Fuzzy PID (Proportion Integration Differentiation) control algorithm of inflation and deflation main valve system based on high-side electromagnetic valve

Abstract

The invention relates to a fuzzy PID (Proportion Integration Differentiation) control algorithm of an inflation and deflation main valve system based on a high-side electromagnetic valve, which is characterized in that an air pressure outer ring uses a fuzzy PID controller, the difference between a target air pressure value of external communication and the actually measured pressure of an air pressure sensor is obtained and is sent to an air pressure fuzzy PID outer ring controller, and an output value of the outer ring is obtained; the difference between the output value of the outer loop and the collected actual current value of the high-side electromagnetic valve is calculated, closed-loop calculation is conducted through a current inner loop by adopting traditional PI adjustment, the duty ratio of PWM output is adjusted according to the obtained output result, then the actual opening size of the high-frequency electromagnetic valve is adjusted, and the size of an exhaust opening is linearly transformed. The dynamic characteristics of the main valve system change continuously along with different stages of the whole inflation and deflation process, the air pressure control precision and response speed of the main valve inflation and deflation system are improved, and the overshoot and oscillation phenomena in the control process are reduced. And therefore, the inflation and deflation time of the whole vehicle is shortened, and the efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of inflation and deflation of wheeled vehicles, and in particular relates to a fuzzy PID control algorithm of an inflation and deflation main valve system based on a high-side solenoid valve. Background Art

[0002] For a long time, the main valves used in special wheeled vehicles have not been able to exhaust smoothly, and have low accuracy and slow system response.

[0003] In recent years, with the development of electronic technology and the main valve control technology of special vehicles, the exhaust time needs to be shorter and shorter, and the accuracy is getting higher and higher. At present, various component manufacturers have optimized the main valve structure, software algorithm and other aspects. Most of them use ordinary PID closed-loop regulation. However, according to the actual measurement of tires at different air pressure stages during loading, the optimal PID parameters corresponding to the control air pressure will change accordingly. When controlling the air pressure, the control air pressure environment and the thickness and length of the pipes installed on the vehicle will have a great impact on the accuracy of the air pressure value. And as a large hysteresis system, it takes a certain amount of time for the intake air to reach the specified target tire pressure through the high-side solenoid valve.

[0004] The main valve on the market currently has poor overall exhaust, the system's air pressure control accuracy is relatively low, and the PID parameters are fixed during program execution and cannot be adjusted in real time with the system's dynamics. However, in actual applications, due to environmental influences, installed pipeline lengths, and other uncontrollable factors, the dynamic characteristics of the air pressure in the main valve system for charging and discharging air are constantly changing at different stages. Based on the current PID system, it is impossible to adjust the parameters according to the dynamic characteristics of the main valve, which will cause the closed-loop system of the entire PID control system to be unstable, with overshoot and oscillation. Summary of the invention

[0005] The present invention provides a fuzzy PID control algorithm for a main valve system for charging and discharging gas based on a high-side solenoid valve. The technical problem to be solved is: to solve the problem that the air pressure of the main valve is constantly changing in different stages during the entire charging and discharging process, to improve the air pressure control accuracy and response speed of the main valve charging and discharging system, and to reduce the occurrence of overshoot and oscillation in the control process.

[0006] The technical solution of the present invention to solve the above-mentioned problem is: a fuzzy PID control algorithm of a charging and discharging main valve system based on a high-side solenoid valve, characterized in that: a fuzzy PID controller is used in the air pressure outer loop, and the difference between the target air pressure value received from external communication and the pressure of the actual measured air pressure sensor is obtained, and the pressure is given to the air pressure fuzzy PID outer loop controller to obtain the output value of the outer loop, and the difference between the output value of the outer loop and the actual current value of the collected high-side solenoid valve is obtained. The traditional PI adjustment is used for closed-loop calculation in the current inner loop, and the output result is used to adjust the duty cycle of the PWM output, and then to adjust the actual opening size of the high-frequency solenoid valve, so that the exhaust opening size is linearly transformed.

[0007] In order to solve the above technical problems, the present invention provides a double closed-loop control model to enable the entire system to respond faster, introduces fuzzy PID control, and allows PID parameters to adapt to the air pressure stage control requirements of different tires. Through this model, the control accuracy of the system can be further improved, the control speed and the response speed of the entire system can be increased, and the system's ability to resist external interference can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the present invention.

