JP2009142904A - Robot control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot control device which reduces an influence of hysteresis and improves the accuracy of a parameter and the accuracy of control. <P>SOLUTION: The control device 12 creates calibration data for use in controlling a robot 11. The control device 12 acquires normal direction data and negative direction data by moving an end effector 17 from a first location in a normal direction and moving the end effector 17 from a second location in a negative direction to an objective point as an arrival point of the end effector 17. Then the control device 12 creates the calibration data, based on the acquired normal direction data and the negative direction data, and a DH parameter set in the robot 11. Thus by moving the end effector 17 from the first location and the second location that are symmetric to the objective point to acquire the normal direction data and the negative direction data, the influence of the hysteresis caused by difference in operational direction on the created calibration data, is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a robot control apparatus, and more particularly to a robot control apparatus that applies a parameter that takes hysteresis into consideration.

In an industrial robot system, it is necessary to identify various parameters with high accuracy in order to increase control accuracy during operation. The robot includes, for example, an actuator that generates a driving force, an encoder that detects the position of the actuator, a link mechanism that transmits the driving force of the actuator, and the like. Therefore, slight errors occurring in these actuators, encoders, links, and the like are corrected using parameters (see Patent Document 1).
JP-A-6-304893

  In the case of Patent Document 1, an arbitrary number of points are extracted from an arbitrary motion region assumed by the robot, and the end effector is moved to the arbitrary point. In Patent Literature 1, calibration is executed based on data obtained by repeating the movement of the end effector to an arbitrary point a plurality of times, and various parameters are acquired. However, hysteresis exists in the actuator and the link mechanism that constitute the robot. Therefore, the position of the end effector is slightly deviated depending on the movement direction of the end effector, the load applied to the end effector, the moving speed of the end effector, or the acceleration of the end effector. As a result, the accuracy of parameters obtained as a result of calibration may deteriorate, and the control accuracy may be insufficient.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a robot control device that reduces the influence of hysteresis and improves the accuracy of parameters and the accuracy of control.

  In the first aspect of the present invention, the end effector coordinates and the rotation angle of the shaft are acquired by moving the end effector from the positive direction and the negative direction with respect to the target point set by the target point setting means. That is, the positive direction movement detection means moves the end effector from the first position to the target point, and acquires the positive end effector coordinates of the end effector and the positive rotation angle of each axis when the target point is reached. On the other hand, the negative direction movement detection means moves the end effector from the second position on the opposite side of the first position across the target point to the target point, and the negative end of the end effector when the target point is reached. The effector coordinates and their negative rotation angles are acquired. In this way, by moving the end effector from the first position to the positive direction and from the second position to the negative direction with respect to the target point, the end effector coordinates and the rotation angles of the respective axes while moving from different directions. Is acquired. Therefore, calibration that cancels the influence of hysteresis caused by the difference in movement direction is executed. Therefore, the influence of hysteresis can be reduced, and the accuracy of parameters and the accuracy of control can be improved.

  In the invention according to claim 2, the movement of the end effector in the positive direction from the first position to the target point and the movement of the end effector in the negative direction from the second position to the target point are repeated for a plurality of different target points. Running. Then, calibration is executed from each end effector coordinate, each rotation angle of each axis, and DH parameters obtained repeatedly. Therefore, it is possible to reduce the influence of slight deviation for each movement and the influence of hysteresis, and improve the accuracy of parameters and the accuracy of control.

  In the invention according to claim 3, a plurality of DH parameters are set according to the load applied to the end effector and the acceleration of the end effector. Therefore, even when the hysteresis varies depending on the load applied to the end effector and the acceleration of the end effector, an appropriate specific DH parameter is extracted according to the load applied to the end effector and the acceleration of the end effector. Therefore, it is possible to reduce the influence of hysteresis that changes depending on the load and acceleration, and it is possible to improve the accuracy of parameters and the accuracy of control.

