Nonlinear flutter control method giving consideration to high-dynamic low-hysteresis and micro-motion characteristics of proportional valve

Abstract

The invention discloses a nonlinear flutter control method considering high-dynamic low-hysteresis and micro-motion characteristics of a proportional valve, and belongs to the field of proportional valve control. The method comprises the following steps: acquiring a detection signal of a controlled proportional valve in real time, and performing mean filtering processing on the real-time detection signal to filter a flutter part so as to obtain a basic detection signal; the controller obtains the valve front and valve back pressure difference, the target control signal current and the basic detection signal of the current proportional valve; the frequencies and the amplitudes of the driving control signal and the optimal flutter control signal are obtained; and the driving control signal and the flutter control signal finish addition operation in the controller to obtain an equivalent control signal, so that the control of the controlled proportional valve is realized. The method is applied to a closed loop feedback link, and hysteresis can be greatly reduced. Under the control method, the valve element is always in a macroscopic stable and microcosmic jittering state, so that the speed of responding to a control signal is higher, the dead zone and saturation zone range of a proportional valve current-displacement curve can be reduced, and the linearity is higher.

Description

Technical Field

[0001] The invention belongs to the field of proportional valve control, and in particular relates to a nonlinear flutter control method taking into account high dynamic, low hysteresis and micro-motion characteristics of a proportional valve. Background Art

[0002] Due to the sliding valve structure of the proportional valve, friction will inevitably occur between the valve core and the valve body during the movement, and friction is one of the main reasons for the hysteresis phenomenon of the proportional valve. When the proportional valve receives a motion control signal, the valve core needs to overcome static friction greater than dynamic friction from static to moving. At this time, a larger driving current needs to be provided to the electromagnetic coil to generate a larger driving force to counter the static friction in order to make the valve core produce initial displacement. This phenomenon of the valve core movement being blocked will lead to problems such as proportional valve dead zone, poor micro-motion characteristics, valve core displacement hysteresis, flow hysteresis, etc., thereby reducing the repeatability of the proportional valve open-loop control system, and will also cause the closed-loop control system to oscillate or even fail.

[0003] The main causes of proportional valve hysteresis include friction, spring deformation hysteresis, hysteresis, fluid dynamics, mechanical clearance and assembly errors, and temperature changes. Under ideal conditions, the relationship between valve core displacement and coil current should be as follows: Figure 1 However, in actual working conditions, the coil current-valve core displacement curve when the valve core extends and retracts is as follows Figure 2 As shown in the figure, when the valve core extends, the valve core will move only when the coil current reaches a certain value, forming a dead zone, and when the coil current has not reached the rated maximum current of the coil, the valve core reaches the maximum displacement, forming a saturation zone; similarly, when the valve core retracts, the valve core will start to move and retract when the coil current decreases to a certain value, and when the coil current has not yet decreased to 0, the valve core reaches 0 displacement. The above hysteresis phenomenon greatly weakens the control performance of the proportional valve.

[0004] There are also proportional valves equipped with valve core displacement sensors in industrial applications. The valve core displacement sensors of such proportional valves can detect the valve core displacement in real time and can basically eliminate the valve core displacement hysteresis problem. However, due to the above-mentioned obstruction of the valve core movement, there are still problems such as slow response and poor micro-motion performance.

[0005] There are many solutions to the above problems, such as compensation method based on Coulomb friction model, compensation method based on Karnopp friction model, flutter compensation method, etc. Among them, flutter compensation method is the most widely used, which superimposes low-amplitude flutter signal into control signal, so that the valve core can move microscopically while keeping macroscopically still, thus avoiding the influence of static friction, and finally improving the dynamic performance and proportional control performance of proportional valve, and reducing hysteresis.

