JP2002082721A - Driving controller for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot driving controller which suppresses abrupt variation of current, when an actuator is started or stopped, by performing current control based upon an ideal current for placing a movable position of a robot in desired operation as a control target, and which can be manufactured at low cost. SOLUTION: The robot driving controller 1 comprises a potentiometer 2 which detects position information on a movable part, a current sensor 3 which detects the actual current flowing to a stepping motor 7, an ideal current determination part 4 which determines the ideal current for making the movable part to operate as desired, a hold torque determination part 5 which determines hold torque needed to make the movable part stationary, and a motor current control part 6 which corrects the actual current according to the hold torque and ideal current and determines a motor command value for making the movable part move to an operation target position as desired.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control device for a robot for operating a movable part of the robot.

[0002]

2. Description of the Related Art Conventionally, a robot having a movable part among industrial robots and toy robots, etc., detects the operating state of the movable part one by one in control for operating the movable part, and the detection result is a target. The feedback control for appropriately changing the voltage applied to the actuator so as to match the operation has been used. In particular, in the case of a robot that imitates a creature such as a pet-type robot or a human-type robot, for example, when the control target is a human-type robot, the control becomes complicated in order to move the movable part like a human, so high performance is required. Feedback control was required.

[0003] However, a device that performs high-performance feedback control is very expensive, and is unsuitable for a robot that needs to be manufactured at low cost, such as a toy robot. . Therefore, as another control method, an ideal voltage of the actuator is set such that the movable part performs a desired operation, and a voltage control for correcting an actual voltage with the value as a control target is performed to perform a desired operation on the movable part. There is something to make. With this control method, unlike the above-described high-performance feedback control, there is feed-forward control that detects the current position of the movable part and uniquely determines an ideal voltage value corresponding to the operation target position and the current position. Therefore, it can be realized at low cost.

[0004]

However, in the above-described voltage control, a sudden current change occurs particularly at the start and stop of the operation of the actuator, and at the start, the movable part performs a sudden operation for a moment. There is a problem to be solved such that a steep vibration occurs at the time of stop.

Therefore, the present invention has been made in view of such an unsolved problem of the conventional technology, and performs current control using an ideal current for causing a movable part to perform a desired operation as a control target. Accordingly, it is possible to provide a drive control device for a robot which can suppress a sudden change in current at the time of starting and stopping of an actuator, perform a desired operation on a movable part, and can be manufactured at low cost. The purpose is.

[0006]

According to a first aspect of the present invention, there is provided a drive control device for a robot for operating a movable portion of a robot, wherein A movable part current position detecting means for detecting a current position of the movable part, an actuator current detecting means for detecting an actual current flowing in an actuator for operating the movable part, and Ideal current determining means for determining an ideal value of the current for operating the movable part as desired based on the current value; and actuator current control means for adjusting the driving torque of the actuator by correcting the actual current based on the ideal value. And with.

With such a configuration, a function, a database, and the like for obtaining an ideal value of a current corresponding to the current position and the operation target position of the movable part are set so that the movable part operates as desired for each type of robot. When the movable part is operated, first, when the operation target position is input, the movable part current position detecting means detects the current position of the movable part. Next, the ideal current determining means determines an ideal value of the corresponding current from a preset database or function based on the detected current position and the input operation target position, and the actuator current control means Then, the actual current detected by the actuator current detecting means is corrected so as to approach the ideal value. As described above, by repeatedly performing the detection of the current position, the determination of the ideal value, and the correction of the actual current at predetermined intervals, the drive torque of the actuator is controlled to an appropriate magnitude, and the movable portion is operated as desired. It is possible to operate up to the position. At this time, the information fed back is only the current position of the movable part and the actual current flowing through the actuator, and the ideal value is determined by feedforward control that uniquely determines the input target position and the detected current position. Therefore, high-performance feedback control is not required, and realization can be achieved with an inexpensive configuration.

