Pump-controlled hydraulic system for a surface grinder and method for controlling the same

Abstract

The application provides a pump-controlled hydraulic system for a surface grinder and a control method thereof, and relates to the technical field of surface grinders.The pump-controlled hydraulic system comprises a servo motor, a bidirectional constant-displacement pump, a double-acting hydraulic cylinder, a speed sensor, a force sensor, a flow sensor, a first pressure sensor, a second pressure sensor, a super capacitor, an accumulator, a voltage sensor and a controller.The flow sensor, the first pressure sensor and the second pressure sensor are arranged on a pipeline between the bidirectional constant-displacement pump and the double-acting hydraulic cylinder.The speed sensor and the force sensor are connected with a cylinder rod of the double-acting hydraulic cylinder.The super capacitor is connected with the servo motor, and the voltage sensor is connected with the super capacitor.The application converts kinetic energy generated in the deceleration braking stage of the surface grinder into electric energy and stores the electric energy, and the electric energy is released and used when the surface grinder works externally, so that energy loss is effectively avoided, and the working time of the system is prolonged.

Description

Technical Field

[0001] This invention relates to the field of surface grinding technology, and in particular to a pump-controlled hydraulic system and its control method for surface grinding. Background Technology

[0002] A surface grinder is a machine tool that uses an abrasive wheel to grind the surface of a workpiece. Traditional surface grinders use a valve-controlled hydraulic system for workpiece feeding. In this system, flow losses occur at the orifices and gaps of the valve components, resulting in significant energy loss. Furthermore, during the deceleration and braking phase of the workpiece feeding system, the system contains a large amount of kinetic energy, which is dissipated as heat through throttling and overflow losses. Due to these two energy losses, traditional valve-controlled surface grinder hydraulic systems have low energy efficiency and generate significant heat, requiring high-power oil cooling equipment, leading to high installation costs and low integration. Summary of the Invention

[0003] The purpose of this invention is to provide a pump-controlled hydraulic system and its control method for a surface grinder, which maximizes the conversion of the kinetic energy generated during the deceleration and braking phase of the surface grinder into electrical energy for storage, and releases and uses it when the surface grinder performs external work, effectively avoiding energy loss and extending the working time of the system.

[0004] A pump-controlled hydraulic system for a surface grinder includes: a servo motor, a bidirectional fixed displacement pump, a double-acting hydraulic cylinder, a speed sensor, a force sensor, a flow sensor, a first pressure sensor, a second pressure sensor, a supercapacitor, an accumulator, and a controller.

[0005] The speed sensor, the force sensor, the flow sensor, the first pressure sensor, the second pressure sensor, and the servo motor are all connected to the controller;

[0006] The output end of the servo motor is connected to the drive end of the bidirectional quantitative pump via a coupling.

[0007] The first oil outlet of the bidirectional quantitative pump is connected to the oil outlet of the accumulator and the first oil inlet of the double-acting hydraulic cylinder, respectively.

[0008] The second oil outlet of the bidirectional quantitative pump is connected to the oil outlet of the accumulator and the second oil inlet of the double-acting hydraulic cylinder, respectively.

[0009] The flow sensor and the first pressure sensor are disposed on the pipeline between the first oil outlet of the bidirectional quantitative pump and the first oil inlet of the double-acting hydraulic cylinder, and the flow sensor and the first pressure sensor are close to the bidirectional quantitative pump.

[0010] The second pressure sensor is disposed on the pipeline between the second oil outlet of the bidirectional quantitative pump and the second oil inlet of the double-acting hydraulic cylinder, and the second pressure sensor is close to the bidirectional quantitative pump;

[0011] The speed sensor and the force sensor are connected to the cylinder rod of the double-acting hydraulic cylinder;

[0012] The supercapacitor is connected to the servo motor via a DC / DC converter.

[0013] Optionally, the pump-controlled hydraulic system further includes a throttle valve and a servo energy-saving valve;

[0014] The inlet of the throttle valve is connected to the first outlet of the bidirectional metering pump;

[0015] The oil outlet of the throttle valve is connected to the oil inlet of the servo energy-saving valve.

[0016] The oil outlet of the servo energy-saving valve is connected to the second oil outlet of the bidirectional quantitative pump.

