Motor control device

Abstract

The present application provides a kind of motor control device, comprising: the speed detection unit of detecting the speed of motor;According to the position deviation, the position controller of first speed instruction is obtained;By limiting the second speed instruction based on torque instruction, the speed limiting unit of third speed instruction after limiting is obtained;And according to the control mode automatic switching signal, the speed instruction selection unit selects any one of first speed instruction and third speed instruction, and the motor speed instruction is obtained according to the selected value.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor control device. BACKGROUND

[0002] In welding of a workpiece using a servo welding gun (electric welding gun) for spot welding, the workpiece is gripped by a welding tip of an electrode portion of the electric welding gun. Also, while the workpiece is pressed by controlling the torque of a motor, electric current is passed between the welding tips. In this way, the workpiece is welded. Such an electric welding gun is moved to the vicinity of contact with a pressurization target by position control or speed control. Subsequently, the control mode is switched to a torque control mode, and the pressurization target is pressed by the electric welding gun. Also, in order to suppress collision of the electric welding gun and the pressurization target due to excessive speed of the electric welding gun at the time of switching the control mode to the torque control mode, the torque control mode is implemented with a speed limit function. After the welding is completed, the control mode is switched to the position control mode or the speed control mode again, and the electric welding gun is moved.

[0003] An example of implementing press control while switching the control mode between the position control mode or the speed control mode and the torque control mode is described in Japanese Patent No. 6113378. The motor control device described in Japanese Patent No. 6113378 controls a motor provided with an encoder. The motor control device is provided with a position command generation portion, a position control portion, a pressure command generation portion, a pressure control portion, a speed command selection portion, and a speed control portion. The position command generation portion generates a position command. The position command is a command value for bringing a mechanical load driven by the motor close to a pressurization target and reaching a final position of the mechanical load to a certain distance before the pressurization target. The position control portion outputs a first speed command so that the position of the motor detected by the encoder follows the position command. The pressure command generation portion generates a command value of pressure or force to be applied to the pressurization target, that is, a pressure command. The pressure control portion outputs a second speed command so that the pressure or force detected by the mechanical load when the mechanical load presses the pressurization target follows the pressure command. The speed command selection portion selects either one of a creep speed, the first speed command, and the second speed command as a speed command for operating the motor and outputs it. The creep speed defines an upper limit of the speed of the motor when the mechanical load contacts the pressurization target. The speed control portion outputs a current command for supplying current to the motor so that the speed of the motor follows the speed command output from the speed command selection portion. The speed command selection portion selects either one of the second speed command and the creep speed that is smaller after selecting the first speed command and after the first speed command is lower than the creep speed.

[0004] Thus, according to the method of Japanese Patent No. 6113378, at the timing when the first speed command is lower than the creep speed, processing of selecting the smaller value of either the second speed command or the creep speed is implemented. However, in this method, in order to constitute the pressure control section, a pressure detector or a force detector is required. Therefore, according to this method, on an apparatus where such a detector is difficult to set, it is difficult to perform the press control. Further, due to noise contained in the output from the pressure detector or the force detector or the rigidity of the machine constituting the pressure control circuit, there are cases where an unstable factor is generated. At this time, fluctuations are generated in the speed command from the pressure control section. Therefore, in the vicinity of the timing of switching between the creep speed and the second speed command, the pressure control circuit is cut off and restored. Therefore, the operation of the pressure control circuit becomes unstable. SUMMARY

[0005] One object of the present disclosure is to provide a motor control device for press control that does not require a pressure detector and a force detector, is capable of shifting from position control or speed control to torque control with a speed limit function at high speed, and is capable of shifting from a speed limit state to torque control at high speed and stably.

[0006] The motor control device according to one embodiment of the present disclosure (the present motor control device) includes: a speed detection section that detects a speed of a motor; a first subtractor that obtains a position deviation by subtracting a position from a position command; a position controller that obtains a first speed command based on the position deviation; a speed deviation calculator that obtains a first speed deviation based on a torque command; an adder that obtains a second speed command based on the torque command by adding the first speed deviation based on the torque command to the speed; a speed limiter that obtains a limited third speed command by limiting the second speed command based on the torque command according to a speed limit command and outputs the limited third speed command; a speed command selector that selects either the first speed command from the position controller or the limited third speed command according to 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 performs a speed control calculation by taking the second speed deviation as an input, calculates a motor torque command, and outputs the motor torque command; and a motor torque control section 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 selector compares the first speed command from the position controller with the limited third speed command, selects a value of the first speed command from the position controller in a case where the value of the first speed command from the position controller is greater than a value of the limited third speed command, selects the value of the limited third speed command in a case where the value of the first speed command from the position controller is below the value of the limited third speed command, and obtains a motor speed command based on the selected value.

