Pressure Control Method of Hydraulic Cylinder System

Abstract

The present invention provides a pressure control method for a hydraulic cylinder system, including obtaining the flow parameters of the hydraulic cylinder, and calculating the oil flow of the oil flowing through the hydraulic cylinder according to the flow parameters; obtaining the pressure parameters of the pressure control valve and the oil parameters of the oil flowing through the hydraulic cylinder, and calculating the hydraulic force of the oil flowing through the hydraulic cylinder according to the oil flow, pressure parameters, and oil parameters; compensating the input current of the pressure control valve according to the hydraulic force and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to the compensation result. This scheme takes into account the hydraulic force, which is the cause of the nonlinearity between the actual pressure of the hydraulic cylinder and the input current of the pressure control valve, and compensates the input current of the pressure control valve according to the hydraulic force, which can improve the control accuracy of the pressure of the hydraulic cylinder.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic cylinder control, and in particular to a pressure control method for a hydraulic cylinder system. Background Art

[0002] Hydraulic cylinders are important actuators in hydraulic transmission systems, converting hydraulic energy into mechanical energy. Installing hydraulic cylinders on vehicles can provide excellent support and protection for the vehicle's power.

[0003] Most existing hydraulic cylinders are valve-controlled, meaning their oil supply circuits are controlled by valves, such as solenoid valves or slide valves. To ensure optimal control of hydraulic cylinders and smoother vehicle operation, major manufacturers have invested significant effort in pressure tracking control after the cylinders build pressure.

[0004] After the hydraulic cylinder is filled with oil, if the hydraulic cylinder does not move, the pressure response characteristics of the hydraulic cylinder are very close to the pressure-current response characteristics of the solenoid valve itself. Figure 1 When the hydraulic cylinder is stationary (the piston of the hydraulic cylinder does not move), the actual pressure of the hydraulic cylinder and the target pressure curve basically coincide. At this time, the pressure closed-loop control is performed based on the pressure sensor value, and the control accuracy is high. However, if the hydraulic cylinder moves during the pressure control process (for example, a single-acting spring-type hydraulic cylinder or a double-acting hydraulic cylinder will often move), the flow rate when the hydraulic cylinder moves will cause the solenoid valve or slide valve that drives the hydraulic cylinder to have a relatively large hydraulic force, resulting in the dynamic response characteristics between the input current and the control pressure deviating from the steady-state characteristics (that is, the current-pressure response characteristics when the hydraulic cylinder is stationary), resulting in poor hydraulic cylinder pressure control accuracy. Reference Figure 2 When the hydraulic cylinder moves (the piston of the hydraulic cylinder moves), as the acceleration of the piston movement increases, the actual pressure of the hydraulic cylinder will be greatly disturbed.

[0005] Therefore, the existing valve-controlled hydraulic cylinder can achieve high control accuracy when the hydraulic cylinder is stationary or moves very slowly through pressure closed-loop control based on pressure sensors. However, the pressure control accuracy of variable volume moving hydraulic cylinders is generally poor, especially when the hydraulic cylinder moves at a high speed. It often cannot meet the usage requirements. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem of poor pressure control accuracy of hydraulic cylinders in the prior art.

[0007] To solve the above problems, an embodiment of the present invention discloses a pressure control method for a hydraulic cylinder system, wherein the hydraulic cylinder system includes a hydraulic cylinder, which includes a cylinder body, a piston, and a hydraulic rod. The piston is movably arranged in an inner cavity of the cylinder body, and the hydraulic rod is connected to the piston; the hydraulic cylinder system also includes a pressure control valve, a control circuit, and an oil supply circuit, wherein the oil supply circuit includes a control valve oil supply circuit and a hydraulic cylinder oil supply circuit; the control valve oil supply circuit is connected to the oil inlet of the pressure control valve, and the two ends of the hydraulic cylinder oil supply circuit are respectively connected to the oil outlet of the pressure control valve and the hydraulic cylinder; the two ends of the control circuit are respectively connected to the pressure control valve and the hydraulic cylinder oil supply circuit; the pressure control method of the hydraulic cylinder system is used to control the pressure of the hydraulic cylinder; and the pressure control method of the hydraulic cylinder system includes the following steps:

[0008] S1: Obtain the flow parameters of the hydraulic cylinder and calculate the oil flow rate of the oil flowing through the hydraulic cylinder according to the flow parameters;

[0009] S2: Obtain the pressure parameters of the pressure control valve and the oil parameters of the oil flowing through the hydraulic cylinder, and calculate the hydraulic force of the oil flowing through the hydraulic cylinder based on the oil flow, pressure parameters, and oil parameters;

[0010] S3: Compensate the input current of the pressure control valve according to the hydraulic force and the preset compensation coefficient, and control the pressure of the hydraulic cylinder according to the compensation result.

