JP2021175206A - Motor control device - Google Patents

Abstract

To provide a motor control device for pressing control without requiring a pressure detector and a force detector, and capable of performing high speed transition from position control and speed control to torque control having speed restriction function.SOLUTION: A motor control device controlling a motor on the basis of a control mode command of either one of torque or a position has: a speed detection part detecting motor speed; a position controller obtaining a speed command on the basis of positional deviation; a speed restriction part outputting a speed command after restriction, by restricting the speed command based on a torque command on the basis of a speed restriction command; a speed command selection part outputting a motor speed command by switching the speed command from the position controller with the speed command after restriction, on the basis of a control mode automatic switching signal; a subtractor outputting a speed deviation by subtracting the motor speed from the motor speed command; a speed controller performing a speed control operation using the speed deviation as an input and outputting the motor torque command; and a motor torque controlling part causing the torque to be outputted based on the motor torque command.SELECTED DRAWING: Figure 1

Description

The present invention relates to a motor control device for pressing control.

In the spot welding servo gun, the work is sandwiched between the welding tips of the electrode portion of the welding gun, the torque of the motor is controlled and pressurized, and the electrodes are energized to weld the work. In such a welding gun, the position control or speed control is used to move the welding gun to the point where it comes into contact with the pressurizing target, and the welding gun is switched to torque control to pressurize. Then, torque control having a speed limiting function is performed so that an excessive speed is not generated when the torque control is switched to and the pressure target is not collided with the pressurized object. When the welding is completed, the movement is performed again by position control and speed control.

Patent Document 1 is an example in which pressing control is performed by switching between position control, speed control, and torque control. Patent Document 1 describes a motor control device for controlling a motor including an encoder, in which a mechanical load driven by the motor approaches a pressurized object and the final position of the mechanical load is the pressurized object. A position command generator that generates a position command that is a command value that should be a certain distance before, and a position control unit that outputs a first speed command so that the position of the motor detected by the encoder follows the position command. A pressure command generator that generates a pressure command, which is the command value of the pressure or force to be applied to the object to be pressurized, and the pressure or force detected by the mechanical load when the mechanical load is pressed against the object to be pressurized. A pressure control unit that outputs a second speed command so that And the second speed command is selected so that the speed of the motor follows the speed command selection unit output as the speed command to be operated by the motor and the speed command output by the speed command selection unit. It is equipped with a speed control unit that outputs a current command that supplies current to the motor, and the speed command selection unit selects the first speed command and then after the timing when the first speed command falls below the creep speed, A motor control device is described that comprises selecting a second speed command or a smaller value of creep speed.

As described above, in the method of Patent Document 1, a process of selecting the second speed command or a value having a small creep speed is performed after the timing when the first speed command falls below the creep speed. However, a pressure detector and a force detector are required to form the pressure control unit, and there is a problem that the pressing control cannot be performed in the equipment not provided with such a detector. In addition, if there is noise contained in the output of the pressure or force detector, or if there is an unstable element due to the rigidity of the machine that constitutes the pressure control loop, ripple will occur in the speed command from the pressure control unit, and the creep speed and the first In the vicinity where the speed command of 2 is switched, the pressure control loop is interrupted or revived, so that there is a problem that the operation becomes unstable.

Japanese Patent No. 6113378

The present invention has been made to solve the above problems, and an object thereof is to change from position control and speed control to torque control with a speed limit function without the need for a pressure detector or a force detector. It is an object of the present invention to provide a motor control device for pressing control capable of performing a high-speed transition and further performing a high-speed and stable transition from a speed limit state to torque control.

