Robot control device

Abstract

A robot control device (1) comprises: a storage unit (4) for storing load information, wherein the load information includes the mass and center of gravity position of a load mounted on the robot (100); a guided control unit (5) for controlling the robot (100) having a sensor (160) for detecting external force based on the external force detected by the sensor (160) and the load information stored in the storage unit (4); and a load suitability determination unit (6) for determining whether the load information stored in the storage unit (4) is suitable. When the load suitability determination unit (6) determines that the load information may be inappropriate, the guided control unit (5) limits the movement of the robot (100).

Description

Technical Field

[0001] The present disclosure relates to a robot control device. Background Art

[0002] So-called guided teaching is known in which a user performs teaching while directly pushing a robot arm with his hands and operating the robot (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-55458 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In guided teaching, the robot's movements are controlled based on the external force applied by the user (hereinafter referred to as guided control). The external force applied to the robot also includes gravity. To prevent erratic movement due to gravity, it is necessary to use information about the robot's own weight and the weight of the load attached to the robot (hereinafter referred to as load information) to compensate for the torque generated by the motor.

[0008] In addition, the robot may need to replace the hand mounted on the front end or grasp workpieces with different weights or center of gravity. In this case, it is necessary to pre-store load information for the hand that may be mounted or the workpiece that may be grasped, and switch the load information each time the hand or workpiece is changed.

[0009] However, if the stored load information is inaccurate, the robot may move in a direction that the user does not intend when guided control is performed. Therefore, it is desirable to be able to prevent the robot from moving suddenly in a direction that the user does not intend even when guided control is performed based on inaccurate load information.

[0010] Solutions for solving problems

[0011] One embodiment of the present disclosure is a robot control device comprising: a storage unit that stores load information, the load information including the mass and center of gravity position of a load mounted on the robot; a guided control unit that controls a robot having a sensor for detecting external force based on the external force detected by the sensor and the load information stored in the storage unit; and a load suitability determination unit that determines whether the load information stored in the storage unit is suitable. If the load suitability determination unit determines that the load information may be inappropriate, the guided control unit limits the movement of the robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a block diagram showing an example of a robot control device according to the first embodiment of the present disclosure.

[0013] Figure 2 It is shown by Figure 1 A perspective view of an example of a robot controlled by a robot control device.

[0014] Figure 3 It is an explanation Figure 1 Block diagram of the guided control unit of a robot control device.

[0015] Figure 4 Is explained by Figure 1 Flowchart of guided control performed by a robot controller.

[0016] Figure 5 It shows Figure 4 Flowchart of a modified example of guided control.

[0017] Figure 6 This is a block diagram showing an example of a robot control device according to a second embodiment of the present disclosure.

[0018] Figure 7 It is an explanation Figure 6 Block diagram of the guided control unit of a robot control device.

[0019] Figure 8 Is explained by Figure 6 Flowchart of guided control performed by a robot controller. DETAILED DESCRIPTION

[0020] Hereinafter, a robot controller 1 according to a first embodiment of the present disclosure will be described with reference to the accompanying drawings. The robot controller 1 according to this embodiment is, for example, a controller. Figure 2 The control device of the robot 100 is shown.

[0021] This robot 100 is a vertical six-axis multi-articulated collaborative robot comprising a base 110 installed on the ground; a rotating body 120 supported on the base 110 so as to be rotatable about a vertical first axis A; and a first arm 130 supported on the rotating body 120 so as to be rotatable about a horizontal second axis B. Furthermore, the robot 100 comprises a second arm 140 supported on the first arm 130 so as to be rotatable about a third axis C parallel to the second axis B; and a three-axis wrist unit 150 provided at the distal end of the second arm 140.

[0022] The wrist element 150 includes a first wrist element 151 supported by the second arm 140 so as to be rotatable about a fourth axis D arranged in a plane including the first axis A; and a second wrist element 152 supported by the first wrist element 151 so as to be rotatable about a fifth axis E perpendicular to the fourth axis D. Furthermore, the wrist element 150 includes a third wrist element 153 supported by the second wrist element 152 so as to be rotatable about a sixth axis F arranged in a plane parallel to the fourth axis D and perpendicular to the fifth axis E.

[0023] A torque sensor (sensor) 160 is provided on each axis of the robot 100 to detect external forces acting on the robot 100. The torque sensor 160 may be provided on each axis or on one or more axes. Alternatively, other sensors such as force sensors may be used in place of the torque sensor 160.

