CN113541570A

CN113541570A - Motor control device

Info

Publication number: CN113541570A
Application number: CN202110387292.9A
Authority: CN
Inventors: 井出勇治; 北原通生; 平出敏雄
Original assignee: Sanyo Denki Co Ltd
Current assignee: Sanyo Denki Co Ltd
Priority date: 2020-04-20
Filing date: 2021-04-09
Publication date: 2021-10-22
Also published as: TW202147767A; PH12021050166A1; JP7532074B2; JP2021175206A

Abstract

The present invention provides a motor control device, including: a speed detection unit for detecting the speed of the motor; a position controller for calculating a first speed command based on the position deviation; a speed limiting unit that obtains a third speed command after limitation by limiting a second speed command based on the torque command; and a speed command selection unit that selects either one of the first speed command and the third speed command in response to the control mode automatic switching signal, wherein the motor control device obtains the motor speed command from the selected value.

Description

Motor control device

Technical Field

The present invention relates to a motor control device.

Background

In welding a workpiece using a servo welding gun (electric welding gun) for spot welding, the workpiece is held by a welding head of an electrode portion of the electric welding gun. Then, the torque of the motor is controlled to pressurize the workpiece and the bonding heads are energized. Thus, the workpiece is welded. Such an electric welding gun is moved to the front of the contact with the pressurized object by position control or speed control. Subsequently, the control mode is switched to the torque control mode, and the welding torch pressurizes the pressurizing object. In addition, a torque control mode having a speed limiting function is implemented in order to prevent the electric welding gun from colliding with the pressurized object due to an excessive speed of the electric welding gun when the control mode is switched to the torque control mode. After welding, the control mode is switched to the position control mode or the speed control mode again, and the electric welding gun is moved.

Japanese patent No. 6113378 discloses an example of performing the pressing control while switching the control mode between the position control mode, the speed control mode, and the torque control mode. The motor control device described in japanese patent No. 6113378 controls a motor provided with an encoder. The motor control device includes a position command generation unit, a position control unit, a pressure command generation unit, a pressure control unit, a speed command selection unit, and a speed control unit. A position command generating unit generates a position command. The position command is a command value for bringing a mechanical load driven by the motor close to the object to be pressurized and for bringing the final position of the mechanical load to a position just before the object to be pressurized by a predetermined distance. The position control unit outputs a first speed command to cause the position of the motor detected by the encoder to follow the position command. The pressure command generation unit generates a pressure command that is a command value of pressure or force to be applied to the pressurized object. The pressure control unit outputs a second speed command so that the pressure or force detected by the mechanical load follows the pressure command when the mechanical load presses the pressurized object. The speed command selection unit selects any one of a creep speed, a first speed command, and a second speed command and outputs the selected one as a speed command for operating the motor. The creep speed defines an upper limit of the speed of the motor when the mechanical load contacts the pressurized object. The speed control unit outputs a current command for supplying a current to the motor so that the speed of the motor follows the speed command output from the speed command selection unit. The speed command selection unit selects a smaller value of either the second speed command or the creep speed at a timing when the first speed command is selected and the first speed command is lower than the creep speed.

In this way, according to the method of japanese patent No. 6113378, after the timing at which the first speed command is lower than the creep speed, the process of selecting a smaller value of either the second speed command or the creep speed is performed. However, in this method, a pressure detector or a force detector is required to constitute the pressure control unit. Therefore, according to this method, it is difficult to perform press control in an apparatus in which it is difficult to provide such a detector. Further, an unstable factor may be generated due to noise included in an output from the pressure detector or the force detector or mechanical rigidity of the pressure control circuit. At this time, the speed command from the pressure control unit fluctuates. Therefore, the pressure control circuit is shut off and restored in the vicinity of the timing of switching the creep speed and the second speed command. Therefore, the operation of the pressure control circuit becomes unstable.

Disclosure of Invention

An object in the present disclosure is to provide a motor control device for press control as follows. The motor control device can perform a transition from position control or speed control to torque control with a speed limiting function at a high speed without requiring a pressure detector or a force detector, and can perform a transition from a speed limiting state to torque control at a high speed and stably.

