阅读说明：本技术 对称不均等的负叠合比例阀控非对称缸系统的控制方法 (Control method of asymmetric negative superposition proportional valve control asymmetric cylinder system ) 是由 曾乐 李红章 刘金荣 许文斌 杨俊� 谭建平 于 2021-07-14 设计创作，主要内容包括：本发明提供一种对称不均等的负叠合比例阀控非对称缸系统的控制方法,包括以下步骤：获取基于模型变换的对称不均等的负叠合比例阀控非对称缸系统的输入信号；对输入信号进行补偿得到补偿后的输入信号,具体是：获取该系统在零速状态时的输入信号；基于零速状态时的输入信号获取对称不均等的负叠合比例阀控非对称缸系统的补偿信号；结合输入信号和补偿信号获得补偿后的输入信号。应用本发明的技术方案,推导了对称不均等负叠合的阀控非对称缸系统理论零点模型,在阀控非对称缸系统的模型变换控制基础上提出了零点在线补偿控制方法,使得阀控非对称缸系统的响应对称,且消除了零点偏移导致的稳态误差,有效提高比例阀控非对称缸系统的控制精度。(The invention provides a control method of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry, which comprises the following steps: acquiring input signals of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry based on model transformation; the input signal is compensated to obtain a compensated input signal, specifically: acquiring an input signal of the system in a zero-speed state; acquiring compensation signals of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry based on input signals in a zero-speed state; the compensated input signal is obtained by combining the input signal and the compensation signal. By applying the technical scheme of the invention, a theoretical zero point model of the valve control asymmetric cylinder system with asymmetric negative superposition is deduced, and a zero point online compensation control method is provided on the basis of model transformation control of the valve control asymmetric cylinder system, so that the response of the valve control asymmetric cylinder system is symmetric, steady-state errors caused by zero point offset are eliminated, and the control precision of the proportional valve control asymmetric cylinder system is effectively improved.)

1. A control method of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry is characterized by comprising the following steps:

obtaining the output of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry based on model transformationIncoming signal u_i；

For input signal u_iThe input signal after compensation is obtained, specifically:

obtaining an input signal u of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry and in a zero-speed state₀；

Based on input signal u at zero speed state₀Obtaining a compensation signal delta u of a negative superposition proportion valve control asymmetric cylinder system with asymmetric symmetry_i；

Combining the input signals u_iAnd the compensation signal Deltau_iA compensated input signal u' is obtained.

2. The method of claim 1, wherein the input signal u of the asymmetric negative overlap proportional valve controlled asymmetric cylinder system based on model transformation is obtained_iThe method comprises the following steps: and the asymmetric mathematical model of the asymmetric negative superposition proportion valve control asymmetric cylinder system with unequal symmetry is converted into a symmetric system model by utilizing a conversion transfer function, so that the symmetric change of the load flow model is realized, and the forward and reverse motions are correspondingly consistent when a unified controller is adopted.

3. The method of claim 2, wherein the input signal u of the asymmetric negative overlap proportional valve controlled asymmetric cylinder system at zero speed is obtained₀The method comprises the following steps: detecting the working pressure of two cavities of the hydraulic cylinder of the asymmetrical negative superposition proportional valve control cylinder system with unequal symmetry by a pressure sensor, and calculating the dimensionless quantity of the displacement of the proportional valve by adopting an expression 11)

Wherein: eta is the ratio of the area of the rod cavity of the hydraulic cylinder to the area of the rodless cavity;is a dimensionless quantity of load pressure of a symmetrical and unequal negative superposition proportion valve control asymmetric cylinder system,p_Ssupply pressure of a hydraulic cylinder being a proportional valve, p₁Pressure of rodless chambers of hydraulic cylinders, p₂The pressure of a rod cavity of the hydraulic cylinder; chi is the asymmetry of the superposition amount of the proportional valve;

dimensionless quantity combined with proportional valve displacementIs defined as expression 6) to obtain the input signal u of the asymmetrical negative superposition proportion valve control asymmetrical cylinder system in the zero-speed state₀Is expression 12):

wherein: delta₂Is the displacement of the proportional valve; x is the number of_VIs the displacement of the proportional valve core; u. of₂Representing the displacement of the proportional valve as Δ₂The input signal of (1).

