A vehicle height adjustment fault diagnosis method based on air suspension system

Abstract

The present invention discloses a vehicle height adjustment fault diagnosis method based on an air suspension system, which relates to the technical field of vehicle suspension design, and includes: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and an adaptive height dynamic adjustment fault detection method; wherein the static self-balancing fault detection method includes: sequentially detecting suspension height fault, airbag pressure fault, vehicle body pitch angle fault, vehicle body roll angle fault and vehicle body side kneeling function fault; the fixed height dynamic adjustment fault detection method includes: calculating the ideal fixed height of the suspension and adjusting the fixed height of the vehicle accordingly and detecting control system hardware fault; the adaptive height dynamic adjustment fault detection method includes: calculating the ideal dynamic height of the suspension and adjusting the adaptive height of the vehicle accordingly, detecting circuit temperature rise fault and detecting dynamic adjustment time fault.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle suspension design, and in particular to a vehicle height adjustment fault diagnosis method based on an air suspension system. Background Art

[0002] As a component connecting the wheels and the vehicle body, the suspension system can play a role in buffering and reducing vibration during the vehicle's driving process, thereby ensuring the vehicle's driving performance and safety performance. Once the parameters of the traditional passive suspension system are designed, they cannot be adjusted, so its performance has certain limitations and cannot adapt to performance changes caused by environmental changes.

[0003] With the continuous development and progress of electronic and information technology, the suspension system has gradually evolved from a passive system with fixed parameters to a semi-active suspension system with adjustable parameters, and the air suspension system is a type of semi-active suspension system. The air suspension system adjusts the vehicle height and suspension stiffness by inflating / deflating the airbag, which has nonlinear characteristics.

[0004] like Figure 1 As shown, the air suspension system is mainly composed of an air pump motor, four air bags, four auxiliary air tanks, four connecting valves, four switch solenoid valves, four height sensors and four pressure sensors. By switching the four switch solenoid valves and selecting their corresponding channels, dynamic adjustment of the vehicle height can be achieved.

[0005] In the actual vehicle height adjustment process, it is necessary to diagnose the vehicle height adjustment process according to the changes in the vehicle state, so as to clarify the current system state. Especially for the two different working conditions of the vehicle static state and the actual driving state, the fault diagnosis of the suspension height dynamic adjustment process has become a key issue that needs to be solved urgently. Summary of the invention

[0006] In view of this, the present invention provides a vehicle height adjustment fault diagnosis method based on an air suspension system, which can realize online detection and fault diagnosis of the system status under static and dynamic driving conditions of the vehicle, thereby further optimizing the driver's driving experience and providing an effective reference and basis for the comprehensive optimization of system performance.

[0007] The technical solution of the present invention is: a vehicle height adjustment fault diagnosis method based on an air suspension system, including: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and an adaptive height dynamic adjustment fault detection method; wherein the static self-balancing fault detection method includes: sequentially detecting suspension height fault, airbag pressure fault, vehicle body pitch angle fault, vehicle body roll angle fault and vehicle body side kneeling function fault; the fixed height dynamic adjustment fault detection method includes: calculating the ideal fixed height of the suspension and thereby raising and lowering the fixed height of the vehicle and detecting control system hardware faults; the adaptive height dynamic adjustment fault detection method includes: calculating the ideal dynamic height of the suspension and thereby raising and lowering the adaptive height of the vehicle, detecting circuit temperature rise faults and detecting dynamic adjustment time faults.

[0008] Preferably, the steps of detecting the suspension height fault are: opening the front connecting valve to connect the front left and front right airbags to each other, opening the rear connecting valve to connect the rear left and rear right airbags to each other; after the gas self-balances for a set time, closing the front and rear connecting valves, detecting the height positions of the four air suspensions corresponding to the front left, front right, rear left and rear right, respectively. fl 、h fr 、h rl and h rr ;

[0009] According to the ideal height position of the vehicle h I and height tolerance h err The expected range of vehicle height is calculated as [h I -h err ,h I +h err ]; if h i ∈[h I -h err ,h I +h err ], no fault is reported; if The air suspension system sends a suspension height abnormal fault signal, and then enters the airbag pressure fault detection step; where i = fl, fr, rl, rr.

