CN110671373A - An electro-hydraulic control system for controlling hydraulic cylinders in parallel with two valves - Google Patents

Abstract

The invention provides an electro-hydraulic control system for controlling hydraulic cylinders in parallel with double valves. It includes hydraulic cylinder, electro-hydraulic proportional governor, electro-hydraulic servo valve, controller, load, piston rod, and force sensor. Among them, the electro-hydraulic proportional speed regulating valve and the electro-hydraulic servo valve are connected in parallel and controlled by the controller. After the pressure sensor detects the pressure of the piston rod, it transmits the feedback signal to the controller, and the controller adjusts the input signals of the two valves, thereby achieving the purpose of controlling the hydraulic cylinder. The electro-hydraulic control system of the double-valve parallel control hydraulic cylinder provided by the invention can well improve the rapidity and stability of the electro-hydraulic control system, and can also improve the frequency response of the electro-hydraulic control system and eliminate excessive spare capacity, reduce costs, etc.

Description

An electro-hydraulic control system for controlling hydraulic cylinders in parallel with two valves

technical field

The invention mainly relates to some material testing machines, structural fatigue testing machines, wheel braking devices, etc., and mainly relates to an electro-hydraulic control system for controlling hydraulic cylinders in parallel with two valves.

Background technique

Electro-hydraulic servo control system is still very important in actual production.

With the continuous development of science and technology, higher standards have been put forward for the electro-hydraulic servo control systems in some engineering practices. For the active power control system that we are more familiar with, the system is required to have higher standards. Accuracy, rapidity and stability, and because the electro-hydraulic servo valve itself has a certain problem of low frequency response, in the process of force loading, excess force is often generated, and it is also required to further eliminate the existence of the system. excess force.

SUMMARY OF THE INVENTION

The invention provides an electro-hydraulic control system for controlling a hydraulic cylinder in parallel with two valves. By using an electro-hydraulic servo valve and an electro-hydraulic proportional speed regulating valve to be connected in parallel to control the hydraulic cylinder, the electro-hydraulic control can be well improved. The rapidity and stability of the system can also improve the frequency response of the electro-hydraulic control system, eliminate excess force, and reduce costs.

The invention provides an electro-hydraulic control system for controlling hydraulic cylinders in parallel with two valves, which is characterized by comprising: a hydraulic cylinder (1), a piston rod (2), an electro-hydraulic proportional regulator (3), an electro-hydraulic servo valve (4) ), pressure sensor (5), controller (6), fuel tank (7), pressure gauge (8), relief valve (9), oil pump (10), load (11).

Wherein, the piston rod (2) is located in the hydraulic cylinder (1); the pressure sensor (5) is located at the end of the piston rod (2); the load (11) is located after the pressure sensor (5); when the pressure sensor (5) detects the piston rod (2), the feedback signal is transmitted to the controller (6), and the controller (6) then controls the input signals of the electro-hydraulic proportional control valve (3) and the electro-hydraulic servo valve (4); the electro-hydraulic proportional control valve ( 3) It is connected in parallel with the electro-hydraulic servo valve (4); the output hydraulic oil of the electro-hydraulic proportional control valve (3) and the electro-hydraulic servo valve (4) is combined into the same pipeline as the hydraulic oil input end of the hydraulic cylinder (1). The oil pumping end of the oil pump (10) connects the oil pipe to the oil tank (7), and the hydraulic oil in the oil tank (7) is pumped as the input hydraulic oil to the electro-hydraulic proportional control valve (3) connected in parallel with the electro-hydraulic in the servo valve (4).

Description of drawings

In the attached image:

Figure 1 is a schematic diagram of the basic composition of an electro-hydraulic control system with only electro-hydraulic servo valves.

FIG. 2 is a schematic structural diagram of an electro-hydraulic control system for controlling hydraulic cylinders in parallel with dual valves according to the present invention.

FIG. 3 is a schematic diagram of a logic algorithm of an electro-hydraulic control system for controlling hydraulic cylinders in parallel with two valves according to the present invention.

The parameters and specifications of all the same components and loads of the different systems shown in Figure 1 and Figure 2 are the same.

Detailed ways

The following describes in detail an electro-hydraulic control system for controlling hydraulic cylinders in parallel with dual valves provided by the present invention with reference to the accompanying drawings.

