Robot Control Device

Abstract

This robot control device 1 is provided with: a storage unit (4) that stores load information including the mass and center of gravity of the load attached to a robot (100); a lead-through control unit (5) that controls the robot (100), which is provided with a sensor (160) for detecting external forces, on the basis of 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) that determines whether or not the load information stored in the storage unit (4) is suitable. If the load suitability determination unit (6) determines that there is a possibility that the load information is unsuitable, then the lead-through control unit (5) restricts operation of the robot (100).

Description

[Technical field]

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

[0002] A so-called lead-through teaching method is known in which a user teaches a robot arm by directly pushing and operating the robot arm with his or her hand (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-55458 A Summary of the Invention [Problem to be solved by the invention]

[0004] In lead-through teaching, the robot is controlled to move according to the external force applied by the user (hereinafter referred to as lead-through control). The external force applied to the robot is gravity, and to prevent the robot from moving on its own due to gravity, it is necessary to compensate for the torque generated by the motor using information on the robot's own weight and information on the weight of the load attached to the robot (hereinafter referred to as load information).

[0005] In addition, the robot may need to change the hand attached to the tip or grip a workpiece with a different weight or center of gravity. In this case, it is necessary to store in advance the load information of the hand that may be attached or the workpiece that may be gripped, and to switch the load information every time the hand or workpiece is changed.

[0006] However, when the stored load information is inaccurate, the robot may move in a direction unintended by the user when the lead-through control is performed. Therefore, it is desirable to prevent the robot from suddenly moving in a direction unintended by the user even when the lead-through control is performed based on inaccurate load information. [Means for solving the problem]

[0007] One aspect of the present disclosure is a robot control device comprising a memory unit that stores load information including the mass and center of gravity position of a load attached to a robot, a lead-through control unit that controls a robot equipped with a sensor that detects external forces based on the external force detected by the sensor and the load information stored in the memory unit, and a load suitability determination unit that determines whether the load information stored in the memory unit is appropriate, wherein the lead-through control unit limits the operation of the robot when the load suitability determination unit determines that the load information may be inappropriate. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram showing an example of a robot control device according to a first embodiment of the present disclosure. FIG. [Diagram 2] 2 is a perspective view showing an example of a robot controlled by the robot control device of FIG. 1. [Diagram 3] 2 is a block diagram illustrating a lead-through control unit of the robot control device of FIG. 1. [Figure 4] 4 is a flowchart illustrating a lead-through control by the robot control device of FIG. 1. [Diagram 5] 5 is a flowchart showing a modified example of the lead-through control in FIG. [Figure 6] FIG. 11 is a block diagram showing an example of a robot control device according to a second embodiment of the present disclosure. [Figure 7] 7 is a block diagram illustrating a lead-through control unit of the robot control device of FIG. 6. [Figure 8]7 is a flowchart illustrating the lead-through control by the robot control device of FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A robot control device 1 according to a first embodiment of the present disclosure will be described below with reference to the drawings. The robot control device 1 according to this embodiment is, for example, a control device that controls a robot 100 shown in FIG.

[0010] This robot 100 is a vertical six-axis articulated collaborative robot, and includes a base 110 placed on the floor, a rotating body 120 supported rotatably relative to the base 110 about a vertical first axis A, and a first arm 130 supported rotatably relative to the rotating body 120 about a horizontal second axis B. The robot 100 also includes a second arm 140 supported rotatably relative to the first arm 130 about a third axis C parallel to the second axis B, and a three-axis wrist unit 150 provided at the tip of the second arm 140.

[0011] Wrist unit 150 includes a first wrist element 151 rotatably supported relative to second arm 140 about a fourth axis D arranged in a plane including first axis A, and a second wrist element 152 rotatably supported relative to first wrist element 151 about a fifth axis E perpendicular to the fourth axis D. Wrist unit 150 further includes a third wrist element 153 rotatably supported by second wrist element 152 about a sixth axis F arranged in a plane parallel to the fourth axis D and perpendicular to the fifth axis E.

[0012] A torque sensor (sensor) 160 that detects an external force acting on the robot 100 is disposed on each axis of the robot 100. The torque sensor 160 may be provided on each axis, or on one or more axes. Also, instead of the torque sensor 160, other sensors such as a force sensor may be used.