4. The method of claim 3, wherein the MA is satisfied by the moving average_t< gamma and the absolute value of the systematic error abs (e) < e₀Under the condition of (1), the compensation signal Deltau_iAdopting expression 14) to obtain:

Δu_i＝(u₀+k∫edt) 14)；

wherein: Δ u_iIs a compensation signal of the proportional valve, k is an integral constant, t is time, and e is a system error; moving average MA_tExpressed by expression 13), e_tThe system error value, e, collected for the current period of time t_t-(n-1）TThe system error value of the (n-1) th period before the time T, T is sampling time, and n is sampling times;

5. the method for controlling a negatively-congruent, proportionally-controlled, asymmetric cylinder system according to claim 4, characterized in that the compensated input signal u' is obtained using expression 15):

u’＝u_i+Δu_i 15)。

Technical Field

The invention relates to the technical field of mechanical electronics, in particular to a control method of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry.

Background

The electro-hydraulic servo system has wide application in real life. The proportional valve changes the flow area of the throttling port through the relative movement of the valve sleeve and the valve core, and controls the pressure and the flow of liquid flow. The pre-opening forms of the valve sleeve and the valve core can be divided into a negative opening (positive overlapping), a zero opening (zero overlapping) and a positive opening (negative overlapping), because the electro-hydraulic proportional valve has the influence of factors such as overlapping amount, temperature, pressure and the like, the zero-speed balance point of the proportional valve control hydraulic cylinder system is not at the zero position of the proportional valve generally, and the system has larger steady-state error by adopting a control strategy commonly used in the industry.

Aiming at the problems that a proportional valve has a large dead zone, and the range of the dead zone is influenced by pressure, temperature and the like and changes within a certain range, the conventional research is mainly as follows: wang Qingfeng and the like put forward variable dead zone self-learning compensation control, indirectly target system positioning errors, judge whether to reach expected positioning accuracy by on-line search by using a self-learning mechanism, and further determine a compensation value; in 1999, Pengxieg and the like select a dead zone compensation initial value, and seek a proper dead zone compensation correction amount by a dead zone compensation self-learning algorithm according to the error and error change characteristic information in the dynamic response process of the system by taking the positioning accuracy as a target; in 2018, the Pengxiewei and other designs can adjust the fuzzy dead zone compensation algorithm of the dead zone compensation quantity on line based on errors and error change rates, and the comprehensive use of the iterative learning algorithm and the fuzzy dead zone compensation algorithm is to flexibly adjust the control quantity according to the current control experience, so that the influence caused by the nonlinearity and the timely degeneration of the system is effectively improved. When fuzzy dead zone compensation is added, the hysteresis of system position tracking is greatly improved, and the control performance of the system is improved.

However, the current research mainly aims at the electro-hydraulic proportional valve with positive superposition, a flow dead zone caused by the positive superposition is directly subtracted in the control, the control method is simple, and for the zero position of the proportional valve with the negative superposition, the zero position of the proportional valve changes along with the system pressure, the pressure of two cavities of a hydraulic cylinder and the oil temperature, the zero point research on the proportional valve control asymmetric cylinder system with the negative superposition is less. Therefore, the control method which aims at the asymmetrical negative superposition proportion valve control asymmetric cylinder system and can improve the system accuracy is significant.

