CN115479058A - Pressure control method for hydraulic cylinder system - Google Patents
Pressure control method for hydraulic cylinder system Download PDFInfo
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- CN115479058A CN115479058A CN202110599499.2A CN202110599499A CN115479058A CN 115479058 A CN115479058 A CN 115479058A CN 202110599499 A CN202110599499 A CN 202110599499A CN 115479058 A CN115479058 A CN 115479058A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/044—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by electrically-controlled means, e.g. solenoids, torque-motors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/08—Servomotor systems incorporating electrically operated control means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/044—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by electrically-controlled means, e.g. solenoids, torque-motors
- F15B2013/0448—Actuation by solenoid and permanent magnet
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- General Engineering & Computer Science (AREA)
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- Analytical Chemistry (AREA)
- Fluid-Pressure Circuits (AREA)
Abstract
The invention provides a pressure control method of a hydraulic cylinder system, which comprises the steps of obtaining flow parameters of a hydraulic cylinder, and calculating the oil flow of oil flowing through the hydraulic cylinder according to the flow parameters; acquiring pressure parameters of a pressure control valve and oil parameters of oil flowing through the hydraulic cylinder, and calculating hydraulic power of the oil flowing through the hydraulic cylinder according to the oil flow, the pressure parameters and the oil parameters; and compensating the input current of the pressure control valve according to the hydraulic power and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to a compensation result. The scheme considers the reason of nonlinearity of the actual pressure of the hydraulic cylinder and the input current of the pressure control valve caused by hydraulic force, compensates the input current of the pressure control valve according to the hydraulic force, and can improve the control precision of the pressure of the hydraulic cylinder.
Description
Technical Field
The invention relates to the technical field of hydraulic cylinder control, in particular to a pressure control method of a hydraulic cylinder system.
Background
Hydraulic cylinders are important actuators in hydraulic transmission systems and are capable of converting hydraulic energy into mechanical energy. The hydraulic cylinder is arranged on the automobile, so that good support and guarantee can be provided for the power of the automobile.
Most of the existing hydraulic cylinders are valve-controlled hydraulic cylinders, namely, the on-off of an oil supply loop of the hydraulic cylinder is controlled by a valve, such as an electromagnetic valve or a slide valve. In order to control the hydraulic cylinder well so that the vehicle can run more smoothly, various manufacturers put much effort on the pressure following control after the hydraulic cylinder is pressurized.
After the hydraulic cylinder is filled with oil, if the hydraulic cylinder is not moved, the pressure response characteristic of the hydraulic cylinder is very close to the pressure-current response characteristic of the electromagnetic valve. Referring to fig. 1, when the hydraulic cylinder is stationary (the piston of the hydraulic cylinder does not move), the actual pressure and target pressure curves of the hydraulic cylinder substantially coincide. At the moment, pressure closed-loop control is performed according to the value of the pressure sensor, and the control precision 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 often moves), the flow rate of the hydraulic cylinder during the movement may cause a solenoid valve or a spool valve for driving the hydraulic cylinder to have a relatively large hydraulic force, which causes the dynamic response characteristic between the input current and the control pressure to deviate from the steady-state characteristic (i.e., the current-pressure response characteristic when the hydraulic cylinder is not moving), and thus, the result of poor control accuracy of the hydraulic cylinder pressure is presented. Referring to fig. 2, when the hydraulic cylinder moves (the piston of the hydraulic cylinder moves), the actual pressure of the hydraulic cylinder is greatly disturbed as the acceleration of the piston movement increases.
Therefore, the existing valve-controlled hydraulic cylinder can have higher control precision when the hydraulic cylinder is not in motion or has a very low moving speed through pressure closed-loop control based on a pressure sensor, the pressure control precision effect of the variable-volume moving hydraulic cylinder is general, and particularly when the hydraulic cylinder has a relatively high moving speed, the pressure control precision is very poor and the use requirement can not be met.
Disclosure of Invention
The invention aims to solve the problem of poor pressure control precision of a hydraulic cylinder in the prior art.
In order 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 comprises a hydraulic cylinder, the hydraulic cylinder comprises 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 with the piston; the hydraulic cylinder system also comprises a pressure control valve, a control loop and an oil supply loop, wherein the oil supply loop comprises a control valve oil supply loop and a hydraulic cylinder oil supply loop; the control valve oil supply loop is connected to an oil inlet of the pressure control valve, and two ends of the hydraulic cylinder oil supply loop are respectively connected with an oil outlet of the pressure control valve and the hydraulic cylinder; two ends of the control loop are respectively connected with the pressure control valve and the hydraulic cylinder oil supply loop; the pressure control method of the hydraulic cylinder system is used for controlling the pressure of the hydraulic cylinder; also, a pressure control method of a hydraulic cylinder system includes the steps of:
s1: acquiring flow parameters of the hydraulic cylinder, and calculating the oil flow of oil flowing through the hydraulic cylinder according to the flow parameters;
s2: acquiring pressure parameters of a pressure control valve and oil parameters of oil flowing through the hydraulic cylinder, and calculating hydraulic power of the oil flowing through the hydraulic cylinder according to the oil flow, the pressure parameters and the oil parameters;
s3: and compensating the input current of the pressure control valve according to the hydraulic power and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to a compensation result.