[0013] 1, the robot control device 1 includes a position command generating unit 2, a position control unit 3, a storage unit 4, a lead-through control unit 5, a lead-through sensitivity setting unit (load suitability determining unit) 6, and a switching unit 7. A teaching operation panel 8 is connected to the robot control device 1, and the teaching operation panel 8 is provided with a changeover switch 9.

[0014] The position command generating unit 2 generates a position command based on a previously taught teaching program or an operation by a user. The position control unit 3 controls the motors 170 of the respective axes of the robot 100 based on the position commands generated by the position command generating unit 2.

[0015] The lead-through control unit 5 controls the robot 100 based on an external force detected by a torque sensor 160 provided in the robot 100. The lead-through sensitivity setting unit 6 sets the sensitivity of the lead-through control.

[0016] The changeover switch 9 is, for example, a switch that is turned on when pressed by a user's finger and turned off when the user releases the finger. The switching unit 7 switches to the lead-through control when the changeover switch 9 is turned on, and switches to the position control when the changeover switch 9 is turned off.

[0017] 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. The mass and center of gravity of each part of the robot 100 are known and therefore accurate information is assumed to be stored. The mass and center of gravity of the load are set by the user each time the load is changed, and therefore may not be set accurately.

[0018] To the position control unit 3, load information stored in the storage unit 4 is input, and current information from the motors 170 of the respective axes of the robot 100 and position information from encoders (not shown) provided on the motors 170 are fed back. The lead-through control unit 5 receives the load information stored in the storage unit 4, and also receives the position information from the encoder.

[0019] The lead-through control unit 5 includes a load torque calculation unit 10 and an offset amount storage unit 11, as shown in FIG. 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. The offset amount storage unit 11 stores the offset amount of the torque sensor 160.

[0020] The lead-through control unit 5 subtracts the offset amount stored in the offset amount storage unit 11 from the external force detected by the torque sensor 160, and also subtracts the gravitational load torque calculated by the load torque calculation unit 10. In this way, an estimate of the force applied to the robot 100 by the user is calculated.

[0021] Then, the lead-through control unit 5 calculates a torque command for the motor 170 by multiplying the calculated force estimate by the gain K and subtracting the result from the gravity load torque calculated by the load torque calculation unit 10. The gain K is 0≦K≦1, and the closer to K=0, the higher the sensitivity of the lead-through control, and the closer to K=1, the lower the sensitivity of the lead-through control.

[0022] The state of the changeover switch 9 and the force estimate calculated by the lead-through control unit 5 are input to the lead-through sensitivity setting unit 6. As shown in Fig. 4, the lead-through sensitivity setting unit 6 determines whether the changeover switch 9 has been pressed (step S1), and waits until the changeover switch 9 is pressed.

[0023] When the changeover switch 9 is pressed, the lead-through control is switched to be enabled (step S2), and it is determined whether the absolute value of the force estimate input from the lead-through control unit 5 is equal to or smaller than a predetermined threshold value T1 (step S3). If the absolute value of the estimate is greater than the threshold value T1, the gain K of the lead-through control unit 5 is set to a predetermined value K1 close to 1 (step S4).

[0024] If the absolute value of the estimated value is equal to or smaller than the threshold value T1, the read-through sensitivity setting unit 6 sets the gain K of the read-through control unit 5 to K0, which is smaller than K1 (step S5). The threshold value T1 can be set appropriately as necessary. Then, the lead-through control is performed using the set gain K, and the process from step S2 is repeated until the changeover switch 9 is turned off (step S6).

[0025] That is, when the changeover switch 9 is first switched to the on state, if the calculated force estimate is greater than the threshold value T1, the load information may be inaccurate, and the sensitivity of the lead-through control is reduced by increasing the gain K. On the other hand, if the absolute value of the estimate becomes equal to or less than the threshold value T1 while the lead-through control is being performed with the sensitivity reduced by increasing the gain K, the gain K is set to K0 (step S5). After the changeover switch 9 is turned off in the process of step S6, the lead-through control is switched to be disabled (step S7), and the process is completed.

[0026] According to the robot control device 1 according to the present embodiment configured as described above, when the lead-through control is started, if the absolute value of the estimated value calculated initially is greater than the threshold value T1, the sensitivity of the lead-through control is reduced. This has the advantage that the movement of the robot 100 according to the force applied by the user can be restricted, and even if inaccurate load information is stored, the robot 100 can be prevented from suddenly moving in a direction unintended by the user.