According to a second aspect of the present invention, in the drive control device for a robot according to the first aspect, the ideal current determining means is provided when the difference between the operation target position and the current position is large. The ideal value is determined in such a manner that the driving torque tends to be larger than when the driving torque is small. In other words, the magnitude of the ideal value is determined by the difference between the current position and the operation target position. For example, when the difference is large, the ideal value is increased, and as the difference is reduced, the ideal value is gradually reduced. Is set as follows. For example, if the actuator is a motor, increasing the current flowing through the motor when the distance between the current position of the movable part and the operation target position is long, generates a large torque on the rotating shaft to increase the rotation speed of the motor. When the distance from the target position is short, the torque of the rotating shaft is reduced by reducing the current flowing through the motor to reduce the rotation speed of the motor. By setting the ideal value in this way, it is possible for a robot that imitates a living thing, such as a humanoid robot or a pet-shaped robot, to make the operating speed of the arm, which is a movable part, more or less slow, and to make the movement more like a living thing Can be realized. The ideal value for the distance between the current position of the movable part and the movement target position is set according to the distance by a straight line or a curve, or is set so as to change in a stepwise manner. Set

According to a third aspect of the present invention, in the drive control device for a robot according to the first aspect, a holding torque determination for determining a torque for holding the movable portion in a stationary state based on the current position. Means, wherein the actuator current control means corrects the actual current so as to generate a torque obtained by adding the driving torque corresponding to the ideal value and the holding torque.

In other words, the current of the actuator for operating the movable part is controlled in consideration of the holding torque required for stopping the movable part at a predetermined position. The holding torque determining means determines the holding torque at that position (strictly, a current for generating the holding torque) from the detected information of the current position, and the actuator current controlling means determines the holding torque current and the ideal value. Is corrected as the control target value. By controlling the current in this way, when the weight of the movable part is large, it is possible to control the change in the operating speed when operating in the direction against gravity and when operating in the direction following gravity by the ideal value. It becomes possible. Accordingly, when this robot drive control device is applied to, for example, a humanoid robot, an operation is performed in which the arm of the robot is moved in a direction against gravity (the arm is lifted) and then returned to the original position in accordance with the gravity, that is, the original position. When the arm is lowered, the holding torque is determined from the detected current position, and the ideal value is added to the current for the holding torque, so that the weight of the arm is canceled by the holding torque, The operation is left only to the ideal value. For example, by controlling with the same ideal value, it is possible to raise or lower the arm with the same speed change according to the ideal value, and the speed at the time of ascent and descent without considering the weight of the movable part Makes it possible to perform a human-like operation as compared with an unnatural operation due to the mismatch between the two. It should be noted that the ideal value should be set in advance according to the conditions of the control target such that the numerical value is negative when the movable part is operated in the direction following gravity, and positive when the movable part is operated in the direction against gravity. There is.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are views showing an embodiment of a drive control device for a robot according to the present invention.
First, the configuration of a drive control device for a robot according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a drive control device for a robot according to the present invention. FIG. 2 is provided on a movable part (left arm) of a humanoid robot equipped with such a drive control device for a robot. FIG. 3 is a diagram illustrating positions of a stepping motor, a potentiometer, and a current sensor.

The robot drive control device 1 comprises a potentiometer 2 for detecting position information of a movable part, a current sensor 3 for detecting an actual current flowing through a stepping motor 7,
An ideal current determining unit 4 for determining an ideal current for operating the movable part as desired, a holding torque determining unit 5 for determining a holding torque necessary for stopping the movable part, and based on the holding torque and the ideal current. And a motor current controller 6 for determining a motor command value for correcting the actual current to move the movable part to the operation target position as desired.

The stepping motor 7 is composed of first and second stepping motors 7a and 7b at different positions, and as shown in FIG.
Are arranged so as to operate in two axial directions of the front-rear direction and the lateral direction. The potentiometer 2 includes first and second potentiometers 2a and 2b, each of which is installed so that the resistance value changes in conjunction with the first and second stepping motors 7a and 7b. Operates to change the position of the movable part, and converts the resistance value corresponding to the position of the movable part into a voltage value and outputs it as position information. This position information is transmitted to the ideal current determining unit 4 and the holding torque determining unit 5, respectively.

