Hydraulic synchronous control system and control method based on traveling wave and magnetic field combined drive

Abstract

The invention relates to the technical field of electro-hydraulic integrated driving, in particular to a hydraulic synchronous control system and method based on traveling wave and magnetic field composite driving, the system comprises a plurality of hydraulic cylinders, and each hydraulic cylinder comprises a piston rod assembly and a cylinder barrel; the piston rod assembly comprises a metal push rod on the inner layer, a three-phase winding module arranged around the metal push rod on the middle layer and a lining barrel on the outer layer. Each hydraulic cylinder corresponds to one pressure sensor, one displacement sensor and one controller. The cylinder barrel serves as a secondary conductor, eddy current is generated through traveling wave magnetic field induction, and axial thrust is generated. In a no-load state, the controller switches the current direction to generate auxiliary oil absorption thrust; during loading, current parameters are dynamically adjusted according to displacement, pressure and speed feedback, and synchronous compensation and speed regulation are achieved. The linear motor has the characteristics of high thrust density of a hydraulic system and quick response of the linear motor, and is suitable for high-precision engineering machinery and aerospace hydraulic actuating mechanisms.

Description

Technical Field

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

[0002] Hydraulic systems in the field of multi-cylinder synchronous control have long faced bottlenecks such as low synchronization accuracy, delayed dynamic response, and insufficient energy efficiency. Traditional solutions use mechanical coupling synchronization to force the displacement of multiple cylinders to coincide through rigid connections such as gears and connecting rods. While this approach is simple in structure, mechanical backlash and elastic deformation lead to cumulative errors. Proportional valve control relies on high-precision valves to adjust flow distribution, but this is limited by the compressibility of the hydraulic oil and the dynamic characteristics of the valve core (response delay >50ms). Low-frequency load fluctuations are prone to pressure oscillations due to oil elasticity, resulting in "virtual displacement." Furthermore, the valve control system must maintain a constant high pressure to overcome pipeline resistance. During the no-load return stroke, approximately 65% ​​of the pump station's energy is consumed by valve throttling, leading to significant energy efficiency issues. While linear motor direct drives offer high response and micron-level positioning accuracy, their thrust density is difficult to match the load requirements of the hydraulic cylinders, and the independent motors occupy additional space.

[0003] In recent years, hydraulic-electromagnetic hybrid drive technology has attempted to combine the advantages of both, but existing solutions have significant defects: for example, the external linear motor assisted hydraulic cylinder solution, due to the offset between the electromagnetic thrust axis and the center line of the hydraulic cylinder, causes additional bending moment, which aggravates the eccentric wear of the piston and reduces its service life; in addition, insufficient speed regulation capability has become a common problem. Traditional hydraulic systems rely on valve-controlled throttling speed regulation, and have poor speed stability, while independent linear motors have a natural contradiction between high speed and large thrust. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned 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 solutions: A hydraulic synchronous control system based on traveling wave magnetic field composite drive includes multiple hydraulic cylinders, the hydraulic cylinders include piston rod assemblies and cylinder barrels, 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 liner. 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. The pressure sensor and the displacement sensor are both communicatively connected to the controller, and the controllers are communicatively connected to each other. The hydraulic cylinders are cross-coupled and compensated. 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 a coil and a silicon steel sheet, the coil and the silicon steel sheet wrapped with a high-temperature resistant enameled wire constitute a winding, and are 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-magnetic-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 a 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 reads the displacement sensors, pressure sensors, and coil impedance values ​​of each hydraulic cylinder. The hydraulic pump starts, and the controller simultaneously injects a preheating current into the coil, activating the magnetic field and detecting the eddy current response of the cylinder barrel. One of the hydraulic cylinders is designated as the master cylinder, while the remaining cylinders are slave cylinders. A target speed is set for the master cylinder, and the slave cylinder controllers receive the initial PID parameters from the displacement signal of the master cylinder controller.

[0009] During the load lifting phase, disturbance detection and compensation are performed. During the lifting process, if the slave hydraulic cylinder lags behind due to eccentric load, 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: When approaching the target, S-curve planning is initiated, the traveling magnetic field weakens and reverses, allowing the piston rod to smoothly decelerate and avoid mechanical shock. After reaching the target position, the excitation current is reduced, and the hydraulic locking valve is used to dynamically maintain pressure to ensure stable positioning.

