Single pump servo hydraulic motion system and control method thereof

Abstract

The present application relates to a hydraulic electromechanical system, comprising: a hydraulic servo pump group, a check valve, a first to third directional valve, a hydraulic actuator and an accumulator. The oil inlet of the first directional valve is connected to the hydraulic servo pump group, and the oil return is connected to the oil tank; the input of the check valve is connected to the second main oil port of the first directional valve; the oil inlet of the second directional valve is connected to the output of the check valve, and the oil return is connected to the oil tank; one oil port of the hydraulic actuator is connected to the first main oil port of the first directional valve, and the other oil port is connected to the second main oil port of the second directional valve; wherein the accumulator is connected to the hydraulic actuator through the second and third directional valves. The control method of the system comprises: subtracting the position feedback from the target given position quantity, then sequentially passing through the servo pump control module and the hydraulic actuator control module, and then outputting the position control result, wherein the position feedback is from the output of the hydraulic actuator control module. The present application can realize precise position follow-up control, and is low in cost, energy-saving, durable and reliable.

Description

Single-pump servo hydraulic motion system and its control method Technical Field

[0001] This invention belongs to the field of industrial electrical automation and provides an implementation scheme for precision position control technology in hydraulic transmission technology, especially relating to a single-pump servo hydraulic motion system and its control method. Background Technology

[0002] Hydraulic transmission is a widely used technology in industry. It is powerful, reliable, and smooth, and is especially suitable for linear motion equipment and heavy equipment, such as presses, forging machines, extruders, and mold opening and closing devices.

[0003] Many linear motion devices require not only force and speed adjustments but also precise positioning. In hydraulic transmission systems, position control is typically achieved through flow valves or direct pump control. These methods reduce speed as the device approaches the target position and cut off the hydraulic circuit upon reaching the target position, achieving relatively precise position control. However, this method is only suitable for fixed-point control in a single direction with a predetermined target position. It is unsuitable for position servo control where the target position changes dynamically and can be arbitrarily changed in either direction.

[0004] Traditional valve control technology can also achieve position tracking control of hydraulic cylinders, but it requires the use of servo flow valves and dynamic adjustment of the pressure on both sides of the hydraulic cylinder piston. This pressure difference acts on the piston and connecting rod, changing and adjusting their direction of motion and acceleration, thereby achieving piston rod position control. However, this control is essentially implemented by pressure relief valves on both sides of the hydraulic cylinder, resulting in significant energy loss. Furthermore, servo flow valves are very expensive, prone to wear, and have requirements for hydraulic oil quality and temperature. This technology is also primarily suitable only for cylinders with a constant cross-sectional area. Summary of the Invention

[0005] Based on advanced servo pump control technology, this invention provides an electromechanical-hydraulic hybrid system and its control scheme, which can also achieve precise position follow-up control and has the advantages of low cost, energy saving, durability and reliability. It also solves at least one of the technical problems existing in the prior art.

[0006] The technical solution of this invention relates to a hydraulic electromechanical system, comprising: a hydraulic servo pump assembly, the hydraulic servo pump assembly having a servo motor to drive an oil pump to deliver oil from an oil tank; a first directional valve, the first directional valve having a first main oil port, a second main oil port, an inlet port, and a return port, the inlet port of the first directional valve being connected to the hydraulic servo pump assembly, and the return port of the first directional valve being connected to the oil tank; a check valve, the check valve having an input port and an output port, the check valve restricting the transfer of oil from the input port to the output port, the input port of the check valve being connected to the second main oil port of the first directional valve; and a second directional valve, the second directional valve having a first main oil port, a second main oil port, an inlet port, and a return port, the inlet port of the second directional valve being connected to the output port of the check valve. The return port of the second directional valve is connected to the oil tank; a hydraulic actuator has a cylinder, a first oil port, a second oil port, and a piston located in the cylinder between the first oil port and the second oil port, wherein the first oil port of the hydraulic actuator is connected to the first main oil port of the first directional valve, and the second oil port of the hydraulic actuator is connected to the second main oil port of the second directional valve; a third directional valve has a first port and a second port, which are cut off when the third directional valve is closed and remain connected when the third directional valve is open, wherein the first port of the third directional valve is connected to the output port of the check valve; and an accumulator is connected to the second port of the third directional valve.

[0007] Furthermore, the first directional control valve includes a first one-way position, a first stop position, and a first two-way position. In the first one-way position, the first main oil port is connected to the oil inlet and the second main oil port is connected to the oil return port. In the first stop position, the first main oil port is cut off from the oil inlet and both the first and second main oil ports are connected to the oil return port. In the first two-way position, the first main oil port is connected to the oil return port and the second main oil port is connected to the oil inlet. The second directional control valve includes a second one-way position, a second stop position, and a second two-way position. In the second one-way position, the first main oil port is connected to the oil inlet and the second main oil port is connected to the oil return port. In the second stop position, the first main oil port is cut off from the oil inlet and the second main oil port is cut off from the oil return port. In the second two-way position, the first main oil port is connected to the oil return port and the second main oil port is connected to the oil inlet.

[0008] Furthermore, the hydraulic electromechanical system includes a pressure relief valve, the input end of which is connected to the accumulator, and the output end of which is connected to the oil tank.

[0009] Furthermore, the hydraulic actuator includes: a piston rod connected to the piston; and a displacement sensor connected to the piston rod for acquiring position information of the piston rod.

[0010] Furthermore, the motor of the hydraulic servo pump unit drives a single oil pump to operate in a unidirectional rotation manner.

[0011] The technical solution of the present invention also relates to a hydraulic servo control method for controlling the above-mentioned hydraulic electromechanical system, the method comprising the following steps:

[0012] S10. Switch the first directional valve to connect the first oil port of the hydraulic actuator to the hydraulic servo pump group, switch the second directional valve and open the third directional valve to connect the second oil port of the hydraulic actuator to the accumulator, and collect the motion position feedback of the hydraulic actuator in real time through the displacement sensor.

