Robot control device and robot control method

Abstract

A robot control device (20) constitutes a feedback control loop (L) in which a robot arm (2) is to be controlled, a position command (θref) for a motor (3) is to be a target value, and the motor position (θm) of the motor is to be a measurement value. The robot control device estimates, on the basis of a current command (Iref) for the motor and the motor speed (ωm) of the motor, an arm speed estimation value (ωˆL) for a robot arm and a torsion amount estimation value (θˆs) for a spring component (37) of a speed reducer (4), outputs a vibration suppression value (Twl) by multiplying the respective estimated values by corresponding state feedback gains (f1, f2) and executing addition of the resulting values; multiplies the vibration suppression value by a correction gain (Kon); and adds the resulting value to the feedback control loop. The correction gain is set so as to decrease immediately after a brake (38) of the motor is released and to increase as time (t) elapses after the brake is released.

Description

Robot control device and robot control method

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

[0002] A robot control device that controls a robot arm driven by a motor via a speed reducer is known. There is a spring component between the primary side and the secondary side of the speed reducer. When the robot arm is moved by the motor via the speed reducer, the robot arm vibrates due to the spring component of the speed reducer. The vibration of the robot arm leads to a decrease in the working accuracy of the robot arm, which is not preferable.

[0003] There is a method of measuring the torsional amount of the spring component of the speed reducer and the speed of the robot arm, and correcting the robot arm based on the measured values. However, for this purpose, it is necessary to add a sensor to the configuration, which is a factor in increasing costs.

[0004] Therefore, in the robot control device according to Patent Document 1, a state observer is configured, and the state observer estimates an estimated value of the arm speed of the robot arm and an estimated value of the torsional amount of the spring component of the speed reducer based on the current command for the motor and the motor speed of the motor, and corrects the robot arm based on the estimated values, thereby suppressing the vibration caused by the spring component of the speed reducer.

[0005] Japanese Unexamined Patent Application Publication No. 2009-028865

[0006] In the conventional technology as described above, immediately after the robot control device starts energizing the motor, that is, immediately after releasing the brake of the motor, the robot arm drops slightly, and then, when the position control of the motor starts, the robot arm returns to its original position. At that time, the current command for the motor and the motor speed of the motor change suddenly.

[0007] Thus, immediately after releasing the motor brake, the current command and motor speed, which are input values ​​to the state observer, fluctuate rapidly, causing the arm speed estimate and torsion amount estimate, which are output values ​​from the state observer, to also fluctuate rapidly. As a result, immediately after releasing the motor brake, the feedback control adversely affects the behavior of the robot arm, causing the robot arm to vibrate, and consequently resulting in abnormal noise and shaking.

[0008] This disclosure describes a method for suppressing vibrations of a robot arm by feedback control immediately after releasing the motor brake.

[0009] The robot control device according to this disclosure is a robot control device equipped with a state observer that controls a robot arm moved by a motor via a reduction gear. The robot control device controls the robot arm as the control target, and configures a feedback control loop in which the position command to the motor is the target value and the motor position of the motor is the measured value. The state observer estimates the arm speed of the robot arm and the torsion amount of the spring component of the reduction gear based on the current command to the motor and the motor speed of the motor. The robot control device outputs a vibration suppression value by multiplying the arm speed estimate and the torsion amount estimate by a state feedback gain and adding them together. The robot control device adds the vibration suppression value multiplied by a correction gain to the feedback control loop. The robot control device sets the correction gain to decrease immediately after the motor brake is released and to increase as time elapses since the brake was released.

[0010] The robot control method according to this disclosure is a robot control method for controlling a robot arm moved by a motor via a reduction gear, wherein the robot arm is the control target, a position command to the motor is set as the target value, and a feedback control loop is configured with the motor position of the motor as the measured value, an estimated arm speed of the robot arm and an estimated torsion amount of the spring component of the reduction gear are estimated based on the current command to the motor and the motor speed of the motor, a vibration suppression value is output by multiplying the estimated arm speed and the estimated torsion amount by a state feedback gain and adding them, the vibration suppression value is multiplied by a correction gain and added to the feedback control loop, and the correction gain is set to decrease immediately after the motor brake is released and to increase as time elapses since the brake was released.