[0010] Preferably, the steps of detecting airbag pressure failure are:

[0011] Assuming that the sampling step of the external data acquisition device is ΔT, the corresponding sampling frequency is f E =1 / ΔT, according to the detection frequency f E The pressure inside the four airbags is monitored cyclically, and the pressure P inside the i-th airbag is obtained according to the inherent characteristics of the i-th airbag. i and pressure change rate The tolerance ranges are [P imin,P imax ]and

[0012] Among them, within the time range of 0-T, the number of samples is N E =T / ΔT, and the value of the i-th airbag is obtained. and The calculation method is:

[0013]

[0014] Where P ij and P i(j+1) are the internal air pressure of the i-th airbag at the j-th and j+1-th sampling times, respectively. Λ is the bus delay coefficient, and its value is related to the bus load rate η, that is, the following relationship exists:

[0015]

[0016] If the internal pressure of the i-th airbag is P i ∈[P imin ,P imax ], the air suspension system will not report a fault; if The air suspension system sends a suspension pressure fault signal, and then further detects the pressure change rate inside the airbag.

[0017] if The air suspension system will not report a fault; if The air suspension system sends an air circuit sealing fault signal; if The air suspension system then sends an airbag structural damage fault signal and enters the step of vehicle body pitch angle fault detection.

[0018] Preferably, the vehicle body pitch angle fault detection step is:

[0019] According to the displacement z of the vehicle body at the four suspensions bi , the vehicle body pitch angle θ is calculated as:

[0020]

[0021] Where a and b are the distances from the center of mass of the vehicle to the front axle and rear axle respectively;

[0022] According to the pitch attitude change of the vehicle body, the limit change range of the pitch angle θ when the vehicle is stationary is [θ min ,θ max ], then the maximum change range of the pitch angle θ when the vehicle is moving corresponds to [D1θ min ,D2θ max]; where D1 and D2 are two dynamic correction coefficients of the pitch angle θ; according to the fault tolerance requirements of the air suspension system's extreme inflation / deflation process, the vehicle body is tilted forward to ensure that the headlights point to the ground, and the value ranges of D1 and D2 are set to [0.85, 0.95] and [1.05, 1.1] respectively;

[0023] If θ∈[D1θ min ,D2θ max ], the system operates normally without fault reporting; if θ <D1θ min , the system sends a fault signal that the direction indicated by the vehicle lights deviates from the safe trajectory. At this time, it is necessary to detect whether the solenoid valve responds normally during the system's charging / deflating process; if θ>D2θ max , the system sends a fault signal of abnormal longitudinal posture of the vehicle body. At this time, it is necessary to inspect whether the connecting valves of the four airbags' inflation / deflation process are opened and / or closed normally, and whether there is overcharging and / or over-discharging.

[0024] Preferably, the steps of detecting the vehicle body roll angle fault are:

[0025] According to the displacement z of the vehicle body at the four suspensions bi , calculate the body roll angle for:

[0026]

[0027] Where, B is the vehicle wheelbase;

[0028] According to the roll angle change of the vehicle body movement, the roll angle at rest is obtained The corresponding limit change range is The vehicle's roll angle when moving The corresponding limit change range is H1 and H2 are the roll angles The two stability correction coefficients are set to [1.02, 1.08] and [0.90, 0.98] respectively, so as to ensure that the maximum change range of the body roll when the vehicle is moving is smaller than the maximum change range of the roll angle when the vehicle is stationary.

[0029] if The system operates normally without reporting any faults; if The system sends a left-side tilt fault signal. At this time, it is necessary to detect whether the left-side solenoid valve responds normally during the system's charging / deflating process. If The system sends a right-side vehicle tilt fault signal. At this time, it is necessary to detect whether the right-side solenoid valve responds normally during the system's charging / deflating process.