[0013] S20. Subtract the motion position feedback of the hydraulic actuator from the given position input of the hydraulic actuator of the hydraulic electromechanical system to obtain the input error. After the input error is transmitted to the PID servo control loop of the hydraulic servo pump group, it is multiplied by the first proportional link coefficient (K1) to calculate the output flow of the hydraulic servo pump group as the first oil port flow of the hydraulic actuator.

[0014] S30. The difference between the calculated flow rate at the first port of the hydraulic actuator and the flow rate at the second port of the hydraulic actuator is transmitted to the hydraulic actuator control module. After the fluid volume is obtained through the integration process, it is multiplied by the elastic coefficient (K2) to calculate the hydraulic pressure. Then, the hydraulic pressure is reduced by at least the piston pressure caused by the accumulator, or further reduced by the internal resistance of the hydraulic actuator, to obtain the pressure difference.

[0015] S40. The pressure difference is multiplied by the second proportional element coefficient (K3) and then passed through an integral element to calculate the movement speed of the hydraulic actuator.

[0016] S50. The calculated motion speed of the hydraulic actuator is passed through an integrator to calculate the motion position output of the hydraulic actuator.

[0017] Furthermore, in the method described: the flow rate of the second oil port of the hydraulic actuator is calculated by multiplying the movement speed of the hydraulic actuator by the cross-sectional area coefficient (K5) of the cylinder of the hydraulic actuator; the resistance inside the hydraulic actuator includes the viscous force generated by the cylinder and the piston, which is calculated by multiplying the movement speed of the hydraulic actuator by the viscosity coefficient (K4) of the cylinder; the piston pressure caused by the accumulator is calculated by multiplying the hydraulic pressure of the accumulator by the cross-sectional area of ​​the piston inside the cylinder.

[0018] The technical solution of the present invention also relates to another hydraulic servo control method for controlling the above-mentioned hydraulic electromechanical system, the method comprising the following steps:

[0019] S1. Switch the first directional valve to connect the first oil port of the hydraulic actuator to the hydraulic servo pump group, switch the second directional valve and open the third directional valve to connect the second oil port of the hydraulic actuator to the accumulator, and collect the motion position feedback of the hydraulic actuator in real time through the displacement sensor.

[0020] S2. Subtract the motion position feedback of the hydraulic actuator from the given position input of the hydraulic actuator in the hydraulic electromechanical system to obtain the input error. Then, transmit the input error to the PID servo control loop of the hydraulic servo pump group to calculate the speed of the servo motor.

[0021] S3. The rotational speed of the servo motor is passed through the hydraulic actuation control module to calculate the motion speed of the hydraulic actuator. The transfer function of the hydraulic actuation control module is G(s)=(K1 / K5) / (1+T2·s(1+T1·s)), where T1=1 / (K3·K4), T2=K4 / (K2·K5), K1 is the first proportional element coefficient, K2 is the elastic coefficient of the hydraulic actuator cylinder, K3 is the second proportional element coefficient, K4 is the viscosity coefficient of the hydraulic actuator cylinder, and K5 is the cross-sectional area coefficient of the hydraulic actuator cylinder.

[0022] S4. The calculated motion speed of the hydraulic actuator is passed through an integrator to calculate the motion position output of the hydraulic actuator.

[0023] Furthermore, any of the above methods may include the following steps: closing the third directional valve, switching the first directional valve to the first one-way position to connect the first port of the hydraulic actuator to the hydraulic servo pump assembly, switching the second directional valve to the second two-way position to connect the second port of the hydraulic actuator to the oil tank, triggering the servo motor of the hydraulic servo pump assembly to rotate to output flow, thereby causing the hydraulic actuator to output movement from the first port to the second port; or closing the third directional valve, switching the first directional valve to the first two-way position to connect the first port of the hydraulic actuator to the oil tank. The oil tank is switched, and the second directional valve is switched to the second one-way position so that the second oil port of the hydraulic actuator is connected to the hydraulic servo pump group, triggering the servo motor of the hydraulic servo pump group to rotate to output flow, thereby causing the hydraulic actuator to output movement from the second oil port to the first oil port; or the third directional valve is opened, the first directional valve is switched to the first two-way position so that the output port of the hydraulic servo pump group is connected to the accumulator through the check valve, and the second directional valve is switched to the second cut-off position, and the servo motor of the hydraulic servo pump group is triggered to rotate to output flow, thereby causing the accumulator to store energy.

[0024] The present invention also relates to a computer device, including a memory and a processor, wherein the processor performs the above-described method when executing a computer program stored in the memory.

[0025] The technical solution of the present invention may also relate to a computer-readable storage medium storing computer program instructions thereon, which, when executed by a processor, implement the above-described method.

[0026] Compared with existing technologies, especially traditional servo valves, the technical advantages of this invention are as follows:

[0027] 1. By using a servo hydraulic pump unit with an accumulator and one or two additional directional valves, the functions that can be achieved by a regular motor pump unit with expensive servo valves are replaced, resulting in a significant reduction in overall cost.

[0028] 2. The servo hydraulic motion system in the technical solution of this invention is itself a CNC device, which eliminates the need for additional motion control devices, further reducing costs and making it easier to achieve full digitization of the equipment;

[0029] 3. Compared with servo valves with overflow control, servo hydraulic pump sets eliminate overflow losses, significantly saving energy, reducing oil temperature, and improving equipment reliability and lifespan. Attached Figure Description

[0030] Figure 1 is a schematic diagram of the servo hydraulic motion system according to the present invention.

[0031] Figure 2 is a diagram of the working state of the servo hydraulic motion system according to the present invention, which realizes unidirectional rightward movement.

[0032] Figure 3 is a diagram of the working state of the servo hydraulic motion system according to the present invention, which realizes unidirectional leftward movement.

