Robot control unit and robot programming unit

Abstract

Robot control device (1), comprising: a comparison unit (2, 12), wherein, when a robot (110) equipped with a force sensor (112) capable of detecting force components (Fx, Fy, Fz) of the same type in a plurality of directions (x, y, z) is operating, the comparison unit (2, 12) compares a magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) with a predetermined threshold value for each direction (x, y, z); and a controller (3) wherein, if the comparison unit (2, 12) determines that a magnitude of a force component (Fx, Fy, Fz) in any of the directions (x, y, z) exceeds the threshold, the controller (3) controls the robot (110) to prevent an increase in the magnitude of the force component (Fx, Fy, Fz) in the direction (x, y, z), wherein the threshold comprises a first threshold as a nominal value of the force sensor (112) for each direction (x, y, z) and a second threshold as a test load of the force sensor (112) which is greater than the first threshold, and wherein the controller (3) reduces the operating speed of the robot (110) if any force component (Fx, Fy, Fz) exceeds the first threshold, and causes the robot (110) to stop working, or causes the robot (110) to work along a reverse path after the robot (110) has stopped working if any force component (Fx, Fy, Fz) exceeds the second threshold, where excessive force is anticipated in advance and the acceleration and deceleration of the robot (110) are limited to reduce the magnitude of each force component (Fx, Fy, Fz) with respect to the rated load and the test load.

Description

[0001] The present disclosure relates to a robot control device and a robot programming device.

[0002] A known robot is equipped with a force sensor that is capable of detecting forces in a plurality of directions (see e.g. JP 2012-137421 A). PATENT LITERATURE JP 2012-137421 A DE 10 2018 100 217 A1 DE 10 2018 000 467 A1 DE 10 2016 119 600 A1 DE 10 2015 012 232 A1 DE 10 2015 009 654 A1 US 2016 / 0221193 A1

[0003] Typically, the forces measured in multiple directions are combined to calculate a combined force. It is then determined whether the calculated combined force exceeds a predetermined threshold. Especially in the case of a collaborative robot, determining the magnitude of the combined force is necessary, as the magnitude of an external force acting on the collaborative robot can be problematic.

[0004] However, a force sensor or a tool attached to the robot may have a different rating depending on the direction. If the detection is based on the combined force, it may be difficult to detect a force component in any of the directions, even if the force component exceeds the rating.

[0005] DE 10 2018 100 217 A1 discloses a system for human-robot collaboration with a function for safety assurance operation for a robot.

[0006] Furthermore, DE 10 2018 000 467 A1 describes a robot system comprising a force-controlled pushing device which, when a robot is guided and moved, causes an object provided at a tip end of the robot to be brought into suitable contact with another object.

[0007] In addition, DE 10 2016 119 600 A1 shows a robot safety monitoring device for a robot for monitoring the safety of a robot by detecting external forces.

[0008] Furthermore, DE 10 2015 012 232 A1 discloses a robot system collaborating with humans, in which a robot and a human share a workspace.

[0009] DE 10 2015 009 654 A1 also describes a mobile cooperative robot for collaboration with a person.

[0010] Furthermore, US 2016 / 0221193 A1 describes, among other things, a robot with a robot arm having a plurality of sensors whose detection ranges for a force differ from one another.

[0011] An object of the invention is to reduce the force components in any of the directions in a simple manner when controlling a robot.

[0012] The object is achieved according to claim 1 by a robot control device comprising a comparison unit, wherein, when a robot equipped with a force sensor capable of detecting force components of a similar type in a plurality of directions is operating, the comparison unit compares a magnitude of each force component detected by the force sensor with a predetermined threshold value for each direction; and a controller, wherein, if the comparison unit determines that a magnitude of a force component in any of the directions exceeds the threshold value, the controller controls the robot to prevent an increase in the magnitude of the force component in that direction, wherein the threshold value comprises a first threshold value as a rated value of the force sensor for each direction and a second threshold value as a test load of the force sensor, which is greater than the first threshold value.and wherein the controller reduces an operating speed of the robot if any force component exceeds the first threshold and causes the robot to stop working, or causes the robot to work along a reverse path after the robot stops working if any force component exceeds the second threshold, wherein excessive force is estimated in advance and the acceleration and deceleration of the robot are limited to reduce the magnitude of each force component with respect to the rated load and the test load.