[0011] The above scheme takes into account the hydraulic force that causes the nonlinearity between the actual pressure of the hydraulic cylinder and the input current of the pressure control valve. The input current of the pressure control valve is compensated according to the hydraulic force, which can improve the control accuracy of the pressure of the hydraulic cylinder.

[0012] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, in step S1, the flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder body and the actual displacement of the piston; and

[0013] Calculate the oil flow rate according to the following formula:

[0014]

[0015] Among them, Q is the oil flow rate, x is the actual displacement of the piston, and A is the cross-sectional area of ​​the inner cavity of the cylinder.

[0016] This solution calculates oil flow using the actual piston displacement and the cross-sectional area of ​​the cylinder's inner cavity, eliminating the need to measure the flow rate of oil flowing through the pressure control valve. This makes measurement more convenient and saves the cost of deploying a flow sensor. Furthermore, the actual piston displacement and the cross-sectional area of ​​the cylinder's inner cavity can both be accurately measured, improving the accuracy of the calculation.

[0017] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, in step S1, the flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder body, the calculated displacement of the piston, and the actual pressure of the hydraulic cylinder; and

[0018] Step S1 further includes the following steps:

[0019] S11: Obtaining a pressure-displacement characteristic curve of the hydraulic cylinder, and determining a calculated displacement of the piston based on the pressure-displacement characteristic curve of the hydraulic cylinder and the actual pressure of the hydraulic cylinder;

[0020] S12: Calculate the oil flow rate based on the cross-sectional area of ​​the inner cavity of the cylinder and the calculated displacement of the piston.

[0021] By adopting the above scheme, the calculated displacement of the piston is determined according to the pressure-displacement characteristic curve of the hydraulic cylinder, and the oil flow is further calculated based on the calculated displacement, without the need to arrange many sensors, thus saving costs.

[0022] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, in step S12, the oil flow rate is calculated according to the following formula:

[0023]

[0024] Among them, Q is the oil flow rate, x * is the calculated displacement of the piston, and A is the cross-sectional area of ​​the inner cavity of the cylinder.

[0025] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, in step S2, the pressure parameters include the jet angle of the pressure control valve and the pressure difference between the oil inlet and the oil outlet of the pressure control valve;

[0026] The oil parameters include the oil density corresponding to the current oil temperature of the oil flowing through the hydraulic cylinder; and

[0027] The fluid force is calculated according to the following formula:

[0028]

[0029] Among them, F jet is the hydraulic force, Q is the oil flow rate, θ is the jet angle of the pressure control valve, Δp is the pressure difference between the oil inlet and outlet of the pressure control valve, and ρ is the oil density.

[0030] By adopting the above scheme, the oil density corresponding to the current oil temperature of the oil flowing through the hydraulic cylinder, the jet angle of the pressure control valve, and the pressure difference between the oil inlet and oil outlet of the pressure control valve are comprehensively considered when calculating the hydraulic force, thereby improving the accuracy of the calculated hydraulic force.

[0031] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, step S3 includes the following steps:

[0032] S31: Determine the compensation electromagnetic force according to the fluid force and the preset compensation coefficient;

[0033] S32: Determine a first compensation current according to the compensation electromagnetic force, and compensate the input current of the pressure control valve according to the first compensation current.

[0034] By adopting the above scheme, the actual compensation effect is adjusted based on the hydraulic force combined with the compensation coefficient, which can avoid the impact on other sub-items in the original dynamic balance equation caused by directly adding hydraulic force compensation to the electromagnetic force of the solenoid valve current.

[0035] According to another specific embodiment of the present invention, the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention determines the compensation electromagnetic force according to the following formula:

[0036] F′ se =±K jet F jet

[0037] Among them, F′ se To compensate for the electromagnetic force, K jet is the compensation coefficient, ±F jet It is the hydraulic force. When the hydraulic force increases the pressure of the pressure control valve, the sign of the hydraulic force is -. When the hydraulic force decreases the pressure of the pressure control valve, the sign of the hydraulic force is +.

[0038] According to another specific embodiment of the present invention, the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, step S3 further includes the following steps:

[0039] S32': Obtain the target pressure and actual pressure of the hydraulic cylinder, and compensate the input current of the pressure control valve according to the target pressure and the actual pressure;

[0040] S33': Control the pressure of the hydraulic cylinder according to the compensation results in step S32 and step S32'.

[0041] By adopting the above solution, the input current of the pressure control valve is compensated according to the difference between the target pressure and the actual pressure of the hydraulic cylinder and the hydraulic force, thereby improving the accuracy of input current control.