According to one aspect of the present invention, in a motor control device that controls a motor based on a control mode command of either torque or position, in the position control mode, the position of the motor is controlled according to the position command, and the torque is described. In the control mode, it is a motor control device that limits the speed according to the speed limit command at a speed higher than the speed limit command and controls the torque of the motor according to the torque command at a speed lower than the speed limit command. Is a speed detector that detects the speed of the motor, a subtractor that subtracts the position from the position command to obtain the position deviation, a position controller that obtains the speed command based on the position deviation, and a speed based on the torque command. A speed deviation calculator that calculates the deviation, an adder that adds the speed deviation and speed based on the torque command to obtain the speed command based on the torque command, and a speed command based on the torque command is limited based on the speed limit command. A speed limit unit that outputs a later speed command, and a speed command selection unit that switches between a speed command from the position controller and a speed command after the limit based on a control mode automatic switching signal and outputs a motor speed command. , A subtractor that subtracts the speed of the motor from the motor speed command and outputs a speed deviation, a speed controller that performs a speed control calculation using the speed deviation as an input and outputs a motor torque command, and the motor torque command. The speed controller includes a proportional controller and an integral controller, and the speed command selection unit includes a speed command from the position controller. Compare with the speed command after the limitation based on the torque command, and if the value of the speed command from the position controller is larger than the value of the speed command after the limitation, the value of the speed command from the position controller is used. If the value of the speed command from the position controller is equal to or less than the value of the speed command after the limitation, the value of the speed command after the limitation is selected to obtain the motor speed command. A featured motor control device is provided.

The speed command selection unit may enable automatic control mode switching when the position of the member driven by the motor reaches a predetermined position close to the pressing control target.

The speed controller selects the speed command after the limitation by the speed command selection unit, and when the speed command based on the torque command is not speed-limited by the speed limiting unit, proportional control is performed. When the speed command based on the torque command is speed-limited in the speed limiting unit, it is preferable that proportional integration control is performed.

According to the present invention, the transition from position control and speed control to torque control with a speed limiting function can be performed at high speed without the need for a pressure detector or a force detector.
Further, it is possible to provide a control device for a motor for pressing control capable of performing a transition from a speed limit state to torque control at high speed and stably.

FIG. 1 is a block diagram showing an aspect of a motor control device and a method. FIG. 2 is a diagram showing a specific configuration example of the speed controller. FIG. 3 is a diagram showing a simulation result in the case where the position control moves to the front side of contact with the pressurization target and the torque control is switched to perform the pressurization operation.

Hereinafter, embodiments of the motor control device and method according to the present invention will be described in detail with reference to the drawings. The scope of the present invention is not limited by the description of this embodiment, and any aspect of the present invention can be used as long as it belongs to the technical scope of the invention according to each claim of the claims. It is included in the range.
FIG. 1 shows an aspect of a motor control device and a method.

As described in the above [Background Art], the torque control device and the control method with the speed limit function of the motor based on the torque command and the speed limit command are known, so detailed description thereof will be omitted. , The embodiment of the present invention is as follows.

The motor control device A that controls the torque and position of the motor of the motor 21 of the present invention is roughly a speed detection unit 25 that obtains a speed by differentiating the positions of the encoder EN23 and the encoder EN23, a speed deviation calculator 1, and an adder. 3. It is composed of a speed limiting unit 5, a control mode switching unit 7, a subtractor 11, a speed controller 15, a speed command selection unit 16, a motor torque controller 17, a position controller 35, and the like.

The embodiment shown in FIG. 1 shows an example in which the torque control mode and the position control mode can be switched. The functions of each part of the motor control device A are as follows. Obtain a velocity deviation S _DT based on the torque command through the torque command T _C the speed deviation calculator 1. _{The speed deviation SDT} based on the torque command and the speed V are added by the adder 3 to obtain the _{speed command STC based on the torque command.} In the speed limiting unit 5, and the speed limit at the speed limit value commanded the speed command S _TC based on the torque command T _C at a rate limiting command S _LC, it obtains a speed command S _CL after restriction.
Further, by subtracting the position P from the position command L _C, it obtains the position deviation P _DT, determine the speed designation S _C from the position controller through a position controller 35.

In the control mode switching unit 7, based on the speed command selection instruction S _TS from the speed command selection section 16 switches the speed command S _CL after limiting the speed command S _C from the position controller to obtain the motor speed S _MC .. If the speed command selection instruction S _TS is the speed command from the position controller to the speed command S _C from the position controller and motor speed S _MC, the speed command selection instruction S If _TS is the speed command S _CL after restriction _Sets the speed command S CL after the limit to the motor speed command S _MC . Then, based on the motor speed S _MC, control the speed of the motor.