[0007] It is preferable that the speed command selector causes the control mode automatic switching to take effect if a position of a member driven by the motor reaches a prescribed position close to a press control object.

[0008] It is preferable that the speed controller be configured to perform proportional control in a case where the second speed command based on the torque command is not subjected to speed limitation in the speed limiter when the speed command selector selects the limited third speed command, and to perform proportional integral control in a case where the second speed command based on the torque command is subjected to speed limitation in the speed limiter.

[0009] According to the present motor control device, a pressure detector and a force detector are not required, and a shift from position control or speed control to torque control with a speed limitation function can be performed at high speed.

[0010] Further, according to the present motor control device, it is possible to perform the shift from the speed limit state to the torque control at high speed and stably. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a block diagram showing one embodiment of a motor control device and method.

[0012] Figure 2 shows a structure example of a specific speed controller.

[0013] Figure 3A ~G shows a simulation result when the control mode is switched to the torque control mode to perform a pressing operation after the member is moved to the vicinity of contact with the pressing object in the position control. DETAILED DESCRIPTION

[0014] In the following detailed description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments can be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.

[0015] Hereinafter, embodiments of a motor control device and a motor control method according to the present disclosure will be specifically described with reference to the accompanying 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 all the technical spirits falling within the scope of the claims, and the technical scope of the present disclosure is not limited by the embodiments.

[0016] Figure 1 shows one embodiment of a motor control device and a motor control method.

[0017] A device and a control method for performing torque control of a motor based on a torque command and a speed limit command with a speed limit function of the motor have been known as described above (BACKGROUND ART). Therefore, detailed description about the known technology is omitted. Embodiments of the present disclosure are described as follows.

[0018] Figure 1 shows a motor control device A related to the embodiments of the present disclosure. As shown in the figure, the motor control device A controls the torque and the position of a motor 21. The motor control device A controls the motor 21 according to a control mode command of either the torque or the position. The motor control device A controls the position of the motor 21 according to a position command in a position control mode. Further, the motor control device A limits the speed according to a speed limit command at a speed equal to or higher than the speed limit command in a torque control mode, and on the other hand, controls the torque of the motor 21 according to a torque command at a speed lower than the speed limit command.

[0019] 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 limiter 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, and a position controller 35, etc.

[0020] Figure 1 The motor control device A shown can switch between torque control mode and position control mode. The functions of each part of the motor control device A are as follows.

[0021] The speed detection unit 25 detects the speed of the motor 21 by differentiating the position of the encoder EN23. The speed deviation calculator 1 calculates the speed based on the torque command T. C Calculation based on torque command T C First velocity deviation S DT That is, to make the torque command T... C The torque command T is thus calculated using the speed deviation calculator 1. C First velocity deviation S DT .

[0022] Adder 3 will use torque command T as the basis for the addition. C First velocity deviation S DT Add the speed V output from the speed detection unit 25 to obtain the torque command T. C Second speed command S TC .

[0023] Speed ​​limit unit 5 uses speed limit command S LC The indicated speed limit value is based on the torque command T. C Second speed command S TC Apply speed limits to determine the third speed command S after the speed limit is applied. CL and outputs the third speed command S after the limitation. CL .

[0024] The first subtractor 10 is activated by the position instruction L. C Subtract position P to find position deviation P DT The position controller 35 determines the position deviation P based on the position deviation P. DT Calculate the first speed command S from the position controller 35. C That is, to make the positional deviation P DT The first speed command S from the position controller 35 is thus obtained. C .