[0017] Optionally, the pump-controlled hydraulic system further includes a first relief valve and a second relief valve;

[0018] The oil outlet of the accumulator is connected to the first oil outlet of the bidirectional quantitative pump through the first overflow valve, that is, the oil outlet of the accumulator is connected to the oil outlet of the first overflow valve, and the oil inlet of the first overflow valve is connected to the first oil outlet of the bidirectional quantitative pump.

[0019] The oil outlet of the accumulator is connected to the second oil outlet of the bidirectional quantitative pump through the second overflow valve, that is, the oil outlet of the accumulator is connected to the oil outlet of the second overflow valve, and the oil inlet of the second overflow valve is connected to the second oil outlet of the bidirectional quantitative pump.

[0020] Optionally, the pump-controlled hydraulic system further includes a first two-way check valve and a second two-way check valve;

[0021] The oil outlet of the accumulator is connected to the first oil outlet of the bidirectional quantitative pump through the first two-way check valve, that is, the oil outlet of the accumulator is connected to the oil inlet of the first two-way check valve, and the oil outlet of the first two-way check valve is connected to the first oil outlet of the bidirectional quantitative pump.

[0022] The oil outlet of the accumulator is connected to the second oil outlet of the bidirectional quantitative pump through the second two-way check valve, that is, the oil outlet of the accumulator is connected to the oil inlet of the second two-way check valve, and the oil outlet of the second two-way check valve is connected to the second oil outlet of the bidirectional quantitative pump.

[0023] A control method for the above-mentioned pump-controlled hydraulic system, comprising:

[0024] S1, the movement speed of the double-acting hydraulic cylinder is obtained based on the speed sensor, and the load force of the double-acting hydraulic cylinder is obtained based on the force sensor. The power of the double-acting hydraulic cylinder is calculated based on the movement speed and the load force.

[0025] S2, determine the power of the double-acting hydraulic cylinder. If the power of the double-acting hydraulic cylinder is greater than 0, it is in the external work state and executes S3. If the power of the double-acting hydraulic cylinder is less than 0, it is in the kinetic energy recovery state and executes S4.

[0026] S3, the bidirectional fixed displacement pump is used as a hydraulic pump, and the servo motor operates as an electric motor:

[0027] The controller drives the servo motor to rotate, which in turn drives the bidirectional fixed displacement pump to rotate. The bidirectional fixed displacement pump acts as a hydraulic pump to draw in oil, and the oil discharged from the bidirectional fixed displacement pump enters one chamber of the double-acting hydraulic cylinder. The cylinder rod drives the load to reciprocate. The supercapacitor and the external power supply work together to power the servo motor.

[0028] S4, based on the rated displacement of the bidirectional fixed displacement pump, combined with the working torque of the servo motor and the working area of ​​the double-acting hydraulic cylinder, establishes an objective function to determine the optimal output power;

[0029] S5: Obtain the flow rate of the pump-controlled hydraulic system based on the flow sensor, obtain the pressure of the pump-controlled hydraulic system based on the first pressure sensor or the second pressure sensor, and calculate the power of the pump-controlled hydraulic system.

[0030] S6, determine the power of the pump-controlled hydraulic system and the optimal output power. If the power of the pump-controlled hydraulic system is greater than the optimal output power, execute S7; if it is less than, execute S8; if it is equal, execute S9.

[0031] S7 reduces the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0032] S8 increases the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0033] S9, the bidirectional quantitative pump is used as a hydraulic motor, and the servo motor is in generator mode: the controller applies the kinetic energy of the surface grinder during deceleration as a load force to one chamber of the double-acting hydraulic cylinder, so that the oil flowing out of the other chamber of the double-acting hydraulic cylinder enters the bidirectional quantitative pump, drives the bidirectional quantitative pump to rotate, and makes the bidirectional quantitative pump act as a hydraulic motor to drive the servo motor to rotate, and then stores the generated electrical energy in the supercapacitor.

[0034] Optionally, the power calculation formula for a double-acting hydraulic cylinder is as follows:

[0035] P = F·v;

[0036] In the formula: P is the power of the double-acting hydraulic cylinder, F is the load force of the double-acting hydraulic cylinder, and v is the movement speed of the double-acting hydraulic cylinder.

