Robot system and method for controlling robot system

Abstract

A robot system (100) comprises: a robot (10) that includes a plurality of joints (13); a torque detecting unit (14) that is disposed at a prescribed joint among the plurality of joints (13) and that detects a detected torque value around a rotation axis of the prescribed joint; and a control unit (20) that performs control to acquire, as the value of an external force acting on the robot (10), a second value (Pai) obtained by converting a first value (Pi) obtained by dividing the difference between the detected torque value and a reference torque value by a radius (R) from a rotation axis (A1, A2, A3, A4, A5, A6) of the predetermined joint to a monitoring point (40) set on the surface of the robot (10), into a normal direction value on the basis of an angle (θ) formed between the direction of a tangent, at the monitoring point (40), to a circle having the radius (R) and the normal direction to the surface of the robot (10) on which the monitoring point (40) is set.

Description

ROBOT SYSTEM AND METHOD FOR CONTROLLING ROBOT SYSTEM

[0001] The present disclosure relates to a robotic system and a method for controlling a robotic system.

[0002] 2. Description of the Related Art Conventionally, a robot system has been known, and one such robot system is disclosed in Japanese Patent No. 7290472, for example.

[0003] The above-mentioned Japanese Patent No. 7290472 discloses a robot system including a robot and a control device for controlling the robot. The robot is a vertically articulated robot, and torque sensors are provided at the first to third joints counting from the base end to detect torque around the rotation axis of the joint. The control device is configured to obtain, as an external force value, a value obtained by dividing the differential torque between the torque detected by the torque sensor and a calculated torque calculated from the posture and movement of the robot by the smallest radius from the rotation axis of the joint at a position where physical contact is possible.

[0004] Patent No. 7290472

[0005] However, in the robot system described in the above-mentioned Japanese Patent No. 7290472, the external force value is obtained by dividing the differential torque by the minimum radius, so only the force in the tangential direction of the circle with the minimum radius is taken into consideration and the force in the radial direction is ignored, which poses the problem of the external force value being obtained being smaller than expected.

[0006] This disclosure has been made to solve the above-mentioned problems, and aims to provide a robot system and a control method for a robot system that can prevent external force values ​​from being acquired as being too small.

[0007] A robot system according to a first aspect of the present disclosure includes a robot including a plurality of joints, a torque detection unit disposed at a predetermined joint among the plurality of joints and configured to detect a detected torque value around a rotation axis of the predetermined joint, and a control unit configured to perform control to acquire, as an external force value acting on the robot, a second value obtained by dividing a difference between the detected torque value and a reference torque value by a radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, the first value being obtained by converting the difference between the detected torque value and a reference torque value by a radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, the second value being obtained by converting the difference between the tangent direction of a circle having the radius at the monitoring point and a normal direction to the surface of the robot on which the monitoring point is set. Note that in this specification, the term "surface of the robot" is a broad concept that includes, when the robot includes a hand that holds a workpiece, the surface of the robot hand and the surface of the workpiece held by the robot hand.

[0008] In the robot system according to the first aspect of this disclosure, as described above, a control unit is provided that performs control to acquire, as an external force value acting on the robot, a first value obtained by dividing the difference between the detected torque value and the reference torque value by the radius from the rotation axis of a predetermined joint to a monitoring point set on the robot's surface, and then converting the first value into a normal direction value based on the angle between the tangent direction at the monitoring point of a circle having the radius and the normal direction to the robot's surface where the monitoring point is set. This makes it possible to acquire an external force value that is a combination of the tangential force and the radial force at the monitoring point, preventing a situation in which only the tangential force at the monitoring point is taken into account and the radial force at the monitoring point is ignored. As a result, it is possible to avoid acquiring an external force value that is too small.

[0009] A control method for a robot system according to a second aspect of this disclosure is a control method for a robot system equipped with a robot including a plurality of joints, comprising: detecting a detected torque value around a rotation axis of a predetermined joint among the plurality of joints; and obtaining a first value obtained by dividing the difference between the detected torque value and a reference torque value by the radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, and converting the first value into a normal direction value based on the angle between the tangent direction at the monitoring point of a circle having the above-mentioned radius and the normal direction to the surface of the robot on which the monitoring point is set, as an external force value acting on the robot.