By adopting the scheme, the reason that the actual pressure of the hydraulic cylinder and the input current of the pressure control valve are nonlinear due to hydraulic force is considered, the input current of the pressure control valve is compensated according to the hydraulic force, and the control precision of the pressure of the hydraulic cylinder can be improved.
According to another specific embodiment of the present invention, in the method for controlling the pressure of the hydraulic cylinder system according to the embodiment of the present invention, in step S1, the flow parameter includes a cross-sectional area of an inner cavity of the cylinder body and an actual displacement of the piston; and is
Calculating the oil flow according to the following formula:
wherein Q is the oil flow, x is the actual displacement of the piston, and A is the cross-sectional area of the inner cavity of the cylinder.
By adopting the scheme, the oil flow is calculated by utilizing the actual displacement of the piston and the cross-sectional area of the inner cavity of the cylinder body, the flow of the oil flowing through the pressure control valve is not required to be measured, the measurement is more convenient, and the cost for arranging the flow sensor is also saved. In addition, accurate values can be actually measured according to the actual displacement of the piston and the cross-sectional area of the inner cavity of the cylinder body, and the calculation accuracy is improved.
According to another specific embodiment of the present invention, in the method for controlling pressure of a hydraulic cylinder system according to the embodiment of the present invention, in step S1, the flow parameter includes a cross-sectional area of an inner cavity of the cylinder body, a calculated displacement of the piston, and an actual pressure of the hydraulic cylinder; and is
Step S1 further comprises the steps of:
s11: acquiring a pressure displacement characteristic curve of the hydraulic cylinder, and determining the calculated displacement of the piston according to the pressure displacement characteristic curve of the hydraulic cylinder and the actual pressure of the hydraulic cylinder;
s12: and calculating the oil flow according to the cross-sectional area of the inner cavity of the cylinder body and the calculated displacement of the piston.
By adopting the scheme, the calculation displacement of the piston is determined according to the pressure displacement characteristic curve of the hydraulic cylinder, the oil flow is further calculated according to the calculation displacement, a plurality of sensors are not required to be arranged, and the cost is saved.
According to another embodiment of the present invention, in the method for controlling the pressure of the hydraulic cylinder system according to the embodiment of the present invention, in step S12, the oil flow rate is calculated according to the following formula:
wherein Q is oil flow, x * For the calculated displacement of the piston, A is the cross-sectional area of the inner cavity of the cylinder.
According to another specific embodiment of the present invention, in the method for controlling pressure of a hydraulic cylinder system disclosed in the embodiment of the present invention, in step S2, the pressure parameter includes a jet angle of the pressure control valve, and a pressure difference between an oil inlet and an oil outlet of the pressure control valve;
the oil parameters comprise oil density corresponding to the current oil temperature of oil flowing through the hydraulic cylinder; and is
The hydrodynamic force is calculated according to the following formula:
wherein, F jet The hydraulic power is adopted, Q is the oil flow, theta is the jet flow angle of the pressure control valve, delta p is the pressure difference between an oil inlet and an oil outlet of the pressure control valve, and rho is the oil density.
By adopting the 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 the oil outlet of the pressure control valve are comprehensively considered during calculation of the hydraulic power, and the accuracy of the calculated hydraulic power is improved.
According to another specific embodiment of the present invention, in the method for controlling the pressure of the hydraulic cylinder system according to the embodiment of the present invention, the step S3 includes the steps of:
s31: determining a compensation electromagnetic force according to the hydrodynamic force and a preset compensation coefficient;
s32: a first compensation current is determined based on the compensation electromagnetic force and an input current of the pressure control valve is compensated based on the first compensation current.
By adopting the scheme, the effect of actual compensation is adjusted by combining the compensation coefficient on the basis of the hydraulic power, so that the influence on other subentries in the original dynamic balance equation due to the fact that the hydraulic power compensation is directly added to the current electromagnetic force of the electromagnetic valve can be avoided.
According to another embodiment of the present invention, a method for controlling a pressure of a hydraulic cylinder system according to an embodiment of the present invention determines a compensation electromagnetic force according to the following formula:
F′ se ＝±K jet F jet
wherein, F' se To compensate for electromagnetic forces, K jet To compensate for the coefficient, ± F jet The hydraulic power is adopted, when the hydraulic power enables the pressure of the pressure control valve to rise, the sign of the hydraulic power is negative, when the hydraulic power enables the pressure of the pressure control valve to fall, the sign of the hydraulic power is positive.
