Background technology
Hydraulic loaded is bigger than electronic loading because of its power volume.Thereby acquisition widespread use.From loading formal division, according to the difference that loads object, hydraulic loaded can be divided into following three kinds of forms: for hydraulic valve carries out pressure-loaded; By hydraulic jack straight-line motion mechanism being carried out power loads; By hydraulic pump rotational motion mechanism being carried out moment of torsion loads.
The principle of carrying out pressure-loaded for hydraulic valve as shown in Figure 1, hydraulic valve 104 is connected the exit that is loaded valve 101, control the size that is loaded valve 101 top hole pressures by hydraulic valve 104, thereby finish pressure-loaded, can be connected the flow sensor 102 that is loaded between valve 101 and the hydraulic valve 104 and pressure transducer 103 detects respectively by the flow size of hydraulic valve and the size of on-load pressure by being arranged on.
Principle when loading for straight-line motion mechanism as shown in Figure 2, the hydraulic schematic diagram that Fig. 2 loads for electro-hydraulic proportional valve control hydraulic cylinder realizable force, as shown in the figure, this loading system comprises displacement transducer 201, oil cylinder 202, two electro-hydraulic proportional valves 203 and 204, two pressure transducers 205 and 206, four retaining valves 207,208,209 and 210 and solenoid directional control valve 211.Its course of work is, oil cylinder 202 by piston rod 212 be loaded mechanism 213 and be connected, under the pulling that is loaded mechanism 213, stretch out the withdrawal to-and-fro movement, the hydraulic oil at fuel feeding 1 place is by solenoid directional control valve 211, retaining valve 210 when oil cylinder 202 stretches out, enter into the rodless cavity of oil cylinder 202, play the effect of repairing, this moment, electro-hydraulic proportional valve 204 was inoperative; The hydraulic oil of oil cylinder 202 rod chambers is then got back to fuel tank through electro-hydraulic proportional valve 203, then can control the return pressure of oil cylinder 202 rod chambers by the pressure of control electro-hydraulic proportional valve 203, thereby play the effect that power loads, the size of force value can detect by pressure transducer 205.The hydraulic oil at fuel feeding 1 place enters into the rod chamber of oil cylinder 202 by solenoid directional control valve 211, retaining valve 209 when oil cylinder 22 withdrawals, plays the effect of repairing, and this moment, electro-hydraulic proportional valve 203 was inoperative; The hydraulic oil of oil cylinder 202 rodless cavities is then got back to fuel tank through electro-hydraulic proportional valve 204, then can control the return pressure of oil cylinder 202 rodless cavities by the pressure of control electro-hydraulic proportional valve 204, thereby play the effect that power loads, the size of force value can detect by pressure transducer 206.The movement velocity of the piston rod 212 of oil cylinder 202 can detect by displacement transducer 201.The size of loading force can multiply by its piston area and calculate by the pressure of hydraulic cylinder 202 working chambers, after the hydraulic cylinder parameter is determined, the size of loading force only by the pressure decision in hydraulic cylinder works chamber, then controlled by hydraulic valve 203 and 204 by the pressure in hydraulic cylinder works chamber.Displacement transducer 201 is used for detecting the displacement of piston rod 211, thereby tests the speed indirectly.
Principle when loading for rotational motion mechanism is loaded mechanism 301 and links to each other with hydraulic pump 303 by torque speed sensor 302 as shown in Figure 3.The size of loading moment of torsion can multiply by its rotating speed by the top hole pressure of hydraulic pump 303 and discharge capacity is calculated, after hydraulic pump 303 parameters and rotating speed thereof are determined, the size that loads moment of torsion is only determined by the top hole pressure of hydraulic pump 303, and the top hole pressure of hydraulic pump 303 is also controlled by hydraulic valve 305, and the top hole pressure of hydraulic pump 303 can detect by pressure transducer 304.
In above-mentioned as can be seen three kinds of loading forms, the size of loaded value finally all is that the size by hydraulic valve controlled pressure value realizes.
Under the prior art condition, the accurate control that wants to realize on-load pressure, loading force or load moment of torsion, hydraulic valve generally all is to select servo-valve for use.The advantage that adopts servo-valve is that the response speed of servo-valve is fast, and the Control current and the linearity between the output pressure of servo-valve are good, and the pressure resolution height is easy to realize high-precision closed-loop control.But the shortcoming that adopts servo-valve is that the cost of servo-valve will be far above general hydraulic valve, and the antipollution degree ability of servo-valve, the cleanliness of hydraulic oil is required high, is easy to contaminated obstruction, cisco unity malfunction.
