Hydraulic station for numerical control lathe and control method of hydraulic station

Abstract

The invention discloses a hydraulic station for a numerical control lathe and a control method thereof.The hydraulic station for the numerical control lathe comprises an oil tank, a driving unit, a diaphragm type energy accumulator, a filter, a high-pressure pipe and an oil separator, the driving unit comprises a servo motor, a motor fixing block, a hydraulic pump and a pressure sensor, and an output shaft of the servo motor is connected with the hydraulic pump; the pressure sensor is arranged on an output pipeline of the hydraulic pump, the flow meter is arranged on the output pipeline of the hydraulic pump, an oil inlet of the hydraulic pump is connected with the oil tank, and the output pipeline of the hydraulic pump, the diaphragm type energy accumulator, the filter, the high-pressure pipe and the oil separator are sequentially connected; the control method comprises the step that high-precision control over the hydraulic pump is achieved by adopting a feedforward-feedback composite control framework in combination with a fuzzy self-adaptive PID and a state observer. The invention aims to reduce the vibration of the hydraulic station so as to meet the requirements of industrial scenes requiring multi-physical-quantity accurate cooperative control, such as ultra-precision lathes, aerospace actuators, precision injection molding machines and the like.

Description

Technical Field

[0001] The present invention relates to a hydraulic drive technology belonging to the field of numerically controlled lathes, and in particular to a hydraulic station for numerically controlled lathes and a control method thereof. Background Art

[0002] CNC lathes are high-precision, high-efficiency automated machining equipment widely used in modern machining. They utilize a CNC system to control the machine's motion and machining processes, enabling high-precision machining of complex parts. The main components of a CNC lathe include the spindle box, feed system, tool holder, bed, and control system. Their performance and precision directly impact product quality and production efficiency.

[0003] A hydraulic station is a type of hydraulic equipment consisting of a hydraulic pump, an electric motor, a fuel tank, and solenoid valves. It provides hydraulic oil with the appropriate flow direction, pressure, and flow rate according to the needs of the drive unit. It is suitable for various machines where the drive unit is separated from the hydraulic station. By connecting the hydraulic station and the drive unit with oil pipes, the hydraulic system can achieve various predetermined movements. Hydraulic stations play a vital role in CNC lathes. Many functions of CNC lathes, such as the spindle drive, feed system, toolholder movement, clamping device, and cooling system, rely on the hydraulic station. The hydraulic station converts the hydraulic energy generated by the hydraulic pump into mechanical energy, providing power to various machine tool components. For example, the hydraulic cylinder enables rapid positioning and clamping of the toolholder, and the hydraulic motor drives the spindle for high-precision cutting. Furthermore, the hydraulic system offers advantages such as fast response, high precision, and excellent stability, meeting the stringent precision and efficiency requirements of CNC lathes.

[0004] A Chinese patent application document with publication number CN107327428A discloses a hydraulic station structure for a CNC machine tool. This device is installed on the base of the CNC machine tool and fixed to provide pressure assurance. From left to right, it is equipped with a motor, a hydraulic control valve, a pressure regulating knob, and a pressure level gauge. The motor adopts a squirrel-cage motor and is vertically mounted on the hydraulic station platform via a motor fastening flange. The hydraulic control valve is vertically fixed to the hydraulic station platform via a bolt connection. The pressure regulating knob is vertically mounted on the hydraulic station platform and adopts a clearance fit. The pressure level gauge is installed in the upper left corner. However, the squirrel-cage motor used in the motor of this device has large vibrations, which has a significant impact on the accuracy of ultra-precision lathes. It is difficult to be applied to industrial scenarios such as ultra-precision lathes, aerospace actuators, and precision injection molding machines that require precise coordinated control of multiple physical quantities. Summary of the Invention

[0005] Technical problem to be solved by the present invention: In response to the above-mentioned problems of the prior art, a hydraulic station for a CNC lathe and a control method thereof are provided. The present invention aims to reduce the vibration of the hydraulic station to meet the needs of industrial scenarios such as ultra-precision lathes, aerospace actuators, and precision injection molding machines that require precise coordinated control of multiple physical quantities.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A hydraulic station for a CNC lathe comprises an oil tank, a drive unit, a diaphragm accumulator, a filter, a high-pressure pipe and an oil separator. The drive unit comprises a servo motor, a motor fixing block, a hydraulic pump and a pressure sensor. The output shaft of the servo motor is connected to the hydraulic pump via a coupling. The pressure sensor is arranged on the output pipeline of the hydraulic pump. A flow meter is provided on the output pipeline of the hydraulic pump. The oil inlet of the hydraulic pump is connected to the oil tank. The output pipeline of the hydraulic pump, the diaphragm accumulator, the filter, the high-pressure pipe and the oil separator are connected in sequence to output hydraulic oil through the oil separator.