  According to the fourth aspect of the present invention, after the operation in one step of the robot stops, the control of the robot by the specific DH parameter is switched. The robot may change its load and acceleration during operation. In this case, if the DH parameter is switched together with the switching of the conditions, there is a risk of causing a shift in the robot operation. Therefore, the DH parameter is not switched until the operation in one step is stopped in the robot. Accordingly, it is possible to reduce the deviation of the operation during the operation of the robot.

Hereinafter, an embodiment of a robot control apparatus according to the present invention will be described with reference to the drawings.
1 and 2 show a robot system to which the robot control apparatus according to the present embodiment is applied. FIG. 1 is a block diagram showing the configuration of the robot system. FIG. 2 is a schematic diagram showing the configuration of the robot system. The robot system 10 includes a robot 11 and a control device 12. The robot 11 is a robot having an arbitrary configuration, for example, for assembling parts or for inspecting parts. The control device 12 is connected to a teaching pendant 13 constituting an operation pendant as a peripheral device, a personal computer 14 for program input, and the like.

  The robot 11 is configured as a six-axis vertical articulated robot, for example. As is well known, the robot 11 has an arm 16 that is driven by a driving force from a servo motor 15 that is an actuator or the like. The arm 16 has an end effector 17 at the tip. For example, when parts are transported or assembled by the robot 11, a hand for holding these parts is used as the end effector 17. In addition, for example, when a part 11 is inspected by the robot 11, a camera for photographing a target part is used as the end effector 17. Thus, the end effector 17 can be arbitrarily selected according to the process of applying the robot 11. Between the servo motor 15 and the end effector 17 at the tip of the arm 16, a driving force transmission mechanism such as a speed reduction mechanism or a link (not shown) is provided. As a result, the end effector 17 provided at the tip of the arm 16 is driven by the driving force from the servo motor 15. The robot 11 and the control device 12 are connected by a connection cable 18. Accordingly, the servo motor 15 that drives each axis of the robot 11 and the end effector 17 that performs the work are controlled by the control device 12.

  The teaching pendant 13 is configured, for example, in such a size that the user can carry it or carry it in his hand. The teaching pendant 13 is formed in a thin, substantially rectangular box shape, for example. The teaching pendant 13 has a display part 21 made of, for example, a liquid crystal display at the center of the surface part. Various screens are displayed on the display unit 21. The display unit 21 is configured with a touch panel. Further, the teaching pendant 13 is provided with various key switches 22 around the display unit 21. The touch panel and the key switch 22 constitute a key operation unit 23 for inputting various instructions to the control device 12.

  Inside the teaching pendant 13, a control circuit 24 and an interface (not shown) are provided. The control circuit 24 is mainly composed of a microcomputer. The teaching pendant 13 performs high-speed data transfer with the control device 12 via the interface. The teaching pendant 13 is connected to the control device 12 via a cable 25. An operation signal or the like input from the key operation unit 23 of the teaching pendant 13 is transmitted from the teaching pendant 13 to the control device 12 via the cable 25. Further, the control device 12 supplies driving power to the teaching pendant 13 together with a control signal and a display signal.

  The user can execute various functions such as operation and setting of the robot 11 using the teaching pendant 13 described above. Specifically, the user can call a preset program of the robot 11 by operating the key operation unit 23 to execute activation of the robot 11 or setting of various parameters. In addition, various teaching operations can be executed by operating the robot 11 by manual operation. At this time, a desired screen such as a menu screen, a setting input screen, and a status display screen is displayed on the display unit 21 as necessary.

  A general-purpose notebook computer or the like is applied to the personal computer 14. By executing the programming software on the personal computer 14, the user can create a robot program describing the operation procedure of the robot 11 according to the application. In this case, the user can create an operation program for the robot 11 relatively easily by combining package commands or adding corrections according to the application executed by the robot 11. The personal computer 14 is connected to the control device 12 via a cable 26. The operation program of the robot 11 created by the personal computer 14 is input from the personal computer 14 to the control device 12 via the cable 26.

  In the control device 12, a control unit 31 is incorporated in a box-shaped frame. The control unit 31 is mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The control unit 31 receives each axis of the robot 11 via the servo control unit 32 based on an operation program of the robot 11 input and stored in advance, various data and parameters, an operation signal from the teaching pendant 13, and the like. The servo motor 15 is driven. Thereby, the control device 12 controls the operation of the robot 11.

