JP2508129B2 - Electric motor controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a device for controlling the speed of an electric motor.

B. SUMMARY OF THE INVENTION The present invention is a device for controlling the speed of an electric motor, in which first and second electric motor simulating means having characteristics equivalent to those of the electric motor are provided, and subtraction output between the addition output of both simulating means and the speed of the electric motor By giving it to the inertia moment estimator and changing the torque constant of the motor according to the output of the inertia moment estimator so that there is no speed deviation from both simulation means, the speed response will be the motor simulation means even if the inertia moment changes. It is designed to be the same as the response determined by.

C. Conventional Technology FIG. 4 shows a block diagram of a control system for controlling the speed of an electric motor using a conventional motor control device. This control system is composed of a control device 200 and a loaded electric motor 2, and performs feedback control of the electric motor speed. The control device 200 has a PI unit 201 as a control element,
The transfer function Gc (S) is expressed by the following equation.

Gc (S) = Kp + Ki / S Here, Kp and Ki are control constants. The speed Wc of the electric motor 2 as the control amount is fed back to the input of the PI unit, and the difference with the speed setting value Ws is calculated and input to the PI unit 201. The PI unit 201 outputs the torque current Itc to the electric motor 2 as a manipulated variable, and the speed Wc
Adjust the motor torque so that is equal to the set value Ws. A disturbance T is generally applied to the electric motor 2.

D. Problems to be Solved by the Invention In the control system using the above-described conventional motor control device, the response characteristic is determined by the control constants Kp and Ki. These values are set so as to obtain desired response characteristics by assuming the moment of inertia of the motor load in advance. The set value is fixed and never changed.

Therefore, when the moment of inertia of the motor load changes, the root of the characteristic equation changes and it becomes impossible to obtain the desired response characteristic. In addition, the control system may become unstable when the moment of inertia changes drastically. In order to describe these matters in more detail, a control block diagram using the transfer function of FIG. 5 will be described. In the control block diagram of FIG. 5, the transfer function G ₁ (S) of the actual speed of the motor with respect to the speed command Ws is expressed by the following equation.

However, Jr is the moment of inertia, and the constant K _{T in} Fig. 5 is Jr.
Think of it as included in.

Ωn (frequency) and ξ (damping coefficient) that determine this response
Is as follows.

Now, the PI gain is determined so that the desired response (ωn, ξ) to the speed command is obtained, but when the moment of inertia changes, ωn, ξ changes, and the desired response cannot be obtained.

E. Means for Solving the Problems The present invention relates to a device for controlling the speed of an electric motor, in which a first electric motor simulating means having characteristics equivalent to those of the electric motor and the speed of the first electric motor simulating means are used as feedback signals. The torque current supplied to the first electric motor simulating means is adjusted so that the speed of the first electric motor simulating means becomes equal to the set speed, and at the same time, the speed control means for supplying the torque current to the electric motor, the sine wave signal and the cosine. Signal generating means for generating a wave signal, second electric motor simulation means to which the sine wave signal generated by the signal generating means is supplied, and the first and second
The outputs of the electric motor simulating means are added, the speed difference between the added output and the electric motor is obtained, and the subtracting means for outputting this as a speed difference signal, and the speed difference signal from the subtracting means,
Compensating means for supplying to the electric motor to output a compensating current for making the speed difference between the electric motor and the first and second electric motor simulating means zero, and supplying the compensating current to the torque current for supplying to the electric motor An adding means, and a torque coefficient changer inserted in an electric path through which the output of the first adding means is supplied to the electric motor;
The second addition means for adding the sine wave signal generated by the signal generation means to the torque current, the cosine wave signal of the signal generation means and the speed difference signal of the subtraction means are input and calculated, and the calculation result is obtained. And an inertia moment estimating means for supplying a coefficient corresponding to the inertia moment to the torque coefficient changer.

F. Action In the motor control device according to the present invention, speed control is performed not for the motor but for the first motor simulating means. That is, the speed controller receives the speed of the first electric motor simulating means as a feedback signal and adjusts the torque current supplied to the first electric motor simulating means so that the speed of the first electric motor simulating means becomes equal to the set speed. A speed difference between the sum of the output of the first electric motor simulating means and the output of the second electric motor simulating means and the speed of the electric motor is given to the moment of inertia estimator. The moment of inertia estimator gives an output to the torque coefficient changer from the cosine wave signal from the signal generator and the above speed difference to change the torque constant of the electric motor so that there is no speed difference between the first and second electric motor simulating means. To do. As a result, the speed response becomes the same as the response determined by the first and second electric motor simulation means.

G. Examples Next, examples of the present invention will be described with reference to the drawings.

 Before going into the explanation, a list of symbols used here is shown.

