Abstract:
A control system for performing a synchronously cooperative operation among some robots of a plurality of robots connected by a communication line. A plurality of robots No. 1 to No. 4 is operated individually and also is operated in synchronous cooperation. Further, some robots No. 1 and 2 is operated in synchronous cooperation while the other robots Nos. 2 and 4 are operated in synchronous cooperation. The robots Nos. 3 and 4 are operated in synchronous cooperation. The robots No. 1 and 3 is operated in synchronous cooperation while the robots Nos. 2 and 4 are operated individually. The synchronously cooperative operation is performed by any desired combination in that the above robot control part keeps motion procedures denoting changes, which are corresponding to the frame notifications of the passage of time from the above media reproduction part; and moves the above robot according toe the above motion procedures, in the corresponding frame.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control system for controlling a plurality of industrial robots, and more particularly a control system for performing a synchronously cooperative operation using the plurality of robots. 
     2. Description of the Related Art 
     There has not been provided any practical control system for performing a synchronously cooperative operation using a plurality of robots which are respectively controlled by robot controllers connected with one another by a communication line. In the conventional system for the synchronously cooperative operation of the robots, a changeover between a synchronously cooperative operation and a normal independent operation of the robots is set at the time of constructing the system, and it is necessary to change a basic setting of the system for changing the changeover setting for the synchronous cooperative operation. 
     A combination of robots to be operated in synchronous cooperation has been fixedly set at the time of system construction. In the case where the system has four robots respectively controlled by four robot controllers connected by communication lines, for example, the conventional system has adopted a method in which all of the four robots are operated in synchronous cooperation by these controllers. 
     In the practical use, according to content of an operation, there is a case where it is desirable that all of four robots, in the above-described example, operate in synchronous cooperation, a case where it is desirable that each robot operates individually, a case where it is desirable that only two or only three of the four robots operate in synchronous cooperation and the remaining robots operate individually, and further a case where it is desirable that two of the four robots and the remaining two robots respectively operate in synchronous cooperation. However, in the conventional synchronously cooperative operation system, robots to be operated in synchronous cooperation cannot be selected in accordance with the operation to be performed. Such a system is inconvenient in that all the robots are operated either in synchronous cooperation or individually, so that the synchronously cooperative operation of desired robots selected from the robots in accordance with the kind of operation can not be performed. 
     Furthermore, in the synchronously cooperative operation, an operator of the robots has to pay attention to the motion of the master robot as well as the slave robot since the slave robot operates in accordance with the master robot. However, it is difficult for the operator to recognize the synchronously cooperative operation status of the robots from the motion of the robots. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a control system for a plurality of robots comprises a plurality of robot controllers connected with one another by a communication line, for respectively controlling the plurality of robots. At least one master robot controller is selected for controlling at least one master robot from the plurality of robot controllers, and one or more slave robot controllers is selected for one or more slave robots from the rest of the plurality of robot controllers. The master robot controller sends data regarding positions of taught points and interpolation points for the master robot to each of the slave robot controllers through the communication line, so that each slave robot controller controls the slave robot thereof to perform the synchronously cooperative operation with the master robot based on the data received from the master robot controller. 
     According to another aspect of the present invention, a control system for a plurality of robots comprises robot controllers connected with one another by a communication line, for respectively controlling at least three robots. At least one master robot controller is selected for controlling at least one master robot from the robot controllers, and one or more slave robot controllers is selected for controlling one or more slave robots for the master robot from the rest of the plurality of robot controllers. The master robot controller sends data regarding positions of taught points and interpolation points for the master robot to each of the slave robot controllers through the communication line, so that each slave robot controller controls the slave robot thereof to perform the synchronously cooperative operation with the master robot based on the data received from the master robot controller. 
     Each of the plurality of robot controllers may store a series of operation programs as a combination of a master program to operate the controlled robot as the master robot, a slave program to operate the controlled robot as the slave robot and a normal program to operate the controlled robot independently of the other robots. 
     The synchronously cooperative operation of the master robot and the slave robots may be started and terminated by a program command in an operation program stored in the master robot controller. 
     Each of the master controller and the slave controllers may store an operation program with an attribute for the synchronously cooperative operation, and the synchronously cooperative operation of the master robot and the slave robots may start when the master robot controller and the slave robot controller start execution of the operation programs having the attributes of the synchronously cooperative operation, and terminates with completion of the operation programs having the attributes. 