[0010] In a control method for a robot system according to a second aspect of this disclosure, as described above, a difference between a detected torque value and a reference torque value is divided by a radius from a rotation axis of a predetermined joint to a monitoring point set on the surface of the robot to obtain a first value, and the first value is converted into a normal direction value based on an angle between a tangent direction at the monitoring point of a circle having the above radius and a normal direction to the surface of the robot where the monitoring point is set, thereby obtaining, as an external force value acting on the robot. This makes it possible to obtain an external force value that is a combination of tangential and radial forces at the monitoring point, so that only the tangential force at the monitoring point is taken into account and the radial force at the monitoring point is not ignored. As a result, a control method for a robot system can be provided that can avoid obtaining an external force value that is too small.

[0011] According to the present disclosure, it is possible to avoid the external force value being acquired as being smaller than normal, as described above.

[0012] FIG. 1 is a diagram showing a robot system according to an embodiment; FIG. 2 is a block diagram showing a robot according to an embodiment; FIG. 3 is a diagram (1) for explaining acquisition of external force values ​​of a robot system according to an embodiment; FIG. 4 is a diagram (2) for explaining acquisition of external force values ​​of a robot system according to an embodiment; and FIG. 5 is a flowchart for explaining control processing related to external force values ​​of a robot system according to an embodiment.

[0013] Hereinafter, embodiments embodying the present disclosure will be described with reference to the drawings.

[0014] (Configuration of Robot System) The configuration of a robot system 100 according to one embodiment will be described with reference to Figures 1 to 4. As shown in Figure 1, the robot system 100 is a system that performs work using a robot 10. The robot system 100 includes the robot 10, a control unit 20, and an instruction unit 30.

[0015] The robot 10 is a robot that works in the same space as humans. For example, the robot 10 is a collaborative robot or a service robot. The robot 10 is used without a safety fence or the like. The robot 10 is also a six-axis vertical articulated robot. As shown in FIGS. 1 and 2 , the robot 10 includes a base 11, a plurality of links 12, a plurality of joints 13, a plurality of torque detectors 14, and a hand 15.

[0016] The base 11 is fixed to an installation surface such as a floor surface by fastening members such as bolts.

[0017] The multiple links 12 include links 12a, 12b, 12c, 12d, 12e, and 12f. The links 12a, 12b, 12c, 12d, 12e, and 12f are arranged in this order from the base end to the tip end. The multiple joints 13 include joints 13a, 13b, 13c, 13d, 13e, and 13f. The joints 13a, 13b, 13c, 13d, 13e, and 13f are arranged in this order from the base end to the tip end.

[0018] Joint 13a is disposed at the connection between base 11 and link 12a. Joint 13a is configured to rotate link 12a relative to base 11 about a rotation axis A1 in the vertical direction. Joint 13b is disposed at the connection between links 12a and 12b. Joint 13b is configured to rotate link 12b relative to link 12a about a rotation axis A2 that is perpendicular to the rotation axis A1. Joint 13c is disposed at the connection between links 12b and 12c. Joint 13c is configured to rotate link 12c relative to link 12b about a rotation axis A3 that is parallel to the rotation axis A2.

[0019] Joint 13d is disposed at the connection between link 12c and link 12d. Joint 13d is configured to rotate link 12d relative to link 12c about rotation axis A4, which is perpendicular to rotation axis A3. Joint 13e is disposed at the connection between link 12d and link 12e. Joint 13e is configured to rotate link 12e relative to link 12d about rotation axis A5, which is perpendicular to rotation axis A4. Joint 13f is disposed at the connection between link 12e and link 12f. Joint 13f is configured to rotate link 12f relative to link 12e about rotation axis A6, which is perpendicular to rotation axis A5. As a result, joint 13f is configured to rotate the hand 15 attached to link 12f relative to link 12f about rotation axis A6.

[0020] Each of the joints 13 a, 13 b, 13 c, 13 d, 13 e, and 13 f is provided with a motor 131, a reducer 132, and an encoder 133. The motor 131 is a drive source that drives the joint 13, and is configured as a servo motor. The reducer 132 is configured to reduce the rotation speed of the motor 131 and transmit the driving force of the motor 131 to the link 12. The encoder 133 is configured to output information on the rotation position of the motor 131.

[0021] The torque detection units 14 are torque sensors and are arranged at all of the joints 13. Specifically, the torque detection units 14 include torque detection units 14a, 14b, 14c, 14d, 14e, and 14f arranged at the joints 13a, 13b, 13c, 13d, 13e, and 13f, respectively.

