JP2016068171A - Robot control device and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot control device and a robot control method which can reduce positional deviations between motors in a servo control structure configured to drive one driving shaft with at least two motors.SOLUTION: A robot control device, which comprises an original current command value generating portion that generates an original current command value on the basis of a position command value and a master position, and one or more compensation elements for compensating slave speed corresponding to respective deviations of the slave speed on the basis of one or more deviations of the slave speed relative to master speed, distributes the original current command value so as to generate the master current command value and one or more slave current command values, drives a master motor on the basis of the master current command value, and performs control so as to drive one or more slave motors on the basis of current command values to which are added respectively outputs of compensation elements corresponding to one or more slave current command values respectively corresponding to one or more slave motors respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a robot control apparatus and control method, and more particularly to a robot control apparatus and control method having a servo control structure that drives one drive shaft with at least two motors.

  In a robot such as a machine tool, when the load applied to the drive shaft that drives the movable part that defines the operation of the robot is large and the drive shaft cannot be driven by only one motor, the two motors are connected to each other. A dual servo control structure is known that controls two motors so as to drive one drive shaft. In the conventional dual servo control structure, the two motors are fed back by feeding the current position of the one motor to the control system of the two motors based on the position command value to one of the two motors. Is subjected to feedback control.

  Furthermore, as a configuration for performing more stable control in the dual servo control structure, for example, a configuration as in Patent Document 1 has been proposed. In the configuration of Patent Document 1, the torque command to the slave motor is corrected according to the difference between the torque command to one motor (master motor) and the torque command to the other motor (slave motor).

JP 2003-79180 A

  However, even with such a configuration, there is a problem that even if a motor having the same performance is controlled in the same manner, a deviation in the position of the other motor occurs with respect to one motor. Such a problem also occurs in a server control structure in which three or more motors are connected to each other and three or more motors are controlled to drive one drive shaft.

  The present invention has been made to solve the above problems, and a robot capable of reducing a positional deviation between motors in a servo control structure in which one drive shaft is driven by at least two motors. An object of the present invention is to provide a control device and a robot control method.

  A robot control apparatus according to an aspect of the present invention includes a drive shaft that drives a movable part that defines the operation of the robot, a master motor that rotationally drives the drive shaft, and one or more slaves that rotationally drive the drive shaft. A master position acquisition unit that acquires a master position that is a rotational position of the master motor, and generates an original current command value based on the position command value and the master position. An original current command value generation unit that performs a master speed acquisition unit that acquires a master speed that is the speed of the master motor, and a slave speed acquisition unit that acquires one or more slave speeds that are the speed of the one or more slave motors. And one or more for compensating the slave speed corresponding to each deviation based on one or more deviations of the slave speed with respect to the master speed. A compensation element, distributing the original current command value to generate a master current command value and one or more slave current command values, driving the master motor based on the master current command value, Control is performed to drive one or more slave motors based on current command values obtained by adding outputs of the compensation elements corresponding to the one or more slave current command values respectively corresponding to the slave motors. Is.

  According to one aspect, there is an effect that the positional deviation between the motors can be reduced in the servo control structure in which one drive shaft is driven by at least two motors.

FIG. 1 is a block diagram showing a schematic configuration of a robot control apparatus according to the first embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of a robot control apparatus according to a modification of the first embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of a robot control apparatus according to the second embodiment of the present invention. FIG. 4 is a graph showing temporal changes in torque and speed of the master motor and slave motor in this embodiment. FIG. 5 is an enlarged view of a portion V in the graph showing the temporal change of the speed shown in FIG. It is a graph which shows the time change of the slave current command value after compensation in a present Example with a comparative example. FIG. 7 is a graph showing temporal changes in torque and speed of the master motor and slave motor in the comparative example. FIG. 8 is an enlarged view of a part VIII in the graph showing the temporal change of the speed shown in FIG.

<Background of obtaining one embodiment of the present invention>
As described above, in the conventional dual servo control structure, there is a problem that even if a motor having the same performance is controlled in the same manner, a deviation of the position of the other motor occurs with respect to one motor.

