CN101144493A - Dynamic compensation hydraulic pressure servo valve null shift method - Google Patents

Abstract

A dynamic compensation hydraulic pressure servo valve zero drift method is disclosed. A displacement sensor, an oil pressure sensor, and a servo valve are arranged on a rolling machine hydraulic cylinder, and the displacement detection and the oil pressure signal of the hydraulic cylinder are read through a PLC high speed gathering module, to calculate the zero drift compensation amount of the hydraulic pressure servo valve, and to control the opening degree of the servo valve to perform the closed loop adjustment of the hydraulic cylinder position. The positive effect of the invention can be used for any HAPC algorithm, can not only guarantee the response speed of the original system, but aslo greatly enhance the static control precision of the original system.

Description

A kind of method of dynamic compensation hydraulic pressure servo valve null shift

Technical field

The invention belongs to oil hydraulic cylinder automated location control (HAPC) technical field, particularly a kind of method of dynamic compensation hydraulic pressure servo valve null shift in the board rolling.

Background technique

The HAPC regulator is that the actual hydraulic pressure cylinder position that is obtained by displacement sensor is compared with the position setting value, and deviation signal is through the regulator computing, and D/A exports computing, after power amplifier amplifies, regulate the servovalve opening degree, the Position of Hydraulic Cylinder closed loop control is finished in the motion of control hydraulic cylinder piston.HAPC control system principle as shown in Figure 1, HAPC control system skeleton diagram is as shown in Figure 2.

HAPC regulator among Fig. 2 is generally selected the PID controller for use, considers that rolling machine system has high requirement to the dynamic responding speed of Position of Hydraulic Cylinder control, and the HAPC regulator is selected the P controller for use usually.

Hydraulic efficiency servo-valve all inevitably has zero drift phenomenon.Show as when the servovalve controlled quentity controlled variable is zero, servovalve has lasting leakage, and then oil hydraulic cylinder has lasting displacement.

The drift amount is meant that when the servovalve controlled quentity controlled variable was μ, oil hydraulic cylinder did not have lasting displacement.When the HAPC regulator was selected the P controller for use, the static error amount that is caused by drift was ε=μ/P, for example: when μ=5 (expression servovalve opening degree 5%), P=500, static error ε=μ/P=5/500=0.01mm.

The method that solves drift at present has two kinds:

1, selects for use the PI controller as the HAPC regulator, drift is eliminated, reach the purpose of dynamic elimination static error by introducing integral controller.But the cost of doing like this is the dynamic responding speed of sacrificial system;

2, mean value is obtained in the stable state output value sampling of PI controller,, adopted the output quantity of P controller to add the servovalve controlled quentity controlled variable of μ as the HAPC regulator as the drift amount μ of HAPC regulator.Do like this and can only eliminate drift in one period, but along with the hydraulic system operation, the drift meeting changes with the field condition variation, static error also changes accordingly.This method can not fundamentally reduce static error.

All there is defective in these two kinds of methods, can't take into account the requirement and the little requirement of static error of the rapid dynamic response speed of system.

Summary of the invention

At the problem that existing HAPC system exists, the invention provides a kind of method of dynamic compensation hydraulic pressure servo valve null shift, it has dynamic adjustments, and system response time is fast, the advantage that error is low.

The present invention does not carry out any modification to the HAPC regulator of original system, only need insert dynamic compensator between HAPC regulator and servoamplifier (D/A converter) gets final product, specific practice as shown in Figure 3, the output of original system HAPC regulator is connected to the input end of dynamic compensator, and the output of dynamic compensator is connected to the input end of servoamplifier.The dynamic compensator function is to realize by the dynamic compensation amount software for calculation that embeds PLC, and this software calculates compensation rate according to the dynamic compensation algorithm.The principle of dynamic compensator as shown in Figure 4.

Algorithmic formula is: U (i)=U _a(i)+α μ (i)=U _a(i)+α lim (U (i-1), HL, LL) (1)

U wherein _a(i) be HAPC regulator i output value constantly, U (i) be the i output value constantly of dynamic compensator, and α is an accommodation coefficient, HL, LL be about amplitude limit.The Parameter H L that algorithm only need be determined, LL and α.

[regulation 1]: U, U _a, μ, HL, the LL span is (100,100), expression servovalve opening degree controlled quentity controlled variable ,-100 expression negative sense maximum open, 100 expression forward maximum open.

[regulation 2]: error E unit is mm, and the APC regulator selects P regulator, then U _a(i)=and PE (i), the unit of P is

1, determine HL, LL:

At first with HL, LL all is changed to 0, then U (i)=U _a(i).U under the system stability state (i) repeatedly sampled asks on average as the present drift value of system: $\mathrm{\μ}=\underset{i\→\∞}{\lim }U\left(i\right),$ Get HL=| μ |+2, LL=-HL.