[0011] Furthermore, the robot control device according to this disclosure is a robot control device that controls a robot arm moved by a motor via a reduction gear, and allows displacement of the robot arm immediately after the brake of the motor is released, and corrects the position of the robot arm so that the displacement of the robot arm decreases as time elapses since the brake was released.

[0012] According to this disclosure, vibrations of the robot arm can be suppressed by feedback control immediately after the motor brake is released.

[0013] Figure 1 is a diagram showing the configuration of a robot according to an embodiment of the present disclosure. Figure 2 is a diagram showing the configuration of the motor and reducer at each joint of the robot arm in the embodiment. Figure 3 is a block diagram showing the feedback control loop by the robot control device in the first embodiment. Figure 4 is a graph showing the details of the correction gain in the embodiment. Figure 5 is a flowchart showing the control flow of the robot control device in the embodiment. Figure 6 is a block diagram showing the feedback control loop by the robot control device in the second embodiment of the present disclosure.

[0014] The embodiments of this disclosure will be described in detail below with reference to the drawings. The following descriptions of each embodiment are illustrative in nature and are not intended to limit the disclosure, its applications, or its uses in any way.

[0015] <First Embodiment> (Robot) First, the first embodiment of this disclosure will be described.

[0016] Figure 1 is a diagram showing the configuration of robot 1 according to an embodiment of the present disclosure.

[0017] Robot 1 is a multi-jointed robot. Robot 1 comprises a robot arm 2 and a plurality of joints J1 to J6. A robot control device 20 is connected to Robot 1.

[0018] The robot arm 2 is divided into several parts. Each of the connecting parts (six connecting parts) in the robot arm 2 is provided with joints J1 to J6. The robot arm 2 has joints J1 to J6. Joints J1 to J6 include a first joint J1, a second joint J2, a third joint J3, a fourth joint J4, a fifth joint J5, and a sixth joint J6.

[0019] Joints J1 to J3 are the three main axes that determine the overall posture of the robot arm 2, and joints J4 to J6 are the three wrist axes that determine the direction of the tip of the robot arm 2. The first joint J1 is a pivot axis that rotates the robot arm 2. For example, a laser output device (not shown) is attached to the tip of the robot arm 2. The laser output device cuts the workpiece by irradiating it with laser light.

[0020] Figure 2 shows the configuration of the motor 3 and reduction gear 4 in each of the joints J1 to J6 of the robot arm 2 in the embodiment.

[0021] A motor 3 is connected to each of the joints J1 to J6 of the robot arm 2 via a reduction gear 4.

[0022] In Figure 2, a portion of the robot arm 2 is shown as a load 30. The load 30 includes a first arm 31, a motor 3, a gearbox 4, and a second arm 35. The first arm 31 is a base for mounting the motor 3. The motor 3 is connected to the first arm 31. The gearbox 4 includes a primary side 32 connected to the motor 3 and a secondary side 33 having a bearing 34. The second arm 35 is rotatably connected to the secondary side 33 of the gearbox 4 via the bearing 34. The primary side 32 of the gearbox 4 is coupled to the rotor 36 (rotating shaft) of the motor 3.

[0023] The primary side 32 of the reduction gear 4 rotates by the amount of the motor position θm (motor rotation position) based on the current command Iref sent from the robot control device 20. The reduction gear 4 converts the motor position θm into the arm position θL (arm rotation position) by the reduction ratio Rg. In this way, the robot arm 2 is moved by the motor 3 via the reduction gear 4.

[0024] A spring component 37 exists between the primary side 32 and the secondary side 33 in the reduction gear 4. The gap between the primary side 32 and the secondary side 33 in the reduction gear 4 is backlash.

[0025] The motor 3 is equipped with a brake 38 to suppress the rotation of the rotor 36. The brake 38 functions when the motor 3 is not energized, suppressing the rotation of the rotor 36. The brake 38 is released when the motor 3 is energized, i.e., by the current command Iref, allowing the rotor 36 to rotate.

[0026] (Robot control device) Figure 3 is a block diagram showing the feedback control loop L by the robot control device 20 in the first embodiment.

[0027] The robot control device 20 controls the robot arm 2, and more specifically, the load 30 described above. The robot control device 20 includes a position control unit 21, a speed PI control unit 22, and a state observer 50.

