JPH04312106A - Servo control method - Google Patents

Abstract

PURPOSE:To keep the fixed follow-up characteristic for the servo control method by automating the adjustment of the follow-up characteristic. CONSTITUTION:The difference between the target value Li and the feedback value Lp of a control system 3 is obtained at each unit time T as the control deviation L. The sum of the deviation L and the moved variable (VpXT) of the target value of each time T is obtained as a control action signal (d). A servo control part B calculates these deviation L and signal (d) and outputs the signal (d) as a manipulated variable Vs which is amplified by the gain G. Then an arithmetic control part C calculates the new gain Gv so as to secure the steady velocity deviation Kv while the subject 3 is moving at a fixed velocity based on the gain G0 set at present, the control deviation L, the moving velocity Vp, the unit time T, and the deviation Kv (ratio between the velocity Vp set in the precedent adjustment) and the deviation L). Then the gain G0 of the part B is updated into the gain Gv.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a servo control method, and more particularly to a servo control method for controlling a controlled object with high precision.

0002

[Prior Art] In order to perform high-precision machining or drawing in a control device that controls machines such as NC machine tools and drafting machines, it is necessary to control the controlled object to a time-varying target value (machining position or drawing position). data), it is necessary to generate a manipulated variable that can be accurately tracked and controlled in detail.

[0003] A servo control method for such a control device is as follows:
Every preset unit time (determined by the processing speed of the control device, etc.), the difference between the target value input from the target value storage unit and the feedback amount fed back from the controlled object is determined as a control deviation. The sum of this control deviation and the amount of movement of the target value per unit time is determined as a control operation signal. This control operation signal is amplified by a set gain to generate a manipulated variable, and the controlled object is moved by this manipulated variable. Then, by setting the gain appropriately,
The manipulated variable was generated with good follow-up characteristics for the target value.

0004

[Problems to be Solved by the Invention] In the conventional servo control method described above, even after the gain is set, the characteristics of the electronic components constituting the control device change due to environmental changes in temperature and humidity, changes over time, etc. The tracking characteristics also change. Therefore,
It was necessary to periodically change the gain and adjust the tracking characteristics. An object of the present invention is to provide a servo control method that automates the adjustment work of tracking characteristics and maintains a constant tracking characteristic.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the configuration of a control circuit using the servo control method of the present invention will be explained using FIG. 1 corresponding to an embodiment.

[0006] In the figure, numeral 3 indicates an object to be controlled. A is a conversion unit that outputs the movement amount of the controlled object 3 as a feedback amount Lp. B is a servo control unit that calculates the difference between the target value Li and the feedback amount Lp input from the conversion unit A as a control deviation L, and calculates the control deviation L and the movement amount (Vp) of the target value Li per unit time T. ×T) and the control operation signal d
It has an arithmetic function to obtain the manipulated variable Vs by amplifying the control operation signal d by a set gain G, outputs the manipulated variable Vs every unit time T, and moves the controlled object 3 by the manipulated variable Vs. let C is an arithmetic control unit that calculates unit time T, gain G0 (gain G at the previous adjustment), steady speed deviation Kv (ratio of moving speed Vp at the previous adjustment and control deviation L)
and a function to calculate the gain Gv so that the steady speed deviation becomes Kv based on the unit time T, gain G0, steady speed deviation Kv, moving speed Vp and control deviation L, and the servo The amount of movement of the target value Li per unit time T (Vp×T) and the control deviation L are input from the control unit B,
A gain Gv is set in the servo control section B.

[0007]

[Operation] The principle of calculating the newly set gain Gv from the moving speed Vp of the target value Li, the unit time T, the preset steady speed deviation Kv, the current gain G0, and the control deviation L will be explained.

When the controlled object 3 is moving at a constant speed V, the control deviation L, which is the difference between the target value Li and the feedback amount Lp, is L=Li−Lp.

It is determined by (1). The control operation signal d, which is the sum of the control deviation L and the amount of movement per unit time T (Vp×T), is: d=L+Vp×T

It is found in (2). Operation amount Vs obtained by amplifying the control operation signal d by gain G
is, Vs=G×d

It is found in (3). Movement speed V
The steady speed deviation K, which is the ratio of p and the control deviation L, is: K=Vp/L

It is obtained by (4). The feedback amount Lp per unit time T, which is the product of the constant M (a constant determined by the drive system of the controlled object 3 and the converter A), the manipulated variable Vs, and the unit time T, is Lp=M×Vs×T.

