JPH01227675A - Motor controller - Google Patents

Abstract

PURPOSE:To obtain a motor controller which is strong against disturbance by so setting a transfer function of feed-forward controlling as to become the sum of the denominator of the function of an object to be controlled and the transfer function of a proportional-differentiation controller. CONSTITUTION:An output obtained by adding the output theta of an object 3 to be controlled to a proportional-differentiation controller 5 is subtracted from an output obtained by adding a deviation (e) between a command value U and the output theta to a proportional integrating controller 4. Further, the value U added with the output obtaining through a feed-forward unit 2 to the subtracted output is supplied to the object 3 to be controlled. Here, the transfer function of the unit 5 is so set as to become the sum of the denominator of the function of the object 3 to be controlled and the function of the controller 5. Thus, a motor can control a high response without delay with respect to a motor command.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a motor control device.

[Prior Art] Generally, when the torque of a motor is T, the moment of inertia is J, the coefficient of viscous friction (mechanical resistance) is D, and the rotation angle is θ, the block diagram is as shown in Fig. 4, and the rotation angle and The torque relationship is expressed as.

In a mechanical system such as a motor, the torque T is given by (r is the input), so it can be written as (J s2 +Ds)θ=A r+B sθ. This is shown in a block diagram as shown in FIG. 5, and the transfer function G (s) from the input r to the output θ is as follows. In a mechanical system where the moment of inertia and mechanical resistance do not change (including cases where these changes are negligible), A =
Since J, B=D, it becomes.

Therefore, in such a mechanical system, the transfer function G of the controlled object is
(s) lt 1/s 2.

Therefore, hereinafter, the transfer function G(s) is set to 1/S2.

Feedback control is conventionally known as a rotational position control of a motor. However, with simple feedback control, since the deviation from the motor command value is detected and then controlled to reduce that deviation, the response is poor and it cannot be used for applications that require high response. was there. Furthermore, since disturbances are inherent in controlling mechanical systems, a control means that is resistant to disturbances is desired.

To improve the above-mentioned drawbacks, for example, as shown in FIG. PI-PD control is known in which the deviation from the output obtained by passing θ through a proportional and differential (FD) controller 5 is used as the input r to the controlled object 3.

Here, the transfer function G2 of the PI controller 4 and the FD controller 5 is
(S) and G3 (S) are each represented by the following formula.

G2 (S) = 1, (1-Q) +-,-G3
(s) = 1 to α+3 s ”However, α is O
K1 is a proportional gain, K2 is an integral gain, and K3 is a differential gain.

It has also been proposed to carry out feedforward control as shown in Japanese Utility Model Application Publication No. 1983-1989-L'ta3eoa. As shown in FIG. 6, this is the position command U
and the deviation e of the position output θ by proportional, integral, and differential (P I
D) The sum of the proof force obtained by passing the position command U through the controller 1 and the output obtained by passing the position command U through the feed forward device 2 is used as the input r to the controlled object 3. Here, the PIDID controller performance function Gz (s) is expressed by the following equation.

However, K1 is a proportional gain, K2 is an integral gain, and K3 is a differential gain.

[Problems to be Solved by the Invention] However, although the conventional PI-FD control (FIG. 7) is strong against disturbances, it has the disadvantage of poor coordination. In addition, control devices that add feedforward control to conventional PID control (Fig. 6) generally have excellent quick response speed, but they have the disadvantage of being susceptible to external disturbances. be.

Therefore, it is conceivable to add a feedforward element s2 to the disturbance-resistant loop of the conventional PI-FD control, as shown in Fig. 8. However, in this control system, in response to a constant acceleration input command, There was a problem in that it caused a delay. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a motor control device in which a position output follows an input command without delay, and which is resistant to external disturbances. do.

[Means for Solving the Problems] The present invention obtains a deviation between a position command given to a controlled device whose moment of inertia and mechanical resistance can be considered constant and a position output of the controlled device through a proportional-integral controller. From the output, the output obtained by passing the position output through a proportional differential controller is subtracted by φ1, and the output obtained by passing the position command through a feedforward device is added to the motor control which is input to the device to be controlled. , the transfer function of the feedforward control is the denominator S of the transfer function of the controlled object.
2 and the front portion, the transmission amount of the proportional component 1 controller, and the movement were selected to be the sum. ,, ・11
Clause 1,, [cut use],.

15. In the control device of the present invention, the input r to the control pair PL is 1. Output of feedforward device F-(s)
u and proportional-integral control,! (PI controller), 9 outputs G 2
For example, by changing (s,)e and subtracting the output G3(s)θ of the differential control system (one FD controller), 'p+,
, < can be obtained, but PI open control ・Input to the device (
The difference e) between the position command U and the position neutral force θ is O in the tracking state.
Or, F? , r = F (s,), , u-(K1, a+-3s) θ0 = -1 Therefore, the transfer function from the position command U to the position output θ is as follows. According to the present invention, the transfer function F (s) of the feedforward controller is changed to the transfer function 1152 (s) of the controlled object (
7) Denominator S2 and FD controller transfer function G 3 (s)−
Since it was selected to be the sum of 1 α + 3 s, that is, F(s) = s2 + 1 α + 3 s, θ/u = 1.