[0006] After investigation, it was found that the existing flutter compensation research applied flutter signals of constant frequency and amplitude to the proportional valve at different openings. However, when the proportional valve is at different openings, the hydraulic force, impact, damping and mechanical properties of the valve acting on the valve core will change, and the force condition of the valve core will become extremely complicated. For example, as the displacement of the valve core changes, the flutter amplitude of the valve core will show nonlinear attenuation phenomenon [1]. Therefore, in engineering applications, it is necessary to apply flutter signals of different frequencies and amplitudes to the proportional valve at different openings and working conditions to ensure the consistency of the flutter behavior of the valve core within the travel range. Summary of the invention

[0007] In order to solve the problems in the prior art, the present invention proposes a nonlinear flutter control method that takes into account the high dynamic, low hysteresis and micro-motion characteristics of a proportional valve.

[0008] The technical solution of the present invention is as follows:

[0009] The present invention first provides a nonlinear flutter control method taking into account high dynamic, low hysteresis and micro-motion characteristics of a proportional valve, which comprises the following steps:

[0010] 1) Acquire the detection signal of the controlled proportional valve in real time, perform mean filtering on the real-time detection signal to filter out the chatter signal, and obtain the basic detection signal;

[0011] 2) The controller obtains the current pressure difference ΔP before and after the controlled proportional valve j , external input target control signal and real-time basic detection signal; obtain the drive control signal according to the real-time basic detection signal and the target control signal, and obtain the best flutter control signal under the current conditions from the database according to the current valve front and rear pressure difference and the target control signal; the database pre-stores different valve front and rear pressure differences ΔP of the controlled proportional valve in the current usage scenario j , the frequency and amplitude of the optimal flutter control signal under the target control signal;

[0012] 3) The controller adds the drive control signal and the optimal dither control signal to obtain an equivalent control signal, and then performs PWM waveform equivalent conversion on the equivalent control signal to convert it into a control signal;

[0013] 4) The power amplifier converts the control signal into coil voltage to directly drive the controlled proportional valve.

[0014] In the present invention, the detection signal of the controlled proportional valve is a current signal or a displacement signal; the detection signal is subjected to mean filtering to filter out the vibration part to obtain a basic detection signal;

[0015] When the controlled proportional valve does not have a valve core displacement detection function, the detection signal of the controlled proportional valve is a current signal, which is obtained by a current sensor, and the basic detection signal obtained after mean filtering is a driving current without a flutter current;

[0016] When the controlled proportional valve has a valve core displacement detection function, the detection signal of the controlled proportional valve is a valve core displacement signal, which is obtained by a valve core displacement sensor, and the basic detection signal obtained after mean filtering is the current basic displacement of the valve core excluding the flutter displacement.

[0017] The target control signal in step 2) is the target current or target displacement, and the type of the target control signal is the same as the type of the basic detection signal. This target control signal can be a function related to the real-time running time, such as sine, cosine, square wave, triangle wave, or a constant. As a function that changes with time, the target control signal can be directly called, or its real-time value can be directly derived and observed.

[0018] In step 2), the process of obtaining the drive control signal according to the real-time basic detection signal and the target control signal is: subtracting the real-time basic detection signal from the target control signal, and the difference is subjected to closed-loop control operation to obtain the drive control signal. The present invention does not limit the type of closed-loop control operation, which is common knowledge in the art, such as but not limited to PID\LQR\MPC\neural network\ARC, etc., which can generally achieve closed-loop control of current or displacement, and are essentially a correction of real-time current or real-time displacement.

[0019] Preferably, the optimal vibration control signal stored in the database corresponds one-to-one to the controlled proportional valve, and the data is constructed by the following method:

[0020] 2.1) Pressure difference ΔP before and after the current valve j Under this condition, input the target control signal, set the vibration signal amplitude to U, and control the vibration frequency to gradually increase from 0 until the vibration sensor detects the vibration signal. At this moment, the valve core just overcomes the static friction and vibrates. The vibration frequency at this moment is the optimal vibration control signal frequency F i ;

[0021] Then, keep the other current parameters unchanged and gradually reduce the amplitude of the dither control signal until the vibration sensor can no longer detect the dither signal. At this moment, the valve core cannot maintain the dither motion because the amplitude of the dither voltage is too small. The amplitude of the previous dither control signal before the amplitude is reduced is the optimal dither control signal U i Amplitude; So far, the pressure difference before and after the current valve is ΔP j , the optimal flutter control signal frequency F under the target control signal i and amplitude U i Determined and written to the database;

