JP2013206426A - Robot control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot control device with which track error can be further reduced in the case where multiaxial synchronous operation of a robot is performed.SOLUTION: A control device 20 performs control so that multiple joints of a robot operate synchronously, by executing an operation program. A CPU 21 reads commands included in the operation program in sequence. If the read command is an operation command, the CPU 21 estimates lost motion that occurs when the previously executed operation command and the currently read operation command are executed in sequence, according to the operation commands. The CPU 21 reduces the lost motion according to the currently read operation command and the estimated lost motion, and then creates an operation pattern for allowing the multiple joints to operate synchronously and executes the created operation pattern.

Description

  The present invention relates to a robot control apparatus.

  2. Description of the Related Art Conventionally, some tables having X-axis and Y-axis feed axes add a motion command for lost motion to an electric motor when the axis movement direction is reversed (see, for example, Patent Document 1). According to the device described in Patent Document 1, it is possible to shorten the movement time corresponding to the lost motion of the electric motor when the moving direction is reversed, and to reduce the trajectory error during the multi-axis synchronous operation.

Japanese Patent Publication No. 7-19180

  However, in the thing of patent document 1, after the reversal | inversion of the moving direction of a feed shaft is instruct | indicated, the movement command for a lost motion is added with respect to an electric motor. For this reason, although the movement time for the lost motion can be shortened, there is a limit in reducing the trajectory error during the multi-axis synchronous operation.

  The present invention has been made in view of such circumstances, and a main object of the present invention is to provide a robot control device that can further reduce the trajectory error during the multi-axis synchronous operation of the robot.

  A first means is a control device that synchronously operates a plurality of joints of a robot by executing an operation program, a reading unit that sequentially reads commands included in the operation program, and a read unit that is read by the reading unit When the command is an operation command, based on the operation command executed before the operation command is read by the reading unit and the operation command read by the reading unit, the operation commands are consecutive. An estimation unit that estimates a lost motion that occurs when executed, and the lost motion is reduced based on the operation command read by the reading unit and the lost motion estimated by the estimation unit. A creation unit that creates an operation pattern for synchronously operating the plurality of joints, and the operation pattern created by the creation unit Characterized in that it comprises a an execution unit for executing.

  According to the above configuration, the commands included in the operation program are sequentially read by the reading unit. When the command read by the reading unit is an operation command, the estimation unit determines whether or not based on the operation command executed before the operation command is read by the reading unit and the operation command read by the reading unit. The lost motion that occurs when the motion command is continuously executed is estimated. Then, based on the motion command read by the reading unit and the lost motion estimated by the estimation unit, the creation unit creates a motion pattern that synchronizes the plurality of joints after reducing the lost motion.

  That is, when the command read by the reading unit is an operation command, there is no time until the next operation command is executed, and thus an operation pattern including control for reducing the lost motion is created in advance. Thereafter, the operation pattern created by the creation unit is executed by the execution unit. Therefore, the operation command is actually executed after the lost motion is reduced, and the trajectory error during the multi-axis synchronous operation of the robot can be further reduced.

  In the second means, the creation unit creates the motion pattern so that a start portion of a period in which the plurality of joints are synchronously operated overlaps an end portion of the period in which the lost motion is reduced.

  When an operation pattern including control for reducing the lost motion is created in advance, there is a concern that the timing for synchronizing the plurality of joints based on the operation command may be delayed.

  In this regard, according to the above configuration, the creation unit creates the motion pattern so that the start portion of the period in which the plurality of joints are operated synchronously overlaps the end portion of the period in which the lost motion is reduced. For this reason, the start time of the synchronous operation based on the operation command can be advanced, and the transition from the reduction of the lost motion to the synchronous operation can be smoothly performed.

  In the third means, the creation unit creates the motion pattern so as to start the synchronous motion of the plurality of joints when the lost motion is reduced to less than a predetermined amount.

  It is desirable that the lost motion be sufficiently reduced when the start timing of the synchronous operation based on the operation command is advanced.

  In this regard, according to the above-described configuration, when the lost motion is reduced to less than a predetermined amount, the creation pattern creates the motion pattern so as to start the synchronization operation of the plurality of joints. For this reason, the lost motion can be reduced to less than a predetermined amount while the start time of the synchronous operation based on the operation command is advanced.

  In the fourth means, the creation unit extends the operation time of the other joint in accordance with the operation time of the joint that takes the longest time to reduce the lost motion to less than the predetermined amount. Create an action pattern.

  According to the above configuration, the motion pattern is created so that the motion time of the other joints is extended in accordance with the motion time of the joint that takes the longest time to reduce the lost motion to less than a predetermined amount. For this reason, it is possible to minimize the time required for the control to reduce the lost motion while reliably reducing the lost motion to less than a predetermined amount.

  In the fifth means, the creation unit creates the motion pattern so that the lost motion is further reduced after the lost motion is reduced to less than the predetermined amount for the joint whose operation time is extended.

  According to the above configuration, the motion pattern is created by the creating unit so as to further reduce the lost motion after reducing the lost motion to less than a predetermined amount for the joint whose operating time is extended. That is, in a joint whose operation time is extended, after the lost motion is reduced to less than a predetermined amount, the lost motion is further reduced using the extended operation time. As a result, the trajectory error during the multi-axis synchronous operation of the robot can be further reduced.

  In a sixth means, the creation unit creates the motion pattern so as to operate the joint that takes the longest time at the maximum speed when the lost motion is reduced to less than the predetermined amount.

  According to the above configuration, when the lost motion is reduced below the predetermined amount, the motion pattern is created so that the joint that requires the longest time is operated at the maximum speed. For this reason, it is possible to further shorten the time until the lost motion is reduced to less than a predetermined amount.

  When two motion commands are executed in succession, a lost motion occurs when the motion direction of the joint is reversed. Further, the amount of lost motion can be estimated based on the backlash amount of gears meshing with each other.

  For this reason, as in the seventh means, each joint has a reduction gear having a servo motor as a drive source for operating the joint, a gear provided on the output shaft of the servo motor, and a gear meshing with the gear. The estimation unit is configured to execute a rotation direction of the servo motor when the operation command is executed before the operation command is read by the reading unit, and the operation command read by the reading unit. A joint having a rotation direction opposite to that of the servo motor is extracted, and the extracted joint is based on a backlash amount between the gear of the servo motor and the gear of the speed reducer. Thus, a configuration in which the lost motion is estimated can be employed.

