Double-servo-valve flow switching control system

Abstract

The invention relates to the technical field of hydraulic control interaction, and discloses a double-servo-valve flow switching control system which comprises a multi-channel controller, a hydraulic actuator, a second-stage servo valve and a third-stage servo valve, the second-stage servo valve and the third-stage servo valve are connected in parallel and integrated through a control valve block, and the multi-channel controller is provided with a large flow control mode, a small flow control mode and a corresponding PID parameter set. In a large-flow mode, the controller sends an opening signal to the independent enabling end of the third-stage servo valve, the double valves are controlled to cooperatively output, and the high-frequency response characteristic of the second-stage servo valve is used for compensating dynamic lag; and in the small flow mode, the controller sends a cut-off signal, so that the third-stage servo valve is forcibly reset and cuts off the branch, and the three-stage servo valve is independently driven only by the second-stage servo valve. Through asymmetric enabling control and parameter self-adaptive switching, seamless consideration of large-flow high-dynamic and small-flow high-precision working conditions in a single system is achieved, and low efficiency and pollution risks caused by manual valve replacement are avoided.

Description

Technical Field

[0001] This invention relates to the field of hydraulic control interaction technology, specifically a dual servo valve flow switching control system. Background Technology

[0002] With the rapid development of the automotive industry and the continuous expansion of the market, vehicle manufacturers are placing increasingly stringent performance requirements on key chassis components such as shock absorbers, axles, and air springs. To ensure the reliability and safety of these components, high-intensity bench tests must be conducted using hydraulic testing rigs during product development and mass production. Typically, for the same model of component, testing specifications cover two key aspects: performance testing and fatigue testing. These two types of tests have significantly different flow requirements for the hydraulic system.

[0003] When conducting component performance testing, hydraulic actuators often need to output high speeds or large displacements within a short period. This requires the control system to have a very high instantaneous flow throughput capacity, typically necessitating a three-stage electro-hydraulic servo valve with a large rated flow rate to meet testing requirements. However, during durability fatigue testing or low-speed characteristic testing, the system's flow rate requirement is lower, but the control accuracy of force or displacement and waveform reproducibility are extremely demanding. If a large-flow-rate three-stage servo valve is used for control in these situations, the valve core will operate in a small opening region near zero position for an extended period, resulting in reduced flow resolution, significant dead zone and hysteresis effects, making it difficult to meet the high-precision control requirements under low-flow conditions, and directly impacting the accuracy of experimental data.

[0004] To resolve the contradiction between a large flow range and high control precision, a common approach in existing technologies is to manually replace servo valves of different specifications depending on the type of experiment. For example, a high-flow valve is installed for performance testing, and then disassembled and replaced with a low-flow, high-precision valve when switching to fatigue testing, along with a corresponding adapter plate. This frequent hardware replacement not only interrupts the testing process due to downtime, significantly reducing experimental efficiency, but also inevitably causes hydraulic oil leakage and waste during disassembly and assembly. More seriously, frequent opening of hydraulic line interfaces can easily introduce external particulate contaminants into the precision hydraulic system, causing oil contamination. This not only accelerates the wear of hydraulic components but may even lead to serious malfunctions such as servo valve jamming, posing significant maintenance risks and economic losses to the long-term stable operation of the testing equipment. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a dual servo valve flow switching control system, which solves the problems that existing hydraulic testing systems cannot simultaneously meet the requirements of high-flow, high-dynamic performance testing and low-flow, high-precision fatigue testing on the same equipment, and that traditional manual valve changing methods are inefficient and pose a risk of contamination.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a dual servo valve flow switching control system, aiming to resolve the technical contradiction that existing single-valve control systems cannot simultaneously achieve high dynamic performance for large flow rates and high precision control for small flow rates. This system mainly includes a multi-channel controller, a hydraulic actuator, and a secondary servo valve and a tertiary servo valve integrated onto the hydraulic actuator via a control valve block.

[0007] At the system architecture level, this invention adopts a hydraulic parallel topology. The control valve block has internal flow channels that physically connect the inlet, return, and control ports of the secondary and tertiary servo valves to the corresponding ports of the hydraulic actuator. Through this parallel connection, the flow rates output by the secondary and tertiary servo valves converge within the control valve block, thus acting together on the hydraulic actuator. Specifically, the secondary servo valve is a moving-coil or torque motor type electro-hydraulic servo valve with a high dynamic response bandwidth; the tertiary servo valve is a main-stage electro-hydraulic servo valve with displacement feedback, possessing a large rated flow output capacity.

[0008] At the control logic level, this invention establishes an asymmetric control strategy based on independent enable signals. The multi-channel controller establishes electrical connections with two servo valves respectively, and uses a digital output channel to connect to the independent enable signal input terminal of the third-stage servo valve, and an analog output channel to connect to the drive terminal of the second-stage servo valve. The system presets a high-flow control mode and a low-flow control mode in the multi-channel controller according to operating conditions.