     The master robot controller and the slave robot controllers may output signals indicative of the midst or the ready of the synchronously cooperative operation when the master robot and the slave robots are in the midst or the ready of the synchronously cooperative operation. 
     The master robot controller and the slave robot controller may output signals indicative of the midst or the ready of the synchronously cooperative operation when the master robot and the slave robots are in the midst or the ready of the synchronously cooperative operation. Thus, an operator of the robot controller can confirm the status of the synchronously cooperative operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of an essential part of a robot controller for controlling an associated robot for performing a cooperative operation of a plurality of robots according to an embodiment of the present invention; 
     FIG. 2 is a schematic diagram showing an example of a network of the robot controllers connected by communication lines; 
     FIG. 3 is a schematic view showing another example of a network of the robot controllers connected by communication lines; 
     FIG. 4 is a table of a setting example of combinations of robots to perform a cooperative operation; 
     FIG. 5 is a table of a link pattern set in a robot No. 1 as a master robot in the example of combinations of robots as shown in FIG. 5; 
     FIG. 6 is a table of a link pattern set in a robot No. 3 as a master robot in the example of combinations of robots as shown in FIG. 5; 
     FIG. 7 is a diagram for showing the operation sequence of the robots in the example of combinations of robots as shown in FIG. 5; 
     FIG. 8 is a diagram of a program sequence stored in each robot in one example of the operation sequence as shown in FIG. 7; 
     FIG. 9 is a partial flowchart of processing to be executed by the processor of the robot controller of each robot as shown in FIG. 1, which is mainly a flowchart of processing to be performed by the robot controller for the robot to operate independently (execution of a normal program); 
     FIG. 10 is a continuation of the flowchart of FIG. 9, which is a part to be executed by the processor of a master robot controller (execution of a master program); 
     FIG. 11 is a continuation of the flowchart of FIG. 10 to be executed by the processor of the master robot controller (execution of the master program); 
     FIG. 12 is a continuation of the flowchart of FIG. 10, which is a part of to be executed by a slave robot controller (execution of a slave program); 
     FIG. 13 is a continuation of the flowchart of FIG. 12 to be executed by the slave robot controller (execution of the slave program); 
     FIG. 14 is a continuation of the flowchart of FIG. 13 to be executed by the slave robot (execution of the slave program); and 
     FIG. 15 is a schematic view of a method for determining interpolation position data of a slave robot on which the motion amount of a master robot is reflected. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a robot controller for controlling each robot for synchronously performing a cooperative operation of a plurality of robots. In FIG. 1, a robot controller  1  has a processor  10  for generally controlling a robot mechanism  2  and the robot controller  1 . The processor  10  is connected with a ROM  11 , a RAM  12 , a nonvolatile memory  13 , a robot axis control section  14 , a communication module  15 , a teaching panel interface  16 , etc. via a bus  18 . The ROM  11  stores a system program to be executed by the processor  10 , and the nonvolatile memory  13  stores set values of various parameters and a taught program for an operation to be performed by the robot mechanism  2 . The RAM  12  is used for temporarily storage of data. The robot axis control section  14  performs feedback controls of position, velocity and torque (current) of each motor for each axis by the digital servo control using a processor based on motion commands fro each axis, to drive the servomotor for each axis of the robot mechanism section  2  via a servo amplifier  17 . The communication module  15  is connected to another robot controller by a communication path. The teaching operation panel interface  16  is connected with a teaching operation panel  3 . 
     The above basic configuration of each robot controller is the same as that of the conventional one, and the robot controllers of such configuration are connected to one another via a signal path of communication lines, to constitute a control system for a synchronously cooperative operation of a plurality of robots. 
     The following is a description on a robot control system for controlling four robots by the robot controllers connected by the signal path for respectively controlling the associated robots, to sequentially perform individual operations and a synchronously cooperative operation of the robots in an arbitrary combination. 