Figure 1 is a schematic diagram of the basic composition of an electro-hydraulic control system with only an electro-hydraulic servo valve, including: a hydraulic cylinder (1), a piston rod (2), a load (3), an electro-hydraulic servo valve (4), a pressure sensor ( 5), controller (6), oil tank (7), pressure gauge (8), relief valve (9), oil pump (10). Wherein, the piston rod (2) is located in the hydraulic cylinder (1); the pressure sensor (5) is located at the end of the piston rod (2); the load (3) is located after the pressure sensor (5); when the pressure sensor (5) detects the piston rod After the pressure of (2), the feedback signal is transmitted to the controller (6), and the controller (6) further controls the input signal of the electro-hydraulic servo valve (4); the output hydraulic oil of the electro-hydraulic servo valve (4) is used as the hydraulic cylinder ( The hydraulic oil input end of 1); the oil pumping end of the oil pump (10) connects the oil pipe to the oil tank (7), and the hydraulic oil in the oil tank (7) is pumped as the input hydraulic oil to the electro-hydraulic servo valve (4) middle.

2 and 3, an electro-hydraulic control system provided by the present invention for controlling a hydraulic cylinder in parallel with two valves is described, which mainly includes: a hydraulic cylinder (1), a piston rod (2), an electro-hydraulic proportional regulator (3), electro-hydraulic servo valve (4), pressure sensor (5), controller (6), fuel tank (7), pressure gauge (8), relief valve (9), oil pump (10), load (11) ).

Wherein, the piston rod (2) is located in the hydraulic cylinder (1); the pressure sensor (5) is located at the end of the piston rod (2); the load (11) is located after the pressure sensor (5); when the pressure sensor (5) detects the piston rod (2), the feedback signal is transmitted to the controller (6), and the controller (6) then controls the input signals of the electro-hydraulic proportional control valve (3) and the electro-hydraulic servo valve (4); the electro-hydraulic proportional control valve ( 3) It is connected in parallel with the electro-hydraulic servo valve (4); the output hydraulic oil of the electro-hydraulic proportional control valve (3) and the electro-hydraulic servo valve (4) is combined into the same pipeline as the hydraulic oil input end of the hydraulic cylinder (1). The oil pumping end of the oil pump (10) connects the oil pipe to the oil tank (7), and the hydraulic oil in the oil tank (7) is pumped as the input hydraulic oil to the electro-hydraulic proportional control valve (3) connected in parallel with the electro-hydraulic in the servo valve (4).

After the system is started, the oil pump (10) extracts the hydraulic oil from the oil tank (7), and the hydraulic oil enters into the parallel electro-hydraulic proportional regulator (3) and the electro-hydraulic servo valve (4), respectively, from the electro-hydraulic proportional regulator ( 3) The hydraulic oil output by the electro-hydraulic servo valve (4) is used as the oil supply end of the hydraulic cylinder (1) to supply oil to the hydraulic cylinder (1), and the hydraulic oil enters the hydraulic cylinder and pushes the piston rod (2) to load the force. , the pressure sensor (5) at the front end of the piston rod (2) will convert the pressure into a voltage signal and transmit it to the controller (6). When the difference is small, the controller will close the electro-hydraulic servo speed regulating valve (3), and no longer supply oil, and the system pressure error will be compensated by the controller (6) through feedback adjustment to the electro-hydraulic servo valve (4) (smaller). The error is adjusted by the electro-hydraulic servo valve with higher precision), and the system has completed the work.

In the electro-hydraulic control system of the present invention, due to the addition of the electro-hydraulic proportional speed control valve, the displacement of the electro-hydraulic servo valve core is smaller than the displacement of the electro-hydraulic servo valve core of the system with only electro-hydraulic servo valves. The speed of reaching the designated spool position is improved, and the displacement of the electro-hydraulic servo valve spool that requires feedback adjustment is also small, so that the feedback adjustment can be realized more quickly, thereby achieving the purpose of improving the rapidity of the system.

Among them, for the parallel connection of the electro-hydraulic proportional speed control valve and the electro-hydraulic servo valve, the following special instructions need to be made:

1 is a schematic diagram of the composition of an electro-hydraulic control system with only electro-hydraulic servo valves. The difference between FIG. 2 and FIG. 1 is that the present invention is a parallel connection structure of an electro-hydraulic proportional speed control valve and an electro-hydraulic servo valve.

The parallel connection of the electro-hydraulic proportional speed control valve and the electro-hydraulic servo valve in Figure 2 is a combination for combining the advantages of the two valves.

Among them, because the electro-hydraulic proportional speed control valve has many advantages such as short start-up time, convenient operation and low cost, it can eliminate the problem of low frequency of some electro-hydraulic servo valves, realize the rapid start of the system, and eliminate excess force.

And the parallel connection of the electro-hydraulic proportional speed control valve and the electro-hydraulic servo valve can relieve the pressure of the electro-hydraulic servo valve. rapidity. The electro-hydraulic servo valve has high control accuracy, and is connected in parallel with the electro-hydraulic proportional speed control valve to jointly feed the hydraulic cylinder, which can complement each other well.

