Commercial vehicle air suspension control system and control method thereof

Abstract

The present invention provides a commercial vehicle air suspension control system and control method thereof. The control system comprises a suspension height measurement module, a suspension air pressure measurement module, a data processing unit, and a solenoid valve. The suspension height measurement module is used for real-time measurement of suspension height, and the suspension air pressure measurement module is used for real-time measurement of the air pressure of the suspension air spring. The suspension height measurement module and the suspension air pressure measurement module are respectively connected to the data processing unit and are used to collect the suspension height signal from the suspension height measurement module and the suspension air pressure signal from the suspension air pressure measurement module, calculate and output a control signal to the solenoid valve to control the suspension height and suspension air pressure. Control methods include suspension height PID control, air pressure PID control, switch control, height tolerance adaptive adjustment control, and Smith predictive compensation control. The control system and control method thereof have the characteristics of high control accuracy, fast response speed, low cost, and high reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle air suspension control, and in particular relates to a commercial vehicle air suspension control system and a control method thereof. Background Art

[0002] The air suspension control system and its control method are the key core parts of the air suspension. Currently, there are two main types of control systems on the market. One is a mechanical air suspension control system based on a load-sensing valve. For example, the patent with application number CN201711218085.0 discloses an air suspension vehicle load-sensing valve system and its control method. The other is an electronically controlled air suspension control system based on electronic and electrical equipment. The electronically controlled air suspension control system has been recognized and effectively promoted by the market due to its simple operation, complete functions, and low gas consumption. However, domestic research on electronically controlled air suspension control systems is still in its early stages. The electronically controlled air suspension control system has poor integration and scalability, is expensive, and some functions cannot meet the needs of the domestic market. The air spring on one side often lacks air when unloaded, resulting in wrinkles on the air spring bladder and reduced lifespan. These problems have seriously affected the market promotion and technological expansion of air suspension models. Summary of the Invention

[0003] The present invention provides a commercial vehicle air suspension control system and a control method thereof, which effectively solve the above-mentioned problems.

[0004] The present invention is achieved through the following technical solutions:

[0005] In a first aspect, a commercial vehicle air suspension control system and a control method thereof include: a suspension height measuring module, a suspension air pressure measuring module, a data processing unit and a solenoid valve, wherein the suspension height measuring module is used to measure the suspension height in real time, and the suspension air pressure measuring module is used to measure the air pressure of the suspension air spring in real time. The suspension height measuring module and the suspension air pressure measuring module are respectively connected to the data processing unit, and are used to collect the suspension height signal of the suspension height measuring module and the suspension air pressure signal of the suspension air pressure measuring module, and output a control signal to the solenoid valve after calculation, so as to control the suspension height and suspension air pressure.

[0006] Furthermore, the suspension height measurement module includes: a rotation angle sensor and a motion conversion mechanism, wherein the motion conversion mechanism is used to convert the up and down bounce of the axle into rotation, one end of the motion conversion mechanism is fixed on the axle, and the other end is connected to the rotation angle sensor, and the rotation angle sensor is connected to the data processing unit for transmitting the rotation angle signal to the data processing unit.

[0007] Furthermore, the suspension air pressure measurement module includes: a pressure sensor, which is arranged on the air spring and is also connected to the data processing unit for transmitting the air spring air pressure signal to the data processing unit.

[0008] Furthermore, the data processing unit includes: a main controller and a data collector, the main controller and the data collector are connected, the suspension height measurement module and the suspension air pressure measurement module are respectively connected to the data collector, and are used to collect the suspension height signal and the suspension air pressure signal.

[0009] Furthermore, the system also includes: a data return module, which is connected to the data processing unit and is used to transmit the suspension height data and the suspension air pressure data to the vehicle network terminal.