[0024] The robot control device 1 has at least one processor and a memory. Figure 1 As shown, the robot controller 1 includes a position command generating unit 2, a position control unit 3, a storage unit 4, a guidance control unit 5, a guidance sensitivity setting unit (load adequacy determination unit) 6, and a switching unit 7. Furthermore, a teaching operation panel 8 is connected to the robot controller 1, and the teaching operation panel 8 includes a selector switch 9.

[0025] The position command generator 2 generates a position command based on a pre-taught teaching program or a user operation. The position control unit 3 controls the motor 170 of each axis of the robot 100 based on the position command generated by the position command generator 2 .

[0026] The induction control unit 5 controls the robot 100 based on the external force detected by the torque sensor 160 included in the robot 100. The induction sensitivity setting unit 6 sets the sensitivity of the induction control.

[0027] The selector switch 9 is, for example, a switch that is closed when the user presses it with a finger and is opened when the user releases the finger.

[0028] The switching unit 7 switches to the pilot control when the switch 9 is in the closed state, and switches to the position control when the switch 9 is in the open state.

[0029] The storage unit 4 stores load information such as the mass and center-of-gravity position of each part of the robot 100 and the mass and center-of-gravity position of a load such as a hand or a workpiece attached to the robot 100 .

[0030] Since the mass and center of gravity of each part of the robot 100 are known, accurate information is assumed to be stored. However, since the mass and center of gravity of the load are set by the user each time the load is changed, they may not be set accurately.

[0031] The load information stored in the storage unit 4 is input to the position control unit 3 , and current information is fed back from the motors 170 of the respective axes of the robot 100 , and position information is fed back from encoders (not shown) included in the motors 170 .

[0032] The load information stored in the storage unit 4 is input to the guide control unit 5 , and the position information is input from the encoder to the guide control unit 5 .

[0033] like Figure 3 As shown, the pilot control unit 5 includes a load torque calculation unit 10 and an offset storage unit 11 .

[0034] The load torque calculation unit 10 sequentially calculates the gravity load torque based on the load information input from the storage unit 4 and the position information input from the encoder.

[0035] The offset storage unit 11 stores the offset of the torque sensor 160 .

[0036] The inductive control unit 5 subtracts the offset stored in the offset storage unit 11 from the external force detected by the torque sensor 160 and also subtracts the gravity load torque calculated by the load torque calculation unit 10. Thus, an estimated value of the force applied by the user to the robot 100 is calculated.

[0037] The guided control unit 5 then calculates a torque command for the motor 170 by subtracting a value obtained by multiplying the calculated estimated force value by a gain K from the gravity load torque calculated by the load torque calculation unit 10. The gain K is set to 0 ≤ K ≤ 1. The closer K is to 0, the higher the sensitivity of the guided control. The closer K is to 1, the lower the sensitivity of the guided control.

[0038] The state of the switch 9 and the estimated value of the force calculated by the guidance control unit 5 are input to the guidance sensitivity setting unit 6. Figure 4 As shown, the guidance sensitivity setting unit 6 determines whether the switch 9 is pressed (step S1 ), and waits until the switch 9 is pressed.

[0039] When the selector switch 9 is pressed, the guided control mode is switched to be enabled (step S2), and a determination is made as to whether the absolute value of the estimated force input from the guided control unit 5 is less than or equal to a predetermined threshold value T1 (step S3). If the absolute value of the estimated force is greater than threshold value T1, the gain K of the guided control unit 5 is set to a predetermined value K1 close to 1 (step S4).

[0040] When the absolute value of the estimated value is less than or equal to threshold value T1, guided control unit 6 sets gain K of guided control unit 5 to K0 which is smaller than K1 (step S5). Threshold value T1 can be appropriately set as needed.

[0041] Then, the pilot control is performed using the set gain K, and the process from step S2 is repeated until the switch 9 is turned off (step S6).

[0042] Specifically, when the switch 9 is initially switched to the closed state, if the calculated estimated force value is greater than the threshold value T1, the load information may be inaccurate, and the sensitivity of the pilot control is reduced by increasing the gain K. On the other hand, if the absolute value of the estimated force value falls below the threshold value T1 during the pilot control operation with the sensitivity reduced by increasing the gain K, the gain K is set to K0 (step S5).

[0043] When the switch 9 is turned off in the process of step S6, the guided control is switched to be invalid (step S7), and the processing ends.

[0044] According to the robot controller 1 of this embodiment configured in this manner, when guided control begins, if the absolute value of the estimated value initially calculated exceeds threshold value T1, the sensitivity of guided control is reduced. This has the advantage of limiting the movement of the robot 100 in response to the force applied by the user, and preventing the robot 100 from abruptly moving in a direction unintended by the user even when inaccurate load information is stored.