[0007] Optionally, the oil tank is in a cubic shape, and fixing plates are welded on both sides and the rear of the oil tank for being installed on a CNC lathe through threads. A platform side panel is provided on the outer side of the side wall of the oil tank, and a pressure level gauge, an observation port, and a refueling port are installed on the platform side panel. The flow meter is installed and fixed on the top of the oil tank, and a thermometer for detecting the temperature of the hydraulic oil is also installed and fixed on the top of the oil tank.

[0008] A control method applied to the hydraulic station for a CNC lathe, comprising: S1, the flow signal detected by the flow meter is used to obtain the feedforward signal by the feedforward controller ; S2, calculate the flow error signal E and error change rate EC, according to the flow error signal E and error change rate EC, use the fuzzy controller to dynamically correct the control parameters of the PID controller, and obtain the proportional gain K after the first correction p , integral gain K i and differential gain K d ; S3, through the third-order state observer, respectively observes the flow estimation value z1, pressure estimation value z2 and pressure change rate estimation value z3, and uses the flow estimation value z1 to correct the integral gain K of the PID controller i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d , get the second corrected proportional gain K p , integral gain K i and differential gain K d ; S4, through the PID controller based on the proportional gain K after the second correction p , integral gain K i and differential gain K d The error signal E of the input flow rate is used to obtain the corresponding reference signal, and the reference signal and the feedforward signal are combined. The sum is obtained to obtain the control voltage u of the hydraulic pump to control the working state of the hydraulic pump.

[0009] Optionally, the function expression of the feedforward controller is: , , in, is the output of the feedforward controller at time t, is the input of the feedforward controller at time t, is the feedforward transfer function of the feedforward controller, is the transfer function of the feedforward controller.

[0010] Optionally, when the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the control process of the CNC lathe machining is divided into three stages: the initial control stage, the middle control stage and the late steady-state adjustment stage. The fuzzy controller dynamically modifies the proportional gain K p The fuzzy rules used include a preset higher proportional gain K in the initial stage of control. p To utilize its fast response characteristics to improve the system's dynamic tracking capability; reduce the proportional gain K after entering the mid-term control p Weaken the proportional action intensity to suppress overshoot while maintaining system response efficiency; increase the proportional gain K again after entering the late stage of steady-state regulation p The steady-state accuracy can be improved by combining with the integral link.

[0011] Optionally, when the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the fuzzy controller dynamically modifies the integral gain K i The fuzzy rules used include a preset lower integral gain K in the initial stage of control. i To suppress the integral strength to avoid the risk of initial overshoot; gradually increase the integral gain K after entering the mid-term control i To balance the error correction requirements and the phase margin until entering the middle stage of control; continue to increase the integral gain K after entering the late stage of steady-state regulation i In order to improve the control accuracy, its cumulative error elimination characteristics are utilized.

[0012] Optionally, when the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the fuzzy controller dynamically modifies the differential gain K dThe fuzzy rules used include a preset higher differential gain K in the initial stage of control. d In order to utilize its advanced compensation effect to effectively suppress overshoot and enhance the rapid response; after entering the mid-term control, reduce the differential gain K d To balance the contradiction between dynamic correction requirements and noise sensitivity; after entering the late stage of steady-state regulation, increase the differential gain K again d To form a secondary damping enhancement mechanism to improve anti-interference ability.

[0013] Optionally, the function expression of the third-order state observer is: , , , , , , , , , in, ~ are the first, second, third and fourth control state variables of the hydraulic station, is the flow rate of the hydraulic station, is the internal pipeline pressure of the hydraulic station, is the pressure change in the internal pipeline of the hydraulic station, is the total disturbance, The relative control voltage of the hydraulic station flow The partial derivative of is the flow gain of the hydraulic pump, is the pressure difference between the inlet and outlet of the hydraulic pump, ~ for ~ The derivative of is the flow change of the hydraulic station, To control the voltage variation, is the change of flow disturbance, is the effective bulk modulus of the oil, is the effective volume of the control chamber of the hydraulic pump, is the load flow, is the pressure estimation error, Estimated flow rate The first derivative of Estimated pressure value The first derivative of is the estimated value of the pressure change rate The first derivative of is the disturbance estimate The first derivative of ~ is an intermediate variable, is the bandwidth of the third-order state observer.