When the motor 21 approaches the control target Pushing, host controller based on the position signal, etc., to enable control mode automatic switching signal C _MS. When the control mode automatically switching signal C _MS is enabled, the speed command selection section 16 compares the speed command S _CL after limiting the speed command S _C from the position controller, the speed command S _C from the position controller greater than the speed command S _CL after restriction selects the speed command S _C from the position controller, the speed command S _C from the position controller is below the limit after the speed command S _CL, the speed command after restriction Select S _CL to obtain the motor speed command S _MC . Based on the motor speed _{S MC,} control the speed of the motor 21.

Specifically, the speed is obtained by differentiating the position of the encoder EN23 attached to the motor. The speed is subtracted from the motor speed command S _MC to obtain the speed deviation S _D, and the motor torque command T _MT is calculated through the speed controller 15. Based on the motor torque command T _MT , the motor torque controller 17 outputs the torque according to the motor torque command T _MT from the motor. The position rotated by the output torque from the motor detected by the encoder EN23, speed control is performed to match the motor speed S _MC.

The speed controller 15 has a proportional controller 15a, and can be operated only by the proportional controller 15a or integrated control with the proportional controller 15a by _{the speed controller control signal TSSS} from the speed command selection unit 16 based on the control state. Both of the vessels 15b are operated.
A speed command selection section 16, if the speed command S _C from the position controller is selected, a proportional integral control by operating both the proportional controller 15a and the integral controller 15b by a speed controller control signal S _TSS I do. Though the speed command S _CL after restricted speed command selection section 16 is selected, the same proportional integral control even when the speed command based on the torque command T _C is afflicted with speed limit. Though the speed command S _CL after restricted speed command selection section 16 is selected, if the speed command based on the torque command T _C is not applied to the speed limit performs proportional control by the speed controller control signal S _TSS.

FIG. 2 is a diagram showing a more specific configuration example of the speed controller 15 in FIG. The proportional gain 15a-1 constitutes the proportional controller 15a, and the integral gain 15b-1 and the integrator 15b-2, and the integral attenuation gain 15b-3 and the changeover switch 15b-4 constitute the integrator controller 15b. ..

When the speed controller 15 is operated by the proportional integration control, the changeover switch 15b-4 is set to 1, and the integration controller 15b is made to perform the integration operation. When the speed controller 15 is operated by the proportional controller, the changeover switch 15b-4 is set to 2, the value of the integrator 15b-2 is attenuated based on the integral attenuation gain of the minus sign and set to 0, and the proportional operation is performed. Let me. Each part that controls these motors can be configured by software, and control calculations are performed for each control sample.

Speed command selection section 16, the position of the member for driving the motor 21 reaches a predetermined position close to the controlled object the pushing, to enable the control mode automatic switching in response to a control mode automatic switching signal C _MS. That is, the position control mode and the torque control mode can be automatically switched.
Speed command selection section 16 compares the speed command S _CL after limiting the speed command S _C from the position controller.
The value of the speed command S _C from the position controller is when the value is greater than the speed command S _CL after restriction selects the value of the speed command S _C from the position controller.

On the other hand, the value of the speed command S _C from the position controller is in the case of less than the value S _CL velocity command after restriction, motor speed S _MC is determined by selecting the value of the limiting after the speed command S _CL.

Speed controller 15 selects the speed command after restricted speed command selection section 16, the speed command S _TC based on the torque command T _C if not the speed limit at the speed limiting unit 5, the proportional control is performed ..
On the other hand, when the speed command _STC based on the torque command is speed-limited by the speed limiting unit 5, proportional integration control is performed.

When the speed command selection command _STS is the speed command S _CL after the limit, the control mode switching unit 7 _{selects the speed command S CL} after the limit, and torque control with the speed limit function is performed as follows. NS.
The speed controller 15 is constituted by a proportional controller 15a, when the gain and GP, by back calculation of calculation for calculating a motor torque command T _MT from motor speed S _MC of the speed control system, torque from the torque command T _{C The speed command STC} based on the command can be calculated as follows.

