A control method for a proportional solenoid valve for a hydraulic retarder

Abstract

This invention discloses a control method for a proportional solenoid valve used in a hydraulic retarder, mainly addressing the technical problems of existing control methods, such as long pressure response time, large overshoot, and poor tracking performance. The control method includes: periodically acquiring the feedback pressure of the hydraulic retarder's working chamber and the input signal of the proportional solenoid valve; determining the current target pressure request state and calculating the current target current of the proportional solenoid valve based on the determination result; calculating the current duty cycle of the proportional solenoid valve; finally, superimposing chatter and outputting the final duty cycle, thereby achieving control of the proportional solenoid valve used in the hydraulic retarder. This control method can achieve precise control of the proportional solenoid valve and has the advantages of short response time, small overshoot, and good tracking performance.

Description

Technical Field

[0001] This invention relates to vehicle electronic control methods, specifically to a control method for a proportional solenoid valve used in a hydraulic retarder. Background Technology

[0002] A hydraulic retarder is an auxiliary braking device, typically installed on the driveshaft of heavy-duty vehicles. It mainly consists of a stator, rotor, working chamber, oil filling and discharging mechanism, and cooling system. The working principle of the hydraulic retarder is that the rotor rotates with the driveshaft. During operation, under the action of an external control system, compressed air enters above the oil tank, causing oil to enter the upper end of the stator through the oil inlet pipe, and then into the closed working chamber formed by the rotor and stator. Driven by the rotor blades, the oil circulates and impacts the stator blades, changing the momentum and generating a braking torque that hinders the rotation of the rotor impeller, thereby reducing the speed of the driveshaft and slowing down the vehicle. During deceleration, the proportional solenoid valve on the hydraulic retarder allows for precise control of the compressed air pressure in the working chamber, thus enabling precise control of the braking torque of the hydraulic retarder to adapt to different operating conditions.

[0003] Traditional proportional solenoid valve control methods mainly employ current-based PID control. For example, Chinese invention patent CN108980441 A discloses a PWM-based proportional solenoid valve driving method. This method obtains the impedance value R of the proportional solenoid valve, detects the driving voltage P applied to the proportional solenoid valve, and detects whether the target current changes, thereby estimating the duty cycle. The controller then outputs a PWM signal to the proportional solenoid valve with the estimated duty cycle. Simultaneously, it detects the actual current flowing through the proportional solenoid valve and compares it with the target current, using closed-loop control to adjust the duty cycle until the difference between the actual current and the target current is less than or equal to the error value. This control method eliminates most of the rise time, achieving rapid control and significantly shortening the target current adjustment time. However, due to the low rigidity of gas, there is a significant lag in control for the gas pressure in the working chamber. Existing PID control methods have long pressure response times, large overshoot, and poor tracking performance, thus failing to meet the system's control requirements. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of existing control methods, such as long pressure response time, large overshoot, and poor tracking performance, and to provide a control method for a proportional solenoid valve for a hydraulic retarder.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0006] A control method for a proportional solenoid valve in a hydraulic retarder, characterized by the following steps:

[0007] Step 1: Periodically collect the feedback pressure in the working chamber of the hydraulic retarder and the input signal of the proportional solenoid valve; the input signal includes the feedback current and the system voltage;

[0008] Step 2: Based on the target pressure in the working chamber of the hydraulic retarder and the feedback pressure collected in Step 1, determine the current target pressure request status. If the current target pressure is greater than the feedback pressure, the current target pressure request status is positive. Further determine whether it has entered the overshoot state. If it has entered the overshoot state, proceed to Step 3. If it has not entered the overshoot state, proceed to Step 4.

[0009] If the current target pressure is less than the feedback pressure, the current target pressure request status is return, and step 4 is executed;

[0010] If the current target pressure is equal to the feedback pressure, then the current target pressure request state is to maintain the existing state, and the current target current of the proportional solenoid valve is the current feedback current. At this time, step 5 is executed.

[0011] Step 3: Calculate the overshoot current under overshoot conditions, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve.

[0012] Step 4: Calculate the current offset value in the forward non-overshoot state or the return state, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve.