[0037] Optionally, the power calculation formula for the pump-controlled hydraulic system is as follows:

[0038] P1 = p·q;

[0039] In the formula: P1 is the power of the pump-controlled hydraulic system, p is the pressure of the pump-controlled hydraulic system, and q is the flow rate of the pump-controlled hydraulic system.

[0040] Optionally, the control method further includes:

[0041] Determine the load force of a double-acting hydraulic cylinder;

[0042] If the change in load force of the double-acting hydraulic cylinder is positive and the absolute value is greater than the set threshold, the controller adjusts the voltage signal to reduce the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0043] If the change in load force of the double-acting hydraulic cylinder is negative and its absolute value is greater than the set threshold, the controller adjusts the voltage signal to increase the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0044] Optionally, the supercapacitor first performs constant current charging. When the terminal voltage reaches the set voltage value, the supercapacitor switches to constant voltage charging mode until the supercapacitor voltage is constant.

[0045] The effects of this invention are as follows:

[0046] 1. The present invention relates to a pump-controlled hydraulic system for a surface grinder, wherein a bidirectional fixed displacement pump is coaxially driven by a servo motor and connected in parallel with a servo energy-saving valve to supply oil to the system; an overflow valve is installed between the main oil circuit and the intermediate return oil circuit to ensure that the system can be safely unloaded and to prevent the maximum system pressure from exceeding the set pressure; after the external accumulator is charged, it is connected to replenish oil to the system, which reduces the failure rate and improves the reliability of the system.

[0047] 3. The control method of the pump-controlled hydraulic system of the present invention is based on the rated displacement of the bidirectional fixed displacement pump, combined with the working torque of the servo motor and the working area of ​​the double-acting hydraulic cylinder, to establish an objective function, determine the optimal output power, and determine the optimal output power according to the load change under the current working conditions, so as to achieve the best kinetic energy recovery effect of the system.

[0048] 3. This invention uses a supercapacitor to convert the kinetic energy generated by the surface grinder during the deceleration and braking phase into electrical energy for storage, and releases and uses it when the surface grinder performs external work, which greatly improves the energy utilization rate of the system. Attached Figure Description

[0049] Figure 1 This is a structural diagram of the pump-controlled hydraulic system for a surface grinder according to the present invention;

[0050] Figure 2 This is a schematic diagram of the pump-controlled hydraulic system for a surface grinder according to the present invention;

[0051] Figure 3 This is a flowchart of the control method for the pump-controlled hydraulic system of the present invention;

[0052] Figure 4 This is a schematic diagram of the time-motion speed / load force change of the pump-controlled hydraulic system of the present invention;

[0053] Figure 5 This is a schematic diagram of the time-energy change of the supercapacitor of the present invention.

[0054] In the diagram: 1. Servo motor; 2. Bidirectional quantitative pump; 3. Double-acting hydraulic cylinder; 4. Speed ​​sensor; 5. Force sensor; 6. Flow sensor; 7. First pressure sensor; 8. Second pressure sensor; 9. Supercapacitor; 10. Accumulator; 11. Controller; 12. Throttle valve; 13. Servo energy-saving valve; 14. First relief valve; 15. Second relief valve; 16. First two-way check valve; 17. Second two-way check valve; 18. DC / DC converter; 19. Driver. Detailed Implementation

[0055] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0056] Figure 1 This is a structural diagram of the pump-controlled hydraulic system for a surface grinder according to the present invention; Figure 2 This is a schematic diagram of the pump-controlled hydraulic system for a surface grinder according to the present invention. Figure 1 and Figure 2 As shown, the present invention provides a pump-controlled hydraulic system for a surface grinder, comprising: a servo motor 1, a bidirectional fixed displacement pump 2, a double-acting hydraulic cylinder 3, a speed sensor 4, a force sensor 5, a flow sensor 6, a first pressure sensor 7, a second pressure sensor 8, a supercapacitor 9, an accumulator 10, and a controller 11.

[0057] Speed ​​sensor 4, force sensor 5, flow sensor 6, first pressure sensor 7, second pressure sensor 8, and servo motor 1 are all connected to controller 11.

[0058] The output end of servo motor 1 is connected to the drive end of bidirectional quantitative pump 2 via a coupling.