A motor control device (present motor control device) according to an aspect of the present disclosure includes: a speed detection unit that detects a speed of the motor; a first subtractor that obtains a position deviation by subtracting the position from the position command; a position controller for calculating a first speed command based on the position deviation; a speed deviation calculator that obtains a first speed deviation based on the torque command; an adder that obtains a second speed command based on the torque command by adding a first speed deviation based on the torque command to the speed; a speed limiting unit that limits a second speed command based on the torque command in accordance with a speed limiting command, obtains a third speed command after the limitation, and outputs the third speed command after the limitation; a speed command selecting unit that selects either one of the first speed command from the position controller and the restricted third speed command, based on a control mode automatic switching signal; a second subtractor that obtains a second speed deviation by subtracting the speed of the motor from a motor speed command and outputs the second speed deviation; a speed controller that calculates a motor torque command by performing a speed control calculation using the second speed deviation as an input, and outputs the motor torque command; and a motor torque control unit that causes the motor to output a torque based on the motor torque command, wherein the speed controller includes a proportional controller and an integral controller, the speed command selection unit compares the first speed command from the position controller with the limited third speed command, selects the value of the first speed command from the position controller when the value of the first speed command from the position controller is larger than the value of the limited third speed command, selects the value of the limited third speed command when the value of the first speed command from the position controller is equal to or smaller than the value of the limited third speed command, and obtains the motor speed command from the selected value.

Preferably, the speed command selection unit enables automatic switching of the control mode when the position of the member driven by the motor reaches a predetermined position close to the object to be pressed.

Preferably, when the speed command selection unit selects the third speed command after limitation, the speed controller performs proportional control when the second speed command based on the torque command is not speed-limited by the speed limitation unit, and performs proportional-integral control when the second speed command based on the torque command is speed-limited by the speed limitation unit.

According to the motor control device, the pressure detector and the force detector are not required, and the shift from the position control or the speed control to the torque control with the speed limiting function can be performed at a high speed.

Further, according to the motor control device, the transition from the speed limit state to the torque control can be stably performed at a high speed.

Drawings

Fig. 1 is a block diagram showing one embodiment of a motor control apparatus and method.

Fig. 2 shows a specific configuration example of the speed controller.

Fig. 3A to G show simulation results when the control mode is switched to the torque control mode to perform the pressurizing operation after the member is moved to the position near the contact with the pressurizing object in the position control.

Detailed Description

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

Hereinafter, embodiments of the motor control device and the motor control method according to the present disclosure will be described in detail with reference to the drawings. In addition, the technical scope of the present disclosure is not limited to the description of the embodiments. The technical scope of the present disclosure includes the technical scope of the present disclosure in any way, depending on the claims included in the scope of the patent application.

Fig. 1 shows one embodiment of a motor control device and a motor control method.

As described above (background art), a device and a control method for performing torque control with a speed limit function of a motor based on a torque command and a speed limit command are known. Therefore, detailed description about the known technology is omitted. Embodiments of the present disclosure are described below.

Fig. 1 shows a motor control device a according to an embodiment of the present disclosure. As shown in the figure, the motor control device a controls the torque and position of the motor 21. The motor control device a controls the motor 21 in accordance with a control mode command for either torque or position. The motor control device a controls the position of the motor 21 in accordance with the position command in the position control mode. In the torque control mode, the motor control device a limits the speed in accordance with the speed limit command at a speed equal to or higher than the speed limit command, and controls the torque of the motor 21 in accordance with the torque command at a speed lower than the speed limit command.

The motor control device a generally includes an encoder EN23, a speed detection unit 25, a speed deviation calculator 1, an adder 3, a speed limiting unit 5, a control mode switching unit 7, a first subtractor 10, a second subtractor 11, a speed controller 15, a speed command selection unit 16, a motor torque controller (motor torque control unit) 17, a position controller 35, and the like.

The motor control device a shown in fig. 1 can switch between a torque control mode and a position control mode. Each part of the motor control device a functions as follows.

The speed detector 25 detects the speed of the motor 21 by differentiating the position of the encoder EN 23. The speed deviation calculator 1 calculates the torque command T_CCalculating a torque-based command T_CFirst speed deviation S_DT. That is, the torque command T is set_CThe torque command T is obtained by the speed deviation calculator 1_CFirst speed deviation S_DT。

The adder 3 is based on the torque command T_CFirst speed deviation S_DTAdding the speed V outputted from the speed detecting part 25 to obtain a torque command T_CSecond speed command S_TC。

The speed limiting part 5 limits the command S by speed_LCThe indicated speed limit value pair is based on a torque command T_CSecond speed command S_TCLimiting the speed to obtain a limited third speed command S_CLAnd outputting the limited third speed command S_CL。