     FIGS. 2 and 3 show examples of connection of the four robot controllers connected by a communication network of Ethernet. Any network other than Ethernet may be used. In an example of FIG. 2, the robot controllers No. 1 to No. 4 are connected to one another by signal lines L to form a signal path. In the example of FIG. 3, the robot controllers Nos. 1-4 are connected to one another by using a hub. To identify each robot connected by the communication lines L, each robot number is applied to each robot, and in the nonvolatile memory of each robot, the robot number assigned to that robot is set and stored. In the examples shown in FIGS. 2 and 3, the number of No. 1 to No. 4 are set and stored. In the following description, No. 1 to No. 4 are used for robot No. 1 to No. 4 and robot controller No. 1 to No. 4. Also, robots No. 1 to No. 4 are used. 
     Further, a transformation matrix from each robot to another robot is set by calibrating the installation position between the robots. For example, when the robot No. 2 is viewed from the robot No. 1, it is necessary to determine a position in a world coordinate system of the robot No. 1 at which a world coordinate system of the robot No. 2 lies. For this purpose, for example, a transformation matrix T 2-1  from the world coordinate system of the robot No. 1 to the world coordinate system of the robot No. 2 is determined. This is done for all patterns. However, since the inverse matrix of the transformation matrix T 2-1  from No. 1 to No. 2 is the transformation matrix from No. 2 to No. 1, when the transformation matrix from No. 1 to No. 2 is determined, it is unnecessary to determine the transformation matrix from No. 2 to No. 1. The transformation matrix thus determined is stored in the nonvolatile memory  13  of each robot controller. For example, the transformation matrix T 1-2  from No. 2 to No. 1 is stored in the controller of the robot No. 2. Similarly, each transformation matrix is stored in the nonvolatile memory  13  of each robot controller, for example, the transformation matrix T 1-3  from No. 3 to No. 1 is stored in the robot controller No. 3, the transformation matrix T 1-4  from No. 4 to No. 1 is stored in the robot controller No. 4, and the transformation matrix T 2-3  is stored in the robot controller No. 3. 
     In the calibration method, as having been carried out so far, a calibration rod is attached to wrists of two robots to be calibrated, and a distal end thereof is set so as to be a TCP (tool center point). Then, the distal ends of the calibration rods are positioned at three points (a triangle is formed with the three points being the vertexes) in a space that do not lie on the same straight line, and the positions are determined by the respective world ordinate system. Thereafter, the transformation matrix T 2-1  from the robot No. 1 to the robot No. 2 is calculated from the determined three position data on the world coordinate system of the robot No. 1 and three position data on the world coordinate system of No. 2. Similarly, each transformation matrix is determined, and is stored in the nonvolatile memory of each robot controller. 
     Next, combinations of robots to be synchronously operated for cooperation are determined, and a master robot and one or more slave robots in the combination are determined. FIG. 4 shows an example of the combinations. In the first combination, all of four robots cooperate in synchronism with the robot No. 1 used as a master robot and other robots used as slave robots. In the second combination, the robot No. 1 and the robot No. 2 cooperate in synchronism with the robot No. 1 as a master robot and the robot No. 2 as a slave robot. In the third combination, a synchronously cooperative operation is performed in the combination of the robot No. 3 as a master robot and the robot No. 4 as a slave robot. In the fourth combination, a synchronously cooperative operation is performed by the combination of the robot No. 1 as a master robot and the robot number No. 3 as a slave robot. 
     The robots that are not specified as a master robot or slave robots may be used as normal robots, that is, they are operable independently while the master robot and the slave robot of each combination perform the synchronously cooperative operation. For example, in the second combination, the robots No. 3 and No. 4 can be used as the normal robots, and in the third combination, the robots No. 1 and No. 2 can be used as the normal robots. In the fourth combination, the robots No. 2 and No. 4 can be used as the normal robots. 
     In each combination of the robots to be operated in synchronously cooperation, one robot is selected to be a master robot, and one or more robots are selected to be slave robots among the rest of the robots connected by the communication line. 
     After a combination in which a synchronously cooperative operation is performed is determined, a combination pattern is set. In this example, the combination pattern is set in the master robot controller. The combination pattern may be set in the slave robot controller. In the above-described combinations, since the robot No. 1 is the master robot in the combination numbers 1, 2 and 4, the robot number No. 1 is stored as the master robot and the robot numbers No. 2, No. 3 and No. 4 are stored as the slave robots as a link pattern  1  in the nonvolatile memory  13  of the robot controller No. 1, as shown in FIG.  5 . As a link pattern  2 , the robot number No. 1 is stored as the master robot and the robot number No. 2 is stored as the slave robot. Further, as a link pattern  2 , the robot number No. 1 is stored as the master robot and the robot number No. 3 is stored as the slave robot. 