According to another specific embodiment of the present invention, in the method for controlling a pressure of a hydraulic cylinder system according to the embodiment of the present invention, the step S3 further includes the steps of:
s32': acquiring target pressure and actual pressure of a hydraulic cylinder, and compensating the input current of a pressure control valve according to the target pressure and the actual pressure;
s33': the pressure of the hydraulic cylinder is controlled according to the compensation results in step S32 and step S32'.
By adopting the scheme, the input current of the pressure control valve is compensated together according to the difference value of the target pressure and the actual pressure of the hydraulic cylinder and the hydraulic power, so that the accuracy of controlling the input current is improved.
According to another embodiment of the present invention, in the method for controlling the pressure of the hydraulic cylinder system according to the embodiment of the present invention, the step S32' includes the steps of:
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; further, step S33' includes:
s331': determining a target current according to the corresponding relation between the target pressure and a preset pressure current;
s332': and determining the actual input current of the pressure control valve according to the target current, the first compensation current and the second compensation current.
According to another embodiment of the present invention, a method for controlling a pressure of a hydraulic cylinder system is disclosed, wherein the pressure control valve includes a solenoid valve and/or a power amplifying spool valve.
The invention has the beneficial effects that:
the invention provides a pressure control method of a hydraulic cylinder system, which comprises the steps of firstly calculating the displacement of a hydraulic cylinder based on a displacement sensor or an algorithm, and calculating the oil flow of the hydraulic cylinder according to the displacement of the hydraulic cylinder; then, calculating the hydraulic power based on the pressure difference between the oil inlet and the oil outlet of the pressure control valve and the calculated oil flow; next, the input current of the pressure control valve is compensated according to the hydrodynamic force. The reason that the actual pressure of the hydraulic cylinder and the input current of the pressure control valve are nonlinear due to the hydraulic force is considered, the input current of the pressure control valve is compensated according to the hydraulic force, and the control precision of the pressure of the hydraulic cylinder can be improved.
Drawings
FIG. 1 is a schematic diagram of control accuracy of a prior art hydraulic cylinder with a stationary piston;
FIG. 2 is a schematic diagram of control accuracy of a prior art hydraulic cylinder during piston actuation;
FIG. 3 is a schematic flow chart illustrating a method for controlling pressure in a hydraulic cylinder system according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a hydraulic cylinder system when the hydraulic cylinder provided by the embodiment of the invention is a solenoid valve direct-drive single-action hydraulic cylinder;
FIG. 5 is a schematic structural diagram of a hydraulic cylinder system in which the hydraulic cylinder provided by the embodiment of the present invention is a single-acting hydraulic cylinder driven by a solenoid valve and a power amplifying slide valve;
FIG. 6 is a schematic structural diagram of a hydraulic cylinder system when the hydraulic cylinder provided by the embodiment of the invention is a solenoid valve direct-drive double-acting hydraulic cylinder;
FIG. 7 is a schematic diagram of a double-acting hydraulic cylinder driven by a solenoid valve and a power amplifying slide valve according to an embodiment of the present invention;
FIG. 8 is a closed-loop control diagram of the pressure of a hydraulic cylinder system based on hydraulic power provided by an embodiment of the present invention.
Description of reference numerals:
1. a hydraulic cylinder; 11. a cylinder body; 12. a piston; 13. a hydraulic rod; 2. a pressure control valve; 21. an electromagnetic valve; 22. a power amplifying slide valve; 3. an oil supply circuit; 31. a control valve oil supply circuit; 32. a hydraulic cylinder oil supply loop; 4. a control loop; a. an oil inlet; b. an oil outlet; 5. a pressure sensor; 6. and a displacement sensor.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure. While the invention will be described in conjunction with the preferred embodiments, it is not intended that the features of the invention be limited to that embodiment. On the contrary, the invention has been described in connection with the embodiments for the purpose of covering alternatives or modifications as may be extended based on the claims of the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been omitted from the description in order not to obscure or obscure the focus of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
It should be noted that in this specification, like reference numerals and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present embodiment, it should be noted that the terms "upper", "lower", "inner", "bottom", and the like indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings or orientations or positional relationships that the product of the present invention is usually placed in when used, and are only used for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and operate, and therefore, should not be construed as limiting the present invention.
The terms "first," "second," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
In the description of the present embodiment, it should be further noted that, unless explicitly stated or limited otherwise, the terms "disposed," "connected" and "connected" should be interpreted broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. Specific meanings of the above terms in the present embodiment can be understood as specific cases by those of ordinary skill in the art.