The first subtractor 10 is instructed to operate by the slave position instruction L_CSubtracting the position P to obtain a position deviation P_DT. The position controller 35 is based on the position deviation P_DTDetermining a first speed command S from the position controller 35_C. I.e. to make the position deviation P_DTThe position controller 35 determines the position of the object from the position controller 35 first speed command S_C。

The control mode switching part 7 selects the command S based on the speed command from the speed command selecting part 16_TSFor the first speed instruction S from the position controller_CAnd a limited third speed command S_CLSwitching is performed to obtain a motor speed command S_MC. For example, the control mode switching part 7 selects the command S according to the speed command_TSEither one of the position control mode and the torque control mode is selected as a control mode, and the first speed command S is given according to the selection result_CAnd a limited third speed command S_CLEither one of them is used as a motor speed command S_MCAnd output. At a speed command selection command S_TSIs a first speed command S from the position controller 35_CIn the case of (3), the control mode switching unit 7 gives the first speed command S from the position controller 35_CAs motor speed command S_MCAnd output. On the other hand, in the speed command selection command S_TSIs the limited third speed command S_CLIn the case of (3), the control mode switching unit 7 instructs the limited third speed command S_CLAs motor speed command S_MCAnd output. Then, based on the motor speed command S_MCThe speed of the motor 21 is controlled.

When a member driven by the motor 21 approaches a press control target, the upper controller automatically switches the control mode to the signal C according to a position signal or the like_MSAnd (6) taking effect. If the control mode is automatically switched to the signal C_MSIf it is effective, the speed command selection part 16 automatically switches the signal C according to the control mode_MSSelecting a first speed command S from the position controller 35_CAnd the limited third speed command S_CLAny one of them. That is, the speed command selecting unit 16 outputs the first speed command S from the position controller 35_CAnd the limited third speed command S_CLA comparison is made. At a first speed command S from the position controller 35_CThird speed command S after being greater than the limit_CLIn the case of (3), the speed command selecting unit 16 selects the first speed command from the position controller 35Speed command S_CFor example, as a speed command selection command S_TSAnd output. On the other hand, at the first speed command S from the position controller 35_CThird speed command after limitation S_CLIn the following case, the speed command selecting unit 16 selects the limited third speed command S_CLFor example as a speed command selection command S_TSAnd output. Then, according to the selection result (i.e., the output selection command), the motor speed command S is obtained by the control mode switching unit 7, for example_MC. Based on the obtained motor speed command S_MCThe speed of the motor 21 is controlled. Further, the speed command selecting unit 16 may obtain the motor speed command S according to the selection result_MCAnd output.

Specifically, the speed detector 25 obtains the speed of the motor 21 by differentiating the position of the encoder EN23 attached to the motor. The second subtracter 11 is controlled by a slave motor speed command S_MCSubtracting the speed to obtain a second speed deviation S_DAnd outputting the second speed deviation S_D. The speed controller 15 controls the speed of the vehicle by varying the second speed S_DSpeed control calculation is performed as input, and a motor torque command T is calculated_MTAnd outputs the motor torque command T_MT。

The motor torque controller 17 causes the motor 21 to output a motor torque command T_MTThe torque of (1). That is, the motor torque controller 17 outputs a motor torque command T from the motor 21_MTThe torque of (1). The position rotated by the torque output from the motor 21 is detected by an encoder EN 23. Speed control is performed so that the speed corresponding to the detected position and the motor speed command S_MCAnd (5) the consistency is achieved.

The speed controller 15 has a proportional controller 15a and an integral controller 15 b. The speed controller 15 controls the speed according to a speed controller control signal S from a speed command selection unit 16 based on the control state_TSSOnly the proportional controller 15a is operated, or both the proportional controller 15a and the integral controller 15b are operated.

The speed command selection unit 16 selects a speed command fromFirst speed command S of position controller 35_CIn the case of (2), the speed controller 15 controls the speed according to the speed controller control signal S_TSSThe proportional controller 15a and the integral controller 15b are both operated to perform proportional-integral control. The speed command selecting unit 16 selects the restricted third speed command S_CLAnd based on the torque command T_CSecond speed command S_TCWhen the speed limiting unit 5 is subjected to speed limitation, the speed controller 15 performs proportional-integral control in the same manner. The speed command selecting unit 16 selects the restricted third speed command S_CLAnd based on the torque command T_CSecond speed command S_TCWhen the speed limiting section 5 is not speed-limited, the speed controller 15 controls the speed according to the speed controller control signal S_TSSFor example, only the proportional controller 15a is operated to perform proportional control.