[0028] The position control unit 21 receives a position command θref (angular position command) for the motor 3. Furthermore, the position control unit 21 receives the current motor position θm (motor angular position) of the motor 3 as a feedback value. The motor position θm is measured by an encoder (not shown). The robot control device 20 controls the load 30 of the robot arm 2, and configures a feedback control loop L with the position command θref for the motor 3 as the target value and the motor position θm of the motor 3 as the measured value. The position control unit 21 outputs a speed command ωref (angular velocity command) for the motor 3.

[0029] The speed PI control unit 22 receives the speed command ωref for the motor 3, which is output from the position control unit 21. Downstream of the speed PI control unit 22, the vibration suppression correction value Kon × Twl, which is obtained by multiplying the vibration suppression value Twl (described later) by the correction gain Kon, is input as a feedback value. The speed PI control unit 22 outputs the current command Iref for the motor 3. In Figure 3, the correction gain Kon 70 is shown as a functional block.

[0030] The current command Iref is input to the load 30. The functional block of the load 30 represents the physical phenomena within the load 30 as functional blocks. In the functional block of the load 30, the torque constant Kt71 of the motor 3, the reciprocals of the reduction ratio 1 / Rg72,74 of the reducer 4, the spring constant Ks73 of the reducer 4, the amount of torsion θs generated in the spring component 37 between the primary side 32 and the secondary side 33 of the reducer 4, the differential element s, and the integral element 1 / s75 are shown. Note that in Figure 3, the torque constant Kt71, the reciprocals of the reduction ratio 1 / Rg72,74, the spring constant Ks73, and the integral element 1 / s75 are each shown as functional blocks.

[0031] The motor transfer function 40 and the load transfer function 41 are mathematical formulas (models) of the physical phenomena in the motor 3 and load 30, respectively. The motor transfer function 40 is given by 1 / (Jm × s + Dm), and the load transfer function 41 is given by 1 / (JL × s + DL). In Figure 3, the motor transfer function 40 and the load transfer function 41 are shown as functional blocks.

[0032] The motor transfer function 40 includes the moment of inertia Jm and the viscous friction coefficient Dm about the rotation axis between the rotor 36 of the motor 3 and the primary side 32 of the reduction gear 4.

[0033] The load transfer function 41 includes the moment of inertia JL and the viscous friction coefficient DL around the rotation axis between the second arm 35 and the secondary side 33 of the reduction gear 4.

[0034] The load 30 outputs the arm velocity ωL (arm angular velocity) of the robot arm 2.

[0035] Furthermore, the current motor speed ωm of motor 3 is output from the load 30 to the robot control device 20. The motor speed ωm is then input to the integral element 1 / s81, and the motor position θm is output. The motor position θm is sent to the position control unit 21 as a feedback value. Note that the motor speed ωm and motor position θm may be measured by an encoder (not shown).

[0036] The state observer 50 receives a current command Iref for the motor 3 and the motor speed ωm of the motor 3 as input. The state observer 50 outputs an estimated arm speed ω^L (estimated arm angular velocity), which is an estimated value of the arm speed ωL of the robot arm 2, and an estimated torsion amount θ^s, which is an estimated value of the torsion amount θs of the spring component 37 of the reduction gear 4. In other words, the robot control device 20 estimates the estimated arm speed ω^L of the robot arm 2 and the estimated torsion amount θ^s of the spring component 37 of the reduction gear 4 based on the current command Iref for the motor 3 and the motor speed ωm of the motor 3, as determined by the state observer 50.

[0037] The robot control device 20 outputs a vibration suppression value Twl by multiplying the estimated arm speed ω^L and the estimated torsion amount θ^s by the state feedback gain f82 and adding them together. The estimated torsion amount θ^s is multiplied by the first state feedback gain f1. The estimated arm speed ω^L is multiplied by the second state feedback gain f2. Furthermore, the motor speed ωm is multiplied by the third state feedback gain f3. When these three values, after being multiplied by each state feedback gain f1 to f3, are added together, the vibration suppression value Twl is obtained. In Figure 3, the state feedback gain f82 is shown as a functional block.

[0038] The vibration suppression value Twl is input to the correction gain Kon70. The correction gain Kon70 corrects the vibration suppression value Twl and outputs a vibration suppression correction value Kon×Twl. The vibration suppression correction value Kon×Twl is input as a feedback value to the downstream side of the speed PI control unit 22.

[0039] In this way, the robot control device 20 multiplies the vibration suppression value Twl by the correction gain Kon 70 to obtain a vibration suppression correction value Kon × Twl, which is then added to the feedback control loop L.