Speed based on the torque command deviation _{S DT} = torque command _T C / GP (1)
Speed command based on torque command S _TC = Speed deviation based on torque command S _DT + speed V (2)

Then, a speed limit based on the speed limiting command S _LC relative speed command S _TC based on the torque command obtained, obtains a speed command S _CL after restriction.
When the speed of the motor 21 is controlled according to _{the speed command SCL after the limitation, the result is as follows.}
Motor torque command T _MT = speed deviation S _D x GP = (motor speed command S _MC -speed V) x GP

Here, if the speed limit is not applied, the motor speed command S _{MC = the speed command STC} based on the torque command, so
Motor torque command T _MT = (speed command S _TC based on torque command-speed V) x GP = {(speed deviation S _DT + speed V based on torque command) -speed V} x GP (3)
Here, (speed deviation based on a torque command _{S DT)} × GP = torque command / GP × GP = torque command _{T C,} and the motor torque command _{T MT} coincides with the torque command _{T C,} this motor torque command _{T MT} performs torque control based, motor torque of the motor torque command T _MT as is output from the motor 21.
If applied to the speed limit, the motor speed command S _MC becomes rate limiting command S _LC, the speed control of the motor based on the speed limiting command S _LC is performed, the speed is proportional integral control to the speed limiting command S _LC ..

FIG. 3 is a diagram showing an example of simulation results in the case where the position control according to the present embodiment moves to the front of contact with the pressurization target and switches to torque control to perform the pressurization operation (A to G). Here, as an example, a form when used for a spot welding servo gun is shown.

Waveform A is a diagram showing _{a speed command STC} from a position controller.
The waveform B is _{a diagram showing a torque command TC} and a load torque.
Waveform C is a diagram showing automatic switching of control (position, torque) modes.
The waveform D is a diagram showing _{the speed command SCL after the restriction.}
Waveform E is a diagram showing a motor speed _{S MC.}
The waveform F is a diagram showing the velocity V.
The waveform G is a diagram showing a _{motor torque command TMC.}

In position control, the position of the servo gun approaches the pressurization target, control mode automatic switching is enabled (waveform C), the speed command from the position controller S _{TC (waveform} A) the rate of post-limiting command S _CL ( When the waveform D) or less, the speed command selection unit 16 selects the speed command S _CL after the limit, and the motor speed command S _MC becomes the speed limit value (300 min ^-1 ) set by the speed limit command S _LC. (See 0.12-0.14 of waveform E).

Then, when the object is approached at a limited speed and comes into contact with the object to be pressurized, the load torque increases (waveform B) and the speed decreases (waveform F), the speed limiting state is released, and the torque command T is released. and pressurized subject pressurized with a motor torque command T _MT of _C Street (waveform G).
Pressurizing the object to be pressurized disables automatic control mode switching (waveform C). _{Since there is no pressure control loop, the speed command SLC} (waveform D) after the limit, which is the output from the torque control system with the speed limit function, is a constant and clean value, and the switching from position control to torque control is fast and smooth. (Waveform G). Further, even when the speed limit state is switched to the torque control when the pressure target is contacted, an unstable phenomenon such as chattering is not observed, and the torque control is instantly switched to the torque control (waveform G).

As described above, in the present invention, the normal position control is performed until the motor approaches the pressing control target, and when the motor approaches the pressing control target, the control mode automatic switching is enabled. When the automatic control mode switching is enabled, the speed command selection unit compares the speed command from the position controller with the speed command after the limit. When the speed command from the position controller becomes less than or equal to the speed command after the limit, the speed command after the limit is selected and torque control with the speed limit function is performed. Since there is no pressure control loop in the present invention, switching is fast and smooth, and after switching, it operates at a speed limit value until it comes into contact with a pressurized object. When it comes into contact with the pressurized object, the speed decreases and the speed limit state is released. Then, the motor torque command is obtained according to the torque command, and the object to be pressurized is pressurized by the torque command. Switching from the speed limit state to the torque control state is also fast and smooth because there is no pressure control loop, and the torque control with the speed limit function of this control method automatically switches. A torque control system with a speed limiting function only limits the speed by adding the speed to the speed deviation based on the torque command. Therefore, there is no pressure control loop above the speed control loop to achieve speed limitation, and no special control parameters are required. Even if the gain of the speed controller is low, the motor torque command is calculated according to the torque command when the speed limit is not applied, and the gain of the speed controller is not affected. The gain of the speed controller may be adjusted so that the speed loop is stable when the speed of the motor is normally controlled. Further, if the mechanical system has resonance or the like, a notch filter or a low-pass filter may be provided at the output of the speed controller. In that case, the response to the torque command is reduced by the amount of the filter added.