In this way, the speed command selection unit 16 selects the restricted third speed command S_CLBased on torque command T_CSecond speed command S_TCWhen the speed limiting unit 5 is not subjected to the speed limitation, the speed controller 15 performs the proportional control, and on the other hand, the proportional control is performed based on the torque command T_CSecond speed command S_TCWhen the speed limitation unit 5 receives the speed limitation, the speed controller 15 performs proportional-integral control.

Fig. 2 shows a more specific configuration example of the speed controller 15 in fig. 1. The proportional controller 15a has a proportional gain 15 a-1. The integration controller 15b has an integration gain 15b-1, an integrator 15b-2, an attenuation gain (integral attenuation gain) 15b-3, and a changeover switch 15 b-4.

When the speed controller 15 is operated as a proportional-integral controller, the terminal 1 of the changeover switch 15b-4 is connected to the integrator 15 b-2. In this way, the integration controller 15b performs an integration operation. When the speed controller 15 is operated as a proportional controller, the terminal 2 of the changeover switch 15b-4 is connected to the integrator 15 b-2. Thus, the value of the integrator 15b-2 is attenuated to 0 by the integral attenuation gain of negative sign, and a proportional operation is performed. Each of the components for controlling the motor may be configured by software. Control calculations are performed for each control sample.

When the position of the member driven by the motor 21 reaches a predetermined position close to the object to be pressed, the speed command selection unit 16 receives the control mode automatic switching signal C_MSAnd the automatic switching of the control mode is enabled. That is, the speed command selecting unit 16 realizes a state in which the position control mode and the torque control mode can be automatically switched.

The speed command selection unit 16 selects a first speed command S from the position controller_CAnd the limited third speed command S_CLA comparison is made.

The speed command selecting section 16 outputs a first speed command S from the position controller 35_CIs greater than the limited third speed command S_CLWhen the value of (3) is selected, the first speed command S from the position controller 35 is selected_CThe value of (c).

On the other hand, the speed command selecting unit 16 outputs the first speed command S from the position controller 35_CIs limited to a third speed command S_CLWhen the value of (A) is less than or equal to (B), the limited third speed command S is selected_CLThe value of (c). Calculating a motor speed command S based on the selected value_MC。

The speed command selecting unit 16 selects the restricted third speed command S_CLAnd based on the torque command T_CSecond speed command S_TCWhen the speed limiting unit 5 is not subjected to the speed limitation, the speed controller 15 performs the proportional control.

On the other hand, based on the torque command T_CSecond speed command S_TCWhen the speed limitation unit 5 receives the speed limitation, proportional-integral control is performed.

At a speed command selection command S_TSTo the limited third speed command S_CLIn the case of (3), the control mode switching unit 7 selects the limited third speed command S_CLAs motor speed command S_MCAnd (6) outputting. Then, as described below, torque control with a speed limiting function is performed.

At this time, the speed controller 15 doesIs the proportional controller 15 a. Assuming that the gain of the proportional controller 15a is GP, the motor speed command S in accordance with the motor speed in the speed control system is utilized_MCCalculating a motor torque command T_MTCan be calculated in reverse from the torque command T_CThe torque command T is calculated as follows_CSecond speed command S_TC。

Based on torque command T_CFirst speed deviation S_DTTorque command T_C/GP (1)

Based on torque command T_CSecond speed command S_TCBased on torque command T_CFirst speed deviation S_DT+ speed V (2)

And, by limiting the command S according to the speed_LCFor the calculated based torque command T_CSecond speed command S_TCLimiting the speed, and obtaining a limited third speed command S_CL。

If according to the limited third speed command S_CLWhen the speed of the motor 21 is controlled, a motor torque command T is given_MTAs described below.

Motor torque command T_MTSecond speed deviation S_DX GP (motor speed command S)_MCVelocity V). times.GP

Here, the motor speed command S is given without speed limitation_MCBased on torque command T_CSecond speed command S_TC. Therefore, the motor torque command T_MTAs described below.

Motor torque command T_MTIs (based on torque command T)_CSecond speed command S_TC-speed V) × GP { (based on torque command T)_CFirst speed deviation S_DT+ speed V) -speed V }. times GP (3)

Here, (based on torque command T)_CFirst speed deviation S_DT) Torque command/GP × GP torque command T_C. Therefore, the motor torque command T_MTAnd torque command T_CAnd (5) the consistency is achieved. According to the motor torque command T_MTPerforming torque control. As a result, the motor 21 outputs the motor torque command T_MTThe motor torque of (1).