[0045] On the other hand, while performing guided control with sensitivity suppressed, if the absolute value of the estimated value falls below threshold value T1, the sensitivity is increased. This allows the robot 100 to move smoothly in accordance with the force applied by the user, facilitating operations using guided control. Even if inaccurate load information is set, increasing the sensitivity when the estimated force value is low prevents abrupt movements in directions unintended by the user, improving operability.

[0046] Furthermore, in this embodiment, as an example of limiting the movement of the robot 100 by the guided control unit 5, increasing the gain K of the guided control to reduce sensitivity is described. Alternatively, or in addition to this, the movement distance of the robot 100, which moves in response to a force applied by a user under guided control, may be limited to a predetermined value or less.

[0047] For example, Figure 5As shown, it is determined whether the flag It_end indicating the end in an abnormal state is normal (false) (step S21). If abnormal, the guided control is disabled (step S22). When the abnormal state is resolved, the flag It_end is initialized to normal (false).

[0048] On the other hand, if the flag It_end is false, it is determined whether the switch 9 is in the closed state (step S23). If the switch 9 is not in the closed state, the current position is stored as P1 (step S24).

[0049] On the other hand, when the selector switch 9 is closed, a determination is made as to whether the absolute value of the estimated force is less than or equal to a predetermined threshold value T1 (step S25). If the absolute value of the estimated force is less than or equal to threshold value T1, the switching unit 7 switches the guided control to be effective (step S26) and sets the guided control gain to K0, thereby increasing the guided control sensitivity (step S27).

[0050] On the other hand, if the absolute value of the estimated value is greater than the threshold value T1, it is determined whether the distance between the current position and P1 stored in step S24 is less than or equal to a predetermined threshold value L1 (step S28). If the distance is less than or equal to the threshold value L1, the switching unit 7 switches to enabling the guided control (step S29) and sets the guided control gain to K1 to reduce the sensitivity of the guided control (step S30).

[0051] The guided control is continued until the switch 9 is switched to the OFF state, in which case the process starting from step S25 is repeated (step S31). After the switch 9 is switched to the OFF state, the guided control is switched to be invalid (step S22).

[0052] On the other hand, when it is determined in step S28 that the distance between the current position and P1 is greater than the threshold L1, the flag It_end switches to abnormal (true) (step S32), and the guided control switches to invalid (step S32).

[0053] Specifically, if the absolute value of the estimated force exceeds threshold value T1, the set load information may be inaccurate. This reduces the sensitivity of the guided control while also preventing the movement distance from becoming excessively large. Even if inaccurate load information is set, if the robot 100's movement distance is shortened, the robot 100 can be prevented from moving significantly in a direction unintended by the user. This provides the advantage of more reliably preventing the robot 100 from moving suddenly in a direction unintended by the user.

[0054] As another limitation on the movement of the robot 100, the axes of the robot 100 that move in response to the force applied by the user can be limited. For example, by limiting the guided control to only the three wrist axes of the wrist unit 150, it is possible to prevent the robot 100 from moving significantly in directions unintended by the user.

[0055] Next, a robot control device 50 according to a second embodiment of the present disclosure will be described below with reference to the drawings.

[0056] like Figure 6 and Figure 7 As shown, the robot controller 50 of this embodiment is different from the robot controller 1 of the first embodiment in that the robot controller 50 includes a load information estimating unit 51. In the figure, reference numeral 52 denotes a monitor.

[0057] For example, when load identification information and a load information estimation instruction are input into the teaching operation panel 8, the load information estimation unit 51 sequentially displays a plurality of postures of the robot 100 for load information estimation on the monitor 52. The load information estimation unit 51 then instructs the user to move the robot 100 to the displayed postures through guided control.

[0058] When the user switches switch 9 to the closed state as instructed and, through guided control, moves the robot 100 to a position close to the displayed posture, the load information estimation unit 51 instructs the user to input a measurement command. When the user inputs the load identification information and the measurement command as instructed, the load information estimation unit 51 records the external force detected by the torque sensor 160 and the position of the motor 170 at that time.

[0059] The load information estimation unit 51 then records the external forces along three axes and the position of the motor 170 in the three or more postures of the wrist unit 150, each with different gravity application methods. This solves the equations of motion for the robot 100 and estimates the mass and center of gravity of the load, as well as the offset of the torque sensor 160. The estimated mass and center of gravity of the load are stored in the storage unit 4 in association with the load identification information. The estimated offset is stored in the offset storage unit 11 of the guidance control unit 5.