[0013] Advantageous embodiments of the robot control device are described in the subclaims.

[0014] The object is further achieved by a robot programming device according to patent claim 11. Fig. 1 illustrates the overall configuration of a robot system including a controller according to an embodiment of the present disclosure. Fig. 2 is a perspective view showing a force sensor and a tool mounted on a distal end of a wrist of a robot in the robot system in Fig. 1, as well as schematically showing the axial directions of the force sensor and tool. Fig. 3 is a block diagram showing a control device in Fig. 1 represents. Fig. 4 is a block diagram showing a modification of the control device in Fig. 1 represents. Fig. 5 is a block diagram illustrating a programming device according to an embodiment of the present disclosure.

[0015] A robot control device 1 and a robot programming device 10 according to an embodiment of the present disclosure will be described below with reference to the drawings.

[0016] The control device 1 according to this embodiment is in a Fig. 1 shown robot system 100.

[0017] The robot system 100 includes a robot 110 and the control device 1 according to this embodiment.

[0018] The robot 110 is a six-axis vertically articulated robot or may be of any type, such as a vertically articulated robot of a type other than a six-axis type or a horizontally articulated robot.

[0019] The robot 110 includes a base 113 fixed on a floor surface F, a rotary body (joint) 114 rotatable relative to the base 113 about a first axis A, a first arm (joint) 115 rotatable relative to the rotary body 114 about a horizontal second axis B orthogonal to the first axis A, a second arm (joint) 116 rotatable relative to the first arm 115 about a third axis C parallel to the second axis B, and a wrist (joint) 111 rotatable relative to the second arm 116. The distal end of the wrist 111 has a tool S attached thereto.

[0020] The robot 110 also includes a three-axis force sensor 112 between the distal end surface of the wrist 111 and the tool S. The force sensor 112 can detect three force components Fx, Fy and Fz acting on the tool S along three axes x, y and z. As shown in Fig. 2, the three axes z, x and y are each aligned with a direction z extending from the center of the wrist 111 to the distal end of the tool S and two directions x and y extending orthogonally to the direction z and orthogonally to each other.

[0021] As it is in Fig. As shown in Figure 3, the control device 1 comprises a comparison unit 2 that receives the three force components Fx, Fy, and Fz detected by the force sensor 112 and compares the magnitude (absolute value) of the individual force components Fx, Fy, and Fz with a corresponding threshold value. The control device 1 also comprises a controller 3.

[0022] The controller 3 causes the robot 110 to operate according to a preliminary learned operation program and reduces the operating speed of the robot 110 if the magnitude of any of the force components Fx, Fy, and Fz exceeds the corresponding threshold value as a result of the comparison by the comparison unit 2. The threshold values ​​are set to values ​​less than or equal to the rated loads in the three directions x, y, and z in which the force sensor 112 is capable of detecting the force components Fx, Fy, and Fz.

[0023] In the control device 1 according to this embodiment having the configuration described above, when the robot 110 is operating according to the operation program, the force components Fx, Fy, and Fz in the three orthogonal directions x, y, and z are detected by the force sensor 112 and compared with the threshold values ​​for the respective directions x, y, and z by the comparison unit 2. As a result, if a force component in any of the directions exceeds the corresponding threshold value, the controller 3 reduces the operating speed of the robot 110 so that the force component in the direction in which the corresponding threshold value has been exceeded is prevented from further increasing.

[0024] For example, in a case where precision fitting or polishing is to be performed according to force control using the force sensor 112, the force sensor to be used must have high detection performance. In this case, a compact force sensor with a rated load equal to or less than the rated load of the robot 110 is sometimes installed. Even in such a case, threshold values ​​are set for the x, y, and z directions in which the force sensor 112 is capable of detecting the force components, and the operating speed of the robot 110 is reduced if any of the force components Fx, Fy, and Fz in the x, y, and z directions exceeds the corresponding threshold value. Consequently, the force components Fx, Fy, and Fz in the x, y, and z directions can be prevented from exceeding the rated load of the force sensor 112. This is advantageous in that the force sensor 112 can be maintained in good condition.

