A PWM-based high-speed switching valve hysteresis compensation control method

Abstract

This invention proposes a hysteresis compensation control method for high-speed switching valves based on PWM, belonging to the field of high-speed switching valve control. Its key feature is that the working cycle of the high-speed switching valve is divided into four stages. The rising and falling edges of the reference PWM control the opening and closing times of the high-speed switching valve, while the loading signal consists of on-compensation PWM, excitation PWM, opening-hold PWM, and closing compensation PWM. By varying the pressure before the valve, the critical voltage values ​​for opening and closing the valve core are obtained, thereby controlling the amplitudes of the on-compensation PWM and opening-hold PWM to reduce the hysteresis time and current consumption of the valve core response. The duty cycle of the excitation PWM is determined by the derivative of the pressure before the valve, and the duty cycles of the on-compensation PWM and closing compensation PWM are obtained based on the coil current, accelerating the valve core response speed and optimizing current consumption. This invention can improve the response speed of high-speed switching valves, reduce energy consumption, and expand the frequency response range, offering advantages such as high response, low power consumption, low cost, and small footprint.

Description

Technical Field

[0001] This invention relates to the field of high-speed switching valve control, and more particularly to a hysteresis compensation control method for high-speed switching valves based on PWM. Background Technology

[0002] High-speed switching valves operate fully open or fully closed, offering advantages such as low pressure loss, low energy consumption, and strong resistance to contamination. Through pulse width modulation (PWM), digital signals can be directly converted into flow signals. However, due to the inductance and inertia of the electromagnet and the valve itself, the valve cannot move immediately upon receiving a control signal, lagging behind the signal. The dynamic characteristics of high-speed switching valves are a key factor in evaluating their performance and determining the control accuracy of valve control systems, and the hysteresis characteristic of high-speed switching valves significantly affects their dynamic characteristics.

[0003] Among existing technologies for improving the response speed of high-speed switching valves, pre-excitation control strategies are relatively simple and easy to implement. Generally, a signal is pre-loaded to bring the valve core current close to the critical switching value, thereby reducing the opening and closing lag time of the high-speed switching valve. Chinese patent application CN113898778B discloses a high-speed solenoid valve control system and method that adapts to changes in operating conditions and control parameters. It uses current and maximum pressure feedback to improve the dynamic characteristics of the high-speed switching valve, reduces the impact of the system's maximum pressure on dynamic characteristics, reduces the valve core response lag time, and improves energy conversion efficiency. The pre-excitation method loads a control signal based on the maximum pressure after the valve core opens, ensuring that the valve core does not close during the open-hold phase. This improves the valve core's dynamic performance to a certain extent without significantly increasing the system's complexity or space requirements.

[0004] However, after the valve core opens, the pressure in front of the valve will drop, and the current value required to maintain the maximum opening will also decrease. As a result, the current value generated by the control signal applied based on the highest pressure will be greater than the actual required current value, resulting in excess energy consumption. Moreover, during the valve core closing phase, the current value higher than the actual required current value will also lead to a longer valve core lag time. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a hysteresis compensation control method for high-speed switching valves based on PWM. This method, based on the hysteresis characteristics of high-speed switching valves during switching and combined with the changes in inlet pressure during valve operation, minimizes the opening and closing hysteresis time and operating current of high-speed switching valves, improves dynamic characteristics, reduces energy consumption, and broadens the frequency range of valve core response.

[0006] The detailed technical solution of this invention is as follows:

[0007] A PWM-based hysteresis compensation control method for high-speed switching valves is characterized by dividing the valve's operating cycle into four stages: an opening compensation stage, a valve core opening stage, an opening holding stage, and a closing compensation stage. The opening and closing times of the high-speed switching valve are controlled by a reference PWM signal. During the valve's response period, opening compensation PWM, excitation PWM, opening holding PWM, and closing compensation PWM are introduced. First, the opening compensation PWM ensures the coil current reaches the critical opening current value of the valve core, reducing the valve core opening delay time. The amplitudes of the opening compensation and opening holding PWM signals are determined in real-time based on the upstream pressure, reducing unnecessary current consumption. The valve core motion state is determined by the derivative of the upstream pressure, correcting the duty cycle of the excitation PWM. The duty cycle of the closing compensation PWM is determined by detecting the duration for the current to drop to 0 during the valve core closing stage, ensuring that the current does not increase in the opposite direction, thus extending the valve core motion time and reducing current consumption.