In addition to the above configuration, the control device 12 includes a storage unit 34, a target point setting unit 35, a positive direction movement detection unit 36, a negative direction movement detection unit 37, and a DH parameter extraction unit 38. The storage unit 34 includes a nonvolatile storage element such as an EPPROM, an HDD, and the like. Further, the storage unit 34 may be configured by a ROM and a RAM configuring the control unit 31. The storage unit 34 stores DH parameters of the robot 11. The DH parameter may be stored in advance in the storage unit 34 as data unique to the robot 11, or may be appropriately acquired according to a change in accuracy of the robot 11 over time and stored in the storage unit 34. A plurality of DH parameters are set according to the operating conditions of the end effector 17 such as a load applied to the end effector 17 or an acceleration when the end effector 17 moves. The operation accuracy of the robot 11 varies depending on the load applied to the end effector 17 and the movement acceleration of the end effector 17. Therefore, the DH parameter is acquired in accordance with various loads assumed as the operation of the robot 11, movement acceleration, and the like, and is stored in the storage unit 34.
The target point setting unit 35 sets a target point set in the movable area of the robot 11. This target point is a point to which the end effector 17 is intended to move when the robot 11 is operated. That is, the end effector 17 of the robot 11 moves toward this target point.

  When the robot 11 is operated and the end effector 17 is moved to the target point set by the target point setting unit 35, the forward direction movement detection unit 36 acquires the position and posture of the robot 11 at the target point. Specifically, the forward direction movement detection unit 36 moves the end effector 17 from the preset first position to the target point. The first position P1 is set at a position different from the target point Pg as shown in FIG. 3, and the end effector 17 starts to move. The forward direction movement detection unit 36 moves the end effector 17 from the first position P1 to the target point Pg. Then, when the end effector 17 reaches the target point, the forward direction movement detection unit 36 acquires the coordinates of the end effector 17 and the rotation angles of the respective axes constituting the robot 11. When the end effector 17 is moved from the first position P1 to the target point Pg, the positive direction movement detection unit 36 acquires the coordinates of the end effector 17 at the target point Pg as the positive end effector coordinates. Further, when the end effector 17 is moved from the first position P1 to the target point Pg, the positive direction movement detection unit 36 acquires the rotation angle of each axis constituting the robot 11 at the target point Pg as the positive rotation angle. In the case of this embodiment, since the robot 11 is a six-axis type, the forward direction movement detection unit 36 detects all rotation angles of the six axes. The direction in which the end effector 17 moves by the positive direction movement detector 36, that is, the direction of movement from the first position P1 to the target point Pg is the positive direction in the direction of movement of the end effector 17.

  When the robot 11 is actuated to move the end effector 17 from the preset second position to the target point Pg, the negative direction movement detection unit 37 acquires the position and posture of the robot 11 at the target point Pg. To do. As shown in FIG. 3, the second position P2 is set to a position different from the target point Pg and the first position P1, and the end effector 17 starts to move. The end effector 17 is rotationally moved about a fixed axis Pv supported by each axis of the robot 11 and serving as a center of movement. The second position P2 is provided at a position symmetrical to the first position P1 across the target point Pg with the virtual straight line L connecting the fixed axis Pv and the target point Pg as an axis of symmetry.

  The end effector 17 of the robot 11 can move in three dimensions. On the other hand, even if the robot 11 is movable in three dimensions, when the two points of the target point Pg and the first position P1 are extracted from the movable region, the target point Pg and the first position P1 are on the same virtual plane. To position. A virtual straight line L connecting the fixed axis Pv and the target point Pg is also located on this virtual plane. Therefore, the second position P2 is also located on the same virtual plane as the target point Pg, the first position P1, and the virtual straight line L.