2, determine α:

The APC regulator selects the P regulator, by U _a(i)=PE (i), then system's static error: $\underset{i\→\∞}{\lim }E\left(i\right)=\underset{i\→\∞}{\lim }\frac{1}{P}{U}_a\left(i\right),$

Get by formula (1): U _a(i)=U (i)-α lim (U (i-1), HL, LL), and after system enters stable state, U (i-1) enter (LL, HL) in the scope, then lim (LL)=U (i-1), the system static error of drawing is for U (i-1), HL:

$\underset{i=\∞}{\lim }E\left(i\right)=\underset{i\→\∞}{\lim }\frac{1}{P}[U\left(i\right)-\mathrm{\αlim}(U(i-1),\mathrm{HL},\mathrm{LL})]=\underset{i\→\∞}{\lim }\frac{1}{P}[U\left(i\right)-\mathrm{\αU}(i-1)]---\left(2\right)$

This shows, when α=1, system's static error $\underset{i\→\∞}{\lim }E\left(i\right)=\underset{i=\∞}{\lim }\frac{1}{P}[U\left(i\right)-U(i-1)]=0,$ Yet this situation tends to cause system oscillation, so α will get the numerical value less than 1, it is better to draw α value effect in (0.8,0.9) scope by research.

The present invention's its tangible characteristics and positive effect compared to the prior art is: the invention provides a kind of method that the original system dynamic responding speed has static high-precision dynamic compensation hydraulic pressure servo valve null shift again concurrently that promptly do not reduce, thereby improve the position control accuracy of HAPC regulator.The present invention has remarkable progress than prior art as can be seen.

Description of drawings

Fig. 1 is existing HAPC control system schematic diagram;

Fig. 2 is existing HAPC control system skeleton diagram;

Fig. 3 is a HAPC control system skeleton diagram of the present invention;

Fig. 4 is the dynamic compensation algorithm block diagram;

Fig. 5 is the dynamic compensator interface definition;

Fig. 6 is a control system structural representation of the present invention;

Fig. 7 is a dynamic compensator program flow diagram of the present invention;

Among the figure: 1HAPC regulator, 2 servoamplifiers, 3 servovalves, 4 oil hydraulic cylinders, 5 oil pressure sensors, 6 pressure transducers, 7 displacement transducers, 8 milling trains, 9 variable-gains, 10 pressure amplitude limit regulators, 11 position controllers, 12 dynamic compensators, 13 rolled pieces, Ua is a HAPC regulator output value, and α is an accommodation coefficient, HL, LL is an amplitude limit up and down, and Enable is the dynamic compensator switch, and U is the output value of dynamic compensator.

Embodiment

As shown in Figure 3, the present invention includes the HAPC regulator, dynamic compensator, servoamplifier, servovalve, oil hydraulic cylinder also links to each other successively; Between oil hydraulic cylinder and HAPC regulator, be connected with oil pressure sensor and pressure transducer; Between oil hydraulic cylinder and HAPC regulator, be connected with displacement transducer.The HAPC regulator is the deviation between the given and measured value according to the position, and control servovalve opening degree carries out the Position of Hydraulic Cylinder closed-loop adjustment.Wherein: the dynamic compensator program as shown in Figure 7, the principle of dynamic compensator as shown in Figure 4, its used dynamic compensation algorithm steps is as follows:

Algorithmic formula is: U (i)=U _a(i)+α μ (i)=U _a(i)+α lim (U (i-1), HL, LL) (1)

U wherein _a(i) be HAPC regulator i output value constantly, U (i) be the i output value constantly of dynamic compensator, and α is an accommodation coefficient, HL, LL be about amplitude limit.The Parameter H L that algorithm only need be determined, LL and α.

[regulation 1]: U, U _a, μ, HL, the LL span is (100,100), expression servovalve opening degree controlled quentity controlled variable ,-100 expression negative sense maximum open, 100 expression forward maximum open.

[regulation 2]: error E unit is mm, and the APC regulator selects P regulator, then U _a(i)=and PE (i), the unit of P is

1, determine HL, LL:

At first with HL, LL all is changed to 0, then U (i)=U _a(i).U under the system stability state (i) repeatedly sampled asks on average as the present drift value of system: $\mathrm{\μ}=\underset{i\→\∞}{\lim }U\left(i\right),$ Get HL=| μ |+2, LL=-HL.

2, determine α:

The APC regulator selects the P regulator, by U _a(i)=PE (i), then system's static error: $\underset{i\→\∞}{\lim }E\left(i\right)=\underset{i\→\∞}{\lim }\frac{1}{P}{U}_a\left(i\right),$

Get by formula (1): U _a(i)=U (i)-α lim (U (i-1), HL, LL), and after system enters stable state, U (i-1) enter (LL, HL) in the scope, then lim (LL)=U (i-1), the system static error of drawing is for U (i-1), HL:

$\underset{i=\∞}{\lim }E\left(i\right)=\underset{i\→\∞}{\lim }\frac{1}{P}[U\left(i\right)-\mathrm{\αlim}(U(i-1),\mathrm{HL},\mathrm{LL})]=\underset{i\→\∞}{\lim }\frac{1}{P}[U\left(i\right)-\mathrm{\αU}(i-1)]---\left(2\right)$

