Hydraulic synchronous control system and control method based on traveling wave magnetic field composite driving

Abstract

The application relates to the technical field of electro-hydraulic integrated driving, and particularly relates to a hydraulic synchronous control system and a control method based on traveling wave magnetic field composite driving, which comprises a plurality of hydraulic cylinders, the hydraulic cylinder comprises a piston rod assembly and a cylinder barrel, the piston rod assembly comprises a metal push rod in an inner layer, a three-phase winding module arranged around the metal push rod in a middle layer and a lining barrel in an outer layer, each hydraulic cylinder is provided with a pressure sensor, a displacement sensor and a controller; the cylinder barrel serves as a secondary conductor, eddy current is generated through traveling wave magnetic field induction, and axial thrust is generated. When the load is empty, the controller switches the current direction to generate auxiliary oil suction thrust; when the load is loaded, the current parameters are dynamically adjusted according to the displacement, pressure and speed feedback, synchronous compensation and speed regulation are realized. The application has the characteristics of high thrust density of the hydraulic system and fast response characteristics of the linear motor, and is suitable for high-precision engineering machinery, aerospace hydraulic actuators.

Description

Technical Field

[0001] This invention relates to the technical field of electro-hydraulic integrated drive, and in particular to a hydraulic synchronous control system and control method based on traveling wave magnetic field composite drive. Background Technology

[0002] Hydraulic systems have long faced bottlenecks in multi-cylinder synchronous control, including low synchronization accuracy, sluggish dynamic response, and insufficient energy efficiency. Traditional solutions use mechanical coupling to force consistent displacement across multiple cylinders through rigid connections like gears and connecting rods. While simple in structure, mechanical clearances and elastic deformation lead to accumulated errors. Proportional valve control relies on high-precision valve regulation of flow distribution, but limited by hydraulic oil compressibility and valve core dynamics (response delay >50ms), it is prone to pressure oscillations due to oil elasticity during low-frequency load fluctuations, resulting in "virtual displacement." Furthermore, valve control systems require constant high pressure to overcome pipeline resistance; during no-load return strokes, approximately 65% ​​of the pump station's energy is consumed by valve throttling, highlighting energy efficiency issues. While direct linear motor drive offers high response and micron-level positioning accuracy, its thrust density is insufficient to match the load requirements of hydraulic cylinders, and the independent motor occupies additional space.

[0003] In recent years, hydraulic-electromagnetic hybrid drive technology has attempted to combine the advantages of both, but existing solutions have significant drawbacks: for example, in the case of external linear motor-assisted hydraulic cylinder solutions, the offset between the electromagnetic thrust axis and the hydraulic cylinder centerline causes additional bending moment, which exacerbates piston wear and reduces lifespan; in addition, insufficient speed regulation capability has become a common problem. Traditional hydraulic systems rely on valve-controlled throttling speed regulation, resulting in poor speed stability, while independent linear motors have an inherent contradiction between high speed and high thrust. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a hydraulic synchronous control system and control method based on traveling wave magnetic field composite drive, which can realize synchronous control of multiple hydraulic cylinders and continuous adjustment of movement speed.

[0005] On the one hand, the present invention provides a hydraulic synchronous control system based on traveling wave magnetic field composite drive, which adopts the following technical solution: A hydraulic synchronous control system based on traveling wave magnetic field composite drive includes multiple hydraulic cylinders. Each hydraulic cylinder includes a piston rod assembly and a cylinder barrel. The piston rod assembly includes an inner metal push rod, a middle three-phase winding module arranged around the metal push rod, and an outer bushing. Each hydraulic cylinder corresponds to a pressure sensor, a displacement sensor, and a controller. The pressure sensor is installed in the oil circuit of the hydraulic cylinder, and the displacement sensor is installed outside the hydraulic cylinder. Both the pressure sensor and the displacement sensor are communicatively connected to the controller. The controllers are communicatively connected to each other, and there is cross-coupling compensation between the hydraulic cylinders. The controller is communicatively connected to a time relay for calculating the displacement time of the metal push rod.

[0006] Optionally, the three-phase winding module includes coils and silicon steel sheets. The coils and silicon steel sheets wrapped with high-temperature resistant enameled wire form the windings, which are then sealed with epoxy resin.

[0007] Optionally, the metal push rod is made of high-strength alloy steel, the liner is made of aluminum alloy, and the cylinder is made of high-permeability low-carbon steel.