If adopt general electro-hydraulic proportional valve,, can reduce cost greatly, and the electro-hydraulic proportional valve contamination resistance to the situation of contamination and plugging can not occur far above servo-valve because it is cheap.Severe nonlinear, the especially relation between these two are subjected to the influence of flow bigger but exist relatively between the Control current of electro-hydraulic proportional valve and the output pressure, and under different flows, the corresponding relation between Control current and the output pressure is also different.When pressure is carried out closed-loop control, pressure oscillations appears easily, and control accuracy is subjected to that fluctuations in discharge influences greatly, response speed waits shortcoming slowly.
Summary of the invention
The objective of the invention is for solving the accurate control problem of on-load pressure in the hydraulic loaded, loading force or loading moment of torsion, a kind of electro-hydraulic proportional valve loading method based on model is proposed, Control current by setting up proportioning valve under the different flow and the corresponding relation between the pressure, it is model, again according to the pressure control of model completed percentage valve, thereby improve control accuracy.
The technical solution adopted in the present invention may further comprise the steps:
Steps A, the Control Flow of setting up the different flow correspondence and the transformational relation between the pressure.Transformational relation between described Control Flow and the pressure adopts high order curve to express, and its expression formula is:
Wherein,
Be Control current,
Be pressure, { a
m, a
M-1..., a
0|
QBe the expression formula coefficient of high order curve, m is the exponent number of high order curve, |
QRepresent corresponding with flow, the coefficient difference of expression formula under the different flow.
The implementation procedure of steps A is as follows:
A1, division flow sub-range.If the maximum flow of described electro-hydraulic proportional valve is Q
Max, at 0~Q
MaxInterval range in, mark off i flow sub-range, i is the positive integer greater than 1.
A2, obtain modeling data.If the maximum drive current of described electro-hydraulic proportional valve is I
Max, at 0~I
MaxInterval range in, get j current point { I
0, I
1..., I
J-1, j is the positive integer greater than 1.
A3, in each flow sub-range, according to the j that an is got current point,, obtain the electro-hydraulic proportional valve pressure of each current point correspondence successively to j Control current of electro-hydraulic proportional valve input.Record and j Control current be one group of pressure value one to one, that is:
A4, set up model.According to j current point { I
0, I
1..., I
J-1And the pressure value of each flow sub-range correspondence
Adopt data fitting method, obtain
Expression formula
In the high order curve coefficient { a of each flow sub-range correspondence
m, a
M-1..., a
0.
A5, preservation model parameter.At each flow sub-range, the corresponding scope high order curve coefficient { a corresponding that preserves the flow sub-range with this flow sub-range
m, a
M-1..., a
0|
Q
The flow Q of electro-hydraulic proportional valve is passed through in step B, detection, obtains the transformational relation of this flow correspondence,
Detailed process is as follows:
The flow Q of described electro-hydraulic proportional valve is passed through in b1, detection.
In b2, the information of preserving in a5 step, search the flow sub-range that detects under the flow Q, obtain the expression formula coefficient corresponding with the flow sub-range that finds out;
Step C, the expression formula coefficient that b2 step is obtained are together with pressure to be loaded
Together, bring expression formula into
Calculate and apply described pressure to be loaded
Required Control current value
Step D, the described electro-hydraulic proportional valve of control produce the current value that step C calculates, thereby finish Loading Control one time.
Beneficial effect
By technical scheme of the present invention as seen, the present invention is by setting up model, can obtain accurate control circuit according to actual conditions, adopt this Control current to implement control, can finish high-precision pressure, power or moment of torsion Loading Control, and need not to use electrohydraulic servo valve, and greatly reduce and control cost, improved the antipollution degree of loading system.
Secondly, loading method provided by the invention is simple, does not have complicated computation process, and is less demanding to the arithmetic speed and the storage space of controller.
In addition, loading method provided by the invention only needs once the loaded value that can arrive setting to two Control Circulation, and response speed is very fast.
When adding compensation tache, control accuracy and speed are further enhanced.
Embodiment
The invention provides a kind of electro-hydraulic proportional valve loading method based on model, this method is set up the Control current of hydraulic proportion valve under the different flow and the transformational relation between the pressure in advance, it is model, choose the pressure control of corresponding model completed percentage valve according to actual flow, owing to adopt different models under the different situations, so control accuracy improves greatly.