  In an eighth means, the creation unit creates a speed fluctuation pattern for rotating the servo motor so as to reduce the lost motion of the joint, with respect to the joint extracted by the estimation unit and the lost motion is estimated. To do.

  According to the above configuration, a speed fluctuation pattern for rotating the servo motor is created for the joint extracted by the estimation unit and the lost motion is estimated so as to reduce the lost motion of the joint. That is, a joint that needs to reduce the lost motion is extracted, and a speed variation pattern of the servo motor that reduces the lost motion is created for the joint. Therefore, the lost motion of the target joint can be reduced.

The front view which shows the outline | summary of a robot. The circuit diagram which shows the control apparatus of a robot, and its periphery structure. The figure which shows an example of an operation | movement program. The figure which shows the other example of an operation | movement program. The flowchart which shows the process sequence of the robot operation control of 1st Embodiment. The flowchart which shows the process sequence of the speed fluctuation pattern preparation which cancels LM. The time chart which shows the speed fluctuation pattern of a 1st joint and a 2nd joint. The flowchart which shows the process sequence of the speed fluctuation pattern preparation which performs an operation command after reducing LM. The time chart which shows the speed fluctuation pattern of a 1st joint and a 2nd joint. The time chart which shows the rotation angle of a servomotor and an arm. The schematic diagram which shows the operation | movement locus | trajectory of a hand part. The time chart which shows the rotation angle of a servomotor and an arm. The schematic diagram which shows the operation | movement locus | trajectory of a hand part. The flowchart which shows the process sequence of the robot operation control of 2nd Embodiment. The time chart which shows the speed fluctuation pattern of a 2nd joint. The time chart which shows the rotation angle of a servomotor and an arm. The schematic diagram which shows the operation | movement locus | trajectory of a hand part.

(First embodiment)
Hereinafter, a first embodiment embodied in a robot system for operating a vertical articulated robot will be described with reference to the drawings. The robot of this embodiment is used in an assembly system such as a machine assembly factory as an industrial robot, for example.

  First, an outline of the robot 10 will be described with reference to FIG. As shown in the figure, the robot 10 has a first axis J1, a second axis J2, a third axis J3, a fourth axis J4, a fifth axis J5, and a sixth axis J6 as the rotation center axis of each joint. It is a 6-axis robot. The operating angle of each part in each axis is adjusted through driving of a driving source composed of a servo motor or the like and deceleration by a speed reducer or the like. For example, a wave gear type speed reducer is adopted as the speed reducer. A gear is provided on the output shaft of the servo motor, and this gear and the gear of the reduction gear are engaged with each other. Each servomotor can rotate in both forward and reverse directions, and each part operates based on the origin position by driving the motor. Each joint is provided with a bearing (bearing means) that can smoothly rotate each part about each axis.

  The robot 10 is installed on the floor, and the first axis J1 extends in the vertical direction. In the robot 10, the base 11 has a fixed portion 12 fixed to the floor or the like, and a rotating portion 13 (first rotating portion) provided above the fixed portion 12. It can be rotated in the horizontal direction around the one axis line J1. That is, the rotating portion 13 extends in the direction of the first axis J1 and is supported by the fixed portion 12 so as to be rotatable about the first axis J1.

  The lower arm 15 (second rotating portion) is coupled to be rotatable in a clockwise direction or a counterclockwise direction about a second axis J2 extending in the horizontal direction as a rotation center. That is, the lower arm 15 extends in a direction away from the second axis J2 included in the plane orthogonal to the first axis J1, and is supported by the rotating unit 13 so as to be rotatable about the second axis J2. The lower arm 15 is provided in a direction extending in the vertical direction as a basic posture.

  The upper arm 16 is coupled to the upper end portion of the lower arm 15 so as to be rotatable clockwise or counterclockwise about a third axis J3 extending in the horizontal direction. That is, the upper arm 16 extends in a direction away from the third axis J3 parallel to the second axis J2, and is supported by the lower arm 15 so as to be rotatable about the third axis J3. The upper arm 16 is provided in a direction extending in the horizontal direction as a basic posture.

  The upper arm 16 is configured to be divided into two arm portions on the support side and the distal end side, the first upper arm 16A (third rotating portion) on the support side, and the second upper arm 16B (second assembly) on the distal end side. 4 rotating parts). The second upper arm 16B is rotatable in the torsional direction with respect to the first upper arm 16A with a fourth axis J4 extending in the longitudinal direction of the upper arm 16 as a rotation center. That is, the second upper arm 16B extends in the direction of the fourth axis J4 included in the plane orthogonal to the third axis J3, and is supported by the first upper arm 16A so as to be rotatable about the fourth axis J4. .

  A wrist portion 17 (fifth rotating portion) is provided at the distal end portion of the upper arm 16 (specifically, the second upper arm 16B). The wrist portion 17 is rotatable with respect to the second upper arm 16B with the fifth axis J5 extending in the horizontal direction as the center of rotation. That is, the wrist 17 extends in a direction away from the fifth axis J5 orthogonal to the fourth axis J4, and is supported by the second upper arm 16B so as to be rotatable about the fifth axis J5.

  A hand portion 18 (sixth rotating portion) for attaching a work, a tool, or the like is provided at the distal end portion of the wrist portion 17. The hand portion 18 is rotatable in the torsional direction around the sixth axis J6 that is the center line thereof. That is, the hand portion 18 extends in the direction of the sixth axis J6 orthogonal to the fifth axis J5, and is supported by the wrist portion 17 so as to be rotatable about the sixth axis J6.

  In FIG. 2, the control apparatus 20 of the robot 10 and its periphery structure are shown. The control device 20 controls the operation of the robot 10, and includes a CPU 21, a ROM 22, a RAM 23, a drive circuit 25, a rotational position detection circuit 26, and the like. These are electrically connected to each other. The ROM 22 stores system programs and operation programs for the robot 10. The RAM 23 stores parameter values and the like when executing these programs. The CPU 21 controls the operation of the robot 10 by executing various programs based on the contents stored in the ROM 22 and RAM 23.