[0010] In a second aspect, a method for controlling the control system as described above includes:

[0011] Step 1: Obtain the air pressure and suspension height values ​​of the front and rear suspensions, and calculate the average air pressure;

[0012] Step 2: Determine whether the average air pressure is greater than a preset threshold; if so, determine whether the obtained suspension height value is within a normal range; if less than, adjust the suspension air pressure;

[0013] Step 3: If the suspension height value is within the normal range, continue real-time monitoring; if the suspension height value is not within the normal range, use the PID control method to adjust the suspension height until it is within the normal range;

[0014] Furthermore, the adjustment of the suspension air pressure in step 2 includes: detecting whether the air pressure on both sides of the suspension is normal. If normal, continue to detect whether the suspension height is normal; if abnormal, use the PID control method to adjust the suspension height; after adjusting the suspension height, determine whether the air pressure difference on both sides of the suspension is normal. If normal, return to the initial state and continue monitoring. If abnormal, use the PID control method to adjust the air pressure. After adjusting the air pressure, continue to determine whether the suspension height is normal. If normal, return to the initial state and continue monitoring. If abnormal, use the height tolerance for adaptive adjustment.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] The present invention achieves a simple structure, low cost, and high reliability by providing a suspension control system and control method. This system can not only control the height of the air suspension, but also the air pressure of each air spring in the air suspension system, thereby resolving the shortcomings of the prior art and alleviating problems such as wrinkling of the air spring bladder caused by uneven pressure in the air spring under no-load conditions. Furthermore, the system also includes a suspension status information collection and feedback system that can feedback information such as suspension height, axle load, and air pressure of each air spring, thereby supporting fleet management and R&D improvements. The present invention also provides a control method for the electronically controlled air suspension control system, which primarily includes a switch control method, a suspension height PID control method, an air spring pressure PID control method, a height tolerance adaptive adjustment control method, and a Smith predictive compensation control method. The control method has the characteristics of high control accuracy and fast response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the control system structure of the present invention;

[0018] Figure 2 This is a gas circuit schematic diagram of the control system of the present invention;

[0019] Figure 3 This is a schematic diagram of the control method of the present invention;

[0020] Figure 4 This is a schematic diagram of the time-delay compensation control principle of the control system of the present invention;

[0021] Figure 5 This is the corresponding relationship between the PWM duty cycle and the suspension height of the present invention.

[0022] Description of the accompanying drawings:

[0023] 1-air source, 2-air tank, 3-solenoid valve, 4-frame, 5-data collector, 6-LIN line, 7-main controller, 8-CAN line, 9-on-board network terminal, 10-air spring, 11-pressure sensor, 12-angle sensor, 13-motion conversion mechanism, 14-axle, 15-tire, 16-air pipe, 17-circuit harness. DETAILED DESCRIPTION

[0024] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein may be combined with each other.

[0025] Figure 1 Schematic diagram of the control system structure of the present invention; Figure 2 FIG. 1 is a schematic diagram of the gas circuit of the control system of the present invention; FIG. Figure 1 and Figure 2 As shown, the commercial vehicle air suspension control system comprises: a suspension height measurement module, a suspension air pressure measurement module, a data processing unit and a data feedback module.

[0026] Among them, the suspension height measurement module is mainly used for real-time measurement of suspension height data. Its components include a rotation angle sensor 12 and a motion conversion mechanism 13. The motion conversion mechanism 13 is composed of fasteners and a rocker system. Its main function is to convert the up and down bounce of the wheel 15 and the axle 14 into rotation. One end of the motion conversion mechanism is fixed to the axle 14 by a bolt, and the other end is fixed to the measuring end of the rotation angle sensor 12. The rotation angle sensor 12 converts the rotation angle into a PWM duty cycle signal.

[0027] The suspension air pressure measurement module is mainly used for measuring and controlling the air pressure of the air suspension air spring 10. It consists of a pressure sensor 11 and an air pipe 16. The pressure sensor 11 collects the air pressure status of the air spring 10 in real time and converts the air pressure value into a voltage signal.