[0009] Figure 2 This is the execution flow chart of the outer loop fuzzy control of the present invention.

[0010] Figure 3 (a) (b) are simulation block diagrams for simulating inflation and exhaust of the present invention.

[0011] Figure 4 This is the internal algorithm block diagram of the fuzzy PID of the present invention.

[0012] Figure 5 The figure is a comparison of the effects of the two control methods for simulating inflation of the present invention.

[0013] Figure 6 The figure is a comparison of the effects of two control methods for simulating exhaust gas of the present invention.

[0014] Figure 7 This is a diagram showing the inflation effect of the present invention when actually applied to a main valve.

[0015] Figure 8 This is a diagram showing the deflation effect of the present invention when actually applied to a main valve. DETAILED DESCRIPTION

[0016] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below.

[0017] The present invention proposes a fuzzy PID control algorithm for a main valve system for charging and discharging gas based on a high-side solenoid valve, which adopts an inner and outer loop PID control method. The inner loop current closed loop adopts a traditional PID controller, and the outer loop air pressure closed loop adopts an air pressure fuzzy PID controller. The specific steps are as follows:

[0018] S1. Determine the closed-loop transfer function of the air pressure fuzzy PID controller:

[0019] The current is collected through the internal IV conversion circuit, which converts the collected current into a 0-3.3V voltage, and finally enters the AD conversion channel of the microcontroller to become a digital signal; the actual sensor pressure value P is collected through the internal air pressure sensor of the main valve system C (t), the control unit receives the actual communication target pressure P through the network communication m (t); The pressure deviation value is obtained according to the set target pressure value and the actual pressure value collected. The calculation formula is as follows:

[0020] e i =P m (t) - P C (t) (1)

[0021] Get the pressure change rate ec i The calculation formula is:

[0022]

[0023] In formula (2), e i (n) is the pressure deviation value obtained by the pressure sensor at the nth moment, e i-1 (n-1) is the pressure deviation value collected by the pressure sensor at the n-1th moment, and T is the sampling period. i The current and pressure change rate are used as the two input variables of the fuzzy PID control. The inner current loop adopts the traditional PID controller, and the outer loop is composed of the air pressure fuzzy PID controller. The transfer function of the continuous PID controller is expressed as follows:

[0024]

[0025] In formula (3), the PID parameters of the continuous PID controller are adjusted using the Ziegler-Nichols law (ZN law). First, assume that T i =∞,T d =0, that is, only proportional control K p , the proportionality coefficient K p The value gradually increases from zero until the output of the system shows a continuous equal-amplitude oscillation for the first time. At this time, the corresponding K p The value is called critical gain and is expressed as K c Indicate, and record the period of oscillation Tc And determine K according to the formula in Table 1 below i and K d .

[0026]

[0027] Table 1

[0028] The closed-loop transfer function of the air pressure fuzzy PID controller of the main valve for charging and discharging gas (hereinafter referred to as the air pressure fuzzy PID controller) can be obtained as follows:

[0029]

[0030] K is the sampling signal.

[0031] S2. Determine the initial PID value of the air pressure fuzzy PID controller: When K=3, the initial K can be calculated using the above chart 1 p0 =12, K i0 =0.021, K d0 =0.1623.

[0032] S2.1. Determine the fuzzy rule algorithm of the air pressure fuzzy PID controller.

[0033] In the air pressure fuzzy PID controller, the fuzzy membership curves of the two inputs are set, using a combination of triangular and Gaussian. The domain is set to -6 to 6, and the membership function is divided into 7, represented by "NB", "NM", "NS", "Z", "PS", "PM", and "PB". The middle five use triangular, and the two sides use Gaussian.

[0034] The pressure deviation e i and its derivatives As input, K p , K i , K d The three parameters are used as the output of the fuzzy strategy. The most commonly used centroid method is used for defuzzification.

[0035] According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K p For output, convert to K p Table 2 of fuzzy rules:

[0036] Table 2K p Fuzzy rule table

[0037]

[0038]

[0039] According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K i For output, convert to K i Fuzzy rule table:

[0040] Table 3K i Fuzzy rule table

[0041]

[0042] According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K d For output, convert to K d Table 4 of fuzzy rules

[0043] K d The fuzzy rule table is as follows:

[0044] Table 4K d Fuzzy rule table

[0045]

[0046] S2.2 determines the real-time dynamic PID value of the air pressure fuzzy PID controller:

[0047] Under the IF-AND-THEN fuzzy rule, a fuzzy comprehensive conclusion is generated, and then an accurate output value is obtained according to the defuzzification equation, and then summed with the initial PID value to obtain the real-time dynamic PID value K p , K i , K d , the output object corresponding to the stable point.

