Robot system

Abstract

Robot system (1), comprising: a robot (2) comprising a plurality of drive shafts (10); and a control device (4) designed to control the robot (2), wherein each drive shaft (10) comprises a drive unit designed to cause a second element (B) to operate with respect to a first element (A), the drive unit comprises a motor (11), a braking mechanism (C) designed to brake a rotation of the motor (11) and supply the rotation to the first element (A) and the second element (B), and an input-side detector (E1) designed to detect a rotational angular position of the motor (11), at least one drive unit comprises an output-side detector (E2) designed to detect an operating position of the second element (B) with respect to the first element (A), and the control device (4) controls the motor (11) in such a way that each drive shaft (10) is caused to operate with high responsiveness on the basis of the rotational angle position of the motor (11) detected by the input-side detector (E1) and the operating position detected by the output-side detector (E2), wherein the response sensitivity is determined by control gains of the drive shafts (10).

Description

[0001] The present disclosure relates to a robot system.

[0002] At a joint portion of a robot, the rotation of a motor is decelerated using a deceleration mechanism to drive an output shaft. In a case where a pulse encoder attached to the motor is used to detect a rotation angle to control the position of the output shaft, positional deviation may occur due to backlash and distortion of the deceleration mechanism, or the like, and it may not be possible to improve positioning accuracy. In such a case, it has been known to dispose another position detection sensor on the output shaft side to improve the positioning accuracy of the output shaft (see, for example, JP 2019-000948 A).

[0003] DE 10 2016 014 155 B4 discloses a system comprising a machine tool and a robot.

[0004] Furthermore, DE 10 2014 225 537 B4 describes, among other things, a robot, a robot control method, and a program that controls the driving of a joint of a robot arm. The robot comprises a robot arm with multiple joints and an end effector attached to one end of the robot arm; and a control unit configured to control an operation of the robot.

[0005] Furthermore, US 2018 / 0147724 A1 (corresponding to US 10,434,647 B2) discloses a robot control device, a robot control method, and a gripping device. The robot control device is used for a robot arm that includes a joint and a motor for rotating the joint.

[0006] Furthermore, US 2016 / 0008983 A1 discloses a control method for a robot device and a robot device.

[0007] In addition, US 8,231,117 B2 discloses a robot system that uses a robot. PATENT LITERATURE JP 2019-000948 A DE 10 2016 014 155 B4 DE 10 2014 225 537 B4 US 2018 / 0147724 A1 US 10,434,647 B2 US 2016 / 0008983 A1 US 8,231,117 B2

[0008] In a case where position information detected by the position detection sensor on the output shaft side is used and each shaft of the robot is operated using the position of the output shaft as a direct control variable, a delay in the response of the output shaft may occur due to gear backlash and the like on the deceleration mechanism, so it may not be possible to set a large control gain and may cause responsiveness issues. It has been desirable to make the output shaft operate quickly and shorten the time required to complete positioning.

[0009] According to one aspect of the present disclosure, a robot system is provided, comprising: a robot comprising a plurality of drive shafts; and a controller configured to control the robot, wherein each drive shaft comprises a drive unit configured to cause a second element to operate with respect to a first element, the drive unit comprising a motor, a deceleration mechanism configured to decelerate rotation of the motor and supply the rotation to the first element and the second element, and an input-side detector configured to detect a rotational angular position of the motor, at least one drive unit comprising an output-side detector configured to detect an operating position of the second element with respect to the first element, and the controller controls the motor in such a way,that each drive shaft with high responsiveness is caused to operate with priority based on the rotational angular position of the motor detected by the input-side detector and the operating position detected by the output-side detector, the responsiveness being determined by control gains of the drive shafts.

[0010] According to another aspect of the present disclosure, a robot system is provided, comprising: a robot including at least one drive shaft; an external device including at least one drive shaft; and a control device configured to control the robot and the external device;wherein each drive shaft comprises a drive unit configured to cause a second element to operate with respect to a first element, the drive unit comprising a motor, a deceleration mechanism configured to decelerate rotation of the motor and supply the rotation to the first element and the second element, and an input-side detector configured to detect a rotational angular position of the motor, at least one drive unit comprising an output-side detector configured to detect an operating position of the second element with respect to the first element, and the control device controls the motor such that each drive shaft is caused to operate with high responsiveness with priority based on the rotational angular position of the motor detected by the input-side detector and the operating position detected by the output-side detector.