     Similarly, in the robot controller No. 3, as shown in FIG. 6, according to the third combination the robot number No. 3 is stored as the master robot and the robot number No. 4 is stored as the slave robot as a link pattern  1 . The controller for the specified master robot will be referred to as a master robot controller, and the controller for the specified slave robot will be referred to as a slave robot controller. 
     A program according to the operation sequence is set for the controller of each robot. For example, as shown in FIG. 7, first, each of the robots No. 1 to No. 4 is operated independently, and then all the robots No. 1 to No. 4 are operated in synchronous cooperation by the first combination. After this operation is finished, the robots No. 1 and No. 2 are operated in synchronous cooperation according to the second combination, and simultaneously the robots No. 3 and No. 4 are operated in synchronous cooperation according to the third combination. Finally, the robots No. 1 and No. 3 are operated in synchronous cooperation according to the third combination and the robots No. 2 and No. 4 are operated independently. 
     So as to achieve the above sequence of operations, operation programs are set and stored in the nonvolatile memory  13  of each robot controller in the order as shown in FIG.  8 . In the following description, a program for operating a robot independently will be referred to as a normal program, a program for a master robot for performing a synchronously cooperative operation will be referred to as a master program, and a program to be executed by a slave robot will be referred to as a slave program. 
     The program sequence to be set and stored in the robot controller No. 1 is in the order of the normal program, the master program for synchronously cooperative operation according to the first combination (link pattern  1 ), the master program for synchronously cooperative operation according to the second combination (link pattern  2 ), and the master program for synchronously cooperative operation according to the fourth combination (link pattern  3 ). 
     Also, the program sequence to be set and stored in the robot controller No. 2 is in the order of the normal program, the slave program for synchronously cooperative operation according to the first combination (link pattern  1 ), the slave program for synchronously cooperative operation according to the second combination (link pattern  2 ), and the normal program. 
     In the robot controller No. 3, the programs are set in the order of the normal program, the slave program for synchronously cooperative operation according to the first combination, the master program for synchronously cooperative operation according to the third combination, and the slave program for synchronously cooperative operation according to the fourth combination. In the robot controller No. 4, the programs are set and stored in the order of the normal program, the slave program for synchronously cooperative operation according to the first combination, the slave program for synchronously cooperative operation of the third combination (link pattern  1  set in the robot controller No. 3), and the normal program. 
     In each of the normal program, master program, and slave program, information as to which the program is a normal program, master program, or slave program is stored as an attribute or a program command at the head thereof. 
     Thus, after each program is stored in the nonvolatile memory of each robot controller, the program is started to be executed. Then, the processor  10  of each robot controller  1  starts processing shown in a flowchart of FIGS. 9 to  14 . 
     First, the stored program is read (Step S 1 ), and it is determined whether the read program is a normal program or not (Step S 2 ). In the above-described example, since each robot reads a normal program as shown in FIG. 8, the procedure proceeds to Step S 3 , where the next program line is read, and then it is determined whether the line is present or not (Step S 4 ). If the line is present, the motion start position (present position) on that line is deducted from the teaching target position (TCP position) programmed on that line to determine a distance of motion, and further it is divided by the operation velocity at which the distance of motion is taught to determine a motion time. Also, the motion time is divided by the computation cycle for interpolation to determine the number of interpolation points (Step S 5 ). 
     Next, an index i is set at “0”, and it is determined whether or not the index i is smaller than the number of interpolation points determined in Step S 5  (Step S 7 ). If the index i is smaller than the number of interpolation points, a value obtained by multiplying a value (i+1), which is obtained by adding “1” to the index i, by a value obtained by dividing the distance of motion determined in Step S 5  by the number of interpolation points is added to the motion start position on that line, by which interpolation position data is determined (Step S 8 ). 
     A motion amount (incremental amount) of each axis is determined based on this interpolation data (Step S 9 ), the motion amount of each axis is subjected to acceleration/deceleration processing (Step S 10 ), and a command is issued to a motor (Step S 11 ). Specifically, a motion command value of each axis, which has been subjected to acceleration/deceleration processing, is output to the axis control section  14  of the robot, loop control for position, velocity, current, etc. is carried out, and a servomotor for each axis of the robot mechanism section  2  is driven via the servo amplifier  17 . 