[0022] 2.2) Change the target control signal with the set amplitude, and repeat step 2.1) until the target control signal reaches the maximum allowable value; thereby obtaining the current pressure difference ΔP before and after the valve j Optimal flutter control signal data under any given target control signal;

[0023] 2.3) Then increase the pressure difference by the set value ΔP step Change the pressure difference ΔP before and after the valve j =, and repeat step 2.1) and step 2.2) until the pressure difference reaches the maximum allowable pressure difference; obtain the optimal dither control signal data under any valve front and rear pressure difference and any given target control signal; at this point, the optimal dither control signal database of the proportional valve is established.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The existing proportional valve controller has little effect on improving the hysteresis phenomenon, and the flutter frequency and flutter amplitude cannot be adaptively adjusted as the valve core stroke changes, resulting in the attenuation of the valve core flutter amplitude and instability of the flutter motion. The control method of the present invention obtains the optimal flutter control signal under various working conditions in advance through experiments and builds a database. Based on the database model, the optimal flutter control signal under the current working condition and its corresponding frequency and amplitude are adaptively adjusted and output, and applied to the closed-loop feedback link, which can greatly reduce the hysteresis. Among them, the database model scheme bypasses the complex research on the composite mechanisms of hydraulic force, impact force, damping force, etc., and comprehensively measures the composite influence of the above forces to obtain the optimal flutter type, frequency, and amplitude of the proportional valve under all working conditions.

[0026] 2. When the proportional valve receives the target control instruction, a larger coil current is required to overcome the static friction force that is greater than the dynamic friction force. When the valve core overcomes the static friction force, the friction force it is subjected to suddenly decreases due to the conversion into dynamic friction force. At this time, the coil current is still at a relatively high level, and the valve core will produce a large acceleration, causing the displacement to overshoot. Under the nonlinear flutter control method proposed in the present invention, the valve core will always be in a state of macroscopic stability and microscopic jitter, so the speed of responding to the control signal will be faster, the dead zone and saturation zone of the proportional valve current-displacement curve will be reduced, the linearity will be higher, and the micro-motion performance will be better.

[0027] 3. The nonlinear vibration control method proposed in the present invention is applicable to all electromagnetic proportional slide valves, and can output the best vibration control signal to adapt to proportional valves of different structures, thereby achieving the most ideal vibration effect.

[0028] 4. The integral of the dither control signal proposed in the present invention in the time domain is 0, so its equivalent value is 0, and theoretically no additional energy of the system is consumed.

[0029] 5. The mean filter operation frequency and the dither signal frequency proposed by the present invention are synchronized in real time, ensuring that the filtered signal will not be distorted as the dither frequency changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the ideal current-displacement curve (without hysteresis);

[0031] Figure 2 is the actual current-displacement curve (with hysteresis loop);

[0032] Figure 3 It is a structural schematic diagram of a two-position two-way electromagnetic proportional valve;

[0033] Figure 4 This is the principle diagram of nonlinear flutter control;

[0034] Figure 5 It is a schematic diagram of superposition operation of driving control signal and dither signal in the controller;

[0035] Figure 6 It is a schematic diagram of the valve core flutter motion;

[0036] Figure 7 Schematic diagram of the process for building a database of optimal chatter types, frequencies, and amplitudes;

[0037] Figure 8 Schematic diagram of the experimental current-displacement curve (without flutter);

[0038] Fig. 9 Schematic diagram of the experimental current-displacement curve (with vibration). DETAILED DESCRIPTION

[0039] The present invention is further described and illustrated below in conjunction with specific embodiments. The embodiments are merely exemplary of the present disclosure and do not define the scope of limitation. The technical features of each embodiment of the present invention may be combined accordingly without conflicting with each other.