[0022] The torque detection unit 14a is configured to detect a detected torque value around the rotation axis A1 of the joint 13a. The torque detection unit 14b is configured to detect a detected torque value around the rotation axis A2 of the joint 13b. The torque detection unit 14c is configured to detect a detected torque value around the rotation axis A3 of the joint 13c. The torque detection unit 14d is configured to detect a detected torque value around the rotation axis A4 of the joint 13d. The torque detection unit 14e is configured to detect a detected torque value around the rotation axis A5 of the joint 13e. The torque detection unit 14f is configured to detect a detected torque value around the rotation axis A6 of the joint 13f.

[0023] The hand 15 is configured to perform an operation on a workpiece. For example, the hand 15 is a hand that grips a workpiece or a hand that sucks a workpiece. The hand 15 is also called a tool or an end effector. The surface of the robot 10 includes the surface of the hand 15 and the surface of the workpiece held by the hand 15.

[0024] The control unit 20 is a robot controller. The control unit 20 is configured to control the operation of the robot 10. Specifically, the control unit 20 is configured to acquire instructions for the operation of the robot 10 from the user using the instruction unit 30, and to operate the robot 10 based on the acquired instructions. Furthermore, when the robot 10 performs a task, the robot 10 may come into contact with an object, such as a human, another robot, or a workpiece other than the workpiece to be performed, that is present in the vicinity of the robot 10, and an external force may act on the robot 10. Therefore, as described below, the control unit 20 is configured to perform control to acquire an external force value acting on the robot 10.

[0025] The teaching unit 30 is a teaching pendant and is configured to receive operations for teaching the robot 10 to operate. The teaching unit 30 includes a display unit 31 that displays information such as information related to the teaching, and an operation unit 32 that receives operations related to the teaching.

[0026] (Acquisition of External Force Value) In this embodiment, as shown in FIG. 3, the control unit 20 calculates a value P ｉ is converted into a value of the normal direction based on the angle θ between the tangent direction at the monitoring point 40 of the circle having a radius R and the normal direction to the surface of the robot 10 on which the monitoring point 40 is set. ｉ is configured to perform control to acquire the external force value acting on the robot 10. Specifically, the control unit 20 ｉ =P ｉ / cosθ, the value Pa ｉ In this embodiment, the reference torque value is a theoretical torque value. The theoretical torque value is a theoretical torque value calculated based on the position and posture of the robot 10 based on teaching, the value of the encoder 133, the link length of the robot 10, and the weight of the parts of the robot 10. Note that the value P ｉ is an example of the first value. ｉ is an example of the second value.

[0027] 3 shows an example of acquiring an external force value for the joint 13b. In this case, the control unit 20 acquires a detected torque value detected by the torque detection unit 14b, and also performs control to acquire a reference torque value for the joint 13b calculated based on the position and posture of the robot 10 based on the teachings and the value of the encoder 133. The control unit 20 then performs control to acquire a difference value between the acquired detected torque value and the reference torque value. The control unit 20 then divides the acquired difference value by the radius R from the rotation axis A2 of the joint 13b to a monitoring point 40 set on the surface of the link 12b that is rotationally moved by the joint 13b, thereby obtaining a value P ｉ Then, the control unit 20 performs control to acquire the value P based on the angle θ formed by the tangent direction at the monitoring point 40 of the circle centered on the rotation axis A2 of the joint 13b and the normal direction to the surface of the link 12b on which the monitoring point 40 is set. ｉ The value Pa ｉ That is, the control unit 20 performs control to convert Paｉ =P ｉ / cosθ, the value Pa ｉ Since 0<cosθ<1, Pa ｉ Is P ｉ In this way, the control unit 20 sets the value Pa as the external force value. ｉ The value P representing the tangential force at the monitoring point 40 is obtained. ｉ is converted based on the angle θ, the value Pa as an external force value ｉ is obtained as a result of combining the tangential and radial forces at the monitoring point 40.

[0028] While an example of acquiring an external force value for joint 13b has been described, the same applies to joints 13a, 13c, 13d, 13e, and 13f. For joint 13f, a monitoring point 40 is set on the surface of hand 15 that is rotationally moved by joint 13b. For example, if hand 15 has a suction pad, monitoring point 40 is set on the surface of the suction pad.