It is obtained by (5). When the controlled object 3 is moving at a constant speed V, the amount of movement (Vp×T) in unit time T and the amount of feedback Lp are equal, so from equation (5), Vp×
T=M×Vs×T
The relationship (6) holds true. From formula (6), the manipulated variable Vs is
Vs=Vp/M

It is obtained by (7). On the other hand, from equation (4), L=Vp/K

The relationship (8) holds true. Then, by substituting equation (8) into equation (2), the control operation signal d becomes: d=Vp/K+Vp×T

It is obtained by (9). When formula (9) is substituted into formula (3), the manipulated variable Vs is: Vs=G×(Vp/K+Vp×T)

It is obtained by (10). Substituting equation (7) into equation (10), Vp/M, which is the ratio of moving speed Vp to constant M, is: Vp/M=G×(Vp/K+Vp×T)
(11
). From formula (11), M=1/{G×(1/K+T)}

The relationship (12) holds true. Substituting the current gain as G0 and the current steady speed deviation as K0 into equation (12), M=1/{G0×(1/K0+T)}

The relationship (13) holds true. The gain after correction is Gv
, Equation (12) with the preset steady speed deviation as Kv
When substituted into , M=1/{Gv×(1/K
v+T)}
The relationship (14) holds true. From formula (14), Gv=1/{M×(1/Kv+T)}
(
The relationship 15) holds true. Substituting equation (13) into equation (15), the gain Gv to be newly set is: Gv=G0×(1/K0+T)/(1/K
v+T) (16). From equation (4), the current steady speed deviation K0 is: K0=Vp/L

It is obtained by (17). Formula (16
), the gain Gv is: Gv=G0×(L/Vp+T)/(1/K
v+T) (18).

The operation will be explained using the above principle. The controlled object 3 moves based on the manipulated variable Vs output from the servo control section B. The conversion unit A outputs the movement amount of the controlled object 3 to the servo control unit B as a feedback amount Lp. When the controlled object 3 is moving at a constant speed V, the servo control unit B calculates the operation amount Vs and the amount of movement per unit time T based on the target value Li and the feedback amount Lp input from the conversion unit A. (Vp×T) and control deviation L,
The operation amount Vs is output to the drive circuit 2, and the movement amount (Vp×T)
and the control deviation L are output to the calculation control section C. Arithmetic control section C
is expressed by the formula (18
) to calculate the gain Gv. Gv=G0(L/Vp+T)/(1/Kv
+T) (19) Arithmetic control section C converts gain G0 of servo control section B into gain G
Change the settings to v. As described above, since the gain Gv is set at any time, the adjustment work of the follow-up characteristic is automated, and a constant follow-up characteristic can be maintained.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control circuit using the servo control method of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 2, the vertical axis is position M, and the horizontal axis is time t. 1 is the motor. 2 is a drive circuit that drives the motor 1; Reference numeral 3 denotes a controlled object, which is driven by the rotation of the motor 1. 4 is an encoder, which is coupled to the motor 1 and generates pulses according to the rotation of the motor 1; A counter 5 counts the number of pulses input from the encoder 4 and outputs it as a feedback amount Lp every unit time T, as shown in FIG. Encoder 4 and counter 5 are combined into converter A
That's what it means.

Reference numeral 6 denotes a target value storage section in which a target value Li at each sample time shown in FIG. 2 is stored. 7 is a speed generation unit, into which the target value Li is input from the target value storage unit 6;
The amount of movement (Vp×T) is output for each unit time T. 8 is a subtracter, and the target value Li is transferred from the target value storage unit 6 to the conversion unit A.
A feedback amount Lp is inputted from the positional deviation Lp, and a positional deviation L is outputted. An adder 9 receives the position deviation L from the subtracter 8 and the movement amount (Vp×T) from the speed generator 7, and outputs a control operation signal d. Reference numeral 10 denotes an amplifier which amplifies the control operation signal d inputted from the adder 9 by a preset gain G every unit time T, and outputs it to the drive circuit 2 as a manipulated variable Vs. target value storage unit 6, speed generation unit 7, subtractor 8,
The adder 9 and the amplifier 10 are collectively referred to as a servo control section B.