  Therefore, the inventors of the present invention have conducted intensive research to solve the above problems. As a result, the inventors of the present invention analyze the speed of each of the two motors that have performed dual servo control, so that the other motor (for example, the master motor) is changed with respect to the speed change of the other motor (for example, the master motor). It was found that the change in the speed of the slave motor could not follow, and the difference in speed between the two motors widened due to vibration. Therefore, the inventors of the present invention assume that the displacement difference between the two motors is proportional to the speed difference between the two motors, and use the current command value common to both, while the current command value of the slave motor uses the speed difference between the two motors. The control mode of adding a compensation value based on the above has been conceived. Thereby, the speed change between a master motor and a slave motor can be suppressed, and the position deviation between motors can be made small.

<Outline of One Embodiment of the Present Invention>
The present invention has been conceived based on the inventors' knowledge as described above. A robot control apparatus according to an aspect of the present invention includes a drive shaft that drives a movable part that defines the operation of the robot, a master motor that rotationally drives the drive shaft, and one or more slaves that rotationally drive the drive shaft. A master position acquisition unit that acquires a master position that is a rotational position of the master motor, and generates an original current command value based on the position command value and the master position. An original current command value generation unit that performs a master speed acquisition unit that acquires a master speed that is the speed of the master motor, and a slave speed acquisition unit that acquires one or more slave speeds that are the speed of the one or more slave motors. And one or more for compensating the slave speed corresponding to each deviation based on one or more deviations of the slave speed with respect to the master speed. A compensation element, distributing the original current command value to generate a master current command value and one or more slave current command values, driving the master motor based on the master current command value, Control is performed to drive one or more slave motors based on current command values obtained by adding outputs of the compensation elements corresponding to the one or more slave current command values respectively corresponding to the slave motors. Is.

  According to the above configuration, the common current command value common to the master motor and the slave motor is generated from the position command value. The master current command value distributed from the original current command value is input to the master motor, and the slave motor is supplied to the slave motor based on the deviation between the master speed and the slave speed. The current command value with the compensated slave speed added is input. In this way, while using a current command value common to both, a compensation value based on the speed difference between the two is added to the current command value of the slave motor. Thereby, the speed change between a master motor and a slave motor can be suppressed, and the position deviation between motors can be made small.

  The compensation element may include a proportional element. As a result, compensation proportional to the speed deviation between the master motor and the slave motor is performed, so that a speed change between the master motor and the slave motor can be suppressed. Furthermore, the gain of the proportional element may be set to a value such that the deviation between the master speed and the slave speed monotonously approaches zero. In this way, by setting the gain to a value such that the speed deviation between both approaches monotonically, the speed change between the two can be suppressed more efficiently.

  The master speed acquisition unit includes the master position acquisition unit and a differentiator that differentiates the master position and outputs the master speed, and the slave speed acquisition unit is a slave that is a rotational position of the slave motor. You may provide the slave position acquisition part which acquires a position, and the differentiator which differentiates the said slave position and outputs the said slave speed. Thereby, the structure of this invention is easily realizable with the existing structure.

  A robot control method according to another aspect of the present invention includes a drive shaft that drives a movable part that defines the operation of the robot, a master motor that rotationally drives the drive shaft, and one or more that rotationally drives the drive shaft. A master motor that is a rotational position of the master motor, and distributes an original current command value generated based on the position command value and the master position. Generating a master current command value and one or more slave current command values, obtaining a master speed that is the speed of the master motor, and obtaining one or more slave speeds that are the speed of the one or more slave motors, respectively. Calculating a compensation value for compensating the slave speed corresponding to each deviation based on one or more deviations of the slave speed with respect to the master speed; The master motor is driven based on a current command value, and the compensation value corresponding to each of the one or more slave current command values corresponding to the one or more slave motors is added. One or more slave motors are driven.

  According to the above method, the common current command value common to the master motor and the slave motor is generated from the position command value. A master current command value distributed from the current current command value is input to the master motor, and a slave current command value distributed from the original current command value is input to the slave motor based on a deviation between the master speed and the slave speed. The current command value that compensates for the slave speed is input. In this way, while using a current command value common to both, a compensation value based on the speed difference between the two is added to the current command value of the slave motor. Thereby, the speed change between a master motor and a slave motor can be suppressed, and the position deviation between motors can be made small.

<Embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted.

<First Embodiment>
First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of a robot control apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the robot control apparatus 1 in the present embodiment rotationally drives the drive shaft 2 via a drive shaft 2 that drives a movable part that defines the operation of the robot and a master power transmission mechanism 3. A master motor 4 and a slave motor 6 that rotationally drives the drive shaft 2 via a slave power transmission mechanism 5 are provided. Furthermore, the control device 1 controls the master motor drive unit 14 that drives the master motor 4 based on the master current command value I _M (described later) and the slave motor 6 based on the compensated slave current command value I _CS (described later). And a slave motor drive unit 15 for driving.