[0011] During the no-load return stage, reverse thrust is generated by reversing the current phase, and the rodless cavity returns under the drive of the hydraulic pump. At the same time, the oil tank is bypassed and the reverse electromagnetic force is used to assist in oil suction, 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 hydraulic cylinder piston rod and combining the dynamic coordination of hydraulic thrust and electromagnetic induction force, this system achieves synchronous multi-cylinder control and continuous speed regulation. When unloaded, the controller switches the current direction to generate auxiliary oil suction thrust. Under load, the current parameters are dynamically adjusted 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 fast response characteristics of a linear motor, making it suitable for high-precision hydraulic actuators in engineering machinery and aerospace applications. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Explanation of the accompanying symbols: 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 DESCRIPTION

[0015] The following is combined with Figure 1 -Attached Figure 4 The present invention is described in further detail.

[0016] Reference Figure 1-Figure 4 The present invention discloses a hydraulic synchronous control system based on traveling-wave magnetic field hybrid drive, including a hydraulic cylinder 1, a displacement sensor, a pressure sensor, and a controller, which is a PID controller. The hydraulic cylinder 1 comprises a piston rod assembly 2 and a cylinder barrel 3. The piston rod assembly 2 includes an inner metal push rod 21, a middle three-phase winding module 22 surrounding the metal push rod 21, and an outer aluminum alloy liner 23. The three-phase winding module 22 comprises coils 221 and silicon steel sheets 222. The middle annular coils consist of three groups of three-phase winding modules equidistantly distributed along the axial direction (with a 120° phase shift between the U / V / W phases). Each coil 221 has 50 turns. The coils 221 and the silicon steel sheets 222, which are wrapped with high-temperature enameled wire, form a winding and are sealed with epoxy resin. The magnetic permeability of the liner 23 is approximately 1. The cylinder barrel 3, serving as the secondary conductor, is made of high-permeability low-carbon steel, with a hard chrome plating on the inner wall to reduce 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 entrance.

[0017] The metal push rod 21, made of high-strength alloy steel, carries the primary 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. An aluminum alloy liner 23, wrapped around the outer layer, provides insulation protection while preventing interference with the magnetic field distribution. The cylinder 3 generates axial electromagnetic thrust through eddy currents induced by the traveling-wave magnetic field. The thrust direction is determined by the current phase, resulting in a high-speed response compared to traditional hydraulic systems.

[0018] The traveling wave magnetic field is excited by three-phase alternating current, and after penetrating the liner 23, it forms induced eddy currents on the surface of the cylinder 3, generating axial electromagnetic thrust according to Fleming's left-hand law. 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, displacement sensor, and controller. The pressure sensor is installed in the hydraulic cylinder 1 oil circuit to monitor pressure fluctuations in the hydraulic cylinder 1 oil circuit. The displacement sensor is installed on the outside of the 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 displacement sensor are connected to the controller. The controllers are connected to each other. The controllers are also connected to a timer that calculates the time it takes for the piston rod to move. The displacement divided by the time gives the piston rod extension speed.

[0020] Synchronous control method for multiple hydraulic cylinders 1,To achieve high-precision synchronization of multiple cylinders, the system adopts a hierarchical collaborative control architecture.

[0021] (1) Master-slave control: Designate one hydraulic cylinder 1 as the active hydraulic cylinder and the other hydraulic cylinders 1 as slave hydraulic cylinders. The displacement signal of the active hydraulic cylinder is broadcast to the controllers of each slave hydraulic cylinder via the CAN bus, and the controllers of the slave hydraulic cylinders calculate the displacement error ΔL in real time. Before the hydraulic cylinder 1 moves, the displacement sensor can calibrate the position value. When the movement starts, 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 select any hydraulic cylinder 1 as a reference. If it moves 1000, then the other hydraulic cylinders 1 may move 1000.05 or 999.2, etc., then the difference between these values ​​​​to 1000, 0.05 and -0.8 are the displacement errors.