[0008] On the other hand, the present invention also discloses a control method for a hydraulic synchronous control system based on traveling wave magnetic field composite drive, comprising the following steps: During the initialization phase, the system performs a self-test, the controller is powered on, and the displacement sensor, pressure sensor, and coil impedance values ​​of each hydraulic cylinder are read sequentially. The hydraulic pump starts, and simultaneously, the controller injects preheating current into the coil to activate the magnetic field and detect the cylinder eddy current response. One hydraulic cylinder is designated as the active hydraulic cylinder, and the others are designated as driven hydraulic cylinders. The target speed of the active hydraulic cylinder is set, and the controller of the driven hydraulic cylinders receives the initial PID parameters from the displacement signal of the active hydraulic cylinder controller.

[0009] During the load lifting phase, disturbance detection and compensation are performed. If the driven hydraulic cylinder lags behind in displacement due to off-center load during the lifting process, the controller calculates the displacement error ΔL in real time, triggers fuzzy PID adjustment, and compensates the thrust to quickly achieve error convergence.

[0010] Precision positioning stage: As the target approaches, S-curve planning is initiated, the traveling wave magnetic field weakens and reverses, and the piston rod smoothly decelerates to avoid mechanical impact. After reaching the target position, the excitation current is reduced, and combined with the dynamic pressure maintenance of the hydraulic lock-up valve, stable positioning is ensured.

[0011] During the no-load return phase, reverse thrust is generated by reversing the current phase. The rodless chamber returns under the drive of the hydraulic pump. At the same time, the bypass is connected to the oil tank, and oil is drawn in with the help of reverse electromagnetic force to compensate for the oil supply demand of the hydraulic cylinder, increase the return speed, save energy and improve efficiency.

[0012] Compared with the prior art, the present invention has the following technical effects: By integrating the primary coil of a three-phase linear motor into the piston rod of a hydraulic cylinder, and combining hydraulic thrust with a dynamic coordination mechanism of electromagnetic induction force, multi-cylinder synchronous control and continuous speed adjustment are achieved. Under no-load conditions, the controller switches the current direction to generate auxiliary oil suction thrust; under load, it dynamically adjusts the current parameters based on displacement, pressure, and speed feedback to achieve synchronous compensation and speed regulation. This invention combines the high thrust density of a hydraulic system with the rapid response characteristics of a linear motor, making it suitable for high-precision engineering machinery and aerospace hydraulic actuators. Attached Figure Description

[0013] Figure 1This is a schematic diagram of the piston rod assembly of the hydraulic cylinder in this invention; Figure 2 This is a schematic diagram of the hydraulic cylinder in this invention; Figure 3 This is a schematic diagram of the synchronous hydraulic principle of multiple hydraulic cylinders in this invention; Figure 4 This is a schematic diagram of the control flow in this invention.

[0014] Explanation of reference numerals in the attached drawings: 1. Hydraulic cylinder; 2. Piston rod assembly; 21. Metal push rod; 22. Three-phase winding module; 221. Coil; 222. Silicon steel sheet; 23. Liner; 3. Cylinder barrel; 31. Cylinder head flange; 4. Diverter valve; 5. Pressure reducing valve; 6. Bypass. Detailed Implementation

[0015] The following is in conjunction with the appendix Figure 1 - Appendix Figure 4 The present invention will be described in further detail below.

[0016] Reference Figures 1-4 This invention discloses a hydraulic synchronous control system based on traveling wave magnetic field composite drive, comprising a hydraulic cylinder 1, a displacement sensor, a pressure sensor, and a controller, wherein the controller is a PID controller. The hydraulic cylinder 1 includes a piston rod assembly 2 and a cylinder barrel 3. The piston rod assembly 2 includes an inner metal push rod 21, a three-phase winding module 22 arranged around the metal push rod 21 in the middle layer, and an outer aluminum alloy bushing 23. The three-phase winding module 22 includes coils 221 and silicon steel sheets 222. Three sets of three-phase winding modules (U / V / W phase difference 120°) are equidistantly distributed along the axial direction in the middle layer. Each set of coils 221 has 50 turns. The coils 221 and the silicon steel sheets 222 wrapped with high-temperature resistant enameled wire form a winding, which is then sealed with epoxy resin. The permeability of the bushing 23 is approximately 1. The cylinder barrel 3, as a secondary conductor, is made of high-permeability low-carbon steel, and its inner wall is plated with hard chrome to reduce the coefficient of friction. Figure 2 In the diagram, position A is the oil port for the rod chamber, position B is the oil port for the rodless chamber, and position C is the coil wiring inlet.