  In the robot 10, a servo motor 31 is provided on the front side of each joint with each axis J1 to J6 as the rotation center axis. The CPU 21 drives each servo motor 31 through the drive circuit 25. Thereby, in each joint, the back stage part rotates by the drive of the servo motor 31 provided in the front stage part.

  Each servo motor 31 is provided with a non-excitation electromagnetic brake 33 that brakes its output shaft, and an encoder 32 that outputs a pulse signal corresponding to the rotation angle (rotation position) of the output shaft.

  Each electromagnetic brake 33 brakes the output shaft of the servo motor 31 based on the elastic force of a spring or the like, and releases the braking of the output shaft based on power supply to the exciting coil. The CPU 21 drives each electromagnetic brake 33 through the drive circuit 25. The CPU 21 drives each servo motor 31 in a state where braking of the output shaft by each electromagnetic brake 33 is released.

  Each encoder 32 includes a detection element that magnetically or optically detects the rotation of the rotor formed in a predetermined pattern, and an IC that processes a signal of the detection element. Detection signals of the encoders 32 are input to the rotational position detection circuit 26, respectively. Based on the detection signal of each encoder 32, the rotational position detection circuit 26 is configured to rotate each rotational angle ( Each rotational position) is detected.

  Specifically, the rotation position detection circuit 26 includes a rotation angle (rotation position) of the rotation unit 13 with respect to the fixed unit 12, a rotation angle of the lower arm 15 with respect to the rotation unit 13, and a rotation angle of the first upper arm 16 </ b> A with respect to the lower arm 15. The rotation angle of the second upper arm 16B relative to the first upper arm 16A, the rotation angle of the wrist portion 17 relative to the second upper arm 16B, and the rotation angle of the hand portion 18 relative to the wrist portion 17 are detected, and the detected rotational position information. Is output to the CPU 21.

  Then, the CPU 21 executes an operation program to perform feedback control of the operation of each of the above parts of the robot 10 based on the rotation position information input from the rotation position detection circuit 26.

  The user of the robot 10 creates an operation program describing a command for operating the robot 10. In this operation program, each operation point (each movement destination) for moving the hand unit 18 of the robot 10 is set in order to cause the robot 10 to perform an operation. Further, it commands the movement of the hand unit 18 to each operating point, standby for the movement of the hand unit 18, and the like.

  Based on this operation program, the CPU 21 creates a speed fluctuation pattern (motion pattern) for operating each joint, and synchronizes each joint of the robot 10 with the created speed fluctuation pattern. Further, the CPU 21 creates a speed fluctuation pattern for canceling the lost motion, which will be described later, and creates a speed fluctuation pattern for executing the operation command after reducing the lost motion.

  FIG. 3 shows an example of the operation program. In this example, a standby command Delay is inserted between two movement commands Move. Specifically, in this operation program, positions P0, P1, and P2 are set as destinations. Then, after moving the hand unit 18 to the position P0, it waits for a predetermined time. Next, the hand unit 18 is moved to the position P1, and then moved to the position P2.

  FIG. 4 shows another example of the operation program. In this example, the standby command Delay is not inserted between the plurality of movement commands Move, and the movement commands Move are continuously executed. Specifically, in this operation program, positions P0, P1, and P2 are set as destinations. And the hand part 18 is moved to position P0, P1, P2 in order.

  The CPU 21 creates a speed variation pattern for operating each joint based on these operation programs. Specifically, the target rotation position of each joint for moving the hand unit 18 to the target position (movement destination) is calculated. Then, a speed variation pattern for moving each joint from the current rotational position to the target rotational position is created. Furthermore, a current value for driving each servo motor 31 is calculated based on each created speed variation pattern, and each servo motor 31 is driven with the calculated current value.

  FIG. 5 shows a processing procedure for robot operation control. This series of processing is repeatedly executed by the CPU 21 when the robot 10 is operated by the operation program.

  First, a command to be executed in the operation program is read (S11). Then, it is determined whether or not the read command is an operation command (S12). In this determination, when it is determined that the read command is not an operation command (S12: NO), the next command is read (S13). For example, in the operation program shown in FIG. 3, it is assumed that the Move p, P0 command is executed in the previous process, and the Delay 1000 command is executed in the current process. In this case, since the Delay command is not an operation command, the next Move L, P1 command is read.

  After reading the next command (S13), it is determined whether or not the next command read is an operation command (S14). In this determination, when it is determined that the next command read is not an operation command (S14: NO), the next command is read again (S13).

  On the other hand, in the above determination, when it is determined that the next command read is an operation command (S14: YES), based on the operation command read before this time and the operation command read this time, The lost motion LM generated when the operation command is continuously executed is estimated (S15). In the example shown in FIG. 3, the operations of Move p and P0 are based on the Move p and P0 operation command read in the previous process and the Move L and P1 operation commands read in the current process. The lost motion LM generated when the operation command of Move L, P1 is executed after the command is executed is estimated. Specifically, a joint is extracted in which the rotation direction of the servo motor 31 when the hand unit 18 is moved to the position P0 is opposite to the rotation direction of the servo motor 31 when the hand unit 18 is moved to the position P1. To do. For the extracted joint, the lost motion LM is estimated based on the backlash amount between the gear provided on the output shaft of the servo motor 31 of the joint and the gear of the reduction gear meshing with the gear. It is estimated that the lost motion LM does not occur for the joint that has not been extracted.

  Subsequently, a speed variation pattern for eliminating the estimated lost motion LM is created for each joint (S16).

  Specifically, as shown in FIG. 6, it is determined whether or not there is a joint that needs to eliminate the lost motion LM (S161). That is, it is determined whether or not there is a joint whose generated lost motion LM is estimated in S15. In this determination, if it is determined that there is no joint that needs to eliminate the lost motion LM (S161: NO), the process of S16 is terminated (END), and the process proceeds to S17 of FIG.

  On the other hand, in the above determination, when it is determined that there is a joint that needs to eliminate the lost motion LM (S161: YES), it is determined whether it is necessary to eliminate the lost motion LM of a plurality of joints (S162). . In this determination, when it is determined that the lost motion LM of a plurality of joints needs to be eliminated (S162: YES), a speed variation pattern of each joint that eliminates the lost motion LM is created (S163). On the other hand, in this determination, when it is determined that it is not necessary to eliminate the lost motion LM of a plurality of joints (S162: NO), a joint velocity fluctuation pattern that eliminates the lost motion LM is created (S165). Following S163 or S165, the operation time of each joint is extended until the next operation command (S164). Then, the process of S16 is terminated (END), and the process proceeds to S17 of FIG.

