Motor control device and control method for a motor

Abstract

The present invention provides a motor control device and a control method, which control the torque of a motor while restricting the speed based on a torque command and a speed limit command. The device includes: a speed detection unit that detects the speed of the motor; and a speed limit unit that calculates a speed command based on the torque command and outputs a motor speed command obtained by imposing a limit on the speed command based on the torque command. The speed limit unit includes: a speed command calculation unit that calculates a speed command based on the torque command; and a speed limiter that imposes a speed limit based on the speed limit command on the speed command based on the torque command and outputs the motor speed command. The speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the speed deviation to the speed and outputs a speed command based on the torque command.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of Japanese Patent Application No. 2019 - 238211, filed with the Japan Patent Office on December 27, 2019, the entire content of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a motor control device and a control method, which control the torque of a motor while restricting the motor speed based on a torque command and a speed limit command. Background art

[0004] In the manufacture of paper, sheet bodies, etc., in order to avoid wrinkles, sagging, etc. and improve quality, a tension control device is used for manufacturing. In the control of the pay - out motor of such a tension control device, the pay - out motor is driven with a fixed torque corresponding to the coil diameter to keep the tension fixed.

[0005] Then, in order to suppress the speed increase of the pay - out motor in the case where the workpiece is cut, torque control with a speed limit function is implemented. In addition, in the case of a spot - welding servo gun, the workpiece is clamped by the welding pieces of the electrode part of the gun and the torque of the motor is controlled to apply pressure, and the workpiece is welded by passing an electric current between the electrode pieces.

[0006] In such a welding gun, also before moving to just before contacting the pressurization object by position control and speed control, in order to avoid excessive speed when switching to torque control and colliding with the pressurization object, torque control with a speed limit function is implemented.

[0007] As an example of implementing torque control with such a speed limit function, there is Japanese Unexamined Patent Application Publication No. 2003 - 33068.

[0008] In Japanese Unexamined Patent Application Publication No. 2003 - 33068, a motor control device for controlling a motor based on an external input is disclosed, which includes: a motor that rotates based on an applied voltage; a magnetic pole position sensor that detects the magnetic pole position of the motor; a speed calculation unit that calculates the rotational speed of the motor based on the position signal output by the magnetic pole position sensor; a conversion unit that converts an external input into a torque current command; a torque current correction unit that corrects the torque current command based on the limit rotational speed of the motor and the rotational speed of the motor calculated by the speed calculation unit; a vector calculation unit that calculates a voltage command using the corrected torque current command; and an applied voltage production unit that produces an applied voltage to be applied to the motor based on the voltage command.

[0009] However, in such a method of correcting the torque command by the output of the torque current correction unit, the following problems exist: when speed limiting, it is necessary to output torque current correction for canceling the torque command. When the torque command is large, the cancellation signal also becomes large, resulting in slow response, which in turn leads to large overshoot of speed; when operating near the speed limit, the ON / OFF of speed limit control is performed, so large overshoots occur repeatedly, making the operation unstable; only one speed limit command can be input, so the speed can only be limited in the direction of the torque command; since the direction is uncertain when the torque command is 0, the speed cannot be limited.

[0010] As an example that overcomes the problems of being able to limit the speed only in the direction of the torque command and being unable to limit the speed due to the uncertain direction when the torque command is 0, there is International Publication No. 2011 / 145366.

[0011] International Publication No. 2011 / 145366 discloses a motor control device that controls a motor driving a driven object, presses the driven object against a pressurized object with a pressure corresponding to a target torque, and is characterized by comprising: a speed controller that calculates a torque command for the motor and a return torque for compensating the torque command based on a speed detection value of the motor; and a return torque controller that calculates a first speed command corresponding to a deviation between the target torque and the return torque calculated by the speed controller. The return torque controller limits the calculated first speed command with a desired speed limit value determined based on the contact speed between the driven object and the pressurized object and outputs it. The speed controller calculates the torque command in such a way that the speed detection value follows the first speed command output by the return torque controller.

[0012] In the method of International Publication No. 2011 / 145366, speed limit values can be set for both the forward rotation side and the reverse rotation side of the motor, and the speed can be limited regardless of the polarity of the torque command. Therefore, the problems of being able to limit the speed only in the direction of the torque command and being unable to limit the speed due to the uncertain direction when the torque command is 0 are overcome. However, in such a method of comparing the torque command with the return torque and calculating the speed command through the return torque controller to compensate the torque command for the motor (motor torque command), if the gain of the return torque controller is not made high enough, a motor torque command like the torque command cannot be generated.