[0017] The metal push rod 21 is made of high-strength alloy steel and bears the main hydraulic thrust. A three-phase winding module 22 is arranged circumferentially in the middle layer, generating a traveling wave magnetic field by injecting a sinusoidal current with adjustable amplitude and frequency. The outer layer is wrapped with an aluminum alloy liner 23, which provides insulation protection and avoids interference with the magnetic field distribution. The cylinder 3 generates axial electromagnetic thrust by inducing eddy currents through the traveling wave magnetic field. The direction of the thrust is determined by the current phase, exhibiting high-speed response characteristics compared to traditional hydraulic systems.

[0018] The traveling wave magnetic field is excited by three-phase alternating current. After penetrating the liner 23, it forms an induced eddy current on the surface of the cylinder 3. According to Fleming's left-hand law, it generates an axial electromagnetic thrust. The thrust direction is controlled by the current phase, and it also has the millisecond-level response characteristics of a linear motor.

[0019] Each hydraulic cylinder 1 corresponds to a pressure sensor, a displacement sensor, and a controller. The pressure sensor is installed in the hydraulic circuit of hydraulic cylinder 1 to monitor pressure fluctuations in the hydraulic circuit. The displacement sensor is installed on the outside of hydraulic cylinder 1 to detect the displacement of the piston rod and determine whether the piston rods of multiple hydraulic cylinders 1 are synchronized. Both the pressure sensor and the displacement sensor are communicatively connected to the controller. The controllers are also communicatively connected. A timer is included in the controller communication connection to calculate the piston rod displacement time. The extension speed of the piston rod is obtained by calculating the displacement over time.

[0020] A method for synchronous control of multiple hydraulic cylinders: To achieve high-precision synchronization of multiple cylinders, the system adopts a hierarchical collaborative control architecture.

[0021] (1) Master-Slave Follower Control: One hydraulic cylinder 1 is designated as the active hydraulic cylinder, and the remaining hydraulic cylinders 1 are the driven hydraulic cylinders. The displacement signal of the active hydraulic cylinder is broadcast to the controllers of each driven hydraulic cylinder via the CAN bus. The controllers of the driven hydraulic cylinders calculate the displacement error ΔL in real time. Before hydraulic cylinder 1 moves, the displacement sensor can calibrate the position value. After it starts moving, the difference between the position value of the displacement sensor and the calibrated value is the distance traveled by this hydraulic cylinder 1. If there are four hydraulic cylinders 1, we can select any one hydraulic cylinder 1 as a reference. If it moves 1000, then the other hydraulic cylinders 1 may move 1000.05 or 999.2, etc. The difference between these values ​​and 1000, 0.05 and -0.8, are the displacement errors.

[0022] The compensation current is generated according to the aforementioned formula, where Icomp is the compensation current, Kp is the proportional gain, Ki is the integral gain, and Kd is the micro powder gain.

[0023] (2) Cross-coupling compensation among multiple hydraulic cylinders 1. Cross-coupling compensation is an advanced strategy for the synchronous control of multiple hydraulic cylinders in a hydraulic system. The traditional control method is to give each cylinder an independent controller (such as a PID controller), and each controller only focuses on the deviation between the actual position and the commanded position of its own cylinder (single-axis error). This method is effective for controlling a single cylinder, but it cannot actively coordinate the synchronization relationship between multiple cylinders. Compared with the traditional control method, cross-coupling compensation not only controls the position error of each hydraulic cylinder 1, but also actively controls the relative position error (displacement difference) between adjacent cylinders (or all related cylinders).

[0024] When multiple hydraulic cylinders 1 work together, a displacement coupling matrix is ​​constructed between the hydraulic cylinders 1, and compensation weights are dynamically allocated. For example, when the displacement difference between two adjacent hydraulic cylinders 1 exceeds a threshold, cross-feedback adjustment is initiated to suppress the chain propagation of errors.

[0025] (3) Pressure-displacement joint feedback: The pressure sensor monitors the pressure difference ΔP between the rod-side and rodless sides of each hydraulic cylinder 1 in real time, and constructs a state observer based on the displacement data to predict the trend of sudden load changes. When the rate of change of ΔP exceeds the set threshold, electromagnetic compensation is intervened in advance to suppress the synchronization error within ±0.1mm. The state observer mentioned in the hydraulic control system is a dynamic estimation algorithm based on mathematical models and real-time sensor data. Its core function is to infer the internal state or future trend of the system that cannot be directly measured.

