JPH10248286A - Speed controller for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow swift response of speed control in a speed controller for a motor to a large-inertial machine system. SOLUTION: The speed controller for the motor conducting closed-loop control so that the speed detecting value of the motor driving a machine system having large inertial is conformed to a speed command value bas a PI regulator 1 operated so that a deviation between the above-mentioned speed command value and the speed detecting value reaches zero, a torque estimating equipment 6 estimating the torque of the motor on the basis of the torque corresponding value of the motor and the above-mentioned speed detecting value, and an adder 5 adding an output from the PI regulator 1 and a value obtained by multiplying a torque estimate output from the torque estimating equipment 6 by k, and an output from the adder 5 is used as the torque command value of the motor. The parameter of the torque estimating equipment 6 is adjusted so that the moment of inertia of the machine system from the output from the PI regulator 1 is reduced apparently.

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 driving a mechanical system having a very large inertia as compared with a motor torque.

[0002]

2. Description of the Related Art Conventionally, the following two methods are mainly used for controlling the speed of a motor for a large inertia system. (1) The first method is a speed control method in which the output of a PI controller, which receives the deviation between the speed command value of the electric motor and the detected speed value, as the torque command value, is shown in FIG. 4. . In FIG. 4, 1 indicates that the transfer function is K _p (1 + 1 / T
PI regulator represented by _i s), 2 is a motor-mechanical system represented by 1 / Js, 3 denotes an adder for obtaining a difference between the speed command value and the speed detection value of the motor. _Kp is a proportional gain, _Ti is an integration time, J is the sum of the moment of inertia of the electric motor and the mechanical system, and s is a Laplace operator.

[0003] (2) A second method is to provide an output of a PI controller that receives a deviation between a speed command value of a motor and a detected speed value and a D controller that receives a speed command value of a motor (incomplete). This is a speed control method in which the sum with the output of the differentiator is used as a torque command value, and FIG. 5 shows a block diagram of the method. That is, as shown in FIG. 5, the transfer function J _D s with respect to the configuration of FIG. 4
An incomplete differentiator 4 represented by / (1 + σ _D s) and an adder 5 for adding its output to a torque command value are added. Note that J _D is a time constant, and σ _D is a delay time.

[0004]

The inertia of the mechanical system is very large, and the moment of inertia J converted to the time required to reach the predetermined speed after operating the motor at the rated torque is 10%.
Is greater than or equal to about seconds, in the conventional first control method, since it is not possible to increase only the restriction of the torque control system of the motor drive apparatus until 50-100 times the proportional gain K _p of the PI controller 1, the speed control response Gets very bad. Usually, the DC motor speed control response is open loop cut-off frequency ω _c = K _p / J~20 [rad / s], the AC motor while from 20 to 100 [rad / s], for example, the mechanical system If the inertia is very large, J = 20 seconds,
Even if K _p = 50, ω _c = 2.5 [rad / s], which is extremely poor. In addition, in the second conventional control method, the responsiveness to the speed command value is improved, but the responsiveness to the speed fluctuation due to disturbance is not different from the first related art.

The present invention has been made to solve the problems of the prior art and to provide a motor speed control device capable of high-speed response.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 is an electric motor that performs closed-loop control so that a detected speed value of an electric motor that drives a mechanical system having a large inertia coincides with a speed command value. In the speed control device, the PI adjusting means that operates to reduce the deviation between the speed command value and the speed detection value to zero, and estimates the torque of the motor based on the torque equivalent value of the motor and the speed detection value. A torque estimating means, and an adding means for adding an output of the PI adjusting means and a value obtained by multiplying the torque estimated value outputted from the torque estimating means by a constant, and outputting the output of the adding means to a torque command value In addition, the parameter of the torque estimating means is adjusted so that the moment of inertia of the mechanical system viewed from the output of the PI adjusting means becomes apparently small. Here, the torque equivalent value of the electric motor described above can be a torque command value for an AC motor and a torque detection value for a DC motor.

According to a second aspect of the present invention, in the motor speed control apparatus according to the first aspect, a detected speed value of the motor is obtained from an output of the PI adjusting means with respect to an apparently small inertia moment of the mechanical system. The integral time and the proportional gain of the PI adjusting means are adjusted based on the gain characteristics described above.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 is a block diagram of a speed control system showing this embodiment, and the same components as those in FIGS. 4 and 5 are denoted by the same reference numerals. In this embodiment, a large inertia mechanical system is driven by an AC motor.

In FIG. 1, a deviation between a speed command value of a motor and a detected speed value is obtained by an adder 3. A speed control system that uses the sum of the output of the PI controller 1 that receives the deviation as an input and the output of the torque estimator 6 that receives the torque command value and the speed detection value of the electric motor as a torque command value in a closed loop It is configured.