     Next, the index i is increased by “1” (Step S 12 ), and the control returns to Step S 7  to repeatedly execute the processing in Steps S 7  through S 12  until the index i reaches the number of interpolation points. When the index i reaches the number of interpolation points, the control goes from Step S 7  to Step S 3  where the next program line is read. The processing in Step S 3  and the following steps is executed repeatedly until the read line becomes absent. If the line becomes absent, the processing of this normal program is completed. 
     Then, the next program is read, and it is determined whether the program is a normal program or not (Steps S 1  and S 2 ). In the example shown in FIG. 8, the master program is read for the robot No. 1, and the slave program is read for other robots. Therefore, the control goes from Step S 2  to Step S 13 , where it is determined whether the read program is a master program or not. For the robot No. 1, which is a master robot, since the master program is read, the processing in Steps S 15  through S 34  is started. For other robots, which are slave robots, the control goes from Step S 13  to Step S 37 , where it is determined whether or not a notice of execution start preparation completion has been received from the master robot. 
     The processor  10  of the controller (as a master robot controller) of the robot No. 1 as a master robot outputs a signal for informing the execution of the master program to an operator of the robot control system (Step S 14 ), and reads link pattern information from the link pattern number set in the program (Step S 15 ). In the above-described example, the link pattern  1  is read. The notice of execution start preparation completion of the master program is issued to the slave robot stored in the link pattern corresponding to the read link pattern information via the communication line (Step S 16 ), and it is determined whether or not notices of execution start preparation completion have been received from all notified slave robots (Step S 17 ). The processing in Steps S 16  and S 17  is executed repeatedly until the notices are received. 
     On the other hand, the processor of the slave robot controller outputs a signal for informing the execution of the slave program to the operator of the robot control system (Step S 36 ), and determines whether or not a notice of execution start preparation completion has been received from the master robot (Step S 37 ). If the notice has been received, the number of the master robot that has received this notice of execution start preparation completion is stored in the nonvolatile memory  13  (Step S 38 ), and a notice of execution start preparation completion of slave robot is issued to the stored master robot via the signal line (Step S 39 ). The processing in Steps S 39  and S 40  is executed repeatedly until an execution start command is received from the stored master robot. 
     Specifically, the notice of execution start preparation completion is exchanged between the master robot and the slave robot. After the master robot receives the notice of execution start preparation completion from all the slave robots (Step S 17 ), the execution start command is issued to all the slave robots (Step S 17 ). 
     When the normal and independent operation of each robot is first performed and then the synchronously cooperative operation is performed with all robots as shown in FIG. 8, even if the master robot finishes the execution of normal program and reads the next master program, the synchronously cooperative operation is not started until the notices of execution start preparation completion are received from all the slave robots. Also, unless the slave robot finishes the execution of normal program, which is a previous independent operation, the slave robot does not perform the processing in Step S 37 , and naturally, it does not give the notice of execution start preparation completion in Step S 39 . Therefore, the next synchronously cooperative operation is not executed until all the robots finish the processing of independent and normal program. 
     Inversely, even when the precessing of normal program of the master robot becomes latest, the notice of execution start preparation completion is not sent from the master robot to each of the slave robots, so that the next synchronously cooperative operation is not executed until the master robot finishes the processing of normal program and the normal operation of all the robots is finished. 
     When for the robots in the link pattern in which the synchronously cooperative operation is executed, the operations of all the robots that have been performed before the execution of synchronously cooperative operation have been finished, and the master robot has received the notice of execution start preparation completion from all the slave robots (in this case, robots No. 2 to No. 4) in the link pattern in Step S 17 , the processor of the master robot issues the execution start command to the slave robots in the link pattern (Step S 17 ). The processor of the master robot stores the present position at this time in the nonvolatile memory  13  as a synchronously cooperative operation start position (Step S 19 ). Then, the next line of program is read, and the processing in Steps S 20  through S 24 , which is the same as the above-described processing in Steps S 3  through S 7 . Specifically, if a programmed line is present, the distance of motion, the motion time, and the number of interpolation points are determined, and the index i is set at “0”. If the index i is smaller than the number of interpolation points, the processing in Step S 25 , which is the same as the above-described processing in Step S 8 , is executed to determine the interpolation position data. That is, the interpolation position data is determined by performing the following computation. 