[0025] In particular, the control device 1 for the robot 110 according to this embodiment is advantageous in that the force sensor 112 installed on the robot 110 can be downsized and designed for high precision while maintaining the integrity of the force sensor 112. If the actual force acting on the tool S is to be detected, a combined force can be calculated by combining the force components Fx, Fy, and Fz.

[0026] In this embodiment, the exemplary controller 1 prevents failure of the force sensor 112 even if the force sensor 112 is downsized. Alternatively, the force sensor 112 used may have a sufficient rated load, and values ​​less than or equal to the rated loads of the tool S in the x, y, z directions may be set as threshold values. Accordingly, a force applied to the tool S in the x, y, z directions is prevented from exceeding the corresponding rated load of the tool S, whereby the integrity of the tool S can be maintained if the tool S has different rated loads in the x, y, z directions.

[0027] In this embodiment, it is determined whether the force components Fx, Fy and Fz actually detected by the force sensor 112 have exceeded the respective threshold values ​​for the x, y, z directions or not. Alternatively, as shown in Fig. 4, the control device 1 may include a force calculator 4 that calculates the magnitude of each force component Fx, Fy, and Fz detected by the force sensor 112 based on a geometric parameter of the robot 110 and a state quantity of the robot 110.

[0028] In this case, the comparison unit 2 may compare the force components Fx, Fy, and Fz calculated by the force calculator 4 with the threshold values. The geometric parameter includes, for example, the mass and joint length of each joint 114, 115, and 116 of the robot 110. Furthermore, the state quantity may include the angle of each axis of the robot 110, its operating speed, and its acceleration.

[0029] Accordingly, the force calculator 4 can calculate the force components Fx, Fy, and Fz with regard to the influence of gravity and dynamics and preliminarily predict whether and at what point in the operating program the magnitude of the force component Fx, Fy, or Fz exceeds the corresponding threshold. Therefore, the operating speed can be reduced before the magnitude of the force component Fx, Fy, or Fz exceeds the corresponding threshold. In this case, the thresholds can be set to values ​​equal to the rated loads of the force sensor 112 in the x, y, and z directions.

[0030] Furthermore, the estimation of the force components Fx, Fy, and Fz by the force calculator 4 and the detection of the force components Fx, Fy, and Fz by the force sensor 112 can be performed simultaneously. The operating speed of the robot 110 is reduced even if the force components do not exceed the threshold values ​​when estimated by the force calculator 4, but the actual force components Fx, Fy, and Fz exceed the threshold values. This is advantageous in that the integrity of the force sensor 112 can be maintained.

[0031] As an alternative to this embodiment, in which the force sensor 112 detects the force components Fx, Fy, and Fz in the three orthogonal directions x, y, and z, the force sensor 112 may detect torques about axes extending in the three directions x, y, and z, or may detect the force component Fz in the z direction and torques about the axes extending in the y and z directions. As a further alternative, the force sensor 112 may detect a torque about the axis extending in the z direction and the force components Fy and Fz in the y and z directions. Furthermore, the detection directions by the force sensor 112 do not necessarily have to be orthogonal to each other.

[0032] In this embodiment, the controller 3 reduces the operating speed of the robot 110 if the magnitude of any of the force components Fx, Fy, and Fz in the x, y, and z directions exceeds the corresponding threshold. Alternatively, the robot 110 may be stopped, or the robot 110 may operate along a reverse path after stopping to prevent a further increase in the magnitude of the force component Fx, Fy, or Fz in the x, y, or z direction in which the threshold has been exceeded.

[0033] As an alternative to this embodiment in which the force sensor 112 is mounted at a remote end of the wrist 111, the invention can be applied in a case in which the force sensor 112 is mounted at another freely selected location.

[0034] In the control device 1 according to this embodiment, the force components Fx, Fy and Fz obtained by the force sensor 112 or the force calculator 4 are compared with the threshold values ​​in real time, and the robot 110 is controlled by the controller 3. Alternatively, as shown in Fig. 5, the invention can be applied to the programming device 10 which causes the operating program to work offline.