[0009] When the system operates in high-flow control mode, the multi-channel controller outputs a high-level opening signal to the enable signal input terminal of the three-stage servo valve, activating the main valve stage of the three-stage servo valve. At this time, the multi-channel controller simultaneously sends the same drive command to both servo valves, and the two work together, with the output flow superimposed to drive the hydraulic actuator. During this process, the system utilizes the physical characteristic that the response bandwidth of the two-stage servo valve is higher than that of the three-stage servo valve to implement dynamic compensation control: when the drive command undergoes high-frequency changes or rapid reversals, the two-stage servo valve responds first and outputs transient flow, compensating for the response lag of the three-stage servo valve caused by its large inertia, thereby improving the system's dynamic following performance under high-flow conditions.

[0010] When the system operates in low-flow control mode, the multi-channel controller outputs a low-level cutoff signal to the enable signal input of the three-stage servo valve. The internal circuitry of the three-stage servo valve is de-energized, and its main valve core is forced back to its physical neutral position under the action of the reset mechanism. Based on the zero-position zero-coverage or positive-coverage characteristics of the three-stage servo valve, this reset action physically isolates the hydraulic branch where the three-stage servo valve is located, eliminating potential leakage or interference at high-flow valve ports. At this time, the load flow of the hydraulic actuator is entirely provided independently by the two-stage servo valve, achieving precise regulation of minute flow rates.

[0011] At the algorithm adaptation level, this invention introduces a parameter adaptive switching mechanism. The multi-channel controller internally stores a first PID parameter set adapted to the parallel operation of two valves and a second PID parameter set adapted to the independent operation of a single valve. The controller monitors the state of the enable signal, calling the first PID parameter set when outputting an enable signal and synchronously switching to the second PID parameter set when outputting a cutoff signal. This logic ensures that the electronic gain of the control algorithm can match the drastic changes in the physical flow gain of the hydraulic system in real time, guaranteeing the closed-loop stability and response consistency of the system during different mode switching processes.

[0012] In addition, the system transmits signals through twisted-pair shielded cables and single-end grounding, and performs closed-loop calculations in conjunction with status sensors and valve core displacement feedback signals, further ensuring the anti-interference capability and execution accuracy of control command transmission.

[0013] This invention achieves seamless switching between high-flow and low-flow operating conditions within a single system by combining the aforementioned hardware topology and control strategy. It leverages the high-flow advantage of the three-stage valve while retaining the high-frequency response and high-resolution characteristics of the two-stage valve.

[0014] This invention provides a dual servo valve flow switching control system. It has the following advantages:

[0015] 1. This invention solves the contradiction that a single valve cannot simultaneously meet the needs of large-flow drive and precise adjustment of small flow by constructing a hydraulic parallel topology of a two-stage servo valve and a three-stage servo valve, and by combining the on / off control of the independent enable terminal of the three-stage servo valve. In the high-flow mode, the dual valves work together to meet the high-power load requirements. In the low-flow mode, the cut-off signal is used to force the three-stage servo valve to physically reset and block the branch, and only the high-resolution two-stage servo valve can independently adjust. This effectively eliminates nonlinear interference and leakage near the zero position of the valve port in the high-flow mode, and improves the system resolution and control accuracy in the low-flow condition.

[0016] 2. This invention utilizes the physical characteristic that the dynamic response bandwidth of the two-stage servo valve is higher than that of the three-stage servo valve to establish a transient flow compensation mechanism in high-flow collaborative control. When the drive command undergoes high-frequency sudden change or rapid reversal, the two-stage servo valve can respond and output compensation flow before the three-stage servo valve with large inertia, filling the flow gap caused by the response lag of the three-stage servo valve. This overcomes the inherent defect of slow dynamic response in traditional high-flow hydraulic systems and optimizes the dynamic following characteristics of the system.

[0017] 3. This invention solves the control problem caused by drastic changes in the physical gain of the hydraulic system by using PID parameter adaptive switching logic synchronized with hardware mode switching. The multi-channel controller calls the matching PID parameter set in real time according to the enable signal status, adapting to the high flow gain when two valves are connected in parallel and the low flow gain when a single valve is independent, effectively suppressing oscillation and overshoot during mode switching, and ensuring that the system has consistent control quality and stability throughout the full flow operating range. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall system structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the hydraulic circuit connection and internal flow channel structure of the present invention;

[0020] Figure 3 This is a schematic diagram of the adaptive switching logic flow for control parameters of the present invention.

[0021] Among them, 1. Multi-channel controller; 2. Hydraulic actuator; 21. Control valve block; 3. Secondary servo valve; 4. Tertiary servo valve. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] See attached document Figure 1 This invention provides a dual servo valve flow switching control system, which mainly includes: a multi-channel controller 1, a hydraulic actuator 2, a secondary servo valve 3, and a tertiary servo valve 4. The multi-channel controller 1 is the control core of the system, configured to generate control commands, process feedback signals, and execute PID control algorithms. The hydraulic actuator 2 is the system's execution mechanism, used to convert hydraulic energy into mechanical energy to drive the load in linear reciprocating motion. Both the secondary servo valve 3 and the tertiary servo valve 4 are electro-hydraulic flow control valves, used to adjust the flow rate and direction of hydraulic oil entering the hydraulic actuator 2 according to the received electrical signals.