     
       
         Interpolation position data=motion start position of that line+(distance of motion÷number of interpolation points)×(i+1) 
       
     
     The processor of the master robot sends the stored synchronously cooperative operation start position of the master robot and the interpolation position data determined in Step S 25  to all the slave robots in the link pattern via the communication lines (Step S 26 ), determines the motion amount on each axis based on the interpolation position data determined in Step S 25 , which is the same processing as that in Steps S 9 , S 10 , and S 11 , and performs acceleration/deceleration processing to give a command to the motor (Steps S 27 , S 28 , and S 29 ). Subsequently, the master robot waits until a notice of interpolation position data receipt completion is sent from all the slave robot in the link pattern (Step S 30 ). 
     On the other hand, when the slave robot receives, in Step S 40 , the execution start command issued by the processor of the master robot in the processing in Step S 17 , the processor of the slave robot executes the same processing as that in Steps S 20  through S 24 . Specifically, the next line of the slave program is read, and if the line is present, the distance of motion, the motion time, and the number of interpolation points by this line are determined, the index i is set at “0”, and it is determined whether or not the index i is smaller than the number of interpolation points (Steps S 41  through S 45 ). If the index i is smaller than the number of interpolation points, the same processing as the above-described processing in Steps S 8  and S 25  is performed. Specifically, a value obtained by multiplying a value obtained by adding 1 to the index i by a value obtained by dividing the distance of motion determined in Step S 43  by the number of interpolation points is added to the motion start position on that line, by which the interpolation position data is obtained (Step S 46 ). 
     Then, the slave robot waits until the interpolation position data and the synchronously cooperative operation start position data from the master robot stored in Step S 38  are received (Step S 47 ). If the received interpolation position data is not the data from the stored master robot (Step S 48 ), the slave robot issues an alarm and stops (Step S 49 ). On the other hand, if the interpolation position data and the synchronously cooperative operation start position data issued in Step S 26  by the stored master robot are received, the processor of the slave robot determines a transformation matrix to the motion amount of slave robot corresponding to the motion amount of master robot from the received synchronously cooperative operation start position data and interpolation position data (Step S 50 ), and determines the corrected interpolation position data of slave robot to which the motion amount of master robot is added based on the determined transformation matrix and the interpolation position data of slave robot determined in Step S 46  (Step S 51 ). 
     A method for determining the corrected interpolation position data of slave robot to which the motion amount of master robot is added will be described with reference to FIG.  15 . 
     P 0 : an arbitrary position in the space 
     P 1 : an arbitrary position in the space, which is different from P 0   
     P 0 s: a position at which P 0  is viewed from the world coordinate system of slave robot 
     P 1 s: a position at which P 1  is viewed from the world coordinate system of slave robot 
     P 0 m: a position at which P 0  is viewed from the world coordinate system of master robot 
     P 1 m: a position at which P 1  is viewed from the world coordinate system of master robot 
     Tm-s: a transformation matrix in the case where the world coordinate system of master robot is viewed from the world coordinate system of slave robot 
     T 0 s- 1 s: a transformation matrix from P 0 s to P 1 s in the world coordinate system of slave robot in the case of being viewed from a slave robot 
     
       
         P 1 s=T 0 s- 1 s|P 0 s  (1) 
       
     
     
       
         P 1 s=Tm-s|P 1 m  (2) 
       
     
     
       
         P 0 s=Tm-s|P 0 m  (3) 
       
     
      From Equations (1), (2) and (3), 
      Tm-s|P 1 m=T 0 s- 1 s|Tm-s|P 0 m  (4) 
      Therefore, 
     
       
         T 0 s- 1 s=Tm-s|P 1 m|INV(Tm-s|P 0 m)  (5) 
       
     
     where, INV means an inverse matrix. 
     In Equation (5), Tm-s is a transformation matrix in the case where the world coordinate system of master robot is viewed from the world coordinate system of slave robot (in the case where the master robot is the robot No. 1 and the slave robot is the robot No. 2, this transformation matrix is T 1-2 ), and it is set and stored in the nonvolatile memory of the slave robot by the calibration made first. Also, by making the calculation in Equation (5) taking P 0 m as the synchronously cooperative operation start position sent from the master robot and P 1 m as the master robot interpolation position sent from the master robot, the transformation matrix T 0 s- 1 s for determining the motion amount in the world coordinate system of slave robot corresponding to the motion amount of master robot can be determined. 