[0025] The control mode switching unit 7 selects the speed command S from the speed command selection unit 16. TS The first speed command S from the position controller C and the restricted third speed command S CL The switching is performed to determine the motor speed command S. MC For example, the control mode switching unit 7 selects command S based on the speed command. TS Select either position control mode or torque control mode as the control mode, and transmit the first speed command S according to the selection result. C and the limited third speed command S CL Either one can be used as the motor speed command S MC And the output. In the speed command selection command S... TS The first speed command S comes from the position controller 35. C In this case, the control mode switching unit 7 will receive the first speed command S from the position controller 35. C As the motor speed command S MC And the output. On the other hand, in the speed command selection instruction S TS It is the restricted third speed command S CL In this case, the control mode switching unit 7 will limit the third speed command S. CL As the motor speed command S MC And the output. Furthermore, according to the motor speed command S... MC Control the speed of motor 21.

[0026] When the component driven by motor 21 approaches the object being pressed, the upper controller, based on position signals and other factors, sends an automatic control mode switching signal C. MS Effective. If the control mode automatically switches signal C... MS If it takes effect, the speed command selection unit 16 will automatically switch signal C according to the control mode. MS Select the first speed command S from the position controller 35 C With the restricted third speed command S CL Either of the two. That is, the speed command selection unit 16 will select the first speed command S from the position controller 35. C With the restricted third speed command S CL Comparison. The first speed command S from position controller 35. C The third speed command S after exceeding the limit CL In this case, the speed command selection unit 16 selects the first speed command S from the position controller 35. C For example, as a speed command selection command S TSand output. On the other hand, in the case where the first speed command S C the third speed command S CL The speed command selection section 16 selects the third speed command S CL , for example, as the speed command selection command S TS and outputs. Also, in accordance with the selection result (i.e., the output selection command), the motor speed command S MC is calculated, for example, by the control mode switching section 7. In accordance with the calculated motor speed command S MC , the speed of the motor 21 is controlled. Alternatively, the speed command selection section 16 can calculate the motor speed command S MC in accordance with the selection result and output.

[0027] The actual speed detection section 25 calculates the speed of the motor 21 by differentiating the position of an encoder EN23 attached to the motor. The second subtracter 11 calculates a second speed deviation S MC by subtracting the speed from the motor speed command S D and outputs the second speed deviation S D . The speed controller 15 performs a speed control calculation by taking the second speed deviation S D as an input, calculates a motor torque command T MT , and outputs the motor torque command T MT .

[0028] The motor torque controller 17 causes the motor 21 to output a torque based on the motor torque command T MT . That is, the motor torque controller 17 causes the motor 21 to output a torque in accordance with the motor torque command T MT . The position of the rotation by the torque output from the motor 21 is detected by the encoder EN23. The speed control is performed so that the speed corresponding to the detected position coincides with the motor speed command S MC .

[0029] The speed controller 15 has a proportional controller 15a and an integral controller 15b. The speed controller 15 causes only the proportional controller 15a to act or causes both the proportional controller 15a and the integral controller 15b to act in accordance with a speed controller control signal S TSS from the speed command selection section 16 based on the control state.

[0030] In the case where the speed command selection section 16 selects the first speed command S C from the position controller 35, the speed controller 15 causes only the proportional controller 15a to act in accordance with the speed controller control signal S TSSThis causes both the proportional controller 15a and the integral controller 15b to operate, performing proportional-integral control. The speed command selection unit 16 selects the third speed command S after the limit. CL And based on torque command T C Second speed command S TC When the speed is limited in the speed limiting unit 5, the speed controller 15 also performs proportional-integral control. The speed command selection unit 16 selects the third speed command S after the speed limit is applied. CL And based on torque command T C Second speed command S TC When there is no speed limit in the speed limiting section 5, the speed controller 15 controls the speed according to the speed controller control signal S. TSS For example, only the proportional controller 15a is activated to perform proportional control.

[0031] Thus, the speed command selection unit 16 selects the third speed command S after the limit is reached. CL At that time, based on torque command T C Second speed command S TC When there is no speed limit in the speed limiting section 5, the speed controller 15 performs proportional control; on the other hand, based on the torque command T... C Second speed command S TC When the speed is limited in the speed limiting section 5, the speed controller 15 performs proportional-integral control.