In the case of speed limitation, the motor speed command S_MCBecomes a speed limit command S_LC. Therefore, the speed limit instruction S is executed_LCThe speed of the motor 21. As a result, the speed limiting command S is passed_LCAnd carrying out proportional integral control on the speed.

Fig. 3A to G show an example of simulation results when the pressurizing operation is performed by switching the control mode to the torque control mode after the member driven by the motor 21 is moved to the position in front of the contact with the pressurizing object in the position control of the present embodiment. Here, simulation results in the case where a servo welding gun for spot welding is used as an example of the member driven by the motor 21 are shown.

Waveform A represents a first speed command S from position controller 35_C。

Waveform B represents torque command T_CAnd load torque.

Waveform C represents the control (position, torque) mode auto-switch.

Waveform D represents the limited third speed command S_CL。

Waveform E represents a motor speed command S_MC。

Waveform F represents velocity V.

Waveform G represents motor torque command T_MT。

In the position control, when the position of the servo welding gun approaches the pressurizing object, the control mode is automatically switched to be effective (waveform C). If the first speed command S is from the position controller 35_C(waveform A) third speed command S after reaching the limit_CL(waveform D) or less, the speed command selection unit 16 selects the limited third speed command S_CL. Thus, the motor speed command S_MCBecomes the speed limit command S_LCSet speed limit (300 min)^－1) (refer to 0.12-0.14 of waveform E).

If the servo welding gun approaches the pressurizing pair at a limited speedWhen the object comes into contact with the pressurized object, the load torque increases (waveform B), the speed decreases (waveform F), the speed limit state is released, and the torque command T is followed_CMotor torque command T_MTThe subject to be pressurized is pressurized (waveform G).

When the object to be pressurized is pressurized, the control mode is automatically switched to be invalid (waveform C). Since there is no pressure control circuit, the limited third speed command S, which is an output from the torque control system with the speed limiting function_CLThe (waveform D) is a constant and regular value, and switching from the position control to the torque control (switching of the control mode) is performed at high speed and smoothly (waveform G). In addition, even when switching from the speed limit state to the torque control at the time of contact between the servo welding gun and the pressurized object, unstable phenomena such as chattering are not observed, and the switching is performed instantaneously (waveform G).

As described above, according to the motor control device of the embodiment of the present disclosure, the normal position control is performed until the member driven by the motor approaches the pressing control target. On the other hand, when the member driven by the motor approaches the object to be pressed, the control mode is automatically switched to be active. If the control mode automatic switching is effective, the speed command selection part compares the first speed command from the position controller with the limited third speed command. When the first speed command from the position controller is equal to or less than the limited third speed command, the limited third speed command is selected to perform torque control with a speed limiting function.

According to the motor control device of the embodiment of the present disclosure, since there is no pressure control circuit, switching of the control mode is performed at high speed and smoothly. After the control mode is switched, the member driven by the motor operates at a limited speed until the member comes into contact with the pressurized object. When a member driven by a motor comes into contact with a pressurized object, the speed of the member is reduced, and the speed-limited state is released. Since the motor torque command is, for example, a torque command, the pressurizing target is pressurized based on the torque command.

The switching from the speed limit state to the torque control state is also performed smoothly at a high speed because there is no pressure control circuit. According to the torque control with speed limitation function of the control method of the embodiment of the present disclosure, the switching is automatically performed. The torque control system with a speed limiting function performs speed limitation in accordance with the result of addition of a first speed deviation based on a torque command and a speed. Therefore, no pressure control circuit for realizing the speed limitation is provided at the upper level of the speed control circuit, and no special control parameter is required. Even if the gain of the speed controller is low, when the speed limitation is not performed, a motor torque command such as a torque command is calculated, and the motor torque command is not affected by the gain of the speed controller. The gain of the speed controller can be adjusted so that the speed loop is stable when the motor is speed controlled as usual. Further, when the mechanical system has resonance or the like, a notch filter or a low-pass filter may be provided on the output side of the speed controller. In this case, the response to the torque command is reduced by just the portion to which the filter is added.

As described above, according to the motor control device of the embodiment of the present disclosure, the second speed command based on the torque command is calculated based on the torque command. And obtaining a third speed command after limitation by limiting the speed of the second speed command. The first speed command from the position controller is compared with the limited third speed command. When the first speed command from the position controller is larger than the limited third speed command, the first speed command from the position controller is selected. When the first speed command from the position controller is equal to or less than the limited third speed command, the limited third speed command is selected. A motor speed command is obtained according to the selected speed command, and the pressing control is realized. Thus, the following motor control device for press control is provided. The motor control device does not require a pressure detector and a force detector, can perform a transition from position control or speed control to torque control with a speed limiting function at a high speed, and can perform a transition from a speed limiting state to torque control stably at a high speed.