     As shown in the following equation, by multiplying the determined transformation matrix T 0 s- 1 s by the interpolation position data of slave robot determined in Step S 46 , the interpolation position data of slave robot which the motion amount of master robot is reflected on (added to) can be obtained. 
     Interpolation position data of slave robot on which motion amount of master robot is reflected=T 0 s- 1 s| interpolation position data of slave robot 
     Based on the interpolation position data thus corrected, the motion amount on each axis is determined (Step S 52 ), acceleration/deceleration processing is performed (Step S 53 ), and a command is issued to the motor (Step S 54 ). Then, a notice of interpolation position data receipt is issued to the stored master robot (Step S 55 ), the index i is increased by “1” (Step S 56 ), and the control returns to Step S 45 . 
     The processing in Steps S 45  through S 56  is executed repeatedly until the index i reaches the number of interpolation points. 
     On the other hand, if the master robot determines in Step S 30  that the master robot has received the notice of interpolation position data receipt issued by the processor of each slave robot in the processing in Step S 55  from all the slave robots, the index i is increased by “1” (Step S 31 ), and the control returns to Step S 24 . The processing in Steps S 24  through S 31  is executed repeatedly until the index i reaches the number of interpolation points. 
     If the index i reaches the number of interpolation points, the control goes from Step S 24  to Step S 20 , and the processing in Step S 20  and the following steps is executed. 
     On the other hand, the controller of the slave robot also executes the processing in Steps S 45  through S 56  repeatedly. If the index i reaches the number of interpolation points, the control goes from Step S 45  to Step S 41 , and the processing in Step S 41  and the following steps is executed. 
     Thus, the controllers of the master robot and slave robot execute the above-described processing repeatedly until the line is read from the master program and slave program. When a line to be read becomes absent, the procedure for the master robot proceeds from the processing in Steps S 21  to the processing in Step S 32 . Also, the procedure for the slave robot proceeds from the processing in Steps S 42  to the processing in Step S 57 . 
     It is assumed that the line to be read from the master program become absent for the master robot earlier than for the slave robot and the procedure of the processor of the master robot proceeds to Step S 32  earlier than that of the slave robot. In this case, the processor of the master robot sends the latest position interpolation data determined in Step S 25 , stored in a register, and the stored synchronously or cooperative operation start position data to the slave robot via the communication line (Step S 32 ), and determines whether or not a notice of completion has been sent from all the slave robots (Step S 33 ). The processor of the master robot executes the processing in Steps S 32  and S 33  repeatedly until the notice of completion has been sent from all the slave robots, and continues to send the finally sent interpolation position data and synchronously cooperative operation start position data. Specifically, although the operation of the master robot is stopping, the finally sent interpolation position data and synchronously cooperative operation start position data are sent continuously to the slave robot. 
     On the other hand, the slave robot executes the processing in Steps S 41  through S 56  as long as a command line is read from the slave program. In this case, since the data received in Step S 47  are the interpolation position data and synchronously cooperative operation start position data that were finally sent from the master robot, the transformation matrix determined by the processing in Step S 50  is the same. 
     After the operation of the master robot is finished, the slave robot makes the same correction (amount) (Step S 51 ), and is driven based on the slave program. When a line to be commanded becomes absent in the slave program, the procedure for the slave robot proceeds to Step S 57 , where the notice of completion is issued to the master robot via the communication line, and then determines whether or not a completion command has been sent from the master robot (Step S 58 ). If the completion command has not been sent, the distance of motion of the latest line, determined in Step S 43 , is divided by the number of interpolation points, the resultant value is multiplied by the number of interpolation points indicated by the index i, and the obtained value is added to the motion start position of the latest line to determine the interpolation position data (Step S 59 ). Specifically, this interpolation position data is the final position, and is determined finally by the processing in Step S 46  of the latest line. This data is the same as the interpolation position data stored in the register, so that it need not be determined by performing calculations again and can be obtained merely by reading the value stored in the register. 