[0042] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, step S32′ includes the following steps:

[0043] S321': determining a compensation pressure according to the target pressure and actual pressure of the hydraulic cylinder;

[0044] S322': determining a second compensation current according to the compensation pressure, and compensating the input current of the pressure control valve according to the second compensation current; and step S33' includes:

[0045] S331': determining a target current according to the target pressure and a preset pressure-current correspondence relationship;

[0046] S332 ′: Determine the actual input current of the pressure control valve according to the target current, the first compensation current, and the second compensation current.

[0047] According to another specific embodiment of the present invention, in the pressure control method of the hydraulic cylinder system disclosed in the embodiment of the present invention, the pressure control valve includes a solenoid valve and / or a power amplification slide valve.

[0048] The beneficial effects of the present invention are:

[0049] The present invention provides a pressure control method for a hydraulic cylinder system. The method first calculates the displacement of the hydraulic cylinder using a displacement sensor or an algorithm, and then calculates the oil flow rate in the hydraulic cylinder based on the displacement. Next, the hydraulic force is calculated based on the pressure differential between the oil inlet and outlet of a pressure control valve and the calculated oil flow rate. Next, the input current of the pressure control valve is compensated based on the hydraulic force. This compensates the input current of the pressure control valve based on the hydraulic force, taking into account the hydraulic force, which causes the nonlinearity between the actual pressure of the hydraulic cylinder and the input current of the pressure control valve. This method improves the control accuracy of the hydraulic cylinder's pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the control accuracy of the hydraulic cylinder when the piston is stationary in the prior art;

[0051] Figure 2 This is a schematic diagram of the control accuracy of the hydraulic cylinder piston during operation in the prior art;

[0052] Figure 3 1 is a flow chart of a pressure control method for a hydraulic cylinder system provided by an embodiment of the present invention;

[0053] Figure 4 1 is a structural diagram of a hydraulic cylinder system when the hydraulic cylinder provided by an embodiment of the present invention is a single-acting hydraulic cylinder directly driven by a solenoid valve;

[0054] Figure 5 1 is a structural diagram of a hydraulic cylinder system provided by an embodiment of the present invention when the hydraulic cylinder is a single-acting hydraulic cylinder driven by a solenoid valve and a power amplifying slide valve;

[0055] Figure 61 is a structural diagram of a hydraulic cylinder system when the hydraulic cylinder provided by an embodiment of the present invention is a solenoid valve directly driven double-acting hydraulic cylinder;

[0056] Figure 7 1. It is a structural diagram of a hydraulic cylinder provided by an embodiment of the present invention when the hydraulic cylinder is a double-acting hydraulic cylinder driven by a solenoid valve and a power amplifying slide valve;

[0057] Figure 8 This is a pressure closed-loop control diagram of a hydraulic cylinder system based on fluid power provided by an embodiment of the present invention.

[0058] Description of reference numerals:

[0059] 1. Hydraulic cylinder; 11. Cylinder body; 12. Piston; 13. Hydraulic rod; 2. Pressure control valve; 21. Solenoid valve; 22. Power amplifier slide valve; 3. Oil supply circuit; 31. Control valve oil supply circuit; 32. Hydraulic cylinder oil supply circuit; 4. Control circuit; a. Oil inlet; b. Oil outlet; 5. Pressure sensor; 6. Displacement sensor. DETAILED DESCRIPTION

[0060] The following is an explanation of the embodiments of the present invention by specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this embodiment. On the contrary, the purpose of introducing the invention in conjunction with the embodiment is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will contain many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0061] It should be noted that in this specification, similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0062] In the description of this embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0063] The terms “first”, “second”, etc. are only used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0064] In the description of this embodiment, it should be noted that, unless otherwise specified or limited, the terms "disposed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this embodiment based on specific circumstances.

[0065] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0066] In order to solve the problem of poor pressure control accuracy of hydraulic cylinders in the prior art, an embodiment of the present invention provides a pressure control method for a hydraulic cylinder system.

[0067] The pressure control method of the hydraulic cylinder system provided in this embodiment is used to control the pressure of the hydraulic cylinder.

[0068] Specifically, refer to Figure 3 The pressure control method of the hydraulic cylinder system provided in this embodiment includes the following steps:

[0069] S1: Obtain the flow parameters of the hydraulic cylinder and calculate the oil flow rate of the oil flowing through the hydraulic cylinder according to the flow parameters;

[0070] S2: Obtain the pressure parameters of the pressure control valve and the oil parameters of the oil flowing through the hydraulic cylinder, and calculate the hydraulic force of the oil flowing through the hydraulic cylinder based on the oil flow, pressure parameters, and oil parameters;

[0071] S3: Compensate the input current of the pressure control valve according to the hydraulic force and the preset compensation coefficient, and control the pressure of the hydraulic cylinder according to the compensation result.