[0033] Figure 4 is a diagram of the working state of the servo hydraulic motion system according to the present invention, which realizes hydraulic energy storage.

[0034] Figure 5 is a diagram of the working state of the servo hydraulic motion system according to the present invention, which realizes bidirectional motion under closed-loop servo control.

[0035] Figure 6 is a general control block diagram of the servo hydraulic motion control method according to the present invention.

[0036] Figure 7 is a control block diagram of the hydraulic actuation module in the servo hydraulic motion control method according to the present invention.

[0037] Figure 8 is a schematic diagram of hydraulic cylinder pressure calculation in an embodiment of the method according to the present invention.

[0038] Figure 9 is a simplified control block diagram of the servo hydraulic motion control method according to the present invention.

[0039] Figure 10 is a simplified control block diagram including the interpretation of the transfer function in an embodiment of the method according to the present invention. Detailed Implementation

[0040] Hydraulic transmission uses an electric motor to drive an oil pump 21, converting electrical energy into mechanical energy, which then drives a hydraulic cylinder through pipelines, thereby providing power to the mechanical device. Since hydraulic transmission can only provide thrust, not pull, the hydraulic circuit has multiple pipelines that are switched via directional valves, thus changing the direction of movement of the hydraulic cylinder. Simultaneously, pressure valves and flow valves in the pipelines can also control the thrust and linear velocity of the hydraulic cylinder, ultimately achieving the target position, by altering the actual flow rate supplied by the oil pump 21 to the hydraulic cylinder.

[0041] Under the requirements of position servo control, not only must the final stopping position of the machine be consistent with the commanded position, but the instantaneous actual position of each motion process must also be consistent with the target position (within the allowable error range), that is, the actual position dynamically follows the target position. This control requirement not only places high demands on the responsiveness of the hydraulic cylinder speed control, but also requires the hydraulic cylinder to be able to perform precise and smooth bidirectional movements at any time.

[0042] As mentioned earlier, hydraulic transmission can only provide thrust, not pull. Traditionally, bidirectional movement of hydraulic cylinders is achieved by switching pipelines using directional valves. However, directional valves have long switching times and sudden changes in power during the switching process, making precise closed-loop position control impossible. Current hydraulic cylinder position tracking uses servo valves. The basic principle is to simultaneously supply oil to both sides of the hydraulic cylinder piston, dynamically adjusting the flow ratio based on control signals to change the pressure on both sides of the piston. The pressure difference on both sides of the piston is the actual thrust of the hydraulic cylinder. This force can be controlled bidirectionally and linearly, thus providing the basis for position tracking control. Furthermore, since servo valves are very expensive and energy-intensive, this invention adopts an alternative technical solution, based on fixed-displacement pump servo control, to provide a device or system for achieving bidirectional dynamic motion control of the hydraulic cylinder.

[0043] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0044] It should be noted that, unless otherwise specified, when a feature is referred to as "fixed" or "connected" to another feature, it can be directly fixed or connected to the other feature, or indirectly fixed or connected to the other feature. Furthermore, the descriptions of "upper," "lower," "left," "right," "top," and "bottom" used in this invention are only relative to the relative positional relationships of the various components of the invention in the accompanying drawings.

[0045] Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and not for limiting the invention. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0046] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various elements, these elements should not be limited to these terms. These terms are only used to distinguish elements of the same type from one another. For example, without departing from the scope of this disclosure, a first element may also be referred to as a second element, and similarly, a second element may also be referred to as a first element.

[0047] Referring now to Figures 1 to 5, in some embodiments, the servo hydraulic electromechanical system according to the present invention includes at least: a hydraulic servo pump assembly 20, a first directional valve 30, a check valve 40, a second directional valve 50, a hydraulic actuator 60, a third directional valve 90, and an accumulator 70.

[0048] The hydraulic servo pump unit 20 serves as the power source of the system. It includes a servo motor, an oil pump 21, and accessories. The servo motor, driven by a servo driver, drives the oil pump 21 to deliver oil from the oil tank 10, thereby providing high-performance flow control response and hydraulic pressure closed-loop control functions. Preferably, the hydraulic servo pump unit 20 only requires a single motor to drive the single oil pump 21 in a unidirectional rotation manner.

[0049] Both the first directional valve 30 and the second directional valve 50 can be three-position four-way electro-hydraulic directional valves, and each has a first main oil port A, a second main oil port B, an inlet oil port P, and a return oil port T. Referring specifically to Figure 1, the first directional valve 30 includes a first left-hand position 31 (corresponding to the first one-way position mentioned above), a first stop position 32, and a first right-hand position 33 (corresponding to the first two-way position mentioned above). In the first directional valve 30, in the first left-hand position 31, the first main oil port A is connected to the inlet oil port P and the second main oil port B is connected to the return oil port T (as shown in Figure 2). In the first stop position 32, the first main oil port A is cut off from the inlet oil port P, and both the first main oil port A and the second main oil port B are connected to the return oil port T (as shown in Figure 1). In the first right-hand position 33, the first main oil port A is connected to the return oil port T and the second main oil port B is connected to the inlet oil port P (as shown in Figure 3). Referring specifically to Figure 1, the second directional valve 50 includes a second left-hand position 51 (corresponding to the second one-way position mentioned above), a second shut-off position 52, and a second right-hand position 53 (corresponding to the second two-way position mentioned above). In the second directional valve 50, when in the second left-hand position 51, the first main oil port A is connected to the oil inlet P and the second main oil port B is connected to the oil return port T (as shown in Figure 3). When in the second shut-off position 52, the first main oil port A is shut off from the oil inlet P and the second main oil port B is shut off from the oil return port T (as shown in Figure 4). When in the second right-hand position 53, the first main oil port A is connected to the oil return port T and the second main oil port B is connected to the oil inlet P (as shown in Figure 2).