Disclosure of Invention

The invention aims to provide a control method of a negative superposition proportional valve control asymmetric cylinder system with unequal symmetry, which is convenient and fast to operate and can effectively improve the control precision of the proportional valve control asymmetric cylinder system, and the specific technical scheme is as follows:

a control method of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry comprises the following steps:

obtaining an input signal u of a negative superposition proportion valve control asymmetric cylinder system based on model transformation and with unequal symmetry_i；

For input signal u_iThe input signal after compensation is obtained, specifically:

obtaining an input signal u of a negative superposition proportion valve control asymmetric cylinder system with unequal symmetry and in a zero-speed state₀；

Based on input signal u at zero speed state₀Obtaining a compensation signal delta u of a negative superposition proportion valve control asymmetric cylinder system with asymmetric symmetry_i；

Combining the input signals u_iAnd the compensation signal Deltau_iA compensated input signal u' is obtained.

In the invention, preferably, the input signal u of the asymmetric cylinder system with the negative superposition proportion valve control based on the asymmetric symmetry of model transformation is acquired_iThe method comprises the following steps: using transfer function of transformation to make asymmetryThe asymmetric mathematical model of the equal negative superposition proportional valve control asymmetric cylinder system is converted into a symmetric system model, so that the symmetric change of the load flow model is realized, and the positive and negative motions are correspondingly consistent when a unified controller is adopted.

In the invention, preferably, the input signal u of the asymmetrical negative superposition proportion valve-controlled asymmetric cylinder system in the zero-speed state is acquired₀The method comprises the following steps: detecting the working pressure of two cavities of the hydraulic cylinder of the asymmetrical negative superposition proportional valve control cylinder system with unequal symmetry by a pressure sensor, and calculating the dimensionless quantity of the displacement of the proportional valve by adopting an expression 11)

Wherein: eta is the ratio of the area of the rod cavity of the hydraulic cylinder to the area of the rodless cavity;is a dimensionless quantity of load pressure of a symmetrical and unequal negative superposition proportion valve control asymmetric cylinder system,p_Ssupply pressure of a hydraulic cylinder being a proportional valve, p₁Pressure of rodless chambers of hydraulic cylinders, p₂The pressure of a rod cavity of the hydraulic cylinder; chi is the asymmetry of the superposition amount of the proportional valve;

dimensionless quantity combined with proportional valve displacementIs defined as expression 6) to obtain the input signal u of the asymmetrical negative superposition proportion valve control asymmetrical cylinder system in the zero-speed state₀Is expression 12):

wherein: delta₂Is the displacement of the proportional valve; x is the number of_VIs the displacement of the proportional valve core; u. of₂Representing the displacement of the proportional valve as Δ₂The input signal of (1).

In the present invention, it is preferable that the moving average MA is satisfied_t< gamma and the absolute value of the systematic error abs (e) < e₀Under the condition of (1), the compensation signal Deltau_iAdopting expression 14) to obtain:

Δu_i＝(u₀+k∫edt) 14)；

wherein: Δ u_iIs a compensation signal of the proportional valve, k is an integral constant, t is time, and e is a system error; moving average MA_tExpressed by expression 13), e_tThe system error value, e, collected for the current period of time t_t-(n-1)TThe system error value of the (n-1) th period before the time T, T is sampling time, and n is sampling times;

in the present invention, it is preferable that the compensated input signal u' is obtained by using expression 15):

u’＝u_i+Δu_i 15)。

by applying the technical scheme of the invention, a theoretical zero point model of the valve control asymmetric cylinder system with asymmetric negative superposition is deduced, and a zero point online compensation control method is provided on the basis of model transformation control of the valve control asymmetric cylinder system, so that the response of the valve control asymmetric cylinder system is symmetric, steady-state errors caused by zero point offset are eliminated, and the control precision of the proportional valve control asymmetric cylinder system is effectively improved.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic diagram of a proportional valve controlled asymmetric cylinder in an embodiment of the present invention;

FIG. 2 is a composite control block diagram of zero point on-line compensation and load flow inverse transformation in an embodiment of the invention;

FIG. 3 is a displacement response curve of the extension and retraction movements of the hydraulic cylinder for three conditions of prior art P control, prior art model transformation compensation P control, and the inventive compound compensation control (P control + zero compensation) at a pressure load of 4000N;