[0035] As is particularly the case in Fig.As shown in Figure 5, the programming device 10 comprises a force calculator 11 that calculates the force components Fx, Fy, and Fz in the three directions x, y, and z at each point in the operating program, and a comparison unit 12 that compares the magnitude of each calculated force component Fx, Fy, and Fz with a corresponding threshold value of each direction x, y, and z. The programming device 10 also comprises a program setter 13 that changes the operating program if the comparison unit 12 determines that the magnitude of any of the force components Fx, Fy, and Fz in the directions x, y, and z has exceeded the corresponding threshold value, such that the force component Fx, Fy, or Fz must be set less than or equal to the threshold value.

[0036] Accordingly, even in a case that the installed force sensor 112 is a compact force sensor having a rated load lower than the rated load of the robot 110, the operation program is easily caused to operate offline, whereby the operation program can be adjusted so as not to apply an excessive load to the force sensor 112.

[0037] If the specifications of the force sensor 112 are not predetermined, a maximum value for the magnitude of each force component Fx, Fy, and Fz calculated by the force calculator 11 in the three directions x, y, and z can be determined at any point in the operating program. Accordingly, an appropriately dimensioned force sensor 112 with a rated load higher than the maximum values ​​of the force components Fx, Fy, and Fz can be selected.

[0038] The threshold values ​​to be compared with the estimated values ​​or the detected values ​​Fx, Fy, and Fz of the force sensor 112 may each be the test load of the force sensor 112, which normally needs to be set larger than the rated load, instead of the rated load of the force sensor 112. By comparing each force component Fx, Fy, and Fz with the test load of the force sensor 112, failure of the force sensor 112 can be more reliably prevented.

[0039] Alternatively, the threshold values ​​to be compared with the force components Fx, Fy, and Fz may be both the rated load and the proof load of the force sensor 112. Specifically, the robot operation may be provided with a first restriction if a force component exceeds the rated load serving as a first threshold, and the robot operation may be provided with a second restriction if a force component exceeds the proof load serving as a second threshold. In detail, if it is determined that a force component exceeds the rated load, the operating speed of the robot 110 is reduced as the first restriction. If it is determined that a force component exceeds the proof load, the operation of the robot 110 may be stopped as the second restriction. By restricting the robot operation in a two-stage manner, failure of the force sensor 112 can be more reliably prevented.

[0040] Usually, when the robot 110 is to be decelerated, stopped, or caused to operate along a reverse path to reduce the force acting on the force sensor 112 based on the comparison result between each force component Fx, Fy, and Fz and the rated loads and the proof load, an excessive force due to, for example, an inertial force acting on the robot 110 during deceleration may continue to act on the force sensor 112 until the robot 110 stops operating. Therefore, the force sensor 112 can be more reliably maintained in a proper state by estimating the excessive force in advance and limiting the acceleration and deceleration of the robot 110 to reduce the magnitude (absolute value) of each force component Fx, Fy, and Fz with respect to the rated load and the proof load.

[0041] Furthermore, in an application using the force sensor 112, it is often the case that the robot 110 is pushed outward, and the robot 110 is controlled to keep the pushing force constant. In this case, the force sensor 112 receives this pushing force in addition to the calculated force calculated from the geometric parameter and the state quantity of the robot 110. Since the magnitude of this pushing force can be preliminarily set for each x, y, and z direction according to the application, if each calculated force component Fx, Fy, and Fz of the force sensor 112 and the corresponding threshold values ​​are to be compared, a value obtained by subtracting a predetermined pushing force from the rated load and the test load of the force sensor 112 can be set as the threshold value, so that the comparison and determination operations can be performed more appropriately for each application. LIST OF REFERENCE SYMBOLS 1 control device 2, 12 Comparison unit 3 Control 4, 11 force calculator 10 Programming device 13 program adjusters 110 robots 111 Wrist 112 force sensor 114 Rotating body (joint) 115 first arm (joint) 116 second arm (joint) S tool x, y, z directions Fx, Fy, Fz force components