[0028] The data processing unit includes a main controller 7 and a data collector 5, wherein the data collector 5 collects the PWM duty cycle signal of the angle sensor 12 and the voltage signal of the pressure sensor 11 in real time, and converts the PWM duty cycle signal and the voltage signal into a suspension height signal and an air pressure signal, and performs filtering processing at the same time. After the filtering processing is completed, the suspension height value and the air pressure value of the air spring 11 are sent to the main controller 7 through the LIN line 6. The main controller 7 uses the suspension height PID control method, the air pressure PID control method, the switch control method, the height tolerance adaptive adjustment control method and the Smith prediction compensation control method according to the suspension height value and the air spring 11 pressure value. Give the solenoid valve 3 control instructions, and drive the solenoid valve 3 to perform inflation and deflation through the main controller 7, so as to inflate and deflate the corresponding air spring 10, and finally realize the control of the air suspension system height and the air pressure of the air spring 10. At the same time, the main controller 7 will send the current height value of the air suspension and the air pressure value of each air spring 10 to the CAN bus 8. At the same time, the on-board network terminal 9 collects the suspension height data and air spring 10 air pressure data of the CAN bus 8 in real time, and transmits the data back through the feedback system. Designers and back-end managers can remotely collect air suspension height information and air spring 10 air pressure information through the data acquisition platform.

[0029] Figure 3 FIG. 1 is a schematic diagram of the control method of the present invention; FIG. Figure 3 As shown, the present invention also provides a control method capable of controlling the height and air pressure of the control system of the present invention so that the air suspension system is always in an optimal working state, the method comprising the following steps:

[0030] Step I: Figure 1As shown, when the height of the air suspension system changes, the motion conversion system 13 converts the linear runout of the axle 14 into rotation, driving the measuring end of the rotation angle sensor 12 to rotate. The rotation angle sensor 12 then converts the rotation angle information into a PWM duty cycle signal. After filtering by the data collector 5, it is converted into suspension height information using a table lookup method. The table in the table lookup method is a table showing the relationship between the suspension height value of the commercial vehicle air suspension system and the rotation angle of the motion conversion mechanism 13 (see Figure 5 This is a graph generated from a table showing the relationship between the PWM duty cycle of the rear suspension height sensor and the suspension height of a certain commercial vehicle. Based on the corresponding relationship between the duty cycle and suspension height in the graph, the control system obtains the current actual suspension height value by sampling the current suspension height sensor duty cycle. (When the duty cycle is less than 20%, the suspension is limited and the suspension height reaches a minimum value of 0). This angle relationship table was obtained through experimental means. The pressure sensor 11 collects the air pressure of each air spring 10 of the air suspension system in real time and converts the air pressure signal into a voltage signal. The data collector 5 collects the voltage signal of the pressure sensor 11, filters it, and converts it into the air pressure information of each air spring 10.

[0031] Step II: Figure 1 As shown, the data collector 5 sends the collected real-time suspension height signal and air spring pressure signals of the air suspension system to the main controller 7 through the LIN line 6.

[0032] Step III: Figure 3 and Figure 4 As shown, after the main controller 7 receives the air suspension height signal and the air pressure signal of each air spring 10 of the air suspension system, it first uses the switch control to determine whether to start the air pressure control according to the changes in the suspension height signal value and the air pressure signal value of each air spring 10 of the air suspension system. If the average air pressure of each air spring 10 of the air suspension system is greater than The system does not perform air pressure control, but only performs height PID control, thereby improving height control accuracy. For example, if the average air pressure of each air spring 10 in the air suspension system is less than or equal to The system performs height PID control, air pressure PID control and suspension height tolerance adaptive adjustment control, and simultaneously controls the height of the air suspension system and the air pressure of each air spring 10 of the air suspension system.

[0033] More details are as follows Figure 3 As shown, the switch control method of the present invention is that the main controller receives the air pressure signal of each air spring 10 of the air suspension system sent by the data collector 5 in real time, and The average of the 10 air spring pressures of the air suspension system collected is calculated to obtain the average of the 10 air spring pressures of the current air suspension system. , then the main controller 7 will The average air pressure of each air spring of the air suspension system collected 10 times With the preset air pressure switch threshold (In this example, the threshold is 1 bar = 0.1 MPa) for comparison. > , the main controller 7 turns off the pressure control unit, and the system only performs height control. ≤ , the main controller 7 turns on the pressure control unit, and the system controls the suspension height and air spring pressure.