[0008] The frequency of the reference PWM and duty cycle Used to control the opening and closing times of high-speed switching valves, determining the opening duration of the valve core within one cycle, thereby controlling the flow rate at the outlet of the high-speed switching valve.

[0009] The enabled compensation PWM frequency Equal to the reference PWM frequency, its variable amplitude U1 is obtained from the inlet pressure of the valve, and the duty cycle is... The initial value and the cycle value are used to control the loading time of the amplitude signal, so that the coil current reaches the critical opening value when the rising edge of the reference PWM arrives, thereby reducing the valve core opening delay time.

[0010] The frequency of the excitation PWM The frequency is equal to the reference PWM frequency, the amplitude is the rated voltage value of the high-speed switching valve, and the duty cycle is... The initial value and the cycle value are used to control the rapid rise of the current, reduce the valve core opening movement time, and make the valve core open and in the fully open state.

[0011] The opening maintains the PWM frequency. The frequency is equal to the reference PWM frequency, and the amplitude varies with the inlet pressure value, with a duty cycle of [missing information]. Reference PWM duty cycle With the excitation PWM duty cycle The difference is used to minimize the current value when the valve core is always in the fully open state, while reducing the valve core closing delay time.

[0012] The frequency of disabling compensation PWM Equal to the reference PWM frequency, amplitude equal to the maximum negative rated voltage, duty cycle This corresponds to the time it takes for the current to drop to zero. It is used to control the rapid decrease of the coil current, reducing the valve core's closing time.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The proposed high-speed switching valve hysteresis compensation control method based on PWM compensates the current signal in advance before the valve core opens, thereby reducing the valve core opening delay time.

[0015] During the fully open phase of the valve core, the opening is determined by combining the actual pressure before the valve to maintain the PWM amplitude. Compared with using the highest system pressure to apply the amplitude, this further reduces the current and decreases the valve core closing delay time and excess current energy consumption.

[0016] By disabling the negative value signal of the compensation PWM load, the influence of coil residual magnetism is reduced, and its duty cycle, based on current feedback, will not cause the coil current value to increase in the opposite direction, thus shortening the valve core closing movement time. At the same time, there is no excess current, reducing energy consumption.

[0017] By reducing the lag time of valve core movement through hysteresis compensation control, the valve core response speed is improved, and the frequency response range of the valve core is expanded. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the hysteresis compensation control principle in an embodiment of the present invention.

[0019] Figure 2 This is a diagram showing the relationship between the valve inlet pressure derivative and the valve core displacement in an embodiment of the present invention.

[0020] Figure 3 This is a diagram of the hysteresis compensation control drive signal in an embodiment of the present invention.

[0021] Figure 4 This is a dynamic response diagram of the hysteresis compensation control valve core in an embodiment of the present invention.

[0022] Figure 5 This is a comparison chart of valve core displacement response under independent PWM control, adaptive operating condition control, and hysteresis compensation control.

[0023] Figure 6 This is a comparison chart of the coil current response of independent PWM control, adaptive operating condition control, and hysteresis compensation control.

[0024] Figure 7 This is a comparison chart of current energy consumption for independent PWM control, adaptive operating condition control, and hysteresis compensation control.

[0025] Figure 8 This is the displacement response diagram of the valve core under independent PWM control.

[0026] Figure 9 This is the displacement response diagram of the 100Hz hysteresis compensation control valve core. Detailed Implementation

[0027] The technical solution of the present invention will be fully described below with reference to the embodiments and accompanying drawings.

[0028] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. All other embodiments obtained by one of ordinary skill in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The numerical values ​​appearing are also only preferred values ​​for describing particular embodiments.

[0030] like Figure 1 As shown, this embodiment of the invention provides a PWM-based hysteresis compensation control method for high-speed switching valves. The method is characterized by dividing the working cycle of the high-speed switching valve into four stages: an opening compensation stage, a valve core opening stage, an opening holding stage, and a closing compensation stage. The opening and closing times of the high-speed switching valve are controlled by a reference PWM signal, and opening compensation PWM, excitation PWM, opening holding PWM, and closing compensation PWM are introduced during the high-speed switching valve response period.

[0031] The duty cycle of the excitation PWM and the compensation PWM is related to the feedback of the valve core movement process. The duty cycle of the compensation PWM and the holding PWM is related to the excitation PWM and the compensation PWM. Therefore, before the valve core completes a complete opening and closing movement, it is necessary to specify the initial duty cycle value for each PWM to ensure that the valve core moves normally.