  For example, as shown in FIG. 7, it is assumed that the lost motion LM is eliminated at the first joint having the first axis J1 as the rotation center and the second joint having the second axis J2 as the rotation center. In this case, as shown in (a), a speed fluctuation pattern P11 that eliminates the lost motion LM1 in the first joint is created. That is, the trapezoidal area indicated by the speed variation pattern P11 corresponds to the lost motion LM1. Further, as shown in (b), a speed fluctuation pattern P21 that eliminates the lost motion LM2 in the second joint is created. That is, the trapezoidal area indicated by the speed variation pattern P21 corresponds to the lost motion LM2. The first joint and the second joint are rotated at the maximum rotation speed (speed).

  Here, in the first joint, the end time of the speed fluctuation pattern P11 coincides with the start time t14 of the speed fluctuation pattern P12 of the next operation command. On the other hand, in the second joint, the end time t12 of the speed fluctuation pattern P21 is earlier than the start time t14 of the speed fluctuation pattern P23 of the next operation command. For this reason, as shown in the speed fluctuation pattern P22, the operation time of the second joint is extended until the start time t14 of the speed fluctuation pattern P23. At this time, in (b), the area of the trapezoid indicated by the speed fluctuation pattern P22 is equal to the area of the trapezoid indicated by the speed fluctuation pattern P21, and the lost motion LM2 is also eliminated by the speed fluctuation pattern P22. For example, when it is necessary to eliminate only the lost motion LM2 of the second joint, only the speed variation pattern P22 is created.

  The speed fluctuation patterns P11 and P22 for eliminating the lost motion LM are set following the end (time 0) of the operation command (speed fluctuation pattern) executed before the current operation command. The speed fluctuation patterns P11 and P22 are set until the start of the current operation command (speed fluctuation patterns P12 and P23). That is, the speed variation patterns P11 and P22 are set over the entire period from the end of the operation command executed before the current operation command to the execution of the current operation command. Further, in the speed variation patterns P11 and P22, the time 0 at which the acceleration is started, the time t11 at which the acceleration ends, the time t13 at which the deceleration starts, and the time t14 at which the deceleration ends are the same. That is, when the lost motion LM is eliminated, a speed variation pattern for synchronously operating a plurality of joints is created.

  Returning to FIG. 5, in S <b> 17, a speed variation pattern for eliminating the lost motion LM is executed. For example, the speed variation patterns P11 and P22 of FIG. 7 are executed. Then, based on the speed variation patterns P11 and P22, a current value for driving each servo motor 31 is calculated, and each servo motor 31 is driven with the calculated current value. Note that the process of S17 is not executed for a joint for which a speed variation pattern for eliminating the lost motion LM has not been created.

  Subsequently, a speed fluctuation pattern of the next operation command read in S14 is created (S18). For example, the speed fluctuation patterns P12 and P23 in FIG. 7 and the speed fluctuation patterns of other joints are created. In these speed fluctuation patterns, the time t14 at which acceleration starts, the time t15 at which acceleration ends, the time t16 at which deceleration starts, and the time t17 at which deceleration ends are the same. That is, when the next operation command is executed, a speed variation pattern for synchronously operating a plurality of joints is created. Then, the created speed variation pattern of each joint is executed (S19). At this time, a current value for driving each servo motor 31 is calculated based on each speed variation pattern, and each servo motor 31 is driven with the calculated current value. Thereafter, the series of processes is temporarily ended (END), and when the robot 10 is continuously operated by the operation program, the process is executed again from S11.

  If it is determined in S12 that the read command is an operation command (YES), based on the operation command executed before this time and the operation command read this time, those operation commands are determined. The lost motion LM generated when is continuously executed is estimated (S20). In the example shown in FIG. 4, based on the Move p and P0 operation commands read in the previous process and the Move L and P1 operation commands read in the current process, the Move p and P0 operation commands are obtained. The lost motion LM generated when the operation command of Move L, P1 is executed after execution is estimated. The estimation method of the lost motion LM is the same as S15.

  Subsequently, for each joint, a speed variation pattern for executing the operation command read in the current process after reducing the estimated lost motion LM is created (S21).

  Specifically, as shown in FIG. 8, it is determined whether or not there is a joint that needs to reduce the lost motion LM (S211). That is, it is determined whether there is a joint whose generated lost motion LM is estimated in S20. In this determination, when it is determined that there is a joint that needs to reduce the lost motion LM (S211: YES), it is determined whether the lost motion LM of a plurality of joints needs to be reduced (S212). In this determination, when it is determined that it is necessary to reduce the lost motion LM of a plurality of joints (S212: YES), the amount of lost motion LM to be reduced for each joint is calculated (S213). A speed variation pattern of each joint that reduces the lost motion LM by the calculated amount is created (S214). Subsequently, the joint that requires the longest time to reduce the lost motion LM is extracted (S215). Then, the operation time of the other joint is extended in accordance with the joint that requires the longest time to reduce the lost motion LM (S216).

  On the other hand, in the determination of S212, when it is determined that it is not necessary to reduce the lost motion LM of a plurality of joints (NO), the amount of lost motion LM to be reduced is calculated for the joint to reduce the lost motion LM (S217). Then, a joint speed fluctuation pattern for reducing the lost motion LM is created (S218).

  If it is determined in S211 that there is no joint that needs to reduce the lost motion LM (S211: NO), a speed variation pattern of each joint is created based on the operation command read in S12. (S219). In these speed fluctuation patterns, the time to start acceleration, the time to end acceleration, the time to start deceleration, and the time to end deceleration are the same. That is, a speed variation pattern for synchronizing the plurality of joints is created. Even after S216 or S218, the process proceeds to S219, and a speed fluctuation pattern of each joint based on the motion command is created following the speed fluctuation pattern for reducing the lost motion LM. Thereafter, the process of S21 is ended (END), and the process proceeds to S22 of FIG.