[0050] The third directional valve 90 can be a two-position two-way electro-hydraulic directional valve, and has a first port and a second port. Referring specifically to Figure 1, when the third directional valve 90 is closed (or when the third directional valve 90 is switched to the left position shown in Figure 1), the first port and the second port are cut off; when the third directional valve 90 is open (or when the third directional valve 90 is switched to the right position shown in Figure 4), the first port and the second port remain connected.

[0051] The check valve 40 has an inlet and an outlet, and restricts the transfer of oil from the inlet to the outlet within the check valve 40.

[0052] The hydraulic actuator 60 has a cylinder body, a first oil port (e.g., left oil port 61), a second oil port (e.g., right oil port 62), and a piston located within the cylinder body between the first and second oil ports. Specifically, the actuator of the hydraulic actuator 60 can be a hydraulic cylinder or a hydraulic motor, one providing linear motion and the other providing rotary motion. The following description and accompanying drawings use a hydraulic cylinder as an example to describe the structure, connection method, and control method of the hydraulic actuator 60. The hydraulic motor is similar in principle except for the difference between linear and rotary motion; both have a first and second oil port for inlet and outlet of hydraulic fluid, and a piston driven by the hydraulic fluid for operation. Preferably, the hydraulic actuator 60 includes a piston rod 63 (or slide rod) connected to the piston and a displacement sensor 64 connected to the piston rod 63 for acquiring position information of the piston rod 63.

[0053] The accumulator 70 is used to convert the energy in the hydraulic circuit into compressible energy or potential energy at the appropriate time and store it. When the system needs it, it converts the compressible energy or potential energy into hydraulic or pneumatic energy and releases it. It is one of the core components of the present invention and provides resistance for the closed-loop position control of the hydraulic actuator 60.

[0054] Referring again to Figures 1 to 5, in an embodiment of the present invention, the connection relationships of the various devices in the servo hydraulic motion system are as follows: The inlet P of the first directional valve 30 is connected to the hydraulic servo pump group 20, and the return port T of the first directional valve 30 is connected to the oil tank 10; the input port of the check valve 40 is connected to the second main port B of the first directional valve 30; the inlet P of the second directional valve 50 is connected to the output port of the check valve 40, and the return port T of the second directional valve 50 is connected to the oil tank 10; the left port 61 of the hydraulic actuator 60 is connected to the first main port A of the first directional valve 30, and the right port 62 of the hydraulic actuator 60 is connected to the second main port B of the second directional valve 50; wherein, the first port of the third directional valve 90 is connected to the output port of the check valve 40; and the accumulator 70 is connected to the second port of the third directional valve 90. Preferably, a pressure relief valve 80 is also provided, the input end of which is connected to the accumulator 70, and the output end of which is connected to the oil tank 10.

[0055] Furthermore, the servo hydraulic motion system according to the present invention includes a servo driver and a motion controller. The motion controller, through the servo driver, can be used to perform servo control on the motor of the hydraulic servo pump group 20, and can also be used to control the three directional valves (electro-hydraulic directional valves) and the check valve 40 respectively with electrical signals to switch valve positions. This motion controller can be implemented, for example, as a PLC, PAC, FCS, DSC, CNC numerical control system, or other industrial controllers based on single-chip microcomputers / DSPs. Therefore, the controller can switch valve positions to achieve unidirectional or bidirectional left and right movement of the hydraulic cylinder output of the hydraulic actuator 60, and also to achieve energy storage in the accumulator. In other words, the controller can implement the servo hydraulic motion control method according to the present invention. The control method flow of the hydraulic motion system under these different operating modes is described in detail below.

[0056] 1. Rightward movement of the hydraulic cylinder for unidirectional control

[0057] Referring to Figure 2, the third directional valve 90 is closed, and the first directional valve 30 is switched to the first left position 31 so that the left port 61 of the hydraulic actuator 60 is connected to the hydraulic servo pump group 20. The second directional valve 50 is switched to the second right position 53 so that the right port 62 of the hydraulic actuator 60 is connected to the oil tank 10. Then, the servo motor of the hydraulic servo pump group 20 is triggered to rotate to output flow. At this time, the oil output of the hydraulic servo pump group 20 is connected to the left port 61 of the hydraulic cylinder of the hydraulic actuator 60 through the first directional valve 30, while the right port 62 of the hydraulic cylinder is connected to the oil tank 10 through the second directional valve 50. Therefore, the hydraulic oil enters the cylinder from the left side, pushing the piston and piston rod 63 of the hydraulic cylinder to the right, and the right port 62 discharges oil back to the oil tank 10.

[0058] 2. Leftward movement of the hydraulic cylinder for unidirectional control

[0059] Referring to Figure 3, the third directional valve 90 is closed, and the first directional valve 30 is switched to the first right-hand position 33 so that the left port 61 of the hydraulic actuator 60 is connected to the oil tank 10. The second directional valve 50 is switched to the second left-hand position 51 so that the right port 62 of the hydraulic actuator 60 is connected to the hydraulic servo pump group 20, and then the servo motor of the hydraulic servo pump group 20 is triggered to rotate to output flow. At this time, the oil output from the hydraulic servo pump group 20 passes through the check valve 40 and the second directional valve 50 and then passes through the right port 62 of the hydraulic cylinder of the hydraulic actuator 60, while the left port 61 of the hydraulic cylinder passes through the first directional valve 30 to the oil tank 10. Therefore, hydraulic pressure enters the cylinder from the right side, pushing the hydraulic cylinder piston and piston rod 63 to the left, and the oil from the left port 61 is discharged back to the oil tank 10.