[0024] The multi-channel controller 1 includes signal input ports, signal output ports, and a data processing unit. The multi-channel controller 1 is equipped with at least two independent analog output channels and one digital output channel, used to send control signals to the secondary servo valve 3 and the tertiary servo valve 4, respectively. The multi-channel controller 1 is also equipped with an analog input channel for acquiring displacement sensor signals or force sensor signals from the hydraulic actuator 2, and valve core displacement feedback signals from the tertiary servo valve 4, thereby forming a closed-loop control system.

[0025] The hydraulic actuator 2 integrates a control valve block 21. The control valve block 21 has interfaces connecting to an external hydraulic power source and a return oil tank, as well as a flow channel connecting to the internal piston chamber of the hydraulic actuator 2. Specifically, the control valve block 21 has an oil inlet P, an oil return port T, a first control port A, and a second control port B. The oil inlet P is connected to a high-pressure oil source, the oil return port T is connected to a low-pressure return oil tank, the first control port A is connected to either the rod-side or rodless side chamber of the hydraulic actuator 2, and the second control port B is connected to either the rodless or rod-side side chamber of the hydraulic actuator 2.

[0026] The secondary servo valve 3 is an electro-hydraulic servo valve with high-frequency response characteristics, such as the G761 series moving-coil or torque motor servo valve. The secondary servo valve 3 is fixedly mounted on the first mounting position of the control valve block 21 using screws. The secondary servo valve 3 has a valve body inlet P3, a valve body return port T3, a valve body control port A3, and a valve body control port B3. Physically, the valve body inlet P3, valve body return port T3, valve body control port A3, and valve body control port B3 are respectively connected to the inlet P, return port T, first control port A, and second control port B on the control valve block 21.

[0027] The three-stage servo valve 4 is an electro-hydraulic servo valve with high flow characteristics, such as the D791 or D792 series master-stage servo valve with displacement feedback. The three-stage servo valve 4 is fixedly mounted on the second mounting position of the control valve block 21 using screws. The three-stage servo valve 4 has a valve body inlet P4, a valve body return port T4, a valve body control port A4, and a valve body control port B4. Physically, the valve body inlet P4, valve body return port T4, valve body control port A4, and valve body control port B4 are respectively connected to the inlet P, return port T, first control port A, and second control port B on the control valve block 21.

[0028] Based on the above connection structure, the secondary servo valve 3 and the tertiary servo valve 4 form a parallel topology in the hydraulic circuit. The flow channel inside the control valve block 21 merges the hydraulic oil flow output from the secondary servo valve 3 and the hydraulic oil flow output from the tertiary servo valve 4, and the total flow after merging is input to the same working chamber of the hydraulic actuator 2. When both the secondary servo valve 3 and the tertiary servo valve 4 are open, the system output flow is the algebraic sum of their flow rates; when only the secondary servo valve 3 is open, the system output flow is provided solely by the secondary servo valve 3.

[0029] In terms of electrical connection, the multi-channel controller 1 is electrically connected to the secondary servo valve 3 via a first shielded cable. The secondary servo valve 3 has a 4-pin interface, where pins A and B (or pins C and D) are connected to the analog output channel of the multi-channel controller 1 to receive drive current signals. The secondary servo valve 3 does not have an external enable signal control terminal; when the system is powered on, its valve core displacement always responds to the drive signal output by the multi-channel controller 1.

[0030] The multi-channel controller 1 is electrically connected to the three-stage servo valve 4 via a second shielded cable. The three-stage servo valve 4 has a 6-pin interface, including a positive power supply terminal A, a negative power supply terminal B, an enable signal input terminal C, a positive command input terminal D, a negative command input terminal E, and a valve spool displacement feedback terminal F. The positive power supply terminal A and the negative power supply terminal B are connected to a 24V DC power supply; the positive command input terminal D and the negative command input terminal E are connected to the analog output channel of the multi-channel controller 1; and the valve spool displacement feedback terminal F is connected to the analog input channel of the multi-channel controller 1. The enable signal input terminal C is connected to the digital output channel of the multi-channel controller 1 to receive logic level signals that enable or disable the three-stage servo valve 4.

[0031] See attached document Figure 2 This section details the fluid physical connection relationship and flow channel topology between the hydraulic actuator 2, control valve block 21, secondary servo valve 3, and tertiary servo valve 4.

[0032] The control valve block 21 serves as the hydraulic fluid distribution and confluence center of the system. Its interior is precision-machined to form a main oil supply channel, a main oil return channel, a first load channel, and a second load channel. The physical outer surface of the control valve block 21 is provided with a common interface (P, T) for connecting external pipelines and two independent mounting interfaces for installing servo valves, namely the first mounting interface and the second mounting interface.