Since it is an electro-hydraulic control system, the load pressure gradually increases from zero during the loading process. For the system, using the electro-hydraulic proportional speed control valve, the speed stability of the system will be obtained to a certain extent. promote. In this system, the pressure difference between the front and rear ends of the throttle valve of the hydraulic oil through the electro-hydraulic proportional speed control valve is a constant value, which will reduce the influence of the system with the load change, so that the flow through the electro-hydraulic proportional speed control valve does not follow the pressure. For the electro-hydraulic control system in which the electro-hydraulic proportional speed regulating valve and the servo valve control the hydraulic cylinder in parallel, the stability of the system will be improved.

As shown in Figure 3, because the parallel connection of the electro-hydraulic proportional speed control valve and the electro-hydraulic servo valve is used to jointly feed oil into the hydraulic cylinder, the load pressure has the same effect on the two valves. When the flow equation of the valve is deduced, it will be found that it is the same as the derivation of the servo valve flow equation of the electro-hydraulic control system with only electro-hydraulic servo valve (Fig. 1). Complication, which is also a major point of the present invention.

The controller controls the flow rate and switch of the electro-hydraulic proportional speed control valve through the feedback signal. When the specified load pressure is reached, it will be closed, and the electro-hydraulic servo valve will perform feedback compensation.

The formula involved in the electro-hydraulic control system of the dual-valve parallel control hydraulic cylinder provided by the present invention is as follows:

Formula 1: U _e =U _r -U _f

Formula 2: U _f = K _fF F _g

Formula 3: Δi=K _a U _e

Formula 4: X _v =ΔiK _sv G _sv (s)

Formula 5: Q ₁ =K _q X _v -K _c p _L

Formula six:

Formula seven:

Formula eight:

Formula Nine,

Among them, in formula 1, U _e is the deviation voltage signal, U _f is the feedback voltage signal, and U _e is the input voltage signal; in formula 2, K _fF is the pressure sensor gain, and F _g is the hydraulic cylinder output force detected by the pressure sensor. ; In formula 3, Δi is the output current of the electro-hydraulic servo valve servo amplifier, and Ka is the gain of the electro-hydraulic servo valve amplifier; in formula 4, _{X v} is the electro-hydraulic servo valve spool of the electro-hydraulic control system shown in Figure 2 displacement, K _sv is the gain of the electro-hydraulic servo valve, G _sv (s) is the transfer function of the electro-hydraulic servo valve when K _sv is equal to 1; in formula 5, Q ₁ is the output flow of the electro-hydraulic servo valve, and K _q is the electrical hydraulic servo valve flow gain, K _c is the flow-pressure coefficient of the electro-hydraulic servo valve, p _L is the load pressure; in formula 6, _QL is the total input flow of the hydraulic cylinder, and Q ₂ is the output of the electro-hydraulic proportional speed control valve Flow, A _p is the effective area of the hydraulic cylinder piston, s is the Laplace operator, X _p is the piston displacement of the hydraulic cylinder, C _tp is the internal leakage coefficient of the hydraulic cylinder, V _t is the effective volume of the hydraulic cylinder, βe is The effective bulk elastic modulus of the hydraulic cylinder; in formula 7, is the displacement of the electro-hydraulic servo valve spool of the electro-hydraulic control system shown in Figure 1; in formula 8, F _g is the load pressure, m _t is the total mass of the piston and the load converted to the piston, and B _p is the piston and the load The viscous damping coefficient of , K is the load spring stiffness.

Equation 1 to Equation 4 are the basic knowledge of electro-hydraulic control system, which will not be elaborated here.

Formula 5 is the flow equation of the electro-hydraulic servo valve of the electro-hydraulic control system of the present invention.

Formula 6 is the hydraulic cylinder flow continuity equation of the electro-hydraulic control system of the present invention.

Formula 7 is the equivalent form of the flow continuity equation of the hydraulic cylinder of the electro-hydraulic control system with only electro-hydraulic servo valve and the hydraulic cylinder flow continuity equation of the electro-hydraulic control system of the present invention.

Formula 8 is the force balance equation between the hydraulic cylinder and the load of the electro-hydraulic control system of the present invention.

From formula 6 and formula 8, it can be concluded that when the load pressure and hydraulic cylinder parameters are equal, whether it is the system shown in Figure 1 or the system shown in Figure 2, the flow rate _QL of the hydraulic cylinder into the oil chamber is a fixed value.

为正确公式。From formula 5, formula 6, and formula 8, it can be concluded that, compared with the electro-hydraulic servo valve of the electro-hydraulic control system with only electro-hydraulic servo valve, the oil is supplied separately, because the present invention uses the electro-hydraulic proportional speed control valve and the electro-hydraulic servo valve. The hydraulic servo valves are connected in parallel, so that the flow _QL flowing into the oil inlet chamber of the hydraulic cylinder is provided by the electro-hydraulic servo valve and the electro-hydraulic proportional speed control valve. Formula seven:

is the correct formula.