[0022] , generate compensation current according to the above formula, Icomp is the compensation current, Kp is the proportional gain, Ki is the integral gain, and Kd is the powder gain.

[0023] (2) Cross-coupling compensation between multiple hydraulic cylinders 1. Cross-coupling compensation is an advanced strategy for 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 command 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 can not only control the position error of each hydraulic cylinder 1 itself, but also actively control 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 assigned. For example, when the displacement difference between two adjacent hydraulic cylinders 1 exceeds a threshold, cross-feedback regulation is activated to suppress the chain diffusion of errors.

[0025] (3) Combined pressure-displacement feedback: A pressure sensor monitors the pressure difference ΔP between the rod chamber and the rodless chamber in each hydraulic cylinder 1 in real time. Combined with the displacement data, a state observer is constructed to predict the trend of sudden load changes. When the rate of change of ΔP exceeds a set threshold, electromagnetic compensation is initiated in advance to suppress the synchronization error to 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 principle diagram, the piston rod advance state: The system, based on the synchronous circuit of diverter valve 4, controls the propagation speed of the traveling wave magnetic field by adjusting the excitation frequency of the current in coil 221. Simultaneously, the current magnitude is adjusted to control the electromagnetic force's compensation or suppression of the piston rod thrust, thereby achieving balanced distribution of flow in the rodless chamber and speed control among the various cylinders. In the return state: Reducing valve 5 regulates the return oil pressure, and the reverse electromagnetic force compensates for the piston rod's return force. Bypass 6 assists in oil suction, accelerating the return stroke.

[0027] The system's operating modes are hydraulically dominated and electromagnetically dominated. When working under heavy loads, electromagnetic thrust acts as a compensation to suppress synchronization deviations caused by sudden load changes. Generally, the working load changes continuously, and sudden changes may occur in: load offset, sudden vibration due to load loss, etc. When working under light loads, electromagnetic thrust provides the main driving force, and the hydraulic system only maintains the basic oil pressure, which helps reduce pressure loss and energy consumption. Speed ​​control achieves continuous adjustment of the piston rod speed of hydraulic cylinder 1 by adjusting the amplitude and frequency of the current, thereby changing the propagation speed of the traveling wave magnetic field, and improving the accuracy of the transmission valve control system by several times. In addition, during the no-load return phase, reverse thrust is generated by reversing the current phase. The one-way valve is connected to the oil tank on the side to assist in oil suction with the help of reverse electromagnetic force, reducing the oil supply demand of the hydraulic pump and improving energy efficiency and return speed.

[0028] The hydraulic synchronous control system of the present invention uses the cylinder barrel (3) as its own secondary conductor and employs an electromagnetic drive method without permanent magnets, eliminating the risk of permanent magnet demagnetization due to high temperatures. A closed-loop dynamic compensation mechanism detects displacement-velocity changes and employs a fuzzy PID algorithm to optimize synchronous control accuracy. A closed-loop system includes a feedback loop. The PID controller continuously receives actual displacement and velocity measurements, compares them with the desired target values ​​(commands), and calculates the error. A displacement sensor measures piston rod displacement, a timer calculates time, and velocity is calculated by dividing displacement by time.

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

[0030] Dynamic compensation mechanism: In real-time response to load changes, it proactively calculates and applies an additional correction (compensation) to the control output based on the detected displacement / velocity errors and their changing trends. This compensation is intended to offset disturbances or differences that cause asynchrony.

[0031] The electromagnetic thrust generated by the traveling wave magnetic field dynamically compensates for or suppresses external disturbances, providing rapid response and improved synchronization and positioning accuracy. During the no-load phase, electromagnetic force assists in oil suction, replacing traditional valve-controlled oil replenishment methods to reduce energy consumption 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 precise positioning stage and a return stage.

[0033] During the initialization phase, a system self-test is performed. The controller is powered on and reads the impedance values ​​of each hydraulic cylinder 1 displacement sensor, pressure sensor, and coil 221. The hydraulic pump is started, and the controller simultaneously injects a preheating current into coil 221, activating the magnetic field and detecting the eddy current response of cylinder barrel 3. One hydraulic cylinder 1 is designated as the master hydraulic cylinder 1, and the remaining hydraulic cylinders 1 are designated as slave hydraulic cylinders 1. The target speed of the master hydraulic cylinder 1 is set, and the slave hydraulic cylinder 1 controller receives the initial PID parameters from the master hydraulic cylinder 1 displacement signal.