  The robot to which this embodiment is applied is configured as a multi-joint robot including, for example, a plurality of arm members and a plurality of joints (rotating shafts) that connect these members. That is, the rotation shaft that rotates a specific arm member in the multi-joint robot as a movable portion is the drive shaft 2 in the present embodiment. The master power transmission mechanism 3 is not particularly limited as long as it is a mechanism that transmits the rotational power output from the master motor 4 to the drive shaft 2. For example, the master power transmission mechanism 3 can employ various configurations such as a gear mechanism, an arm mechanism, or a combination thereof. The slave power transmission mechanism 5 is also configured similarly to the master power transmission mechanism 3 as a mechanism for transmitting the rotational power output from the slave motor 6 to the drive shaft 2.

  Each of the master power transmission mechanism 3 and the slave power transmission mechanism 5 has a predetermined reduction ratio with respect to the drive shaft 2. In the present embodiment, the reduction ratio of the master power transmission mechanism 3 and the reduction ratio of the slave power transmission mechanism 5 are set to the same value.

Furthermore, the control device 1 includes a master speed acquisition unit 7 that acquires a value (master speed ω _M ) indicating the speed (current speed) of the master motor 4 and a value (slave speed) indicating the speed (current speed) of the slave motor 6. and a slave speed acquisition unit 8 that acquires ω _S ). In the present embodiment, the master speed acquisition unit 7 differentiates the master position P _M with a master position acquisition unit 9 that acquires a value (master position P _M ) indicating the rotational position (current position) of the master motor 4. a differentiator 10 for outputting a master speed omega _M, and a. Similarly, the slave speed acquiring unit 8, the slave position acquiring unit 11 for acquiring the value (slave position P _S) indicating the rotational position of the slave motor 6, and outputs the slave speed omega _S by differentiating the slave position P _S A differentiator 12. The rotation position acquired by the position acquisition units 9 and 11 means the rotation angle position (the number of rotations and the rotation angle from the reference position) of the output shafts (motor shafts) of the motors 4 and 6. For example, the position acquisition units 9 and 11 are configured by an encoder, a resolver, or the like.

Furthermore, the control device 1 includes an original current command value generation unit 13 that generates an original current command value Io based on the position command value P _o and the master position P _M. The original current command value generation unit 13 is configured as a functional block of a computer including a CPU, a memory, an input / output device for various signals, and the like. The position command value _Po is input from the outside as a value indicating the rotational position (the rotational speed and rotational angle from the reference position) of the motor shaft of the master motor 4.

The original current command value I _o generated by the original current command value generation unit 13 is evenly distributed by branching to the route to the master motor 4 and the route to the slave motor 6, so that the master current command value I _M and the slave the current command value _{I S.} The master current command value _IM is input to the master motor drive unit 14. Master motor driver 14 drives the master motor 4 so as to generate an output torque T _M based on a master current command value I _M that is input, the master motor 4 outputs the rotational power.

Further, the control unit 1 is provided with a compensating element 16 for compensating the slave speed omega _S based on the deviation Δω slave velocity omega _S to the master speed omega _M. The compensation element 16 is also configured as a functional block of the computer, like the original current command value generation unit 13. In the present embodiment, the compensation element 16 is configured to include a proportional element (gain G). Furthermore, the compensation element 16 is configured to include a converted value for adding the speed deviation Δω to the current command value.

  The compensation element 16 has at least one of a proportional element, an integral element, and a derivative element as the gain G. A plurality of these elements may be combined. That is, not only proportional compensation but also PI compensation or PID compensation may be performed.

The compensation value GΔω output from the compensation element 16 is added to the slave current command value I _S and is input to the slave motor drive unit 15 as the compensated slave current command value I _CS . The slave motor drive unit 15 drives the slave motor 6 to generate an output torque T _S based on the input compensated slave current command value I _CS, the slave motor 6 outputs rotational power.

The master motor 4 and feeds back the current value corresponding to the output torque T _M generated, and is configured to perform PI compensation for the deviation between the feedback current value and the master current command value I _M. Similarly, the slave motor 6 feeds back a current value corresponding to the output torque T _S generated, is configured to perform a PI compensation for the deviation of the feedback current value and the compensated slave current command value I _CS ing.