[0030] Preferably, the steps of detecting the vehicle body side kneeling function fault are:

[0031] Consider the side kneeling function margin of the vehicle body and It is calculated based on the limit height of spring inflation and deflation, and the following equation is used:

[0032]

[0033] In the formula, h i_lim_h and h i_lim_l They are the maximum limit height and the minimum limit height corresponding to the corresponding spring respectively; The minimum roll angle The body side kneeling function margin is corrected, The maximum roll angle The body side kneeling function margin is corrected;

[0034] Define the range of the vehicle body side kneeling limit change as In the vehicle side kneeling function, if No fault is reported; if or No fault is reported, but the side kneeling function start command signal is sent synchronously; if The system sends a vehicle body lateral safety fault signal, at which time the front and rear connecting valves are opened, and the active suppression control of the vehicle body posture is achieved through the self-balancing of the gas between different airbags;

[0035] Preferably, the control system hardware fault detection step is: in the process of charging / deflating, detect whether the controller has signal feedback according to the control instruction; if the controller has a signal response, no fault is reported; if the controller has no signal response, detect the size of the bus load rate η, if the bus load rate η ≥ 75%, the system sends a bus load too high fault signal; if the bus load rate η < 75%, continue to detect the air pump motor control current I c The size is based on the rated working current I A , if I c ∈[0.5I A ,1.2I A ), no fault is reported; if I c <0.5I A , the system sends a bus line fault signal; if I c ≥ 1.2I A , the system sends an air pump motor fault signal; after the inflation and deflation are completed, fixed height dynamic adjustment fault detection is performed according to the static self-balancing fault detection method.

[0036] Preferably, in the adaptive height dynamic adjustment mode, the method for calculating the ideal dynamic height of the suspension is as follows: the controller calculates the ideal dynamic height position h of the vehicle in real time according to the environmental road excitation and the vehicle state. DI ; At this time, the dynamic ideal height position of the vehicle h DI Its dynamic error h Derr The calculation method is:

[0037]

[0038] Where A is the cross-sectional area of ​​the airbag, P ti and P I are the pressures when the solenoid valve is closed and after the gas inside the airbag is balanced, n is the gas index, and its value range is [1,1.38], V0 is the initial volume of the airbag, h ti is the height change value of the suspension at the current moment;

[0039] After the gas inside the airbag is in dynamic equilibrium, the pressure P DI The calculation formula is:

[0040]

[0041] Where P0 is the initial pressure of the airbag, P C and V C They are the pressure and volume changes during the airbag change process;

[0042] Ideally, the airbag is approximated as a cylinder, so the cross-sectional area A of the airbag is approximated according to a fixed value; however, the actual volume of the airbag is not a cylinder, so a correction calculation is performed as follows:

[0043]

[0044] Where H is the height of the airbag in its natural state, D1 and D2 are the cross-sectional diameters of the lower and upper ends of the airbag, respectively, and ψ is the surface correction coefficient of the airbag, which is determined through experimental tests.

[0045] Preferably, the step of detecting a dynamic adjustment time failure includes: during multiple adjustments of the system, the time interval ΔT between each two adjustments must meet the following conditions:

[0046]

[0047] Where, T O and T I The airbag is deflated and inflated for a complete cycle respectively; otherwise, the system sends out an air pump frequent switching fault signal, at which time the relay is forced to close and the vehicle height adjustment process is forced to be interrupted;

[0048] After the inflation and deflation are completed, adaptive height dynamic adjustment fault detection is performed according to the static self-balancing fault detection method.

[0049] Preferably, the step of detecting the circuit temperature rise fault includes: when the air pump motor is working normally, the work W done by the resistance R in the circuit A for:

[0050] W A =I A U A T

[0051] Where U A is the rated voltage of the air pump when it is working normally, and T is the working duration;

[0052] The resistance value R in the circuit will increase with the increase of temperature, so the actual work done W S for:

[0053]

[0054] In the formula, C is the resistance temperature coefficient, t1 and t2 are the temperatures of the resistance R at the initial moment and the current moment respectively;

[0055] Define the temperature rise proportionality coefficient Ψ, then:

[0056]

[0057] If Ψ≤1.45, the system works normally and no fault is reported; if Ψ>1.45, the system issues an abnormal temperature rise fault warning signal, and the relay is closed until Ψ≤1.45.