[0013] Step 5: Based on the current target current of the proportional solenoid valve obtained in Step 2, Step 3, or Step 4, and combined with the feedback current and system voltage collected in Step 1, calculate the current duty cycle of the proportional solenoid valve.

[0014] Step 6: Based on the current duty cycle obtained in Step 5, add flutter and output the final duty cycle to realize the control of the proportional solenoid valve of the hydraulic retarder.

[0015] Furthermore, in step 1, the feedback pressure and feedback current need to be subjected to mean filtering, and the filtering window is the flutter period divided by the sampling period.

[0016] Furthermore, the flutter period is 50ms to 150ms; the sampling period is 1ms to 10ms.

[0017] Furthermore, in step 2, the method for determining whether an overshoot state has been entered is:

[0018] If the difference between the current target pressure and the feedback pressure is greater than the set overshoot threshold, it indicates that the overshoot state has been entered, and the overshoot state will be exited when the difference between the target pressure and the feedback pressure is less than the set steady-state threshold; the overshoot threshold is greater than the steady-state threshold.

[0019] If the difference between the current target pressure and the feedback pressure is less than or equal to the set overshoot threshold, it means that the overshoot state has not been entered.

[0020] Further, in step 3, the current target current of the proportional solenoid valve is calculated using the following formula:

[0021] TargetCurrent=CurrentBase+OverloadCurrent

[0022] In the formula, TargetCurrent is the current target current of the proportional solenoid valve; CurrentBase represents the feedforward current of the proportional solenoid valve, the value of which can be obtained directly by looking up the interpolation table based on the target pressure; OverloadCurrent represents the current overshoot current, the value of which can be obtained directly by looking up the interpolation table based on the target pressure and the difference between the target pressure and the feedback pressure.

[0023] Furthermore, in step 4, the current target current of the proportional solenoid valve, TargetCurrent, is calculated using the following formula:

[0024] TargetCurrent=CurrentBase+CurrentOffset

[0025] In the formula, CurrentBase represents the feedforward current of the proportional solenoid valve, the value of which is obtained directly from the target pressure by consulting the interpolation table; CurrentOffset represents the current offset value in the non-overshoot state or the return state, and its calculation formula is as follows:

[0026]

[0027] In the formula, Kp is the proportionality coefficient; Ki is the integral coefficient; Err p Let Err be the difference between the target pressure and the feedback pressure. p = targetPress - actualPress, where targetPress is the target pressure and actualPress is the feedback pressure.

[0028] Furthermore, in step 5, the current duty cycle TargetDuty of the proportional solenoid valve... (n) Calculated using the following formula:

[0029] TargetDuty (n) =DutyBase + DutyOffset (n)

[0030] Where DutyBase represents the feedforward duty cycle, which is directly obtained from the current target current and system voltage of the proportional solenoid valve; DutyOffset (n) This indicates the current duty cycle offset, and

[0031] DutyOffset (n) =Kp * Err i(n) +∑Ki*Err i(n) +Kd*(Err i(n) -Err i(n-1) )

[0032] In the formula, Kp is the proportionality coefficient; Ki is the integral coefficient; Kd is the differential coefficient; Err i(n) It is the difference between the current target current and the feedback current; Err i(n-1) It is the difference between the target current and the feedback current in the previous cycle; n represents the sampling cycle number.

[0033] Furthermore, in step 6, the final duty cycle is... (n) Calculated using the following formula:

[0034] Duty (n) =TargetDuty (n) +Amplitude×f(t)

[0035] In the formula, Amplitude is the flutter amplitude; f(t) is a periodic function with time as the independent variable, specifically a triangular wave or sine wave with the flutter period as the period, and a number of points are uniformly taken as sampling points in each period of the waveform.

[0036] Furthermore, the number of sampling points Where T1 represents the flutter period and T2 represents the sampling period.