[0034] Furthermore, if Figure 3 As shown, when the average air pressure of each air spring 10 of the air suspension system is greater than When the system enters the suspension height control unit, if the air suspension height is not within the normal range, the system automatically performs height PID control. If the air suspension system height is within the normal range, no PID control is required and the system returns to the initialization state. When the average air pressure of each air spring 10 in the air suspension system is less than or equal to When the system enters the suspension air pressure control unit, the system first determines whether the average air pressure difference of the air springs 10 on the left and right sides of the suspension is within the normal range. If the average air pressure difference is within the normal range, it continues to determine whether the suspension height is within the normal range. If the suspension height is within the normal range, no control is performed and the system automatically returns to the initialization state. If the average air pressure difference is not within the normal range or the suspension height is not within the normal range, the system first performs suspension height PID control. After the suspension height PID is adjusted, it is again determined whether the average air pressure difference of the air springs 10 on the left and right sides of the suspension is within the normal range. If the average air pressure difference is within the normal range, the system returns to the initial state. If the average air pressure difference is not within the normal range, air pressure PID control is performed. After air pressure PID control, it is again determined whether the suspension height is within the normal range. If the suspension height is within the normal range, the system returns to the initial state. If the suspension height is not within the normal range, the system performs suspension height tolerance adaptive adjustment control. After the suspension height tolerance adaptive adjustment is completed, the air pressure control link is re-entered. Since the height tolerance has been adjusted to adapt to the current suspension state, the system will quickly meet the control requirements after entering the air pressure control link for the second time and enter the initialization state.

[0035] Furthermore, as attached Figure 3 As shown, the suspension height PID control method of the present invention is as follows: The average air pressure of each air spring in the suspension system collected 10 times Greater than the air pressure switch threshold When the main controller 7 The current suspension height value collected and suspension height control target value For comparison, let the height control tolerance be C. The system performs height PID control. Assume that the height control deviation is ,but PID control is highly sensitive to deviation signals. Perform proportional, integral and differential operations, and the control law is: ,in is the proportionality coefficient, is the integration coefficient, is the differential coefficient, where 、 、 The specific value is obtained through test debugging, according to the height deviation After PID calculation, the control signal of the solenoid valve 3 is obtained. The drive unit adjusts the PWM duty cycle of the solenoid valve 3 according to the control signal, thereby controlling the opening area of ​​each port of the solenoid valve 3, and finally realizing the automatic adjustment of the air suspension height. < The system returns to the initialization state and does not perform suspension height PID control.

[0036] Furthermore, as attached Figure 3 As shown, the air pressure control unit control method of the present invention is as follows: The average air pressure of each air spring in the suspension system collected 10 times Less than or equal to the air pressure switch threshold When the main controller 7 first The average air pressure of the 10 air springs on the left side of the suspension system collected Average pressure of right air spring 10 For comparison, assume that the pressure control tolerance is ,when When , the system performs high-level PID control. < The system will judge the current suspension height status. The system performs high-level PID control. < The system returns to the initialization state. The suspension height control method is the same as the height PID control method mentioned above. After the height PID control is completed, the system again calculates the average air pressure of the air spring 10 on the left side of the suspension system. Average pressure of right air spring 10 For comparison, such as < When the system enters the initialization state, The system performs air pressure PID control, and the control method is as follows: the main controller 7 obtains the first The average air pressure of the left air spring 10 collected in the current suspension system Average pressure of right air spring 10 , assuming the pressure control deviation is ,but , the air pressure PID control is the deviation signal Perform proportional, integral and differential operations, and the control law is: ,in is the proportionality coefficient, is the integration coefficient, is the differential coefficient, where 、 、 The specific value is obtained through test debugging, according to the air pressure deviation of the left and right air springs 10 After the PID operation, the control signal of the solenoid valve 3 is obtained. The drive unit adjusts the PWM duty cycle of the solenoid valve 3 according to the control signal, thereby controlling the opening area of ​​each port of the solenoid valve 3, and finally realizing the automatic adjustment of the air suspension pressure. After the air pressure PID control is completed, the system again adjusts the current height of the suspension. Make a judgment, when The system will adjust the height tolerance adaptively, and after the adjustment is completed, it will return to the air pressure control unit to adjust the height and air pressure control. < , the system returns to the initialization state.