FIG. 4 is an enlarged view of the location b1 in FIG. 3;

FIG. 5 is an enlarged view of position c1 in FIG. 3;

FIG. 6 is a graph of the response of the displacement of the hydraulic cylinder under a pressure load of 4000N for both the PI control of the prior art and the composite compensation control of the present invention;

FIG. 7 is a displacement response curve of the extension and retraction movements of the hydraulic cylinder for three conditions of prior art P control, prior art model transformation compensation P control, and the inventive composite compensation control (P control + zero compensation) at a tensile load of 2000N;

FIG. 8 is an enlarged view of the location b2 in FIG. 7;

fig. 9 is an enlarged view of the position c2 in fig. 7.

Detailed Description

Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.

Example (b):

a control method for asymmetric negative superposition proportional valve control asymmetric cylinder system, which is the proportional valve control asymmetric cylinder of the asymmetric negative superposition proportional valve control asymmetric cylinder system (hereinafter referred to as the system for short)The schematic diagram is detailed in fig. 1, wherein: p is a radical of_SSupply pressure of a hydraulic cylinder being a proportional valve, p_RPressure for oil return, p₁Pressure of rodless chambers of hydraulic cylinders, p₂Pressure of the rod chamber of the cylinder, q₁Is the flow of the rodless chamber of the hydraulic cylinder, q₂Is the flow of the rod chamber of the hydraulic cylinder, x_VThe displacement of the proportional valve core, the displacement of the hydraulic rod and the displacement of the hydraulic cylinder are respectively shown in the specification, y and F.

Assuming that the valves are symmetrical unequal hydraulic proportional valves, i.e. the overlap of the throttling edges of the proportional valves is respectively delta₁And Δ₂。

In this embodiment, a block diagram of load flow inverse transformation control and zero-speed balance point online compensation control of the valve-controlled asymmetric cylinder system is shown in fig. 2, where: y is_dIs the desired displacement value; y is the actual displacement value; changing the values of the number gamma and k of the controller can adjust the performance of the controller. The control method of the embodiment comprises the following steps:

the method comprises the following steps of firstly, obtaining an input signal u of a negative superposition proportion valve control asymmetric cylinder system which is asymmetric and is based on model transformation, wherein the input signal u specifically comprises the following steps: and the asymmetric mathematical model of the asymmetric negative superposition proportion valve control asymmetric cylinder system with unequal symmetry is converted into a symmetric system model by utilizing a conversion transfer function, so that the symmetric change of the load flow model is realized, and the forward and reverse motions are correspondingly consistent when a unified controller is adopted. See patent application No. 201510197350.6 entitled control method of asymmetric electro-hydraulic proportional system based on model transformation. Based on the invention, the skilled person can realize the first step of operation, such as obtaining the output signal u through the adjustment of the PID controller, and obtaining the output signal u through the transformation of the load flow model_i。

Second step, for the input signal u_iCompensating to obtain a compensated input signal, comprising the following specific operations:

step 2.1, obtaining an input signal u of the asymmetrical negative superposition proportion valve control asymmetric cylinder system in the zero-speed state₀The method specifically comprises the following steps:

obtaining the flow of the proportional valve:

the flow rate of the rodless chamber is expression 1):

q₁＝a(p_S-p₁)^1/2(x_V+Δ₁)-a(p₁-p_R)^1/2(Δ₂-x_V) 1)；

wherein:C_dthe flow coefficient is rho, the density of an oil medium is rho, omega is the area gradient of the proportional valve, and the area gradients of all valve ports are assumed to be equal;

the flow into the lumen of the rod is:

q₂＝a(p_S-p₂)^1/2(Δ₂-x_V)＝a(p₂-p_R)^1/2(x_V+Δ₁) 2)；

when the piston of the hydraulic cylinder is static, the flow equation expression 1) of the rodless cavity and the flow equation expression 2) of the rodless cavity satisfy expression 3):