[0011] Advantageous embodiments of the robot system are described in the subclaims. Fig. 1 is an overall configuration diagram illustrating a robot system according to an embodiment of the present invention. Fig. 2 is a diagram for explaining a connection of a robot main body and drive shafts of a work table with a control device in the robot system in Fig. 1. Fig. 3 is an overall configuration diagram for explaining an ideal case where only the robot main body is caused to operate to achieve a positioning target position in the robot system in Fig. 1 to reach exactly. Fig. 4 is an overall configuration diagram for explaining a new set operation target position in the robot system of Fig. 1. Fig. Fig. 5 is an overall configuration diagram for explaining a case where the robot main body and the work table are caused to move in the direction shown in Fig. 4 set new operating target position to work with the robot system in Fig. 1. Fig. 6 is an overall configuration diagram showing a modified example of the robot system in Fig. 1 illustrates.

[0012] A robot system 1 according to an embodiment of the present disclosure will be described below with reference to the drawings.

[0013] The robot system 1 according to the embodiment comprises a 6-axis articulated robot 2 comprising six drive shafts 10, a work table (external device) 3 capable of changing the position and posture of a mounted workpiece W, and a control device 4 adapted to control the robot 2 and the work table 3, as shown, for example, in Fig. 1 is illustrated.

[0014] The robot 2 includes a base 5 placed on a floor surface F, and a rotary body 6 supported by the base 5 so as to be able to rotate about a vertical first axial line J1. The robot 2 also includes a first arm 7 supported by the rotary body 6 so as to be able to rotate about a horizontal second axial line J2, and a second arm 8 supported by the first arm 7 so as to be able to rotate about a third axial line J3 parallel to the second axial line J2. Further, the robot 2 includes a three-axis wrist unit 9 supported at a distal end of the second arm 8.

[0015] The wrist unit 9 includes a first wrist element 9a supported by the second arm 8 so as to be able to rotate about a fourth axial line J4 that perpendicularly intersects the third axial line J3, a second wrist element 9b supported by the first wrist element 9a so as to be able to rotate about a fifth axial line J5 that is parallel to the third axial line J3 and perpendicularly intersects the fourth axial line J4, and a third wrist element 9c supported by the second wrist element 9b so as to be able to rotate about a sixth axial line J6 that perpendicularly intersects the fifth axial line J5.

[0016] In the embodiment, the six drive shafts 10 constitute a mechanism designed to drive rotation of the rotating body 6 about the first axial line J1 with respect to the base 5, a mechanism designed to drive rotation of the first arm 7 about the second axial line J2 with respect to the rotating body 6, a mechanism designed to drive rotation of the second arm 8 about the third axial line J3 with respect to the first arm 7, a mechanism designed to drive rotation of the first wrist element 9a about the fourth axial line J4 with respect to the second arm 8, a mechanism designed to drive rotation of the second wrist element 9b about the fifth axial line J5 with respect to the first wrist element 9a, and a mechanism designed toto drive rotation of the third wrist element 9c about the sixth axial line J6 with respect to the second wrist element 9b.

[0017] A tool S is attached to a distal end of the wrist unit 9. In the embodiment, a needle-shaped member for indicating a positioning target position is used as the workpiece W, and a needle-shaped member for indicating a distal tool end point is used as the tool S for simplifying the description.

[0018] Each drive shaft 10 comprises a drive unit designed to cause a second element B to operate with respect to a first element A, as shown in Fig. 2. The drive unit comprises a motor 11 to be driven and a braking mechanism C designed to brake rotation of the motor 11 and transmit the rotation to the second element B. The second element B here corresponds, with respect to the first element A, to the rotating body 6 with respect to the base 5, the first arm 7 with respect to the rotating body 6, and the second arm 8 with respect to the first arm 7.

[0019] The drive unit also includes a first encoder (input-side detector) E1 capable of detecting the rotational angular position of the motor 11. Furthermore, the drive unit includes a second encoder (output-side detector) E2 configured to detect a rotational angular position (working position) of the second element B relative to the first element A on each drive shaft 10.

[0020] The work table 3 comprises a base 12 and a placement platform 13 which is driven to rotate about a horizontal axial line G1 with respect to the base 12 and to which the workpiece W is attached, as shown in Fig. 1. The work table 3 is also provided with a motor 11 designed to cause the placement platform 13 to pivot with respect to the base 12, and a pulse generator (input-side detector) E3 designed to detect the rotational angular position of the motor 11.

[0021] As in Fig. As illustrated in Figure 2, the rotational angle position of the motor 11 of each drive shaft 10 of the robot 2, detected by the first pulse generator E1 of the drive unit, and the rotational angle position (working position) of the second element B relative to the first element A, detected by the second pulse generator E2, are fed to the control device 4. The rotational angle position of the motor 11, detected by the pulse generator E3 of the clamping table 3, is also fed to the control device 4.