[0033] The first mounting interface is used to fit and install the secondary servo valve 3. This interface has four oil passage holes that match the positions and diameters of the P3, T3, A3, and B3 oil ports of the secondary servo valve 3. The second mounting interface is used to fit and install the tertiary servo valve 4. This interface has four oil passage holes that match the positions and diameters of the P4, T4, A4, and B4 oil ports of the tertiary servo valve 4. The bottom surfaces of the secondary servo valve 3 and the tertiary servo valve 4 are pressed tightly against the first and second mounting interfaces by sealing elements (such as O-rings), and are rigidly fixed by screwing high-strength screws into the threaded holes of the control valve block 21 to ensure no external leakage under high-pressure conditions.

[0034] The internal flow path of the control valve block 21 incorporates fully hydraulic parallel logic. The specific connection topology is as follows:

[0035] First, parallel connection on the oil supply side: one end of the main oil supply channel of the control valve block 21 is connected to the external high-pressure oil source interface P, and the other end branches internally, connecting to the P3 oil passage hole of the first mounting interface and the P4 oil passage hole of the second mounting interface respectively. Thus, the system oil supply pressure... At the same time, it acts equally on the oil inlet of the second-stage servo valve 3 and the oil inlet of the third-stage servo valve 4.

[0036] Second, parallel connection on the oil return side: the T3 oil passage on the first mounting interface and the T4 oil passage on the second mounting interface converge into the main oil return channel inside the control valve block 21, and finally connect to the external oil return interface T. Thus, the back pressure of the oil return of the two servo valves... Maintain consistency.

[0037] Third, load-side flow convergence: This is the key physical basis for the flow switching and coordinated control of this system. The first load channel inside the control valve block 21 is simultaneously connected to the A3 oil passage of the first mounting interface and the A4 oil passage of the second mounting interface, and guides the converged hydraulic oil to the first working chamber (e.g., the rodless chamber) of the hydraulic actuator 2; the second load channel inside the control valve block 21 is simultaneously connected to the B3 oil passage of the first mounting interface and the B4 oil passage of the second mounting interface, and guides the converged hydraulic oil to the second working chamber (e.g., the rod chamber) of the hydraulic actuator 2.

[0038] Based on the above structure, the instantaneous total load flow entering the hydraulic actuator 2 Physically, it is strictly equal to the vector sum of the output flow rates of the two servo valves. Its fluid continuity relationship can be described by the following equilibrium equation:

[0039] ;

[0040] in, The flow rate through the secondary servo valve 3, The flow rate is the flow rate through the three-stage servo valve 4.

[0041] The physical characteristic of this parallel structure lies in its dual function of hydraulic superposition and hydraulic isolation: in the state of hydraulic superposition, both flow channels are opened simultaneously to achieve a large flow output.

[0042] In hydraulic isolation mode, when the three-stage servo valve 4 is closed (valve core physically neutral), its valve core shoulder completely covers the throttling window inside the valve body. Because the clearance between the valve core and valve sleeve of the three-stage servo valve 4 is at the micrometer level, and its neutral position design employs a zero-coverage or positive-coverage structure, the four ports P4, T4, A4, and B4 of the three-stage servo valve 4 are physically blocked inside the valve body. For the first and second load channels, the three-stage servo valve 4 is equivalent to a rigid hydraulic plug at this moment. At this time, the volume change of the hydraulic actuator 2 is entirely determined by the output flow of the second-stage servo valve 3. This decision eliminates potential leakage interference or volumetric effects that might be introduced by high-flow-rate valves, ensuring control stiffness and resolution under low-flow-rate conditions.

[0043] This section details the electrical interface definition, signal transmission logic, and hardware connection specifications between the multi-channel controller 1, the secondary servo valve 3, and the tertiary servo valve 4.

[0044] As the core control unit of the system, the multi-channel controller 1 is equipped with an analog output module (AO), a digital output module (DO), and an analog input module (AI) at its hardware interface level. To ensure signal purity during high-frequency response control, the connection cables between the multi-channel controller 1 and each servo valve are all shielded twisted-pair cables, and the shielding is grounded at one end to suppress electromagnetic interference.

[0045] For the electrical connection of the secondary servo valve 3, a four-pin aviation connector is used as the electrical interface. The specific pin definitions and connections are as follows: The interface of the secondary servo valve 3 includes a first coil drive terminal (pin A) and a second coil drive terminal (pin B). These two pins are electrically connected to the positive and negative terminals of the first analog output channel of the multi-channel controller 1, respectively. The multi-channel controller 1 outputs a continuously varying current signal (e.g., -40mA to +40mA) or voltage signal through this channel to directly drive the torque motor or moving coil actuator inside the secondary servo valve 3. It should be noted that the hardware architecture of the secondary servo valve 3 does not include a separate logic enable pin. Therefore, at the physical connection level, as long as the multi-channel controller 1 is powered on, the secondary servo valve 3 is in a standby and controlled state. The movement of its valve core completely and in real time follows the command signal of the first analog output channel, and there is no hardware-level logic cutoff or lockout function. This always-on connection characteristic ensures that the secondary servo valve 3 can respond to control commands without delay at any moment of switching between operating conditions.

