JPH10337070A - Speed controller of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the labor of adjusting a speed control system by coupling a motor and a machine system actually on the site. SOLUTION: This device is equipped with a P adjuster 4 which operates to zero the deviation between a speed command value and a speed detected value, a torque estimator P which estimates the torque, based on the torque command value and the speed detected value, and an adder 5 which gets the torque command value by adding the output of the P adjuster 4 and the torque estimated value. The torque estimator 6 has a model 10 geared to a motor and machine system 2, a controller 9 which outputs a torque estimate from the deviation between the speed detected value and the speed estimate outputted from the model 10, and an adder 8 which gets the deviation between the value equivalent to torque and the torque estimate and inputs it into the model 10. The apparent inertial moment J of the motor and machine system 2 is made to conform to the time constant Jr of the torque estimator 6 in a wide frequency range, by enlarging the parameters of the controller 8 based on the time constant of the torque estimator, the gain, and the sampling time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control device for controlling the rotation speed of a motor connected to a mechanical system in a closed loop with respect to a speed command value.

[0002]

2. Description of the Related Art FIG. 4 shows a block diagram of this kind of speed control device. The speed control system shown in FIG. 1 uses the output of a PI (proportional / integral) adjuster that operates by inputting a deviation between a speed command value of a motor and a detected speed value so that the difference becomes zero, and uses the output as a torque command value. 1 means that the transfer function is K _{P
(1 + 1 / T i s} ) PI regulator represented by, the 2 1 / J
An electric motor / mechanical system 3 indicated by s is an adder for calculating a deviation between a speed command value and a detected speed value of the electric motor. Note that K
_P is a proportional gain of the PI regulator 1, T _i is the integral time, J is the sum of the inertia moment of the motor-mechanical system 2, s is a Laplace operator.

[0003]

In the prior art described above, in order to obtain a desired speed control response, it is necessary to locally adjust the proportional gain K _P and the integration time T _i of the PI controller 1. For example, the cutoff frequency ω _c of the open loop transfer function of the speed control system is set to 20 [ra
d / sec], it is necessary to set the proportional gain K _P = Jω _c = 20 J with respect to the value of the moment of inertia J.

However, since the actual moment of inertia J of the actual motor / mechanical system 2 is often different from the design value, the moment of inertia is actually measured by connecting the motor and the mechanical system at the time of on-site adjustment. Therefore, a complicated procedure of determining and adjusting the proportional gain K _P has to be performed, and the trouble of the adjustment and the variation by the adjuster have become a problem.

Accordingly, the present invention provides a complicated adjustment work in a state where a motor and a mechanical system are connected on site by making the moment of inertia J of the motor / mechanical system independent of the response of the speed control system. It is an object of the present invention to provide a motor speed control device which does not require a motor.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a motor for performing closed-loop control so that a detected speed value of a motor connected to a mechanical system matches a speed command value. A detection device that adjusts the deviation between the speed command value and the speed detection value to zero, based on a torque equivalent value (torque command value or torque detection value) of the motor and the speed detection value; A torque estimating means for estimating the torque of the electric motor, and an adding means for obtaining a torque command value by adding an output of the adjusting means and a torque estimated value output from the torque estimating means, wherein the torque estimating means comprises: A model corresponding to an electric motor / mechanical system, a controller that outputs a torque estimated value by using a deviation between the detected speed value and a speed estimated value output from the model as an input, and a torque corresponding to the torque. And a deviation between the torque estimated value output from the controller and those having a means for inputting into the model.

According to a second aspect of the present invention, the parameters of the controller based on the time constant, gain, and sampling time of the torque estimating means are increased, so that the apparent inertia of the motor / mechanical system in a wide frequency range. If the moment matches the time constant of the torque estimating means, model matching from a low frequency becomes possible.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Although the following embodiment is for driving an AC motor, the present invention is similarly applicable to a DC motor. First, FIG. 1 is a block diagram of a speed control system according to the present embodiment.

In FIG. 1, a deviation between a speed command value of a motor and a detected speed value is obtained by an adder 3. This deviation is input to the P (proportional) controller 4 of the proportional gain K _P ,
The output and a torque estimated value which is an output of the torque estimator 6 described later are added by the adder 5 to obtain a torque command value. This torque command value is given to the electric motor / mechanical system 2. The torque estimator 6 receives the torque command value of the electric motor and the detected speed value and outputs a torque estimated value. With the above configuration, the torque estimator 6 calculates the sum of the output of the P adjuster 4 and the output of the torque estimator 6. The speed control system that sets the torque command value is configured with a closed loop.

[0010] torque estimator 6 obtains the torque estimator transfer function 1 / J _P s the speed estimation value and the deviation adder 7 between the speed detection value after the model 10 corresponding to the motor-mechanical system 2, the The result is input to the controller 9. The controller 9 inputs the estimated torque value output via the parameter L to the adder 5. Also, a deviation between the torque command value output from the adder 5 and the estimated torque value is obtained by the adder 8, and this deviation is determined by the torque estimator model 1
Input to 0. Where J _P is the torque estimator time constant,
L is a parameter represented by _{L = -J P · G T /} Δt, the G _T torque estimator gains ranging from 0 to 2, Delta] t is the sampling time.

