. If the program counter is moved out of the rou- tine, or if the routine is deleted, the cleanup handler is automa- tically executed.

A cleanup handler is not mandatory. Skipping it will result in that no cleanup handler is executed for that routine. Supplying an empty cleanup handler, i. e. the body of the cleanup handler is empty, has the same meaning as skipping it entirely, no cleanup handler is executed for that routine.

The object of the cleanup handler is to cleanup remaining side effects after partially executed routines, e. g. canceling modal instructions, such as opening a file. A modal instruction is an instruction that performs a lasting adjustment of the system or the user program, for example sets one or more global parame- ters, functions or allocate external resources. A cleanup handler can access any variable or symbol reachable from the normal routine body, including locally declared variables. Most parts of the program language can be used in a cleanup handler, but

there are some limitations, for example, motion instructions are not allowed. Accordingly, execution of a cleanup handler will not reset robot motions caused by the routine. Further, the cleanup handler is not allowed to contain instructions such as STOP, BREAK, RAISE, or RETURN. If an attempt is made to use any of these instructions, the instruction will be ignored and a warning will be generated. Since routine calls are allowed in a cleanup handler, the restrictions must also apply to routines called by the cleanup handler as well.

A cleanup handler is not mandatory. Skipping it will result in that no cleanup handler is executed for that routine. Supplying an empty cleanup handler, i. e. the body of the cleanup handler is empty, has the same meaning as skipping it entirely, no cleanup handler is executed for that routine.

The execution of a cleanup routine is always continuous. All break points are ignored when executing the cleanup handlers.

It is not possible to step the cleanup handler. When the cleanup handler starts, the execution mode is automatically set to"con- tinuous". After the cleanup session is finished, the previous exe- cution mode is restored. If the program is stopped while execut- ing a cleanup handler, the rest of the program instructions will not be executed, if there are additional cleanup handlers in the call chain that have not yet been executed, they will be ignored as well. This will result in a warning. It is not possible to move the program counter into a cleanup handler.

During normal execution of a routine, a program counter 14 is shown to the user. The program counter points at the instruction being currently executed. However, the program counter is not visible in a cleanup handler. When the cleanup handler is exe- cuted, the program counter remains at its previous location, but it is updated when the cleanup handler is finished. An EXIT in- struction aborts the cleanup procedure in a similar way as a time-out error or a stop. The rest of the cleanup handlers in the

call chain are ignored and the program counter is moved to the main routine.

Fig. 3 shows a chain of procedure calls. A main routine 16 has made a call to routine A, 18, which has made a call to routine B, 20, which has made a call to procedure C, 22. The main routine 16, routines B, and routine C is provided with cleanup handlers 24,26, and 28. When the cleanup executer is activated, all the cleanup handlers in the call chain are executed. As disclosed in Fig. 3, the program counter 14 has unexpectedly been moved from routine C to the main routine 16. The cleanup handlers are processed in the same order, as the routines would have been returned. The cleanup handler closest to the end of the call chain, i. e. cleanup handler 28 of routine C will be executed first and the routine closest to the main procedure will be executed last. In this example, the main procedure comprises a cleanup handler 24 and this cleanup handler will be executed last in the chain. All cleanup handlers in the procedure call chain are exe- cuted from the bottom to the top.

The purpose of the cleanup functionality is to support automatic deactivation of modal instructions when aborting a routine, for example when moving the program counter out of the current routine. A cleanup handler is a list of instructions that are exe- cuted by the program executor on certain system events that leaves the routine only partly executed. An activation event is for example when the program counter is moved out of a rou- tine. The cleanup handler is for example defined inside a routine and below the routine body. The cleanup handler has access to the variables declared in the routine encapsulating it. In order to execute the cleanup handler, an activation event has to occur.

If an exit statement is executed causing the program counter to be moved to the main routine, any cleanup handlers on the call chain back is to be executed. This is done by starting a cleanup session. It is possible to stop the execution of a cleanup ses-

sion, but it is not possible to resume the cleanup session, if it has been stopped. If this happens, a warning is presented noti- fying the user of the only partially executed cleanup session.