[0032] Before the rising edge of the reference PWM arrives, an on-start compensation PWM with amplitude varying with the inlet pressure is applied, causing the coil current to rise to near the critical opening current of the valve spool. This reduces the time it takes for the current to rise from 0 to the critical opening current of the valve spool when the on-start signal arrives. To ensure the valve spool does not open prematurely, a coefficient is needed to correct the amplitude U1 of the on-start compensation PWM. When the coefficient is 0.95, the valve spool does not open prematurely, and the amplitude of the on-start compensation PWM is [value missing]. In the formula This refers to the number of coil turns. The length of the magnetic core's magnetic circuit; The leakage flux coefficient; Relative permeability; This is the initial air gap length; The magnetic permeability of the magnetic core; This is the effective cross-sectional area of ​​the armature; The vacuum permeability; This is the equivalent resistance of the coil; This refers to the pressure before the valve. This represents the effective working area of ​​the pressurized oil. The initial duty cycle value for the first cycle of the compensated PWM is... The initial duty cycle value for the second cycle of the compensated PWM is ; .

[0033] When the valve core opening signal, i.e., the rising edge of the reference PWM, arrives, an excitation PWM with an amplitude of U2 = 24V is applied, causing the current to rise rapidly and open the valve core. The first cycle of the excitation PWM needs to ensure the valve core is fully open; therefore, the initial duty cycle value for the first cycle of the excitation PWM is set to... .

[0034] like Figure 2 The diagram shows the relationship between the derivative of the inlet pressure and the valve core displacement. When the valve core moves from the closed state to the fully open state, a PWM (Positioning Mode and Control) is applied to maintain the opening. Since it's difficult to install a displacement sensor inside a high-speed switching valve, the change in inlet pressure is used to determine the valve core's position. When the derivative of the inlet pressure is less than zero, it indicates that the valve core is open. The time t2 from the rising edge of the reference PWM to the inlet pressure derivative becoming less than zero is calculated. To ensure that the valve core is fully open when the amplitude of the excitation PWM is 0, a coefficient is needed to correct it. When the coefficient is 2, the valve core reaches the fully open state exactly when the amplitude of the excitation PWM is 0. Therefore, we have... .

[0035] When the valve core is fully open, in order to ensure that the valve core opens normally while keeping the current as small as possible, the opening amplitude U3 is kept in PWM mode as the inlet pressure changes with the valve. A correction factor of 1.05 is taken, then... In the formula This refers to the number of coil turns. The length of the magnetic core's magnetic circuit; The leakage flux coefficient; Relative permeability; This is the initial air gap length; The magnetic permeability of the magnetic core; This is the effective cross-sectional area of ​​the armature; The vacuum permeability; This is the equivalent resistance of the coil; This refers to the pressure before the valve. The effective working area of ​​the pressurized oil; This represents the maximum displacement of the valve core. The opening maintains the initial duty cycle value of the first cycle of the PWM. The duty cycle of the PWM remains constant in subsequent cycles. .

[0036] When the valve core close signal, i.e., the falling edge of the reference PWM, arrives, the coil current needs to decrease rapidly to ensure the valve core closes quickly. A shutdown compensation PWM with an amplitude of U4 = -24V is applied to reduce the influence of the inductance and allow the coil current to unload quickly. However, an excessively large or small duty cycle of the shutdown compensation PWM will affect the valve core's closing time. An excessively large duty cycle will cause the current to increase in the opposite direction after dropping to zero, thus increasing the electromagnetic force again; an excessively small duty cycle will prevent the current from quickly dropping to zero. Therefore, to ensure the coil current drops to zero in the first cycle, facilitates the calculation of the duty cycle for subsequent cycles of the shutdown compensation PWM, and prevents the valve core from opening again, the initial value of the duty cycle for the first cycle of the shutdown compensation PWM is taken. By acquiring the coil current value through a current sensor and calculating the time t4 from the falling edge of the reference PWM to the coil current dropping to zero, the duty cycle for shutting off the subsequent cycles of the compensation PWM can be determined. .