[0026] Reference Figure 3 In the hydraulic schematic diagram, during the piston rod thrust state: the system, based on the synchronous circuit of the flow divider valve 4, controls the propagation speed of the traveling wave magnetic field by adjusting the excitation frequency of the coil 221; simultaneously, it adjusts the current magnitude to control the compensation or suppression of the electromagnetic force on the piston rod thrust, thereby achieving balanced distribution and speed regulation of the flow rate in the rodless chamber of each cylinder during thrust. During the return stroke: the return oil pressure is reduced by adjusting the pressure reducing valve 5, the reverse electromagnetic force compensates for the piston rod return force, and the bypass 6 assists in oil suction, accelerating the return stroke.

[0027] The system operates in two modes: hydraulically driven and electromagnetically driven. Under heavy loads, electromagnetic thrust acts as a compensation to suppress synchronization deviations caused by sudden load changes. Normal working loads are continuously varying, and sudden changes may occur due to load shifts, sudden unload vibrations, etc. Under light loads, electromagnetic thrust provides the primary driving force, while the hydraulic system only maintains basic oil pressure, which helps reduce pressure loss and energy consumption. Speed ​​control adjusts the amplitude and frequency of the current to change the propagation speed of the traveling wave magnetic field, achieving continuous adjustment of the piston rod speed of hydraulic cylinder 1, with accuracy several times greater than that of a transmission valve control system. Furthermore, during the no-load return phase, reverse thrust is generated by reversing the current phase. A one-way valve bypasses the oil tank, using reverse electromagnetic force to assist in oil suction, reducing the hydraulic pump's oil supply requirements and improving energy efficiency and return speed.

[0028] The hydraulic synchronization control system of this invention uses cylinder 3 as its secondary conductor and employs an electromagnetic drive method without permanent magnets, eliminating the risk of permanent magnet demagnetization at high temperatures. A closed-loop dynamic compensation mechanism detects displacement-velocity changes and uses a fuzzy PID algorithm to optimize synchronization control accuracy. Closed-loop refers to a system containing a feedback loop; the PID controller continuously receives actual displacement and velocity measurements, compares them with the desired target value (command), and calculates the error. A displacement sensor measures the piston rod displacement, a timer calculates the time, and the displacement is used to obtain the velocity from the time.

[0029] Detecting displacement-velocity changes: The system monitors the actual position (displacement) and velocity changes of each actuator in real time. This is the core source of feedback signals.

[0030] Dynamic compensation mechanism: In real time, it responds to load changes by actively calculating and applying an additional correction (compensation) to the control output based on the detected displacement / velocity errors and their trends. This compensation is designed to counteract disturbances or differences that cause asynchrony.

[0031] The electromagnetic thrust generated by the traveling wave magnetic field dynamically compensates for or suppresses external disturbances, with a rapid response speed, improving synchronization and positioning accuracy. In the no-load phase, electromagnetic force assists in oil suction, replacing traditional valve-controlled oil replenishment methods to reduce energy loss and eliminate maintenance.

[0032] The present invention provides a control method for a hydraulic synchronous control system based on traveling wave magnetic field composite drive, which includes the following steps. Taking the synchronous lifting of four hydraulic cylinders 1 as an example, the system operation is divided into an initialization stage, a load lifting stage, a precision positioning stage, and a return stage.

[0033] During the initialization phase, the system performs a self-test, the controller is powered on, and the impedance values ​​of the displacement sensors, pressure sensors, and coil 221 of each hydraulic cylinder 1 are read sequentially. The hydraulic pump starts, and simultaneously the controller injects preheating current into coil 221 to activate the magnetic field and detect the eddy current response of cylinder 3. One hydraulic cylinder 1 is designated as the active hydraulic cylinder 1, and the remaining hydraulic cylinders 1 are designated as driven hydraulic cylinders 1. The target speed of the active hydraulic cylinder 1 is set, and the controller of the driven hydraulic cylinder 1 receives the initial PID parameters from the displacement signal of the active hydraulic cylinder 1.