According to the control apparatus 1 of the robot in this embodiment, the original current command value I _o which is common to each of the position command value P _o to the master motor 4 and slave motor 6 is generated. To the master motor 4 is input original current command value I _o master current distributed from the command value I _M is the the slave motor 6, the slave speed based on the deviation Δω between the master velocity omega _M and a slave speed omega _S ω current command value compensation amount is added to _S (compensated slave current command value) I _CS is input. In this way, while using a common source current command value I _o to both, they are added to the compensation value GΔω based on both the speed difference Δω as a current command value I _CS to the slave motor 6. Thereby, the speed change between the master motor 4 and the slave motor 6 can be suppressed, and the positional deviation between the motors 4 and 6 can be reduced.

In addition, since the compensation element 16 includes a proportional element (gain G), compensation proportional to the speed deviation Δω between the master motor 4 and the slave motor 6 is performed, so that an original current command common to the two motors is obtained. while using the value I _o, the control mode of adding the compensation value based on both the speed difference Δω can be achieved easily and simply to a current command value I _CS slave motor 6. Furthermore, the gain G is preferably set to a value such that the speed deviation Δω approaches zero monotonously. Thus, by setting the gain G to such a value that the speed deviation Δω between the two approaches monotonically, the speed change between the two can be suppressed more efficiently.

In this embodiment, the first current command value generating unit 13, a position command value P _o and the speed command value to calculate the speed command value omega _O on the basis of the position deviation (time difference) [Delta] P between the master position P _M A calculation unit 17 and a current command value calculation unit 18 that calculates a first current command value I ₁ from a speed deviation (temporal deviation) Δω between the speed command value ω _o and the master speed ω _M are provided. More specifically, the speed command value calculation unit 17 is configured to generate a speed command value ω _o by performing PI compensation on the position deviation ΔP using the position loop gain K _PM . In addition, the current command value calculation unit 18 performs PI compensation on the speed deviation Δω using the speed loop gain K _ωM and outputs a first current command value I ₁ . The position loop gain K _PM and the velocity loop gain K _ωM include proportional gains (K _PP , K _ωP ) and integral gains (K _PI , K _ωI ), respectively, and the values of the differential gain and the integral gain are set individually. Is done.

In this way, by performing feedback control on the original current command value _Io based on the position P _M and the speed ω _M of the master motor 4, a common original current command value I to the master motor 4 and the slave motor 6 is obtained. Effective feedback control can be performed on _o .

Also, in order to perform position feedback control and velocity feedback control using a master speed omega _M obtained this with the master position P _M detected by the master position acquisition unit 9 is differentiated by a differentiator 10, a speed detector The two feedback controls can be easily realized without separately providing. Furthermore, since the current command value I _CS to the slave motor 6 is generated using the master speed acquisition unit 7 provided in advance in the configuration for performing such position feedback control and speed feedback control, the existing configuration can be easily used. The configuration of the present invention (that is, a control mode in which a compensation value based on the speed difference Δω is added to the current command value I _CS of the slave motor 6 while using the common current command value I _o common to the two motors). Can be realized.

In the present embodiment, since the reduction ratio of master power transmission mechanism 3 and the reduction ratio of slave power transmission mechanism 5 are the same value, current command value calculation unit 18 uses speed loop gain _KωM. A value obtained by multiplying the value after the PI compensation for the speed deviation Δω by a gain of 0.5 for distribution to each motor is output as the original current command value _Io . Therefore, in the present embodiment, the original current command value Io, the master current command value IM, and the slave current command value IS are substantially the same value.

Further, as a current command value that is input to the master motor drive unit 14, gravity may be added to the current correction value based on the consideration to dynamic torque applied to the master current command value I _M to the drive shaft 2 of the robot. Similarly, as a current command value input to the slave motor drive unit 15, a current correction value based on a dynamic torque considering gravity acting on the drive shaft 2 of the robot may be added to the compensated slave current command value _ICS. Good.

  The dynamic torque in consideration of gravity as a basis of these current correction values includes, for example, gravity torque, acceleration / deceleration torque, friction torque, torque (interference torque) that supports the movement of other shafts, and the like. The dynamic torque in consideration of gravity is defined as a value based on a theoretical value in robot operation and is set in advance. By performing feedforward control that adds a current correction value based on such dynamic torque, the positional deviation and speed deviation between the master motor 4 and the slave motor 6 can be reduced in advance, and more rapid control is performed. Can do.