  For example, as shown in FIG. 9, it is assumed that the lost motion LM is reduced at a first joint centered on the first axis J1 and a second joint centered on the second axis J2. In this case, as shown in (a), a speed fluctuation pattern P14 that eliminates the lost motion LM1 in the first joint is created. That is, the trapezoidal area indicated by the speed variation pattern P14 corresponds to the lost motion LM1. Further, as shown in (b), a speed variation pattern P24 that eliminates the lost motion LM2 in the second joint is created. That is, the trapezoidal area indicated by the speed variation pattern P24 corresponds to the lost motion LM2. The first joint and the second joint are rotated at the maximum rotation speed (speed).

  Originally, following the end (time 0) of the operation command (speed fluctuation pattern) executed before the current operation command, the speed fluctuation patterns P15 and P26 of the current operation command are set. Here, before executing the speed fluctuation patterns P15 and P26 of the current operation command, speed fluctuation patterns P14 and P25 for reducing the lost motions LM1 and LM2 are set. Therefore, when the lost motions LM1 and LM2 are reduced below a predetermined amount so as to minimize the time required for reducing the lost motions LM1 and LM2, the current operation command (speed fluctuation patterns P16 and P27) is started. Thus, the speed variation pattern P16 is set.

  Specifically, the allowable rotation error Δθ of each joint, the allowable position error ΔP of the hand unit 18 and the Jacobian J are expressed by a relational expression of Δθ = ΔP / J. Note that Jacobian J is a matrix of coefficients representing the relationship between the position of the hand unit 18 and each joint in a minute region, and is determined by the length and angle of each rotating unit and the configuration of the rotating unit. For this reason, by setting the allowable position error ΔP of the hand unit 18, the allowable rotation error Δθ of each joint can be calculated. Then, the amount of lost motion LM to be reduced at each joint is set to LM1-Δθ1 and LM2-Δθ2, respectively. Therefore, the speed variation pattern P16 is started at time t24 when the remaining lost motion LM1 becomes less than the allowable rotation error Δθ1 in the first joint. As a result, the speed fluctuation pattern P17 is set in a portion where the speed fluctuation pattern P14 and the speed fluctuation pattern P16 overlap.

  At this time, the time t22 when the lost motion LM2 is reduced below a predetermined amount (allowable rotation error Δθ2) in the second joint is the time when the lost motion LM1 is reduced below the predetermined amount (allowable rotation error Δθ1) at the first joint. It is earlier than t24. For this reason, as shown in the speed fluctuation pattern P25, the operating time of the second joint is extended after time t22, and the lost motion LM2 is further reduced. Specifically, the operation time of the second joint is extended to time t24 in accordance with the first joint that takes the longest time to reduce the lost motion LM. In (b), the area of the trapezoid shown by the speed fluctuation pattern P25 is equal to the area of the trapezoid shown by the speed fluctuation pattern P24, and the lost motion LM2 is completely eliminated by the speed fluctuation pattern P25. For example, when it is necessary to reduce only the lost motion LM2 of the second joint, the speed fluctuation pattern P27 is created so that the current operation command (speed fluctuation pattern P27) is started at time t22. In this case, the speed fluctuation pattern P14 of the first joint is not created, and only the speed fluctuation pattern P25 of the second joint is created.

  Returning to FIG. 5, in S22, after the lost motion LM is reduced, a speed fluctuation pattern for executing the operation command read in the current process is executed. For example, the speed fluctuation patterns P14, P17, and P16 (speed fluctuation patterns P25 and P27) in FIG. 9 are executed. Based on these speed fluctuation patterns, a current value for driving each servo motor 31 is calculated, and each servo motor 31 is driven with the calculated current value. Thereafter, the series of processes is temporarily ended (END), and when the robot 10 is continuously operated by the operation program, the process is executed again from S11.

  Note that the processing of S11 corresponds to the processing as a reading unit, the processing of S19 and S22 corresponds to the processing as an execution unit, the processing of S13 corresponds to the processing as a prefetching unit, and the processing of S15 and S20 is estimated. The processing in S16 and S17 corresponds to the processing as a cancellation unit, and the processing in S21 corresponds to the processing as a creation unit.

  FIG. 10 shows the effects of the processes of S15 to S19 in FIG. 5 together with the comparative example. Here, it is not necessary to eliminate the lost motion LM1 of the first joint centered on the first axis J1, and it is necessary to cancel the lost motion LM2 of the second joint centered on the second axis J2. To do. Then, the case where the lost motion LM1 is canceled before the next operation command is started at time t14 will be described.

  As shown to (a), in the 1st joint, the rotation angle of the servomotor 31 of the comparative example shown by M1 and the rotation angle of the servomotor 31 of this embodiment shown by M2 correspond. That is, in the first joint, since it is not necessary to eliminate the lost motion LM1, a speed variation pattern that eliminates the lost motion LM1 is not created.

  On the other hand, as shown in (b), in the second joint, the rotation angle of the servo motor 31 of the comparative example indicated by the broken line M1 is increased from time t14 when the next operation command is started. On the other hand, the rotation angle of the servo motor 31 of the present embodiment indicated by the solid line M2 is increased from time 0 to time t14. That is, by time t14, a speed variation pattern for eliminating the lost motion LM2 has been executed.

  For this reason, in the comparative example, the rotation angle of the arm indicated by the broken line A1 is greatly deviated from the ideal rotation angle of the arm indicated by the solid line AR. On the other hand, in this embodiment, the rotation angle of the arm indicated by the solid line A2 substantially matches the rotation angle of the ideal arm indicated by the solid line AR.

  FIG. 11 shows the trajectory of the arm of the robot 10 by the processing of S15 to S19 in FIG. 5 together with a comparative example. Here, an operation of moving the hand unit 18 in the y-axis direction while keeping the position in the x-axis direction constant is shown as an example. In the movement locus of the hand portion 18 of the comparative example indicated by the broken line H1, the position in the x-axis direction is greatly shifted. On the other hand, the position in the x-axis direction is kept constant in the operation locus of the hand unit 18 of the present embodiment indicated by the solid line H2.

  In addition, FIG. 12 shows the effect of the processing of S20 to S22 of FIG. 5 together with the comparative example. Here, it is not necessary to eliminate the lost motion LM1 of the first joint centered on the first axis J1, and it is necessary to cancel the lost motion LM2 of the second joint centered on the second axis J2. To do. Then, the case where the motion command is originally started at time 0 is shown in the case where the motion command is started at time t24 after the lost motion LM2 of the second joint is reduced to less than a predetermined amount.