[0037] Furthermore, the number of sampling points is even.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. This invention provides a control method for a proportional solenoid valve used in a hydraulic retarder. This method is based on periodically collected feedback pressure from the hydraulic retarder's working chamber and the input signal from the proportional solenoid valve. By accurately determining the current pressure request state, it precisely calculates the current duty cycle of the proportional solenoid valve, and then superimposes chatter to output the final duty cycle, ultimately achieving precise control of the proportional solenoid valve. This method meets system control requirements and has the advantages of short response time, small overshoot, and good tracking performance.

[0040] 2. The control method for a proportional solenoid valve for a hydraulic retarder provided by the present invention incorporates chatter, which can reduce the influence of hysteresis and friction on the performance of the proportional solenoid valve, thereby improving control accuracy. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0043] like Figure 1 As shown, this embodiment provides a control method for a proportional solenoid valve used in a hydraulic retarder. Taking a controller of a hydraulic retarder as an example, the purpose of this controller is to control the pressure value of the gas in the working chamber of the hydraulic retarder, with the target pressure varying within the range of 0 to 3.5 Bar. The specific control method includes the following steps:

[0044] Step 1: Periodically collect the feedback pressure in the working chamber of the hydraulic retarder and the input signal of the proportional solenoid valve. In this embodiment, the input signals include the feedback current and system voltage. The feedback pressure and feedback current need to be averaged and filtered. The filtering window is the dither period T1 divided by the sampling period T2. The dither period T1 and sampling period T2 are preset according to control requirements. In this embodiment, the dither period T1 is 50ms to 150ms; the sampling period T2 is 1ms to 10ms.

[0045] It should be noted that, in order to prevent the "stickiness" effect, this embodiment increases the chatter period to achieve the chatter function. Due to the influence of the chatter function, the control period of the current feedback control should be the chatter period to avoid the influence of chatter on the feedback current.

[0046] Step 2: Based on the target pressure in the hydraulic retarder's working chamber and the feedback pressure collected in Step 1, determine the current target pressure request status:

[0047] (1) When the target pressure changes, if the current target pressure is greater than the feedback pressure, the current target pressure request state is positive, and it is further determined whether it has entered the overshoot state. If it has entered the overshoot state, step 3 is executed; if it has not entered the overshoot state, step 4 is executed; specifically:

[0048] If the difference between the current target pressure and the feedback pressure is greater than the set overshoot threshold Limit1, it indicates that an overshoot state has been entered. At this point, step 3 is executed. Subsequently, as the target pressure changes, the difference between the target pressure and the feedback pressure Err is calculated. p The system exits the overshoot state when the value falls below the set steady-state threshold Limit2 or when the overshoot time is reached. Generally, Limit1 > Limit2. In this embodiment, Limit1 is set to 0.15 bar and Limit2 is set to 0.03 bar.

[0049] The above Err p = targetPress - actualPress, where targetPress is the target pressure and actualPress is the feedback pressure.

[0050] If the difference between the current target pressure and the feedback pressure is less than or equal to the set overshoot threshold, it means that the overshoot state has not been entered, and then proceed to step 4.

[0051] (2) When the target pressure changes, if the current target pressure is less than the feedback pressure, the current target pressure request status is return, and step 4 is executed.

[0052] (3) If the current target pressure is equal to the feedback pressure, the current target pressure request state is to maintain the existing state. The current target current of the proportional solenoid valve is the current feedback current. At this time, step 5 is executed.

[0053] Step 3: Calculate the overshoot current under overshoot conditions, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve. Specifically:

[0054] TargetCurrent=CurrentBase+OverloadCurrent

[0055] In the formula, TargetCurrent is the current target current of the proportional solenoid valve; CurrentBase represents the feedforward current of the proportional solenoid valve, i.e., CurrentBase = f(targetPress). The value of the feedforward current is obtained directly from the target pressure by consulting an interpolation table. This interpolation table is obtained from the characteristic curve of the proportional solenoid valve and reflects the relationship between the target pressure and the feedforward current. OverloadCurrent represents the current overshoot current, i.e., OverloadCurrent = f(targetPress, Err) p The value of the overshoot current is determined by the target pressure and the difference between the target pressure and the feedback pressure, and can be directly obtained by looking up the interpolation table.

