JP3570469B2 - Motor speed control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor speed control device that performs closed-loop control of the rotation speed of a motor connected to a mechanical system with respect to a speed command value.
[0002]
[Prior art]
FIG. 4 shows a block diagram of this type 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 PI regulator transfer function represented by _{K P (1 + 1 / T} i s), 2 is a motor-mechanical system represented by 1 / Js, 3 is the difference between the speed command value and the speed detection value of the motor This is the adder to be sought. Incidentally, 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]
[Problems to be solved by the invention]
In the prior art described above, in order to obtain the desired speed control response, the proportional gain K _P and integral time T _i of the PI regulator 1 has to be local adjustment.
For example, in order to make the cutoff frequency ω _c of the open loop transfer function of the speed control system about 20 [rad / sec] for the AC motor, the proportional gain K _P = Jω with respect to the value of the inertia moment J _It is necessary to set _c = 20J.
[0004]
However, since the actual moment of inertia J of the motor / mechanical system 2 often differs from the design value, the moment of inertia J is actually measured by connecting the motor and the mechanical system at the time of on-site adjustment, and the proportional gain determining the K _P, inevitably going through complicated steps of adjusting, variations due to labor and coordinators of adjustment has been a problem.
[0005]
Therefore, the present invention eliminates the need for complicated adjustment work in a state where the motor and the mechanical system are connected on site by making the moment of inertia J of the motor and the mechanical system independent of the response of the speed control system. It is an object of the present invention to provide an electric motor speed control device.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, an invention according to claim 1 is a motor speed control device that performs closed loop control so that a detected speed value of a motor to which a mechanical system is connected matches a speed command value.
Adjusting means operable to reduce the deviation between the speed command value and the detected speed value to zero; torque estimating means for estimating the torque of the electric motor based on the torque equivalent value of the electric motor and the detected speed value; Adding means for obtaining a torque command value by adding the output of the means and the torque estimated value output from the torque estimating means,
Said torque estimating means, and the model corresponding to the motor and mechanical system, the deviation of the speed detection value and the speed estimated value output from the model is input and outputs the torque estimated value, parameter torque estimating means time constant, possess a controller, represented by the gain and sampling time, and means for input to said model a deviation between the torque estimated value output from the said torque equivalent value controller,
By increasing the parameters of the controller with the time constant of the torque estimating means fixed, model matching is performed by matching the apparent moment of inertia of the motor / mechanical system with the time constant of the torque estimating means in a wide frequency range. Is what you do .
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described 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.
[0009]
In FIG. 1, a deviation between a speed command value and a detected speed value of the motor is obtained by an adder 3. This deviation is input to the P of the proportional gain K _P (proportional) controller 4, a torque estimated value which is the output of torque estimator 6 described later and its output is added by the adder 5 obtains the torque command value Can be This torque command value is given to the electric motor / mechanical system 2.
The torque estimator 6 outputs a torque estimated value by inputting the torque command value and the speed detection value of the electric motor. 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 uses the torque command value is configured by a closed loop.
[0010]
Torque estimator 6 obtains the torque estimator transfer function 1 / J deviation adder 7 and P _s the speed estimation value and the speed detection value after the model 10 corresponding to the motor-mechanical system 2, the controller and the results Enter 9 The controller 9 inputs the estimated torque value output via the parameter L to the adder 5. Further, 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 input to the torque estimator model 10.
Here, _{J P} is time constant torque estimator, L is a parameter represented by _{L = -J P · G T /} Δt, torque estimator gains ranging _{G T} is 0 to 2, Delta] t is the sampling Time.
[0011]
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. The equivalent transfer function G (s) in FIG.
[0012]
(Equation 1)
G (s) = {(1 + σ a s) / (1 + σ b s)} (1 / J P s)
[0013]
Σ _a and σ _b are time elements, and in the frequency range of ω <1 / 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 It becomes _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]
(Equation 2)
σ _a = _JP / L
[0015]
[Equation 3]
σ _b = J / L
[0016]
In this embodiment, fixing the time constant J _P torque estimator, controller parameters 9 L - reduce the time element sigma _a, sigma _b by as large as possible _{(= J P · G T /} Δt), wide performing model matching to the moment of inertia J of the torque estimator time constant J _P apparent motor-mechanical system 2 in the frequency domain.
[0017]
For example, when the sampling time Δt of the speed control system is 5 [msec] moment of inertia J of the motor-mechanical system 2 is 2 _[sec], J P = 500 _[msec], sigma _a = 5 in _G T = 1 [ msec], sigma _b = 20 [msec], and the can be regarded as approximately omega <50 _[J P = 500 in the frequency domain the moment of inertia of the apparent electric motor and mechanical system 2 rad / sec] [msec].
In the present embodiment, since it is possible to adjust the speed control system in setting the proportional gain K _P of the P controller 4 in accordance with the moment of inertia of the load, the actual motor-mechanical system 2 moment of inertia J is Even if it is not clear, a desired speed control system response can be obtained.
[0018]
For time constant J _P torque estimator, as described below to set the proportional gain K _P of the P controller 4.
In the above example, when the gain characteristic from the output of the P adjuster 4 to the detected speed value of the motor is drawn, the gain curve is bent at a frequency of 1 / σ _b as shown in FIG. Less than half of the frequency of this frequency and the cutoff frequency omega _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]
(Equation 5)
K _P ≦ J _P / 2σ _b
[0021]
In the above numerical examples, from Expressions 4 and 5, ω _c ≦ 25 [rad / sec] and K _P ≦ 12.5.
[0022]
In FIG. 1, the controller that receives the deviation between the speed command value and the detected speed value of the motor as an input may be a PI controller as shown in FIG.
[0023]
【The invention's effect】
As described above, according to the present invention, since the adjustment of the speed control system can be performed independently of the moment of inertia of the electric motor / mechanical system, it is not necessary to actually adjust the electric motor and the mechanical system in a connected state, The labor and time required for on-site adjustment work can be reduced, and variations caused by coordinators can be eliminated.
Actually, in the present invention, the cut-off frequency ω _c of the open-loop transfer function is set to 20 [rad / sec] while the set values of the torque estimator and the P regulator are the same for J = 0.5 to 3 [sec]. It has been proven that ω _c = 20 [rad / sec] for an electric motor / mechanical system with J = 2 [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.
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 (1)

In a motor speed control device that performs closed-loop control so that a speed detection value of a motor connected to a mechanical system matches a speed command value,
Adjusting means operating to reduce the deviation between the speed command value and the speed detection value to zero,
Torque estimation means for estimating the torque of the motor based on the torque equivalent value of the motor and the speed detection value,
Adding means for adding a torque command value by adding an output of the adjusting means and a torque estimated value output from the torque estimating means,
The torque estimating means includes:
Models corresponding to electric motors and mechanical systems,
Outputs the deviation is input torque estimation value estimated speed value output from the model and the speed detection value, and the controller parameters represented by the time constant, gain and sampling time of the torque estimation means,
Means for obtaining a deviation between the torque equivalent value and the estimated torque value output from the controller and inputting the deviation to the model,
Have a,
By increasing the parameters of the controller with the time constant of the torque estimating means fixed, model matching is performed by matching the apparent moment of inertia of the motor / mechanical system with the time constant of the torque estimating means in a wide frequency range. speed detecting device of a motor and performing.

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