<Modification>
FIG. 2 is a block diagram showing a schematic configuration of a robot control apparatus according to a modification of the first embodiment of the present invention. In the present modification, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The robot control device 1B of the present modification is different from the robot control device 1 in the first embodiment in that the reduction ratio α of the master power transmission mechanism 3B and the reduction ratio β of the slave power transmission mechanism 5B are different. It is. In response thereto, the control apparatus 1B is provided with a distribution element 19, 20 for applying each gain corresponding to the ratio of the reduction ratio in the first current command value I ₁ for driving the motors 4 and 6 . Furthermore, the control apparatus 1B, in order to calculate the velocity deviation Δω between the master velocity omega _M and a slave speed omega _S, and a speed adjustment element 21 for applying a gain to eliminate the effect of the reduction ratio.

  The distribution element 19 is provided between the original current command value generation unit 13 (current command value calculation unit 18) and the master motor drive unit 14. The distribution element 20 is between the original current command value generation unit 13 (current command value calculation unit 18) and the slave motor drive unit 15, and is upstream of the adder to which the compensation value GΔω output from the compensation element 16 is added. Is provided.

Ratio of the reduction ratio of the master power transmission mechanism 3B and slave power transmission mechanism 5B is alpha: for a beta, proportional gain distribution element 19 for distributing the original current command value I _o to the master motor 4, α / (α + β ), and the proportional gain of the distributing element 20 for distributing the original current command value I _o to the slave motor 6 is β / (α + β). Therefore, in this modification, the master current command value I _M is obtained by multiplying the original current command value I _o by the proportional gain α / (α + β) of the distribution element 19, and the slave current command value _IS is the original current command value I _S. The current command value _Io is multiplied by the proportional gain β / (α + β) of the distribution element 20.

Further, since the reduction ratio of the master power transmission mechanism 3B alpha and the reduction ratio β of the slave power transmission mechanism 5B is different, the master speed omega _M and a slave speed omega _S, the speed of the target is originally different. Therefore, in order to convert both speeds ω _M and ω _S into the same target speed and compare them, at least one of the outputs of the speed acquisition units 7 and 8 is multiplied by a gain for adjusting the speed. In this embodiment, the control apparatus 1B, in order to convert the master speed omega _M to the speed of the slave velocity omega _S, enter the master velocity omega _M to the speed adjustment element 21, the output and slave speed of the speed adjusting element 21 A difference from ω _S is calculated as a speed deviation Δω. That is, the speed adjustment element 21 is provided between the output terminal of the differentiator 10 and the input terminal of the subtractor that calculates the speed deviation Δω. In this case, the proportional gain of the speed adjustment element is β / α.

Incidentally, the speed adjustment element 21 for calculating the speed deviation Δω may be so as to convert the speed corresponding slave velocity omega _S to the target speed of the master speed omega _M, the master speed omega _M and a slave speed omega _S may be converted into a speed corresponding to another predetermined target speed (for example, a speed corresponding to the target speed of the drive shaft 2). In these cases, it is preferable to multiply the compensation element 16 by a gain for conversion into a speed corresponding to the original target speed of the slave motor 6 again.

  The present modification can also be applied when the reduction ratio α of the master power transmission mechanism 3B and the reduction ratio β of the slave power transmission mechanism 5B are the same (α = β). In this case, the proportional gains of the distribution elements 19 and 20 are both 0.5, and the proportional gain of the speed adjustment element is 1.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a schematic configuration of a robot control apparatus according to the second embodiment of the present invention. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 3, the robot control device 1C in the present embodiment is different from the robot control device 1 in the first embodiment in that there is one master motor 4 and a plurality of (two in the example of FIG. 3). ) Slave motors 6a and 6b. By providing a plurality of slave motors 6a and 6b, a plurality (two each) of configurations 5, 8, 11, 12, 15, and 16 related to the slave motors 6a and 6b are also provided. In FIG. 3, the difference between these components is distinguished by adding a or b to each symbol. Hereinafter, in some cases, the two slave motors 6a and 6b are referred to as a first slave motor 6a and a second slave motor 6b.