neglecting the pressure p of the tank_RWhen the valve core displacement is x_VWhen expression 3) is satisfied, the flow that two chambeies of pneumatic cylinder flowed into is zero, and the system is the zero-speed state, and the pressure in two chambeies of pneumatic cylinder adopts expression 4) to express this moment:

asymmetry of proportional valve overlap and dimensionless proportional valve displacementExpressed by expression 5) and expression 6):

when the system is in a zero-speed state, the displacement x of the proportional valve_VAt (-delta)₁,Δ₂) In accordance with expression 5) and expression

Equation 6) to obtain the dimensionless value of the proportional valve in the zero speed state of the system satisfying expression 7):

setting the dimensionless quantity of two-cavity pressure of hydraulic cylinder asBy dimensionless expression 4), the working pressures of the two control chambers of the available hydraulic cylinder are expressed by expression 8):

setting dimensionless quantity of system load pressureUsing expression 9):

wherein: eta is the ratio of the area of the rod cavity of the hydraulic cylinder to the area of the rodless cavity.

Substituting expression 9) into expression 8) to obtain expression 10):

the system load pressure dimensionless quantity can be obtained by detecting the system pressure and the working pressure of two cavities of the hydraulic cylinder through a pressure sensor, and the dimensionless quantity of the displacement of the proportional valve can be theoretically calculated to be an expression 11 according to the expression 10) and the range relation of the displacement of the valve in the zero-speed state of the system:

the displacement of the proportional valve is controlled by controlling the input voltage and the current magnitude, the displacement of the proportional valve is in proportional relation with the input signal, the input signal of the proportional valve is u, and the displacement of the proportional valve is delta₁Input signal of u₁Proportional valve displacement of Δ₂Input signal of u₂When the system is in a zero-speed state, the input signal of the proportional valve is u₀。

Obtaining the input signal u of the proportional valve in the zero-speed state of the system according to the expression 6) and the expression 11)₀As in expression 12):

step 2.2, based on the input signal u in the zero speed state₀Obtaining a compensation signal delta u of a negative superposition proportion valve control asymmetric cylinder system with asymmetric symmetry_iThe method specifically comprises the following steps:

in the system, because the valve opening is small, the flow state is laminar flow, the flow coefficient is greatly influenced by the pressure difference, and the actual zero-speed balance point and the theoretical zero-speed balance point have larger errors along with the change of the differential pressure value of the valve opening. And finding an accurate zero-speed balance point of the system, which needs to be obtained by online control compensation.

When the error gradually stabilizes, the zero point compensation control is started, and in order to judge the error variation trend, a moving average line of the absolute value of the error is introduced, as shown in expression 13):

wherein: e.g. of the type_tThe system error value (here, specifically, the displacement error value of the system) collected for the period of time t, e_t-(n-1)TAnd the error value of the n-1 th cycle at the moment T is shown, T is sampling time, and n is average sampling times. Moving average MA_tIs the average of n cycles before time t.

In order to increase the system response speed, it is not necessary to compensate the zero-speed balance point after the system error approaches the steady-state error, when the moving average MA_t< gamma and the absolute value of the systematic error abs (e) < e₀The system initiates zero compensation. In order to quickly find the zero-speed balance point, the feedback error is subjected to proportional integral on the basis of the calculated theoretical zero-speed balance point, and the steady-state error is gradually reduced through zero compensation control. The zero-speed balance point compensation function of the present embodiment is expressed by expression 14):

Δu_i＝(u₀+k∫edt) 14)；

wherein: Δ u_iAnd k is an integral constant, t is time, and e is a system error.