[0059] The first oil outlet of the bidirectional fixed displacement pump 2 is connected to the oil outlet of the accumulator 10 and the first oil inlet of the double-acting hydraulic cylinder 3, respectively.

[0060] The second outlet of the bidirectional fixed displacement pump 2 is connected to both the outlet of the accumulator 10 and the second inlet of the double-acting hydraulic cylinder 3. The accumulator 10 can replenish oil for the pump-controlled hydraulic system.

[0061] The flow sensor 6 and the first pressure sensor 7 are installed on the pipeline between the first oil outlet of the bidirectional quantitative pump 2 and the first oil inlet of the double-acting hydraulic cylinder 3, and the flow sensor 6 and the first pressure sensor 7 are close to the bidirectional quantitative pump 2.

[0062] The second pressure sensor 8 is installed on the pipeline between the second oil outlet of the bidirectional quantitative pump 2 and the second oil inlet of the double-acting hydraulic cylinder 3, and the second pressure sensor 8 is close to the bidirectional quantitative pump 2.

[0063] Speed ​​sensor 4 and force sensor 5 are connected to the cylinder rod of double-acting hydraulic cylinder 3.

[0064] The supercapacitor 9 is connected to the servo motor 1 via the DC / DC converter 18 and the driver 19. The controller 11 is connected to the servo motor 1 via the driver 19.

[0065] Furthermore, in order to adjust the outlet flow rate of the bidirectional quantitative pump 2 and effectively solve the problem of low-speed nonlinearity of the flow rate of the bidirectional quantitative pump 2, the pump control hydraulic system of the present invention also includes a throttle valve 12 and a servo energy-saving valve 13.

[0066] The inlet of the throttle valve 12 is connected to the first outlet of the bidirectional fixed displacement pump 2. The throttle valve 12 can adjust the outlet flow rate of the bidirectional fixed displacement pump 2.

[0067] The oil outlet of the throttle valve 12 is connected to the oil inlet of the servo energy-saving valve 13.

[0068] The oil outlet of the servo energy-saving valve 13 is connected to the second oil outlet of the bidirectional fixed displacement pump 2. The servo energy-saving valve 13 can effectively solve the problem of low-speed nonlinear flow of the bidirectional fixed displacement pump 2.

[0069] Furthermore, to provide overflow protection in emergency situations, the pump-controlled hydraulic system of the present invention also includes a first overflow valve 14 and a second overflow valve 15. The first overflow valve 14 and the second overflow valve 15 ensure that the system can be safely unloaded, preventing the maximum system pressure from exceeding the set pressure.

[0070] The oil outlet of the accumulator 10 is connected to the first oil outlet of the bidirectional quantitative pump 2 through the first overflow valve 14, that is, the oil outlet of the accumulator 10 is connected to the oil outlet of the first overflow valve 14, and the oil inlet of the first overflow valve 14 is connected to the first oil outlet of the bidirectional quantitative pump 2.

[0071] The oil outlet of the accumulator 10 is connected to the second oil outlet of the bidirectional quantitative pump 2 through the second overflow valve 15. That is, the oil outlet of the accumulator 10 is connected to the oil outlet of the second overflow valve 15, and the oil inlet of the second overflow valve 15 is connected to the second oil outlet of the bidirectional quantitative pump 2.

[0072] Optionally, the pump-controlled hydraulic system also includes a first two-way check valve 16 and a second two-way check valve 17.

[0073] The oil outlet of the accumulator 10 is connected to the first oil outlet of the bidirectional quantitative pump 2 through the first two-way check valve 16, that is, the oil outlet of the accumulator 10 is connected to the oil inlet of the first two-way check valve 16, and the oil outlet of the first two-way check valve 16 is connected to the first oil outlet of the bidirectional quantitative pump 2.

[0074] The oil outlet of the accumulator 10 is connected to the second oil outlet of the bidirectional quantitative pump 2 through the second two-way check valve 17. That is, the oil outlet of the accumulator 10 is connected to the oil inlet of the second two-way check valve 17, and the oil outlet of the second two-way check valve 17 is connected to the second oil outlet of the bidirectional quantitative pump 2.