[0037] Based on the relationship between voltage and current, the time required for the current to rise to the critical turn-on current value is: In the formula: For coil inductance; The initial current of the coil; This is the equivalent resistance of the coil; This is the critical start-up current value. Based on the current sensor, the time it takes for the current to drop to 0 is 0.0028 seconds, meaning the loading time for compensation to be off is 0.0028 seconds. The time it takes for the current to rise to its maximum value when voltage U1 is applied is 0.0246 seconds. To ensure the current value remains low at all times, based on a frequency of 10Hz, the duration for the base PWM amplitude to be 0 with a duty cycle of 0.5 is 0.05 seconds. Therefore, the amplitude of the compensation PWM needs to become 0 within 0.0226 seconds after compensation is off. 0.0226 / 0.0028 = 8.07. To allow the current to rise to its maximum value, the coefficient is rounded down to 8. Therefore, the duty cycle of the subsequent cycles of the compensation PWM is... .

[0038] The pressure before the valve gradually rises from 0 to the set maximum pressure value. Therefore, when the reference PWM is directly applied at time 0, the hydraulic pressure overcome is 0, which cannot reflect the actual dynamic response of the valve core at the maximum working pressure. Thus, the reference PWM needs to be delayed for a period of time to ensure that the pressure before the valve rises to the maximum value, which better reflects the actual operating conditions. The delay time of the reference PWM is... .

[0039] No delay is needed for the first cycle of enabling the compensated PWM. Since the frequency of enabling the compensated PWM is the same as that of the reference PWM, a delay is required in the second cycle of enabling the compensated PWM to turn off for the duration corresponding to the initial value of the duty cycle. The delay for enabling compensated PWM in subsequent cycles is... .

[0040] The excitation PWM is applied at the rising edge of the reference PWM, therefore the delay of the excitation PWM is the same as the delay of the reference PWM. The span-and-hold PWM is applied after the excitation PWM, and the span-and-hold frequency is consistent with the reference PWM; therefore, the delay of the span-and-hold PWM in the first cycle is [missing information]. The delay of subsequent cycles is .

[0041] The compensated PWM is disabled and applied at the falling edge of the reference PWM. In subsequent cycles, the duty cycle of the disabled PWM is related to the current fall time of the previous cycle and the falling edge of the reference PWM. The duty cycle output is zero before the current fall time of the previous cycle is obtained. Therefore, only the delay time of the initial value for the first cycle needs to be set. No delay is needed in subsequent cycles.

[0042] like Figure 3 The image shows the drive signal for the PWM-based high-speed switching valve hysteresis compensation control method.

[0043] The following experiments will be conducted in a simulation environment using specific examples:

[0044] The following parameters were used to model the system in the simulation: a two-position three-way high-speed normally closed cartridge valve was taken as the research object, with the following specific parameters: steel ball diameter 3.2mm, valve stem diameter 1.2mm, valve core stroke 0.5mm, valve port diameter 2.2mm, moving part mass 15.1g, coil turns 900, coil internal resistance 10.2Ω, leakage magnetic coefficient 1.6, initial air gap length 0.6mm, armature diameter 7.5mm, armature length 22mm, pump flow rate 8L / min, reference PWM frequency 10Hz, duty cycle 0.5, amplitude 24, and relief valve pressure 6MPa.

[0045] The control effect is as follows:

[0046] Figure 4 The dynamic response diagram of the hysteresis compensation control valve core is shown. The results show that, except for the first cycle with the initial value of the duty cycle, the valve core displacement closely matches the ideal displacement in subsequent cycles. Before the valve core opens, the coil current rises first and then rises rapidly to open the valve core. After the valve core opens, the current drops and then drops to 0.

[0047] Figure 5The diagram shows a comparison of valve core displacement response under independent PWM control, adaptive operating condition control, and hysteresis compensation control. The left diagram compares the valve core open state, and the right diagram compares the valve core closed state. Since this invention considers the changes in inlet pressure during operation, it is compared with a high-speed solenoid valve control system and method for adapting to changes in operating conditions and control parameters disclosed in CN113898778B. The results show that the overall valve core hysteresis time is 6.4ms for adaptive operating condition control, 26ms for independent PWM control, and 5.7ms for hysteresis compensation control, which is an improvement of 10.9% compared to adaptive operating condition control and 78.1% compared to independent PWM control.

[0048] Figure 6 The graph shows a comparison of the coil current response of independent PWM control, adaptive operating condition control, and hysteresis compensation control. The results show that during the opening and holding phase, the hysteresis compensation control is significantly lower than the independent PWM control. Since the pressure in front of the valve gradually decreases after the valve core opens, the current of the hysteresis compensation control during the opening and holding phase is also slightly smaller than that of the adaptive operating condition control.