[0014] Optionally, the flow estimation value z1 is used to modify the integral gain K of the PID controller. i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d Includes: If the flow estimate z1 increases, reduce the integral gain K i To improve steady-state accuracy, if the flow estimate z1 decreases, increase the integral gain K i Otherwise, reduce the integral gain K i To improve stability; if the pressure estimate z2 increases, reduce the proportional gain K p Otherwise, increase the proportional gain K p To avoid overshoot; if the pressure change rate estimate z3 exceeds the preset threshold, increase the differential gain K d Otherwise, reduce the differential gain K d To suppress vibration.

[0015] Compared with the prior art, the present invention can mainly achieve the following beneficial effects: in order to reduce the vibration of the hydraulic station and meet the needs of industrial scenarios such as ultra-precision lathes, aerospace actuators, and precision injection molding machines that require precise coordinated control of multiple physical quantities, the hydraulic station of the present invention for CNC lathes includes an oil tank, a drive unit, a diaphragm accumulator, a filter, a high-pressure pipe and an oil separator. The drive unit includes a servo motor, a motor fixing block, a hydraulic pump and a pressure sensor. The output shaft of the servo motor is connected to the hydraulic pump through a coupling. The pressure sensor is arranged on the output pipeline of the hydraulic pump. A flow meter is provided on the output pipeline of the hydraulic pump. The oil inlet of the hydraulic pump is connected to the oil tank, and the output pipeline of the hydraulic pump, the diaphragm accumulator, the filter, the high-pressure pipe and the oil separator are connected in sequence to output the hydraulic oil through the oil separator. The present invention replaces the original squirrel cage motor with a servo motor. Compared with the original motor, the device is smaller in size, consumes less energy, and is more environmentally friendly and clean. In addition, combined with the diaphragm accumulator and the filter, it can reduce the vibration of the hydraulic station, make it easier to realize digital integration, and complete rapid response under different working conditions. It can meet the needs of industrial scenarios such as ultra-precision lathes, aerospace actuators, and precision injection molding machines that require precise coordinated control of multiple physical quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the three-dimensional structure of the hydraulic station according to an embodiment of the present invention.

[0017] Figure 2Schematic diagram of the three-dimensional structure of the driving unit in an embodiment of the present invention.

[0018] Figure 3 Schematic diagram of the control principle of the hydraulic station according to an embodiment of the present invention.

[0019] Legend: 1. Fixing plate; 10. Flow meter; 11. Thermometer; 12. Observation port; 13. Refueling port; 2. Pressure level gauge; 3. Platform side panel; 4. Oil separator; 5. High-pressure pipe; 6. Filter; 7. Diaphragm accumulator; 8. Drive unit; 800. Servo motor; 801. Motor fixing block; 802. Hydraulic pump; 803. Pressure sensor; 9. Fuel tank. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] like Figure 1 and Figure 2As shown, the hydraulic station for a CNC lathe in this embodiment includes an oil tank 9, a drive unit 8, a diaphragm accumulator 7, a filter 6, a high-pressure pipe 5, and an oil separator 4. The drive unit 8 includes a servo motor 800, a motor mounting block 801, a hydraulic pump 802, and a pressure sensor 803. The output shaft of the servo motor 800 is connected to the hydraulic pump 802 via a coupling. The pressure sensor 803 is arranged on the output pipeline of the hydraulic pump 802. The output pipeline of the hydraulic pump 802 is equipped with a flow meter 10. The oil inlet of the hydraulic pump 802 is connected to the oil tank 9. The output pipeline of the hydraulic pump 802, the diaphragm accumulator 7, the filter 6, the high-pressure pipe 5, and the oil separator 4 are connected in sequence to output hydraulic oil through the oil separator 4. Because the vibration of a squirrel-cage motor can affect the accuracy of an ultra-precision lathe, in this embodiment, the drive unit 8 includes a servo motor 800, a motor mounting block 801, a hydraulic pump 802, and a pressure sensor 803. The drive unit 8 is used to replace the squirrel-cage motor, and the diaphragm accumulator 7 is used for energy storage and release. The diaphragm accumulator 7 operates as follows: The diaphragm accumulator 7 comprises a sealed container separated by an elastic diaphragm into a liquid chamber and a gas chamber. When system pressure increases, hydraulic oil enters the liquid chamber through a liquid valve, compressing the gas chamber on the other side of the elastic diaphragm, reducing the gas volume and increasing the pressure, storing energy in the form of gas compression energy. When system pressure drops, the high-pressure nitrogen in the gas chamber expands, pushing the elastic diaphragm to press the hydraulic oil in the liquid chamber back into the system, replenishing flow or maintaining pressure. This embodiment uses the diaphragm accumulator 7 to temporarily store high-pressure fluid energy in the hydraulic system. When the system requires a sudden high flow rate, the diaphragm accumulator 7 releases energy to supplement the pump's insufficient fluid supply. Furthermore, the diaphragm accumulator 7 can absorb pressure shocks. When a valve is suddenly closed or a pump is started or stopped, the system may experience pressure pulsation. The diaphragm accumulator 7 absorbs the shock through compressed gas, protecting the pipelines and components.