[0013] However, the return torque control loop is composed of two controllers, namely a speed controller composed of a proportional-integral controller and a return torque controller also composed of a proportional-integral controller. Since the integral element enters doubly, the control system is prone to become unstable. If the control gain is increased, the return torque vibrates. If the return torque vibrates, the motor torque command also vibrates. Therefore, there is a problem that the gain cannot be increased for use, and only a motor torque slightly smaller than the torque command can be output.

[0014] In particular, the following problems occur: if the proportional gain of the regenerative torque controller is increased, vibration is likely to occur, so the proportional gain cannot be increased for use. Therefore, depending on the control parameters, the recovery from the speed limit state sometimes cannot operate properly, making adjustment difficult. As a result, the parameter range for stable operation is narrow.

[0015] In addition, the integrator of the speed controller also acts as the integrator of the regenerative torque controller. Therefore, when the torque command changes abruptly, the integrator of the speed controller also acts. As a result, the following problems occur: the overshoot of the speed is large; when operating near the speed limit, the ON / OFF of the speed limit control is performed, so large overshoots occur repeatedly, making the operation unstable. Summary of the Invention

[0016] The present invention is proposed to overcome the above problems, and its object is to provide a motor control device and a motor control method that are easy to adjust control parameters, can limit the speed in torque control regardless of the polarity of the torque command or the rotation direction of the motor, have a small overshoot during speed limit, and can output the motor torque according to the torque command without involving speed limit.

[0017] The motor control device of the present invention is as described below.

[0018] A motor control device controls the torque of a motor while limiting the speed based on a torque command and a speed limit command. The motor control device is characterized in that it has: a speed detection unit that detects the speed of the motor; and a speed limit unit that calculates a speed command based on the torque command and outputs a motor speed command obtained by imposing a limit on the speed command based on the torque command. The speed limit unit includes: a speed command calculation unit that calculates a speed command based on the torque command; and a speed limiter that imposes a speed limit based on the speed limit command on the speed command based on the torque command and outputs the motor speed command. The speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the speed deviation to the speed and outputs the speed command based on the torque command.

[0019] In addition, the present invention also includes the following motor control method.

[0020] A motor control method controls the torque of a motor while limiting the speed based on a torque command and a speed limit command. It is characterized in that a speed deviation is calculated based on the torque command, a speed command based on the torque command is output by adding the speed deviation to the speed of the motor, and a speed limit based on the speed limit command is imposed on the speed command based on the torque command to output a motor speed command.

[0021] Embodiments of such a motor control device and motor control method of the present invention can be implemented in various ways as shown in the dependent claims of the claims. Each embodiment, as well as other details and advantages, will be described in detail in the specific embodiments described later.

[0022] According to the above configuration, in the present invention, speed limitation in torque control can be achieved through the following simple configuration: In a method of inverse operation of calculating a motor torque command based on a motor speed command in a speed control loop, a speed command based on the torque command is calculated based on the torque command, speed limitation is performed to obtain a motor speed command, and the motor is speed-controlled based on the motor speed command. Therefore, a control device for a motor can be realized, which does not require special parameter adjustment, can limit the speed regardless of the polarity of the torque command or the rotation direction of the motor, has small overshoot during speed limitation, and can output a motor torque as per the torque command without involving speed limitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a block diagram showing one mode of a motor control device and method.

[0024] Figure 2 is a block diagram showing other modes of a motor control device and method.

[0025] Figure 3 is a graph showing the simulation result of speed change of one mode (speed proportional control) of a motor control device and method.

[0026] Figure 4 is a graph showing the simulation result of speed change of other modes (speed proportional integral control) of a motor control and its method.

[0027] Figure 5 is a graph showing the simulation result of speed change of an operation example of a mode for correcting a torque command. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] 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 will 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.

[0029] Hereinafter, embodiments of a motor control device and method according to the present invention will be described in detail with reference to the accompanying drawings. In addition, the scope of the present invention is not limited by the description of this embodiment, and any mode is included in the scope of the present invention as long as it belongs to the technical scope of the invention related to each claim of the claims.

[0030] Figure 1 One mode of the motor control device and method is shown.

[0031] A motor control device A for controlling the motor torque T of a motor M of the present invention generally includes: an encoder EN for obtaining the motor speed S, a differentiator Dif, a speed deviation calculator 1, an adder 2, a subtractor 3, a speed limiter 4, a speed controller 5, a motor torque controller 6, and the like.