[0029] Furthermore, in this embodiment, the monitoring point 40 is set at an arbitrary position on the surface of the robot 10, not at a fixed position. For example, the monitoring point 40 is set at an arbitrary position specified by a user. For example, the monitoring point 40 is set at an arbitrary position before the robot 10 is shipped. For example, the monitoring point 40 is set based on a risk assessment that estimates the risk of the robot 10. For example, the monitoring point 40 is set at a position with the smallest radius R among positions on the surface of the robot 10 that can be contacted by an object that applies an external force to the robot 10, based on the risk assessment. The smaller the radius R, the larger the external force value that is acquired. Therefore, by setting the monitoring point 40 so that the radius R is smaller, it is possible to prevent the external force from being acquired as being too small.

[0030] 3 and 4, in this embodiment, the monitoring points 40 are set at a plurality of positions on the surface of the robot 10. Specifically, a monitoring point 40 is set for each movement direction of the robot 10. The control unit 20 performs control to acquire the external force value using one of the plurality of monitoring points 40 that corresponds to the movement direction of the robot 10.

[0031] FIG. 3 shows an example in which the link 12b is rotationally moved in the movement direction D1 by the joint 13b. FIG. 4 shows an example in which the link 12b is rotationally moved in the movement direction D2 by the joint 13b. The movement directions D1 and D2 are the positive and negative directions, respectively, of the rotation around the rotation axis A2 of the joint 13b. The monitoring points 40 are set at two positions: a position on the surface 12ba of the link 12b on the moving side when the link 12b is rotationally moved in the movement direction D1, and a position on the surface 12bb of the link 12b on the moving side when the link 12b is rotationally moved in the movement direction D2. When the link 12b is rotationally moved in the movement direction D1, the control unit 20 performs control to acquire the external force value using the monitoring point 40 set on the surface 12ba. When the link 12b is rotationally moved in the movement direction D2, the control unit 20 also performs control to acquire the external force value using the monitoring point 40 set on the surface 12bb.

[0032] Although the example of the monitor point 40 on the surface of the link 12b has been described, the same applies to the monitor points 40 on the surfaces of the links 12a, 12c, 12d, and 12e and the hand 15. That is, the monitor points 40 on the surfaces of the links 12a, 12c, 12d, and 12e and the hand 15 are set at two positions corresponding to the two rotation directions, the plus direction and the minus direction. A total of 12 monitor points 40 are set.

[0033] In this embodiment, the control unit 20 determines the value Pa as the external force value. ｉ exceeds the threshold T1, the value Pa ｉ The control unit 20 is configured to control the robot 10 to issue a warning that the external force value Pa has exceeded the threshold value T1, and to control the robot 10 to continue operating. ｉexceeds a threshold T2 that is greater than the threshold T1, the value Pa ｉ The control unit 100 controls the robot 10 to notify the user of an abnormality that the external force exceeds the threshold value T2, and controls the robot 10 to stop or to perform an avoidance operation. Stopping the robot 10 means stopping the operation of each joint 13 of the robot 10. Performing an avoidance operation of the robot 10 means controlling the operation of the robot 10 by driving each joint 13 of the robot 10 to avoid an increase in the external force acting on the robot 10, for example, by operating the robot 10 in a direction that reduces the external force acting on the robot 10. The threshold value T2 is determined, for example, by ISO / TS15066. The threshold value T1 is an example of a first threshold value. The threshold value T2 is an example of a predetermined threshold value and a second threshold value.

[0034] The control unit 20 determines the value Pa ｉ When issuing a warning that the value Pa has exceeded the threshold value T1, the control unit 20 is configured to perform at least one of illuminating a light emitting unit such as an LED disposed on the robot 10 and displaying a message notifying the warning on the display unit 31 of the teaching unit 30. Similarly, the control unit 20 is configured to ｉ When an abnormality is to be notified that the value of the robot 10 has exceeded the threshold value T2, the robot 10 is configured to perform at least one of the following: illuminating a light-emitting element such as an LED disposed on the robot 10; and displaying a message notifying the abnormality on the display unit 31 of the teaching unit 30.

[0035] (Control Process Related to External Force Value) The control process related to the external force value of the robot system 100 according to this embodiment will be described based on a flowchart with reference to Fig. 5. Each process in the flowchart is executed by the control unit 20.