[0060] 3. Energy storage and release accumulators for unidirectional control

[0061] Referring to Figure 4, the third directional valve 90 is opened, and the first directional valve 30 is switched to the first right-hand position 33 so that the output port of the hydraulic servo pump set 20 is connected to the accumulator 70 through the check valve 40. The second directional valve 50 is then switched to the second shut-off position 52, triggering the servo motor of the hydraulic servo pump set 20 to rotate and output flow. At this time, the oil output from the hydraulic servo pump set 20 passes through the first directional valve 30 and then through the check valve 40, while the second directional valve 50 closes the oil circuit, and the third directional valve 90 is opened. Therefore, the pump set can store energy for the accumulator 70.

[0062] To release energy from the accumulator 70, in the energy storage configuration, the second main oil port B of the second directional valve 50 can be connected to the oil tank 10. At this time, the second directional valve 50 can be switched to the second right-hand position 53, allowing hydraulic oil to flow from the accumulator 70 back to the oil tank 10. Additionally, the pressure relief valve 80 can also regulate the pressure of the accumulator.

[0063] 4. Hydraulic cylinder for bidirectional closed-loop position control: left and right movement

[0064] Referring to Figure 5, the first directional valve 30 is switched to connect the left port 61 of the hydraulic actuator 60 to the hydraulic servo pump assembly 20. The second directional valve 50 is switched and the third directional valve 90 is opened to connect the right port 62 of the hydraulic actuator 60 to the accumulator 70. At this time, the oil output from the hydraulic servo pump assembly 20 flows through the first directional valve 30 to the left port 61 of the hydraulic cylinder of the hydraulic actuator 60. The second directional valve 50 connects the right port 62 of the hydraulic cylinder and the check valve 40. At the same time, the third directional valve 90 connects the accumulator 70 to the right port 62 of the hydraulic cylinder. The left side of the hydraulic cylinder piston receives the output pressure of the hydraulic servo pump assembly 20, and the right side receives the output pressure of the accumulator 70. The pressure difference between the two determines whether the piston moves to the left or right. Specifically, when closed-loop position control of the hydraulic cylinder is required, the hydraulic circuit is in the aforementioned closed-loop position control mode. The hydraulic cylinder piston is simultaneously subjected to the combined force of the output of the left hydraulic servo pump group 20 and the output of the right accumulator 70. When the thrust on the left is greater than the thrust on the right, the hydraulic cylinder moves to the right; conversely, the hydraulic cylinder moves to the left. Since the output pressure of the accumulator 70 can be considered basically constant within a certain range if the accumulator 70 has sufficient capacity, the left or right movement of the hydraulic cylinder can be controlled by adjusting the output of the hydraulic servo pump group 20.

[0065] The hydraulic servo control process is described in detail below with reference to Figures 6 to 10 through multiple embodiments, in order to explain the control system configuration and bidirectional position closed-loop control method of the present invention. In these embodiments, the controlled object is a hydraulic actuator 60, wherein a linear displacement sensor 64 is installed on the hydraulic cylinder piston rod 63 to detect the current position and displacement of the hydraulic cylinder and output a position feedback signal. In the position closed-loop control, after the target position or displacement is input, a high responsiveness of hydraulic cylinder speed control is achieved, so that the instantaneous actual position of the piston rod 63 during the movement process is consistent with the target position, that is, follow-up control is achieved.

[0066] Referring to Figure 6, the control principle block diagram of the hydraulic servo control method according to the present invention can be divided into a servo pump control module, a hydraulic actuation control module, and a position feedback module.

[0067] The servo pump control module, or servo pump control unit, consists of a control model for a servo driver, a servo motor, and an oil pump 21. The servo driver uses vector control principles to drive the servo motor, exhibiting high responsiveness and high linearity. It incorporates position control, speed control, vector control, and PWM output components, performing the necessary calculations for position control and adjusting the hydraulic pressure output by the oil pump 21 through the output torque of the servo motor.

[0068] The hydraulic actuation control module is the execution element, which is provided by the physical model between the cylinder, piston, hydraulic fluid and accumulator, involving the speed and position changes of the piston rod 63 caused by oil flow, pressure or viscous force.

[0069] The position feedback module uses the sampled signal from the linear displacement sensor 64 as the feedback loop for position closed-loop control.

[0070] The target given position is subtracted from the feedback from the position feedback module, and then passed through the servo pump control module and the hydraulic actuation control module in sequence to output the position control result. The input of the position feedback module comes from the output of the hydraulic actuation control module.

[0071] Referring now to Figures 6 and 7, in some embodiments, the hydraulic servo control method according to the present invention may specifically include the following steps:

[0072] S10. The motion position feedback of the hydraulic actuator 60 is collected in real time by the displacement sensor 64.

[0073] S20. Subtract the motion position feedback of the hydraulic actuator 60 from the given position input of the hydraulic actuator 60 in the hydraulic electromechanical system to obtain the input error. After the input error is transmitted to the PID servo control loop of the hydraulic servo pump group 20, it is multiplied by the first proportional loop coefficient K1 to calculate the output flow of the hydraulic servo pump group 20 as the flow of the first oil port (left oil port 61) of the hydraulic actuator 60.

[0074] S30. The difference between the calculated flow rate of the first oil port (left oil port 61) of the hydraulic actuator 60 and the flow rate of the second oil port (right oil port 62) of the hydraulic actuator is transmitted to the hydraulic actuator control module. After the fluid volume is obtained through the integration process, it is multiplied by the elastic coefficient K2 to calculate the hydraulic pressure. Then, the hydraulic pressure is reduced by at least the piston pressure caused by the accumulator 70, or further reduced by the internal resistance of the hydraulic actuator 60, to obtain the pressure difference.

[0075] S40. After multiplying the pressure difference by the second proportional element coefficient K3, the movement speed of the piston rod 63 of the hydraulic actuator 60 is calculated by the integral element.

[0076] S50. The calculated motion speed of the hydraulic actuator 60 is integrated to calculate the motion position output of the hydraulic actuator 60.