[0060] In this case, in the robot control device 50 of this embodiment, as shown in FIG. Figure 8 As shown, the load information estimation unit 51 waits for input of load identification information and a load information estimation instruction (step S11). When the load identification information and the load information estimation instruction are input, the load information estimation unit 51 instructs the guidance sensitivity setting unit to set the gain K of the guidance control to K1, thereby reducing the sensitivity (step S12).

[0061] The load information estimation unit 51 then determines whether the selector switch 9 is closed (step S13). If so, it determines whether the axis being operated by the guided control is the wrist axis (step S14). If the wrist axis is being operated, the guided control becomes effective (step S15). If an axis other than the wrist axis is being operated or if the selector switch 9 is open, the guided control becomes ineffective (step S16).

[0062] When the load information estimation operation is completed and the accurate load information is stored in the storage unit, when the robot 100 is taught using the guide control, there is no need to input the estimation instruction. Figure 4 or Figure 5 Alternatively, for a load for which load information estimation has been implemented, a flag indicating that estimation has been implemented may be set in advance, and when a load stored in the storage unit 4 is selected and guided control is started, the gain is set to K0 if the flag is set.

[0063] Thus, according to the robot control device 50 of this embodiment, since accurate load information may not be stored when the load information estimation unit 51 is instructed to estimate load information, the sensitivity of the guided control can be reduced, thereby limiting the movement of the robot 100. Thus, when the robot 100 is moved by guided control while load information estimation is being performed, it is possible to prevent the robot 100 from abruptly moving in a direction opposite to the user's intention based on inaccurate load information.

[0064] Furthermore, in this embodiment, as restrictions on the movement of the robot 100 during the load information estimation operation, two methods are adopted: reducing the sensitivity of the lead-through control and limiting the axis for which the lead-through control is effective to only the wrist axis. However, only one of these methods may be adopted. Figure 5 The moving distance of the robot 100 is similarly limited.

[0065] The embodiments of the present disclosure are described in detail above, but the present disclosure is not limited to the above-mentioned embodiments. Various additions, replacements, changes, partial deletions, etc. can be made to these embodiments without departing from the scope of the invention, or without departing from the scope of the ideas and purposes of the present invention derived from the contents recorded in the claims and their equivalents. For example, in the above-mentioned embodiments, the order of each action or the order of each processing is exemplary, and the present invention is not limited thereto. In addition, the same applies to the case where numerical values ​​or mathematical formulas are used in the description of the above-mentioned embodiments.

[0066] Description of reference numerals:

[0067] 1.50: Robot control device

[0068] 3: Position control unit

[0069] 4: Storage

[0070] 5: Guided control unit

[0071] 6: Guidance sensitivity setting unit (load adequacy judgment unit)

[0072] 9: Toggle switch

[0073] 51: Load information estimation unit

[0074] 100: Robot

[0075] 160: Torque sensor (sensor)

[0076] T1: Threshold

Claims

1. A robot control device, characterized in that: have: a storage unit that stores load information including a mass and a center-of-gravity position of a load mounted on a robot having a wrist axis; a guided control unit that controls the robot including the sensor for detecting the external force based on the external force detected by the sensor and the load information stored in the storage unit; a load suitability determination unit configured to determine whether the load information stored in the storage unit is suitable, and a load information estimating unit that records the external force detected by the sensor and the position of the motor of the robot when the robot is set to a plurality of postures, and estimates the load information based on the recorded external force and the position of the motor; if the load information estimating unit fails to estimate the load information, the load suitability determining unit determines that the load information stored in the storage unit is likely to be inappropriate, When the load suitability determination unit determines that the load information may be inappropriate, the inductive control unit limits the axis of the robot that operates according to the external force to only the wrist axis.

2. The robot control device according to claim 1, characterized in that: The robot control device comprises: a position control unit that controls the robot according to the position instruction; and The switching switch is controlled by the position control unit or the guided control unit. When the switching switch switches to control by the guided control unit, if the estimated value of the force applied by the user estimated based on the external force detected by the sensor and the load information exceeds a predetermined threshold, the load suitability determination unit determines that the load information may be inappropriate.

3. The robot control device according to claim 2, characterized in that: After the robot motion is restricted due to the estimated value exceeding the threshold, the restriction is released if the estimated value becomes equal to or less than the threshold.

4. The robot control device according to any one of claims 1 to 3, characterized in that: When the load suitability determination unit determines that the load information may be inappropriate, the sensitivity of the robot's operation to the external force is reduced.

5. The robot control device according to any one of claims 1 to 3, characterized in that: When the load suitability determination unit determines that the load information may be inappropriate, the movement distance of the robot due to the external force is limited.

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