[0058] Beneficial effects:

[0059] 1. The method of the present invention aims at different vehicle height adjustment processes. Through fault detection in three modes (static self-balancing mode, fixed height dynamic adjustment mode and adaptive height dynamic adjustment mode), it can realize online detection of air suspension system and vehicle height adjustment fault diagnosis under multi-parameters and multi-working conditions, so as to provide operation reference for the driver, provide effective reference for further control optimization, and provide a benchmark for active intervention of the control system; wherein, static self-balancing fault detection realizes system diagnosis under static conditions through suspension height fault detection, airbag pressure fault detection, vehicle body pitch angle and roll angle fault detection and vehicle body side kneeling function fault detection; fixed height dynamic adjustment fault detection realizes system diagnosis of fixed gear adjustment process through suspension ideal height calculation and control system hardware fault detection; and adaptive height dynamic adjustment fault detection realizes system diagnosis under dynamic adjustment through suspension ideal dynamic height calculation, circuit temperature rise fault detection and dynamic adjustment time fault detection.

[0060] 2. The suspension height fault detection in the present invention performs fault diagnosis on the suspension height in a stationary state based on the collected sensor and vehicle status data, that is, based on the ideal height position h of the vehicle. I and height tolerance h err Fault detection is performed on the height positions of the four suspensions respectively, which facilitates the online diagnosis of vehicle height adjustment faults under multiple parameters and multiple working conditions, thereby providing effective early warning and control reference for the controller and driver.

[0061] 3. The airbag pressure fault detection in the present invention performs fault detection on the pressure inside the four airbags according to the tolerance range corresponding to the internal pressure of the airbag and the pressure change rate based on the collected sensor and vehicle status data, so as to facilitate further online diagnosis of vehicle height adjustment faults under multiple parameters and multiple working conditions, thereby providing effective early warning and control reference for the controller and the driver.

[0062] 4. The vehicle body pitch angle fault detection in the present invention is based on the suspension height fault detection and airbag pressure fault detection. The pitch angle of the vehicle body can be calculated using the suspension displacement and the vehicle wheelbase and track. Further, according to the corresponding extreme variation range, the fault diagnosis of the vehicle body posture (pitch angle) in a stationary state can be realized, which is convenient for further realizing the online diagnosis of vehicle height adjustment faults under multiple parameters and multiple working conditions, thereby providing effective early warning and control reference for the controller and the driver; at the same time, the system parameters in the dynamic adjustment process can be dynamically corrected.

[0063] 5. The hardware fault detection of the control system in the present invention can, during the dynamic adjustment process of the vehicle's fixed height, first determine the dead zone adjustment range, calculate the ideal fixed height position and allowable error value of the suspension during the adjustment process; on this basis, perform fault detection on the controller communication process according to the bus load rate and control current; after the system is charged and deflated, further perform fault diagnosis according to the vehicle height adjustment process when the vehicle is stationary.

[0064] 6. The method for calculating the ideal dynamic height of the suspension in the present invention is to consider the dynamic change of the cross-sectional area of ​​the airbag during the dynamic adjustment of the vehicle's adaptive height. First, it is necessary to calculate the ideal dynamic height position, dynamic error and dynamic equilibrium pressure of the gas of the vehicle, thereby performing fault diagnosis according to the vehicle height adjustment process when the vehicle is stationary. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of the air suspension system.

[0066] Figure 2 The figure is a schematic diagram of a height adjustment fault diagnosis process of a vehicle based on an air suspension system according to the present invention. DETAILED DESCRIPTION

[0067] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0068] This embodiment provides a vehicle height adjustment fault diagnosis method based on an air suspension system, which can realize online detection and fault diagnosis of the system status under static and dynamic driving conditions of the vehicle, thereby further optimizing the driver's driving experience and providing an effective reference and basis for the comprehensive optimization of system performance.

[0069] When a vehicle is driving under different working conditions, the dynamic response of its system changes dynamically with the actual working conditions. The collected system status data can reflect the fluctuations and changes of the environment on the one hand, and on the other hand, the system's own status can be detected according to the status fluctuations, thereby obtaining the system stability and subsystem fault status during vehicle driving in real time.