As described above, in the present invention, the speed command based on the torque command is calculated based on the torque command, the speed is limited to obtain the speed command after the limit, and the speed command from the position controller and the speed command after the limit are obtained. If the speed command from the position controller is larger than the speed command after restriction, select the speed command from the position controller. When the speed command from the position controller becomes equal to or less than the speed command after the limit, the speed command after the limit is selected, the motor speed command is obtained, and the pressing control is realized. As a result, no pressure detector or force detector is required, the transition from position control and speed control to torque control with speed limiting function is fast, and the transition from speed limiting state to torque control is fast and stable pressing. A control device for a control motor can be provided.

Each of the above-described aspects shows one aspect of the present invention, and the present invention itself is not limited to the specific configuration indicated by those aspects. The scope of the present invention includes all that can be assumed by those skilled in the art based on the matters described in the claims.

A Motor control device P Position V Speed 1 Speed deviation calculator 3 Adder 5 Speed limit unit 7 Control mode switching unit 11 Subtractor 15 Speed controller 15a Proportional controller 15a-1 Proportional gain 15b Integral controller 15b-2 Integrator speed command _{S TSS} speed of 15b-3 attenuation gain 15b-4 selector switch 16 speed command selector 17 motor torque controller 21 motor 23 encoder 35 position controller _{L C} position command _{P DT} position deviation _{S C} speed command _{S CL} limit after controller control signal _{S D} speed deviation _S speed deviation _DT-based torque command _{S LC} speed limiting command _{S TC} speed command based on the torque command _{S TS} speed control device control signal _{S MC} motor speed _{T C} torque command _{T MT} motor torque command

Claims (3)

In a motor control device that controls a motor based on either a torque or position control mode command, the position of the motor is controlled according to the position command in the position control mode, and the speed limit command or higher is performed in the torque control mode. It is a motor control device that limits the speed according to the speed limit command and controls the torque of the motor according to the torque command at a speed lower than the speed limit command.
The motor control device is
A speed detection unit that detects the speed of the motor,
A subtractor that subtracts the position from the position command to obtain the position deviation,
A position controller that obtains a speed command based on the position deviation,
A speed deviation calculator that calculates the speed deviation based on the torque command, and
An adder that adds the speed deviation and speed based on the torque command to obtain the speed command based on the torque command,
A speed limiter that limits the speed command based on the torque command based on the speed limit command and outputs the speed command after the limit,
Based on the control mode automatic switching signal, the speed command selection unit that switches between the speed command from the position controller and the speed command after the limitation and outputs the motor speed command,
A subtractor that subtracts the speed of the motor from the motor speed command and outputs the speed deviation.
A speed controller that performs speed control calculations using the speed deviation as an input and outputs a motor torque command.
A motor torque control unit that outputs torque based on the motor torque command is provided.
The speed controller includes a proportional controller and an integral controller.
The speed command selection unit
The speed command from the position controller is compared with the speed command after the limitation based on the torque command, and if the value of the speed command from the position controller is larger than the value of the speed command after the limitation, the position Select the value of the speed command from the controller, and if the value of the speed command from the position controller is equal to or less than the value of the speed command after the limitation, select the value of the speed command after the limitation and the motor speed. A motor control device for which a command is required. The motor control device according to claim 1, wherein the speed command selection unit enables automatic control mode switching when the position of a member driven by the motor reaches a predetermined position close to the pressing control target. The speed controller
The speed command after the limitation is selected by the speed command selection unit, and the speed command is selected.
When the speed command based on the torque command is not speed-limited in the speed limit unit, proportional control is performed.
The motor control device according to claim 1 or 2, wherein when the speed command based on the torque command is speed-limited in the speed limiting unit, proportional integration control is performed.

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