JPH0378802A - Sliding mode control system - Google Patents

Abstract

PURPOSE:To attain the control of a sliding mode without inducing the resonance of a machine system by applying a filter processing to eliminate the resonance frequency component of the machine system out of the current command component consisting of a current switching item and then adding the current command component to that obtained from the linear control to obtain a current command. CONSTITUTION:The current command component obtained from the linear control, e.g., the proportion control is separated from the current command component consisting of a switching item which generates a sliding mode. Then a filter processing is supplied to only the current command component consisting of the switching item via an LPF, a notch filter, etc. Thus the resonance frequency component of a machine system is eliminated. Thus the resonance frequency component of a machine system is eliminated Then the current command component consisting of the switching item is added to the current component obtained from the linear control. Thus a current command is generated and outputted. As a result, the sliding mode control is attained without deteriorating the positioning performance due to the LPF or the notch filter nor inducing the resonance of the machine system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a variable structure system.
Sliding mode control system in ture system (prior art) One of the control systems is a variable structure system.

This includes the coefficients of multiple parameters that determine the control input,
In other words, this is a system in which the magnitude of the gain is switched depending on the stage of control. Among these, sliding mode control is a control method in which the gain of the control input is switched according to the control stage so that the controlled object moves along a slip plane preset in a state plane.

Conventionally, the control input obtained by sliding mode control was used as is or through a filter.

In the former case, the switching frequency of the current for generating sliding mode tends to increase as the sampling time becomes shorter, and therefore, the high frequency component of the current generated due to the switching causes damage to the mechanical system to be controlled. May transmit resonance. This tendency becomes particularly strong when the switching frequency is close to the natural frequency of the mechanical system.

In order to alleviate this problem, a low-pass filter or a notch filter is usually provided after the current output command as in the latter case, and the current output is generated through the low-pass filter or notch filter. In this case, although the resonance of the mechanical system is alleviated, the provision of the filter has an adverse effect on control performance, and in positioning control, this may impede high-speed positioning performance or cause overshoot.

[Problem to be solved by the invention]

Therefore, the problem to be solved by the present invention is to realize sliding mode control without deteriorating the positioning performance of the low-pass filter or notch filter and without inducing resonance in the mechanical system.

[Means to solve the problem]

The present invention configures a current command by sliding mode control into a current command component by linear control and a current command component consisting of a current switching term, and removes a mechanical system resonance frequency component from the current command component consisting of the current switching term. The present invention is characterized in that filter processing is performed and then added to the current command component obtained by the linear control to obtain the current command.

In this sliding mode control method, if the positioning trajectory based on the current command component by the current switching term deviates from the region specified on the phase plane, filter processing is not performed for that part to minimize the degradation of robustness. can do.

[Effect]

In the present invention, sliding mode control is constructed by separating a current command component caused by linear control (for example, proportional control) and a current command component made up of a switching term for generating the sliding mode, and a current command component made of a switching term is configured. Only the components are filtered using a low-pass filter, a notch filter, etc. to remove the resonance frequency component of the mechanical system. Thereafter, it is added to the current component by linear control to form a current command and output.

Here, filtering the current command component consisting of the switching term degrades the inherent robustness of sliding mode control, but in order to suppress this as much as possible, we In this case, it is desirable to output the current command component based on the switching term without performing filter processing.

As described above, sliding mode control can be configured without deteriorating positioning performance due to a low-pass filter or notch filter, and without inducing resonance in the mechanical system.

〔Example〕

Embodiments in which the present invention is applied to positioning control of a DC servo motor will be described below.

When the linear control is proportional control, the current command U by sliding mode control is as shown in equation (1).

U = k, SR+ ks X+ ・・・・・・
・・・・・・・・・(1) However, Sl= k p X+
10X2, X+ = χ"-χ1, 2 sentences.

・χr: Position command, xl: Position , , k, , k, : proportional gain.

The first term on the right side of equation (1) is the current command component due to proportional control,
The second term is the current command component due to the switching term.

In order to satisfy the sliding mode generation conditions, it is necessary to satisfy the following formula.

”− 2≧k, ・・・・・・・・・・・・・・・
・・・・・・(3) kd However, J: Moment of inertia of the motor, k7: Torque constant In this way, by changing the sign of 5IXI, (1
) ks of the second term on the right side of the equation (4) and (5
), chattering occurs in the current output.

The present invention outputs only the current command component based on this switching term via a filter.

ks when Si X+ > O is ksp, SI
When X+ < O, let be ksN, then k
sP and A'SN are as shown in FIG. 1 on the phase plane. Further, when the trajectory is within the shaded area δ, the current switching term is outputted through the filter, and when the trajectory appears outside of δ, it is outputted without passing through the filter. The present invention is illustrated in FIG. 2.

The current command is calculated by software using a signal processor or the like, but the filter circuit can also be configured by hardware in consideration of program execution time and the like.

FIG. 3 shows a flowchart when the process is executed by software including the filter circuit. In the figure, in steps 100 to 140 and 150, the calculations of equations (3) to (5) described above are executed. Step 16
0 and 170, it is determined whether or not to perform filter processing on the switching term. If YES, filter processing is performed in step 180. If the determinations in steps 160 and 170 are NO, the filtering process in step 180 is not performed and the sliding mode is instantaneously generated. In step 190, as previously calculated in step 120,
- Add Sl and the switching term, and in step 200 output the calculation result from the D/A converter to the current amplifier.

FIG. 4 shows a flowchart when filter processing is configured by hardware (filter circuit 10). In the figure, the processing in steps 300-370 is the same as the processing in steps 100-170 in FIG.

The D/A converter 1 outputs @.Sl as an analog result of the calculation in step 320 (step 500).
The D/A converters 2 and 3 output analog switching terms. The D/A converter 2 is connected to an analog filter circuit 10, and the D/A converter 3 is not connected to the filter circuit 10. When passing through the filter circuit 10, D
The output of the /A converter 3 is set to 0, and the switching term is output from the D/A converter 2 (steps 380 and 390). When the signal is not passed through the filter circuit 10, the output of the D/A converter 2 is set to O, and the D/A converter 3 outputs a switching term. These outputs are added by the adder 20 to the D obtained in step 500.
The output from the /A converter 1 is added to the .Sl output and input to the current amplifier.

〔Effect of the invention〕

Since the present invention has the above configuration, it has the following effects.

■ The control human power is divided into the proportional control part and the switching top part, and a filter is applied only to the switching term, so the characteristics of normal proportional control are not impaired.

■ Features sliding mode control, making it highly robust against parameter fluctuations.

■ Current chattering can be suppressed by the filter effect of the switching term.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the phase plane locus and switching terms, FIG. 2 is a control block diagram of the present invention, and FIG. 3 is a flowchart of the control method when the filter circuit is configured by software.
FIG. 4 is a flowchart of a control method when the filter circuit is configured by hardware. Figure 1 x 2

Claims (1)

[Scope of Claims] 1. A current command by sliding mode control is composed of a current command component by linear control and a current command component consisting of a current switching term, and the current command component consisting of the current switching term has a resonance frequency of the mechanical system. A sliding mode control method characterized in that a filter process is performed to remove the component, and then a current command is obtained by adding it to the current command component obtained by the linear control. 2. The sliding mode control method according to claim 1, wherein if the positioning locus based on the current command component by the current switching term deviates from a region designated on the phase plane, filter processing is not performed for that portion. .