[0022] Filter 6 reduces vibration in the hydraulic station and significantly improves space utilization. It's easy to install and suitable for space-constrained applications. Using a motor instead of a motor for oil supply effectively improves speed regulation accuracy, facilitates digital integration, and enables rapid response to varying operating conditions. Compared to conventional motors, the device consumes less energy and is more environmentally friendly and clean, meeting the needs of industrial applications requiring precise coordinated control of multiple physical quantities, such as ultra-precision lathes, aerospace actuators, and precision injection molding machines.

[0023] like Figure 1As shown, in this embodiment, the oil tank 9 is in a cubic shape, and fixed plates 1 are welded on both sides and the rear of the oil tank 9 for being installed on a CNC lathe through threads. A platform side panel 3 is provided on the outer side of the side wall of the oil tank 9, and a pressure level gauge 2, an observation port 12, and a refueling port 13 are installed on the platform side panel 3. A flow meter 10 is installed and fixed on the top of the oil tank 9. A thermometer 11 for detecting the temperature of the hydraulic oil is also installed and fixed on the top of the oil tank 9. In this embodiment, the fixed plate 1 is fixed to the machine tool via a threaded connection. The pressure level gauge 2 is vertically attached to the upper left of the oil tank 9. The oil separator 4 is horizontally mounted on the hydraulic station platform 14 and connected to the high-pressure pipe 5. The oil separator 4 is divided into three pipelines connecting different pipelines. The filter 6 is vertically fixed to the oil tank 9 via a threaded connection. The diaphragm accumulator 7 is vertically fixed to the fixed plate 1 via a threaded connection. The flow meter 10 is vertically fixed to the hydraulic station platform 14 by welding. The temperature sensor is horizontally fixed to the hydraulic station platform via a threaded connection. The drive unit 8 is horizontally fixed to the hydraulic station platform 14 via bolts. An observation port 12 is designed in the upper right corner, and the refueling port 13 is designed below the oil tank 9. In this embodiment, the servo motor 800 of the drive unit 8 is horizontally fixed to the motor fixing block 801 via bolts and connected to the hydraulic pump 802 via a coupling. The motor fixing block 801 is horizontally mounted on the hydraulic station platform 14 and connected via threads. The hydraulic pump 802 is horizontally mounted on the motor fixing block 801 and connected via threads. The pressure sensor 803 is connected to the hydraulic pump 802 via a nut and sealed with a sealing ring. Specifically, in this embodiment, the hydraulic pump 802 adopts a bidirectional gear pump. In addition, other pumps can also be used as needed. In this embodiment, the flow rate of the hydraulic pump 802 is maintained at 20-150L / min, and the pressure is set at 20-250bar. In this embodiment, a closed-loop control system consisting of the servo motor 800, the hydraulic pump 802 and the pressure sensor 803, as well as a flow meter 10 is provided on the output pipeline of the hydraulic pump 802. Among them, the servo motor 800 is directly connected to the hydraulic pump 802 via an elastic coupling to ensure that the pressure and oil volume of the oil supply are basically stable.

[0024] For the hydraulic station used for a CNC lathe in this embodiment, the motor dynamics equation and the hydraulic station flow and pressure equations can be established as follows: , , , in, is the flow rate of the hydraulic station, is the valve flow gain, is the control voltage, is the valve port pressure difference, Flow disturbances, including leakage and oil viscosity changes; is the pressure change of the pipeline in the hydraulic station, is the effective bulk modulus of the oil, To control the effective volume of the cavity, is the load flow, is the servo motor moment of inertia, and are the first-order and second-order positions of the motor angle respectively, is the motor viscous friction coefficient, is the pressure drop proportionality coefficient, is the current, It is the pressure disturbance caused by sudden load changes, including temperature and other effects.