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In order to solve the problem of poor pressure control precision of a hydraulic cylinder in the prior art, the embodiment of the invention provides a pressure control method of a hydraulic cylinder system.
The pressure control method of the hydraulic cylinder system provided by the embodiment is used for controlling the pressure of the hydraulic cylinder.
Specifically, referring to fig. 3, the pressure control method of the hydraulic cylinder system according to the present embodiment includes the steps of:
s1: acquiring flow parameters of the hydraulic cylinder, and calculating the oil flow of oil flowing through the hydraulic cylinder according to the flow parameters;
s2: acquiring pressure parameters of a pressure control valve and oil parameters of oil flowing through the hydraulic cylinder, and calculating hydraulic power of the oil flowing through the hydraulic cylinder according to the oil flow, the pressure parameters and the oil parameters;
s3: and compensating the input current of the pressure control valve according to the hydraulic power and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to a compensation result.
By adopting the scheme, firstly, the displacement of the hydraulic cylinder is calculated based on a displacement sensor or an algorithm, and the oil flow of the hydraulic cylinder is calculated according to the displacement of the hydraulic cylinder; then, calculating hydraulic power based on the pressure difference between an oil inlet and an oil outlet of the pressure control valve and the calculated oil flow; next, the input current of the pressure control valve is compensated according to the hydrodynamic force. The reason that the actual pressure of the hydraulic cylinder is nonlinear with the input current of the pressure control valve due to the hydraulic force is considered, the input current of the pressure control valve is compensated according to the hydraulic force, and the control precision of the pressure of the hydraulic cylinder can be improved.
Next, a pressure control method of the hydraulic cylinder system provided in the present embodiment will be described in detail with reference to fig. 3 to 8.
First, the hydraulic cylinder system will be described with reference to fig. 4 to 7.
In this embodiment, the hydraulic cylinder system includes a hydraulic cylinder 1, and the hydraulic cylinder 1 includes a cylinder body 11, a piston 12, and a hydraulic rod 13. Wherein a piston 12 is movably arranged in the inner cavity of the cylinder 11, and a hydraulic rod 13 is connected with the piston 12.
The hydraulic cylinder system further comprises a pressure control valve 2, an oil supply circuit 3 and a control circuit 4.
The oil supply circuit 3 includes a control valve oil supply circuit 31 and a cylinder oil supply circuit 32. The control valve oil supply loop 31 is connected to an oil inlet a of the pressure control valve 2, and two ends of the hydraulic cylinder oil supply loop 32 are respectively connected to an oil outlet b of the pressure control valve 2 and the hydraulic cylinder 1. Both ends of the control circuit 4 are connected to the pressure control valve 2 and the cylinder oil supply circuit 32, respectively.
Preferably, in the present embodiment, the pressure control valve 2 includes a solenoid valve 21 and/or a power amplifying spool valve 22.
That is, in the present embodiment, the pressure control valve 2 is mainly used to control the pressure of the oil in the hydraulic cylinder 1. The pressure of the oil in the hydraulic cylinder 1 may be controlled by the solenoid valve 21 alone, or by the solenoid valve 21 and the power amplifying spool 22 together. The number of the solenoid valves 21 and the power amplifying spool valves 22 may be set arbitrarily, which is not limited in this embodiment.
Fig. 4 is a schematic structural diagram of a hydraulic cylinder system provided in an embodiment of the present invention, in which a hydraulic cylinder is specifically a solenoid valve direct-drive single-acting hydraulic cylinder.
In the hydraulic cylinder system formed by the electromagnetic valve direct-drive single-action hydraulic cylinder, the electromagnetic valve 21 receives a control instruction, and then the pressure of the hydraulic cylinder 1 is controlled. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds the actual pressure back to the controller for closed-loop control.
FIG. 5 is a schematic block diagram of another hydraulic cylinder system in which the hydraulic cylinders, specifically solenoid valves and power amplifying slide valves, actuate single-acting hydraulic cylinders, according to an embodiment of the present invention.
In the hydraulic cylinder system composed of the solenoid valve and the power amplifying spool driving single-acting hydraulic cylinder, the solenoid valve 21 and the power amplifying spool 22 have the corresponding oil supply circuit 3 and control circuit 4, respectively. The control valve oil supply circuit 31 of the electromagnetic valve 21 is connected to the oil inlet a of the electromagnetic valve 21. The control valve oil supply circuit 31 of the power amplification slide valve 22 is connected to the oil inlet a of the power amplification slide valve 22, and both ends of the hydraulic cylinder oil supply circuit 32 are respectively connected to the oil outlet b of the power amplification slide valve 22 and the hydraulic cylinder 1. Both 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. Both ends of the control circuit 4 of the power amplifying spool 22 are connected to the power amplifying spool 22 and the cylinder oil supply circuit 32, respectively. The pressure sensor 5 is arranged in the vicinity of the control circuit 4 of the power amplifying spool 22.