Claims

[1] Robot control device (1), comprising: a comparison unit (2, 12), wherein, when a robot (110) equipped with a force sensor (112) capable of detecting force components (Fx, Fy, Fz) of a same type in a plurality of directions (x, y, z) operates, the comparison unit (2, 12) compares a magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) with a predetermined threshold value for each direction (x, y, z); and a controller (3), wherein, if the comparison unit (2, 12) determines that a magnitude of a force component (Fx, Fy, Fz) in any of the directions (x, y, z) exceeds the threshold value, the controller (3) controls the robot (110) to prevent an increase in the magnitude of the force component (Fx, Fy, Fz) in the direction (x, y, z), wherein the threshold value comprises a first threshold value as a nominal value of the force sensor (112) for each direction (x, y, z) and a second threshold value as a test load of the force sensor (112) which is greater than the first threshold value, and wherein the controller (3) reduces an operating speed of the robot (110) if any force component (Fx, Fy, Fz) exceeds the first threshold and causes the robot (110) to stop working, or causes the robot (110) to work along a reverse path after the robot (110) has stopped working if any force component (Fx, Fy, Fz) exceeds the second threshold, wherein an excessive force is estimated in advance and the acceleration and deceleration of the robot (110) is limited to reduce the magnitude of each force component (Fx, Fy, Fz) with respect to the rated load and the test load. [2] Robot control device (1) according to claim 1, further comprising: a force calculator (4, 11) which calculates the magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) on the basis of a geometric parameter of the robot (110) and a state quantity of the robot (110), wherein the comparison unit (2, 12) compares the magnitude of each force component (Fx, Fy, Fz) calculated by the force calculator (4, 11) with the threshold value. [3] Robot control device (1) according to claim 1, wherein the comparison unit (2, 12) compares the magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) with the threshold value. [4] Robot control device (1) according to one of claims 1 to 3, wherein the force sensor (112) is provided at a remote end of a wrist (111) of the robot (110). [5] Robot control device (1) according to claim 2, wherein the geometric parameter comprises a mass and a length of each joint (114, 115, 116) of the robot (110). [6] Robot control device (1) according to one of claims 1 to 5, wherein each force component (Fx, Fy, Fz) detected by the force sensor (112) is a force along a predetermined axis or a torque about the axis. [7] Robot control device (1) according to one of claims 1 to 6, wherein the threshold value is set less than or equal to a nominal value of the force sensor (112) for each direction (x, y, z). [8] Robot control device (1) according to one of claims 1 to 6, wherein the threshold value is set to be less than or equal to a nominal value of a tool (S) attached to the robot (110) for each direction (x, y, z). [9] Robot control device (1) according to one of claims 1 to 8, wherein the controller (3) reduces an operating speed of the robot (110) when any force component (Fx, Fy, Fz) exceeds the threshold value. [10] Robot control device (1) according to claim 1, further comprising: a force calculator (4, 11), wherein, if the robot (110) is pushed outward by a predetermined pushing force, the force sensor (112) calculates the magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) on the basis of a geometric parameter of the robot (110), a state quantity of the robot (110) and the pushing force, and wherein the comparison unit (2, 12) compares the magnitude of each force component (Fx, Fy, Fz) calculated by the force calculator (4, 11) with the threshold value. [11] Robot programming device (10), comprising: a force calculator (4, 11), wherein, when a robot (110) equipped with a force sensor (112) capable of detecting force components (Fx, Fy, Fz) of a same type in a plurality of directions (x, y, z) operates, the force calculator (4, 11) calculates a magnitude of each force component (Fx, Fy, Fz) detected by the force sensor (112) on the basis of a geometric parameter of the robot (110) and an operation program of the robot (110); a comparison unit (2, 12) which compares each force component (Fx, Fy, Fz) calculated by the force calculator (4, 11) with a predetermined threshold value for each direction (x, y, z), wherein the threshold value comprises a first threshold value as a nominal value of the force sensor (112) for each direction (x, y, z) and a second threshold value as a test load of the force sensor (112) which is greater than the first threshold value, and wherein an excessive force is estimated in advance and the acceleration and deceleration of the robot (110) is limited to reduce the magnitude of each force component (Fx, Fy, Fz) with respect to the rated load and the test load; and a program setter (13), wherein, if the comparison unit (2, 12) determines that a magnitude of a force component (Fx, Fy, Fz) in any of the directions (x, y, z) exceeds the threshold value, the program setter (13) changes the operation program such that the force component (Fx, Fy, Fz) in the direction (x, y, z) is set to be less than or equal to the threshold value.

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