[0048] (a) When the error |e i | is larger, indicating that the absolute value of the error is larger. Regardless of the error change trend, the controller's K should be considered. p Take a larger value to improve the rapidity of response; and to prevent |ec i |Instantaneous overshoot,K d Should take a smaller value; to control overshoot, K i It should also be a very small value.

[0049] (b) When the error |e i |When the size is medium, in order to ensure the response speed of the system and control overshoot, K should be reduced. p ,K i The value should be increased, K d It should be moderate.

[0050] (c) When the error |e i | is small, in order to ensure that the system has good steady-state characteristics, K should be increased. p ,K i To avoid oscillation, K d The value of |ec should be i |Get in touch.

[0051] The PID parameter tuning algorithm is designed by applying fuzzy synthetic reasoning. The tuning differential, integral, and proportional of the kth sampling time are shown in the following formulas (5), (6), and (7):

[0052] k p (k) = k p0 +Δk p (k) (5)

[0053] k i (k) = k i0 +Δk i (k) (6)

[0054] k d (k) = k d0 +Δk d (k) (7)

[0055] In formulas (5), (6), and (7), k p (k), k i (k), k d (k) are the real-time dynamic PID values ​​of real-time proportion, integration and differentiation respectively.

[0056] S3, such as Figure 1 As shown, the air pressure outer loop uses a fuzzy PID controller, which receives the target air pressure value from external communication and the pressure difference of the actual air pressure sensor, and gives it to the air pressure fuzzy PID outer loop controller. The specific control execution process is as follows Figure 2 , and get the output value of the outer loop. The output value of the outer loop is subtracted from the actual current value of the high-side solenoid valve, and the closed-loop calculation is performed using the traditional PI regulation through the current inner loop. The output result is used to adjust the duty cycle of the PWM output, and then to adjust the actual opening size of the high-frequency solenoid valve, so that the exhaust opening size is linearly transformed.

[0057] According to formula (4), actual simulation verification is carried out in Matlab / Simulink, and the transfer function of the outer loop controlled object is obtained as follows:

[0058]

[0059] Modeling through Simul ink, such as Figure 3 , including the simulation block diagram of inflation and exhaust, such as Figure 4 As shown in FIG. 1 , the core algorithm of the fuzzy PID of the present invention is an internal block diagram. Verify the following of the entire system during the inflation process and the exhaust process.

[0060] The specific simulation results are as follows Figure 5 , 6 As shown, by comparing the final results of the traditional PID model adjustment with the fuzzy adjustment model simulation designed by the present invention, it can be obviously found that the fuzzy PID control followability and system responsiveness are more superior.

[0061] After discretizing the model PID algorithm, the standard C language is generated through Simulink and integrated into the control panel of the main valve. The target air pressure value is sent through external CAN communication to obtain the specific actual air pressure inflation and exhaust following effect, such as Figure 7 Inflatable follow effect diagram, Figure 8 This is the exhaust follower effect diagram. It can be seen from the figure that the entire system can achieve a control accuracy of ±3kpa.

[0062] The present invention is specially designed for the main valve of the inflation and deflation system of special wheeled vehicles, and has the overall characteristics of good following effect and fast response speed. In addition, the present invention has been successfully integrated into the main valve of the inflation and deflation system of various types of special vehicles in China and has been put into practical application, and has passed the acceptance inspection with the whole vehicle.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fuzzy PID control algorithm for a main valve system for charging and discharging gas based on a high-side solenoid valve, characterized in that: The air pressure outer loop uses a fuzzy PID controller, which receives the target air pressure value from external communication and the actual pressure measured by the air pressure sensor, and calculates the difference, which is given to the air pressure fuzzy PID outer loop controller to obtain the output value of the outer loop. The output value of the outer loop is calculated by calculating the difference between the actual current value of the high-side solenoid valve collected, and the traditional PI adjustment is used for closed-loop calculation in the current inner loop. The output result is used to adjust the duty cycle of the PWM output, and then to adjust the actual opening size of the high-frequency solenoid valve, so that the exhaust opening size is linearly transformed.