Preferably,, eliminate the error of model, improve the pressure controling precision of electro-hydraulic proportional valve, shorten the response time by a feedback compensation link because may there be certain error in institute's established model.Satisfy the requirement that pressure, power or moment of torsion load.
Be explained in further detail below in conjunction with the preferred implementation of drawings and Examples the inventive method.
Electro-hydraulic proportional valve loading method process flow diagram based on model provided by the invention may further comprise the steps as shown in Figure 4:
Steps A, be based upon under the various flow Q Control current of electro-hydraulic proportional valve
With pressure
Between model
General equation
An available high order curve represents that its common version is:
In the formula (1), { a
m, a
M-1, a
0|
QBe the coefficient of high order curve, i.e. model parameter; " |
Q" expression corresponding with certain flow Q; The value of m determined by fitting result hereinafter described, and the value of general m is less than or equal at 4 o'clock and just can describes out model between Control current and the output voltage with higher precision
It is as follows that steps A is set up the concrete grammar of electro-hydraulic proportional valve transformational relation of Control current and pressure under different flow:
A1, division flow sub-range.If the maximum flow of electro-hydraulic proportional valve is Q
Max, at (0~Q
Max) in the interval range, mark off i flow sub-range, i.e. { (0~Q
1), [Q
2~Q
3) ..., [Q
N-1~Q
Max).The method of dividing the flow sub-range is as follows:
A11, for described electro-hydraulic proportional valve provides fixedly Control current, and establish zero and be the starting point of flow;
A12, make flow start from scratch, increase the flow Q by electro-hydraulic proportional valve gradually, observe the pressure of electro-hydraulic proportional valve correspondence under fixing Control current, when pressure variety meets pre-conditionedly, writing down the present flow rate value is Q
1, then think from the zero flow value to the present flow rate value to be first flow sub-range (0~Q
1), then with flow Q
1As the starting point in next flow sub-range, repeat this step a12, until arriving maximum flow Q
Max, determine to finish the division in all flow sub-ranges.
Wherein, described meeting pre-conditionedly is: the variable quantity of force value surpasses the setting number percent of described electro-hydraulic proportional valve maximum working pressure (MWP) value.
A2, obtain modeling data.If the maximum drive current of described electro-hydraulic proportional valve is I
Max, at 0~I
MaxInterval range in, get j current point { I
0, I
1..., I
J-1, j is a positive integer.Preferably, j is greater than 20.
A3, in each flow sub-range, according to the j that an is got current point,, obtain the electro-hydraulic proportional valve pressure of each current point correspondence successively to j Control current of electro-hydraulic proportional valve input.Record and j Control current be one group of pressure value one to one, that is:
A4, set up model.According to j current point { I
0, I
1..., I
J-1And the pressure value of each flow sub-range correspondence
Adopt data fitting method, obtain
Expression formula
In the high order curve coefficient { a of each flow sub-range correspondence
m, a
M-1..., a
0.
A5, preservation model parameter.At each flow sub-range, the corresponding scope high order curve coefficient { a corresponding that preserves the flow sub-range with this flow sub-range
m, a
M-1..., a
0|
Q
A preferred implementation method in a5 step is as follows:
In each flow sub-range, expression formula
Coefficient { a of corresponding high order curve
m, a
M-1..., a
0|
QPreserve with the form of two-dimensional array, for example be kept in the storer of digitial controller, digitial controller is to link to each other with electro-hydraulic
proportional valve 203 as shown in Figure 2, is used to control the parts of electro-hydraulic proportional valve electromagnet.The preservation form of two-dimensional array is:
Wherein W is the name of array, and its line number is n, the number in the flow sub-range of promptly being divided.Each row has m+2 element, and preceding two elements are preserved the scope in flow sub-range, and the m of a back element is preserved the coefficient of the high order curve of the interval correspondence of this flow.
After obtaining the relation between control electric current of electro-hydraulic proportional valve in the different flow sub-range and the pressure, just can use at controller.Following steps B~D can adopt controller to realize.
The flow Q of electro-hydraulic proportional valve is passed through in step B, detection, obtains the transformational relation of this flow correspondence,, obtains corresponding model that is, so that adopt the Control current of the Model Calculation flow correspondence of obtaining to be loaded.
Step B specifically comprises:
The flow Q of described electro-hydraulic proportional valve is passed through in b1, detection.