[0037] Furthermore, at present, most commercial vehicles in China adopt the structure of front leaf spring and rear air suspension. When the vehicle is unloaded or lightly loaded, the height of the front suspension is generally higher. At the same time, when it is lightly loaded, due to the low air pressure in the air spring, the stiffness of the front suspension leaf spring is generally greater than that of the air spring, that is, the frame is in hard support on the left and right sides of the front suspension and in soft support on the left and right sides of the rear suspension. Since three supporting points can determine a surface, that is, two points on the left and right sides of the front suspension and one point on the left or right side of the rear suspension can make the frame in a horizontal normal height state, the air pressure of the air spring on the non-support side of the rear suspension will be lower than the air pressure of the air spring on the supporting side, resulting in air shortage in the air spring on one side and wrinkles in the air spring, which affects the service life of the air spring and often leads to customer complaints. Therefore, the present invention proposes a two-point height control plus a two-point air pressure control mode.

[0038] In addition, since most commercial vehicles in China currently use non-independent suspension, as shown in the figure below, there is a certain coupling relationship between their left and right movements. At the same time, when the load remains unchanged, changes in the air spring pressure will also cause changes in the suspension height. In addition, there are certain assembly errors in the air suspension assembly itself. This coupling relationship and assembly error will cause differences in different vehicles under different suspension stability states. If a fixed tolerance mode is used, the suspension height on one side will meet the requirements, but the suspension on the other side cannot reach the target value due to mechanical structure problems, or the height reaches the target value but the air pressure cannot reach the target value, resulting in frequent inflation and deflation of the control system and instability. However, if the tolerance value is set too large, it will affect the control accuracy. Therefore, tolerance adaptive adjustment is proposed. When the air suspension height and air pressure cannot be stabilized, the tolerance is automatically adjusted to make the suspension height and air pressure reach the optimal state that can be achieved.

[0039] Therefore, the height tolerance adaptive adjustment control method is: when the system When the system enters the air pressure control unit for the first time and triggers the altitude tolerance adaptive adjustment, the system altitude tolerance C will automatically increase by Y times. When the altitude tolerance is adjusted +1 times after entering the air pressure control unit and the altitude tolerance is adaptively adjusted, the altitude tolerance of the system will continue to increase by Y times based on the previous base value, and so on, until the altitude tolerance reaches the upper limit set by the system. At this time, the system stops air pressure control and only performs altitude control.

[0040] like Figure 4 As shown in the figure, during the operation of the air suspension control system, from collecting the left and right suspension heights and the left and right air spring pressures to issuing solenoid valve control instructions and then driving the solenoid valves, time is consumed, causing system hysteresis. To reduce the system hysteresis and improve the system response sensitivity, this system uses the Smith time-lag compensation method, using the overriding unit to drive the solenoid valve in advance, thereby improving the system response speed and reducing time lag. The time-lag compensation control adopts the Smith predictive compensation controller. Its specific steps are as follows: when the suspension height or air pressure changes due to the road surface or external excitation, the suspension height signal and the air pressure signal R(S) of each air spring 10 in the suspension system are transmitted to the main controller 7. The main controller 7 activates the switch control, height PID control, air pressure PID control and height tolerance adaptive adjustment control, and calculates the control signal of the solenoid valve 3. This signal is sent to the main controller 7 drive unit through the Smith time-lag compensator overriding unit, driving the solenoid valve 3 to operate, thereby compensating for the control time lag of the air suspension system height and air pressure.

[0041] Furthermore, if Figure 1 and 2As shown, the solenoid valve 3 adopts a combined proportional solenoid valve, which receives the PWM duty cycle signal from the main controller drive unit and adjusts the opening area of ​​each valve port according to the size of the duty cycle signal, adjusts the charging and discharging action and charging and discharging speed of each air spring, thereby achieving precise control of the height and air pressure of the air suspension system.