The solenoid valve 21 outputs a control command to the power amplification spool 22, and controls the pressure of the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds the actual pressure back to the controller for closed-loop control.
Fig. 6 is a schematic structural diagram of another hydraulic cylinder system provided in an embodiment of the present invention, in which the hydraulic cylinder is specifically a solenoid valve direct-drive double-acting hydraulic cylinder.
In the hydraulic cylinder system consisting of the solenoid valve direct-drive double-acting hydraulic cylinder, two solenoid valves 21 are provided. And, two electromagnetic valves 21 are respectively connected to the left and right sides of the hydraulic cylinder 1 to control the hydraulic cylinder 1 from both sides of the hydraulic cylinder 1. The control valve oil supply circuit 31 is connected to an oil inlet a of the electromagnetic valve 21, and both ends of the hydraulic cylinder oil supply circuit 32 are connected to an oil outlet b of the electromagnetic valve 21 and the hydraulic cylinder 1, respectively. Both ends of the control circuit 4 are connected to the solenoid valve 21 and the cylinder oil supply circuit 32, respectively. The pressure sensor 5 is provided near the cylinder oil supply circuit 32. The displacement sensor 6 is disposed near the hydraulic cylinder 1.
The solenoid valve 21 receives a control command and performs pressure control on the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds the actual pressure back to the controller for closed-loop control. The displacement sensor 6 collects the displacement of the hydraulic cylinder 1 and feeds the displacement back to the controller.
Fig. 7 is a schematic structural diagram of a hydraulic cylinder system in which hydraulic cylinders, specifically, solenoid valves and power amplifying slide valves, drive double-acting hydraulic cylinders according to an embodiment of the present invention.
In a hydraulic cylinder system including the solenoid valve and the power amplification spool valve for driving the double-acting hydraulic cylinder, a solenoid valve 21, a power amplification spool valve 22, and a pressure sensor 5 are provided on both sides of the hydraulic cylinder 1, respectively. The displacement sensor 6 is disposed near the hydraulic cylinder 1. The connection relation of the single-action hydraulic cylinder driven by the electromagnetic valve and the power amplification slide valve is not essentially different, and the description of the embodiment is omitted.
The solenoid valve 21 outputs a control command to the power amplifying spool 22, and pressure-controls the hydraulic cylinder 1. The pressure sensor 5 collects the actual pressure of the hydraulic cylinder 1 and feeds the actual pressure back to the controller for closed-loop control. The displacement sensor 6 collects the displacement of the hydraulic cylinder 1 and feeds the displacement back to the controller.
Next, a method of controlling the pressure of the hydraulic cylinder system according to the present embodiment will be described.
Firstly, step S1 is executed, the flow parameter of the hydraulic cylinder is obtained, and the oil flow of the oil flowing through the hydraulic cylinder is calculated according to the flow parameter.
Considering the incompressibility of the oil, the flow rate through the hydraulic cylinder via the solenoid valve or the power amplifying slide valve is approximately equal to the product of the moving speed of the piston and the cross-sectional area of the inner cavity of the cylinder body.
The embodiment provides two oil flow calculation methods.
Firstly, the oil flow is calculated by a displacement sensor method.
The flow parameters include the cross-sectional area of the inner cavity of the cylinder body and the actual displacement of the piston.
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.
The actual displacement of the piston is the displacement of the piston in the cylinder of the hydraulic cylinder compared to the original position. Which can be measured directly by a displacement sensor.
Specifically, the oil flow is calculated according to the following formula:
wherein Q is the oil flow, x is the actual displacement of the piston, and A is the cross-sectional area of the inner cavity of the cylinder.
The above formula can also be understood as being obtained by the formula Q = V × a. V is the moving speed of the piston in the hydraulic cylinder.
Secondly, the oil flow is obtained by an estimation method.
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.
Specifically, step S1 further includes the steps of:
s11: acquiring a pressure displacement characteristic curve of the hydraulic cylinder, and determining the calculated displacement of the piston according to the pressure displacement characteristic curve of the hydraulic cylinder and the actual pressure of the hydraulic cylinder;
s12: and calculating the oil flow according to the cross-sectional area of the inner cavity of the cylinder body and the calculated displacement of the piston.
The pressure-displacement characteristic curve of the hydraulic cylinder is obtained by acquiring data of displacements of a plurality of sets of hydraulic cylinders under a certain pressure, and performing processes such as point drawing and fitting on the data. Specifically, the displacement of the hydraulic cylinder can be obtained by looking up a table of data of the pressure sensor or according to a pressure displacement characteristic curve.