  The negative direction movement detection unit 37 moves the end effector 17 from the second position P2 to the target point Pg. Then, when the end effector 17 reaches the target point Pg, the negative direction movement detection unit 37 acquires the coordinates of the end effector 17 and the rotation angles of the respective axes constituting the robot 11. When the end effector 17 is moved from the second position P2 to the target point Pg, the negative direction movement detection unit 37 acquires the coordinates of the end effector 17 at the target point Pg as negative end effector coordinates. Further, when the end effector 17 is moved from the second position P2 to the target point Pg, the negative direction movement detection unit 37 acquires the rotation angle of each axis constituting the robot 11 at the target point Pg as a negative rotation angle. The direction in which the end effector 17 moves by the negative direction movement detection unit 37, that is, the direction of movement from the second position P2 to the target point Pg is the negative direction in the direction of movement of the end effector 17.

  The positive direction movement detection unit 36 and the negative direction movement detection unit 37 acquire, for example, the following parameters as parameters for detecting the coordinates of the end effector 17 of the robot 11 and the rotation angle of each axis. The positive direction movement detection unit 36 and the negative direction movement detection unit 37 include, for example, the rotation angle θi of the rotation axis i constituting each axis of the robot 11, the link Li driven by the rotation axis i, the rotation axis i, and the rotation axis i + 1. All or part of the link length ai, the rotation angle αi around the xi axis from the z-axis of the link Li to the z-axis of the link Li + 1, and the offset amount Δθi of the rotation angle θi are acquired as parameters.

  The control unit 31 stores the positive end effector coordinates and the positive rotation angle acquired by the positive direction movement detection unit 36, the negative end effector coordinates and the negative rotation angle acquired by the negative direction movement detection unit 37, and the storage unit 34. The calibration of the robot 11 is executed based on the DH parameter. The DH parameter extraction unit 38 extracts a DH parameter suitable for the load and movement acceleration of the end effector 17 from the DH parameter stored in the storage unit 34 as a specific DH parameter. The DH parameter extraction unit 38 extracts, as a specific DH parameter, a DH parameter suitable for the application in accordance with a robot application according to an operation program of the robot 11 input from the personal computer 14 or the like, for example.

Next, calibration by the control device 12 having the above configuration will be described with reference to FIG.
The target point setting unit 35 sets a measurement position for performing calibration of the robot 11, that is, a target point Pg (S101). The target point Pg is a representative measurement point that can acquire parameters applicable to all the operation regions of the robot 11. The target point setting unit 35 sets at least one target point Pg. Note that the target point setting unit 35 may set, as the target point, a measurement point at which a parameter applicable only to a part of the motion in the motion region of the robot 11 can be acquired.

  When the target point Pg is set, the forward direction movement detection unit 36 sets the first position P1, and moves the end effector 17 to the first position P1 (S102). The forward direction movement detection unit 36 sets a first position P1 different from the target point Pg. The distance between the target point Pg and the first position P1 may be set in advance as a constant value, or may be set as a value that changes arbitrarily for each target point Pg. When the first position P1 is set, the forward direction movement detection unit 36 moves the end effector 17 of the robot 11 to the first position P1. The forward direction movement detection unit 36 outputs a drive signal to the servo motor 15 via the servo control unit 32 to operate the robot 11. The robot 11 operates according to the rotation amount of the servo motor 15, and the end effector 17 provided at the tip of the arm 16 moves.

  When the end effector 17 moves to the first position P1, the forward direction movement detector 36 moves the end effector 17 from the first position P1 to the target point Pg (S103). The forward direction movement detection unit 36 sets a command position and orientation or a command angle, which is a control signal for moving the end effector 17 to the target point Pg, and outputs the command position and the command angle from the servo control unit 32 to the servo motor 15. The servo motor 15 is driven based on a control signal including a command position and orientation or a command angle output from the servo control unit 32. As a result, the end effector 17 moves from the first position P1 to the target point Pg.

  When the end effector 17 moves from the first position P1 to the target point Pg, the forward direction movement detection unit 36 acquires the actual position and the actual posture of the end effector 17 (S104). The end effector 17 measures the actual position and orientation when moving to the target point Pg by an external device (not shown) such as a laser measuring instrument. The forward direction movement detection unit 36 acquires the position and orientation of the end effector 17 measured by the external device as the actual position and orientation of the end effector 17 from the external device.