[0032] Here, both the encoder EN and the differentiator Dif for obtaining the motor speed S constitute a speed detection unit B for detecting the motor speed S. In addition, the components of the speed detection unit B do not have to be only composed of the encoder EN and the differentiator Dif, and can be arbitrary as long as they can detect the speed.

[0033] In addition, the speed deviation calculator 1 and the adder 2 constitute a speed command calculation unit C based on the torque command, and the speed command calculation unit C based on the torque command and the speed limiter 4 constitute a speed limit unit D.

[0034] In the motor control device A configured in this way, a torque command Tc for controlling the motor torque T of the motor M and a speed limit command Suc for limiting the motor speed S of the motor M are provided from the outside, and the motor M is operated under the desired torque and a certain speed limit.

[0035] The desired torque command Tc provided from the outside is input to the speed deviation calculator 1, and the speed deviation Sd1 based on the torque command Tc is calculated and output.

[0036] In the adder 2, the speed deviation Sd1 based on the torque command Tc is added to the motor speed S output from the speed detection unit B, and the speed command Sc based on the torque command is output. The speed command Sc based on the torque command is input to the speed limiter 4, where speed limiting is performed based on the desired speed limit command Suc provided from the outside, and the motor speed command Smc is calculated. The motor M is speed-controlled based on the motor speed command Smc.

[0037] Specifically, the differentiator Dif differentiates the position signal sent from the encoder EN installed in the motor M to obtain the motor speed S. The speed deviation Sd2 signal output by subtracting the motor speed S from the motor speed command Smc in the subtractor 3 is input to the speed controller 5, and the speed controller 5 calculates the motor torque command Tmc. Based on the motor torque command Tmc, the motor torque T corresponding to the motor torque command Tmc is output from the motor M through the motor torque controller 6. The position after rotation according to the motor torque T output from the motor M is detected by the encoder EN, and a speed control loop is formed to be consistent with the motor speed command Smc.

[0038] When the speed controller 5 is constituted by a proportional controller and its gain is set to G, the operation of the speed control loop is performed based on the following formulas (1) and (2).

[0039] Motor speed command Smc - Motor speed S = Speed deviation Sd2...(1)

[0040] Speed deviation Sd2 × Gain G of the proportional controller = Motor torque command Tmc...(2)

[0041] Through the two formulas, the inverse operation can be performed as follows to obtain the motor speed command Smc from the motor torque command Tmc.

[0042] Speed deviation Sd2 = Motor torque command Tmc / Gain G of the proportional controller...(3)

[0043] Motor speed command Smc = Speed deviation Sd2 + Motor speed S...(4)

[0044] In the present invention, for the torque command Tc provided from the outside, using the relationships of the following formulas (5) and (6), first, the speed command Sc based on the torque command is calculated.

[0045] Speed deviation Sd1 based on the torque command = Torque command Tc / G...(5)

[0046] Speed command Sc based on the torque command = Speed deviation Sd1 based on the torque command + Motor speed S...(6)

[0047] Then, for the speed command Sc based on the torque command obtained, speed limiting is performed in the speed limiter 4 based on the speed limit command Suc, and the motor speed command Smc is obtained.

[0048] If speed control of the motor is performed based on this motor speed command Smc, then:

[0049] Motor torque command Tmc = speed deviation Sd2 × G

[0050] =(motor speed command Smc - motor speed S) × G

[0051] Here, in the case where speed limiting is not involved, that is, when the speed command Sc based on the torque command is smaller than the speed limit command Suc, the motor speed command Smc = the speed command Sc based on the torque command. Therefore,

[0052] Motor torque command Tmc = (speed command Sc based on the torque command - motor speed S) × G

[0053] ={(speed deviation Sd1 based on the torque command + motor speed S)

[0054] - motor speed S} × G

[0055] =(speed deviation Sd1 based on the torque command) × G

[0056] = torque command Tc / G × G

[0057] = torque command Tc

[0058] The motor torque command Tmc coincides with the torque command Tc, and torque control of the motor M is performed based on this motor torque command Tmc, and the motor torque T according to the motor torque command Tmc, that is, the torque command Tc, is output from the motor M.

[0059] In the case where speed limiting is involved, that is, when the speed command Sc based on the torque command is greater than or equal to the speed limit command Suc, the motor speed command Smc becomes the speed limit command Suc, and speed control of the motor M based on the speed limit command Suc is performed. Only the speed deviation Sd1 based on the torque command is added to the motor speed S for speed limiting. Therefore, there is no torque control loop for implementing speed limiting at the upper level of the speed control loop, and no special control parameters for constructing the control loop are required.