[0042] The above embodiments are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or replacements made by those skilled in the art based on the technical features of the present invention fall within the scope of protection of the present invention.

Claims

1. A control method for a commercial vehicle air suspension control system, characterized in that: Obtain the air pressure value and suspension height value of each air spring in the suspension system, and calculate the average air pressure ; When The average air spring pressure of each suspension system collected Greater than the air pressure switch threshold When The current suspension height value collected and suspension height control target value For comparison, let the height control tolerance be C. Perform height PID control when ,but PID control is highly sensitive to deviation signals. Perform proportional, integral and differential operations; when < Return to the initialization state and do not perform suspension height PID control; When The average air spring pressure of each suspension system collected Less than or equal to the air pressure switch threshold When The average air spring pressure of the left side of the suspension system collected Average air pressure of right air spring For comparison, assume that the pressure control tolerance is ,when When , high PID control is performed; if < Then judge the current suspension height state. When the height PID control is carried out, < Return to the initialization state; After the height PID control is completed, the average air spring pressure on the left side of the suspension system is adjusted again. Average air pressure of right air spring For comparison, such as < When it enters the initialization state, such as Then the air pressure PID control is carried out, and the control method is to obtain the The average air spring pressure of the left side of the current suspension system collected Average air pressure of right air spring , assuming the pressure control deviation is ,but , the air pressure PID control is the deviation signal Perform proportional, integral and differential operations; after the air pressure PID control is completed, the current height of the suspension is again Make a judgment, when When the altitude tolerance is adjusted, the altitude and pressure control unit will be returned to adjust. < When , it returns to the initialization state; The height tolerance adaptive adjustment control method is as follows: i When you enter the air pressure control unit for the first time and trigger the altitude tolerance adaptive adjustment, the altitude tolerance C will automatically increase by Y times. i When the altitude tolerance is adaptively adjusted after entering the air pressure control unit for the first time, the altitude tolerance will continue to increase by Y times based on the previous value, and so on, until the altitude tolerance reaches the set upper limit. At this time, air pressure control will be stopped and only altitude control will be performed.

2. The control method of a commercial vehicle air suspension control system according to claim 1, characterized in that: The commercial vehicle air suspension control system includes: a suspension height measurement module, a suspension air pressure measurement module, a data processing unit and a solenoid valve. The suspension height measurement module is used to measure the suspension height in real time, and the suspension air pressure measurement module is used to measure the air pressure of the suspension air spring in real time. The suspension height measurement module and the suspension air pressure measurement module are respectively connected to the data processing unit and are used to collect the suspension height signal from the suspension height measurement module and the suspension air pressure signal from the suspension air pressure measurement module, calculate and output a control signal to the solenoid valve to control the suspension height and suspension air pressure.

3. The control method of a commercial vehicle air suspension control system according to claim 2, characterized in that: The suspension height measurement module includes: a rotation angle sensor and a motion conversion mechanism, wherein the motion conversion mechanism is used to convert the up and down bounce of the axle into rotation, one end of the motion conversion mechanism is fixed to the axle, and the other end is connected to the rotation angle sensor, and the rotation angle sensor is connected to the data processing unit for transmitting the rotation angle signal to the data processing unit.

4. The control method of a commercial vehicle air suspension control system according to claim 2, characterized in that: The suspension air pressure measurement module includes a pressure sensor, which is arranged on the air spring and is also connected to the data processing unit for transmitting the air spring pressure signal to the data processing unit.

5. The control method of a commercial vehicle air suspension control system according to claim 2, characterized in that: The data processing unit includes: a main controller and a data collector, the main controller is connected to the data collector, and the suspension height measurement module and the suspension air pressure measurement module are respectively connected to the data collector for collecting the suspension height signal and the suspension air pressure signal.

6. The control method of a commercial vehicle air suspension control system according to claim 2, characterized in that: Also includes: A data return module is connected to the data processing unit and is used to transmit the suspension height data and the suspension air pressure data to the vehicle network terminal.

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