  Further, the forward direction movement detection unit 36 acquires a command position and posture or a command angle set for operating the end effector 17 to the target point Pg (S105). The command position and orientation or command angle is set when the end effector 17 is moved from the first position P1 to the target point Pg in step S103 described above. Therefore, the forward direction movement detection unit 36 acquires the command position and posture or the command angle set in step S103.

  The forward direction movement detection unit 36 determines the end effector 17 based on the actual position and orientation of the end effector 17 acquired from the external device in step S104 and the command position and orientation or command angle of the end effector 17 acquired in step S105. The positive end effector coordinates indicating the coordinates and the positive rotation angle indicating the rotation angle in each axis of the robot 11 are calculated. Then, the positive direction movement detection unit 36 stores the calculated positive end effector coordinates and positive rotation angle in the storage unit 34 as positive direction data (S106).

  When the positive direction movement detection unit 36 completes the acquisition of the positive direction data during the movement of the end effector 17 in the positive direction in steps S102 to S106, the negative direction movement detection unit 37 sets the second position P2, and ends The effector 17 is moved to the second position P2 (S107). The negative direction movement detection unit 37 sets a second position P2 different from the target point Pg and the first position P1. As described above, the second position P2 is set at a position symmetrical to the first position P1 with the virtual straight line L shown in FIG. 3 as the axis of symmetry. Therefore, the distance from the target point Pg to the second position P2 is the same as the distance from the target point Pg to the first position P1. When the second position P2 is set, the negative direction movement detection unit 37 moves the end effector 17 of the robot 11 to the second position P2. The negative direction movement detection unit 37 outputs a drive signal from the servo control unit 32 to the servo motor 15 to operate the robot 11. The robot 11 operates according to the rotation amount of the servo motor 15, and the end effector 17 provided at the tip of the arm 16 moves.

  When the end effector 17 moves to the second position P2, the negative direction movement detector 37 moves the end effector 17 from the second position P2 to the target point Pg (S108). The negative direction movement detection unit 37 sets a command position and posture or a command angle, which is a control signal for moving the end effector 17 to the target point Pg, and outputs the command position and the command angle from the servo control unit 32 to the servo motor 15. The servo motor 15 is driven based on a control signal including a command position and orientation or a command angle output from the servo control unit 32. As a result, the end effector 17 moves from the second position P2 to the target point Pg.

  When the end effector 17 moves from the second position P2 to the target point Pg, the negative direction movement detection unit 37 acquires the actual position and the actual posture of the end effector 17 (S109). The end effector 17 measures the actual position and orientation when the end effector 17 is moved to the target point by an external device (not shown) as in the forward movement. The negative direction movement detection unit 37 acquires the position and orientation of the end effector 17 measured by the external device as the actual position and orientation of the end effector 17 from the external device.

  Further, the negative direction movement detection unit 37 acquires a command position and posture or a command angle set for operating the end effector 17 to the target point Pg (S110). The command position and orientation or command angle is set when the end effector 17 is moved from the second position P2 to the target point Pg in step S108 described above. Therefore, the negative direction movement detection unit 37 acquires the command position and posture or the command angle set in step S108.

  The negative direction movement detection unit 37 determines the end effector 17 based on the actual position and orientation of the end effector 17 acquired from the external device in step S109 and the command position and orientation or command angle of the end effector 17 acquired in step S110. The negative end effector coordinates indicating the coordinates and the negative rotation angle indicating the rotation angle in each axis of the robot 11 are calculated. Then, the negative direction movement detection unit 37 stores the calculated negative end effector coordinates and negative rotation angle in the storage unit 34 as negative direction data.