[0060] In addition, the speed limit command Suc can limit both the CW (clockwise rotation direction) side and the CCW (counterclockwise rotation direction) side through one input, or two speed limit commands can be set to independently limit the CW side and the CCW side.

[0061] In addition, the speed limit instruction Suc can determine the upper limit of the motor speed S based on a predetermined threshold value, a predetermined table value, a predetermined function value, etc. In this case, the so-called "prescribed" naturally includes what can be determined arbitrarily, and also includes what can be set arbitrarily at a certain time such as when the motor control device A is manufactured, tested, shipped, or used.

[0062] As described above, in the present invention, the motor torque command Tmc is calculated based on the motor speed command Smc in the speed control system by performing the inverse operation, the speed command Sc based on the torque command is calculated based on the torque command Tc, the motor speed command Smc is obtained by performing speed limitation, and the motor torque command Tmc is calculated based on the motor speed command Smc.

[0063] In addition, when the gain G of the speed controller 5 is low, when there is no speed limit involved, the motor torque command Tmc is calculated according to the torque command Tc, and is not affected by the gain G of the proportional controller of the speed controller 5. When the motor M is speed-controlled in a normal operating state, the gain G of the speed controller 5 can be adjusted in a normal manner so that the speed loop is stable.

[0064] exist Figure 2 Other embodiments of the motor control device and method are shown in FIG.

[0065] In this method, Figure 1 In the motor control device and method shown, when resonance occurs in the motor M or the mechanical system such as the shaft or winding device connected thereto, a filter such as a notch filter NF or a low-pass filter LPF can be provided on the output side of the speed controller 5. In this case, the response to the torque command Tc is reduced by an amount corresponding to the addition of the filter such as the low-pass filter LPF. The other configurations are the same as those of the first embodiment described above.

[0066] When the speed controller 5 is constituted by a proportional controller, there is no overshoot. In the case where the workpiece is cut during tension control by the motor M, there is only rotational friction of the unwinding part, so the load torque is small, and even in proportional control, the error that occurs at the limited motor speed is small.

[0067] Two methods are described above. However, according to the application of the present invention, the load torque Tb of the load is large, and a speed error of the load torque Tb divided by the speed control gain G may occur with respect to the speed limit command Suc.

[0068] In this case, a speed controller 5 is constituted by a proportional-integral controller, which operates as a proportional controller when not involving speed limit and makes the integral controller effective when involving speed limit. When involving speed limit, the influence of the load torque Tb is suppressed by the integral controller. However, the value output from the integral controller is only the value for compensating the amount of the load torque Tb, the compensation amount of the integral controller is minute, and the overshoot of the motor speed is also minute.

[0069] In addition, when the load torque Tb is large and a regeneration operation is performed, the integral controller of the proportional-integral controller is turned OFF when speed limit is involved during regeneration. Although a speed error is generated, during regeneration, the integral controller is repeatedly turned ON / OFF, playing a role in avoiding the pulsation of the motor torque T.

[0070] In Figure 3 and Figure 4 simulations of speed changes in multiple modes of motor control and its method are shown. Additionally, in Figure 5 simulation results of speed changes in the operation example of the method for correcting the torque command are shown. In each of the above figures, the vertical axis represents the magnitude of the speed, and the horizontal axis represents the passage of time. They are all curves under the same speed limit command Suc.

[0071] In Figure 3 in one mode of motor control and its method, when the time T satisfies 0 ≤ T ≤ 0.25, the result in the case where the load torque is zero is shown. Within this time range, it appears that the speed is limited according to the setting of the speed limit command Suc. Additionally, in the range of 0.25 ≤ T, the result in the case where the load torque is present is shown. Within this time range, as will be described later, for the speed limit command Suc, a speed error of the amount obtained by dividing the load torque Tb by the gain G of speed control occurs. The example here is just an example, showing an error of 29.4 min−1. During power operation, it is limited in a manner of a lower amount of the error, and during regeneration, it is limited in a manner of a higher amount of the error.

[0072] In skipping one figure Figure 5Among them, as a comparison with the motor control and method, an operation example of the method of the correction torque command disclosed in Japanese Unexamined Patent Application Publication No. 2003-33068 is shown. When the time T satisfies 0≤T≤0.25, the result in the case where the load torque is zero is shown. In addition, in the range of 0.25≤T, the result in the case where the load torque exists is shown. During any power operation, when the speed is rising, large overshoots such as 290 min-1 and 265 min-1 occur. In addition, when the torque command is 0 during regeneration, a situation where the speed is not limited occurs. Since it is a structure that limits the speed by outputting a torque command from the speed loop that only cancels the magnitude of the torque command, there is a time delay until a large cancellation torque command appears, so the overshoot is large.