[0077] Step S20 mainly involves the control flow of the servo pump control module. In the PID servo control loop of the hydraulic servo pump group 20, the motion position feedback quantity is multiplied by the outer loop gain coefficient to obtain the given motor speed, which is then processed through the speed loop control loop to calculate the motor speed. Since the hydraulic pump can be equivalent to a linear speed input and flow output model, the calculated motor speed is multiplied by the first proportional element coefficient K1 of the hydraulic pump model to calculate the output flow of the hydraulic servo pump group 20.

[0078] Steps S30 and S40 are the control flow of the hydraulic actuation control module. As shown in Figure 5, the piston divides the cylinder into a first port side (left side) and a second port side (right side). The output flow of the hydraulic servo pump group 20 acts on the left side, while the energy storage flow of the accumulator 70 acts on the right side. Therefore, the flow rate at the right port 62 of the hydraulic actuator 60 is calculated by multiplying the movement speed of the hydraulic actuator 60 by the cross-sectional area coefficient K5 of the cylinder (basically the right side) of the hydraulic actuator 60, and this flow rate difference is used to calculate the flow rate difference.

[0079] Furthermore, the resistance inside the hydraulic actuator 60 includes the viscous force generated by the cylinder and piston, which is calculated by multiplying the movement speed of the hydraulic actuator 60 by the viscosity coefficient K4 of the cylinder. The piston pressure caused by the accumulator 70 is calculated by multiplying the hydraulic pressure of the accumulator (referred to as hydraulic pressure) by the cross-sectional area of ​​the piston inside the cylinder.

[0080] Since the oil pump 21 generally cannot operate in reverse, and even if it could, it would exhibit nonlinear characteristics near the zero-speed region, if the oil pump 21 were to operate bidirectionally, it could not be considered a linear component in the system like a servo motor, thus disrupting the system's control characteristics. Therefore, the control and execution components of the method according to the present invention include an auxiliary component where the accumulator 70 provides resistance.

[0081] In a preferred embodiment, the hydraulic actuator 60 can also be made to operate in the linear region by adjusting the oil pressure of the hydraulic servo pump group 20 and the accumulator.

[0082] Referring to Figure 8, the physical quantities are set as follows: maximum operating oil pressure Pmax of the system, output oil pressure Po of hydraulic servo pump group 20, operating oil pressure Pe of accumulator 70, effective area Sl on the left side of the hydraulic cylinder piston, effective area Sr on the right side, force F1 acting on the left side of the piston with area Sl, and force F2 acting on the right side of the piston with area Sr. Then the resultant force acting on piston rod 63 is F = F1 - F2 = Po * Sl – Pe * Sr. Therefore, F can be positive or negative, and the value and direction of F can be changed by adjusting Po.

[0083] When Po = Pmax, F is the positive maximum value of Pmax*Sl - Pe*Sr; when Po = 0, F is the maximum negative value of Pe*Sr. Since Pmax, Sl, and Sr are all constants, by selecting an appropriate Pe, the positive and negative maximum values ​​of F are equal, and the hydraulic cylinder has the largest bidirectional force adjustment range. When the output pressure Pe of the accumulator 70 is basically constant at 50% of Pmax, the oil pump 21 only needs to rotate forward to adjust the output force Po to adjust the magnitude and direction of F. The oil pump 21 does not need to rotate in reverse, so it basically operates in the linear region and can be regarded as a linear element in the control process.

[0084] When Po changes between 0 and Pmax, F changes linearly between its negative and positive maximum values. When F = 0, according to Po = (Sr / Sl)*Pe, if Sr and Sl are approximately close, Po is approximately 50% of Pmax. Therefore, within this pressure range between 0 and Pmax, the oil pump 21 exhibits linear and sensitive characteristics, making it a good actuator. The entire control closed loop displays excellent control characteristics, enabling high-precision position control.

[0085] Based on the above-described hydraulic pressure optimization and adjustment, in a preferred embodiment, the control method according to the present invention can be summarized as the control block diagram shown in Figure 9. Accordingly, the control method according to the present invention includes the following steps:

[0086] S1. Switch the first directional valve 30 to connect the left oil port 61 of the hydraulic actuator 60 to the hydraulic servo pump group 20, switch the second directional valve 50 and open the third directional valve 90 to connect the right oil port 62 of the hydraulic actuator 60 to the accumulator 70, and collect the motion position feedback of the hydraulic actuator 60 in real time through the displacement sensor 64.

[0087] S2. Subtract the motion position feedback of the hydraulic actuator 60 from the given position input of the hydraulic actuator 60 in the hydraulic electromechanical system to obtain the input error. Transmit the input error to the PID servo control loop of the hydraulic servo pump group 20 to calculate the speed of the servo motor.

[0088] S3.1. The speed of the servo motor is multiplied by the first proportional element coefficient K1 to calculate the output flow of the hydraulic servo pump group 20, which is used as the flow of the left oil port 61 of the hydraulic actuator 60.

[0089] S3.2 The difference between the calculated flow rate at the left port 61 of the hydraulic actuator 60 and the flow rate at the right port 62 of the hydraulic actuator is transmitted to the hydraulic actuator control module. After the fluid volume is obtained through the integration process, it is multiplied by the elastic coefficient K2 to calculate the hydraulic pressure. Then, the hydraulic pressure is multiplied by the proportional coefficient 1 / K4 to calculate the piston acceleration.

[0090] S3.3 The piston acceleration is passed through a first-order inertial element to calculate the movement speed of the piston rod 63 of the hydraulic actuator 60. The transfer function of the first-order inertial element is G0(s)=(1 / (1+T1·s)), where T1=1 / (K3·K4).

[0091] S4. The calculated motion speed of the hydraulic actuator 60 is integrated to calculate the motion position output of the hydraulic actuator 60.