[0056] Step 4: Calculate the current offset value in the forward non-overshoot state or the return state, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve, specifically:

[0057] TargetCurrent=CurrentBase+CurrentOffset

[0058] In the formula, CurrentBase represents the feedforward current of the proportional solenoid valve, and its specific value is as described above. CurrentOffset represents the current offset value in the non-overshoot state or the return state, and its calculation formula is as follows:

[0059] CurrentOffset = Kp * Err p +∑Ki*Err p

[0060] In the formula, Kp is the proportional coefficient, and Ki is the integral coefficient. Here, the anti-saturation limiting of the integral term and the limiting of the current offset value are retained in the traditional PI algorithm; Err p This represents the difference between the target pressure and the feedback pressure. To improve response speed, when the target pressure changes, the integral term ∑Ki*Err is adjusted. p Reset to zero.

[0061] In the above formula, Kp and Ki can be adjusted according to the actual situation. The specific adjustment methods are as follows: when Err p When ≤C, the system is considered to have entered a steady state, where C is the tolerance of the target pressure. At this point, Kp and Ki should be smaller; when Err... p When the value is greater than C, the system is considered to be in a slow adjustment state. At this time, Kp and Ki need to be larger, and due to the compressibility of the gas, in order to reduce overshoot, the operating period of the current offset value needs to be relatively longer.

[0062] Step 5: Based on the current target current of the proportional solenoid valve obtained in Step 2, Step 3, or Step 4, and combined with the system voltage and feedback current collected in Step 1, calculate the current duty cycle TargetDuty of the proportional solenoid valve. (n) Specifically:

[0063] TargetDuty (n) =DutyBase + DutyOffset (n)

[0064] Wherein, DutyBase represents the feedforward duty cycle, which is directly obtained from the current target current and system voltage of the proportional solenoid valve, i.e., DutyBase = f(Targetcurrent, systemVoltage). This formula represents the relationship between the target current of the proportional solenoid valve, the system voltage (systemVoltage), and the duty cycle. In this embodiment, this relationship is a two-dimensional table. DutyOffset (n) This indicates the current duty cycle offset, and

[0065] DutyOffset (n) =Kp * Err i(n) +∑Ki*Err i(n) +Kd*(Err i(n) -Err i(n-1) )

[0066] In the formula, Kp is the proportional coefficient; Ki is the integral coefficient; and Kd is the differential coefficient. All three are customized, while retaining the anti-saturation limiting of the integral term and the limiting of the duty cycle offset in the traditional PID algorithm; Err i(n) It is the difference between the current target current and the feedback current; Err i(n-1) This is the difference between the target current and the feedback current in the previous cycle; n represents the sampling cycle number. To improve response speed, when the system voltage changes significantly, the current integral term ∑Ki*Err is adjusted. i(n) Reset to zero.

[0067] Step 6: Based on the current duty cycle obtained in Step 5, add flutter and output the final duty cycle to realize the control of the proportional solenoid valve of the hydraulic retarder.

[0068] Final Duty (n) Calculated using the following formula:

[0069] Duty (n) =TargetDuty (n) +Amplitude×f(t)

[0070] In the formula, Amplitude is the flutter amplitude; f(t) is a periodic function with time as the independent variable, specifically a triangular wave or sine wave with the flutter period as the period, and a number of sampling points are uniformly taken on each period of the waveform, the number of sampling points being... Where T1 represents the flutter period and T2 represents the sampling period. In this implementation, f(t) is a triangular wave with 8 sampling points, which are sequentially taken from an array, {0,0.5,1,0.5,0,-0.5,-1,-0.5}.

[0071] In summary, this invention utilizes a dual-loop series control strategy of pressure loop and current loop, distinguishing between the forward and retrace phases in the pressure closed-loop control circuit. A segmented control strategy is adopted for the forward phase, while a PI control method is used for the retrace phase. This approach has the advantages of short response time, small overshoot, and good tracking performance.