[0032] Figure 2 It indicates Figure 1 A more specific example of the structure of the speed controller 15 is shown below. The proportional controller 15a has a proportional gain 15a-1. The integral controller 15b has an integral gain 15b-1, an integrator 15b-2, an attenuation gain (integral attenuation gain) 15b-3, and a switching switch 15b-4.

[0033] When the speed controller 15 is operated as a proportional-integral controller, connect terminal 1 of the switch 15b-4 to the integrator 15b-2. This causes the integrator 15b to perform integral operation. When the speed controller 15 is operated as a proportional controller, connect terminal 2 of the switch 15b-4 to the integrator 15b-2. This causes the value of the integrator 15b-2 to decay to 0 due to the negative integral attenuation gain, thus performing proportional operation. The aforementioned components for motor control can be configured using software. Control calculations are performed for each control sample.

[0034] If the position of the component driven by the motor 21 approaches the predetermined position of the pressing control object, the speed command selection unit 16 receives the control mode automatic switching signal C. MSThe automatic switching of the control mode is made effective. That is, the speed command selection section 16 realizes a state in which the position control mode and the torque control mode are automatically switchable.

[0035] The speed command selection section 16 compares the first speed command S C from the position controller with the third speed command S CL after the limitation.

[0036] The speed command selection section 16 selects the value of the first speed command S C from the position controller 35 in a case where the value of the first speed command S CL from the position controller 35 is larger than the value of the third speed command S C after the limitation.

[0037] On the other hand, the speed command selection section 16 selects the value of the third speed command S C after the limitation in a case where the value of the first speed command S CL from the position controller 35 is equal to or smaller than the value of the third speed command S CL after the limitation. The motor speed command S MC is calculated based on the selected value.

[0038] In a case where the third speed command S CL after the limitation is selected by the speed command selection section 16 and the second speed command S C based on the torque command T TC is not subjected to speed limitation in the speed limiter 5, the speed controller 15 performs proportional control.

[0039] On the other hand, in a case where the second speed command S C based on the torque command T TC is subjected to speed limitation in the speed limiter 5, proportional integral control is performed.

[0040] In a case where the speed command S TS is the third speed command S CL after the limitation, the control mode switching section 7 selects the third speed command S CL after the limitation as the motor speed command S MC output. Moreover, torque control with a speed limitation function is implemented as described below.

[0041] At this time, the speed controller 15 operates as a proportional controller 15a. When the gain of the proportional controller 15a is set to GP, the calculation of the motor torque command T MT from the motor speed command S MC in the speed control system is calculated in a reverse direction, and the torque command T CThe second speed command S C based on the torque command T TC is calculated as follows.

[0042] The first speed deviation S C based on the torque command T DT = torque command T C / GP (1)

[0043] The second speed command S C based on the torque command T TC = first speed deviation S C based on the torque command T DT + speed V (2)

[0044] Further, by speed-limiting the calculated second speed command S LC based on the torque command T C according to the speed limit command S TC , a third speed command S CL after limitation is calculated.

[0045] If the speed control of the motor 21 is performed according to the third speed command S CL after limitation, the motor torque command T MT is as follows.

[0046] Motor torque command T MT = second speed deviation S D x GP = (motor speed command S MC - speed V) x GP

[0047] Here, in the case where the speed limitation is not performed, the motor speed command S MC = second speed command S C based on the torque command T TC . Therefore, the motor torque command T MT is as follows.

[0048] Motor torque command T MT = (second speed command S C based on the torque command T TC - speed V) x GP = {(first speed deviation S C based on the torque command T DT + speed V) - speed V} x GP (3)

[0049] Here, (first speed deviation S C based on the torque command T DT ) x GP = torque command / GP x GP = torque command T C . Therefore, the motor torque command TMT and the torque command T C is made in accordance with the motor torque command T MT Torque control is performed. As a result, the motor torque in accordance with the motor torque command T MT is output from the motor 21.

[0050] In the case where the speed limit is implemented, the motor speed command S MC becomes the speed limit command S LC . Therefore, speed control of the motor 21 based on the speed limit command S LC is performed. As a result, proportional integral control of the speed by the speed limit command S LC is performed.

[0051] Figure 3A ~G shows an example of a simulation result when the pressing 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 vicinity of contact with the pressing object in the position control of the present embodiment. Here, a simulation result in the case where a spot welding servo welding gun is used as an example of the member driven by the motor 21 is shown.