[0046] For the electrical connection of the three-stage servo valve 4, a six-pin aviation connector is used as the electrical interface, integrating four functions: power supply, logic control, command drive, and status feedback. The specific pin definitions and connection relationships are as follows:

[0047] First, the power supply circuit: Pin A (positive power supply) and Pin B (ground power supply) of the three-stage servo valve 4 are respectively connected to the system's independent 24V DC regulated power supply. This circuit provides operating power for the valve-on-board integrated amplifier and control electronics.

[0048] Second, the command loop: Pin D (command positive) and pin E (command negative) of the three-stage servo valve 4 are connected to the positive and negative terminals of the second analog output channel of the multi-channel controller 1, respectively. This channel is used to transmit control command signals (typically ±10V voltage signals) representing the desired flow rate and direction.

[0049] Third, feedback loop: Pin F (valve core displacement feedback) of the three-stage servo valve 4 is connected to the analog input channel of the multi-channel controller 1. This pin outputs a voltage signal that is proportional to the actual physical displacement of the main valve core. The multi-channel controller 1 collects this signal to monitor the working status of the valve and to build closed-loop control or fault diagnosis logic for the valve core position.

[0050] Fourth, the enable logic loop (key feature): Pin C (enable input) of the three-stage servo valve 4 is connected to the digital output channel (DO) of the multi-channel controller 1. This connection forms the hardware foundation for the dual-mode switching of this system. Pin C is configured to receive binary logic voltage signals: when the multi-channel controller 1 outputs a high-level logic voltage (e.g., 24V) to pin C, the electronic control unit inside the three-stage servo valve 4 is activated, and the valve enters the working mode. At this time, the valve core displacement follows the command signals received by pins D and E, performing flow regulation actions.

[0051] When the multi-channel controller 1 outputs a low-level logic voltage (e.g., 0V) or leaves the pin C floating, the three-stage servo valve 4 internally triggers a safety reset mechanism, entering the shut-off mode. In this mode, regardless of the command signals received by pins D and E, the internal circuitry of the valve forcibly cuts off the drive to the pilot stage and uses a reset spring or hydraulic pressure to force the main valve spool back and lock it in the physical zero position (neutral position). This hardware logic ensures that when the enable signal is cut off, the three-stage servo valve 4 can reliably close the flow path, becoming a locking element in the hydraulic system without relying on an external shut-off valve.

[0052] This section details how the multi-channel controller 1 coordinates the control of the secondary servo valve 3 and the tertiary servo valve 4 when the system is operating at high flow rates, and the specific technical implementation of dynamic flow compensation using the frequency response difference between the two valves.

[0053] When the experimental task is set as a performance experiment (such as a shock absorber indicator diagram test or a high-frequency long-stroke fatigue test), and the required flow exceeds the preset threshold (such as exceeding the rated flow of the secondary servo valve 3), the system enters control mode one, namely the dual-valve collaborative control mode.

[0054] In this mode, the multi-channel controller 1 first performs a hardware enable operation. The multi-channel controller 1 continuously outputs a high-level logic voltage (e.g., 24V) to the enable signal input terminal C of the three-stage servo valve 4 through its digital output channel. Upon receiving this enable signal, the pilot stage coil inside the three-stage servo valve 4 is energized, the hydraulic pre-stage establishes control pressure, releases the zero-position lock-up state of the main valve core, and allows the three-stage servo valve 4 to enter a controllable operating state. Simultaneously, the second-stage servo valve 3, due to its constantly controlled characteristics, remains in a ready-to-operate state.

[0055] Subsequently, the multi-channel controller 1 distributes control commands and performs dual-loop regulation. The multi-channel controller 1 generates target control commands based on preset waveform functions (such as sine waves, triangle waves, or path spectra). And combined with the sensor feedback signal from hydraulic actuator 2 Calculate the current control deviation of the system .

[0056] ;

[0057] Based on this deviation, the PID algorithm unit inside the multi-channel controller 1 calls the first set of control parameters ( ), calculate the total control quantity This control quantity The signal is simultaneously mapped to two analog output channels, which are transmitted to the drive terminal (pins A / B) of the secondary servo valve 3 and the command input terminal (pin D / E) of the tertiary servo valve 4, respectively. At this time, the total load flow entering the hydraulic actuator 2... The sum of the instantaneous output flow rates of the two valves:

[0058] ;

[0059] in, and These are the flow gains for the secondary and tertiary valves, respectively. and These represent the spool displacements of the secondary and tertiary valves, respectively. Oil supply pressure, Load pressure.