The current sensor 3 comprises first and second current sensors 3a and 3b, and a stepping motor 7a,
7b is connected to each motor to detect the actual current flowing through the motor 7b. The detected current value is transmitted to the motor current control unit 6. The ideal current determination unit 4 determines an ideal value of a current for operating the movable part as desired based on the detected position information and the input operation target position in accordance with a preset ideal value determination method. . Here, the method of determining the ideal value is a function of determining the ideal value from the detected current position and the input operation target position, or the determination of the ideal value itself, such as a database of ideal values corresponding one-to-one to the position information. In addition to the method, a method of setting the sign of an ideal value, such as making the direction opposite to gravity plus the moving direction of the movable part and making the direction following gravity negative, is also shown. Here, the rotation direction of the motor is also determined from the relationship between the current position and the operation target position. The determined ideal value and the rotation direction of the motor are transmitted to the motor current control unit 6.

The holding torque determining unit 5 determines the holding torque based on the detected position information by using a function or a database in the same manner as the ideal current determining unit 4. The determined holding torque is determined by the motor current control unit 6. Transmitted to.
The motor current control unit 6 determines the final target current value by adding the ideal value to the current value for the holding torque, determines the command value to the motor so that the actual current becomes the target value, and performs stepping. The command value is transmitted to the motor 7. The command value includes information on the rotation direction of the motor. Then, the stepping motor 7 is driven according to the input command value.

The head, right arm, left leg, and right leg, which are movable parts other than the left arm 9 of the robot 8, operate in the same manner as the left arm 9, but details are not shown here. The drive control device 1 for a robot includes a RAM for storing each detection result and a calculation result, and a ROM for storing a program for controlling the ideal current determination unit 4, the holding torque determination unit 5, and the motor current control unit 6. And a central processing unit (CPU) for executing the program.

FIG. 3 is a flowchart showing an operation process of the robot drive control device 1 according to the present invention. Less than,
The flow will be described based on FIG. As shown in FIG.
First, the operation target position of the movable part is input to the ideal current determination unit 4, and the process proceeds to step S302. Step S302
At this point, since the ideal current and the actual current have not been input to the motor current controller 6, the process proceeds to step S304 without performing any processing.

In step S304, since the motor command value has not been input to the stepping motor 7, the process proceeds to step S306 with the motor kept as it is. In step S306, the current position of the movable part is detected by the potentiometer 2, and the actual current flowing through the stepping motor 7 is detected by the current sensor 3. Then, the current position is transmitted to the ideal current determination unit 4 and the holding torque determination unit 5, respectively, and the actual current is transmitted to the motor current control unit 6, and the process proceeds to step S308.

In step S308, the ideal current deciding unit 4 decides an ideal value of a current for moving the movable part to the operation target position as desired according to a preset deciding method. Further, the rotation direction of the motor is determined from the current position and the operation target position, the determined ideal value and the rotation direction of the motor are transmitted to the motor current control unit 6, and the process proceeds to step S310. The sign of the ideal value is determined in accordance with a preset signing method based on conditions of the movable part to be operated.

At step S310, based on the input current position information, the holding torque is determined by a function or a database in the same manner as the determination of the ideal value, and the determined holding torque is transmitted to the motor current control unit 6. Move to step S302. Moving to step S302,
This time, since the ideal value and the holding torque have been determined and input to the motor current control unit 6, the target value is determined by adding the ideal value and the current value for the holding torque. Then, the detected actual current is set to this target current value, and a motor command value is determined so as to operate in the determined rotation direction of the motor and transmitted to the stepping motor 7, and the process proceeds to step S304. .

In step S304, the stepping motor 7 is driven in accordance with the motor command value to move the movable part in the direction of the operation target position, and the flow advances to step S306.
In step S306, the position information of the movable part is detected again, and the actual current flowing through the stepping motor 7 is detected, and the position information is used as the ideal current determination unit 4 and the holding torque determination unit 5.
, And the detected current is transmitted to the motor current controller 6, and the process proceeds to step S308.

That is, when the operation target position of the movable part is input in step S300, the processing of steps S302 to S310 is repeated to move the movable part to the operation target position. The function or database is set so that the ideal value of the current becomes 0 for the movable part that has reached the operation target position. As a result, at the operation target position, the motor is driven only by the holding torque at that position. To be stationary.