If flow sensor has been installed in the system, controller obtains the flow size by the electric signal of acquisition stream quantity sensor output.If flow sensor is not installed, then:
For the straight line force loading system, need size by displacement transducer indirect calculation outflow value.Concrete grammar is: controller is loaded the shift value of straight-line motion mechanism by the displacement transducer collection, when gathering shift value the s time, acquisition time and shift value is kept at variable T respectively
1And L
1In, when the s+1 time collection arrives constantly, earlier with variable T
1And L
1In value be saved in variable T respectively
2And L
2In, then the s+1 time collection value is saved in variable T respectively
1And L
1In, and according to formula
Calculate and be loaded the movement velocity v of straight-line motion mechanism within adjacent two sampling periods.And then, calculate the size of flow value by formula v * A according to the effective piston area A that is loaded straight-line motion mechanism.
For the rotary torque loading system, need size by speed probe indirect calculation outflow value.Concrete grammar is: controller is loaded the tachometer value of rotational motion mechanism by the speed probe collection, and it is kept among the variable ω, then according to the discharge capacity q that is loaded rotational motion mechanism, is calculated the size of flow value by formula ω * q.
B2, obtain model parameter.According to the numerical value of detected flow Q, in the information that step a5 preserves, search the affiliated flow sub-range of detected flow Q, obtain the coefficient { a of the high order curve corresponding with the flow sub-range that finds out
m, a
M-1..., a
0|
QSpecifically, this step pairing flow of query flows Q sub-range in two-dimensional array W.Thereby find out expression formula
Coefficient { a of corresponding high order curve under flow Q
m, a
M-1..., a
0|
Q
Coefficient { a of step C, high order curve that step B is obtained
m, a
M-1..., a
0|
QSet pressure with electro-hydraulic proportional valve
Substitution formula (1) calculates and applies set pressure
Required Control current
This Control current
Can be directly as controlled quentity controlled variable.
In addition, because may there be error in institute's established model, make the electric current that calculates
And there is certain error between the exact value I, causes electric current
The pressure that produces
And there is error between the accurate pressure P, as shown in Figure 5.Consider the existence of error, can be at electric current
The basis on add offset current I
c, as controlled quentity controlled variable I to electro-hydraulic proportional valve.Offset current I
cBe to determine that according to the pressure P of the actual output of electro-hydraulic proportional valve the method for determining is as follows:
Because P and exact value
Between error very little, promptly P just exists
Near, in the neighborhood of P, can regard the relation between the electric current of electro-hydraulic proportional valve and the pressure as linear relationship, therefore can adopt the method for local linearization to obtain offset current I
c, its formula is shown in (2).Fig. 6 is the synoptic diagram of local linearization.
In the formula (2), k is the linearization scale-up factor, its physical meaning be electro-hydraulic proportional valve control electric current with pressure curve at a slope at P place, can pass through curve
Ask inverse to obtain.
Therefore the relation between on-load pressure and the Control current I can be used formula (3) expression:
As can be seen, as long as obtain
Expression formula and compensation rate I
c, just can finish control to on-load pressure P, loading force F or loading moment of torsion N.For just the power that realizes for the Electro-hydraulic Proportional Control cylinder loads, need pass through relational expression
Loading force F is converted to the controlled pressure of electro-hydraulic proportional valve
Wherein A is the useful area of hydraulic cylinder piston.For the moment of torsion loading that the Electro-hydraulic Proportional Control hydraulic pump is realized, need pass through relational expression
To load moment of torsion N and be converted to electro-hydraulic proportional valve pressure
Wherein ω is the rotating speed of hydraulic pump, and q is the hydraulic pressure pump capacity.
Therefore, under the situation that increases compensation tache, further calculate offset current I
cStep, be specially:
Controller is by the actual output pressure value P of pressure transducer detection electro-hydraulic proportional valve, and this pressure value P is that last control applies the actual pressure of exporting in back.Calculate a
mP
m+ a
M-1P
M-1+ ... + a
1P+a
0|
QFirst order derivative at the P place, thus linearization scale-up factor k=ma obtained
mP
M-1+ (m-1) a
M-1P
M-2+ ... + a
1|
Q, { a wherein
m, a
M-1..., a
0The high order curve coefficient that uses step B to obtain.Calculate offset current I according to formula (2) then
c
With the electric current that obtains
And I
cAddition, the Control current I after being compensated is with its Control current as electro-hydraulic proportional valve.In this case, in step D,, control thereby finish once by the Control current after the current amplifier generation compensation of controller control electro-hydraulic proportional valve.
Step D, control electro-hydraulic proportional valve produce the current value that step C calculates, thereby finish Loading Control one time.
In sum, more than be preferred implementation of the present invention only, be not to be used to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.