[0060] The core technical feature of this embodiment lies in utilizing the high-frequency response characteristics of the two-stage servo valve 3 to dynamically compensate the three-stage servo valve 4. Physically, the three-stage servo valve 4, due to its large rated flow rate (e.g., above 60 L / min), has a large main valve core diameter, is heavy, and includes a three-stage hydraulic amplification stage, resulting in a low dynamic response bandwidth (e.g., approximately 30 Hz-50 Hz). This leads to significant phase lag and dynamic dead zone during rapid commutation or zero-crossing. Conversely, the two-stage servo valve 3 (e.g., the G761 series) employs a direct-drive or two-stage amplification structure, exhibiting extremely high dynamic response bandwidth (e.g., bandwidth exceeding Hz) and minimal phase lag.

[0061] During the coordinated control process, when the target control command When a high-frequency abrupt change occurs or when passing through a zero-position commutation point:

[0062] First stage, transient response: Due to inertial differences, the valve core displacement of the three-stage servo valve 4... Unable to immediately follow control quantity The change in [the output flow] causes its output flow rate to [be affected]. Lagging behind instructions, system deviation There is a tendency for it to increase.

[0063] Second stage: Rapid compensation: Multi-channel controller 1 detects deviation. The presence of the control quantity maintains or adjusts the control quantity. At this point, the secondary servo valve 3, which has high-frequency response characteristics, is the first to respond to the control input. Its valve core displacement Quickly establish and output traffic This portion of traffic It quickly fills the working chamber of the hydraulic actuator 2, filling the flow gap left by the three-stage servo valve 4 due to the lag in response.

[0064] In the third stage, steady-state following: as time goes by (milliseconds), the valve core of the third-stage servo valve 4 gradually moves into position, providing the main flow support. At this time, the second-stage servo valve 3 continues to cooperate with fine-tuning to correct the overshoot.

[0065] Through the above mechanism, the system actually constructs a macro-micro composite drive model: the three-stage servo valve 4 acts as a coarse-adjustment actuator, providing a large base flow output to meet speed requirements; the two-stage servo valve 3 acts as a fine-adjustment actuator, using its rapid response capability to repair waveform details and eliminate commutation flat tops and waveform distortion. This parallel connection at the physical level and the co-source drive at the control level enable the system to achieve dynamic response accuracy close to that of a small-flow servo valve while outputting a large flow, thereby ensuring a high degree of overlap between the feedback waveform and the command waveform.

[0066] This section details how, when the system is operating under low-flow, high-precision conditions, the multi-channel controller 1 uses hardware logic to block the hydraulic path of the three-stage servo valve 4 and achieves independent, high-precision control using only the two-stage servo valve 3.

[0067] When the experimental task is set as a durability test or fatigue test, and the required flow rate is in a low range (e.g., less than 80% of the rated flow rate of the secondary servo valve 3), the system enters control mode two, namely the single valve independent control mode.

[0068] In this mode, the multichannel controller 1 performs an electronic shut-off operation for the three-stage servo valve 4. The digital output signal of the multichannel controller 1 connected to the enable input C of the three-stage servo valve 4 is switched to a low-level state (e.g., 0V) or a high-impedance state.

[0069] Once the voltage signal at the enable input terminal C is removed, the integrated control circuit inside the three-stage servo valve 4 immediately cuts off the drive current to the pilot stage. At this time, regardless of whether there is control voltage at the command input terminals D and E, the three-stage servo valve 4 will no longer respond. Under the action of the return spring and hydraulic centering force inside the valve, the main valve core of the three-stage servo valve 4 is forcibly pushed back and mechanically locked in the geometric null position.

[0070] Based on the zero-lap or positive-lap spool valve structure of the three-stage servo valve 4, when the valve core is in the geometric neutral position, the hydraulic flow path between the valve body inlet P4, the valve body return port T4, and the valve body control ports A4 and B4 is physically isolated by the valve core shoulder. At this time, the three-stage servo valve 4 becomes a normally closed hydraulic damping element. For the parallel flow path inside the control valve block 21, the flow rate of the branch where the three-stage servo valve 4 is located... Reduced to zero (ignoring trace amounts of static internal leakage), that is:

[0071] ;

[0072] At this point, the movement of hydraulic actuator 2 is completely taken over by the secondary servo valve 3. Multichannel controller 1 continues to send control commands to the secondary servo valve 3 through the first analog output channel. Since the secondary servo valve 3 is always in a controlled state, its valve core displacement... The flow rate into hydraulic actuator 2 is adjusted in real time according to the command. At this time, the total load flow equation of the system simplifies to:

[0073] ;

[0074] in, Total load flow The flow rate through the secondary servo valve 3, For the flow gain of the secondary valve, This refers to the valve core displacement of the secondary valve. Oil supply pressure, Load pressure.

[0075] The technical advantage of this control mode lies in solving the nonlinearity problem of small opening degree in high-flow-rate servo valves under low-flow-rate conditions. In hydraulic servo control, if a three-stage servo valve 4 with a huge rated flow rate is directly used to control a small flow rate, the valve core will operate in a very small opening range near zero position for a long time (e.g., opening degree less than 2%). Within this range, due to the influence of machining tolerances, zero-position dead zone, and hydraulic interference, the linearity of the flow gain is poor, resulting in steps or jitter in the control waveform, which seriously affects the accuracy of the data in the durability test.