[0036] In step S1, the difference between the detected torque value and the reference torque value is divided by the radius R from the rotation axis of the joint 13 to the monitoring point 40 set on the surface of the robot 10 to obtain a value P ｉis converted into a value of the normal direction based on the angle θ between the tangent direction at the monitoring point 40 of the circle having a radius R and the normal direction to the surface of the robot 10 on which the monitoring point 40 is set. ｉ is acquired as the external force value acting on the robot 10. Specifically, Pa ｉ =P ｉ / cosθ, the value Pa ｉ In step S1, the value Pa is obtained for each of the plurality of joints 13. ｉ is obtained.

[0037] Then, in step S2, the value Pa ｉ In step S2, it is determined whether or not the value Pa ｉ It is determined whether or not the value Pa exceeds the threshold value T1. ｉ If it is determined that the value Pa does not exceed the threshold value T1, the control process is terminated. ｉ If it is determined that exceeds the threshold value T1, the process proceeds to step S3.

[0038] Then, in step S3, the value Pa ｉ In step S3, it is determined whether or not the value Pa ｉ It is determined whether or not the value Pa exceeds the threshold value T2. ｉ If it is determined that does not exceed the threshold value T2, the process proceeds to step S4.

[0039] Then, in step S4, the value Pa ｉ A warning is given that the threshold T1 has been exceeded. For example, at least one of the following is performed: illuminating a light-emitting unit such as an LED disposed on the robot 10; and displaying a message notifying the warning on the display unit 31 of the teaching unit 30. The robot 10 continues to operate without stopping the robot 10 or performing an avoidance operation.

[0040] In step S3, the value Pa ｉ If it is determined that exceeds the threshold value T2, the process proceeds to step S5.

[0041] Then, in step S5, the value Pa ｉ The robot 10 is notified of an abnormality that the threshold T2 has exceeded the threshold T2. For example, at least one of the following is performed: illuminating a light-emitting unit such as an LED disposed on the robot 10; and displaying a message notifying the abnormality on the display unit 31 of the teaching unit 30. Also, the robot 10 is stopped, or the robot 10 is made to perform an avoidance operation.

[0042] (Effects of this embodiment) In this embodiment, as described above, the value P obtained by dividing the difference between the detected torque value and the reference torque value by the radius R from the rotation axis of the joint 13 to the monitoring point 40 set on the surface of the robot 10 is ｉ is converted into a value of the normal direction based on the angle θ between the tangent direction at the monitoring point 40 of the circle having a radius R and the normal direction to the surface of the robot 10 on which the monitoring point 40 is set. ｉ as the external force value acting on the robot 10. This makes it possible to acquire an external force value that is a combination of the tangential force and the radial force at the monitoring point 40, so that only the tangential force at the monitoring point 40 is taken into consideration and the radial force at the monitoring point 40 is not ignored. As a result, it is possible to avoid acquiring an external force value that is too small.

[0043] In this embodiment, as described above, the control unit 20 ｉ =P ｉ / cosθ, the value Pa ｉ This controls the acquisition of Pa ｉ =P ｉ By using the formula / cos θ, the external force value that is a combination of the tangential force and the radial force at the monitoring point 40 can be easily obtained.

[0044] Furthermore, in this embodiment, as described above, the monitoring point 40 is not set at a fixed position but at any position on the surface of the robot 10. This allows the monitoring point 40 to be set at any position on the surface of the robot 10, making it possible to easily set the monitoring point 40 according to the robot 10.

[0045] Furthermore, in this embodiment, as described above, the monitoring points 40 are set at a plurality of positions on the surface of the robot 10. This allows the monitoring points 40 to be set at a plurality of positions on the surface of the robot 10, making it possible to more appropriately acquire external force values ​​than when the monitoring points 40 are set at only one position on the surface of the robot 10.

[0046] Furthermore, in this embodiment, as described above, a monitoring point 40 is set for each movement direction of the robot 10, and the control unit 20 performs control to acquire external force values ​​using one of the multiple monitoring points 40 that corresponds to the movement direction of the robot 10. As a result, if the shape of the robot 10 differs for each movement direction of the robot 10, the positions at which external forces of the robot 10 are likely to act will differ for each movement direction of the robot 10. However, by acquiring external force values ​​using one of the multiple monitoring points 40 that corresponds to the movement direction of the robot 10, it is possible to acquire external force values ​​appropriately and effectively.