Next, the actual operation of the drive control device 1 for a robot according to the present invention will be described with reference to FIGS.
FIG. 4 is a diagram showing an operation of the left arm 9 of the robot 8 only in the lateral direction. FIG. 5 shows a function for determining an ideal current value.
FIG. 6 is a graph plotting the difference between the current position and the operation target position and the magnitude of the torque as axes, and FIG. 6 is a graph illustrating the relationship between the position information and the holding torque. Note that when the left arm 9 is operated in the “RU” direction shown in FIG. 4, the rotation direction of the motor is “left rotation”, the “RD” direction is “right rotation”, and the motor is operated in a direction against gravity. The sign of the ideal value of the current is plus, and the sign of the direction according to gravity is minus.

When the left arm 9 is at the position A in FIG. 4, the operation target position is the position C in FIG.
(Step S300), the processing in steps S302 to S304 is skipped without performing anything because the information is only the operation target position at this point. Then, when the process proceeds to step S306,
The current position of the left arm 9 is detected by the second potentiometer 2b. In this case, an angle “0 °” corresponding to the position A in FIG. 4 is detected. Further, the actual current flowing in the stepping motor 7b is detected by the current sensor 3b, but no specific numerical value is shown here. Then, the detected current position is transmitted to the ideal current determination unit 4 and the holding torque determination unit 5, respectively, and the actual current is transmitted to the motor current control unit 6.

In step S308, the ideal current determining unit 4 determines the ideal value of the current for driving the stepping motor 7b based on the input current position and target operation position. In the present embodiment, when determining the ideal value of the current, the ideal value of the current tends to be larger when the difference is larger than when the difference is smaller than the distance between the current position and the operation target position. Set the function. The graph shown in FIG. 5 shows the function with the difference and the ideal value of the current as axes, but is a straight line having a certain slope. The ideal value of the current for moving the left arm 9 to the operation target position with respect to the current position is calculated from the function of this straight line. Note that the degree of change in current can be changed by setting an arbitrary value for the slope of the straight line. Therefore, the slope is appropriately changed according to the type of robot, the operation content, and the like. For the sake of explanation, for example, when the inclination is set to “1” (different from FIG. 5), the function is as follows.

I = 1 * D (1) That is, the difference between the current position and the operation target position is D,
The product of multiplying the difference D by the slope “1” of the straight line is the ideal value I of the current.
[MA]. Here, since the current position is “0 °” and the operation target position is the position C, the position information is “90”.
°, and the ideal value I of the current is the product “90” obtained by multiplying “1” by the difference D “90 ° −0 ° = 90 °”.
[MA] ". The calculated ideal value is transmitted to the motor current control unit 6.

The ideal current control section 4 determines the rotation direction of the motor in order to move the left arm section 9 to the operation target position. In this case, the left arm 9 is set to “R” shown in FIG.
Since the operation is performed in the “U” direction, the rotation direction is “left rotation”. Further, the sign of the calculated ideal value is “plus” because the operation is in the direction against gravity. Step S31
When the state is shifted to 0, the holding torque determining unit 5 determines from the holding torque database that stores the holding torque in the relationship of the graph of FIG. 6 with respect to the input current position information, the holding torque “0” corresponding to the position information. Is determined.

Then, the process returns to step S302, and the motor current control unit 6 adds the input ideal value and the current value for generating the holding torque. The added current value becomes the final target current, and the actual current detected by the current sensor 3b is corrected so as to become the target current, and the stepping motor 7b is rotated in the determined rotation direction "left rotation". A motor command value is determined so as to drive the stepping motor 7b.
Transmit to.

In step S304, since a motor command value is input to the stepping motor 7b, the motor is driven in accordance with the command value, and the left arm 9 is operated in the direction of the operation target position. In step S306, the position information of the left arm 9 in operation is detected again, and the actual current flowing through the stepping motor 7b at that time is detected. The current is transmitted to the motor 5 and the actual current is transmitted to the motor current controller 6. Here, if the detected current position information of the left arm 9 is the position B shown in FIG. 4, the current position is “45 °”.

In step S308, the product of "45", which is the difference between the detected current position "45" and the operation target position "90", is multiplied by "1" according to the above equation (1). “45 [mA]” is calculated as the ideal value I of the current. In addition, since the left arm 9 is moved in a direction against gravity, the sign of the ideal value is set to plus, and the rotation direction of the motor is also operated in the “RU” direction. Is transmitted.