[0040] The nonlinear flutter control method of the present invention that takes into account the high dynamic, low hysteresis and micro-motion characteristics of the proportional valve is applicable to all proportional slide valves. The following embodiments are described by taking a two-position, two-way electromagnetic proportional valve as an example. The present invention establishes a valve core displacement coordinate system, where the horizontal axis is the axial valve core displacement (positive to the right) and the vertical axis is the radial valve core displacement (positive upward). Figure 3 As shown. In the figure, the valve core displacement coordinate system is relatively static and fixed to the valve body. When the electromagnetic coil is not energized, the valve core position in the figure is defined as the valve core displacement origin, and the piston blocks the oil in the oil inlet from the oil outlet; when the electromagnetic coil is energized, the armature moves to the right under the electromagnetic force of the coil, a gap is generated between the piston and the oil outlet, and the oil inlet and the oil outlet are connected.

[0041] Taking the electromagnetic proportional valve without valve core displacement detection function as an example, for this type of controlled proportional valve, a current sensor is used to obtain the current signal of the valve coil as a detection signal, and the target control signal is also a detection signal. As shown in the figure, the principle of this type of electromagnetic proportional valve nonlinear flutter control system mainly includes: current sensor, mean filter module, controller and power amplifier. Among them, the current sensor is used to obtain the current signal of the proportional valve, the mean filter module processes the current signal to obtain the real-time drive current, the controller is used to output an equivalent control signal containing the drive control signal and the flutter control signal, and the equivalent control signal performs PWM waveform equivalent conversion; the power amplifier converts the control signal into a coil voltage to drive the proportional valve.

[0042] If the controlled proportional valve has a valve core displacement detection function (ie, a valve core displacement sensor), the valve core displacement signal can be directly used as a detection signal, and the target control signal is the displacement signal. Figure 4 The corresponding current sensor is replaced by a displacement sensor, and the valve core displacement signal is filtered to filter out the flutter displacement and obtain the valve core basic displacement.

[0043] The working principle of the system of the present invention is:

[0044] 1) Acquire the detection signal of the controlled proportional valve in real time, filter the real-time detection signal to filter out the chatter signal, and obtain the basic detection signal;

[0045] 2) The controller obtains the current pressure difference ΔP before and after the controlled proportional valve j , external input target control signal and real-time basic detection signal; obtain the drive control signal according to the real-time basic detection signal and the target control signal, and obtain the best flutter control signal under the current conditions from the database according to the current valve front and rear pressure difference and the target control signal; the database pre-stores different valve front and rear pressure differences ΔP of the controlled proportional valve in the current usage scenario j , the frequency and amplitude of the optimal flutter control signal under the target control signal;

[0046] 3) The controller adds the drive control signal and the optimal dither control signal to obtain an equivalent control signal, and then performs PWM waveform equivalent conversion on the equivalent control signal to convert it into a control signal;

[0047] 4) The power amplifier converts the control signal into coil voltage to directly drive the controlled proportional valve.

[0048] like Figure 5As shown, the waveform of the dither control signal can be a square wave, a left vertical triangle wave, a right vertical triangle wave, a sawtooth wave, a sine wave, and many other different waveforms. However, for the same usage scenario (the same load), the optimal waveform of the dither control signal is determined and does not need to be changed. Therefore, before the database of the present invention is constructed, the waveform of the dither control signal in the usage scenario has been determined based on the attempts in the field. When constructing the database, the present invention no longer conducts waveform research, and the constructed dither signals are all the same waveform. In different usage scenarios, the most matching dither waveform can be used according to the actual situation to achieve the best hysteresis improvement effect, but the database needs to be rebuilt. Since the integral of the dither control signal in the time domain is 0, its equivalent value is 0, and theoretically no additional energy is consumed by the system.