Ws: Set speed W: Model speed Wr: Motor speed T _L : Load torque J _r : Motor inertia moment J: Model inertia moment e: Speed difference Km: Torque constant In: Random noise current It: Torque current Ix : Compensation current K'p, K'i, K'q, Kr, Ks, Ka: Constant τ: Time constant S: Operator Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the present invention. The block is composed of a control device 1 according to the present invention and a motor 2 under load, and the control device 1 is further composed of the following (a) to (h).

(A) First and second electric motor simulating means (hereinafter, referred to as first and second models) 13a and 13b simulating the electric motor 2 and having characteristics equivalent to the electric motor 2.

(B) A speed at which the torque current It is supplied to the first model 13a and the electric motor 2, the speed W of the first model 13a is received as a feedback signal, and the torque current It is adjusted so that this speed becomes equal to the set speed Ws. Controller 11.

(C) A subtractor 14 for obtaining a difference between the speed Wr of the electric motor 2 and the sum of the speed W of the first model 13a and the output of the second model 13b.

(D) The transfer function is composed of a proportional element and an integral element, and based on the difference between the speed of the electric motor 2 obtained by the subtractor 14 and the sum output of the first and second models 13a, 13b, Speed Wr is 1st, 2nd
A compensator 12 that outputs a compensation current to follow the speed of the models 13a and 13b.

(E) An adder that adds the compensation current output by the compensator 12 to the torque current output by the speed controller 11 and outputs the result to the motor 2.
15.

(F) An inertia moment estimator 16 which outputs an output that changes the torque constant of the electric motor 2 based on the difference output by the subtractor 14 and the cosine wave signal generated by the signal generator 17.

(G) A torque coefficient changer 19 that changes the coefficient by the output of the moment of inertia estimator so that the speed response does not change even if the moment of inertia changes.

(H) An adder 18 that adds the sine wave signal of the signal generator and the torque current and supplies the result to the electric motor 2.

Next, the operation will be described. In this control system, the speed controller 11 controls the speed of the first model 13a. That is, the speed controller 11 receives the speed W of the first model 13a as a feedback signal, and adjusts the torque current It so that the difference between the speed W of the first model 13a and the set speed Ws becomes zero.
Since the same torque current It supplied to the first model 13a is also supplied to the electric motor 2, if the characteristics of the electric motor 2 and the characteristics of the first model 13a are the same, the speed of the electric motor 2 Wr becomes equal to the speed W of the first model 13a, and thus the set speed Ws. However, when the moment of inertia of the load of the electric motor 2 changes or when there is a deviation in the parameter setting in the first model 3a, the characteristic of the electric motor 2 and the characteristic of the first moment 13a differ.

The compensator 12 is provided to match the speed Wr of the electric motor 2 with the speed W of the first model 13a even if such a characteristic mismatch occurs. That is, the compensation current output from the compensator 12 is supplied to the electric motor through the adder 15, and the compensator 12 outputs the speed W of the first model 13a input from the subtractor 14 and the output of the second model 13b described later. The value obtained by subtracting the speed Wr from the output of the sum of and is received, and the compensation current is adjusted so that the difference between the speed Wr and the output of the sum becomes zero.

In the present embodiment, the compensator 12 is not limited to the one whose transfer function is composed of the proportional element and the integral element as described above, and includes, for example, a derivative element according to the required control characteristic. It can be a thing etc.

Next, the sine wave signal (sin ωn
t) is added to the torque current by the adder 18 and supplied to the electric motor 2 and also to the second model 13b. At this time, the moment of inertia of the electric motor 2 is the second model 13
When the moment of inertia of b is different, a difference occurs between the speed Wr of the electric motor and the speed W of the first model 13a and the sum output of the outputs of the second model 13b. The subtractor 14 outputs this difference to the moment of inertia estimator 16. The moment of inertia estimator 16 estimates the difference in the active moment of the electric motor 2 based on this speed difference and the cosine wave signal (cosωnt) from the signal generator 17. Then, an output is sent from the inertia moment estimator 16 based on the estimation result. This output is used to change the coefficient of the torque coefficient changer 19 so that the difference between the inertia moments is eliminated. Thereby, even if the moment of inertia changes, the velocity response becomes the same as the response determined by the second model 13b.

FIG. 2 is a block diagram showing the present embodiment in more detail, in which the constituent elements of FIG. 1 are disassembled into the transmission elements constituting them. The mathematical formula written in each block represents a transfer function. The following is a brief description of FIG.