[0075] The first two-way check valve 16 and the second two-way check valve 17 can provide safety protection.

[0076] Figure 3 This is a flowchart of the control method for the pump-controlled hydraulic system of the present invention. (See attached flowchart.) Figure 3 As shown, the present invention provides a control method for the above-mentioned pump-controlled hydraulic system, which includes:

[0077] S1. The motion speed of the double-acting hydraulic cylinder is obtained based on the speed sensor, and the load force of the double-acting hydraulic cylinder is obtained based on the force sensor. The power of the double-acting hydraulic cylinder is calculated based on the motion speed and load force.

[0078] The power calculation formula for a double-acting hydraulic cylinder is as follows:

[0079] P = F·v;

[0080] In the formula: P is the power of the double-acting hydraulic cylinder, F is the load force of the double-acting hydraulic cylinder, and v is the movement speed of the double-acting hydraulic cylinder.

[0081] S2: Determine the power of the double-acting hydraulic cylinder. If the power of the double-acting hydraulic cylinder is greater than 0, it is in the external work state and executes S3. If the power of the double-acting hydraulic cylinder is less than 0, it is in the kinetic energy recovery state and executes S4.

[0082] S3, the bidirectional fixed displacement pump is used as a hydraulic pump, and the servo motor operates as an electric motor:

[0083] The surface grinder operates normally at the preset speed. The controller drives the servo motor to rotate, which in turn drives the bidirectional fixed displacement pump to rotate. The bidirectional fixed displacement pump, acting as a hydraulic pump, draws in oil, and the oil discharged from the pump enters one chamber of the double-acting hydraulic cylinder. The cylinder rod drives the load in reciprocating motion. The supercapacitor and an external power supply jointly power the servo motor. The supercapacitor can only supply power to the servo motor after its voltage has been tested and found to be within the specified range.

[0084] S4, based on the rated displacement of the bidirectional fixed displacement pump, combined with the working torque of the servo motor and the working area of ​​the double-acting hydraulic cylinder, establishes an objective function to determine the optimal output power. Specifically, a multi-objective optimization algorithm is used to establish the objective function and determine the optimal output power.

[0085] S5: Obtain the flow rate of the pump-controlled hydraulic system based on the flow sensor, obtain the pressure of the pump-controlled hydraulic system based on the first pressure sensor or the second pressure sensor, and calculate the power of the pump-controlled hydraulic system.

[0086] The power calculation formula for a pump-controlled hydraulic system is as follows:

[0087] P1 = p·q;

[0088] In the formula: P1 is the power of the pump-controlled hydraulic system, p is the pressure of the pump-controlled hydraulic system, and q is the flow rate of the pump-controlled hydraulic system.

[0089] S6: Determine the power of the pump-controlled hydraulic system against the optimal output power. If the power of the pump-controlled hydraulic system is greater than the optimal output power, execute S7; if it is less than the optimal output power, execute S8; if it is equal to the optimal output power, execute S9. Figure 3 In the middle, P 优 This indicates the optimal output power.

[0090] S7 reduces the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0091] S8 increases the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0092] The controller compares the power of the pump-controlled hydraulic system with the optimal output power. The resulting deviation signal is adjusted by the controller and outputs a 0-10V voltage signal to control the speed of the servo motor, thereby further controlling the flow rate of the pump-controlled hydraulic system.

[0093] S9, the bidirectional quantitative pump is used as a hydraulic motor, and the servo motor is in generator mode: the controller applies the kinetic energy of the surface grinder during deceleration as a load force to one chamber of the double-acting hydraulic cylinder, so that the oil flowing out of the other chamber of the double-acting hydraulic cylinder enters the bidirectional quantitative pump, drives the bidirectional quantitative pump to rotate, and makes the bidirectional quantitative pump act as a hydraulic motor to drive the servo motor to rotate, and then stores the generated electrical energy in the supercapacitor.

[0094] The supercapacitor first enters constant current charging mode. When the terminal voltage reaches the set voltage value, the supercapacitor switches to constant voltage charging mode until the supercapacitor voltage is constant. This reduces the energy loss caused by voltage division due to the internal resistance of the supercapacitor, allowing the supercapacitor to obtain maximum energy within a certain period of time and ensuring that the charging efficiency of the pump-controlled hydraulic system is maximized during kinetic energy recovery.