  The control unit 31 determines whether or not the acquisition of the positive direction data by the positive direction movement detection unit 36 and the acquisition of the negative direction data by the negative direction movement detection unit 37 have been performed for n sets (n ≧ 1) set in advance. (S112). The operation of the end effector 17 is deviated between movement in the positive direction and movement in the negative direction due to hysteresis generated in the servo motor 15 and the driving force transmission mechanism of the robot 11. That is, the coordinates of the end effector 17 that are reached when operating in the positive direction from the first position P1 and the end effector 17 that is reached when operating in the negative direction from the second position P2 to the target point Pg. There is a difference between the coordinates of. This deviation not only depends on the direction of the operation of the end effector 17 but also occurs every time the operation is executed. In other words, even if the end effector 17 is moved in the same direction, a slight deviation occurs every time the operation is performed. Therefore, in order to execute calibration with higher accuracy, the control unit 31 executes n sets of acquisition of positive direction data by the positive direction movement detection unit 36 and acquisition of negative direction data by the negative direction movement detection unit 37. At this time, in order to sufficiently secure the accuracy, preferably n ≧ 50. This n can be arbitrarily set according to the accuracy required for the coordinates of the robot 11 and the end effector 17. That is, n can be reduced when the required accuracy is relatively low, and n can be increased as the required accuracy increases. Further, when the shape accuracy and assembly accuracy of the robot 11 are high, n may be small.

  If the control unit 31 determines in step S112 that acquisition of n sets of positive direction data and acquisition of negative direction data has not been completed, the process returns to step S102. Thereby, the control part 31 repeatedly performs from step S102 to step S111 until acquisition of positive direction data and negative direction data reaches n sets. On the other hand, if the control unit 31 determines in step S112 that acquisition of n sets of positive direction data and acquisition of negative direction data has been completed, has the acquisition of positive direction data and negative direction data been completed at all of the target points Pg? It is determined whether or not (S113). As described above, the target point setting unit 35 sets at least one target point Pg in the operation region of the robot 11. Therefore, the control unit 31 determines whether or not the acquisition of the positive direction data and the negative direction data has been completed for all the set target points Pg.

  If the control unit 31 determines in step S113 that the acquisition of the positive direction data and the negative direction data has not been completed for all the target points Pg, the control unit 31 returns to step S101. Thereby, the control part 31 repeatedly performs step S101 to step S112 until acquisition of the positive direction data and the negative direction data is completed for all the target points Pg. On the other hand, when determining that the acquisition of the positive direction data and the negative direction data is completed at all the target points in step S113, the control unit 31 creates calibration data (S114).

  The control unit 31 creates calibration data from the positive direction data and the negative direction data obtained by executing Step S101 to Step S113 and the DH parameter stored in the storage unit 34. This positive direction data includes a positive end effect coordinate and a positive rotation angle. Similarly, the negative direction data includes negative end effect coordinates and a negative rotation angle. At this time, the control unit 31 uses the DH parameter extraction unit 38 to extract specific DH parameters used for creating calibration data.

  When the creation of the calibration data in step S <b> 114 is completed, the control unit 31 stores the created calibration data in the storage unit 34. Then, when controlling the robot 11, the control unit 31 corrects the command value of the control signal output from the servo control unit 32 to the servo motor 15 based on the calibration data stored in the storage unit 34 (S115). That is, the control unit 31 performs control of the robot 11 using the calibration data created in step S114. Thereby, the robot 11 is controlled based on the control signal corrected by the calibration data in which the influence of hysteresis is reduced.

  As described above, in the embodiment of the present invention, the robot 11 is controlled by the control signal corrected by the calibration data. The calibration data includes positive direction data from the movement of the robot 11 from the first position P1 to the target point Pg, and negative data from the movement of the robot 11 from the second position P2 symmetrical to the first position P1 to the destination point Pg. It is created based on the direction data and DH parameters set in the robot 11. By creating calibration data using the positive direction data and the negative direction data, the influence of hysteresis due to the moving direction of the end effector 17 is reduced. That is, by combining the positive direction data and the negative direction data acquired by moving the end effector 17 from two symmetric directions, the influence of the hysteresis generated in the robot 11 on the control of the robot 11 is reduced. Therefore, the control accuracy of the robot 11 can be improved.