[0047] Furthermore, in this embodiment, as described above, the torque detection units 14 are disposed at all of the multiple joints 13. This makes it possible to detect both external forces that cannot be detected by simply disposing the torque detection units 14 at the base-end joints 13 and external forces that cannot be detected by simply disposing the torque detection units 14 at the tip-end joints 13. Therefore, when an external force acts on the robot 10, the external force acting on the robot 10 can be reliably detected. Furthermore, when the torque detection units 14 are disposed at the tip-end joints 13, the torque detection units 14 can be used not only to acquire external force values ​​but also to control the operation of the hand 15. For example, when the robot 10 performs a task using the hand 15 that requires delicate control of the amount of force applied, such as fitting a screw as a workpiece or polishing a workpiece, the operation of the hand 15 can be accurately controlled based on the detected torque value of the torque detection units 14 disposed at the tip-end joints 13.

[0048] In this embodiment, as described above, the control unit 20 determines the value Pa as the external force value. ｉ exceeds the threshold T2, the robot 10 is controlled to stop or to perform an avoidance action. In this way, when a relatively large external force acts on the robot 10, the robot 10 can be stopped or can perform an avoidance action. As a result, it is possible to prevent a large load from being applied to the object that caused the external force and came into contact with the robot 10.

[0049] In this embodiment, as described above, the control unit 20 determines the value Pa as the external force value. ｉ exceeds the threshold T2, the value Pa ｉ exceeds the threshold value T2. This allows the operator to know that a relatively large external force has acted on the robot 10, and therefore allows the operator to take appropriate action in response to the relatively large external force acting on the robot 10.

[0050] In this embodiment, as described above, the control unit 20 determines the value Pa as the external force value. ｉ exceeds the threshold T1, the value Pa ｉThe robot 10 is controlled to continue its operation by issuing a warning that the external force Pa has exceeded the threshold value T1. ｉ exceeds a threshold T2 that is greater than the threshold T1, the value Pa ｉ The system performs control to notify an operator that an abnormality has occurred, that is, that the external force has exceeded the threshold value T2, and also controls the robot 10 to stop or to perform an avoidance operation. As a result, in the case of a warning, it is possible to notify an operator that a situation that may lead to an abnormality has occurred. Furthermore, in the case of a warning, the operation of the robot 10 is continued, thereby suppressing a decrease in the availability rate of the robot 10. Furthermore, in the case of an abnormality, it is possible to notify an operator that an abnormality has occurred, thereby enabling the operator to deal with the abnormality. Furthermore, in the case of an abnormality, it is possible to stop the robot 10 or perform an avoidance operation, thereby preventing a large load from being applied to the object that caused the external force and came into contact with the robot 10.

[0051] Furthermore, in this embodiment, as described above, the robot 10 is a robot 10 that performs work in the same space as humans. Here, when the robot 10 and humans perform work in the same space, an external force may act on the robot 10 due to contact between the robot 10 and the human. Therefore, when the robot 10 is a robot 10 that performs work in the same space as humans, it is very effective to be able to avoid acquiring a small external force value.

[0052] The robot 10 includes a hand 15 that holds a workpiece, and the surface of the robot 10 includes the surface of the hand 15 and the surface of the workpiece held by the hand 15. This makes it possible to appropriately acquire an external force value when an external force acts on the surface of the hand 15 and the surface of the workpiece held by the hand 15.

[0053] (Modifications) The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above-mentioned embodiments, and further includes all modifications (modifications) within the meaning and scope equivalent to the claims.

[0054] For example, in the above embodiment, an example was shown in which the robot was a six-axis vertical articulated robot, but the present disclosure is not limited to this. In the present disclosure, the robot may be a seven-axis or eight-axis vertical articulated robot other than the six-axis. Furthermore, the robot may be a robot other than a vertical articulated robot. For example, the robot may be a horizontal articulated robot.

[0055] In addition, in the above embodiment, an example was shown in which the robot works in the same space as humans, but the present disclosure is not limited to this. In the present disclosure, the robot may be a robot other than a robot that works in the same space as humans.

[0056] In the above embodiment, an example has been described in which the control unit serving as the robot controller performs control to acquire the external force value, but the present disclosure is not limited to this. In the present disclosure, a control unit other than the robot controller may perform control to acquire the external force value.

[0057] In addition, in the above embodiment, an example was shown in which the reference torque value was a theoretical torque value, but the present disclosure is not limited to this. In the present disclosure, the reference torque value may be a torque value other than the theoretical torque value. For example, the reference torque value may be a calculated torque value calculated based on the current value of the motor of the joint.