[0095] Optionally, to ensure that the power of the pump-controlled hydraulic system remains at its optimal output power under current operating conditions, the control method also includes:

[0096] Determine the load force of a double-acting hydraulic cylinder.

[0097] If the change in load force of the double-acting hydraulic cylinder is positive and the absolute value is greater than the set threshold, the controller adjusts the voltage signal to reduce the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0098] If the change in load force of the double-acting hydraulic cylinder is negative and its absolute value is greater than the set threshold, the controller adjusts the voltage signal to increase the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

[0099] Specifically, using the pump-controlled hydraulic system and control method of this invention for a surface grinder, the time-speed / load force change is as follows: Figure 4 As shown, the time-energy change of a supercapacitor is as follows: Figure 5 As shown, when the pump-controlled hydraulic system is in the state of performing external work, the electrical energy decreases; when the pump-controlled hydraulic system is in the state of kinetic energy recovery, the electrical energy increases.

[0100] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A pump-controlled hydraulic system for a surface grinder, characterized in that, It includes: servo Motor, bidirectional fixed displacement pump, double-acting hydraulic cylinder, speed sensor, force sensor, flow sensor, first pressure sensor, second pressure sensor, supercapacitor, accumulator and controller; The speed sensor, the force sensor, the flow sensor, the first pressure sensor, the second pressure sensor, and the servo motor are all connected to the controller; The output end of the servo motor is connected to the drive end of the bidirectional quantitative pump via a coupling. The first oil outlet of the bidirectional quantitative pump is connected to the oil outlet of the accumulator and the first oil inlet of the double-acting hydraulic cylinder, respectively. The second oil outlet of the bidirectional quantitative pump is connected to the oil outlet of the accumulator and the second oil inlet of the double-acting hydraulic cylinder, respectively. The flow sensor and the first pressure sensor are disposed on the pipeline between the first oil outlet of the bidirectional quantitative pump and the first oil inlet of the double-acting hydraulic cylinder, and the flow sensor and the first pressure sensor are close to the bidirectional quantitative pump. The second pressure sensor is disposed on the pipeline between the second oil outlet of the bidirectional quantitative pump and the second oil inlet of the double-acting hydraulic cylinder, and the second pressure sensor is close to the bidirectional quantitative pump; The speed sensor and the force sensor are connected to the cylinder rod of the double-acting hydraulic cylinder; The supercapacitor is connected to the servo motor via a DC / DC converter. The control method for a pump-controlled hydraulic system includes the following steps: S1, the movement speed of the double-acting hydraulic cylinder is obtained based on the speed sensor, and the load force of the double-acting hydraulic cylinder is obtained based on the force sensor. The power of the double-acting hydraulic cylinder is calculated based on the movement speed and the load force. S2, determine the power of the double-acting hydraulic cylinder. If the power of the double-acting hydraulic cylinder is greater than 0, it is in the external work state and executes S3. If the power of the double-acting hydraulic cylinder is less than 0, it is in the kinetic energy recovery state and executes S4. S3, the bidirectional fixed displacement pump is used as a hydraulic pump, and the servo motor operates as an electric motor: The controller drives the servo motor to rotate, which in turn drives the bidirectional fixed displacement pump to rotate. The bidirectional fixed displacement pump acts as a hydraulic pump to draw in oil, and the oil discharged from the bidirectional fixed displacement pump enters one chamber of the double-acting hydraulic cylinder. The cylinder rod drives the load to reciprocate. The supercapacitor and the external power supply work together to power the servo motor. S4, based on the rated displacement of the bidirectional fixed displacement pump, combined with the working torque of the servo motor and the working area of ​​the double-acting hydraulic cylinder, establishes an objective function to determine the optimal output power; S5: Obtain the flow rate of the pump-controlled hydraulic system based on the flow sensor, obtain the pressure of the pump-controlled hydraulic system based on the first pressure sensor or the second pressure sensor, and calculate the power of the pump-controlled hydraulic system. S6, determine the power of the pump-controlled hydraulic system and the optimal output power. If the power of the pump-controlled hydraulic system is greater than the optimal output power, execute S7; if it is less than, execute S8; if it is equal, execute S9. S7 reduces the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power. S8 increases the speed of the servo motor by adjusting the voltage signal through the controller, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power. S9, the bidirectional quantitative pump is used as a hydraulic motor, and the servo motor is in generator mode: the controller applies the kinetic energy of the surface grinder during deceleration as a load force to one chamber of the double-acting hydraulic cylinder, so that the oil flowing out of the other chamber of the double-acting hydraulic cylinder enters the bidirectional quantitative pump, drives the bidirectional quantitative pump to rotate, and makes the bidirectional quantitative pump act as a hydraulic motor to drive the servo motor to rotate, and then stores the generated electrical energy in the supercapacitor.