[0072] The above solution first calculates the displacement of the hydraulic cylinder using a displacement sensor or an algorithm, and then calculates the oil flow rate based on the displacement. Next, the hydraulic force is calculated based on the pressure differential between the inlet and outlet of the pressure control valve and the calculated oil flow rate. Next, the pressure control valve input current is compensated based on the hydraulic force. This compensates for the pressure control valve input current based on the hydraulic force, which accounts for the nonlinearity between the actual pressure in the hydraulic cylinder and the input current of the pressure control valve. This improves the control accuracy of the hydraulic cylinder pressure by considering the hydraulic force, which contributes to the nonlinearity between the actual pressure in the hydraulic cylinder and the input current of the pressure control valve.

[0073] Next, refer to Figure 3-8 The pressure control method of the hydraulic cylinder system provided in this embodiment is described in detail.

[0074] First, combine Figure 4-7 The hydraulic cylinder system is described.

[0075] In this embodiment, the hydraulic cylinder system includes a hydraulic cylinder 1, which includes a cylinder body 11, a piston 12, and a hydraulic rod 13. The piston 12 is movably disposed in the inner cavity of the cylinder body 11, and the hydraulic rod 13 is connected to the piston 12.

[0076] The hydraulic cylinder system also includes a pressure control valve 2, an oil supply circuit 3, and a control circuit 4.

[0077] The oil supply circuit 3 includes a control valve oil supply circuit 31 and a hydraulic cylinder oil supply circuit 32. The control valve oil supply circuit 31 is connected to the oil inlet a of the pressure control valve 2. The two ends of the hydraulic cylinder oil supply circuit 32 are respectively connected to the oil outlet b of the pressure control valve 2 and the hydraulic cylinder 1. The two ends of the control circuit 4 are respectively connected to the pressure control valve 2 and the hydraulic cylinder oil supply circuit 32.

[0078] Preferably, in this embodiment, the pressure control valve 2 includes a solenoid valve 21 and / or a power amplification slide valve 22 .

[0079] That is, in this embodiment, the pressure control valve 2 is primarily used to control the oil pressure in the hydraulic cylinder 1. It can be a single solenoid valve 21, or it can be a combination of the solenoid valve 21 and the power amplification spool valve 22 to control the oil pressure in the hydraulic cylinder 1. The number of solenoid valves 21 and the power amplification spool valve 22 can be arbitrarily set, and this embodiment does not impose any limitation thereto.

[0080] Figure 4 1 is a structural diagram of a hydraulic cylinder system provided by an embodiment of the present invention. In the hydraulic cylinder system, the hydraulic cylinder is specifically a solenoid valve directly driven single-acting hydraulic cylinder.

[0081] In the hydraulic cylinder system composed of a solenoid valve directly driving a single-acting hydraulic cylinder, the solenoid valve 21 receives a control instruction and then controls the pressure of the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds it back to the controller for closed-loop control.

[0082] Figure 5 1 is a structural diagram of another hydraulic cylinder system provided by an embodiment of the present invention. In this hydraulic cylinder system, the hydraulic cylinder is specifically a single-acting hydraulic cylinder driven by a solenoid valve and a power amplifying slide valve.

[0083] In this hydraulic cylinder system consisting of a solenoid valve and a power-amplifying spool valve driving a single-acting hydraulic cylinder, the solenoid valve 21 and the power-amplifying spool valve 22 each have a corresponding oil supply circuit 3 and control circuit 4. The control valve oil supply circuit 31 of the solenoid valve 21 is connected to the oil inlet a of the solenoid valve 21. The control valve oil supply circuit 31 of the power-amplifying spool valve 22 is connected to the oil inlet a of the power-amplifying spool valve 22. The ends of the hydraulic cylinder oil supply circuit 32 are connected to the oil outlet b of the power-amplifying spool valve 22 and the hydraulic cylinder 1, respectively. The ends of the control circuit 4 of the solenoid valve 21 are connected to the oil outlet b of the solenoid valve 21 and the power-amplifying spool valve 22, respectively. The ends of the control circuit 4 of the power-amplifying spool valve 22 are connected to the power-amplifying spool valve 22 and the hydraulic cylinder oil supply circuit 32, respectively. A pressure sensor 5 is provided near the control circuit 4 of the power-amplifying spool valve 22.

[0084] Furthermore, the solenoid valve 21 receives the control command and outputs pressure to the power amplification slide valve 22, thereby controlling the pressure of the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds it back to the controller for closed-loop control.

[0085] Figure 6 1 is a structural diagram of another hydraulic cylinder system provided by an embodiment of the present invention. In this hydraulic cylinder system, the hydraulic cylinder is specifically a solenoid valve directly driven double-acting hydraulic cylinder.