The calculated displacement of the piston is the displacement of the piston corresponding to a certain pressure obtained from the pressure-displacement characteristic curve.
In step S12, the oil flow rate is calculated according to the following equation:
wherein Q is oil flow, x * For calculating the displacement of the piston, x * And = f (p), and A is the cross-sectional area of the inner cavity of the cylinder body.
It should be noted that in the present embodiment, for a single-acting hydraulic cylinder, such as the solenoid valve direct-drive single-acting hydraulic cylinder and the solenoid valve and the power amplification slide valve drive single-acting hydraulic cylinder described in the above embodiments, the calculated displacement amount of the piston can only take into account the pressure displacement characteristics of the hydraulic cylinder. For the double-acting hydraulic cylinder, due to the complex system, not only the pressure displacement characteristic of the hydraulic cylinder but also other characteristics such as oil density and pressure need to be considered. And the displacement of the hydraulic cylinder is obtained through the joint calculation of the pressure displacement characteristic and other characteristics.
And next, executing the step S2, acquiring pressure parameters of the pressure control valve and oil parameters of the oil flowing through the hydraulic cylinder, and calculating hydraulic power of the oil flowing through the hydraulic cylinder according to the oil flow, the pressure parameters and the oil parameters.
Specifically, the pressure parameters comprise a jet flow angle of the pressure control valve and a pressure difference between an oil inlet and an oil outlet of the pressure control valve.
And the oil parameter includes an oil density corresponding to a current oil temperature of the oil flowing through the hydraulic cylinder.
It should be explained that the jet angle of the pressure control valve is related to the structural parameters of the valve port of the pressure control valve and the opening amount of the valve port. It can be obtained by a numerical simulation method, and this embodiment is not described again.
The pressure difference between the oil inlet and the oil outlet of the pressure control valve is the difference between the pressure of the oil flowing through the oil inlet of the pressure control valve and the pressure of the oil flowing through the oil outlet of the pressure control valve. The pressure at the outlet of the pressure control valve is the value of a pressure sensor arranged in the vicinity of the control circuit. The pressure of an oil inlet of the pressure control valve can be acquired through a pressure sensor, and can also be directly replaced by the target pressure of a hydraulic cylinder.
The oil density corresponding to the current oil temperature refers to the oil density corresponding to the current temperature of the oil. The temperature data of the oil can be acquired by collecting the temperature data of the oil and looking up a table.
More specifically, in the present embodiment, the hydrodynamic force is calculated according to the following formula:
wherein, F jet The hydraulic power is adopted, Q is the oil flow, theta is the jet flow angle of the pressure control valve, delta p is the pressure difference between an oil inlet and an oil outlet of the pressure control valve, and rho is the oil density.
And then, executing a step S3, compensating the input current of the pressure control valve according to the hydraulic power and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to a compensation result.
In the present embodiment, the compensation of the input current of the pressure control valve according to the hydraulic power is considered based on the balance principle of the pressure control valve, particularly the solenoid valve.
The dynamic balance equation of the solenoid valve is as follows:
F se -D×v s -k s ×(x s +x 0 )-p×A s ±F jet ＝m s ×α s
wherein, F se The electromagnetic force of the electromagnetic valve is the electromagnetic force corresponding to the open-loop target current calculated based on a steady-state target pressure-ammeter, D is the viscous damping coefficient of the valve core of the electromagnetic valve, v s Is the moving speed of the valve core of the solenoid valve, k s Is the spring rate, x, of the solenoid valve s Is the displacement of the valve core of the solenoid valve, x 0 Is the pre-compression amount of the spring in the solenoid valve, p is the control pressure (feedback pressure) of the solenoid valve, A s Is the area of a feedback cavity of a valve core of the electromagnetic valve, +/-F jet Is hydrodynamic, the direction of which always causes the valve core to tend to close, the pressure to rise to minus, the pressure to fall to plus, m s Is the mass of the valve core of the solenoid valve, alpha s Is the acceleration of the movement of the solenoid valve spool.
Based on the dynamic balance equation of the solenoid valve, it can be seen that the balance equation is mainly electromagnetic force F se With feedback pressure p x A s Balancing of (1). And no hydrodynamic force F jet Compared with the situation that the hydraulic cylinder is not in motion, the hydraulic force causes the electromagnetic force F of the control pressure p and the input current on the premise that the dynamic damping force (friction is small), the inertia force (mass is small) and the spring force (proportion is small) of the valve core of the electromagnetic valve are negligible se The cause of the non-linearity. Therefore, compensating for hydraulic force can improve hydraulic response performance.
Specifically, in this embodiment, the step S3 includes the following steps:
s31: determining a compensation electromagnetic force according to the hydrodynamic force and a preset compensation coefficient;
s32: a first compensation current is determined based on the compensation electromagnetic force and an input current of the pressure control valve is compensated based on the first compensation current.