[0049] In order to explain the present invention in detail, the electromagnetic proportional valve without valve core displacement detection function (the detection signal and the control signal are both current signals) is taken as an example to describe the control method of the present invention in detail. Under the excitation of the coil voltage, the electromagnetic coil current is composed of two parts: the driving current I0 and the flutter current I chatter As shown in the figure, under the action of the driving current I0, the valve core produces a basic displacement x0, plus the flutter current I chatter The valve core generates a flutter displacement x with an amplitude of A around the displacement x0. chatter In the control system of the present invention, the coil current fed back to the controller must remove the vibration part to ensure the closed-loop stability of the basic displacement x0. In this embodiment, the vibration part is removed by a mean filter. The coil current signal input to the controller after filtering only contains the drive current I0 signal, but not the vibration current I chatter In addition, the mean filter operation frequency F filter Synchronize with the current flutter signal frequency in real time, i.e. F filter =F, to ensure that the filtered signal will not be distorted as the vibration frequency changes. Although the filtering link will cause a certain lag in the signal, the closed-loop operation frequency of most controllers on the market is much greater than the valve core's vibration frequency, and this lag is not enough to affect the control performance of the electromagnetic proportional valve.

[0050] The equivalent conversion rule of the PWM waveform of the equivalent control signal is as follows: In the process of converting the equivalent control signal into the control signal, the controller uses a certain sampling frequency F sample Sample the equivalent control signal. Assume that the sample is taken at time t, and the instantaneous value is E(t). Then the sampled instantaneous value E(t) is normalized to the range [0,1], and the equivalent duty cycle of the control signal is calculated:

[0051]

[0052] Among them, E maxis the maximum value of the equivalent control signal, U is the amplitude of the flutter control signal, and E is the drive control signal.

[0053] The PWM frequency of the control signal is usually tens to hundreds of times the dither frequency, so the control signal after the equivalent control signal is equivalently converted through the PWM waveform can fit the equivalent control signal well.

[0054] The frequency and amplitude of the optimal nonlinear flutter signal output by the control system of the present invention are obtained by searching in a database, and the database pre-stores the frequency and amplitude of the optimal nonlinear flutter signal under different working conditions. The present invention does not limit the method of obtaining the optimal nonlinear flutter signal, and there are several ways to obtain these optimal parameters, including mathematical theoretical modeling, experimental measurement, etc.

[0055] This embodiment of the present invention uses a part of mathematical modeling and full-operating experimental measurement as examples to provide a detailed introduction to the method for obtaining the optimal nonlinear flutter signal. It should be noted that the optimal nonlinear flutter signal acquisition method proposed in this embodiment of the present invention is applicable to all proportional spool valves. Existing studies have shown that there is an optimal range for the flutter frequency and amplitude parameters of the proportional valve spool, which is determined by the structural parameters of the proportional valve.

[0056] The testing principle of the optimal chatter signal database is as follows Figure 7 As shown. At the current pressure difference ΔP before and after the valve j Next (where and is an integer, ΔP max is the maximum pressure difference before and after the valve, ΔP step To test the pressure difference step before and after the valve, ΔP j The system input is the target signal that increases in a certain step size. Taking the current signal as the target signal as an example, the system input is the target signal that increases in a certain step size I step Increased target current I i ,in and is an integer, I max It is the maximum rated current of the proportional valve solenoid coil.

[0057] For proportional valves without valve core displacement detection function, since the coil current also includes the flutter part when the valve core is not in the flutter state, the flutter state of the valve core cannot be judged based on the coil current. In this regard, the present invention uses an additional vibration sensor to judge the critical flutter state of the valve core, specifically, the vibration sensor detects and obtains the flutter signal waveform, and then judges the flutter state based on the waveform characteristics. For valves with valve core displacement detection function, the displacement waveform obtained by the valve core displacement sensor can be directly used to judge the flutter state.