From this, the position output θ follows the position command U without delay.

[Example] An embodiment of the present invention will be explained with reference to FIG.

The controlled object 3 is a mechanical controlled object such as a motor, and its transfer function G (s) is 1/s2.

The output of the controlled object 3 is calculated from the output of the PI controller 4 obtained by adding the deviation e between the command value U and the output θ of the controlled object 3 to the proportional-integral controller (PI controller) 4. FD obtained by adding θ to the proportional differential controller (PD controller) 5
The output of the controller 5 is subtracted, and the output obtained by passing the command value U through the feedforward device 2 is added to this subtracted output to obtain the input r to the controlled object 3.

Here, the input to the PI controller 4 is e=u−θ, and P
Since the transfer function of the I controller 4 is 1 (1-.) + Lee, the output from the PI controller 4 is (K, (1-.
) 10 anus) e However, in the state of tracking, U=θ and therefore e=0, so the output from the PI controller 4 becomes 0.

Furthermore, the transfer function of the PD controller 5 is 1 α + 3 s, and the transfer function of the feedforward device 5 is F(s)
= 1 for s2+ and 3 s for cx+, so r= (1 for s2 +, 35 for a+)u-(K1α+3s)θ. And, since θ=ding/s2, s2 θ=
(1 to s2 + 35 to a+) u-(K1α 1 to 3
s) θ Therefore, the position output θ follows the command value U without delay.

The above is a case of a continuous system in which the controlled object is analog-controlled.

Next, FIG. 2 shows a discrete system in the case of digital control, where the sampling variable is Z and each controller in FIG. 1 is obtained by Z-transforming.

In other words, S in the Laplace transform is replaced with 1-Z-1. The part surrounded by the dotted line in the figure is a digital part, and switches S1, S2, and S3 are provided to turn on and off the command value U, the feedback output θ, and the input r to the controlled object 3 at different timings.

The function is similar to that shown in FIG.

However, the differentiation is performed using the difference in data before l sampling, and by setting the sampling period short, this problem can be avoided in practice.

Note that the discrete system shown in FIG. 2 requires D/A conversion, A/D conversion, sample hold, etc., but since these are all well-known means, their explanations will be omitted.

Using the discrete system shown in FIG. 2, the conventional control method and the results of motor control according to the present invention are shown in FIGS. 3 and 9. In Figure 3, ■ is input (position command), ■ is PI-PD amount control without overshoot, and ■° is PI-
FD sub-control overshoot occurs, ■ is PID
+ID-forward control, ■ is PI-PD+ of the present invention
In these results showing the results in the case of feedforward control, the conventional method (■) has a slow rise, and ■'' has a slightly larger coefficient α to speed up the rise, but due to overshoot, it takes longer to stabilize. is long. In ■ and ■, there is almost no delay in position output θ with respect to input U. However,
Figure 3 shows the case where there is no disturbance.

In the experimental results when there is a disturbance, as shown in Figure 9,
In the PID+ID-forward control (2), the displacement is large in response to a suddenly applied force, and the time it takes to come to rest is long, whereas in (2) of the present invention, the displacement is small and the time it takes to come to rest is short.

Although the above embodiments are examples for rotary motors, it goes without saying that the present invention can also be used for mechanical systems including linear motors. Furthermore, if the state of change of the moment of inertia and mechanical resistance with respect to time is known, by adjusting A and B in Fig. 5 so that the relationship of transfer function G(s) = l/s2 is satisfied, The invention can be practiced.

[Effects of the Invention] The present invention, in a control system that combines PI-PD control and feedforward control, makes the feedforward term equal to the sum of the denominator S2 of the transfer function of the controlled object and the transfer function of the proportional derivative controller. Since this is selected, it is possible to obtain a motor control device that has no delay with respect to motor commands, can perform highly responsive control, and is resistant to external disturbances.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the motor control device of the present invention, and FIG.
The figure is a block diagram of a discrete system for digital control.
3 and 9 are graphs showing the experimental results of the present invention and the conventional example, FIGS. 4 and 5 are block diagrams of the controlled object, and FIGS. 6 to 8 are blocks of the control device according to the prior art. It is a line diagram. 1--1-PID controller, 2-11~feedforward device, 3-111 controlled object, 4-1--PI controller, 5----PD controller.

Claims (1)

[Claims] (1) From the output obtained by passing the deviation between the position command given to the controlled device whose moment of inertia and mechanical resistance can be considered constant and the position output of the controlled device through a proportional-integral controller,
A motor control device that subtracts an output obtained by passing the position output through a proportional differential controller, and adds an output obtained by passing the position command through a feedforward device to input the result to the controlled device; A motor control device characterized in that a transfer function for feedforward control is selected to be the sum of a denominator s^2 of the transfer function of the controlled object and a transfer function of the proportional differential controller.