[0058] In the above embodiment, Pa ｉ =P ｉ Although an example of obtaining an external force value using the formula Pa / cos θ has been shown, the present disclosure is not limited to this. ｉ =P ｉ The external force value may be obtained using an equation other than / cos θ.

[0059] In the above embodiment, an example is shown in which the monitoring point is set at an arbitrary position on the surface of the robot, but the present disclosure is not limited to this. In the present disclosure, the monitoring point may be set at a fixed position on the surface of the robot.

[0060] In addition, in the above embodiment, an example has been shown in which monitoring points for one joint are set at two positions on the surface of the robot, but the present disclosure is not limited to this. In the present disclosure, monitoring points for one joint may be set at one or three or more positions on the surface of the robot.

[0061] In addition, while the above embodiment illustrates an example in which a monitor point is set for each robot movement direction, the present disclosure is not limited to this. In the present disclosure, a monitor point does not have to be set for each robot movement direction. Furthermore, there may be a mixture of joints in which a monitor point is set for each robot movement direction and joints in which a monitor point is not set for each robot movement direction.

[0062] In addition, although the above embodiment shows an example in which torque detectors are disposed in all of the multiple joints, the present disclosure is not limited to this. In the present disclosure, the torque detector may be disposed in at least one of the multiple joints.

[0063] Furthermore, in the above embodiment, an example was shown in which two thresholds were provided: a threshold for issuing a warning and continuing the robot's operation, and a threshold for issuing an abnormality and stopping the robot or causing the robot to take evasive action. However, the present disclosure is not limited to this. In the present disclosure, only a threshold for issuing an abnormality and stopping the robot or causing the robot to take evasive action may be provided. Thresholds other than the threshold for issuing a warning and continuing the robot's operation and the threshold for issuing an abnormality and stopping the robot or causing the robot to take evasive action may also be provided.

[0064] In the above embodiment, the external force values ​​of the two joints may be combined to obtain a combined external force value. In this case, a first external force value of the first joint and a second external force value of the second joint may be obtained using the technique of the above embodiment, and the combined external force value may be obtained by calculating the square root of the sum of the squares of the first external force value and the second external force value. The combined external force value may then be compared with a threshold value.

[0065] In the above embodiment, for joints whose rotation axes are parallel to each other, such as joints 13b and 13c, the external force values ​​of the two joints may be compared, and the smaller of the two may be acquired as the external force value. The acquired external force value may then be compared with a threshold value.

[0066] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0067] Aspects It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0068] (Aspect 1) A robot system comprising: a robot including a plurality of joints; a torque detection unit disposed at a predetermined joint among the plurality of joints and detecting a detected torque value around the rotation axis of the predetermined joint; and a control unit that performs control to acquire, as an external force value acting on the robot, a second value obtained by dividing a difference between the detected torque value and a reference torque value by the radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, and converting the first value into a normal direction value based on the angle formed by the tangent direction of a circle having the radius at the monitoring point and the normal direction to the surface of the robot on which the monitoring point is set.

[0069] (Aspect 2) In the robot system according to aspect 1, the control unit performs control to acquire the second value by an equation Pai=Pi / cos θ, where Pi is the first value, θ is the angle, and Pai is the second value.

[0070] (Aspect 3) The robot system according to aspect 1 or 2, wherein the monitoring point is set at an arbitrary position on the surface of the robot that is not a fixed position.

[0071] (Aspect 4) The robot system according to any one of Aspects 1 to 3, wherein the monitoring points are set at a plurality of positions on a surface of the robot.

[0072] (Aspect 5) The robot system according to Aspect 4, wherein the monitoring point is set for each movement direction of the robot, and the control unit performs control to acquire the external force value using a monitoring point corresponding to the movement direction of the robot among the plurality of monitoring points.

[0073] (Aspect 6) The robot system according to any one of Aspects 1 to 5, wherein the torque detectors are disposed in all of the plurality of joints.

[0074] (Aspect 7) The robot system according to any one of Aspects 1 to 6, wherein the control unit controls the robot to stop or to perform an avoidance operation when the second value as the external force value exceeds a predetermined threshold value.

[0075] (Aspect 8) In the robot system according to aspect 7, when the second value as the external force value exceeds the predetermined threshold value, the control unit performs control to notify the user that the second value has exceeded the predetermined threshold value.