[0058] The optimal vibration control signals stored in the database of the present invention correspond one to one with the controlled proportional valves, and the data is constructed by the following method:

[0059] 2.1) Install a vibration sensor for detecting the chatter signal for the controlled proportional valve (the controlled proportional valve has the function of valve core displacement detection, and the valve core displacement sensor can be used to directly detect the chatter signal). The vibration sensor only needs to be able to detect the chatter signal. The chatter signal is a regular periodic function. The period and amplitude can be determined from the signal, thereby obtaining the chatter frequency and amplitude (whether it is vibrating); at the current pressure difference ΔP before / after the valve j Next, input the target current I i (For proportional valves with valve core displacement detection function, input the target displacement x i ), the amplitude of the flutter signal is set to U, and the flutter frequency is controlled to increase gradually from 0 until the vibration sensor detects the flutter signal. At this moment, the valve core just overcomes the static friction and flutters. The optimal flutter control signal frequency F i It is determined in this way; then keep the other current parameters unchanged and gradually reduce the amplitude of the dither control signal until the vibration sensor can no longer detect the dither signal. At this moment, the valve core is unable to maintain the dither motion because the amplitude of the dither voltage is too small. The amplitude of the previous dither control signal before the amplitude is reduced is the current optimal dither control signal amplitude U i ; So far, at the current pressure difference before and after the valve ΔP j The target current I i (or target displacement x i ) is the frequency F of the optimal flutter control signal under i and amplitude U i Determined and written to the database;

[0060] 2.2) Change the given target current I i '=I i +I step (or target displacement x i '=x i +x step ), repeat step 2.1) until The current pressure difference ΔP before and after the valve is obtained j The optimal vibration control signal data under any given target current (target displacement);

[0061] 2.3) Change the pressure difference ΔP before and after the valve j , ΔP j '=ΔP j +ΔP step , and repeat steps 2.1) and 2.2) until The optimal dither control signal data under any pre-valve / post-valve pressure difference and any target current (or target displacement) are obtained; thus, the optimal dither control signal database of the proportional valve is established.

[0062] After the database is established, enter the required current pressure difference ΔP before and after the valve j The optimal flutter frequency and amplitude required by the proportional valve can be obtained by using the given target current (or target displacement). The experimental results of the nonlinear flutter control method proposed in this invention are as follows: Fig. 9 As shown in the figure, the red curve represents the extension of the valve core, and the blue curve represents the retraction of the valve core. Figure 8 The result without chattering shows that the hysteresis phenomenon has been greatly improved, and the linearity of current-displacement is better. Under the control method of the present invention, the valve core will always be in a state of macroscopic stability and microscopic jitter, so the speed of responding to the control signal will be faster, and the dead zone and saturation zone of the proportional valve current-displacement curve will be reduced and the linearity will be higher.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. For ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A nonlinear flutter control method taking into account high dynamic, low hysteresis and micro-motion characteristics of a proportional valve, characterized in that: The steps include: 1) Acquire the detection signal of the controlled proportional valve in real time, perform mean filtering on the real-time detection signal to filter out the chatter signal, and obtain the basic detection signal; 2) The controller obtains the current pressure difference ΔP before and after the controlled proportional valve j , external input target control signal and real-time basic detection signal; The drive control signal is obtained according to the real-time basic detection signal and the target control signal, and the optimal flutter control signal under the current conditions is obtained from the database according to the current valve front and rear pressure difference and the target control signal; the database pre-stores different valve front and rear pressure differences ΔP of the controlled proportional valve in the current use scenario. j , the frequency and amplitude of the optimal flutter control signal under the target control signal; 3) The controller adds the drive control signal and the optimal dither control signal to obtain an equivalent control signal, and then performs PWM waveform equivalent conversion on the equivalent control signal to convert it into a control signal; 4) The power amplifier converts the control signal into coil voltage to directly drive the controlled proportional valve.

2. The control method according to claim 1, characterized in that: In step 1), the detection signal of the controlled proportional valve is a current signal or a displacement signal; the detection signal is subjected to mean filtering to filter out the vibration part to obtain a basic detection signal; When the controlled proportional valve does not have a valve core displacement detection function, the detection signal of the controlled proportional valve is a current signal, which is obtained by a current sensor, and the basic detection signal obtained after mean filtering is a driving current without a flutter current; When the controlled proportional valve has a valve core displacement detection function, the detection signal of the controlled proportional valve is a valve core displacement signal, which is obtained by a valve core displacement sensor, and the basic detection signal obtained after mean filtering is the current basic displacement of the valve core excluding the flutter displacement.