This shows, when α=1, system's static error $\underset{i\→\∞}{\lim }E\left(i\right)=\underset{i=\∞}{\lim }\frac{1}{P}[U\left(i\right)-U(i-1)]=0,$ Yet this situation tends to cause system oscillation, so α will get the numerical value less than 1, it is better to draw α value effect in (0.8,0.9) scope by research.According to the control accuracy requirement, determine accommodation coefficient α, get 0.85 usually;

When the HAPC regulator output signal first time: U (0)=U _a(0);

When the HAPC regulator output signal second time: U (1)=U _a(1)+and α lim (U (0), HL, LL);

When HAPC regulator for the third time during output signal: U (2)=U _a(2)+and α lim (U (1), HL, LL);

When the i time output signal of HAPC regulator: U (i)=U _a(i)+and α lim (U (i-1), HL, LL).

When HAPC regulator parameter: P=500 is set, μ=5, dynamic compensator determines that parameter is as follows:

HL=| μ |+2=7, LL=-HL=-7, promptly (LL, HL)=(7,7); Get α=0.85;

Then get system's static error by formula (2):

$\underset{i\→\∞}{\lim }E\left(i\right)=\underset{i\→\∞}{\lim }\frac{1}{P}[U\left(i\right)-\mathrm{\αU}(i-1)]=\frac{1-\mathrm{\α}}{P}\underset{i\→\∞}{\lim }U\left(i\right)=\frac{1-\mathrm{\α}}{P}\mathrm{\μ}=0.0015\mathrm{mm};$

If do not use dynamic compensator (α=0), then system's static error is $\underset{i\→\∞}{\lim }E\left(i\right)=\frac{1}{P}\mathrm{\μ}=0.01\mathrm{mm}.$ This shows that dynamic compensator reduces by 85% with the static error of original system.And because (dynamic compensator is to the almost not influence of dynamic characteristic of original system for LL, restriction HL).

This method effect in actual applications:

1, in 3000mm heavy and medium plate mill HAPC regulator, hydraulic station working pressure 28Mpa, oil hydraulic cylinder internal diameter 1100mm, hydraulic cylinder travel 50mm, back pressure pressure 3Mpa, oil hydraulic cylinder displacement transducer resolution 1 μ m, servovalve selects MOOG-D792.Use the present invention, the Position of Hydraulic Cylinder static error can be controlled at ± 2 μ m within.

2, in 450mm single chassis reversable cold-rolling machine HAPC regulator, hydraulic station working pressure 21Mpa, oil hydraulic cylinder internal diameter 300mm, hydraulic cylinder travel 50mm, back pressure pressure 1Mpa, oil hydraulic cylinder displacement transducer resolution 1 μ m, servovalve selects FF102-30.Use the present invention, the Position of Hydraulic Cylinder static error can be controlled at ± 2 μ m within.

Claims (3)

1. the method for a dynamic compensation hydraulic pressure servo valve null shift, it is characterized in that installation position displacement sensor on the rolling mill hydraulic cylinder, oil pressure sensor and servovalve, read the displacement detecting and the fuel injection pressure signal of oil hydraulic cylinder by the PLC high-Speed Data-Acquisition Module, calculate the hydraulic pressure servo valve null shift compensation rate, control servovalve opening degree carries out the Position of Hydraulic Cylinder closed-loop adjustment.

2. the method for dynamic compensation hydraulic pressure servo valve null shift as claimed in claim 1, the calculating that it is characterized in that described hydraulic pressure servo valve null shift compensation rate be according to the following steps:

Step 1, the stable output quantity of observing HAPC, the drift scope of clear and definite servovalve, the amplitude limit value of definite hydraulic pressure servo valve null shift compensation rate on this basis: upper limit HL is 0～10%, and lower limit LL is-10%～0;

Step 2, determine that accommodation coefficient α is 0.8～1;

Step 3, calculating i compensation rate constantly:

μ(i)＝lim(U(i-1)，HL，LL) (1)

Wherein U (i) is the i servovalve opening degree controlled quentity controlled variable constantly of hydraulic pressure APC algorithm;

Step 4, calculating i controlled quentity controlled variable output value constantly:

U(i)＝U _a(i)+αμ(i) (2)

That is: U (i)=U _a(i)+α μ (i)=U _a(i)+α lim (U (i-1), HL, LL) (3)

U wherein _a(i) be HAPC regulator i output value constantly.

3. the method for dynamic compensation hydraulic pressure servo valve null shift as claimed in claim 1 is characterized in that recurrence formula U (i)=U in the step 4 _a(i)+α lim (LL), concrete calculation procedure is as follows for U (i-1), HL:

The first step: U (0)=U _a(0);

Second step: U (1)=U _a(1)+and α lim (U (0), HL, LL);

The 3rd step: U (2)=U _a(2)+and α lim (U (1), HL, LL);

……

The i step: U (i)=U _a(i)+and α lim (U (i-1), HL, LL).

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