     Then, the processing in Steps S 60  through S 67 , which is the same as the processing in Steps S 47  through S 55 , is executed. The interpolation position data determined in Step S 59  is the same as the interpolation position data determined in Step S 46  in the latest line, and for the transformation matrix determined in Step S 63 , the synchronously cooperative operation start position data and interpolation position data sent from the master robot are not changed. Therefore, this correction (amount) is the same as the correction (amount) determined finally in the latest line. As a result, the corrected interpolation position data determined in Step S 64  is the same as the latest interpolation position data determined in Step S 51  in the latest line. As a result, the motion amount (incremental amount) on each axis becomes “0”, and no command is issued to the motor, so that the robot becomes in a stopped state. The processing in Steps S 57  through S 67  is executed repeatedly until the completion command is sent from the master robot. If the completion command is sent from the master robot, the processing of this slave program ends. 
     On the other hand, when the notice of completion is received from all the slave robots (Step S 33 ), the processor of the master robot issues the completion command to all the slave robots (Step S 33 ), and turns off the outputted signal for informing the completion of the master program to the operator (Step S 35 ). Upon receipt of this completion command, as described above, the slave robot stops its operation, and this processing for synchronously cooperative operation ends. 
     In contrast with the above, when the slave robot finishes the processing of the slave program earlier than the master robot, the processor of the master robot executes the processing in Steps S 20  through S 31  repeatedly, and continues to send the synchronously cooperative operation start position and the interpolation position data to the slave robot in Step S 26 . The procedure for the slave robot proceeds from Step S 42  to Step S 57 , and the processing in Steps S 57  through S 67  is executed repeatedly. In this case, the interpolation position data determined in Step S 59  is, as described above, the latest interpolation position data in the latest line of the slave program and the final command position. For this interpolation position data, by the synchronously cooperative operation start position data and interpolation position data sent from the master robot, the interpolation position data corrected by using the transformation matrix determined in Step S 63  is determined, and further the motion amount on each axis is determined, the acceleration/deceleration processing is performed, and the motor for each axis is driven (Steps S 64  through S 67 ). 
     Then, the execution of the master program is also completed and the procedure proceeds from Step S 21  to Step S 32 . When the master robot controller receives the notice of completion from all the slave robot controllers (Step S 33 ), it issues the notice of completion to all the slave robot controllers (Step S 34 ), turns off the outputted signal for informing the completion of the master program to the operator (Step S 35 ), and stops the operation of the master robot. Upon receipt of this completion command (Step S 59 ), the slave robot also stops its operation. 
     Next, in the case where the programs are stored in each robot as shown in FIG. 8, the master program is read in the robot controller NO. 1 and the slave program is read in the robot controller No. 2 according to the second combination, to execute the above-described processing for synchronously cooperative operation with the robot No. 1 as a master robot and the robot No. 2 as a slave robot. As a result, the robots No. 1 and No. 2 are operated in synchronous cooperation. Parallelly with the above, the master program is read in the robot controller NO. 3 and the slave program is read in the robot controller No. 4 according to the third combination, to execute the above-described processing for synchronously cooperative operation with the robot No. 3 as a master robot and the robot No. 4 as a slave robot, substantially simultaneously with the synchronously cooperative operation of the robots Nos. 1 and 2. 
     Further, when the synchronously cooperative operations of the robots No. 1 and No. 2 and the robots No. 3 and No. 4 are finished, in the example shown in FIG. 8, the robots No. 1 and No. 3 perform the synchronously cooperative operation and the robots No. 2 and No. 3 perform the normal and independent operation by the respective normal programs. 
     In the above-described embodiment, the combination of robots operating in synchronous cooperation is set in the master robot as a link pattern number, and the program for performing the synchronously cooperative operation is set in each robot. However, the configuration may be such that the master program and the robot number executing this master program and each slave program and the robot number executing the slave program have been programmed in advance, this program is input in any robot controller, by this robot controller, the master program is sent to the controller of a specified robot and each slave program is sent to the controller of each specified robot via a communication line, and at the time when the sending is finished, start is effected, by which the processing shown in FIGS. 9 to  14  is started by each robot controller. 
     According to the present invention, a synchronously cooperative operation can be executed between robots selected from a plurality of robots connected by communication lines, and other robots that do not perform the synchronously cooperative operation can execute an independent operation. Therefore, highly efficient work can be performed. Also, the combination of robots can be changed according to the object to be worked to perform a synchronously cooperative operation, so that the range of the object capable of being worked is widen, and optimum and efficient work can be executed.