Also in this embodiment, like the first embodiment, the compensation obtained by multiplying a proportional gain G _a master speed omega _M and compensating element 16a to the speed deviation [Delta] [omega _a of the speed omega _Sa of the first slave motor 6a The compensated slave current command value I _{CSa obtained} by adding the value G _a Δω _a to the slave current command value I _Sa is input to the slave motor drive unit 15a for driving the first slave motor 6a. Further, a compensation value G _b Δω _b obtained by multiplying the speed deviation Δω _b between the master speed ω _M and the speed ω _Sb of the second slave motor 6 b by the proportional gain G _b of the compensation element 16 _b is added to the slave current command value I _Sb . The compensated slave current command value I _CSb is input to the slave motor drive unit 15b for driving the second slave motor 6b. Similarly, in case the number of the slave motor 6 is three or more, based on the speed deviation Δω of the master speed omega _M of the master motor 4 and slave speed omega _S of the slave motor 6 current command value to the slave motor 6 Can be compensated.

In the present embodiment, when the reduction ratio of master power transmission mechanism 3 and slave power transmission mechanisms 5a and 5b is the same, current command value calculation unit 18 uses PI speed loop gain _KωM to _perform PI compensation for speed deviation Δω. A value obtained by multiplying the original current command value _Io after 1/3 by a gain of 1/3 is output as a master current command value _IM and slave current command values _ISa , _ISb . Thus, the common original current command value _Io is evenly distributed to the master motor 4 and the slave motors 6a and 6b.

  Also in the present embodiment, as in the modification of the first embodiment, when the ratio of the reduction ratio of the master power transmission mechanism 3 and the reduction ratio of the slave power transmission mechanism 5a is different, and / or the master power When the ratio of the reduction ratio of the transmission mechanism 3 and the reduction ratio of the slave power transmission mechanism 5b is different, each element is provided at a location corresponding to the distribution elements 19 and 20 and the speed adjustment element 21 of the first embodiment. Thus, the configuration of the present embodiment can be realized.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention.

  For example, a part of the configuration described in the first embodiment and the modifications thereof can be applied in the second embodiment.

  Further, the master speed acquisition unit 7 and the slave speed acquisition unit 8 of the above embodiment are configured to detect the positions of the master motor 4 and the slave motor 6 and convert them into speeds. It is good also as acquiring the speed of the master motor 4 and the slave motor 6 directly using a detector.

<Example>
Below, the result of having simulated the torque difference between the master motor 4 and the slave motor 6, the speed difference, and the electric current command value difference based on the structure of the said 1st Embodiment is shown. No added output GΔω the compensating element 16 as a current command value for the slave motor 6 as a comparative example (entering a slave current instruction value I _S directly to the slave motor drive unit 15) the torque between the master motor 4 and the slave motor 6 in aspects Differences, speed differences and current command value differences were also simulated.

  FIG. 4 is a graph showing temporal changes in torque and speed of the master motor and slave motor in this embodiment. The upper graph in FIG. 4 is a graph showing a temporal change in torque, and the lower graph is a graph showing a temporal change in speed. In both graphs, the master motor and the slave motor are overlapped. FIG. 5 is an enlarged view of a portion V in the graph showing the temporal change of the speed shown in FIG. FIG. 7 is a graph showing temporal changes in torque and speed of the master motor and slave motor in the comparative example. FIG. 8 is an enlarged view of a part VIII in the graph showing the temporal change of the speed shown in FIG. 7 corresponds to FIG. 4 in the embodiment, and FIG. 8 is a graph corresponding to FIG. 5 in the embodiment. In the enlarged views of FIGS. 5 and 8, only the schematic waveform is traced so that the speed waveform of the master motor and the speed waveform of the slave motor can be easily understood.

  First, the graphs (upper graphs) showing temporal changes in torque in FIG. 4 and FIG. 7 are compared. In the comparative example (FIG. 7) in which compensation based on the speed deviation Δω is not performed, a vibration phenomenon such as noise appears greatly particularly in the Ac portion where the direction of the generated torque changes. This is because when the torque fluctuation is large, the other motor (slave motor) is not following the one motor (master motor) well, and the torque value of the other motor is compared to the torque value of one motor. This is thought to be due to the above or below.

  In contrast, in the present embodiment (FIG. 4) in which compensation based on the speed deviation Δω is performed, the vibration phenomenon such as noise is relatively suppressed even in the Ae portion where the direction of the generated torque changes, and the overall smoothness is achieved. It has a simple waveform. Therefore, in this embodiment, there is relatively no difference in the torque values generated by the master motor 4 and the slave motor 6, and the torque fluctuation of the slave motor 6 follows the torque fluctuation of the master motor 4 well. It is thought that.