[0022] The control device 4 calculates an operation control signal for the motor 11 of each drive shaft 10 based on the input rotational angle position of the motor 11 of each drive shaft 10 of the robot 2, the rotational angle position of the second element B with respect to the first element A, and the rotational angle position of the motor 11 of the work table 3, and outputs the operation control signal to the motor 11. In a case where the motor 11 is controlled only based on the rotational angle position of the motor 11 detected by the first pulse generator E1 of each drive shaft 10, it is not possible to position the remote tool end of the robot 2 at a positioning target position with high accuracy due to influences such as gear backlash of the deceleration mechanism C. As shown in Fig. 3 is illustrated in a prominent manner, for example, the dot-dash line represents the robot 2 in a state where the robot 2 is positioned at the positioning target position, while the solid line represents the robot 2 in a state where the robot 2 deviates from the positioning target position.

[0023] In this case, since the rotation angle position detected by the first encoder E1 has reached the rotation angle target position, no further corrective action is performed, and the deviation between the positioning target position and the current position remains. On the other hand, the rotation angle position of the second element B relative to the first element A detected by the second encoder E2 directly represents the current position of each drive shaft 10 of the robot 2.

[0024] Therefore, the control device 4 controls the motor 11 of each drive shaft 10 to set the deviation between the target rotation angle position of each drive shaft 10 and the rotation angle position of the second element B relative to the first element A detected by the second encoder E2 to zero. In this case, a control gain of the motor 11 in the control device 4 is different for each drive shaft 10, and some drive shafts 10 have large control gains, while other drive shafts 10 have small control gains.

[0025] For example, the rigidity of the drive shaft 10 of the work table 3 is higher than the rigidity of each drive shaft 10 of the robot 2, and the work table 3 has a larger control gain for controlling the motor 11 in the embodiment. Since the drive shaft 10 with a larger control gain can operate with steeper acceleration and deceleration, it is possible to extend the time during which high-speed operation is performed and thereby shorten the time to reach the target position. Thus, the controller 4 performs control such that the drive shafts 10 of the robot and the drive shaft 10 of the work table 3 are caused to operate with higher priority in descending order from the larger control gains.

[0026] In other words, the control device 4 carries out control of the drive shafts 10 of both the robot and the work table 3 in descending order from greater responsiveness, that is, from the larger control gains, without only controlling the robot 2, in order to cause the robot 2 to reach the target position, as shown by the chain line in Fig. 3. In this way, the control device 4 arranges the robot 2 and the clamping table 3 at positions where the remote tool end point can coincide with the positioning target position of the workpiece W, as shown by the dot-dash line in Fig. 5 is illustrated.

[0027] In particular, the control device 4 sets a new work target position on a work locus of the positioning target position passed through the clamping table 3, as shown in Fig. 4. The new work target position is determined based on the responsiveness of each drive shaft 10, that is, how large the control gains are. For example, the high-rigidity work table 3 operates for a longer time than the low-rigidity drive shafts 10 of the robot 2 to cause the workpiece W to reach the work target position. Then, the controller 4 causes the workpiece W and the tool S to approach each other by causing the robot and the work table 3 to operate toward the new work target position, as shown in Fig. 5 is illustrated.

[0028] In this way, according to the robot system 1 in the embodiment, the drive shaft 10 is made to operate with high responsiveness in the process of correcting a positional deviation due to gear backlash or the like of the deceleration mechanism C of the robot 2 with high priority in a case where the work table 3 comprising one or more drive shafts 10 is used together with the robot 2 comprising six drive shafts 10. Thus, there is an advantage in that it is possible to perform high-speed and accurate positioning.

[0029] Although in a case where the number of arrangement patterns of the tool S with respect to the workpiece W is one, the posture of the robot 2 is determined once according to the rotational angle position of the drive shaft 10 of the work table 3, there are various methods in which the remote tool end point reaches the positioning target position of the workpiece w. Therefore, it is only necessary for the controller 4 to set the new work target position at a position where the drive shaft 10 of the work table 3 is caused to work as long as possible.

[0030] Furthermore, although the robot system 1 comprising the six-shaft articulated robot 2 and the single-shaft work table 3 has been exemplified in the embodiment, the present disclosure is not limited thereto. For example, a traveling device 15 adapted to cause the entire robot 2 to move, as shown in Fig. 6, or a carriage not illustrated may be used as an external device instead of the single-shaft work table 3. In this case, the work table 3 not including a drive shaft 10 may be used as the work table 3 on which the workpiece W is mounted.