[0072] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A control method for a proportional solenoid valve used in a hydraulic retarder, characterized in that, Includes the following steps: Step 1: Periodically collect the feedback pressure in the working chamber of the hydraulic retarder and the input signal of the proportional solenoid valve; the input signal includes the feedback current and the system voltage; Step 2: Based on the target pressure in the working chamber of the hydraulic retarder and the feedback pressure collected in Step 1, determine the current target pressure request status. If the current target pressure is greater than the feedback pressure, the current target pressure request status is positive. Further determine whether it has entered the overshoot state. If it has entered the overshoot state, proceed to Step 3. If it has not entered the overshoot state, proceed to Step 4. If the current target pressure is less than the feedback pressure, the current target pressure request status is return, and step 4 is executed; If the current target pressure is equal to the feedback pressure, then the current target pressure request state is to maintain the existing state, and the current target current of the proportional solenoid valve is the current feedback current. At this time, step 5 is executed. Step 3: Calculate the overshoot current under overshoot conditions, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve. Step 4: Calculate the current offset value in the forward non-overshoot state or the return state, and combine it with the feedforward current of the proportional solenoid valve to calculate the current target current of the proportional solenoid valve. Step 5: Based on the current target current of the proportional solenoid valve obtained in Step 2, Step 3, or Step 4, and combined with the feedback current and system voltage collected in Step 1, calculate the current duty cycle of the proportional solenoid valve. Step 6: Based on the current duty cycle obtained in Step 5, add flutter and output the final duty cycle to realize the control of the proportional solenoid valve of the hydraulic retarder.

2. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 1, characterized in that: In step 1, the feedback pressure and feedback current need to be subjected to mean filtering, and the filtering window is the flutter period divided by the sampling period.

3. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 2, characterized in that: The flutter period is 50ms to 150ms; the sampling period is 1ms to 10ms.

4. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 3, characterized in that: In step 2, the method for determining whether an overshoot state has been entered is: If the difference between the current target pressure and the feedback pressure is greater than the set overshoot threshold, it indicates that the overshoot state has been entered. The overshoot state will be exited when the difference between the target pressure and the feedback pressure is less than the set steady-state threshold. The overshoot threshold is greater than the steady-state threshold. If the difference between the current target pressure and the feedback pressure is less than or equal to the set overshoot threshold, it means that the overshoot state has not been entered.

5. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 4, characterized in that: In step 3, the current target current of the proportional solenoid valve is calculated using the following formula: ； In the formula, The target current for the proportional solenoid valve; This represents the feedforward current of the proportional solenoid valve, the value of which can be obtained directly from the target pressure by consulting the interpolation table. This indicates the current overshoot current, the value of which is determined by the target pressure and the difference between the target pressure and the feedback pressure, and can be directly obtained by looking up an interpolation table.

6. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 4, characterized in that: In step 4, the current target current of the proportional solenoid valve. Calculated using the following formula: ； In the formula, This represents the feedforward current of the proportional solenoid valve, the value of which can be obtained directly from the target pressure by consulting the interpolation table. The current offset value represents the current deviation under non-overshoot or retrace conditions, and its calculation formula is as follows: ； In the formula, This is the proportionality coefficient; The integral coefficient; The difference between the target pressure and the feedback pressure, and , For target pressure, To provide feedback on pressure.

7. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 5 or 6, characterized in that: In step 5, the current duty cycle of the proportional solenoid valve Calculated using the following formula: ； in, This indicates the feedforward duty cycle, which can be directly obtained from the current target current and system voltage of the proportional solenoid valve. This indicates the current duty cycle offset, and ； In the formula, This is the proportionality coefficient; The integral coefficient; These are differential coefficients; It is the difference between the current target current and the feedback current; It is the difference between the target current and the feedback current in the previous cycle; n represents the sampling cycle number.

8. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 7, characterized in that: In step 6, the final duty cycle Calculated using the following formula: ； In the formula, It is the flutter amplitude value; It is a periodic function with time as the independent variable, specifically a triangular wave or sine wave with a flutter period as the period, and a number of points are uniformly taken as sampling points in each period of the waveform.

9. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 8, characterized in that: The number of sampling points ,in, Indicates the flutter period, Indicates the sampling period.

10. The control method for the proportional solenoid valve of the hydraulic retarder according to claim 9, characterized in that: The number of sampling points is even.

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