[0034] During the load lifting phase, disturbance detection and compensation are performed. If the driven hydraulic cylinder 1 lags behind in displacement due to off-center load during the lifting process, the controller calculates the displacement error ΔL in real time, triggers fuzzy PID adjustment, and compensates the thrust to quickly achieve error convergence.

[0035] Precision positioning stage: As the target approaches, S-curve planning is initiated, the traveling wave magnetic field weakens and reverses, and the piston rod smoothly decelerates to avoid mechanical impact. After reaching the target position, the excitation current is reduced, and combined with the dynamic pressure maintenance of the hydraulic lock-up valve, stable positioning is ensured.

[0036] During the no-load return phase, reverse thrust is generated by reversing the current phase. The rodless chamber returns under the drive of the hydraulic pump. At the same time, the bypass is connected to the oil tank, and oil is drawn in with the help of reverse electromagnetic force to compensate for the oil supply demand of hydraulic cylinder 1, increase the return speed, save energy and improve efficiency.

[0037] This invention overcomes the technical bottlenecks of low synchronization accuracy, slow response, and poor energy efficiency in traditional hydraulic systems through triple innovation in structure, control, and energy efficiency. Structurally, it pioneers an inductive interactive design between the piston rod embedded with a three-phase coil 221 and the cylinder 3, eliminating permanent magnets and utilizing the cylinder 3's own eddy currents to generate thrust, reducing manufacturing costs and ensuring resistance to high temperatures and impact loads. It also solves the industry problems of permanent magnet demagnetization and external motor shaft misalignment. In terms of control strategy, a fuzzy PID collaborative architecture is proposed, achieving synchronization accuracy at the ±0.1mm level with a speed fluctuation rate of <1%. Regarding energy efficiency optimization, electromagnetic force-assisted oil suction during the no-load phase reduces energy consumption.

[0038] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A control method for a hydraulic synchronous control system based on traveling wave magnetic field composite drive, characterized in that: Includes the following steps: During the initialization phase, the system performs a self-test, the controller is powered on, and reads the displacement sensor, pressure sensor, and coil impedance values ​​of each hydraulic cylinder in sequence. The hydraulic pump starts, and the controller injects preheating current into the coil to activate the magnetic field and detect the cylinder eddy current response. One hydraulic cylinder is designated as the active hydraulic cylinder, and the remaining hydraulic cylinders are designated as driven hydraulic cylinders. The target speed of the active hydraulic cylinder is set, and the controller of the driven hydraulic cylinder receives the displacement signal and initial PID parameters from the controller of the active hydraulic cylinder. During the load lifting phase, disturbance detection and compensation are performed. If the driven hydraulic cylinder lags behind in displacement due to off-center load during the lifting process, the controller calculates the displacement error ΔL in real time, triggers fuzzy PID adjustment, and compensates the thrust to quickly achieve error convergence. Precision positioning stage: When approaching the target, the S-curve planning is initiated, the traveling wave magnetic field is weakened and reversed, and the piston rod is smoothly decelerated to avoid mechanical impact. After reaching the target position, the excitation current is reduced, and combined with the dynamic pressure maintenance of the hydraulic lock-up valve, the positioning is stable. During the no-load return phase, reverse thrust is generated by reversing the current phase. The rodless chamber returns under the drive of the hydraulic pump. At the same time, the bypass is connected to the oil tank, and oil is drawn in with the help of reverse electromagnetic force to compensate for the oil supply demand of the hydraulic cylinder, increase the return speed, save energy and improve efficiency. The hydraulic synchronization control system includes multiple hydraulic cylinders. Each hydraulic cylinder includes a piston rod assembly and a cylinder barrel. The piston rod assembly includes an inner metal push rod, a middle three-phase winding module arranged around the metal push rod, and an outer bushing. Each hydraulic cylinder corresponds to a pressure sensor, a displacement sensor, and a controller. The pressure sensor is installed in the oil circuit of the hydraulic cylinder, and the displacement sensor is installed outside the hydraulic cylinder. Both the pressure sensor and the displacement sensor are connected to the controller. The controllers are connected to each other. There is cross-coupling compensation between the hydraulic cylinders. The controller is connected to a time relay that calculates the displacement time of the metal push rod. The three-phase winding module includes coils and silicon steel sheets. The coils and silicon steel sheets wrapped with high-temperature resistant enameled wire form the windings, which are then sealed with epoxy resin. The metal push rod is made of high-strength alloy steel, the liner is made of aluminum alloy, and the cylinder is made of high-permeability low-carbon steel.

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