[0040] The correction gain Kon 70 receives the brake release signal B. The brake release signal B is sent to release the brake 38 that stops the rotation of the rotor 36 in the motor 3 when power is first supplied to the motor 3.

[0041] (Correction Gain) Figure 4 is a graph showing the details of the correction gain Kon 70 in the embodiment. In Figure 4, the horizontal axis represents time t (time) [s], and the vertical axis represents the correction gain Kon [%].

[0042] The robot control device 20 sets the correction gain Kon to a first value P1 when the brake release signal B is not input. In this embodiment, the first value P1 is 100%.

[0043] The robot control device 20 sets the correction gain Kon to decrease immediately after the brake 38 of the motor 3 is released by the input of the brake release signal B, and to increase as time t elapses after the brake 38 of the motor 3 is released. In this specification, "immediately after" includes the time simultaneous with the input of the brake release signal B and a short time thereafter.

[0044] Specifically, the correction gain Kon decreases from the first value P1 to the second value P2 immediately after the brake 38 of the motor 3 is released by the input of the brake release signal B, and increases from the second value P2 to the first value P1 as time t elapses after the brake 38 of the motor 3 is released. The second value P2 is smaller than the first value P1. In the embodiment, the second value P2 is, for example, 20%.

[0045] More specifically, the correction gain Kon discontinuously decreases from the first value P1 to the second value P2 immediately after the brake 38 of the motor 3 is released by the input of the brake release signal B, and is set to continuously increase from the second value P2 to the first value P1 as time t elapses after the brake 38 of the motor 3 is released. That is, the correction gain Kon does not take a value between the first value P1 and the second value P2 immediately after the brake 38 is released, and instantaneously (at once) decreases from the first value P1 to the second value P2, and is set to continuously increase from the second value P2 to the first value P1 while taking a value between the second value P2 and the first value P1 as time t elapses after the brake 38 is released.

[0046] The correction gain Kon may be set to increase linearly from the second value P2 to the first value P1 as time t elapses after the brake 38 of the motor 3 is released. In the embodiment, after the input of the brake release signal B, the correction gain Kon is a linear function of time t with a positive slope.

[0047] The brake 38 is released by the start of the input of the current command Iref to the motor 3. Then, the brake release signal B is sent to and input to the correction gain Kon70.

[0048] (Flowchart) Figure 5 is a flowchart showing the control flow of the robot control device 20 in the embodiment.

[0049] The control flow starts from the start. In the first step S1, the robot control device 20 sets the correction gain Kon70 to the first value P1. The first value P1 is, for example, 100%.

[0050] In the second step S2, the speed PI control unit 22 starts transmitting the current command Iref to the motor 3.

[0051] In the third step S3, the brake 38 of the motor 3 is released.

[0052] In the fourth step S4, the robot control device 20 inputs the brake release signal B to the correction gain Kon70.

[0053] In the fifth step S5, the robot control device 20 decreases the correction gain Kon70 from the first value P1 to the second value P2. The second value P2 is, for example, 20%.

[0054] In the sixth step S6, the robot control device 20 increases the correction gain Kon70 from the second value P2 to the first value P1 according to the passage of time t after the brake 38 of the motor 3 is released.

[0055] Then, the control flow reaches the end.

[0056] (Function and Effect) Immediately after the brake 38 of the motor 3 is released, the robot arm 2 drops slightly, and then, by starting the position control of the motor 3, the robot arm 2 returns to the original position. At that time, the current command Iref for the motor 3 and the motor speed ωm of the motor 3 change suddenly.

[0057] Immediately after the brake 38 of motor 3 is released, the current command Iref and motor speed ωm, which are input values ​​to the state observer 50, fluctuate rapidly. As a result, the arm speed estimate ω^L and the torsion amount estimate θ^s, which are output values ​​from the state observer 50, also fluctuate rapidly. Consequently, the vibration suppression value Twl, obtained by multiplying the torsion amount estimate θ^s and arm speed estimate ω^L by the state feedback gains f1 and f2, respectively, and adding them together, also fluctuates rapidly. As a result, immediately after the brake 38 of motor 3 is released, the feedback control adversely affects the behavior of the robot arm 2, causing the robot arm 2 to vibrate, and consequently resulting in abnormal noise and shaking.