Calculating formula 7, it can be obtained that formula 9:

From formula 9, it can be concluded that compared with the electro-hydraulic control system with only electro-hydraulic servo valve, the displacement of the electro-hydraulic servo valve spool of the electro-hydraulic control system of the present invention is smaller, so that when the system starts to run, the displacement of the electro-hydraulic servo valve is smaller. The displacement of the spool is reduced, which will further improve the loading speed of the system, and when the system performs feedback, it will also perform feedback compensation faster to improve the rapidity of the system.

Claims (3)

1. The invention discloses an electric hydraulic control system of a double-valve parallel control hydraulic cylinder, which is characterized by comprising the following components: the hydraulic system comprises a hydraulic cylinder (1), a piston rod (2), an electro-hydraulic proportional regulator (3), an electro-hydraulic servo valve (4), a pressure sensor (5), a controller (6), an oil tank (7), a pressure gauge (8), an overflow valve (9), an oil pump (10) and a load (11).

2. The electric hydraulic control system of the double-valve parallel control hydraulic cylinder as claimed in claim 1, wherein: the piston rod (2) is positioned in the hydraulic cylinder (1); the pressure sensor (5) is positioned at the tail end of the piston rod (2); the load (11) is located behind the pressure sensor (5); when the pressure sensor (5) detects the pressure of the piston rod (2), a feedback signal is transmitted to the controller (6), and the controller (6) further controls input signals of the electro-hydraulic proportional regulating valve (3) and the electro-hydraulic servo valve (4); the electro-hydraulic proportional regulating valve (3) is connected with the electro-hydraulic servo valve (4) in parallel; the output hydraulic oil of the electro-hydraulic proportional control valve (3) and the output hydraulic oil of the electro-hydraulic servo valve (4) are combined into the same pipeline and used as the hydraulic oil input end of the hydraulic cylinder (1); an oil pipe is connected into an oil tank (7) by an oil pumping end of an oil pump (10), and hydraulic oil in the oil tank (7) is pumped into an electro-hydraulic proportional regulating valve (3) and an electro-hydraulic servo valve (4) which are connected in parallel as input hydraulic oil.

3. The electric hydraulic control system of a double-valve parallel control hydraulic cylinder according to claim 1 and claim 2 is characterized by the following formula:

the formula I is as follows: u shape_e＝U_r-U_f

The formula II is as follows: u shape_f＝K_fFF_g

The formula III is as follows: Δ i ═ K_aU_e

The formula four is as follows: x_v＝ΔiK_svG_sv(s)

The formula five is as follows: q₁＝K_qX_v-K_cp_L

Formula six:

the formula seven:

the formula eight:

the formula is nine:

wherein, in the formula I, U_eIs a deviation voltage signal, U_fFor feedback of voltage signals, U_eIs an input voltage signal; in the second formula, K_fFIs a pressure sensorGain, F_gOutputting force for the hydraulic cylinder detected by the pressure sensor; in the third formula, Δ i is the output current of the servo amplifier of the electro-hydraulic servo valve, K_aGain of an electrohydraulic servo valve amplifier; in the formula IV, X_vThe displacement of the valve core of the electro-hydraulic servo valve of the electro-hydraulic force control system shown in FIG. 2, K_svIs an electro-hydraulic servo valve gain, G_sv(s) is K_svAn electro-hydraulic servo valve transfer function equal to 1; in the fifth formula, Q₁Is the output flow of the electro-hydraulic servo valve, K_qFor the flow gain of the electro-hydraulic servo valve, K_cFlow-pressure coefficient, p, of electrohydraulic servo valve_LIs the load pressure; in the sixth formula, Q_LIs the total input flow, Q, of the cylinder₂Is the output flow of the electro-hydraulic proportional speed regulating valve, A_pIs the effective area of the piston of the hydraulic cylinder, s is Laplace operator, X_pIs the piston displacement of the hydraulic cylinder, C_tpIs the internal leakage coefficient, V, of the hydraulic cylinder_tIs the effective volume of the hydraulic cylinder, and beta e is the effective volume elastic modulus of the hydraulic cylinder; in the formula seven, the first step is carried out,

the valve core displacement of an electro-hydraulic servo valve of the electro-hydraulic force control system shown in FIG. 1; in the eighth formula, F_gFor load pressure, m_tFor the total mass of the piston and the load converted to the piston, B_pIs the viscous damping coefficient of the piston and load, and K is the load spring rate.

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