3. The control method according to claim 2, characterized in that: The operation frequency F of the mean filter filter Synchronize with the current flutter signal frequency F in real time, that is, F filter =F to ensure that the filtered signal will not be distorted as the frequency of the vibration signal changes.

4. The control method according to claim 1, characterized in that: In step 2), the pressure difference before and after the valve is ΔP j Obtained through a pressure sensor; the external input target control signal is a target current or a target displacement, and the type of the target control signal is the same as the type of the basic detection signal.

5. The control method according to claim 1, characterized in that: In step 2), the process of obtaining the drive control signal based on the real-time basic detection signal and the target control signal is: subtracting the real-time basic detection signal from the target control signal, and the difference is subjected to current closed-loop control or displacement closed-loop operation to obtain the drive control signal.

6. The control method according to claim 1, characterized in that: The dither type of the optimal dither control signal is pre-set according to the use scenario of the controlled proportional valve. Once the use scenario is determined, the dither type is determined. The dither type does not change with the pressure difference ΔP before and after the valve. j and target control signal.

7. The control method according to claim 1 or 6, characterized in that: The optimal vibration control signals stored in the database correspond one to one with the controlled proportional valves, and the data is constructed by the following method: 2.1) Pressure difference ΔP before and after the current valve j Under this condition, input the target control signal, set the vibration signal amplitude to U, and control the vibration frequency to gradually increase from 0 until the vibration sensor detects the vibration signal. At this moment, the valve core just overcomes the static friction and vibrates. The vibration frequency at this moment is the optimal vibration control signal frequency F i ; Then, keep the other current parameters unchanged and gradually reduce the amplitude of the dither control signal until the vibration sensor can no longer detect the dither signal. At this moment, the valve core cannot maintain the dither motion because the amplitude of the dither voltage is too small. The amplitude of the previous dither control signal before the amplitude is reduced is the optimal dither control signal U i Amplitude; So far, the pressure difference before and after the current valve is ΔP j , the optimal flutter control signal frequency F under the target control signal i and amplitude U i Determined and written to the database; 2.2) Change the target control signal with the set amplitude, and repeat step 2.1) until the target control signal reaches the maximum allowable value; thereby obtaining the current pressure difference ΔP before and after the valve j Optimal flutter control signal data under any given target control signal; 2.3) Then increase the pressure difference by the set value ΔP step Change the pressure difference ΔP before and after the valve j =, and repeat step 2.1) and step 2.2) until the pressure difference reaches the maximum allowable pressure difference; obtain the optimal dither control signal data under any valve front and rear pressure difference and any given target control signal; at this point, the optimal dither control signal database of the proportional valve is established.

8. The control method according to claim 7, characterized in that: When the controlled proportional valve does not have a valve core displacement detection function, a vibration sensor for detecting a chatter signal is installed on the controlled proportional valve, and the target control signal is a target current; the target current initially selects the minimum allowable value and gradually increases in step 2.2); When the controlled proportional valve has the valve core displacement detection function, a built-in valve core displacement sensor is used to obtain a flutter signal or a vibration sensor is installed for the controlled proportional valve to obtain a flutter signal. The target control signal is the valve core target displacement. The valve core target displacement initially selects the minimum allowable value and is gradually increased in step 2.2).

9. The control method according to claim 1, characterized in that: In step 3), the equivalent control signal is converted into a PWM waveform equivalently, specifically: The controller uses the set sampling frequency F sample The equivalent control signal is sampled; assuming that the sampling is performed at time t, the instantaneous value is E(t); then the sampled instantaneous value E(t) is normalized to the range of [0,1], and the equivalent duty cycle of the control signal is calculated: Among them, E max is the maximum value of the equivalent control signal, U is the amplitude of the flutter control signal, and E is the drive control signal; The controller can generate a control signal according to the equivalent duty cycle.

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