[0076] (Aspect 9) The robot system according to any one of Aspects 1 to 8, wherein the control unit: when the second value as the external force value exceeds a first threshold, performs control to issue a warning that the second value has exceeded the first threshold and controls the robot to continue operating; when the second value as the external force value exceeds a second threshold that is greater than the first threshold, performs control to issue a warning that the second value has exceeded the second threshold, and controls the robot to stop or to perform an avoidance operation.

[0077] (Aspect 10) The robot system according to any one of Aspects 1 to 9, wherein the robot is a robot that performs work in the same space as humans.

[0078] (Aspect 11) The robot system according to any one of Aspects 1 to 10, wherein the robot includes a hand that holds a workpiece, and a surface of the robot includes a surface of the hand and a surface of the workpiece held by the hand.

[0079] (Aspect 12) A control method for a robot system including a robot including a plurality of joints, comprising: detecting a detected torque value around a rotation axis of a predetermined joint among the plurality of joints; and obtaining a first value obtained by dividing a difference between the detected torque value and a reference torque value by a radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, and converting the first value into a normal direction value based on an angle formed between a tangent direction of a circle having the radius at the monitoring point and a normal direction to the surface of the robot on which the monitoring point is set, as an external force value acting on the robot.

[0080] 10 Robot 13 Joint 14 Torque detection unit 20 Control unit 40 Monitoring point 100 Robot system A1, A2, A3, A4, A5, A6 Rotation axis D1, D2 Operation direction P ｉ Value (first value) Pa ｉValue (second value) R Radius T1 Threshold (first threshold) T2 Threshold (predetermined threshold, second threshold) θ Angle

Claims

1. A robot system comprising: a robot including a plurality of joints; a torque detection unit disposed at a predetermined joint among the plurality of joints and detecting a detected torque value around the rotation axis of the predetermined joint; and a control unit that performs control to acquire, as an external force value acting on the robot, a second value obtained by dividing a difference between the detected torque value and a reference torque value by the radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, and converting the first value into a normal direction value based on the angle formed by the tangent direction of a circle having the radius at the monitoring point and the normal direction to the surface of the robot on which the monitoring point is set.

2. The control unit sets the first value P ｉ The angle is θ, and the second value is Pa ｉ Let's say, Pa ｉ =P ｉ The robot system according to claim 1 , wherein the second value is obtained by the following formula: / cos θ.

3. The robot system according to claim 1, wherein the monitoring point is set at an arbitrary position on the surface of the robot that is not a fixed position.

4. The robot system of claim 1, wherein the monitoring points are set at a plurality of positions on the surface of the robot.

5. A robot system as described in claim 4, wherein the monitoring point is set for each direction of movement of the robot, and the control unit performs control to acquire the external force value using a monitoring point among the multiple monitoring points that corresponds to the direction of movement of the robot.

6. The robot system according to claim 1, wherein the torque detector is disposed in each of the plurality of joints.

7. The robot system according to claim 1, wherein the control unit controls the robot to stop or to perform an avoidance action when the second value as the external force value exceeds a predetermined threshold value.

8. The robot system according to claim 7, wherein the control unit performs control to notify the user that the second value as the external force value has exceeded the predetermined threshold value when the second value exceeds the predetermined threshold value.

9. The robot system according to claim 1, wherein the control unit, when the second value as the external force value exceeds a first threshold value, controls to issue a warning that the second value has exceeded the first threshold value and controls the robot to continue operating, and when the second value as the external force value exceeds a second threshold value that is greater than the first threshold value, controls to issue a warning that an abnormality has occurred that the second value has exceeded the second threshold value and controls the robot to stop or to perform an avoidance operation.

10. The robot system according to claim 1, wherein the robot performs work in the same space as humans.

11. The robot system according to claim 1, wherein the robot includes a hand that holds a workpiece, and the surface of the robot includes the surface of the hand and the surface of the workpiece held by the hand.

12. A control method for a robot system including a robot having a plurality of joints, comprising: detecting a detected torque value around a rotation axis of a predetermined joint among the plurality of joints; and obtaining a first value obtained by dividing the difference between the detected torque value and a reference torque value by the radius from the rotation axis of the predetermined joint to a monitoring point set on the surface of the robot, and converting the first value into a normal direction value based on the angle between the tangent direction of a circle having the radius at the monitoring point and the normal direction to the surface of the robot on which the monitoring point is set, as an external force value acting on the robot.

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