[0076] By switching to this mode, the system utilizes a secondary servo valve 3 with a smaller rated flow rate to handle the control task. To output the same minute flow rate, the secondary servo valve 3 has a larger valve core opening percentage (e.g., 20%-40%), thus avoiding the zero-position dead zone and operating in a region with better flow gain linearity. This significantly improves the system's resolution and execution accuracy for minute commands.

[0077] Furthermore, during long-term durability testing cycles (typically lasting millions of cycles), the three-stage servo valve 4 remains stationary and closed, preventing mechanical wear and erosion of the throttling edges caused by the high-frequency, micro-amplitude reciprocating motion of its main valve core. This significantly extends the service life of the high-value three-stage servo valve 4 and reduces long-term maintenance costs.

[0078] See attached document Figure 3 This section details how the multi-channel controller 1 adjusts the control strategy synchronously at the software algorithm level while performing hardware condition switching to match the physical gain changes of the hydraulic system.

[0079] The internal storage unit of the multi-channel controller 1 is pre-configured and stores at least two independent sets of control parameters. The first parameter set... Corresponding to the high-flow-rate performance test mode (i.e., dual-valve cooperative operation), the second parameter set This corresponds to the low-flow endurance test mode (i.e., single-valve independent operating condition). Each parameter set includes proportional, integral, and derivative coefficients for the discrete PID control algorithm. The multi-channel controller 1 internally runs an operating condition monitoring logic module. This module monitors the system's target operating condition setpoint signal in real time. .when When a state transition occurs, the multi-channel controller 1 performs synchronized hardware and software actions:

[0080] At the hardware level, the multi-channel controller 1 changes the state of the digital output channel, thereby changing the voltage level (24V or 0V) applied to the enable input terminal C of the three-stage servo valve 4, physically opening or blocking the high-flow hydraulic passage.

[0081] At the software level, synchronously with the hardware actions, the processing core of the multi-channel controller 1 changes the address pointer of the PID algorithm, pointing to the parameter set that matches the current hardware state. Specifically, when the enable input C outputs a high level, the PID algorithm calls the first parameter set. When the enable input C outputs a low level, the PID algorithm calls the second parameter set. .

[0082] The multi-channel controller 1 uses a discrete-time PID control algorithm to calculate the control quantity. In the first Each sampling period, control quantity The calculation formula is as follows:

[0083] ;

[0084] in, This represents the value of the control command output by the controller at the current sampling time. This is the difference between the target value and the feedback value at the current sampling time; This is the deviation value at the previous sampling time; This is the cumulative sum of deviations from the initial time to the current time; This is the proportional gain coefficient; This is the integral gain coefficient; This represents the differential gain coefficient. In this embodiment, the necessity of parameter switching is based on the physical change in the system's open-loop gain.

[0085] Under dual-valve cooperative operation, the total flow gain of the system The flow gain of the secondary servo valve 3 and the flow gain of the three-stage servo valve 4 It is formed by stacking, that is .because The values ​​are relatively large, resulting in extremely high physical gain for the hydraulic system. If the controller maintains high gain parameters, the system is highly susceptible to overshoot or oscillation. Therefore, the first parameter set... In It is usually set to a smaller value to ensure system stability under high traffic.

[0086] In this embodiment, the necessity of parameter switching is based on the physical change of the system open-loop gain.

[0087] Under dual-valve cooperative operation, the total flow gain of the system The flow gain of the secondary servo valve 3 and the flow gain of the three-stage servo valve 4 It is formed by stacking, that is .because The values ​​are relatively large, resulting in extremely high physical gain for the hydraulic system. If the controller maintains high gain parameters, the system is highly susceptible to overshoot or oscillation. Therefore, the first parameter set... In It is usually set to a smaller value to ensure system stability under high traffic.

[0088] In single-valve independent operation, the third-stage servo valve 4 is physically shut off, and the total flow gain of the system drops sharply to be provided solely by the second-stage servo valve 3. At this point, the physical gain of the hydraulic system is low. If a small control gain is continued to be used, the dynamic response of the system will become sluggish, and the tracking error will increase. Therefore, the second parameter set... In It is usually set to a larger value to improve system sensitivity and response speed under low flow conditions.

[0089] By establishing various mapping relationships between the enable signal state and the PID parameter address through the multi-channel controller 1, the system ensures that the mathematical model parameters of the control algorithm are updated simultaneously with each physical flow channel switch, achieving real-time impedance matching between the controller's electronic gain and the hydraulic system's physical gain. This adaptive switching logic eliminates the risk of system instability or response hysteresis caused by drastic changes in flow gain, ensuring that the system can complete a smooth transition from high-flow-rate conditions to low-flow-rate conditions and high-precision control reconfiguration within seconds.