[0058] Therefore, in this embodiment, the vibration suppression value Twl is multiplied by the correction gain Kon to output the vibration suppression correction value Kon × Twl. Furthermore, the correction gain Kon is made smaller immediately after the brake 38 of the motor 3 is released, and is made larger as time t elapses since the brake 38 of the motor 3 was released.

[0059] As a result, even if the vibration suppression value Twl fluctuates rapidly immediately after the brake 38 of the motor 3 is released, the rapid fluctuation of the vibration suppression correction value Kon × Twl can be suppressed by reducing the correction gain Kon.

[0060] Therefore, adverse effects on the behavior of the robot arm 2 can be suppressed, vibrations of the robot arm 2 can be suppressed, and consequently, abnormal noises and shaking can be suppressed. According to this embodiment, vibrations of the robot arm 2 can be suppressed by feedback control immediately after the brake 38 of the motor 3 is released.

[0061] In other words, the robot control device 20 is a device that controls the robot arm 2, which is moved by the motor 3 via the reduction gear 4. It allows displacement of the robot arm 2 immediately after the brake 38 of the motor 3 is released, and corrects the position of the robot arm 2 so that the displacement of the robot arm 2 decreases as time elapses since the brake 38 was released.

[0062] Furthermore, the correction gain Kon is reduced from a first value P1 to a second value P2 after the motor 3's brake 38 is released, and then increased from the second value P2 to the first value P1 as time t elapses since the motor 3's brake 38 was released. In this way, after a predetermined time t has elapsed since the motor 3's brake 38 was released, the original first value P1 can be used as the correction gain Kon.

[0063] Furthermore, after the brake 38 of motor 3 is released, the correction gain Kon can be instantaneously reduced from the first value P1 to the second value P2 by discontinuously decreasing the correction gain Kon from the first value P1 to the second value P2. Then, in accordance with the elapsed time t since the brake 38 of motor 3 was released, the correction gain Kon can be gradually increased from the second value P2 to the first value P1 by continuously increasing the correction gain Kon from the second value P2 to the first value P1.

[0064] Furthermore, by linearly increasing the correction gain Kon from a second value P2 to a first value P1 in accordance with the elapsed time t since the motor 3's brake 38 was released, the correction gain Kon can be gradually increased from a second value P2 to a first value P1 with a simple configuration.

[0065] The brake 38 is released when the transmission of the current command Iref to the motor 3 begins. In this way, the release of the brake 38 of the motor 3 and the start of the transmission of the current command Iref to the motor 3 can be synchronized.

[0066] <Second Embodiment> Next, a second embodiment of the present disclosure will be described.

[0067] Figure 6 is a block diagram showing the feedback control loop by a robot control device in a second embodiment of the present disclosure.

[0068] In the following description, components similar to those in the first embodiment described above will be denoted by the same reference numerals, and detailed explanations will be omitted.

[0069] As shown by the dashed line in the lower right portion of Figure 6, the robot control device 90 of the second embodiment includes an update unit 60. The update unit 60 receives the moment of inertia JL of the robot arm 2 as input. The update unit 60 outputs an observer gain K. The observer gain K changes the state observer 50 (more specifically, the parameters that constitute the state observer 50). The update unit 60 also changes the state feedback gain f. This method is called the FDTD method (Finite-Difference Time-Domain method).

[0070] In the second embodiment, the robot control device 90 uses an update unit 60 to change at least one of the state observer 50 and the state feedback gain f82 based on the moment of inertia JL of the robot arm 2.

[0071] The update unit 60 can maintain at least one of the state observer 50 and the state feedback gain f82 to a suitable state, taking into account the moment of inertia JL of the robot arm 2.

[0072] The other configurations are the same as in the first embodiment.

[0073] <Other Embodiments> Although the present disclosure has been described above with reference to preferred embodiments, this description is not limiting, and various modifications, substitutions, and combinations are, of course, possible.

[0074] For example, the value of the correction gain Kon does not necessarily have to return from the second value P2 to the first value P1 as time t elapses since the motor 3's brake 38 was released; it may remain at a value just before the first value P1 (a value smaller than the first value P1 and larger than the second value P2).