[0025] like Figure 3 As shown, this embodiment also provides a control method for the hydraulic station for a CNC lathe, including using a feedforward-feedback composite control architecture combined with a fuzzy adaptive PID and a state observer to achieve high-precision control of the hydraulic pump 802: S1, the flow signal detected by the flow meter 10 is used to obtain a feedforward signal by a feedforward controller ; S2, calculate the flow error signal E and error change rate EC, according to the flow error signal E and error change rate EC, use the fuzzy controller to dynamically correct the control parameters of the PID controller, and obtain the proportional gain K after the first correction p , integral gain K i and differential gain K d ; S3, through the third-order state observer, respectively observes the flow estimation value z1, pressure estimation value z2 and pressure change rate estimation value z3, and uses the flow estimation value z1 to correct the integral gain K of the PID controller i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d , get the second corrected proportional gain K p , integral gain K i and differential gain K d ; S4, through the PID controller based on the proportional gain K after the second correction p , integral gain K i and differential gain K d The error signal E of the input flow rate is used to obtain the corresponding reference signal, and the reference signal and the feedforward signal are combined. The sum is used to obtain the control voltage u of the hydraulic pump 802 to control the working state of the hydraulic pump 802 .

[0026] In this embodiment, the function expression of the feedforward controller is: , , in, is the output of the feedforward controller at time t, is the input of the feedforward controller at time t, is the feedforward transfer function of the feedforward controller, is the transfer function of the feedforward controller.

[0027] In this embodiment, when calculating the flow error signal E and the error change rate EC, the error signal E is the difference between the flow signal detected by the flow meter 10 and the target flow, and the error change rate EC is the change rate of the error signal E.

[0028] The dynamic characteristics of the PID control system are mainly affected by the proportional gain K p , integral gain K i and differential gain K d The synergistic influence of the three parameters. In this embodiment, when the fuzzy controller is used to dynamically correct the control parameters of the PID controller, the control process of the CNC lathe processing is divided into three stages: the initial control stage, the middle control stage and the late steady-state adjustment stage. The fuzzy controller dynamically corrects the proportional gain K p In the fuzzy rule used, if the flow error signal E is NB and the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p are PB, PB, PM, PM, PS, ZO or ZO respectively; if the flow error signal E is NM, if the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p are PM, PB, PM, PS, PS, ZO or NS respectively; if the flow error signal E is NS, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p are PM, PM, PM, PS, ZO, ZO or NS respectively; if the flow error signal E is ZO, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p are PM, PM, PS, ZO, ZO, NS or NM respectively; if the flow error signal E is PS, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p They are PS, PM, ZO, NS, NS, NS or NM respectively; if the flow error signal E is PM, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K pare PS, PS, NS, NM, NS, NM or NB respectively; if the flow error signal E is PB, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the proportional gain K p They are ZO, ZO, NS, NM, NM, NM or NB, as shown in Table 1.

[0029] Table 1: Dynamic correction proportional gain K p Fuzzy rule table used

[0030] See Table 1. In this embodiment, the proportional gain K p The time-varying characteristics of the control are optimized: a preset higher proportional gain K is used in the initial stage of control. p , using its fast response characteristics to improve the system's dynamic tracking capability; appropriately reduce the proportional gain K after entering the mid-term control p The proportional gain K is increased again when the system enters the late stage of steady-state regulation. p Parameter values, combined with the integral link, work together to improve steady-state accuracy.

[0031] The regulation mechanism of the integral link directly affects the system's ability to eliminate steady-state errors. In this embodiment, the fuzzy controller dynamically modifies the integral gain K i In the fuzzy rule used, if the flow error signal E is NB and the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i are NB, NB, NM, NM, NS, ZO or ZO respectively; if the flow error signal E is NM, if the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i are NB, NB, NM, NS, NS, ZO or ZO respectively; if the flow error signal E is NS and the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i are NB, NB, NS, NS, NS, PS or PS respectively; if the flow error signal E is ZO, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i are NB, NM, NS, ZO, ZO, PM or PS respectively; if the flow error signal E is PS, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K iare NM, NM, NS, PS, ZO, PM or PM respectively; if the flow error signal E is PM, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i are ZO, NS, ZO, PS, PS, PM or PB respectively; if the flow error signal E is PB, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the integral gain K i They are ZO, ZO, PS, PM, PS, PS or PB, as shown in Table 2.