In this speed control system, an equivalent block diagram when the speed detection value is viewed from the output of the P adjuster 4 is as shown in FIG. Equivalent transfer function G (s) in FIG.
Can be represented by Equation 1.

[0012]

G (s) = {(1 + σ _a s) / (1 + σ _b s)}
(1 / J _P s)

Σ _a and σ _b are time elements, and ω <1
In the frequency range of / σ _a , ω <1 / σ _b , the apparent moment of inertia J of the electric motor / mechanical system 2 becomes the torque estimator time constant J _P. That is, the electric motor / mechanical system 2 corresponds to the torque estimator model 10. Here, σ _a and σ _b are represented by Expressions 2 and 3, and the controller 9 represented by the parameter L sets the deviation between the detected speed value of the electric motor and the output of the torque estimator model 10 to zero. It is a working controller. By making this parameter L as large as possible, model matching can be achieved in a wider frequency range.

[0014]

## EQU2 ## σ _a = J _P / L

[0015]

Σ _b = J / L

In this embodiment, the torque estimator time constant J
_P is fixed, and the parameter L of the controller 9 (= −J _P
G _T / Δt) is made as large as possible to reduce the time elements σ _a , σ _b , so that the motor
The moment of inertia J of the apparent mechanical system 2 performs a model matching to time constant J _P torque estimator.

For example, the sampling time Δ of the speed control system
When t is 5 [msec] and the moment of inertia J of the electric motor / mechanical system 2 is 2 [sec], J _P = 500 [msec]
c], G _T = 1, σ _a = 5 [msec], σ _b = 20 [m
sec], and the apparent moment of inertia of the electric motor / mechanical system 2 can be regarded as J _P = 500 [msec] in a frequency range of approximately ω <50 [rad / sec]. In the present embodiment, since the speed control system can be adjusted by setting the proportional gain K _P of the P adjuster 4 according to the inertia moment of the load, the actual motor / mechanical system 2 can be adjusted.
, A desired speed control system response can be obtained.

For the torque estimator time constant J _P , the proportional gain K _P of the P adjuster 4 is set as follows.
In the above-described example, the gain characteristic from the output of the P adjuster 4 to the detected speed value of the motor is expressed as 1 / σ as shown in FIG.
_The gain curve is bent at the frequency _b . A frequency equal to or less than の of this frequency is defined as a cutoff frequency ω _c of the open loop transfer function of the speed control system. That is, the response frequency of the speed control system is expressed by Expression 4, and the proportional gain K _P of the P adjuster 4 is expressed by Expression 5.

[0019]

[Equation 4] ω _c ≦ 1 / 2σ _b

[0020]

[Expression 5] K _P ≦ J _P / 2σ _b

In the above numerical examples, ω _c ≦ 25 [rad / sec] and K _P ≦ 12.5 from Expressions 4 and 5.

In FIG. 1, the controller which receives the deviation between the speed command value and the detected speed value of the motor may be a PI controller as shown in FIG.

[0023]

As described above, according to the present invention, since the adjustment of the speed control system can be performed independently of the inertia moment of the motor / mechanical system, the adjustment can be performed while the motor and the mechanical system are actually connected. Can be eliminated, and labor and time for on-site adjustment work can be reduced, and variations due to coordinators can be eliminated. Actually, in the present invention, J = 0.5 to 3 [se
c], the cut-off frequency ω of the open-loop transfer function while keeping the set values of the torque estimator and the P regulator the same
_c can be set to 20 [rad / sec],
Ω _c = 20 for a motor / mechanical system of J = 2 [sec]
There is a track record of [rad / sec].

[Brief description of the drawings]

FIG. 1 is a block diagram of a speed control system according to an embodiment of the present invention.

FIG. 2 is an equivalent block diagram when a speed detection value is viewed from an output of a P adjuster in FIG. 1;

FIG. 3 is a gain characteristic diagram of the embodiment of FIG. 1;

FIG. 4 is a block diagram of a speed control system showing a conventional technique.

[Explanation of symbols]

 2 Electric motor / mechanical system 3, 5, 7, 8 Adder 4 P adjuster 6 Torque estimator 9 Controller 10 Torque estimator model

Claims (2)

[Claims] 1. A speed detecting device for a motor, which is controlled in a closed loop so that a detected speed value of a motor connected to a mechanical system matches a speed command value, wherein a deviation between the speed command value and the detected speed value is made zero. Adjusting means operating as described above, a torque estimating means for estimating the torque of the electric motor based on the torque equivalent value of the electric motor and the speed detection value, and an output of the adjusting means and an estimated torque value outputted from the torque estimating means. And an adder for obtaining a torque command value by adding the following.The torque estimator includes: a model corresponding to an electric motor / mechanical system; and a deviation between the detected speed value and the estimated speed value output from the model. A controller that outputs a torque estimated value as an input; and a unit that obtains a deviation between the torque equivalent value and a torque estimated value output from the controller and inputs the deviation to the model. A speed control device for an electric motor, comprising: 2. The motor / mechanical system according to claim 1, wherein parameters of the controller based on a time constant, a gain, and a sampling time of the torque estimating means are increased, so that the motor / mechanical system appears in a wide frequency range. A speed control device for an electric motor, wherein the upper moment of inertia is made to coincide with a time constant of a torque estimating means.