More specifically, the compensating electromagnetic force is determined according to the following formula:
F′ se ＝±K jet F jet
wherein, F' se To compensate for electromagnetic forces, K jet To compensate for the coefficient, ± F jet The hydraulic power is adopted, when the hydraulic power enables the pressure of the pressure control valve to rise, the sign of the hydraulic power is negative, when the hydraulic power enables the pressure of the pressure control valve to fall, the sign of the hydraulic power is positive.
Compensation factor K jet Mainly related to the characteristics of the solenoid valve. In the present embodiment, the hydraulic force f jet In combination with a compensation factor K jet The effect of actual compensation is adjusted, and the electromagnetic force F caused by the current of the electromagnetic valve can be avoided se Upper direct liquid power increasing F jet The compensation influences other subentries in the original dynamic balance equation.
To be construed, F' se Is the electromagnetic force corresponding to the first compensation current.
It should be noted that, in this embodiment, step S3 further includes the following steps:
s32': acquiring target pressure and actual pressure of a hydraulic cylinder, and compensating input current of a pressure control valve according to the target pressure and the actual pressure;
s33': the pressure of the hydraulic cylinder is controlled according to the compensation results in step S32 and step S32'.
It should be explained that the target pressure of the hydraulic cylinder is a control target of the hydraulic cylinder drive derived from the control upstream.
The actual pressure of the hydraulic cylinder is the real-time pressure of the hydraulic cylinder measured by the pressure sensor.
More specifically, step S32' includes the steps of:
s321': determining a compensation pressure according to the target pressure and the actual pressure of the hydraulic cylinder;
s322': a second compensation current is determined based on the compensation pressure and the input current to the pressure control valve is compensated based on the second compensation current.
Step S33' includes:
s331': determining a target current according to the corresponding relation between the target pressure and a preset pressure current;
s332': and determining the actual input current of the pressure control valve according to the target current, the first compensation current and the second compensation current.
It should be explained that the compensation pressure is also the difference between the target pressure and the actual pressure of the hydraulic cylinder. In some embodiments, certain adjustment factors may also be incorporated based on the difference between the target pressure and the actual pressure.
The preset pressure current corresponding relation refers to the current of the electromagnetic valve of a certain hydraulic cylinder which is correspondingly driven under specific pressure. Which is related to the characteristics of the hydraulic cylinder and the solenoid valve.
It should also be explained that the input current of the pressure control valve is the control signal of the pressure control valve. The input of the pressure control valve is a current signal, and the output of the pressure control valve is a pressure signal. When the input current changes, the output pressure can change.
The above control method provided in step S3 is explained with reference to fig. 8.
In this embodiment, the pressure of the hydraulic cylinder is controlled in a closed loop manner, in which the target pressure of the hydraulic cylinder is used as a given quantity, the actual pressure of the hydraulic cylinder is used as a controlled quantity, the electromagnetic valve and the hydraulic cylinder are used as control objects, and the actual pressure of the hydraulic cylinder is controlled by performing deviation control on the input current of the electromagnetic valve.
When the control is performed, a target pressure that can cause the pressure response of the hydraulic cylinder to approach the pressure-current response characteristic of the solenoid valve itself is first determined. And then, looking up a table according to the target pressure to obtain the target current for controlling the electromagnetic valve, namely the input current of the electromagnetic valve.
Then, the hydraulic force of the oil flowing through the hydraulic cylinder is calculated according to the displacement of the hydraulic cylinder, a first compensation current is generated according to the calculated hydraulic force, and the first compensation current is added or subtracted on the basis of the input current of the electromagnetic valve, that is, the compensation current 1 in fig. 8. At the same time, it is also necessary to calculate the direct difference between the actual pressure of the hydraulic cylinder and the target pressure, and to generate a second compensation current based on this difference, and to add this second compensation current on the basis of the input current of the solenoid valve, i.e. the compensation current 2 in fig. 8. And comprehensively determining current according to the input current of the electromagnetic valve, the first compensation current and the second compensation current, namely the final input current of the electromagnetic valve.
The pressure of the hydraulic cylinder can be controlled by controlling the solenoid valve by the final input current.