[0031] Further, in the embodiment, although each drive shaft 10 is caused to operate with priority with high responsiveness, it is only necessary to cause each drive shaft 10 to operate such that the time for completing positioning is minimized according to the amount of correction of the position and the shaft speed of each drive shaft 10.

[0032] Furthermore, the six-shaft articulated robot was exemplified as a robot, but the shape of the robot is not limited to this. Any robot can be used, such as a horizontally articulated robot, a cylindrical coordinate system robot, or a direct-drive robot.

[0033] Although the six-shaft robot has been exemplified as a robot, a robot having any number of drive shafts (for example, seven or more shafts) may be employed. Furthermore, an external device having any number of drive shafts may be employed. Instead of the robot system comprising the robot having six or more shafts and the external device having any number of drive shafts, a system comprising a robot having seven or more shafts may be employed. It is only necessary for the controller to cause each drive shaft with high responsiveness to operate with priority, similar to the above description.

[0034] Although in the embodiment, the second encoders are arranged between the base and the rotary body, between the rotary body and the first arm, and between the first arm and the second arm, the second encoder need not be provided on a drive shaft, which is unlikely to cause problems such as gear backlash. Additionally, the second encoder can be arranged for at least one of the three drive shafts of the wrist unit. The second encoder can also be arranged on the work table. LIST OF REFERENCE SYMBOLS 1 robot system 2 robots 3 Clamping table (external device) 4 Control device 10 Drive shaft 11 Engine 15 Driving device (external device) A First Element B Second element C Braking mechanism E1 First pulse generator (input-side detector) E2 Second pulse generator (output-side detector) W workpiece

Claims

[1] Robot system (1), comprising: a robot (2) comprising a plurality of drive shafts (10); and a control device (4) designed to control the robot (2), wherein each drive shaft (10) comprises a drive unit designed to cause a second element (B) to operate with respect to a first element (A), the drive unit comprises a motor (11), a braking mechanism (C) designed to brake a rotation of the motor (11) and supply the rotation to the first element (A) and the second element (B), and an input-side detector (E1) designed to detect a rotational angular position of the motor (11), at least one drive unit comprises an output-side detector (E2) designed to detect an operating position of the second element (B) with respect to the first element (A), and the control device (4) controls the motor (11) in such a way that each drive shaft (10) is caused to operate with high responsiveness on the basis of the rotational angle position of the motor (11) detected by the input-side detector (E1) and the operating position detected by the output-side detector (E2), wherein the response sensitivity is determined by control gains of the drive shafts (10). [2] Robot system (1), comprising: a robot comprising at least one drive shaft (10); an external device (3, 15) comprising at least one drive shaft (10); and a control device (4) designed to control the robot (2) and the external device (3, 15); wherein each drive shaft (10) comprises a drive unit designed to cause a second element (B) to operate with respect to a first element (A), the drive unit comprises a motor (11), a braking mechanism (C) designed to brake a rotation of the motor (11) and supply the rotation to the first element (A) and the second element (B), and an input-side detector (E1) designed to detect a rotational angular position of the motor (11), at least one drive unit comprises an output-side detector (E2) designed to detect an operating position of the second element (B) with respect to the first element (A), and the control device (4) controls the motor (11) in such a way that each drive shaft (10) is caused to operate with high responsiveness with priority on the basis of the rotational angular position of the motor (11) detected by the input-side detector (E1) and the operating position detected by the output-side detector (E2). [3] Robot system (1) according to claim 2, wherein the response sensitivity is determined by control gains of the drive shafts (10). [4] Robot system (1) according to one of claims 1 to 3, wherein the control device (4) controls the motor (11) of the drive unit to set deviations between a working target position of the second element (B) with respect to the first element (A) and the operating position detected by the output-side detector (E2) to zero. [5] The robot system (1) according to claim 2, wherein the control means (4) sets a new work target position at which each drive shaft (10) with high responsiveness is caused to operate with priority while maintaining a required relative positional relationship between the robot (2) and a work target at a work target position of each drive shaft (10), and controls the motor (11) of the drive unit to set a deviation between the new work target position and the operating position to zero. [6] Robot system (1) according to claim 5, wherein the external device (3, 15) is a work table (3) adapted to position a workpiece (W) at a working position of the robot (2). [7] Robot system (1) according to claim 5, wherein the external device (3, 15) is a driving device (15) designed to cause the robot (2) mounted thereon to move.

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