[0086] In this hydraulic cylinder system consisting of a solenoid valve directly driving a double-acting hydraulic cylinder, two solenoid valves 21 are provided. Furthermore, the two solenoid valves 21 are connected to the left and right sides of the hydraulic cylinder 1, respectively, to control the hydraulic cylinder 1 from both sides. The control valve oil supply circuit 31 is connected to the oil inlet a of the solenoid valve 21, and the two ends of the hydraulic cylinder oil supply circuit 32 are connected to the oil outlet b of the solenoid valve 21 and the hydraulic cylinder 1, respectively. The two ends of the control circuit 4 are connected to the solenoid valve 21 and the hydraulic cylinder oil supply circuit 32, respectively. A pressure sensor 5 is provided near the hydraulic cylinder oil supply circuit 32. A displacement sensor 6 is provided near the hydraulic cylinder 1.

[0087] Furthermore, the solenoid valve 21 receives the control command and controls the pressure of the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds it back to the controller for closed-loop control. The displacement sensor 6 collects the displacement of the hydraulic cylinder 1 and feeds it back to the controller.

[0088] Figure 7 1 is a structural diagram of a hydraulic cylinder system provided by an embodiment of the present invention. In the hydraulic cylinder system, the hydraulic cylinder is specifically a double-acting hydraulic cylinder driven by a solenoid valve and a power amplification slide valve.

[0089] In this hydraulic cylinder system consisting of a solenoid valve and a power-amplifying spool valve driving a double-acting hydraulic cylinder, a solenoid valve 21, a power-amplifying spool valve 22, and a pressure sensor 5 are respectively disposed on either side of hydraulic cylinder 1. A displacement sensor 6 is disposed near hydraulic cylinder 1. The connection relationship is essentially the same as for a solenoid valve and a power-amplifying spool valve driving a single-acting hydraulic cylinder, and will not be further described in this embodiment.

[0090] Solenoid valve 21 receives control commands and outputs pressure to power amplifier spool valve 22, thereby controlling the pressure of hydraulic cylinder 1. Pressure sensor 5 collects the actual pressure of hydraulic cylinder 1 and feeds it back to the controller for closed-loop control. Displacement sensor 6 collects the displacement of hydraulic cylinder 1 and feeds it back to the controller.

[0091] Next, the pressure control method of the hydraulic cylinder system provided in this embodiment is described.

[0092] First, step S1 is executed to obtain the flow parameters of the hydraulic cylinder, and calculate the oil flow rate of the oil flowing through the hydraulic cylinder according to the flow parameters.

[0093] Taking into account the incompressibility of the oil, the flow rate flowing through the hydraulic cylinder through the solenoid valve or the power amplifier slide valve is approximately equal to the product of the movement speed of the piston and the cross-sectional area of ​​the inner cavity of the cylinder body.

[0094] This embodiment provides two methods for calculating oil flow rate.

[0095] First, the oil flow rate is calculated using the displacement sensor method.

[0096] Flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder and the actual displacement of the piston.

[0097] The cross-sectional area of ​​the inner cavity of the cylinder body specifically refers to the cross-sectional area of ​​the cylinder body of the hydraulic cylinder in the radial direction, which can be obtained through actual measurement.

[0098] The actual displacement of the piston refers to the displacement of the piston relative to its original position within the cylinder body of the hydraulic cylinder. It can be directly measured using a displacement sensor.

[0099] Specifically, the oil flow rate is calculated according to the following formula:

[0100]

[0101] Among them, Q is the oil flow rate, x is the actual displacement of the piston, and A is the cross-sectional area of ​​the inner cavity of the cylinder.

[0102] The above formula can also be understood as being obtained by the formula Q=V×A, where V is the moving speed of the piston in the hydraulic cylinder.

[0103] Second, the oil flow rate is obtained by estimation.

[0104] The flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder, the calculated displacement of the piston, and the actual pressure of the hydraulic cylinder.

[0105] Specifically, step S1 further includes the following steps:

[0106] S11: Obtaining a pressure-displacement characteristic curve of the hydraulic cylinder, and determining a calculated displacement of the piston based on the pressure-displacement characteristic curve of the hydraulic cylinder and the actual pressure of the hydraulic cylinder;

[0107] S12: Calculate the oil flow rate based on the cross-sectional area of ​​the inner cavity of the cylinder and the calculated displacement of the piston.

[0108] It should be noted that the pressure-displacement characteristic curve of a hydraulic cylinder is obtained by obtaining data on the displacement of several sets of hydraulic cylinders under a certain pressure and performing plotting, fitting, and other processing on the data. Specifically, the displacement of the hydraulic cylinder can be obtained by looking up data from a pressure sensor or by using the pressure-displacement characteristic curve.

[0109] The calculated displacement of the piston refers to the displacement of the piston corresponding to a certain pressure obtained through the pressure-displacement characteristic curve.