[0032] Table 2: Dynamic correction integral gain K i Fuzzy rule table used

[0033] See Table 2, in this embodiment, the dynamic correction integral gain K i Time-varying integral strategy realizes dynamic optimization: weak integral action is applied in the initial stage of control, that is, a preset lower integral gain K is adopted i To suppress the integral strength to avoid the risk of initial overshoot; after transitioning to the mid-term of system dynamic adjustment, gradually increase the integral gain K i To the specified range to balance the error correction demand and phase margin maintenance; when entering the late stage of steady-state tracking, the integral action strength is strengthened, that is, the integral gain K is continued to increase i In order to give full play to its cumulative error elimination characteristics to improve control accuracy.

[0034] The dynamic compensation characteristics of the differential link directly affect the transient response quality of the system. The fuzzy controller of this embodiment dynamically modifies the differential gain K d In the fuzzy rule used, if the flow error signal E is NB and the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d are PS, NS, NB, NB, NB, NM or PS respectively; if the flow error signal E is NM, if the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d are PS, NS, NB, NM, NM, NS or ZO respectively; if the flow error signal E is NS, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d are ZO, NS, NM, NM, NM, NS or ZO respectively; if the flow error signal E is ZO, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K dare ZO, ZO, NM, NM, NS, NS or ZO respectively; if the flow error signal E is PS, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d are PB, ZO, NS, NS, NS, NS or ZO respectively; if the flow error signal E is PM, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d are PB, ZO, ZO, ZO, NS, PS or PB respectively; if the flow error signal E is PB, the flow error change rate EC is NB, NM, NS, ZO, PS, PM or PB, the differential gain K d They are PB, PM, ZO, PS, PS, PS or PB, as shown in Table 3.

[0035] Table 3: Dynamic correction differential gain K d Fuzzy rule table used

[0036] See Table 3, in this embodiment, the dynamic correction differential gain K d Dynamic optimization is achieved by using time-varying differential gain: a strong differential effect is configured in the initial control stage, that is, a preset higher differential gain K is used. d In order to effectively suppress overshoot and enhance the response speed by utilizing its advanced compensation effect; moderately attenuate the differential gain when entering the mid-term regulation, that is, reduce the differential gain K d To balance the contradiction between dynamic correction requirements and noise sensitivity; when approaching the steady state stage, increase the differential strength again, that is, increase the differential gain K again d To form a secondary damping enhancement mechanism to improve anti-interference ability.

[0037] In Tables 1 to 3, NB, NM, NS, ZO, PS, PM, and PB are fuzzy linguistic variables. NB stands for "negative large," NM stands for "negative medium," NS stands for "negative small," ZO stands for "zero," PS stands for "positive small," PM stands for "positive medium," and PB stands for "positive large." It should be noted that the fuzzy controller maps the flow error signal E and the error change rate EC into fuzzy linguistic variables NB, NM, NS, ZO, PS, PM, and PB, and the proportional gain K p , integral gain K i and differential gain K d The mapping of the fuzzy linguistic variables NB, NM, NS, ZO, PS, PM, and PB of the three parameters to corresponding actual values ​​is an existing well-known method of the fuzzy controller, so its implementation details are not described in detail here.

[0038] According to the valve port flow equation Q= The hydraulic system is inherently nonlinear. The hydraulic station system of the machine tool has nonlinear friction and valve core hysteresis. The third-order state observer has more degrees of freedom and can be changed according to the actual situation. , , , , meeting the control requirements. In this embodiment, the function expression of the third-order state observer is: , , , , , , , , , in, ~ are the first, second, third and fourth control state variables of the hydraulic station, is the flow rate of the hydraulic station, is the internal pipeline pressure of the hydraulic station, is the pressure change in the internal pipeline of the hydraulic station, is the total disturbance, The relative control voltage of the hydraulic station flow The partial derivative of is the flow gain of the hydraulic pump 802, is the inlet and outlet pressure difference of the hydraulic pump 802, ~ for ~ The derivative of is the flow change of the hydraulic station, To control the voltage variation, is the change of flow disturbance, is the effective bulk modulus of the oil, is the effective volume of the control chamber of the hydraulic pump 802, is the load flow, is the pressure estimation error, Estimated flow rate The first derivative of Estimated pressure value The first derivative of is the estimated value of the pressure change rate The first derivative of is the disturbance estimate The first derivative of ~ is an intermediate variable, is the bandwidth of the third-order state observer. Since the hydraulic oil in the machine tool hydraulic station will increase the temperature during the flow process, the third-order observation adds a compensation term, and the observer introduces a total disturbance The core advantage of third-order state observers in hydraulic control lies in compensating for system nonlinearities and disturbances through algorithms, reducing reliance on high-cost hardware such as ultra-high-precision sensors, and improving the reliability and miniaturization of hydraulic station systems.