Claims

1. A dual servo valve flow switching control system, characterized in that, include: A multi-channel controller (1), a hydraulic actuator (2), and a secondary servo valve (3) and a tertiary servo valve (4) mounted in parallel on a control valve block (21) integrated on the hydraulic actuator (2). The multi-channel controller (1) is electrically connected to the secondary servo valve (3) and the tertiary servo valve (4) respectively, and is used to output control signals in the high flow control mode and the low flow control mode; The three-stage servo valve (4) is equipped with an independent enable signal input terminal controlled by the multi-channel controller (1), and the two-stage servo valve (3) continuously responds to the drive commands of the multi-channel controller (1); the multi-channel controller (1) has the following control logic: In the high flow control mode, an opening signal is output to the enable signal input terminal to control the opening of the three-stage servo valve (4), and the two-stage servo valve (3) and the three-stage servo valve (4) are controlled to work together to output flow to the hydraulic actuator (2); In the low flow control mode, a cut-off signal is output to the enable signal input terminal to control the three-stage servo valve (4) to be forcibly reset and block the hydraulic branch where it is located, and only the two-stage servo valve (3) is controlled to independently output flow to the hydraulic actuator (2).

2. The dual servo valve flow switching control system according to claim 1, characterized in that, The control valve block (21) is provided with an oil inlet P, an oil return port T, a first control port A and a second control port B that are connected to the hydraulic actuator (2); Each valve body port of the secondary servo valve (3) and the tertiary servo valve (4) is connected to the oil inlet P, the oil return port T, the first control port A and the second control port B on the control valve block (21), so that the flow rate output by the secondary servo valve (3) and the flow rate output by the tertiary servo valve (4) merge inside the control valve block (21).

3. The dual servo valve flow switching control system according to claim 1, characterized in that, The electrical interface of the three-stage servo valve (4) includes a power input terminal, a command input terminal, a feedback signal output terminal, and an enable signal input terminal; the enable signal input terminal is connected to the digital output channel of the multi-channel controller (1); The electrical interface of the secondary servo valve (3) includes a coil drive end, which is connected to the analog output channel of the multi-channel controller (1). The secondary servo valve (3) does not have an external enable signal input end, and the valve core displacement of the secondary servo valve (3) follows the signal change of the analog output channel in real time.

4. The dual servo valve flow switching control system according to claim 1, characterized in that, The dynamic response bandwidth of the secondary servo valve (3) is higher than that of the tertiary servo valve (4); In the high flow control mode, the multi-channel controller (1) sends the same driving command to the secondary servo valve (3) and the tertiary servo valve (4); when the driving command changes at a high frequency, the secondary servo valve (3), which has a high dynamic response bandwidth, outputs transient compensation flow to compensate for the flow deviation caused by the lag in the response of the tertiary servo valve (4).

5. The dual servo valve flow switching control system according to claim 1, characterized in that, The three-stage servo valve (4) has zero-position zero-coverage or positive-coverage characteristics; When the multi-channel controller (1) outputs the cut-off signal to the enable signal input terminal, the internal circuit of the three-stage servo valve (4) is de-energized, and the main valve core of the internal circuit of the three-stage servo valve (4) is locked in the physical neutral position under the action of the reset mechanism, thereby physically isolating the inlet and outlet ports of the three-stage servo valve (4).

6. The dual servo valve flow switching control system according to claim 1, characterized in that, The multi-channel controller (1) internally stores a first PID parameter set and a second PID parameter set; The multi-channel controller (1) has parameter adaptive switching logic: when the start signal is output, the first PID parameter set is called to perform closed-loop control calculation to adapt to the total system flow gain when the two valves are connected in parallel; when the stop signal is output, the controller is synchronously switched to the second PID parameter set to perform closed-loop control calculation to adapt to the system flow gain when only driven by the second-stage servo valve (3).

7. The dual servo valve flow switching control system according to claim 3, characterized in that, The multi-channel controller (1) is also connected to the status sensor of the hydraulic actuator (2); The multi-channel controller (1) calculates the control deviation based on the preset target command signal, the actual signal fed back by the state sensor and the valve core displacement signal fed back by the feedback signal output terminal, and calculates the control quantity based on the selected PID parameter set.

8. The dual servo valve flow switching control system according to claim 1, characterized in that, The secondary servo valve (3) is a moving coil type or torque motor type electro-hydraulic servo valve, and the rated flow of the secondary servo valve (3) is less than the rated flow of the tertiary servo valve (4); the tertiary servo valve (4) is a primary electro-hydraulic servo valve with displacement feedback.

9. A dual servo valve flow switching control system according to claim 1, characterized in that, In the high flow control mode, the total load flow entering the hydraulic actuator (2) is composed of the output flow of the secondary servo valve (3) and the output flow of the tertiary servo valve (4); In the low flow control mode, the output flow of the three-stage servo valve (4) is blocked, and the total load flow is substantially equal to the output flow of the two-stage servo valve (3).

10. A dual servo valve flow switching control system according to claim 3, characterized in that, The turn-on signal is a high-level voltage signal, and the turn-off signal is a low-level voltage signal; The multi-channel controller (1) is connected to the secondary servo valve (3) and the tertiary servo valve (4) respectively via twisted-pair shielded cables, and the shielding layer of the shielded cable is grounded at one end.

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