In step S310, the current position information "4
From 5 °, the holding torque “20” is determined from FIG. 6 in the same manner as described above. Then, the process proceeds to step S302 to determine a motor command value, and the motor is driven according to the command value in step S304. When the left arm 9 moves to the operation target position “C position”, the current position becomes the C position “90 °”, the difference from the target position becomes “0 °”, and the ideal value of the current is From the above equation (1), it is “0 [mA]”. Therefore, the motor current control unit 6 determines the motor command value so as to drive the motor with the current that generates the holding torque “40” at the C position, and the left arm unit 9 uses the holding torque “40” at the target position. It stops at a certain C position.

If the position A is input as the operation target position when the left arm 9 is stationary at the position C (step S300), the processing of steps S302 to S304 is skipped. S3
At 06, the current position “90 °” is detected. In this case, the difference from the A position “0 °” is “90 °”, and in step S308, the ideal value of the current is “90 [mA]” from the equation (1), and the rotation direction of the motor is A
Contrary to the operation from the position to the C position, this time, “R” shown in FIG.
Since the operation is in the “D” direction, the operation is performed in the “right-turn” direction, and the operation follows the direction of gravity.

In step S310, the holding torque "40" at the C position is determined, and when the process returns to step S302, an ideal value is added to the holding torque "40" (in this case, the sign of the ideal value is minus. Subtraction because there is)
The target current value is calculated, the actual current is corrected to become the target current value, and the stepping motor 7b
Output a motor command value to drive the motor.

That is, when the left arm 9 is operated from the position C to the position A, the current obtained by subtracting the ideal value of the current from the current for the holding torque is opposite to the operation from the position A to the position C described above. This is the final current target value. Then, similarly to the above-described operation from the position A to the position C, step S30 is performed.
2 to S310 are repeatedly performed at a predetermined cycle, whereby the left arm 9 is moved to the target position A, which is the operation target position, and is stopped at that position.

The operation of the robot drive control device 1 according to the present invention has been described above. The operation of the left arm 9 at the position A to the position C or the position C to the position A is described in step S
Since the processing from step 302 to step S310 is extremely faster than the operation speed of the left arm 9, the processing is actually repeated many times before the left arm 9 reaches the operation target position. That is, “0 to 1” in which the left arm 9 can operate.
When the ideal value and the holding torque of the current are set at 5 ° intervals in the range of “80 °”, the predetermined cycle is set to all the ideal values and the holding torque set from the start position to the operation target position. Steps S302 to S3
The left arm 9 is operated by updating the motor command value to an appropriate value with respect to a change in the position of the left arm 9 in increments of 5 ° by setting the period to be a period sufficient to perform the processing of Step 10. Operate to the target position.

As described above, the drive control device 1 for a robot according to the present invention determines the target current value by adding the ideal value and the current for the holding torque in order to operate the movable part as desired. Since the drive current is adjusted by controlling the current flowing through the motor so as to reach the target current value, the motor flowing directly through the motor is directly controlled so that the motor starts and stops at the time of voltage control. And the ideal value is added to the holding torque, so that even if the weight of the movable part is large, the target current is calculated based on the holding torque that bears the weight. Since the value is determined, the operation of the movable part can be controlled by the ideal value.

Further, since the ideal value is determined by a function that changes when the difference between the start position and the operation target position is large is larger than when the difference is small, the left arm of the robot 8 It is possible to cause the unit 9 to perform an operation with a speed like a creature. Since the control is performed only by a simple linear function calculation or addition / subtraction, a high-performance CPU is not required, and the cost can be reduced.

Here, the potentiometer 2 is defined in claim 1
And current sensor 3 corresponding to the current position detecting means described in
Corresponds to the actuator current detecting means of the first to third aspects, the ideal current determining section 4 corresponds to the ideal current determining means of the first to third aspects, and the motor current control section 6 corresponds to the first aspect. 3 corresponds to the actuator current control means, and the holding torque determination unit 5 corresponds to the holding torque determination means according to claim 3.

In the above-described embodiment, the processing is repeated until the left arm 9 stops at the operation target position. However, even after stopping at the operation target position, steps S302 to S3 are performed.
When the position information of the movable part changes due to, for example, tilting of the body of the robot, the processing of step 10 is repeated to correct the holding torque before the change to the holding torque at the position after the change, thereby changing the posture of the robot. You may make it control so that it may not collapse.