[0110] Furthermore, in step S12, the oil flow rate is calculated according to the following formula:

[0111]

[0112] Among them, Q is the oil flow rate, x * is the calculated displacement of the piston, x * =f(p), A is the cross-sectional area of ​​the inner cavity of the cylinder.

[0113] It should be noted that in this embodiment, for single-acting hydraulic cylinders, such as those driven directly by a solenoid valve and those driven by a solenoid valve and a power amplifier spool valve as described in the above embodiments, the piston displacement can be calculated solely based on the pressure-displacement characteristics of the hydraulic cylinder. However, for double-acting hydraulic cylinders, due to their more complex systems, not only the pressure-displacement characteristics of the hydraulic cylinder need to be considered, but also other characteristics such as oil density and pressure. The pressure-displacement characteristics and other characteristics are then used together to calculate the displacement of the hydraulic cylinder.

[0114] Next, step S2 is executed to obtain the pressure parameters of the pressure control valve and the oil parameters of the oil flowing through the hydraulic cylinder, and calculate the hydraulic force of the oil flowing through the hydraulic cylinder based on the oil flow, pressure parameters and oil parameters.

[0115] Specifically, the pressure parameters include the jet angle of the pressure control valve and the pressure difference between the oil inlet and the oil outlet of the pressure control valve.

[0116] Furthermore, the oil parameters include the oil density corresponding to the current oil temperature of the oil flowing through the hydraulic cylinder.

[0117] It should be explained that the jet angle of the pressure control valve is related to the valve port structural parameters and the opening amount of the valve port of the pressure control valve, which can be obtained through numerical simulation methods and will not be described in detail in this embodiment.

[0118] The differential pressure between the inlet and outlet of a pressure control valve is the difference between the pressure of the oil flowing through the inlet and the pressure of the oil flowing through the outlet. The pressure at the outlet of the pressure control valve is the value of a pressure sensor located near the control circuit. The pressure at the inlet of the pressure control valve can be measured using a pressure sensor or directly replaced by the target pressure of the hydraulic cylinder.

[0119] The oil density corresponding to the current oil temperature refers to the density of the oil corresponding to the current oil temperature. It can be obtained by collecting the oil temperature data and looking up the table.

[0120] More specifically, in this embodiment, the hydraulic force is calculated according to the following formula:

[0121]

[0122] Among them, F jet is the hydraulic force, Q is the oil flow rate, θ is the jet angle of the pressure control valve, Δp is the pressure difference between the oil inlet and outlet of the pressure control valve, and ρ is the oil density.

[0123] Thereafter, step S3 is executed to compensate the input current of the pressure control valve according to the hydraulic force and a preset compensation coefficient, and the pressure of the hydraulic cylinder is controlled according to the compensation result.

[0124] In this embodiment, the reason why the input current of the pressure control valve is compensated according to the hydraulic force is based on the balance principle of the pressure control valve, especially the solenoid valve.

[0125] The dynamic balance equation of the solenoid valve is as follows:

[0126] F se -D×v s -k s ×(x s +x0)-p×A s ±F jet =m s ×α s

[0127] Among them, F se is the electromagnetic force of the solenoid valve, which is the electromagnetic force corresponding to the open-loop target current calculated based on the steady-state target pressure-current table. D is the viscous damping coefficient of the solenoid valve core. vs k is the moving speed of the solenoid valve core, s is the spring stiffness coefficient of the solenoid valve, x s is the displacement of the solenoid valve core, x0 is the pre-compression of the spring in the solenoid valve, p is the control pressure (feedback pressure) of the solenoid valve, A s is the feedback cavity area of ​​the solenoid valve core, ±F jet The direction of the hydraulic force is always to make the valve core close. The pressure rises to - and the pressure drops to +. s is the mass of the solenoid valve core, α s It is the acceleration of the solenoid valve core.

[0128] Based on the dynamic balance equation of the solenoid valve, it can be seen that the main force in the balance equation is the electromagnetic force F. se and feedback pressure p×A s Balance. With no fluid power F jet Compared with the case where the hydraulic cylinder is not moving, it can be seen that under the premise that the dynamic damping force (small friction), inertia force (small mass) and spring force (small proportion) of the solenoid valve core can be ignored, the hydraulic force is the result of the control pressure p and the input current electromagnetic force F se The reason is nonlinearity. Therefore, compensating the hydraulic force can improve the hydraulic response performance.

[0129] Specifically, in this embodiment, step S3 includes the following steps:

[0130] S31: Determine the compensation electromagnetic force according to the fluid force and the preset compensation coefficient;

[0131] S32: Determine a first compensation current according to the compensation electromagnetic force, and compensate the input current of the pressure control valve according to the first compensation current.