[0027] On the other hand, during the lead-through control in a state where the sensitivity is suppressed, if the absolute value of the estimated value becomes equal to or less than the threshold value T1, the sensitivity is increased. As a result, the robot 100 can be smoothly operated according to the force applied by the user, and work using the lead-through control can be easily performed. Even if inaccurate load information is set, when the estimated value of the force is small, it is possible to prevent the robot from suddenly operating in a direction unintended by the user even if the sensitivity is increased, and workability can be improved.

[0028] In the present embodiment, the gain K of the lead-through control is increased to reduce the sensitivity as an example of limiting the movement of the robot 100 by the lead-through control unit 5. Alternatively or in addition to this, the movement distance of the robot 100, which moves in response to the force applied by the user in the lead-through control, may be limited to a predetermined value or less.

[0029] For example, as shown in Fig. 5, it is determined whether or not a flag It_end indicating that the process ended in an abnormal state is normal (false) (step S21), and if it is abnormal, the lead-through control is disabled (step S22). The flag It_end is initialized to normal (false) when the abnormal state is released.

[0030] On the other hand, if the flag It_end is false, it is determined whether the changeover switch 9 is on or not (step S23). If the changeover switch 9 is not on, the current position is stored as P1 (step S24).

[0031] On the other hand, when the changeover switch 9 is turned on, it is determined whether or not the absolute value of the force estimate is equal to or less than a predetermined threshold value T1 (step S25). When the absolute value of the estimate is equal to or less than the threshold value T1, the switching unit 7 is switched to enable the lead-through control (step S26), and the gain of the lead-through control is set to K0, increasing the sensitivity of the lead-through control (step S27).

[0032] On the other hand, if the absolute value of the estimated value is greater than the threshold T1, it is determined whether the distance between the current position and P1 stored in step S24 is equal to or less than a predetermined threshold L1 (step S28). If the distance is equal to or less than the threshold L1, the switching unit 7 switches to enable the lead-through control (step S29), and the gain of the lead-through control is set to K1, thereby reducing the sensitivity of the lead-through control (step S30).

[0033] The lead-through control continues until the changeover switch 9 is switched to the OFF state, in which case the process from step S25 is repeated (step S31). After the changeover switch 9 is switched to the OFF state, the lead-through control is disabled (step S22). On the other hand, if 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 is switched to abnormal (true) (step S32), and the lead-through control is switched to disabled (step S22).

[0034] That is, when the absolute value of the force estimate is greater than the threshold value T1, the load information that has been set may be inaccurate, so in addition to lowering the sensitivity of the lead-through control, the movement distance is prevented from becoming excessive. Even if inaccurate load information has been set, if the operating distance of the robot 100 is short, it is possible to prevent the robot 100 from moving significantly in a direction unintended by the user. This has the advantage of more reliably preventing the robot 100 from suddenly moving in a direction unintended by the user.

[0035] 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 may be limited. For example, by limiting the lead-through control to only the three wrist axes of the wrist unit 150, it is possible to prevent the robot 100 from moving significantly in a direction unintended by the user.

[0036] Next, a robot control device 50 according to a second embodiment of the present disclosure will be described below with reference to the drawings. 6 and 7, a robot control device 50 according to this embodiment differs from the robot control device 1 according to the first embodiment in that it includes a load information estimation unit 51. In the drawings, reference numeral 52 denotes a monitor.

[0037] For example, when load identification information and a load information estimation command are input to the teaching pendant 8, the load information estimation unit 51 sequentially displays a plurality of postures of the robot 100 for estimating the load information on the monitor 52. Then, the load information estimation unit 51 instructs the user to operate the robot 100 by lead-through control up to the displayed posture.

[0038] When the user turns on the changeover switch 9 in accordance with the instruction and the robot 100 is operated in the vicinity of the displayed posture by the lead-through control, 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 in accordance with the instruction, 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.

[0039] The load information estimation unit 51 can solve the equation of motion of the robot 100 by recording the external forces for three axes and the positions of the motor 170 in the postures of the wrist unit 150 along three or more axes in which gravity is applied differently, and estimate the mass of the load, the position of the center of gravity, and the offset amount of the torque sensor 160. The estimated mass and position of the center of gravity of the load are stored in the storage unit 4 in association with the identification information of the load. The estimated offset amount is stored in the offset amount storage unit 11 of the lead-through control unit 5.