[0073] In Figure 4 the simulation results of the speed change of another method of motor control and its method are shown. The following operation example is shown in this method: the speed controller is configured to perform proportional-integral control (PI control), and can operate as proportional control (P control) when the speed limit value is not reached, and the integral controller is made effective to perform speed proportional-integral control (PI control) when the speed limit is reached. When the time T satisfies 0≤T≤0.25, the result in the case where the load torque is zero is shown. In this time range, when it comes to speed limit, the integral controller operates, but the torque cancellation is not performed, so the overshoot stays at 30 min-1. In addition, in the range of 0.25≤T, the result in the case where the load torque exists is shown. Even in this time range, when it comes to speed limit, the integral controller operates, so overshoot occurs, but compared with the operation example of the method of the correction torque command shown in Figure 5 the amount of overshoot is quite small.

[0074] As described above, in the method of the present invention, a control device for a motor can be realized in all cases. It does not require special parameter adjustment, can limit the speed regardless of the polarity of the limit torque command or the rotation direction of the motor, has a small overshoot during speed limit, and can output the motor torque according to the torque command when the speed limit is not involved.

[0075] Each of the above methods shows the content of one aspect of the present invention, and the present invention itself is not limited by the specific configurations shown by these methods. The scope of the present invention includes variations that those skilled in the art can conceive based on the matters described in the claims.

[0076] The detailed description has been given for purposes of illustration and example. Many variations and modifications are possible in light of the above teachings. The detailed description is not without omissions or intended to limit the subject matter described herein. Although the subject matter has been described in terms of particular structural features and / or methodological procedures, it is to be understood that the subject matter defined in the claims is not necessarily limited to the specific features or specific procedures described. Rather, the specific features and specific procedures are described as examples for implementing the claims.

Claims

1. A motor control device controls the torque of a motor while limiting the speed based on a torque command and a speed limit command, characterized in that, the motor control device has: a speed detection unit that detects the speed of the motor; and a speed limit unit that calculates a speed command based on the torque command, and outputs a motor speed command obtained by imposing a limit on the speed command based on the torque command, the speed limit unit includes: a speed command calculation unit that calculates a speed command based on the torque command; and a speed limiter that imposes a speed limit based on the speed limit command on the speed command based on the torque command, and outputs the motor speed command, the speed command calculation unit based on the torque command includes: a speed deviation calculator that calculates a speed deviation based on the torque command; and an adder that adds the detected speed of the motor to the speed deviation and outputs a speed command based on the torque command, when the speed command based on the torque command is equal to or higher than the speed limit command, the torque of the motor is controlled according to the speed limit command, when the speed command based on the torque command is smaller than the speed limit command, the torque of the motor is controlled according to the speed command based on the torque command.

2. The motor control device according to claim 1, characterized in that, it further includes a speed controller that calculates a motor torque command based on the motor speed command, the speed deviation calculator outputs the speed deviation based on the torque command according to the following formula, the speed deviation (Sd1) based on the torque command = the torque command (Tc) / the gain (G) of the speed controller.

3. The motor control device according to claim 1 or 2, characterized in that, the speed limit command determines an upper limit of the speed of the motor based on a specified threshold value, a specified table value, or a specified function value.

4. The motor control device according to claim 2, characterized in that, the speed controller has at least one of a proportional controller and a proportional-integral controller.

5. A motor control method controls the torque of a motor while limiting the speed based on a torque command and a speed limit command, characterized in that, a speed deviation is calculated based on the torque command, a speed command based on the torque command is output by adding the detected speed of the motor to the speed deviation, a speed limit based on the speed limit command is imposed on the speed command based on the torque command to output a motor speed command, when the speed command based on the torque command is equal to or higher than the speed limit command, the torque of the motor is controlled according to the speed limit command, when the speed command based on the torque command is smaller than the speed limit command, the torque of the motor is controlled according to the speed command based on the torque command.

6. The motor control method according to claim 5, characterized in that, a motor torque command is further calculated based on the motor speed command by a speed controller, Calculate the speed deviation based on the torque command according to the following formula, The speed deviation (Sd1) based on the torque command = The torque command (Tc) / The gain (G) of the speed controller.

7. The motor control method according to claim 5 or 6, characterized in that, The speed limit command determines the upper limit of the speed of the motor based on a specified threshold value, a specified table value or a specified function value.

8. The motor control method according to claim 6, characterized in that, The speed controller performs proportional control in torque control and proportional-integral control in speed limit.

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