A torque estimator 6 obtains a deviation between a speed estimation value via a transfer function 1 / J _ps and a speed detection value by an adder 7, and calculates a torque estimation value output via a parameter L by a constant multiplier. The value is multiplied by K by 9 and input to the adder 5. Also,
Deviation of the torque command value output from the adder 5 and the torque estimated value is calculated by the adder 8, the difference is inputted to the transfer function 1 / J _p s. Here, J _p is a torque estimator time constant, L is a parameter expressed by L = −J _p G _T / Δt, G _T is a torque estimator gain in the range of 0 to 2, and Δt is a sampling Time. In addition, a constant multiplier 9
Is a value as close to 1 as possible.

FIG. 2 is an equivalent block diagram when the speed detection value is viewed from the output of the PI controller 1 in the speed control system of FIG. Here, the equivalent transfer function G (s) obtained by looking at the speed detection value from the output of the PI controller 1 can be expressed by Expression 1.

[0012]

G (s) = ｛(1 + σs) / (1 + α ⁻¹ σ)
s)｝ (1 / αJs)

In this embodiment, the parameter J _p of the torque estimator 6 is made as small as possible, and L (= − J _p · G _T /
Delta] t) as large as possible (that is, by as large as possible) to the G _T, A smaller delay time sigma of the estimated torque value represented by Equation 2, omega <moment of inertia of the mechanical system in the frequency domain of the sigma ^-1 formulas 3 The value is reduced by α times as shown in FIG.

[0014]

## EQU2 ## σ = Δt / G _T

[0015]

## EQU3 ## α = 1-K (1-J / J _p )

For example, the sampling time Δ of the speed control system
When t is 5 [msec] and the moment of inertia of the mechanical system is J = 2
0 When [sec], the parameters of the torque estimator 6 J _p = 50 [msec], and G _T = 1, α = 0.1 becomes when the K = 0.9, the moment of inertia of the mechanical system 2
Apparently, 0 [sec] can be reduced to 0.1 [times] of 2 [sec]. The above corresponds to the first embodiment of the present invention.

Further, as an embodiment of the present invention, the PI adjuster 1 is adjusted as follows with respect to the inertia moment of the mechanical system reduced by α times. PI controller 1
Fig. 3 shows the gain characteristics from the output to the speed detection value.
The gain curve is bent at the frequency (α / σ) as shown in FIG. A half of this frequency (α / σ) is set as the cutoff frequency of the open loop of the speed control system, and the reciprocal of the quarter frequency is set as the integration time of the PI controller 1. That, PI controller 1 of a proportional gain K _p of Equation 4, the integration time T _i and Equation 5.

[0018]

## EQU4 ## K _p = α ² J / 2σ

[0019]

## EQU5 ## T _i = 4σ / α

Thus, according to the above numerical example, K _p =
20, T _i = 200 [msec], and the PI controller 1
It can be even without the proportional gain K so large a _p achieve high-speed response.

[0021]

As described above, according to the present invention, it is possible to achieve high-speed response speed control of a large inertia mechanical system, which has been difficult with the prior art. In the above-mentioned example, the cut-off frequency of the open loop was conventionally limited to about 2.5 [rad / s], but in the present invention, it is 10 [rad / s].
Response was improved until. Further, according to the present invention, a large inertia mechanical system in which J converted to time is 33 seconds can be apparently reduced to 10 seconds, and the cutoff frequency of the open loop is set to 5 [rad / s]. There is a track record.

[Brief description of the drawings]

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

FIG. 2 is an equivalent block diagram of FIG.

FIG. 3 is a gain characteristic diagram from an output of a PI controller of FIG. 2 to a detected speed value.

FIG. 4 is a block diagram showing a first conventional technique.

FIG. 5 is a block diagram showing a second conventional technique.

[Explanation of symbols]

 Reference Signs List 1 PI controller 2 Motor / mechanical system 3, 5, 7, 8 Adder 4 Incomplete differentiator 6 Torque estimator 9 Constant multiplier

Claims (2)

[Claims] 1. A speed control device for a motor that performs closed-loop control so that a speed detection value of a motor driving a mechanical system having a large inertia matches a speed command value, wherein a deviation between the speed command value and the speed detection value is set to zero. PI adjusting means that operates so as to: a torque estimating means that estimates the torque of the motor based on the torque equivalent value of the motor and the speed detection value; an output of the PI adjusting means; and an output from the torque estimating means. Adding means for adding a value obtained by multiplying the estimated torque value by a constant to the output of the motor. The output of the adding means is used as a torque command value of the electric motor, and the moment of inertia of the mechanical system viewed from the output of the PI adjusting means. Wherein the parameter of the torque estimating means is adjusted so as to be apparently smaller. 2. The motor speed control device according to claim 1, wherein an apparently reduced moment of inertia of the mechanical system is based on a gain characteristic from an output of said PI adjustment means to a detected speed of the motor. And adjusting the integration time and the proportional gain of the PI adjusting means.