[0039] In this embodiment, the flow rate estimation value z1 is used to modify the integral gain K of the PID controller. i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d Includes: If the flow estimate z1 increases, reduce the integral gain K i To improve steady-state accuracy, if the flow estimate z1 decreases, increase the integral gain K i Otherwise, reduce the integral gain K i To improve stability; if the pressure estimate z2 increases, reduce the proportional gain K p Otherwise, increase the proportional gain K p To avoid overshoot; if the pressure change rate estimate z3 exceeds the preset threshold, increase the differential gain K d Otherwise, reduce the differential gain K d To suppress oscillation. In this embodiment, the proportional gain K of the PID controller p Between 0.01-0.5, integral gain K i Between 0.05-1s, the differential gain K d Between 0.1-0.5s.

[0040] The control method of the hydraulic station of the CNC lathe in this embodiment is to design a third-order state observer by combining fuzzy feedforward PID control, and obtain the flow estimation value of the hydraulic station through the observer. , pressure estimate , estimated pressure change rate and the perturbation estimate , use the estimated flow value z1 to modify the integral gain K of the PID controller i , use the pressure estimate z2 to modify the proportional gain K of the PID controller pThe design uses PID to control the pressure and flow of the hydraulic station, which can effectively suppress disturbances and quickly respond to changes in set values, and complete closed-loop control in the controller. The dynamic control algorithm in this embodiment adopts an adaptive fuzzy PID control strategy, which estimates the change in load inertia in real time through a third-order state observer. Combined with a feedforward compensation algorithm to eliminate the steady-state error caused by the valve port pressure difference, it can achieve high positioning accuracy and extremely stable flow control. It is particularly suitable for industrial scenarios such as ultra-precision lathes, aerospace actuators, and precision injection molding machines that require precise coordinated control of multiple physical quantities. Experimental verification has shown that the system's overall energy efficiency has increased by 82%, the force control accuracy is ±0.5% FS, and the maintenance cycle is extended by 4,000 working hours compared to traditional hydraulic systems.

[0041] In addition, this embodiment also provides a control system for a hydraulic station for a CNC lathe, comprising a microprocessor and a memory connected to each other, wherein the microprocessor is programmed or configured to execute a control method for a hydraulic station for a CNC lathe. This embodiment also provides a computer-readable storage medium storing a computer program or instructions programmed or configured to execute the control method for a hydraulic station for a CNC lathe via a processor. This embodiment also provides a computer program product comprising a computer program or instructions programmed or configured to execute the control method for a hydraulic station for a CNC lathe via a processor.

[0042] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A hydraulic station for a CNC lathe, characterized in that: The invention comprises an oil tank (9), a drive unit (8), a diaphragm accumulator (7), a filter (6), a high-pressure pipe (5) and an oil separator (4); the drive unit (8) comprises a servo motor (800), a motor fixing block (801), a hydraulic pump (802) and a pressure sensor (803); the output shaft of the servo motor (800) is connected to the hydraulic pump (802) via a coupling; the pressure sensor (803) is arranged on the output pipeline of the hydraulic pump (802); a flow meter (10) is provided on the output pipeline of the hydraulic pump (802); the oil inlet of the hydraulic pump (802) is connected to the oil tank (9); the output pipeline of the hydraulic pump (802), the diaphragm accumulator (7), the filter (6), the high-pressure pipe (5) and the oil separator (4) are connected in sequence to output hydraulic oil through the oil separator (4).

2. The hydraulic station for a CNC lathe according to claim 1, characterized in that: The oil tank (9) is in a cubic shape. Fixed plates (1) are welded on both sides and the rear of the oil tank (9) for being mounted on a CNC lathe via threads. A platform side panel (3) is provided on the outer side of the side wall of the oil tank (9). A pressure level gauge (2), an observation port (12), and a refueling port (13) are installed on the platform side panel (3). The flow meter (10) is mounted and fixed on the top of the oil tank (9). A thermometer (11) for detecting the temperature of the hydraulic oil is also mounted and fixed on the top of the oil tank (9).