[0040] In this case, in the robot control device 50 according to this embodiment, the load information estimation unit 51 waits for input of load identification information and a load information estimation command (step S11) as shown in Fig. 8. When the load identification information and the load information estimation command are input, the load information estimation unit 51 instructs the lead-through sensitivity setting unit to set the gain K of the lead-through control to K1, thereby reducing the sensitivity (step S12).

[0041] Then, the load information estimation unit 51 judges whether the changeover switch 9 is switched to the on state (step S13), and when it is switched, judges whether the axis operated by the lead-through control is the wrist axis (step S14). If the wrist axis is operated, the lead-through control is enabled (step S15), and if an axis other than the wrist axis is operated or if the changeover switch 9 is in the off state, the lead-through control is disabled (step S16).

[0042] When teaching the robot 100 using lead-through control after the load information estimation work is completed and accurate load information is stored in the storage unit, the lead-through control may be performed according to the flowchart of Fig. 4 or 5 without inputting an estimation command. Alternatively, for the loads for which the load information has been estimated, a flag indicating that estimation has been performed may be set, and when a load stored in the storage unit 4 is selected and lead-through control is started, if the flag is set, the gain may be set to K0.

[0043] In this way, according to the robot control device 50 of this embodiment, when issuing a command to estimate load information by the load information estimating unit 51, there is a possibility that accurate load information has not been stored, so the sensitivity of the lead-through control can be lowered to limit the operation of the robot 100. This makes it possible to prevent the robot 100 from suddenly operating in a direction against the user's intention based on inaccurate load information when operating the robot 100 by lead-through control during the load information estimation task.

[0044] In this embodiment, the operation of the robot 100 during the load information estimation task is restricted by lowering the sensitivity of the lead-through control and limiting the axis for which the lead-through control is effective to only the wrist axis, but only one of these may be used. Also, the moving distance of the robot 100 may be restricted in the same manner as in FIG. 5.

[0045] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the above-mentioned individual embodiments. Various additions, replacements, modifications, partial deletions, etc. are possible in these embodiments, within the scope of the gist of the invention, or within the scope of the idea and intent of the present invention derived from the contents described in the claims and their equivalents. For example, in the above-mentioned embodiments, the order of each operation and the order of each process are shown as examples, and are not limited to these. The same applies when numerical values ​​or formulas are used in the description of the above-mentioned embodiments. [Explanation of symbols]

[0046] 1,50 Robot control device 3 Position control section 4 Storage section 5 Lead-through control section 6 Lead-through sensitivity setting section (load suitability determination section) 9. Changeover switch 51 Load information estimation unit 100 Robots 160 Torque sensor (sensor) T1 threshold

Claims

1. A memory unit that stores load information including a mass and a center of gravity position of a load attached to a robot having a wrist axis; a lead-through control unit that controls a robot having a sensor that detects an 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 that determines whether the load information stored in the storage unit is appropriate; a load information estimation unit that records the external force detected by the sensor and a position of a motor of the robot with the robot set in a plurality of postures, and estimates the load information based on the recorded external force and the position of the motor, the load suitability determination unit determines that the load information stored in the storage unit may be inappropriate when the load information has not been estimated by the load information estimation unit; and A robot control device in which, when the load suitability determination unit determines that the load information may be inappropriate, the lead-through control unit limits the axes of the robot that move in response to the external force to only the wrist axis.

2. a position control unit that controls the robot based on a position command; a changeover switch for switching between control by the position control unit and control by the lead-through control unit; 2. The robot control device according to claim 1, wherein the load suitability determination unit determines that the load information may be inappropriate when an 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 value when the changeover switch is switched to control by the lead-through control unit.

3. The robot control device according to claim 2 , wherein, after the estimated value exceeds the threshold value and the motion of the robot is restricted, when the estimated value falls below the threshold value, the restriction is lifted.

4. 4. The robot control device according to claim 1, wherein when the load suitability determining unit determines that the load information is possibly inappropriate, sensitivity of the operation of the robot to the external force is reduced.

5. 5. The robot control device according to claim 1, further comprising a step of limiting an operating distance of the robot in response to the external force when the load suitability determining unit determines that the load information is possibly inappropriate.

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