[0049] Figure 7 This is a comparison chart of current energy consumption for independent PWM control, adaptive operating condition control, and hysteresis compensation control. The energy consumed in 20 seconds is 242.9W for adaptive operating condition control, 494.8W for independent PWM control, and 174.8W for hysteresis compensation control. Compared with adaptive operating condition control, energy consumption is reduced by 28%, and compared with independent PWM control, energy consumption is reduced by 64.7%. It can be seen that hysteresis compensation control achieves low energy consumption.

[0050] Keeping the duty cycle constant at 0.5, change the frequency of the PWM signal to test the frequency response range of the valve core displacement, such as... Figure 8 The figure shows the valve core displacement response curves under independent PWM control at different reference PWM frequencies. The results show that the valve core cannot close properly when the frequency exceeds 30Hz under independent PWM control. Figure 9 The figure shows the valve core displacement response curve with a reference PWM frequency of 100Hz under hysteresis compensation control. The results show that the valve core can still close normally at a frequency of 100Hz under hysteresis compensation control. Compared with independent PWM control, the frequency response range of the valve core is improved by 70%.

[0051] As can be seen from the above results, the PWM-based high-speed switching valve hysteresis compensation control method proposed in this invention can effectively reduce the power loss of the coil and the overall hysteresis time of valve core opening and closing.

[0052] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. The scope of protection of the present invention is determined by the claims.

Claims

1. A hysteresis compensation control method for high-speed switching valves based on PWM, characterized in that: The working cycle of the high-speed switching valve is divided into four stages: opening compensation stage, valve core opening stage, opening holding stage, and closing compensation stage. The opening and closing times of the high-speed switching valve are controlled by a reference PWM signal. During the response period of the high-speed switching valve, opening compensation PWM, excitation PWM, opening holding PWM, and closing compensation PWM are introduced. First, the opening compensation PWM is used to make the coil current reach the critical opening current value of the valve core, reducing the valve core opening delay time. The amplitude of the opening compensation and opening holding PWM signals is determined in real time by combining the upstream pressure, reducing unnecessary current energy consumption. The valve core motion state is determined by the derivative of the upstream pressure, and the duty cycle of the excitation PWM is corrected. The duty cycle of the closing compensation PWM is determined by detecting the time when the current drops to 0 during the valve core closing stage, ensuring that the current does not increase in the opposite direction, which would prolong the valve core motion time, while reducing current energy consumption. Reference PWM frequency and duty cycle Used to control the opening and closing times of high-speed switching valves, determine the opening duration of the valve core within one cycle, and thus control the flow rate at the outlet of the high-speed switching valve. Enable compensated PWM frequency Equal to the reference PWM frequency, its variable amplitude U1 is obtained from the inlet pressure of the valve, and the duty cycle is... The initial value and the loop value are used to control the loading time of the amplitude signal, so that the coil current reaches the critical opening value when the rising edge of the reference PWM arrives, thereby reducing the valve core opening delay time. Frequency of PWM excitation The frequency is equal to the reference PWM frequency, the amplitude is the rated voltage value of the high-speed switching valve, and the duty cycle is... The initial value and the cycle value are used to control the rapid rise of the current, reduce the valve core opening movement time, and make the valve core open and in the fully open state. Open-circuit PWM frequency The frequency is equal to the reference PWM frequency, and the amplitude varies with the inlet pressure value, with a duty cycle of [missing information]. Reference PWM duty cycle With the excitation PWM duty cycle The difference is used to minimize the current value when the valve core is always in the fully open state, and at the same time reduce the valve core closing delay time. Frequency of off compensation PWM Equal to the reference PWM frequency, amplitude equal to the maximum negative rated voltage, duty cycle The duration of time it takes for the current to drop to zero; used to control the rapid decrease of the coil current and reduce the valve core closing time.

2. The PWM-based high-speed switching valve hysteresis compensation control method according to claim 1, characterized in that: During the fully open phase of the valve core, the opening is determined by combining the actual pressure before the valve to maintain the PWM amplitude. Compared with using the highest system pressure to apply the amplitude, this further reduces the current and decreases the valve core closing delay time and excess current energy consumption.

3. The PWM-based high-speed switching valve hysteresis compensation control method according to claim 1, characterized in that: By disabling the negative value signal of the compensation PWM load, the influence of coil residual magnetism is reduced, and its duty cycle, based on current feedback, will not cause the coil current value to increase in the opposite direction, thus shortening the valve core closing movement time. At the same time, there is no excess current, reducing energy consumption.

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