[0034] During the load lifting phase, disturbance detection and compensation are performed. During the lifting process, if the slave hydraulic cylinder 1 lags behind due to eccentric load, 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: When approaching the target, S-curve planning is initiated, the traveling magnetic field weakens and reverses, allowing the piston rod to smoothly decelerate and avoid mechanical shock. After reaching the target position, the excitation current is reduced, and the hydraulic locking valve is used to dynamically maintain pressure to ensure stable positioning.

[0036] During the no-load return stage, reverse thrust is generated by reversing the current phase, and the rodless cavity returns under the drive of the hydraulic pump. At the same time, the oil tank is bypassed and the reverse electromagnetic force is used to assist in oil suction, 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 innovations in structure, control, and energy efficiency. Structurally, it pioneers an inductively interactive design between the piston rod's embedded three-phase coil 221 and the cylinder barrel 3. This eliminates permanent magnets and utilizes the cylinder barrel 3's own eddy currents to generate thrust, reducing manufacturing costs. It also withstands high temperatures and impact loads, resolving the industry challenges of permanent magnet demagnetization and external motor axis offset. In terms of control strategy, a fuzzy PID collaborative architecture is proposed to achieve ±0.1mm synchronization accuracy and a speed fluctuation rate of <1%. In terms of energy efficiency optimization, electromagnetic force assists oil suction during the no-load phase, reducing 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, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hydraulic synchronous control system based on traveling wave magnetic field composite drive, characterized by: It includes multiple hydraulic cylinders, which include piston rod assemblies and cylinder barrels. 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 liner. 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. The pressure sensor and the displacement sensor are both communicatively connected to the controller, and the controllers are communicatively connected to each other. The hydraulic cylinders are cross-coupled and compensated, and the controller is communicatively connected to a time relay that calculates the displacement time of the metal push rod.

2. The hydraulic synchronous control system based on traveling wave magnetic field composite drive according to claim 1 is characterized in that: The three-phase winding module includes coils and silicon steel sheets. The coils and silicon steel sheets wrapped with high-temperature resistant enameled wires form a winding and are sealed with epoxy resin.

3. The hydraulic synchronous control system based on traveling wave magnetic field composite drive according to claim 1 or 2, characterized in that: 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-magnetic-permeability low-carbon steel.

4. A control method for a hydraulic synchronous control system based on a traveling wave magnetic field composite drive, characterized in that: The steps include: During the initialization phase, the system performs a self-test, powers on the controller, and sequentially reads the displacement sensors, pressure sensors, and coil impedance values ​​for each hydraulic cylinder. The hydraulic pump starts, and the controller simultaneously injects a preheating current into the coil, activating the magnetic field and detecting the eddy current response in the cylinder barrel. One of the hydraulic cylinders is designated as the master, and the remaining cylinders as slaves. The master cylinder's target speed is set, and the slave cylinder controllers receive the initial PID parameters from the master cylinder's displacement signal. During the load lifting phase, disturbance detection and compensation are performed. If the slave hydraulic cylinder lags behind due to eccentric load during the lifting process, the controller calculates the displacement error ΔL in real time, triggers fuzzy PID regulation, and compensates the thrust to quickly achieve error convergence. Precision positioning stage: When approaching the target, S-curve planning is activated, the traveling wave magnetic field is weakened and reversed, and the piston rod is smoothly decelerated to avoid mechanical shock. After reaching the target position, the excitation current is reduced, and the dynamic pressure maintenance of the hydraulic locking valve is combined to ensure stable positioning; During the no-load return stage, reverse thrust is generated by reversing the current phase, and the rodless cavity returns under the drive of the hydraulic pump. At the same time, the oil tank is bypassed and the reverse electromagnetic force is used to assist in oil suction, compensate for the oil supply demand of the hydraulic cylinder, increase the return speed, save energy and improve efficiency.

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