[0052] Waveform A shows the first speed command S C from the position controller 35.

[0053] Waveform B shows the torque command T C and the load torque.

[0054] Waveform C shows the control (position, torque) mode automatic switching.

[0055] Waveform D shows the third speed command S CL after the limit.

[0056] Waveform E shows the motor speed command S MC .

[0057] Waveform F shows the speed V.

[0058] Waveform G shows the motor torque command T MT .

[0059] In the position control, if the position of the servo welding gun approaches the pressing object, the control mode automatic switching takes effect (waveform C). If the first speed command S C from the position controller 35 (waveform A) reaches the third speed command S CL after the limit (waveform D) or less, the speed command selection section 16 selects the third speed command S CL after the limit. In this way, the motor speed command S MC becomes the speed limit command SLC The set speed limit value (300 min －1 )(refer to 0.12-0.14 of waveform E).

[0060] Moreover, if the servo welding gun approaches the pressurized object at the limited speed and 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 motor torque command T C is set according to the torque command T MT The pressurized object is pressurized (waveform G).

[0061] If the pressurized object is pressurized, the control mode is automatically switched to be invalid (waveform C). Since there is no pressure control circuit, the output from the torque control system with the speed limit function, i.e., the third speed command S CL after the limit (waveform D) is a certain constant value, and the switching from the position control to the torque control (switching of the control mode) is performed at high speed and smoothly (waveform G). Furthermore, at the time of switching from the speed limit state to the torque control when the servo welding gun comes into contact with the pressurized object, no unstable phenomenon such as chattering is observed, and the switching is performed instantaneously (waveform G).

[0062] As described above, the motor control device according to the embodiment of the present disclosure performs the normal position control until the member driven by the motor approaches the press control object. On the other hand, if the member driven by the motor approaches the press control object, the control mode is automatically switched to be valid. If the control mode is automatically switched to be valid, the speed command selection section compares the first speed command from the position controller with the third speed command after the limit. If the first speed command from the position controller is below the third speed command after the limit, the third speed command after the limit is selected to perform the torque control with the speed limit function.

[0063] The motor control device according to the embodiment of the present disclosure performs the switching of the control mode at high speed and smoothly since there is no pressure control circuit. After the control mode is switched, the member driven by the motor operates at the limited speed until the member comes into contact with the pressurized object. If the member driven by the motor comes into contact with the pressurized object, the speed of the member decreases, and the speed limit state is released. Moreover, the motor torque command becomes the torque command T

[0064] The switching from the speed limit state to the torque control state is also implemented at high speed and smoothly because there is no pressure control loop. The torque control with the speed limit function according to the control method of the embodiment of the present disclosure automatically implements the switching. The torque control with the speed limit function implements the speed limit based on the sum of the first speed deviation based on the torque command and the speed. Therefore, there is no pressure control loop for implementing the speed limit in the upper stage of the speed control loop, and no special control parameter is required. Even if the gain of the speed controller is low, the motor torque command such as the torque command is calculated when the speed limit is not implemented, 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 generally controlled in speed. Furthermore, when there is a resonance or the like in the mechanical system, a notch filter or a low-pass filter can be provided on the output side of the speed controller. At this time, the response to the torque command is reduced only in the portion of the additional filter.

[0065] As described above, the motor control device according to the embodiment of the present disclosure calculates a second speed command based on the torque command from the torque command. A third speed command after the speed limit is obtained by performing the speed limit on the second speed command. The first speed command from the position controller is compared with the third speed command after the speed limit. In the case where the first speed command from the position controller is greater than the third speed command after the speed limit, the first speed command from the position controller is selected. In the case where the first speed command from the position controller is equal to or less than the third speed command after the speed limit, the third speed command after the speed limit is selected. A motor speed command is obtained according to the selected speed command, and the press control is implemented. In this way, the motor control device for press control is provided. The motor control device does not require a pressure detector and a force detector, can perform the shift from the position control or the speed control to the torque control with the speed limit function at high speed, and can perform the shift from the speed limit state to the torque control at high speed and stably.