2. According to claim 1, a fuzzy PID control algorithm for a main valve system for charging and discharging gas based on a high-side solenoid valve is characterized in that: The fuzzy PID controller for the main valve pressure of the gas charging and discharging valve is determined as follows: The current is collected through the internal IV conversion circuit, which converts the collected current into a 0-3.3V voltage, and finally enters the AD conversion channel to become a digital signal; the actual sensor pressure value P is collected through the internal air pressure sensor of the main valve system C (t), the control unit receives the actual communication target pressure P through the network communication m (t); The pressure deviation value is obtained according to the set target pressure value and the actual pressure value collected. The calculation formula is as follows: e i =P m (t) - P C (t) (1) Get the pressure change rate ec i The calculation formula is: In formula (2), e i (n) is the pressure deviation value obtained by the pressure sensor at the nth moment, e i-1 (n-1) is the pressure deviation value collected by the pressure sensor at the n-1th moment, T is the sampling period; the pressure deviation value e i The current and pressure change rate are used as the two input variables of the fuzzy PID control. The inner current loop adopts the traditional PID controller, and the outer loop is composed of the air pressure fuzzy PID controller. The transfer function of the continuous PID controller is expressed as follows: In formula (3), the PID parameters of the continuous PID controller are adjusted using the Ziegler-Nichols law. First, assume that T i =∞,T d =0, that is, only proportional control K p , the proportionality coefficient K p The value gradually increases from zero until the output of the system shows a continuous equal-amplitude oscillation for the first time. At this time, the corresponding K p The value is called critical gain and is expressed as K c Indicate, and record the period of oscillation T c .

3. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 2 is characterized in that: The closed-loop transfer function of the fuzzy PID controller for the main valve pressure of the gas charging and discharging valve is: K is the sampling signal.

4. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 3 is characterized in that: The fuzzy rule algorithm of the fuzzy PID controller for the air pressure of the main valve of the gas charging and discharging is as follows: In the fuzzy PID controller for the air pressure of the main valve of the gas charging and discharging, two input fuzzy membership curves are set, which adopts a combination of triangle and Gaussian. The domain is set to -6 to 6, and the membership function is divided into 7, which are represented by "NB", "NM", "NS", "Z", "PS", "PM", and "PB". The middle five use triangle and the two sides use Gaussian. The pressure deviation e i and its derivatives As input, K p , K i , K d The three parameters are taken as the output of the fuzzy strategy and the most commonly used centroid method is used to defuzzify them.

5. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 4 is characterized in that: According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K p For output, convert to K p The fuzzy rule table of According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K i For output, convert to K i The fuzzy rule table of According to the IF-AND-THEN fuzzy control rule, e i ,ec i is the input, K d For output, convert to K d The fuzzy rule table.

6. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 1 is characterized in that: The real-time dynamic PID value of the fuzzy PID controller of the main valve of the gas charging and discharging is determined as follows: Under the IF-AND-THEN fuzzy rule, a fuzzy comprehensive conclusion is generated, and then an accurate output value is obtained according to the defuzzification equation, and then summed with the initial PID value to obtain the real-time dynamic PID value K p , K i , K d , the output object corresponding to the stable point.

7. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 6 is characterized in that: The real-time dynamic PID value determination method of the fuzzy PID controller of the main valve of the gas charging and discharging is as follows: When the error |e i | is larger, indicating that the absolute value of the error is larger. Regardless of the error change trend, the controller's K should be considered. p Take a larger value to improve the rapidity of response; and to prevent |ec i |Instantaneous overshoot,K d Should take a smaller value; to control overshoot, K i It should also be a very small value.

8. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 7 is characterized in that: When the error |e i |When the size is medium, in order to ensure the response speed of the system and control overshoot, K should be reduced. p ,K i The value should be increased, K d It should be moderate.

9. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 1 is characterized in that: When the error |e i | is small, in order to ensure that the system has good steady-state characteristics, K should be increased. p ,K i To avoid oscillation, K d The value of |ec should be i |Get in touch.

10. The fuzzy PID control algorithm of the main valve system for charging and discharging gas based on a high-side solenoid valve according to claim 1 is characterized in that: Fuzzy PID control is introduced to allow PID parameters to adapt to the control requirements of different tire pressure stages. This model can further improve the system's control accuracy, increase the control speed and the response speed of the entire system, and increase the system's ability to resist external interference.

Images