[0132] More specifically, the compensation electromagnetic force is determined according to the following formula:

[0133] F′ se =±K jet F jet

[0134] Among them, F′ se To compensate for the electromagnetic force, K jet is the compensation coefficient, ±F jet It is the hydraulic force. When the hydraulic force increases the pressure of the pressure control valve, the sign of the hydraulic force is -. When the hydraulic force decreases the pressure of the pressure control valve, the sign of the hydraulic force is +.

[0135] Compensation coefficient K jet It is mainly related to the characteristics of the solenoid valve. jet Based on the compensation coefficient K jetAdjust the actual compensation effect to avoid the electromagnetic force F se Directly increase the hydraulic force F jet Compensation affects other sub-items in the original dynamic equilibrium equation.

[0136] It needs to be explained that F′ se is the electromagnetic force corresponding to the first compensation current.

[0137] It should be noted that, in this embodiment, step S3 further includes the following steps:

[0138] S32': Obtain the target pressure and actual pressure of the hydraulic cylinder, and compensate the input current of the pressure control valve according to the target pressure and the actual pressure;

[0139] S33': Control the pressure of the hydraulic cylinder according to the compensation results in step S32 and step S32'.

[0140] It should be explained that the target pressure of the hydraulic cylinder is a control target of the hydraulic cylinder drive obtained from the upstream control.

[0141] The actual pressure of the hydraulic cylinder refers to the real-time pressure of the hydraulic cylinder measured by the pressure sensor.

[0142] More specifically, step S32' includes the following steps:

[0143] S321': determining a compensation pressure according to the target pressure and actual pressure of the hydraulic cylinder;

[0144] S322 ′: determining a second compensation current according to the compensation pressure, and compensating the input current of the pressure control valve according to the second compensation current.

[0145] Step S33' includes:

[0146] S331': determining a target current according to the target pressure and a preset pressure-current correspondence relationship;

[0147] S332 ′: Determine the actual input current of the pressure control valve according to the target current, the first compensation current, and the second compensation current.

[0148] It should be noted that the compensation pressure is the difference between the target pressure and the actual pressure of the hydraulic cylinder. In certain embodiments, a certain adjustment coefficient may be combined based on the difference between the target pressure and the actual pressure.

[0149] The preset pressure-current correspondence refers to the current that drives the solenoid valve of a hydraulic cylinder under a specific pressure, which is related to the characteristics of the hydraulic cylinder and the solenoid valve.

[0150] It's also important to note that the input current of a pressure control valve refers to the control signal of the pressure control valve. The input of the pressure control valve is a current signal, and the output is a pressure signal. When the input current changes, the output pressure changes.

[0151] refer to Figure 8 The above control method provided in step S3 is described.

[0152] In this embodiment, the pressure of the hydraulic cylinder is controlled in a closed loop, with the target pressure of the hydraulic cylinder as the given quantity, the actual pressure of the hydraulic cylinder as the controlled quantity, the solenoid valve and the hydraulic cylinder as the control objects, and the actual pressure of the hydraulic cylinder is controlled by deviation control of the input current of the solenoid valve.

[0153] When controlling the solenoid valve, the target pressure is first determined to make the hydraulic cylinder's pressure response close to the solenoid valve's own pressure-current response characteristics. Then, the target current for controlling the solenoid valve is obtained by looking up the table based on the target pressure, which is also the solenoid valve's input current.

[0154] Then, the hydraulic force of the oil flowing through the hydraulic cylinder needs to be calculated according to the displacement of the hydraulic cylinder, and a first compensation current is generated according to the calculated hydraulic force. The first compensation current is added or subtracted from the input current of the solenoid valve, that is, Figure 8 At the same time, it is also necessary to calculate the difference between the actual pressure of the hydraulic cylinder and the target pressure, and generate a second compensation current based on the pressure difference, and add the second compensation current to the input current of the solenoid valve, that is, Figure 8 The current determined by combining the input current of the solenoid valve, the first compensation current, and the second compensation current is the final input current of the solenoid valve.

[0155] By controlling the solenoid valve with this final input current, the pressure of the hydraulic cylinder can be controlled.

[0156] Although the present invention has been illustrated and described with reference to certain preferred embodiments thereof, it should be understood by those skilled in the art that the above description is provided as a further detailed description of the present invention in conjunction with specific embodiments thereof, and that the specific implementation of the present invention is not limited to these descriptions. Those skilled in the art may make various changes in form and details, including simple deductions or substitutions, without departing from the spirit and scope of the present invention.