[0066] Each of the above-described modes represents one mode of the present disclosure. The technology of the present disclosure is not limited to the specific structure shown in the above-described modes. The scope of the technology of the present disclosure should include all technical solutions that can be conceived by those skilled in the art based on the content described in the claims.

[0067] In addition, in the embodiment, the upper controller can validate the control mode automatic switching signal according to the position signal or the like in the case where the motor approaches the press control object. Furthermore, the conventional position control can be implemented until the motor approaches the press control object, or the control mode automatic switching can be validated if the motor approaches the press control object.

[0068] Further, the motor control device of one embodiment of the present disclosure can be the following first motor control device. The first motor control device is a motor control device that controls a motor in accordance with a control mode instruction of either a torque or a position, controls the position of the motor in accordance with a position instruction in a position control mode, controls the torque of the motor in accordance with a torque instruction at a speed lower than a speed limit instruction in a torque control mode, and controls the speed of the motor in accordance with the speed limit instruction at a speed equal to or higher than the speed limit instruction. The first motor control device includes a speed detection unit that detects the speed of the motor; a subtracter that calculates a position deviation by subtracting a position from a position instruction; a position controller that calculates a speed instruction from the position deviation; a speed deviation calculator that calculates a speed deviation based on a torque instruction; an adder that calculates a speed instruction based on the torque instruction by adding the speed deviation based on the torque instruction and the speed; a speed limiter that outputs a limited speed instruction by limiting the speed instruction based on the torque instruction in accordance with a speed limit instruction; a speed instruction selector that outputs a motor speed instruction by switching the speed instruction from the position controller and the limited speed instruction in accordance with a control mode automatic switching signal; a subtracter that outputs a speed deviation by subtracting the speed of the motor from the motor speed instruction; a speed controller that performs speed control calculation with the speed deviation as input and outputs a motor torque instruction; and a motor torque control unit that outputs a torque based on the motor torque instruction. The speed controller has a proportional controller and an integral controller. The speed instruction selector compares the speed instruction from the position controller and the limited speed instruction based on the torque instruction, selects the value of the speed instruction from the position controller in the case where the value of the speed instruction from the position controller is greater than the value of the limited speed instruction, selects the value of the limited speed instruction in the case where the value of the speed instruction from the position controller is equal to or lower than the value of the limited speed instruction, and calculates a motor speed instruction.

[0069] The detailed description has been set forth with the intent to illustrate various aspects of the subject matter. Many variations and alterations are possible in the detailed description. The detailed description is not intended to limit or restrict the subject matter to the particular examples disclosed. 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 are disclosed as example implementations of the subject matter.

Claims

1. An electric motor control device characterized by comprises: a speed detector that detects a speed of the motor; a first subtractor that obtains a position deviation by subtracting a position from a position command; a position controller that obtains a first speed command based on the position deviation; a speed deviation calculator that obtains a first speed deviation based on a torque command; an adder that obtains a second speed command based on the torque command by adding the first speed deviation based on the torque command to the speed; a speed limiter that obtains a third speed command after limitation by limiting the second speed command based on the torque command according to a speed limitation command and outputs the third speed command after limitation; a speed command selector that selects either the first speed command from the position controller or the third speed command after limitation 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 performs speed control calculation by taking the second speed deviation as an input, calculates a motor torque command, and outputs the motor torque command; and a motor torque control section that causes the motor to output a torque based on the motor torque command, the speed command selector compares the first speed command from the position controller with the third speed command after limitation, selects a value of the first speed command from the position controller in a case where the value of the first speed command from the position controller is greater than the value of the third speed command after limitation, selects a value of the third speed command after limitation in a case where the value of the first speed command from the position controller is below the value of the third speed command after limitation, and obtains a motor speed command based on the selected value, the speed controller has a proportional controller and an integral controller, the speed controller is configured so that, in a case where the speed command selector selects the value of the third speed command after limitation, the speed controller controls the motor based on a speed controller control signal from the speed command selector, in a case where the second speed command based on the torque command is not subjected to speed limitation in the speed limiter, the proportional control is performed, and in a case where the second speed command based on the torque command is subjected to speed limitation in the speed limiter, the proportional integral control is performed.

2. The motor control device according to claim 1, characterized by The speed command selector causes the control mode automatic switching to take effect if a position of a member driven by the motor reaches a prescribed position close to a press control object.

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