In the above embodiment, when determining the ideal value, the ideal value of the current tends to be larger when the difference between the operation start position and the operation target position is large than when the difference is large. Although the function is set and used, the present invention is not limited to this, and a function that makes a desired change regardless of the distance, a database that makes a desired change without being limited to the function, and the like may be set and used.

In the above-described embodiment, a linear function that changes linearly is used to determine the ideal value of the current. However, the present invention is not limited to this. Alternatively, a function that changes the ideal value linearly or stepwise, or a database or the like may be set and used. In the above embodiment, the stepping motor is used as the actuator of the movable part.
Any other motor such as a motor, or any other motor, such as a solenoid or an electromagnetic brake, may be used as long as it does not deviate from the gist of the present invention.

[0042]

As described above, according to the drive control device for a robot according to the first aspect of the present invention, the operation of the movable part is performed by directly controlling the actual current flowing through the actuator. It is possible to suppress a sudden change in current at the time of starting and stopping the operation of the movable part, which occurs when voltage control is performed. In addition, since the determination of the current target value is determined by a simple calculation, a high-performance CPU is not required, and the cost of the CPU can be reduced.

According to the drive control device for a robot according to the second aspect of the present invention, in addition to the effect of the first aspect, the ideal value of the current is calculated as the difference between the operation start position and the operation target position. On the other hand, when the difference is larger, the ideal value is determined to change with a tendency to be larger than when the difference is smaller, so that the movable part of the robot can be operated like a living thing.

According to the drive control device for a robot according to the third aspect of the present invention, in addition to the effect of the first or second aspect, the control target value of the electric current is required for stopping the movable part. Since the determination is made by adding the ideal value of the current to the current for the holding torque, even if the movable part has a large weight, the effect of the holding torque for the operation due to the weight is negated. The operation change can be determined only by the ideal value of the current.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a drive control device for a robot.

FIG. 2 is a diagram showing an arrangement of a stepping motor, a potentiometer, and a current sensor provided on a movable part (left arm) of a humanoid robot equipped with a drive control device for a robot.

FIG. 3 is a flowchart showing an operation process of the robot drive control device 1;

FIG. 4 is a diagram showing an operation of the left arm 9 of the robot 8 only in a lateral direction.

FIG. 5 is a graph showing a relationship between position information and an ideal current value.

FIG. 6 is a graph showing a relationship between holding torque and position information.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Drive control device for robot 2 Potentiometer 3 Current sensor 4 Ideal current determination unit 5 Holding torque determination unit 6 Motor current control unit 7 Stepping motor 8 Robot 9 Left arm unit 10 Body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02P 8/30 H02P 8/00 302A F-term (Reference) 2C150 CA01 CA02 DA04 DA05 DA24 DA26 DA27 DA28 EB01 EF03 EF11 EF16 EF23 3F059 AA00 BA00 BB06 DA08 DC00 FB29 FC03 FC11 5H269 AB33 BB01 CC09 EE13 GG06 5H303 AA10 BB15 CC08 DD03 FF03 JJ09 KK02 KK22 KK24 KK29 KK33 MM05 5H580 AA03 BB02 FA02 FA04 FD14GG

Claims (3)

[Claims] 1. A drive control device for a robot for operating a movable part of a robot, wherein the actual part flows to a movable part current position detecting means for detecting a current position of the movable part and an actuator for operating the movable part. Actuator current detecting means for detecting a current, ideal current determining means for determining an ideal value of the current for operating the movable part based on the current position and the operation target position of the movable part, and based on the ideal value An actuator current control means for adjusting the drive torque of the actuator by correcting the actual current. 2. The ideal current determining means determines the ideal value in such a manner that the drive torque tends to be larger when the difference between the operation target position and the current position is large than when the difference is small. The drive control device for a robot according to claim 1, wherein 3. A control device according to claim 2, further comprising: a holding torque determining unit configured to determine a torque for holding the movable part in a stationary state based on the current position.
2. The drive control device for a robot according to claim 1, wherein the actual current is corrected so as to generate a torque obtained by adding a drive torque corresponding to the ideal value and the holding torque. 3.