  As shown in (a), in the first joint, the rotation angle of the servo motor 31 of the comparative example indicated by the broken line M1 is increased from time 0, which is the original start time of the operation command. On the other hand, the rotation angle of the servo motor 31 of the present embodiment indicated by the solid line M2 is increased from time t24, which is the time when the lost motion LM2 is reduced to a predetermined amount.

  As shown in (b), in the second joint, the rotation angle of the servo motor 31 of the comparative example indicated by the broken line M1 is increased from time 0, which is the original start time of the operation command. On the other hand, the rotation angle of the servo motor 31 of the present embodiment indicated by the solid line M2 is faster than the rotation angle of the servo motor 31 of the comparative example indicated by the broken line M1 from time 0 in order to quickly reduce the lost motion LM2. Has been increased. At time t24, the lost motion LM2 is made less than a predetermined amount.

  For this reason, in the comparative example, the rotation angle of the arm indicated by the broken line A1 is greatly deviated from the ideal rotation angle of the arm indicated by the solid line AR. On the other hand, in this embodiment, the rotation angle of the arm indicated by the solid line A2 substantially matches the rotation angle of the ideal arm indicated by the solid line AR.

  FIG. 13 shows the trajectory of the arm of the robot 10 by the processing of S20 to S22 of FIG. 5 together with a comparative example. Here, an operation of moving the hand unit 18 in the y-axis direction while keeping the position in the x-axis direction constant is shown as an example. In the movement locus of the hand portion 18 of the comparative example indicated by the broken line H1, the position in the x-axis direction is greatly shifted. On the other hand, in the operation locus of the hand unit 18 of the present embodiment indicated by the solid line H2, the positional deviation in the x-axis direction is smaller than that in the comparative example.

  The embodiment described above has the following advantages.

  The command included in the operation program is sequentially read by the reading unit (S11). Then, the commands read by the reading unit are sequentially executed by the execution unit (S19, S22). If the command read by the reading unit is not an operation command (S12: NO), the next command is read by the pre-reading unit (S13). That is, when the command read by the reading unit is, for example, Delay 1000, the process (S15 to S17) for eliminating the lost motion LM may be executed before the next operation command is executed. it can.

  Then, when the command read by the prefetch unit is an operation command, the estimation unit reads the operation command read by the read unit before the operation command is read by the prefetch unit, and the operation command read by the prefetch unit. Based on the above, the lost motion LM generated when these operation commands are continuously executed by the execution unit is estimated (S15). That is, the lost motion LM generated when the operation command is executed before the operation command read by the prefetching unit is actually executed is estimated. Here, since the robot 10 is a vertical articulated robot and can perform various operations, the state of occurrence of lost motion changes greatly. In this regard, since the lost motion LM is estimated by the estimation unit, it is possible to cope with a change in the occurrence of the lost motion in the robot 10.

  Further, the joint is operated synchronously by the canceling unit so as to cancel the lost motion LM estimated by the estimating unit until the operation command read by the prefetching unit is executed by the executing unit (S16, S17). ). Therefore, the lost motion LM can be eliminated between the end of the motion command and the execution of the next motion command, and the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced. In particular, since the robot 10 requires a quick operation, the benefit of eliminating the lost motion in advance is great.

  As shown in FIG. 7, the control for canceling the lost motion LM following the end of the operation command (time 0) read by the reading unit before the operation command is read by the prefetch unit, that is, the speed variation pattern P11, P22 is executed. For this reason, the control for eliminating the lost motion LM can be started from an early stage, and the time until the lost motion LM is eliminated can be shortened.

  The entire period from the end of the operation command read by the reading unit (time 0) before the operation command is read by the prefetching unit until the operation command read by the prefetching unit is executed by the execution unit (time 0 to 0) Over time t14), control for eliminating the lost motion LM is executed. For this reason, it is possible to ensure a long control time for eliminating the lost motion LM, and to reduce the speed at which the plurality of joints are operated synchronously as in the speed fluctuation pattern P22. As a result, the trajectory error in the control for eliminating the lost motion LM can be reduced, and the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced.

  When the lost motion LM is eliminated, the first joint that requires the longest time is operated at the maximum speed. For this reason, the time until the lost motion LM is eliminated can be further shortened. Therefore, it is effective when the waiting time until the operation command read by the prefetching unit is executed is short.

  A speed variation pattern P11 for rotating the servo motor 31 so as to eliminate the lost motions LM1 and LM2 of the first and second joints extracted from the estimation unit and estimated for the lost motion LM. , P22 are created (S16). That is, the first and second joints that need to eliminate the lost motions LM1 and LM2 are extracted, and the speed fluctuation patterns P11 and P22 of the servo motor 31 that eliminate the lost motions LM1 and LM2 for the first and second joints are extracted. Are created. And since the created speed fluctuation patterns P11 and P22 are executed, the lost motions LM1 and LM2 of the first and second joints to be processed can be eliminated.

  -When the command read by the reading unit is an operation command (S12: YES), the estimation unit executes the operation command executed before the reading unit reads the operation command and the operation command read by the reading unit. Based on the above, the lost motion LM generated when these operation commands are successively executed is estimated (S20). Then, based on the motion command read by the reading unit and the lost motion LM estimated by the estimation unit, the creation unit creates a motion pattern that causes the plurality of joints to operate synchronously after reducing the lost motion LM ( S21).

  That is, when the command read by the reading unit is an operation command, there is no time until the next operation command is executed, and thus speed fluctuation patterns P14, P17, and P16 including control for reducing the lost motion LM in advance. (P25, P27) is created. Then, the operation pattern created by the creation unit is executed by the execution unit (S22). Accordingly, the operation command is actually executed after the lost motion LM is reduced, and the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced. As a result, even in the robot 10 in which continuous motion is executed, the lost motion LM can be eliminated and the trajectory error can be further reduced.

  The operation pattern is generated by the generation unit so that the end portion of the period for reducing the lost motion LM overlaps the start portion of the period for synchronously operating a plurality of joints. That is, as shown in FIG. 9, the start portion of the speed variation pattern P16 is overlapped with the end portion of the speed variation pattern P14. For this reason, the start time of the synchronous operation (speed fluctuation pattern P16) based on the operation command can be advanced, and the lost motion LM1 can be smoothly shifted from the reduction to the synchronous operation. In particular, the robot 10 is highly effective in suppressing the execution of the next operation from being delayed.