Reference numeral 11 denotes a gain storage section in which the gain G0 set during the previous adjustment is stored. 12 is a unit time storage section in which a unit time T is stored. Reference numeral 13 denotes a steady speed deviation storage section in which the steady speed deviation Kv (ratio of the moving speed Vp at the time of the previous adjustment and the control deviation L) is stored. 14 is a start signal output section which outputs a start signal. Reference numeral 15 denotes a moving speed setting section, into which the moving amount (Vp×T) is inputted from the speed generating section 7, and the moving speed Vp is set based on this moving amount (Vp×T). 16 is a control deviation setting section in which the control deviation L inputted from the subtractor 8 is set. 17 is a gain calculation section, which includes a gain storage section 11, a unit time storage section 12, a steady speed deviation storage section 13, a starting signal output section 14, and a moving speed setting section 1.
5. Connected to the control deviation setting section 16 to set the gain Gv in the amplifier 10. gain storage section 11, unit time storage section 12, steady speed deviation storage section 13, starting signal output section 14,
The moving speed setting section 15, the control deviation setting section 16, and the gain calculation section 17 are collectively referred to as an arithmetic control section C.

With this configuration, the motor 1 is rotated by the operation amount Vs input from the drive circuit 2, and moves the controlled object 3. Encoder 4 outputs pulses in accordance with the rotation of motor 1. The counter 5 counts the number of pulses input from the encoder 4, and outputs the number of pulses corresponding to the position of the controlled object 3 as the feedback amount Lp to the subtracter 8 every unit time T. When the controlled object 3 is moving at a constant speed V, as shown in FIG. 2, the target value Li is output to the speed generator 7 and the subtracter 8 at the sample time Tn. When the target value Li of the sample time Tn is input, the speed generation unit 7 calculates the amount of movement per unit time T (
Vp×T) is output to the adder 9 and the moving speed setting section 15. The subtracter 8 calculates the difference between the target value Li inputted from the target value storage section 6 and the feedback amount Lp inputted from the counter 5 as a control deviation L at the sampling time Tn, and converts the control deviation L into an adder. 9 and is output to the control deviation setting section 16. The adder 9 adds the control deviation L input from the subtracter 8 and the movement amount (Vp×T) input from the speed generator 7 at the sampling time Tn, calculates a control operation signal d, and outputs the control signal d to the amplifier. Output to 10. The amplifier 10 amplifies the control operation signal d input from the adder 9 using the previously set gain G0, and outputs the calculated operation amount Vs to the drive circuit 2. Similar processing is repeated after sample time Tn+1.

[0015] The gain calculation section 17 is connected to the activation signal output section 14.
When a start signal is input from , G0 stored in the gain storage section 11, unit time T stored in the unit time storage section 12, steady speed deviation Kv stored in the steady speed deviation storage section 13, and moving speed Movement speed Vp set in the setting section 15
, take in the control deviation L set in the control deviation setting section 16, and calculate Gv=G0×(L/Vp+T)/(1/
Kv+T) is performed to calculate the gain Gv. The gain calculation unit 17 calculates the gain G set in the amplifier 10.
0 to gain Gv, and the gain G0 stored in the gain storage unit 11 is updated to gain Gv.

As described above, according to this embodiment, the gain Gv is adjusted at any time so that the steady speed deviation Kv is constant.
Since the following characteristics are set, the adjustment work of the following characteristics is automated, and a constant following characteristic can be maintained.

[0017]

[Effects of the Invention] As described above, according to the present invention, since the gain is set so that the steady speed deviation becomes a predetermined value, the adjustment work of the tracking characteristic is automated, and the constant tracking Characteristics can be maintained. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control circuit for implementing the servo control method of the present invention.

FIG. 2 is a characteristic diagram illustrating the servo control method of the present invention.

[Explanation of symbols]

A: Conversion section B: Servo control section
C... Arithmetic control unit 3... Controlled object

Claims (1)

[Claims] Claim 1: The difference between the target value and the amount of feedback is obtained as a control deviation for each preset unit time, and the sum of this control deviation and the amount of movement of the target value per unit time is used as a control operation signal. In the servo control method, the control operation signal is amplified by a predetermined gain to obtain the manipulated variable, the controlled object is moved by this manipulated variable, and the movement amount of the controlled object is returned as a feedback amount. A servo control method in which the controlled object is moved while keeping the moving speed of the target constant, and the gain is set so that a steady speed deviation, which is a ratio of the moving speed of the target value and the control deviation, becomes a predetermined value.