  In one embodiment of the present invention, the positive direction data and the negative direction data are acquired by setting the positive direction movement and the negative direction movement of the end effector 17 as one set, and the acquisition of these data is repeated n sets. Thereby, not only the influence of the hysteresis due to the moving direction of the end effector 17 but also the static deviation that differs in units of the operation position of the robot 11 is reduced in the entire operation region. Therefore, the accuracy of the calibration data can be increased, and the control accuracy of the robot 11 can be improved.

  Furthermore, in one embodiment of the present invention, a plurality of DH parameters used for creating calibration data are set according to the load applied to the end effector 17 and the movement acceleration of the end effector 17. Then, the DH parameter extraction unit 38 extracts specific DH parameters suitable for this application from a plurality of set DH parameters according to the application of the robot 11. Thereby, not only the moving direction of the end effector 17 but also optimum calibration data is created for each type of application. Therefore, the control accuracy of the robot 11 can be improved in accordance with the operation of the robot 11.

(Other embodiments)
Depending on the operation of the robot 11, two or more applications having different loads and moving accelerations may be continuous. That is, the robot 11 may continue to operate with different applied DH parameters. At this time, the control device 12 is preferably configured to switch the DH parameter to be applied after the operation of the robot 11, that is, the application completes one step. That is, the control device 12 does not change the DH parameter to be applied while a plurality of applications of the robot 11 are continuously being performed. If the DH parameter is changed during the continuous operation, the control accuracy of the robot 11 may be shifted between applications. Therefore, when the application of the robot 11 continues, the control device 12 does not switch the parameter of the DH parameter until the operation of the robot 11 completes one step. Accordingly, it is possible to reduce the deviation of the operation during the operation of the robot 11.

The block diagram which shows schematic structure of the robot system by one Embodiment of this invention. Schematic showing a robot system according to an embodiment of the present invention. The schematic diagram which shows the positional relationship of a target point, 1st position, and 2nd position in the robot system by one Embodiment of this invention. Schematic showing the flow of operation of the robot system according to one embodiment of the present invention.

Explanation of symbols

  In the drawing, 11 is a robot, 12 is a control device, 16 is an arm, 17 is an end effector, 35 is a target point setting unit (target point setting means), 36 is a positive direction movement detecting unit (positive direction movement detecting means), 37 Is a negative direction movement detection unit (negative direction movement detection unit), 38 is a parameter extraction unit (parameter extraction unit), Pg is a target point, P1 is a first position, P2 is a second position, Pv is a fixed axis, and L is a virtual A straight line is shown.

Claims (4)

A control device for a robot comprising an end effector and an arm that supports the end effector and moves with a plurality of axes as fulcrums,
Target point setting means for setting a target point in the movable region of the robot;
The end effector is moved with respect to the target point from a first position different from the target point with respect to the target point set by the target point setting means, and the coordinates of the end effector when reaching the target point are the positive end. Positive direction movement detection means for obtaining the rotation angle of the plurality of axes as a positive rotation angle as effector coordinates;
The end effector is moved from the second position symmetrical to the first position to the target point with a virtual straight line connecting the fixed axis and the target point in the movement of the end effector as the symmetry axis, and the target point is reached. Negative direction movement detection means for acquiring the coordinates of the end effector at the time as negative end effector coordinates and the rotation angles of the plurality of axes as negative rotation angles;
A robot control device comprising: A set of movement detection of the end effector is configured from the movement of the end effector from the first position to the destination point and the movement from the second position to the destination point.
For each target point set in the movable area of the robot, n sets (n> 1) of movement detection of the end effector are performed, and the obtained positive end effect coordinates, the positive rotation angle, and the negative end effect are obtained. The robot control apparatus according to claim 1, wherein the robot is calibrated based on coordinates, the negative rotation angle, and a DH parameter set in advance in the robot. A plurality of the DH parameters are set according to the load applied to the end effector and the acceleration during the movement of the end effector,
The DH parameter extracting means for extracting a specific DH parameter suitable for a load applied to the end effector and an acceleration of the end effector from a plurality of the set DH parameters. Robot controller.   4. The robot control apparatus according to claim 3, wherein the specific DH parameter extracted by the DH parameter extracting means is switched after an operation in one step is stopped in the robot.

Images