2. The pump-controlled hydraulic system for a surface grinder according to claim 1, characterized in that, The pump-controlled hydraulic system also includes a throttle valve and a servo energy-saving valve; The inlet of the throttle valve is connected to the first outlet of the bidirectional metering pump; The oil outlet of the throttle valve is connected to the oil inlet of the servo energy-saving valve. The oil outlet of the servo energy-saving valve is connected to the second oil outlet of the bidirectional quantitative pump.

3. The pump-controlled hydraulic system for a surface grinder according to claim 1, characterized in that, The pump-controlled hydraulic system also includes a first relief valve and a second relief valve; The oil outlet of the accumulator is connected to the first oil outlet of the bidirectional quantitative pump through the first overflow valve, that is, the oil outlet of the accumulator is connected to the oil outlet of the first overflow valve, and the oil inlet of the first overflow valve is connected to the first oil outlet of the bidirectional quantitative pump. The oil outlet of the accumulator is connected to the second oil outlet of the bidirectional quantitative pump through the second overflow valve, that is, the oil outlet of the accumulator is connected to the oil outlet of the second overflow valve, and the oil inlet of the second overflow valve is connected to the second oil outlet of the bidirectional quantitative pump.

4. The pump-controlled hydraulic system for a surface grinder according to claim 1, characterized in that, The pump-controlled hydraulic system also includes a first two-way check valve and a second two-way check valve. The oil outlet of the accumulator is connected to the first oil outlet of the bidirectional quantitative pump through the first two-way check valve, that is, the oil outlet of the accumulator is connected to the oil inlet of the first two-way check valve, and the oil outlet of the first two-way check valve is connected to the first oil outlet of the bidirectional quantitative pump. The oil outlet of the accumulator is connected to the second oil outlet of the bidirectional quantitative pump through the second two-way check valve, that is, the oil outlet of the accumulator is connected to the oil inlet of the second two-way check valve, and the oil outlet of the second two-way check valve is connected to the second oil outlet of the bidirectional quantitative pump.

5. The pump-controlled hydraulic system for a surface grinder according to claim 4, characterized in that, The power calculation formula for a double-acting hydraulic cylinder is as follows: ； In the formula: The power of the double-acting hydraulic cylinder, ν is the load force of the double-acting hydraulic cylinder, and v is the movement speed of the double-acting hydraulic cylinder.

6. The pump-controlled hydraulic system for a surface grinder according to claim 5, characterized in that, The power calculation formula for a pump-controlled hydraulic system is as follows: ； In the formula: For the power of the pump-controlled hydraulic system, For the pressure of the pump-controlled hydraulic system, This refers to the flow rate of the pump-controlled hydraulic system.

7. The pump-controlled hydraulic system for a surface grinder according to claim 5, characterized in that, The control method further includes: Determine the load force of a double-acting hydraulic cylinder; If the change in load force of the double-acting hydraulic cylinder is positive and the absolute value is greater than the set threshold, the controller adjusts the voltage signal to reduce the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power. If the change in load force of the double-acting hydraulic cylinder is negative and its absolute value is greater than the set threshold, the controller adjusts the voltage signal to increase the speed of the servo motor, thereby changing the flow rate of the bidirectional fixed displacement pump until the power of the pump-controlled hydraulic system reaches the optimal output power.

8. The pump-controlled hydraulic system for a surface grinder according to claim 5, characterized in that, The supercapacitor first enters constant current charging mode. When the terminal voltage reaches the set voltage value, the supercapacitor switches to constant voltage charging mode until the supercapacitor voltage is constant.

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