As shown in FIG. 2, the speed controller 11 includes a transmission element 301.
And a subtraction element 302 for obtaining the difference between the set speed Ws and the speed W of the first model 13a as a feedback signal. The electric motor 2 is composed of transmission elements 303 and 304 and an addition element 305. Correspondingly, the first and second models 13a, 13b consist of transfer elements 306, 307a and 306b, 307b.
The compensator 12 is composed of a transfer element 308, and the moment of inertia estimator 16 has transfer elements 309 and 310 and a multiplication element 311.

Next, referring to FIG. 3, when the moment of inertia changes while driving the motor, the speed response can be sent to the desired response,
The details of compensating for the vibrational condition will be described using mathematical expressions.

 The algorithm of this embodiment is shown below.

FIG. 3 shows the details of the same inertia moment compensation block diagram as in FIG. When the inertia moment Jr of changes, the first and second models There is a deviation (ER) in the speed of and. The deviation at this time is
Equation (7) is obtained from equations (3), (4), (5), and (6). The torque current will be described as IT here.

ER = W + WDD-Wr (3) From equations (3) to (6), Equation (7) is derived and Fourier transformation is performed to obtain equation (8).

Considering now that the frequency ω is ωn, ω = ωn (9) Equation (9) is substituted into Equation (8).

Here, the IT term becomes zero when it is later multiplied by the cosine wave signal and integrated, so it is ignored. Also, for convenience, the coefficient is calculated as the following equation.

At this time, the equation (10) is expressed by the equation (11).

Therefore, when a small signal of sine wave signal sinωnt is input as INX, the deviation ER becomes And take the correlation between the deviation ER and the cosine wave signal cosωnt,
Control so that there is no correlation. Now, in order to investigate the correlation, ER is multiplied by cosωnt and the integrated average is taken.

However, T: cycle time If B is omitted in equation (14), It becomes the formula (15). DC component remains.

From equation (15), C = 0 must be satisfied when the correlation disappears. Therefore, the condition for C = 0 is There are two possibilities.

Now, solving equations (16) and (17) for Kh gives the following equation.

The moment of inertia can be compensated by using Eqs. (18) and (19).

However, although an example is given below in equation (19), since Kh exceeds the limit value, compensation is performed using equation (18).

In the equation (19), if identification is performed with a small signal of 20 Hz, Kh = 20.94 will be exceeded and mil will be exceeded under the condition of ωn = 40π (rad / sec) Ks = 0.01045 Jr = 0.001741. Compensation is performed using equation (18).

H. Effects of the Invention As described above, the difference in the moment of inertia is estimated from the speed deviation between the electric motor and the first and second models, and the torque coefficient changer is changed so that the difference becomes zero. This has the advantage that even if the moment of inertia changes, the velocity response can be the same as the response determined by the first and second models.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are block diagrams showing the same embodiment in detail, FIG. 4 is a block diagram showing a conventional apparatus, and FIG. It is a block diagram which shows a figure by a transfer function. 1 ... Control device, 2 ... Electric motor, 11 ... Speed controller, 12
...... Compensator, 13a, 13b …… First and second electric motor simulation means, 14
…… Subtractor, 15, 18 …… Adder, 16 …… Moment of inertia estimator, 17 …… Signal generator.

Claims (3)

(57) [Claims] 1. An apparatus for controlling the speed of an electric motor, wherein a first electric motor simulating means having characteristics equivalent to those of the electric motor and a speed of the first electric motor simulating means are received as a feedback signal, and the first electric motor simulating means A speed control means for adjusting the torque current supplied to the first electric motor simulating means so that the speed becomes equal to the set speed and at the same time supplying the torque current to the electric motor, and a signal generating means for generating a sine wave signal and a cosine wave signal. A second electric motor simulating means to which a sine wave signal generated by the signal generating means is supplied;
The outputs of the electric motor simulating means are added, a speed difference between the added output and the electric motor is obtained, and a subtracting means for outputting a speed difference signal representing this, and a speed difference signal from the subtracting means,
Compensating means for supplying to the electric motor to output a compensating current for making the speed difference between the electric motor and the first and second electric motor simulating means zero, and supplying the compensating current to the torque current for supplying to the electric motor Adder means, a torque coefficient changer inserted in the electric path through which the output of the first adder means is supplied to the electric motor, and second adder means for adding the sine wave signal generated by the signal generating means to the torque current. , The cosine wave signal of the signal generating means and the speed difference signal of the subtracting means are input and calculated, and the calculation result is averaged to supply the coefficient of inertia to the torque coefficient changer to estimate the moment of inertia And a control unit for an electric motor. 2. The motor control device according to claim 1, wherein the transfer function of the compensation means has a proportional element and an integral element. 3. The control device for an electric motor according to claim 1, wherein the transfer function of the compensation means has a differential element.