  Next, the graph (lower graph) which shows the time change of each speed of FIG. 4 and FIG. 7 is compared. In the comparative example (FIG. 7), the master motor speed changes relatively smoothly as shown in FIG. 8, particularly in the region where the speed changes continuously (for example, the VIII section), whereas the slave motor This speed did not follow the master motor speed well, resulting in the slave motor speed approaching or leaving the master motor speed.

  On the other hand, in the present embodiment (FIG. 4), as shown in FIG. 5, both the speed of the master motor 4 and the speed of the slave motor 6 change relatively smoothly in the same region (V section). was gotten. Thus, according to the present embodiment, it was shown that the speed of the master motor 4 and the speed of the slave motor 6 were able to follow well without leaving.

FIG. 6 is a graph showing a temporal change of the compensated slave current command value _ICS together with the comparative example in the present embodiment. As shown in FIG. 6, in the comparative example in which compensation based on the speed deviation Δω is not performed, the vibration width of the current command value is relatively large, whereas in this embodiment, the vibrational change in the current command value _ICS is compared. The results were smooth and varied. Thus, according to the present embodiment, it was shown that the vibration change of the current command value _ICS itself to the slave motor 6 is suppressed, and relatively smooth torque fluctuation control is performed.

  The robot control apparatus and the robot control method of the present invention are useful for reducing the positional deviation between motors in a servo control structure in which one drive shaft is driven by at least two motors.

1, 1B Robot control device 2 Drive shaft 3 Master power transmission mechanism 4 Master motor 5 Slave power transmission mechanism 6 Slave motor 7 Master speed acquisition unit 8 Slave speed acquisition unit 9 Master position acquisition units 10 and 12 Differentiator 11 Slave position acquisition Unit 13 Original current command value generation unit 16 Compensation element 17 Speed command value calculation unit 18 Current command value calculation unit

Claims (5)

A robot control apparatus comprising: a drive shaft that drives a movable part that defines the operation of the robot; a master motor that rotationally drives the drive shaft; and one or more slave motors that rotationally drive the drive shaft. ,
A master position acquisition unit for acquiring a master position which is a rotational position of the master motor;
An original current command value generating unit that generates an original current command value based on a position command value and the master position;
A master speed acquisition unit that acquires a master speed that is the speed of the master motor;
A slave speed acquisition unit for acquiring one or more slave speeds, each of which is a speed of the one or more slave motors;
One or more compensation elements for compensating the slave speed corresponding to each deviation based on one or more deviations of the slave speed with respect to the master speed,
The master current command value and one or more slave current command values are generated by distributing the original current command value, the master motor is driven based on the master current command value, and each corresponds to the one or more slave motors. A controller for a robot that controls to drive one or more slave motors based on current command values obtained by adding outputs of the corresponding compensation elements to the one or more slave current command values.   The robot control apparatus according to claim 1, wherein the compensation element includes a proportional element.   The robot control apparatus according to claim 2, wherein the proportional gain of the proportional element is set to a value such that a deviation between the master speed and the slave speed monotonously approaches zero. The master speed acquisition unit includes the master position acquisition unit, and a differentiator that differentiates the master position acquired by the master position acquisition unit and outputs the master speed,
The slave speed acquisition unit includes a slave position acquisition unit that acquires a slave position that is a rotational position of the slave motor, and a differentiator that differentiates the slave position and outputs the slave speed. 4. The robot control device according to any one of items 1 to 3. A robot control method comprising: a drive shaft that drives a movable part that defines the operation of the robot; a master motor that rotationally drives the drive shaft; and one or more slave motors that rotationally drive the drive shaft. ,
Obtaining a master position which is the rotational position of the master motor;
An original current command value is generated based on the position command value and the master position,
Obtaining a master speed which is the speed of the master motor;
Obtain one or more slave speeds, each of which is the speed of one or more of the slave motors;
Calculating a compensation value for compensating the slave speed corresponding to each deviation based on one or more deviations of the slave speed with respect to the master speed;
The master current command value and one or more slave current command values are generated by distributing the original current command value, the master motor is driven based on the master current command value, and each corresponds to the one or more slave motors. A robot control method for driving one or more slave motors based on current command values obtained by adding the corresponding compensation values to the one or more slave current command values.

Images