  The speed variation patterns P16 and P27 are created by the creating unit so as to start the synchronous operation of the plurality of joints at time t24 when the lost motion LM1 is reduced to less than a predetermined amount (allowable rotation error Δθ1). For this reason, it is possible to reduce the lost motion LM1 to less than a predetermined amount while advancing the start time of the synchronous operation based on the operation command.

  The speed variation pattern P25 is created so that the operation time of the second joint is extended in accordance with the operation time of the first joint that takes the longest time to reduce the lost motion LM to less than a predetermined amount. Therefore, it is possible to minimize the time (time 0 to time t24) required for the control to reduce the lost motions LM1 and LM2 while reliably reducing the lost motion LM1 to less than a predetermined amount.

  The creation unit creates the speed fluctuation pattern P25 so that the lost motion LM2 is further reduced after being reduced to less than a predetermined amount (allowable rotation error Δθ2) for the second joint whose operation time is extended. That is, in the second joint in which the operation time is extended, after the lost motion LM2 is reduced to less than a predetermined amount, the lost motion LM2 is further reduced using the extended operation time (time t22 to time t24). . As a result, the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced.

  When the lost motion LM is reduced below a predetermined amount, an operation pattern P14 is created so that the first joint that requires the longest time is operated at the maximum speed (S21). For this reason, it is possible to further shorten the time until the lost motion LM1 is reduced to less than a predetermined amount.

  The first embodiment can be implemented with the following modifications.

  In FIG. 7, the control period for eliminating the lost motions LM1 and LM2 may be a fixed period of time until the next operation command is executed. In this case, the execution of the next motion command is executed after the execution of the previously read motion command is completed until the control to cancel the lost motion LM1, LM2 is started, or after the lost motion LM1, LM2 is resolved. Until this happens, a waiting period will occur.

  In FIG. 9, the second joint lost motion LM2 is reduced below the predetermined amount in accordance with the operation time of the first joint that takes the longest time to reduce the lost motion LM below the predetermined amount. The operation time of the two joints may be extended. That is, the speed variation pattern of the second joint may be created so that the remaining lost motion LM2 becomes the allowable rotation error Δθ2 at time t24. In this case, the rotation speed of the second joint can be further reduced.

  -The cancellation unit may synchronize multiple joints by extending the operation time of other joints in accordance with the operation time of the joint that takes the longest time to eliminate the lost motion LM. . For example, in FIG. 7, when the end time of the speed fluctuation pattern P11 of the first joint is earlier than the start time t14 of the speed fluctuation pattern P12 of the next motion command, the second joint is synchronized with the speed fluctuation pattern P11. The operating time may be extended. That is, the end time of the speed fluctuation pattern P22 of the second joint may be matched with the end time of the speed fluctuation pattern P11 of the first joint.

  According to the above configuration, a plurality of joints can be operated synchronously by extending the operation time of the second joint in accordance with the operation time of the first joint that takes the longest time to eliminate the lost motion LM. . For this reason, it is possible to minimize the time required for the control for eliminating the lost motions LM1 and LM2 while reliably eliminating the lost motions LM1 and LM2.

(Second Embodiment)
Hereinafter, a second embodiment in which the robot operation control process is partially changed will be described with reference to the drawings. In this embodiment, the processing of S20 to S22 in FIG. 5 is changed to the processing of S31 to S34 as shown in FIG. 14, and the same processing of S31 to S34 is added between S18 and S19. Yes. Since other configurations are the same as those of the first embodiment, description thereof will be omitted by giving the same reference numerals.

  If it is determined in S12 that the read command is an operation command (YES), a speed variation pattern of the read operation command is created (S31). Specifically, a speed variation pattern of each joint is created so that a plurality of joints are operated synchronously. Then, it is determined whether or not the created speed variation pattern of each joint includes a reversal pattern (speed reversal pattern) for reversing the motion direction of the joint (S32).

  For example, as shown in FIG. 15, when the rotation speed changes between positive and negative in the second joint having the second axis J2 as the rotation center, it is inverted in the speed fluctuation pattern P28 of the second joint. It is determined that the pattern (the portion from time t31 to time t32 in the dashed-dotted line portion) is included. If it is determined in S32 that the created speed fluctuation pattern of each joint includes a reversal pattern that reverses the motion direction of the joint (YES), the created speed fluctuation pattern P28 (reverse In (Pattern), the speed variation pattern P28 is corrected so as to advance the timing for starting the inversion (S33). That is, the time for starting the inversion is changed from time t31 to time t33. Specifically, the speed fluctuation pattern P28 is corrected so that the time at which the inversion is started in the speed fluctuation pattern P28 is advanced by only half the period Tr from the start of inversion in the speed fluctuation pattern P28 to the end of the inversion. .

  Returning to FIG. 14, in S34, the speed variation pattern of each joint is executed. Based on these speed fluctuation patterns, a current value for driving each servo motor 31 is calculated, and each servo motor 31 is driven with the calculated current value. In the determination of S32, if it is determined that the reversal pattern for reversing the motion direction of the joint is not included in the created speed variation pattern of each joint (NO), the speed variation created in S31. The process of S34 is executed without correcting the pattern. Thereafter, the series of processes is temporarily ended (END), and when the robot 10 is continuously operated by the operation program, the process is executed again from S11.

  Further, even after the speed fluctuation pattern of the next operation command is created in S18, the processes of S32 and S33 are executed for the created speed fluctuation pattern. Then, the speed variation pattern of each joint is executed (S19). Thereafter, the series of processes is temporarily ended (END), and when the robot 10 is continuously operated by the operation program, the process is executed again from S11.

  The process of S31 corresponds to the process as the creating unit, the process of S32 corresponds to the process as the determination unit, the process of S33 corresponds to the process as the correction unit, and the process of S34 is the process as the execution unit. It corresponds to.