3. A control method for a hydraulic station for a CNC lathe according to claim 1 or 2, characterized in that: include: S1, the flow signal detected by the flow meter (10) is used to obtain a feedforward signal by a feedforward controller ; S2, calculate the flow error signal E and error change rate EC, according to the flow error signal E and error change rate EC, use the fuzzy controller to dynamically correct the control parameters of the PID controller, and obtain the proportional gain K after the first correction p , integral gain K i and differential gain K d ; S3, through the third-order state observer, respectively observes the flow estimation value z1, pressure estimation value z2 and pressure change rate estimation value z3, and uses the flow estimation value z1 to correct the integral gain K of the PID controller i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d , get the second corrected proportional gain K p , integral gain K i and differential gain K d ; S4, through the PID controller based on the proportional gain K after the second correction p , integral gain K i and differential gain K d The error signal E of the input flow rate is used to obtain the corresponding reference signal, and the reference signal and the feedforward signal are combined The control voltage u of the hydraulic pump (802) is obtained by summing up to control the working state of the hydraulic pump (802).

4. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: The function expression of the feedforward controller is: ， ， in, is the output of the feedforward controller at time t, is the input of the feedforward controller at time t, is the feedforward transfer function of the feedforward controller, is the transfer function of the feedforward controller.

5. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: When the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the control process of the CNC lathe machining is divided into three stages: the initial control stage, the mid-control stage and the late steady-state adjustment stage. The fuzzy controller dynamically modifies the proportional gain K p The fuzzy rules used include a preset higher proportional gain K in the initial stage of control. p To utilize its fast response characteristics to improve the system's dynamic tracking capability; reduce the proportional gain K after entering the mid-term control p By weakening the proportional action strength, overshoot can be suppressed while maintaining system response efficiency; After entering the late stage of steady-state regulation, increase the proportional gain K again p The steady-state accuracy can be improved by combining with the integral link.

6. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: When the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the fuzzy controller dynamically modifies the integral gain K i The fuzzy rules used include a preset lower integral gain K in the initial stage of control. i To suppress the integral strength to avoid the risk of initial overshoot; gradually increase the integral gain K after entering the mid-term control i To balance the error correction requirements and the phase margin until entering the middle stage of control; continue to increase the integral gain K after entering the late stage of steady-state regulation i In order to improve the control accuracy, its cumulative error elimination characteristics are utilized.

7. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: When the fuzzy controller is used to dynamically modify the control parameters of the PID controller, the fuzzy controller dynamically modifies the differential gain K d The fuzzy rules used include a preset higher differential gain K in the initial stage of control. d In order to utilize its advanced compensation effect to effectively suppress overshoot and enhance the rapid response; after entering the mid-term control, reduce the differential gain K d To balance the contradiction between dynamic correction requirements and noise sensitivity; after entering the late stage of steady-state regulation, increase the differential gain K again d To form a secondary damping enhancement mechanism to improve anti-interference ability.

8. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: The function expression of the third-order state observer is: ， ， ， ， ， ， ， ， ， in, ~ are the first, second, third and fourth control state variables of the hydraulic station, is the flow rate of the hydraulic station, is the internal pipeline pressure of the hydraulic station, is the pressure change in the internal pipeline of the hydraulic station, is the total disturbance, The relative control voltage of the hydraulic station flow The partial derivative of is the flow gain of the hydraulic pump (802), is the inlet and outlet pressure difference of the hydraulic pump (802), ~ for ~ The derivative of is the flow change of the hydraulic station, To control the voltage variation, is the change of flow disturbance, is the effective bulk modulus of the oil, is the effective volume of the control chamber of the hydraulic pump (802), is the load flow, is the pressure estimation error, Estimated flow rate The first derivative of Estimated pressure value The first derivative of is the estimated value of the pressure change rate The first derivative of is the disturbance estimate The first derivative of ~ is an intermediate variable, is the bandwidth of the third-order state observer.

9. The control method for a hydraulic station of a CNC lathe according to claim 3, characterized in that: The integral gain K of the PID controller is modified by using the estimated flow value z1. i , use the pressure estimate z2 to modify the proportional gain K of the PID controller p , use the estimated value of pressure change rate z3 to modify the differential gain K of the PID controller d Includes: If the flow estimate z1 increases, reduce the integral gain K i To improve steady-state accuracy, if the flow estimate z1 decreases, increase the integral gain K i Otherwise, reduce the integral gain K i To improve stability; if the pressure estimate z2 increases, reduce the proportional gain K p Otherwise, increase the proportional gain K p To avoid overshoot; if the pressure change rate estimate z3 exceeds the preset threshold, increase the differential gain K d Otherwise, reduce the differential gain K d To suppress vibration.

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