[0075] The robot control method according to this disclosure is a method for controlling a robot arm 2 that is moved by a motor 3 via a reduction gear 4. The robot control method uses the robot arm 2 as the control target, sets a position command θref for the motor 3 as the target value, and configures a feedback control loop L with the motor position θm of the motor 3 as the measured value. A state observer 50 estimates the arm speed of the robot arm 2 ω^L and the torsion amount estimate θ^s of the spring component 37 of the reduction gear 4 based on the current command Iref for the motor 3 and the motor speed ωm of the motor 3. The vibration suppression value Twl is output by multiplying the torsion amount estimate θ^s and the arm speed estimate ω^L by state feedback gains f1 and f2, respectively, and adding them together. The vibration suppression value Twl is multiplied by a correction gain Kon and added to the feedback control loop L. The correction gain Kon is set to decrease immediately after the brake 38 of the motor 3 is released and to increase as time t elapses since the brake 38 was released.

[0076] This disclosure is extremely useful and has high potential for industrial application, as it can be applied to robot control devices and robot control methods, etc.

[0077] 1 Robot 2 Robot arm 3 Motor 4 Reducer 20, 90 Robot control device 21 Position control unit 22 Speed ​​PI control unit 30 Load 31 First arm 32 Primary side 33 Secondary side 34 Bearing 35 Second arm 36 Rotor 37 Spring component 38 Brake 40 Motor transfer function 41 Load transfer function 50 State observer 60 Update unit 70 Correction gain Kon 71 Torque constant Kt 72, 74 Reciprocal of reduction ratio 1 / Rg 73 Spring constant Ks 75 Integral element 1 / s 81 Integral element 1 / s 82 State feedback gain f B Brake release signal Iref Current command J1-J6 Joint JL, Jm Moment of inertia Kon × Twl Vibration suppression correction value K Observer gain L Feedback control loop P1 First value P2 Second value s Differential element S1-S6 Step Twl Vibration suppression value t Time θref Position command θs Torsion amount θL Arm position θm Motor position ωm Motor speed ωref Speed ​​command ω^L Arm speed estimate θ^s Torsion amount estimate

Claims

1. A robot control device equipped with a state observer for controlling a robot arm moved by a motor via a reduction gear, wherein the robot control device configures a feedback control loop with the robot arm as the control target, a position command to the motor as the target value, and the motor position of the motor as the measured value, the state observer estimates an arm speed estimate of the robot arm and an estimated torsion amount estimate of the spring component of the reduction gear based on a current command to the motor and the motor speed of the motor, the robot control device outputs a vibration suppression value by multiplying the arm speed estimate and the torsion amount estimate by a state feedback gain and adding them, the robot control device adds the vibration suppression value to the feedback control loop by multiplying it by a correction gain, and the robot control device sets the correction gain to be small immediately after the motor brake is released and large as time elapses since the brake was released.

2. A robot control device according to claim 1, wherein the robot control device is configured such that the correction gain decreases from a first value to a second value immediately after the brake is released, and increases from the second value to the first value as time elapses since the brake was released.

3. A robot control device according to claim 2, wherein the robot control device is set such that the correction gain becomes discontinuously smaller from a first value to a second value after the brake is released, and continuously larger from a second value to a first value as time elapses since the brake was released.

4. A robot control device according to claim 3, wherein the robot control device is set to increase the correction gain linearly from the second value to the first value in accordance with the elapsed time since the brake was released.

5. A robot control device according to any one of claims 1 to 4, wherein the brake is released by the current command to the motor.

6. A robot control device according to any one of claims 1 to 4, wherein the robot control device further comprises an update unit, the update unit changes at least one of the state observer and the state feedback gain based on the moment of inertia of the robot arm.

7. A robot control method for controlling a robot arm driven by a motor via a reduction gear, comprising: configuring a feedback control loop with the robot arm as the control target, a position command to the motor as the target value, and the motor position of the motor as the measured value; estimating an estimated arm speed of the robot arm and an estimated torsion amount of the spring component of the reduction gear based on a current command to the motor and the motor speed of the motor; outputting a vibration suppression value by multiplying the estimated arm speed and the estimated torsion amount by a state feedback gain and adding them; adding the vibration suppression value to the feedback control loop after multiplying it by a correction gain; and setting the correction gain to decrease immediately after the motor brake is released and increase as time elapses since the brake was released.

8. A robot control device for controlling a robot arm driven by a motor via a reduction gear, wherein the robot control device allows displacement of the robot arm immediately after the motor brake is released, and corrects the position of the robot arm so that the displacement of the robot arm decreases as time elapses since the brake was released.

Images