The above-described embodiments each represent one embodiment of the present disclosure. The technique of the present disclosure itself is not limited to the specific structure shown in the above-described manner. The technical scope of the present disclosure should include all technical solutions that can be conceived by one skilled in the art from the contents described in the claims.

In the present embodiment, when the motor and the object to be pressed are close to each other, the upper controller may assert the control mode automatic switching signal in response to a position signal or the like. Further, the normal position control may be performed until the motor approaches the object to be pressed, or the control mode may be automatically switched to be activated when the motor approaches the object to be pressed.

The motor control device according to one aspect of the present disclosure may be the following first motor control device. The first motor control device controls the position of the motor in accordance with the position command in a position control mode in a motor control device that controls the motor in accordance with a control mode command for either torque or position, and controls the torque of the motor in accordance with a speed limit command in a torque control mode in which the speed is limited in accordance with the speed limit command at a speed equal to or higher than the speed limit command and in accordance with a torque command at a speed lower than the speed limit command. The first motor control device includes: a speed detection unit that detects a speed of the motor; a subtractor that subtracts the position from the position command to obtain a position deviation; a position controller for calculating a speed command from the position deviation; a speed deviation calculator for calculating a speed deviation based on the torque command; an adder for obtaining a speed command based on the torque command by adding a speed deviation and a speed based on the torque command; a speed limiting unit that limits a speed command based on the torque command according to a speed limiting command and outputs the limited speed command; a speed command selecting unit that outputs a motor speed command by switching a speed command from the position controller and the limited speed command according to a control mode automatic switching signal; a subtractor that subtracts a speed of the motor from the motor speed command to output a speed deviation; a speed controller for performing a speed control calculation using the speed deviation as an input and outputting a motor torque command; and a motor torque control unit that outputs a torque based on the motor torque command. The speed controller has a proportional controller and an integral controller. The speed command selection unit compares a speed command from the position controller with the limited speed command based on the torque command, selects the value of the speed command from the position controller when the value of the speed command from the position controller is larger than the value of the limited speed command, and selects the value of the limited speed command to obtain a motor speed command when the value of the speed command from the position controller is equal to or smaller than the value of the limited speed command.

The detailed description has been presented for purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. The detailed description is not intended to be exhaustive or to limit the subject matter described herein. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts described are disclosed as example forms of implementing the claims.

Claims

1. A motor control device characterized by comprising:

a speed detection unit that detects a speed of the motor;

a first subtractor that obtains a position deviation by subtracting the position from the position command;

a position controller for calculating a first speed command based on the position deviation;

a speed deviation calculator that obtains a first speed deviation based on the torque command;

an adder that obtains a second speed command based on the torque command by adding a first speed deviation based on the torque command to the speed;

a speed limiting unit that limits a second speed command based on the torque command in accordance with a speed limiting command, obtains a third speed command after the limitation, and outputs the third speed command after the limitation;

a speed command selecting unit that selects either one of the first speed command from the position controller and the restricted third speed command, based on a control mode automatic switching signal;

a second subtractor that obtains a second speed deviation by subtracting the speed of the motor from a motor speed command and outputs the second speed deviation;

a speed controller that calculates a motor torque command by performing a speed control calculation using the second speed deviation as an input, and outputs the motor torque command; and

a motor torque control unit that causes the motor to output a torque based on the motor torque command,

the speed controller has a proportional controller and an integral controller,

the speed command selection unit compares the first speed command from the position controller with the restricted third speed command, selects the value of the first speed command from the position controller when the value of the first speed command from the position controller is greater than the value of the restricted third speed command, selects the value of the restricted third speed command when the value of the first speed command from the position controller is equal to or less than the value of the restricted third speed command, and obtains the motor speed command from the selected value.

2. The motor control device according to claim 1, wherein the speed command selection unit validates the automatic switching of the control mode when a position of the member driven by the motor reaches a predetermined position close to a pressing control target.

3. The motor control device according to claim 1 or 2,

the speed controller is configured to control the speed of the motor,

when the speed command selecting unit selects the limited third speed command,

when a second speed command based on the torque command is not subjected to speed limitation in the speed limiting section, proportional control is performed, while,

when a second speed command based on the torque command is subjected to speed limitation in the speed limiting section, proportional-integral control is performed.