  FIG. 16 shows the effect of the processes of S31 to S34 in FIG. 14 together with the comparative example. At the rotation angle of the servo motor 31 of the comparative example indicated by the broken line M1, when the operation direction of the arm of the robot 10 is started to be reversed at time t31, the rotation direction of the servo motor 31 is started to be reversed. For this reason, the rotation angle of the arm indicated by the broken line A1 is greatly deviated from the ideal rotation angle of the arm indicated by the two-dot chain line AR. On the other hand, at the rotation angle of the servo motor 31 of the present embodiment indicated by the solid line M2, the rotation direction of the servo motor 31 is changed at time t33 before starting to reverse the operation direction of the arm of the robot 10 at time t31. It is starting to flip. For this reason, the deviation between the rotation angle of the arm indicated by the solid line A2 and the ideal rotation angle of the arm indicated by the two-dot chain line AR is small.

  FIG. 17 shows the trajectory of the arm of the robot 10 by the processing of S31 to S34 in FIG. 14 together with a comparative example. Here, an operation of moving the hand unit 18 in the y-axis direction while keeping the position in the x-axis direction constant is shown as an example. In the operation locus of the hand portion 18 of the comparative example indicated by the broken line H1, the position in the x-axis direction is greatly shifted after y = 0. On the other hand, in the operation locus of the hand unit 18 of the present embodiment indicated by the solid line H2, the position in the x-axis direction is slightly deviated from slightly before to slightly after y = 0. Is also getting smaller.

  The embodiment described above has the following advantages.

  The command included in the operation program is sequentially read by the reading unit (S11). Then, based on the command read by the reading unit, the creating unit creates a speed variation pattern that causes a plurality of joints to operate synchronously (S31).

  Here, the determination unit determines whether or not the speed variation pattern created by the creation unit includes a reversal pattern (speed reversal pattern) for reversing the motion direction of the joint (S32). That is, since the lost motion LM is generated when the motion direction of the joint is reversed, it is determined whether or not the speed variation pattern includes a reverse pattern that reverses the motion direction of the joint. Then, when the determination unit determines that the reverse pattern is included (S32: YES), the correction unit generates an operation pattern generated by the generation unit so as to advance the timing of inversion in the reverse pattern. Is corrected (S33). That is, as shown in FIG. 15, the time at which inversion starts in the speed variation pattern P28 is advanced from time t31 to time t33. Thereafter, the operation pattern corrected by the correction unit is executed by the execution unit (S34).

  For this reason, the speed fluctuation pattern P28 can be corrected in advance so as to reduce the lost motion LM instead of reducing the lost motion LM after the joint is actually operated and the operation direction starts to reverse. As a result, the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced. In the robot 10, since the same operation is often repeatedly executed, when the lost motion LM is generated during the operation, there is a great advantage that the lost motion LM can be reduced every time.

  The speed fluctuation pattern P28 is corrected so as to advance the timing of inversion in the speed fluctuation pattern P28 by a half period of the period Tr from the start of inversion in the speed fluctuation pattern P28 to the end of inversion. Therefore, in FIG. 16, since the reversal pattern is set back and forth evenly when the motion direction of the joint (arm) is reversed as indicated by the solid line M2, the lost motion LM is one side of the front and rear when reversing as indicated by the solid line A2. Can be suppressed. As a result, the trajectory error during the multi-axis synchronous operation of the robot 10 can be further reduced.

  In addition, the said 2nd Embodiment can also be deform | transformed and implemented as follows.

  The timing for starting the inversion in the speed fluctuation pattern P28 is advanced by a slightly longer period or a slightly shorter period than the half of the period Tr from the start of the inversion in the speed fluctuation pattern P28 to the end of the inversion. In addition, the speed fluctuation pattern P28 can be corrected.

  The present invention is not limited to the above embodiments, and can be implemented as follows, for example.

  The robot is not limited to a vertical articulated 6-axis robot, but may be a robot with other types or number of axes such as a horizontal articulated 4 axis robot.

  The language of the operation program is not limited to the languages shown in FIGS. 3 and 4, and any program language can be adopted.

  DESCRIPTION OF SYMBOLS 10 ... Robot, 18 ... Hand part, 20 ... Control apparatus, 21 ... CPU, 31 ... Servo motor, 32 ... Encoder.

Claims (8)

A control device that synchronously operates a plurality of joints of a robot by executing an operation program,
A reading unit for sequentially reading commands included in the operation program;
When the command read by the reading unit is an operation command, based on the operation command executed before the operation command is read by the reading unit and the operation command read by the reading unit, An estimation unit that estimates a lost motion that occurs when these operation commands are continuously executed;
Based on the operation command read by the reading unit and the lost motion estimated by the estimation unit, a creation unit for creating an operation pattern for synchronously operating the plurality of joints after reducing the lost motion;
An execution unit that executes the operation pattern created by the creation unit;
A robot control device comprising:   2. The robot control device according to claim 1, wherein the creation unit creates the motion pattern such that a start portion of a period in which the plurality of joints are synchronously operated overlaps an end portion of a period in which the lost motion is reduced. .   The robot control device according to claim 2, wherein the creation unit creates the motion pattern so as to start a synchronous motion of the plurality of joints when the lost motion is reduced to less than a predetermined amount.   The creation unit creates the motion pattern so as to extend the motion time of another joint in accordance with the motion time of the joint that takes the longest time to reduce the lost motion to less than the predetermined amount. Item 4. The robot control device according to Item 3.   The robot control apparatus according to claim 4, wherein the creation unit creates the motion pattern so that the lost motion is further reduced after the lost motion is reduced to less than the predetermined amount for the joint with the extended operation time. .   The said creation part creates the said motion pattern so that the said joint which requires the longest time may be operated at the maximum speed, when reducing the said lost motion to less than the said predetermined amount. The robot control device according to item 1. Each joint is provided with a reduction gear having a servo motor as a drive source for operating the joint, a gear provided on the output shaft of the servo motor, and a gear meshing with the gear,
The estimation unit includes a rotation direction of the servo motor when the operation command is executed before the operation command is read by the reading unit, and the operation command when the operation command read by the reading unit is executed. Extracting a joint having a rotation direction opposite to the rotation direction of the servo motor, and, for the extracted joint, the lost motion based on a backlash amount between the gear of the servo motor of the joint and the gear of the speed reducer The robot control apparatus according to claim 1, wherein the controller is estimated.   The creation unit creates a speed variation pattern for rotating the servo motor so as to reduce the lost motion of the joint extracted from the estimation unit and estimated for the lost motion. Robot control device.

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