While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a more detailed description of the invention, taken in conjunction with the specific embodiments thereof, and that no limitation of the invention is intended thereby. Various changes in form and detail, including simple deductions or substitutions, may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (10)
1. The pressure control method of the hydraulic cylinder system is characterized in that the hydraulic cylinder system comprises a hydraulic cylinder, the hydraulic cylinder comprises 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 with the piston; and is
The hydraulic cylinder system also comprises a pressure control valve, a control loop and an oil supply loop, wherein the oil supply loop comprises a control valve oil supply loop and a hydraulic cylinder oil supply loop; the control valve oil supply loop is connected to an oil inlet of the pressure control valve, and two ends of the hydraulic cylinder oil supply loop are respectively connected with an oil outlet of the pressure control valve and the hydraulic cylinder; two ends of the control loop are respectively connected with the pressure control valve and the hydraulic cylinder oil supply loop; the pressure control method of the hydraulic cylinder system is used for controlling the pressure of the hydraulic cylinder; and is
The pressure control method of the hydraulic cylinder system comprises the following steps:
s1: acquiring flow parameters of the hydraulic cylinder, and calculating the oil flow of oil flowing through the hydraulic cylinder according to the flow parameters;
s2: acquiring pressure parameters of the pressure control valve and oil parameters of oil flowing through the hydraulic cylinder, and calculating hydraulic power of the oil flowing through the hydraulic cylinder according to the oil flow, the pressure parameters and the oil parameters;
s3: and compensating the input current of the pressure control valve according to the hydraulic power and a preset compensation coefficient, and controlling the pressure of the hydraulic cylinder according to a compensation result.
2. The pressure control method of a hydraulic cylinder system according to claim 1, wherein in step S1, the flow rate parameter includes a cross-sectional area of an inner cavity of the cylinder block, an actual displacement amount of the piston; and is
Calculating the oil flow according to the following formula:
wherein Q is the oil flow, 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 a hydraulic cylinder system according to claim 1, wherein in the step S1, the flow rate parameter includes a cross-sectional area of an inner cavity of the cylinder block, a calculated displacement amount of the piston, and an actual pressure of the hydraulic cylinder; and is
The step S1 further includes the steps of:
s11: acquiring a pressure displacement characteristic curve of the hydraulic cylinder, and determining the calculated displacement of the piston according to the pressure displacement characteristic curve of the hydraulic cylinder and the actual pressure of the hydraulic cylinder;
s12: and calculating the oil flow 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 a hydraulic cylinder system according to claim 3, characterized in that, in step S12, the oil flow rate is calculated according to the following equation:
wherein Q is the oil flow, x * Calculating the displacement of the piston, and A is the cross-sectional area of the inner cavity of the cylinder.
5. The pressure control method of a hydraulic cylinder system according to claim 1, wherein in the step S2, the pressure parameters include a jet angle of the pressure control valve, and a pressure difference between an oil inlet and an oil outlet of the pressure control valve;
the oil parameter comprises oil density corresponding to the current oil temperature of oil flowing through the hydraulic cylinder; and is provided with
Calculating the hydrodynamic force according to the following formula:
wherein, F jet And for the hydraulic power, Q is the oil flow, theta is the jet flow angle of the pressure control valve, delta p is the pressure difference between an oil inlet and an oil outlet of the pressure control valve, and rho is the oil density.
6. The pressure control method of the hydraulic cylinder system according to claim 1, wherein the step S3 includes the steps of:
s31: determining a compensation electromagnetic force according to the hydrodynamic force and the preset compensation coefficient;
s32: a first compensation current is determined based on the compensated electromagnetic force, and an input current of the pressure control valve is compensated based on the first compensation current.
7. Method for pressure control of a hydraulic cylinder system according to claim 6, characterized in that the compensating electromagnetic force is determined according to the following formula:
F′ se ＝±K jet F jet
wherein, F' se For said compensation of electromagnetic forces, K jet Is the compensation coefficient, ± F jet And the sign of the hydrodynamic force is-when the hydrodynamic force increases the pressure of the pressure control valve, and the sign of the hydrodynamic force is +.
8. The pressure control method of the hydraulic cylinder system according to claim 7, wherein the step S3 further comprises the steps of:
s32': acquiring target pressure and 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;
and S33': and controlling the pressure of the hydraulic cylinder according to the compensation results in the step S32 and the step S32'.
9. The pressure control method of the hydraulic cylinder system according to claim 8, wherein the step S32' includes the steps of:
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 is provided with
The step S33' includes:
s331': determining a target current according to the corresponding relation between the target pressure and a preset pressure current;
s332': and determining the actual input current of the pressure control valve according to the target current, the first compensation current and the second compensation current.
10. Method for pressure control of a hydraulic cylinder system according to any one of claims 1-9, characterized in that the pressure control valve comprises a solenoid valve and/or a power amplifying slide valve.
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Effective date of registration: 20221228 Address after: Room 509, building 1, 563 Songtao Road, Pudong New Area, Shanghai, 201203 Applicant after: SAIC Motor Corp.,Ltd. Applicant after: Shanghai automotive industry (Group) Co.,Ltd. Address before: Room 509, building 1, 563 Songtao Road, Pudong New Area, Shanghai, 201203 Applicant before: SAIC Motor Corp.,Ltd. |