Claims

1. A pressure control method for a hydraulic cylinder system, characterized in that: The hydraulic cylinder system comprises a hydraulic cylinder, which comprises a cylinder body, a piston, and a hydraulic rod, wherein the piston is movably disposed in an inner cavity of the cylinder body, and the hydraulic rod is connected to the piston; and The hydraulic cylinder system further comprises a pressure control valve, a control circuit, and an oil supply circuit, wherein the oil supply circuit comprises a control valve oil supply circuit and a hydraulic cylinder oil supply circuit; the control valve oil supply circuit is connected to the oil inlet of the pressure control valve, and the two ends of the hydraulic cylinder oil supply circuit are respectively connected to the oil outlet of the pressure control valve and the hydraulic cylinder; the two ends of the control circuit are respectively connected to the pressure control valve and the hydraulic cylinder oil supply circuit; the pressure control method of the hydraulic cylinder system is used to control the pressure of the hydraulic cylinder; and The pressure control method of the hydraulic cylinder system comprises the following steps: S1: acquiring a flow parameter of the hydraulic cylinder, and calculating an oil flow rate of the oil flowing through the hydraulic cylinder according to the flow parameter; S2: obtaining a pressure parameter of the pressure control valve and an oil parameter of the oil flowing through the hydraulic cylinder, and calculating a hydraulic force of the oil flowing through the hydraulic cylinder according to the oil flow rate, the pressure parameter and the oil parameter; S3: Compensating the input current of the pressure control valve according to the hydraulic force and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to the compensation result.

2. The pressure control method of the hydraulic cylinder system according to claim 1, characterized in that: In step S1, the flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder and the actual displacement of the piston; and The oil flow rate is calculated according to the following formula: Wherein, Q is the oil flow rate, x is the actual displacement of the piston, and A is the cross-sectional area of ​​the inner cavity of the cylinder.

3. The pressure control method of the hydraulic cylinder system according to claim 1, characterized in that: In step S1, the flow parameters include the cross-sectional area of ​​the inner cavity of the cylinder body, the calculated displacement of the piston, and the actual pressure of the hydraulic cylinder; and The step S1 further comprises the following steps: S11: acquiring a pressure-displacement characteristic curve of the hydraulic cylinder, and determining a calculated displacement of the piston according to the pressure-displacement characteristic curve of the hydraulic cylinder and an actual pressure of the hydraulic cylinder; S12: Calculating the oil flow rate according to the cross-sectional area of ​​the inner cavity of the cylinder body and the calculated displacement of the piston.

4. The pressure control method of the hydraulic cylinder system according to claim 3, characterized in that: In step S12, the oil flow rate is calculated according to the following formula: Wherein, Q is the oil flow rate, x * is the calculated displacement of the piston, and A is the cross-sectional area of ​​the inner cavity of the cylinder.

5. The pressure control method of the hydraulic cylinder system according to claim 1, characterized in that: In step S2, the pressure parameters include the jet angle of the pressure control valve and the pressure difference between the oil inlet and the oil outlet of the pressure control valve; The oil parameters include the oil density corresponding to the current oil temperature of the oil flowing through the hydraulic cylinder; and The fluid force is calculated according to the following formula: Among them, F jet is the hydraulic force, Q is the oil flow rate, θ is the jet angle of the pressure control valve, Δp is the pressure difference between the oil inlet and the oil outlet of the pressure control valve, and ρ is the oil density.

6. The pressure control method of the hydraulic cylinder system according to claim 1, characterized in that: The step S3 comprises the following steps: S31: determining a compensation electromagnetic force according to the hydraulic force and the preset compensation coefficient; S32: determining a first compensation current according to the compensation electromagnetic force, and compensating an input current of the pressure control valve according to the first compensation current.

7. The pressure control method of the hydraulic cylinder system according to claim 6, characterized in that: The compensation electromagnetic force is determined according to the following formula: F′ se =±K jet F jet Among them, F′ se is the compensation electromagnetic force, K jet is the compensation coefficient, ±F jet is the hydraulic force. When the hydraulic force increases the pressure of the pressure control valve, the sign of the hydraulic force is -. When the hydraulic force decreases the pressure of the pressure control valve, the sign of the hydraulic force is +.

8. The pressure control method of the hydraulic cylinder system according to claim 7, characterized in that: The step S3 further comprises the following steps: S32': acquiring the target pressure and the actual pressure of the hydraulic cylinder, and compensating the input current of the pressure control valve according to the target pressure and the actual pressure; S33': Control the pressure of the hydraulic cylinder according to the compensation results in step S32 and step S32'.

9. The pressure control method of the hydraulic cylinder system according to claim 8, characterized in that: The step S32' comprises the following steps: S321': determining a compensation pressure according to the target pressure and the actual pressure of the hydraulic cylinder; S322': determining a second compensation current according to the compensation pressure, and compensating the input current of the pressure control valve according to the second compensation current; and The step S33' comprises: S331': determining a target current according to the target pressure and a preset pressure-current correspondence relationship; S332': Determine the actual input current of the pressure control valve according to the target current, the first compensation current, and the second compensation current.

10. The pressure control method of a hydraulic cylinder system according to any one of claims 1 to 9, characterized in that: The pressure control valve includes a solenoid valve and / or a power amplification slide valve.

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