[0092] In a preferred embodiment, the control method according to the present invention can be further simplified to the control block diagram of FIG. 10. Accordingly, the control method according to the present invention includes the following steps:

[0093] S1. Switch the first directional valve 30 to connect the left oil port 61 of the hydraulic actuator 60 to the hydraulic servo pump group 20, switch the second directional valve 50 and open the third directional valve 90 to connect the right oil port 62 of the hydraulic actuator 60 to the accumulator 70, and collect the motion position feedback of the hydraulic actuator 60 in real time through the displacement sensor 64.

[0094] S2. Subtract the motion position feedback of the hydraulic actuator 60 from the given position input of the hydraulic actuator 60 in the hydraulic electromechanical system to obtain the input error. Transmit the input error to the PID servo control loop of the hydraulic servo pump group 20 to calculate the speed of the servo motor.

[0095] S3. The rotational speed of the servo motor is calculated by the hydraulic actuation control module to obtain the movement speed of the piston rod 63 of the hydraulic actuator 60.

[0096] The transfer function of the hydraulic actuation control module

[0097] G(s)=(K1 / K5) / (1+T2·s(1+T1·s)),

[0098] Where T1 = 1 / (K3·K4), T2 = K4 / (K2·K5), K1 is the first proportional element coefficient, K2 is the elastic coefficient of the hydraulic actuator 60 cylinder, K3 is the second proportional element coefficient, K4 is the viscosity coefficient of the hydraulic actuator 60 cylinder, K5 is the cross-sectional area coefficient of the hydraulic actuator 60 cylinder, and s is the variable used as the Laplace operator.

[0099] S4. The calculated motion speed of the hydraulic actuator 60 is integrated to calculate the motion position output of the hydraulic actuator 60.

[0100] It should be understood that the method steps in the above embodiments can be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable storage medium. The method can use standard programming techniques. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if necessary, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. Furthermore, for this purpose, the program can run on a programmed application-specific integrated circuit (ASIC).

[0101] Furthermore, the procedures described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by the context. The procedures described herein (or variations and / or combinations thereof) may be executed under the control of one or more computer systems configured with executable instructions, and may be implemented by hardware or a combination thereof as code (e.g., executable instructions, one or more computer programs, or one or more applications) that commonly executes on one or more processors. The computer program comprises a plurality of instructions executable by one or more processors.

[0102] Furthermore, the method can be implemented in any suitable type of computing platform, including but not limited to personal computers, minicomputers, mainframes, workstations, networked or distributed computing environments, standalone or integrated computer platforms, or in communication with charged particle tools or other imaging devices, etc. Aspects of the invention can be implemented as machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it is readable by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the processes described herein. Furthermore, the machine-readable code, or portions thereof, can be transmitted via wired or wireless networks. The invention described herein includes these and other different types of non-transitory computer-readable storage media when such media comprises instructions or programs that implement the steps described above in conjunction with a microprocessor or other data processor. When programmed according to the methods and techniques described in the invention, the invention may also include the computer itself.

[0103] A computer program can be applied to input data to perform the functions described herein, thereby transforming the input data to generate output data stored in non-volatile memory. The output information can also be applied to one or more output devices, such as a display. In a preferred embodiment of the invention, the transformed data represents physical and tangible objects, including specific visual depictions of physical and tangible objects generated on the display.

[0104] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, as long as they achieve the technical effects of the present invention by the same means, should be included within the scope of protection of the present invention. Within the scope of protection of the present invention, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. A hydraulic electromechanical system, characterized in that, include: A hydraulic servo pump assembly (20) having a servo motor to drive an oil pump (21) to deliver oil from an oil tank (10); A first directional valve (30) having a first main oil port, a second main oil port, an inlet oil port, and a return oil port, wherein the inlet oil port of the first directional valve (30) is connected to the hydraulic servo pump assembly (20), and the return oil port of the first directional valve (30) is connected to the oil tank (10); a check valve (40) having an inlet port and an outlet port, wherein oil is restricted from being transferred from the inlet port to the outlet port within the check valve (40), and the inlet oil port of the check valve (40) is connected to the second main oil port of the first directional valve (30); a second directional valve (50) having a first main oil port, a second main oil port, an inlet oil port, and a return oil port, wherein the inlet oil port of the second directional valve (50) is connected to the outlet port of the check valve (40), and the return oil port of the second directional valve (50) is connected to the oil tank (10); a hydraulic actuator (6) 0), the hydraulic actuator (60) has a cylinder body, a first oil port, a second oil port and a piston located in the cylinder body between the first oil port and the second oil port, wherein the first oil port of the hydraulic actuator (60) is connected to the first main oil port of the first directional valve (30) and the second oil port of the hydraulic actuator (60) is connected to the second main oil port of the second directional valve (50); a third directional valve (90) has a first port and a second port, which is cut off when the third directional valve (90) is closed and remains connected when the third directional valve (90) is open, wherein the first port of the third directional valve (90) is connected to the output port of the check valve (40); an accumulator (70) is connected to the second port of the third directional valve (90).

2. The hydraulic electromechanical system according to claim 1, characterized in that: The first directional valve (30) includes a first one-way position, a first stop position (32) and a first two-way position. In the first one-way position, the first main oil port is connected to the oil inlet and the second main oil port is connected to the oil return port. In the first stop position (32), the first main oil port is cut off from the oil inlet and both the first and second main oil ports are connected to the oil return port. In the first two-way position, the first main oil port is connected to the oil return port and the second main oil port is connected to the oil inlet. The second directional valve (50) includes a second one-way position, a second stop position (52) and a second two-way position. In the second one-way position, the first main oil port is connected to the oil inlet and the second main oil port is connected to the oil return port. In the second stop position (52), the first main oil port is cut off from the oil inlet and the second main oil port is cut off from the oil return port. In the second two-way position, the first main oil port is connected to the oil return port and the second main oil port is connected to the oil inlet.

3. The hydraulic electromechanical system according to claim 1, characterized in that, include: A pressure relief valve (80) is provided, the input end of which is connected to the accumulator (70), and the output end of which is connected to the oil tank (10).