Step 2.3, combine input signal u_iAnd the compensation signal Deltau_iExpression 15) is adopted to obtain the compensated input signal u':

u’＝u_i+Δu_i 15)。

by adopting the above scheme, the performance of the composite control method of zero point online compensation and load flow inverse transformation is verified through the AMESIM simulation model in this embodiment, and the details are as follows:

the simulation model parameters were determined as shown in table 1:

TABLE 1 simulation model parameter statistics table

Parameter(s)	Numerical value	Parameter(s)	Numerical value
				Overflow pressure Mpa	5	Nominal rated pressure MPa of valve	3
Maximum pump flow L/min	20	Nominal rated flow L/min of valve	9
				Valve reference current mA	1	Viscous damping coefficient N.s/m	2000
Critical reynolds number of valve	1000	Valve frequency Hz	100
				Diameter m of rodless cavity	0.05	Amount of lamination Delta1	0.01
Rod diameter m	0.028	Amount of lamination Delta2	0.04
				Load mass kg	50	The rest(s)	By default

Setting the external pressure load to 4000N, the displacement response of the simulation model under the symmetric P control, the load flow conversion compensation P control and the composite compensation control (here, P control + zero point compensation) of the present invention scheme is as shown in fig. 3 (the displacement response of the present invention using PI control + zero point compensation is similar to the composite compensation control in fig. 3, and is not shown), where fig. 4-5 are partial enlarged views of fig. 3, and it can be known by referring to fig. 3-5:

as shown in fig. 3, under the load force of 4000N, the extension motion response of the symmetric P-controlled hydraulic cylinder is slower than the retraction motion response, and after compensation by inverse load flow transformation, the extension motion response time is reduced, the retraction motion response time is increased, and the extension and retraction motion response times are basically consistent. As shown in FIG. 4 and FIG. 5, due to the action of 4000N load force, the zero point of the system is shifted, the steady state error of 0.25mm exists in the hydraulic cylinder under the control of the symmetric P control and the load flow inverse transformation compensation P, and after the online compensation control of the zero speed balance point, the steady state error is better eliminated, and the error is controlled within 0.01 mm.

The P control has no integral I control, because the negative superposition causes the system to have steady-state error, the common integral I control can eliminate the steady-state error, the invention can eliminate the steady-state error of the system by carrying out zero compensation under the P control or the PI control, and compared with the prior art, the effect is obvious.

The steady-state error generated by zero offset is eliminated by adopting the PI controller, and the displacement response under load flow conversion compensation PI control in the prior art and composite control (P control + zero compensation) of the invention is compared, as shown in FIG. 6. The PI control can eliminate the steady-state error, but causes great overshoot of the system, and the zero compensation composite control overshoot of the invention is smaller, eliminates the steady-state error and has great advantages.

Setting the external tension load to 2000N, the displacement response of the simulation model under the symmetric P control, the load flow conversion compensation P control and the composite compensation control of the present invention scheme (here, P control + zero point compensation) is as shown in fig. 7 (the displacement response of the present invention using PI control + zero point compensation is similar to the composite compensation control in fig. 7), where fig. 8-9 are partially enlarged views of fig. 7, and it can be known by referring to fig. 7-9:

as shown in fig. 7, under the action of a tensile load of 2000N, the response of the extending motion of the hydraulic cylinder controlled symmetrically by P is slower than that of the retracting motion, and after compensation by inverse load flow transformation, the response time of the extending motion is reduced, the response time of the retracting motion is increased, and the response time of the extending motion and the response time of the retracting motion are basically consistent. As shown in the figures 8 and 9, due to the zero point offset of the system caused by the action of the 2000N tensile load, the steady-state error exists in the hydraulic cylinder under the symmetrical P control and the load flow inverse transformation compensation P control, and after the zero-speed balance point on-line compensation control, the steady-state error is better eliminated, and the error is controlled within 0.01 mm.

Under the condition that the external tension load is set to be 2000N, compared with the PI control (which can eliminate steady-state errors but has large overshoot) only (not shown), the scheme (P control or PI control plus zero compensation) of the invention can eliminate the steady-state errors and can control the overshoot to be smaller, and the method and the device have obvious progress compared with the prior art.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.