When starting the system again, the action that trigs the cleanup is to be immediately carried out, i. e. moving the program counter. If a time-out error occurs or the program executor is stopped while executing a cleanup session, the session is aborted. The current cleanup handler is aborted and no other cleanup handlers of routines on the call stack are to be exe- cuted.

If an error occurs when executing a cleanup session, any error handlers must be ignored. On error in a cleanup handler, the cleanup handler is terminated and considered consumed. A warning must be presented to the user. If the execution of a cleanup handler takes too much time, say more than a second or so, a man machine interface should present some sort of dia- logue box to the user, so that the user will know what is going on.

All types of routines can have a cleanup handler. In this em- bodiment a keyword, for example, cleanup or undo, marks the start of the cleanup handler. The code of the cleanup handler will follow after the keyword. The end of the cleanup handler is the end statement of the routine, since the cleanup handler is the last item of the routine. The internal data structure of the program executor needs the introduction of three fields to sup- port the cleanup : a statement list, an entry flag, and a source position pointer for storing the location of the cleanup handler.

The cleanup handler of a routine is called when the program counter is moved out of the current routine by user interaction or an exit instruction. To trig a cleanup handler by moving the pro- gram counter is only possible when the system is stopped and the user explicitly moves the program counter to a location out- side the routine. Other events that reset the program executor

will also trigger the cleanup, provided that the program counter is in a routine having a cleanup handler. A cleanup session is not started if the program reaches the end of the routine or a return statement and thus returns as usual from the. routine.

A cleanup session is started by the activation of the cleanup ex- ecutor. The cleanup executor is activated either upon calling on it with a start cleanup session command or upon execution of an exit instruction. The cleanup executor comprises an instruction control unit responsible for rejecting forbidden instructions. The instruction control unit is activated only when executing a cleanup session. Another necessary control is a cleanup session control. If a basic step is executed when the program counter is in the routine body and the cleanup state is finished, the corre- sponding cleanup handler is started. This situation occurs, when a cleanup handler is finished and has returned to its caller. A third control is the break point check, which makes sure that the program executor does not stop on a break point when execut- ing a cleanup session.

After the execution of a cleanup handler is finished, the cleanup state is set to"finished"to indicate that the cleanup session is still active, but not executing a cleanup handler. If no more cleanup handlers exist in the call chain, the session is finished and the cleanup state is set to"new session". When a cleanup session is finished, the last cleanup handler has been executed or the session has been aborted, a special code is returned tell- ing that a cleanup session is finished.

Fig. 4 is a flow chart illustration of the method and the computer program product according to an embodiment of the present in- vention. It will be understood that each block of the flow chart can be implemented by computer program instructions. In this embodiment, the cleanup executor is a part of the program ex- ecutor. In block 30, the program executor runs the user pro- gram. If an unexpected move of the program counter occurs, or

the program or a procedure of the program is deleted, block 32, the cleanup executor is activated and a cleanup session is started, block 33. The cleanup executor performs the following steps.

Upon activation the cleanup executor determines whether the interrupted or deleted routine comprises a cleanup handler. The cleanup executor determines whether the routine comprises a cleanup handler or not by determining whether the routine in- cludes the keyword identifying that the program module is a cleanup handler, block 34. If the interrupted or deleted routine comprises a cleanup routine, the cleanup handler is executed, block 36. If the interrupted or deleted routine is the main routine of the program, and it has already been cleanup, the cleanup session is terminated, block 38. If the interrupted routine is not the main routine, the program executor steps back in the call chain to the preceding routine, block 40. The same procedure is repeated for the preceding routine, including executing the cleanup handler of the preceding routine, if there is any. This procedure is repeated for all the procedures in the call chain, until all the cleanup handlers of the call chain are executed and the main routine is reached and its cleanup handler has been executed. If any routine does not comprise a cleanup handler, block 34, and the routine is not the main routine, block 38, the cleanup executer steps to the preceding routine in the call chain, block 40.

The present invention is not limited to the embodiments dis- closed but may be varied and modified within the scope of the following claims. For example in another embodiment the cleanup handler comprises a call to a subroutine comprising the cleanup instructions.