4. The hydraulic electromechanical system according to claim 1, characterized in that, The hydraulic actuator (60) includes: a piston rod (63) connected to the piston; and a displacement sensor (64) connected to the piston rod (63) for acquiring position information of the piston rod (63).

5. The hydraulic electromechanical system according to any one of claims 1 to 4, characterized in that, The motor of the hydraulic servo pump unit (20) drives a single oil pump (21) to work in a unidirectional rotational manner.

6. A hydraulic servo control method, used in the hydraulic electromechanical system according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S10, switching the first directional valve (30) to connect the first oil port of the hydraulic actuator (60) to the hydraulic servo pump group (20), switching the second directional valve (50) and opening the third directional valve (90) to connect the second oil port of the hydraulic actuator (60) to the accumulator (70), and collecting the motion position feedback of the hydraulic actuator (60) in real time through the displacement sensor (64); S20, subtracting the motion position feedback of the hydraulic actuator (60) from the given position input of the hydraulic actuator (60) of the hydraulic electromechanical system as the input error, transmitting the input error to the PID servo control loop of the hydraulic servo pump group (20), and then multiplying by the first proportional element coefficient (K1) to calculate the hydraulic servo pump group. (20) output flow rate is used as the first port flow rate of hydraulic actuator (60); S30, the difference between the calculated first port flow rate of hydraulic actuator (60) and the second port flow rate of hydraulic actuator is transmitted to hydraulic actuator control module, and after the fluid volume is obtained through integration, it is multiplied by the elastic coefficient (K2) to calculate hydraulic pressure, and then the hydraulic pressure is reduced by at least the piston pressure caused by accumulator (70), or further reduced by the internal resistance of hydraulic actuator (60) to obtain pressure difference; S40, the pressure difference is multiplied by the second proportional link coefficient (K3) and then integrated to calculate the movement speed of hydraulic actuator (60); S50, the calculated movement speed of hydraulic actuator (60) is integrated to calculate the movement position output of hydraulic actuator (60).

7. The method according to claim 6, characterized in that: The flow rate of the second port of the hydraulic actuator (60) is calculated by multiplying the movement speed of the hydraulic actuator (60) and the cross-sectional area coefficient (K5) of the cylinder of the hydraulic actuator (60); the resistance inside the hydraulic actuator (60) includes the viscous force generated by the cylinder and the piston, which is calculated by multiplying the movement speed of the hydraulic actuator (60) and the viscosity coefficient (K4) of the cylinder; the piston pressure caused by the accumulator (70) is calculated by multiplying the hydraulic pressure of the accumulator by the cross-sectional area of ​​the piston in the cylinder.

8. A hydraulic servo control method, used in the hydraulic electromechanical system according to any one of claims 1 to 5, characterized in that, The method includes the following steps: S1, switching the first directional valve (30) to connect the first oil port of the hydraulic actuator (60) to the hydraulic servo pump group (20), switching the second directional valve (50) and opening the third directional valve (90) to connect the second oil port of the hydraulic actuator (60) to the accumulator (70), and collecting the motion position feedback of the hydraulic actuator (60) in real time through the displacement sensor (64); S2, subtracting the motion position feedback of the hydraulic actuator (60) from the given position input of the hydraulic actuator (60) of the hydraulic electromechanical system as the input error, and transmitting the input error to the PID servo control loop of the hydraulic servo pump group (20) to calculate the speed of the servo motor; S3, transferring the servo motor to the PID servo control loop of the hydraulic servo pump group (20) to calculate the speed of the servo motor. The motor speed is calculated by the hydraulic actuator control module to obtain the movement speed of the hydraulic actuator (60). The transfer function of the hydraulic actuator control module is G(s)=(K1 / K5) / (1+T2·s(1+T1·s)), where T1=1 / (K3·K4), T2=K4 / (K2·K5), K1 is the first proportional element coefficient, K2 is the elastic coefficient of the hydraulic actuator (60) cylinder, K3 is the second proportional element coefficient, K4 is the viscosity coefficient of the hydraulic actuator (60) cylinder, K5 is the cross-sectional area coefficient of the hydraulic actuator (60) cylinder, and s is a variable; S4, the calculated movement speed of the hydraulic actuator (60) is passed through the integral element to calculate the movement position output of the hydraulic actuator (60).

9. The method according to any one of claims 6 to 8, characterized in that, Includes the following steps: Close the third directional valve (90), switch the first directional valve (30) to the first one-way position so that the first port of the hydraulic actuator (60) is connected to the hydraulic servo pump group (20), switch the second directional valve (50) to the second two-way position so that the second port of the hydraulic actuator (60) is connected to the oil tank (10), and then trigger the servo motor of the hydraulic servo pump group (20) to rotate to output flow, so that the hydraulic actuator (60) outputs movement from the first port to the second port; or close the third directional valve (90), switch the first directional valve (30) to the first two-way position so that the first port of the hydraulic actuator (60) is connected to the oil tank (10), switch the second directional valve (50) to the second two-way position so that the first port of the hydraulic actuator (60) is connected to the oil tank (10), and ... 0) The hydraulic actuator (60) is connected to the hydraulic servo pump group (20) by the second port of the hydraulic actuator (60) in the second first-way position, and the servo motor of the hydraulic servo pump group (20) is triggered to rotate to output flow, so that the hydraulic actuator (60) outputs movement from the second port to the first port; or the third directional valve (90) is opened, the first directional valve (30) is switched to the first two-way position so that the output port of the hydraulic servo pump group (20) is connected to the accumulator (70) through the check valve (40), and the second directional valve (50) is switched to the second cut-off position (52), and the servo motor of the hydraulic servo pump group (20) is triggered to rotate to output flow, so that the accumulator (70) stores energy.

10. A computer device comprising a memory and a processor, characterized in that, When the processor executes a computer program stored in the memory, it performs the method as described in any one of claims 1 to 9.

Images