[0070] like Figure 2 As shown, the method is divided into three parts: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and an adaptive height dynamic adjustment fault detection method;

[0071] 1. Static self-balancing fault detection method (i.e. vehicle height adjustment fault diagnosis method performed when the vehicle is stationary)

[0072] Step 1.1: Detecting suspension height fault

[0073] Open the front connecting valve to connect the front left and front right airbags, and open the rear connecting valve to connect the rear left and rear right airbags. After the gas self-balances for a set time (preferably 4 to 6 seconds), close the front and rear connecting valves and detect the height positions of the four air suspensions corresponding to the front left, front right, rear left and rear right, respectively. fl 、h fr 、h rl and h rr ;

[0074] According to the ideal height position of the vehicle h I and height tolerance h err , it can be calculated that the expected range of vehicle height is [h I -h err ,h I +h err ]; if h i (i=fl,fr,rl,rr)∈[h I -h err ,h I +h err ], the air suspension system operates normally and no air suspension system fault is reported; if h i(i=fl,fr,rl,rr) [h I -h err ,h I +h err ], the air suspension system sends a suspension height abnormality fault signal. At this time, it is necessary to proceed to step 1.2 to inspect the structure and pipeline sealing of the four airbags to see if they are intact;

[0075] Step 1.2: Detect airbag pressure failure

[0076] Assuming that the sampling step of the external data acquisition device is ΔT, then the corresponding sampling frequency is f E =1ΔT, according to the detection frequency f E The pressure inside the four airbags is monitored cyclically, and the pressure P inside the i-th airbag can be obtained according to the inherent characteristics of the i-th airbag (i = fl, fr, rl, rr) i and pressure change rate The tolerance ranges correspond to [P imin ,P imax ]and

[0077] Among them, within the time range of 0-T, the number of samples is N E =T / ΔT, we can get the value of the i-th airbag and The specific calculation method is:

[0078]

[0079] Where P ij and P i(j+1) are the internal air pressure of the i-th airbag at the j-th and j+1-th sampling times, respectively. Λ is the bus delay coefficient, and its value is related to the bus load rate η, that is, the following relationship exists:

[0080]

[0081] If the internal pressure of the i-th airbag is P i ∈[P imin ,P imax ], the internal pressure of the airbag is normal and the air suspension system does not report a fault; if The air suspension system sends a suspension pressure fault signal, and it is necessary to further detect the pressure change rate inside the airbag.

[0082] if If the pressure inside the i-th airbag changes normally, the air suspension system will not report a fault; If the pressure inside the i-th airbag changes abnormally, the air suspension system sends an air circuit sealing fault signal; If the internal pressure of the i-th airbag changes abnormally, the air suspension system sends an airbag structural damage fault signal and proceeds to step 1.3;

[0083] Step 1.3: Detect vehicle pitch angle fault

[0084] According to the displacement z of the vehicle body at the four suspensions bi (i=fl,fr,rl,rr), the vehicle body pitch angle θ can be calculated as:

[0085]

[0086] Where a and b are the distances from the center of mass of the vehicle to the front axle and rear axle respectively;

[0087] According to the pitch attitude change of the vehicle body movement, the maximum change range of the pitch angle θ when the vehicle is stationary can be obtained as [θ min ,θ max ], then the maximum change range of the pitch angle θ when the vehicle is moving corresponds to [D1θ min ,D2θ max ]; D1 and D2 are two dynamic correction coefficients of the pitch angle θ respectively; according to the fault tolerance requirements of the air suspension system's extreme inflation / deflation process, the vehicle body is tilted slightly forward to ensure that the headlights point to the ground, making it easier for the driver to see the road conditions. The value ranges of D1 and D2 are set to [0.85, 0.95] and [1.05, 1.1] respectively;

[0088] If θ∈[D1θ min ,D2θ max ], the system operates normally without fault reporting; if θ <D1θ min , the system sends a fault signal that the direction indicated by the vehicle lights deviates from the safe trajectory. At this time, it is necessary to detect whether the solenoid valve responds normally during the system's charging / deflating process; if θ>D2θ max , the system sends a fault signal of abnormal longitudinal posture of the vehicle body. At this time, it is necessary to inspect whether the connecting valves of the four airbags' inflation / deflation process are opened and / or closed normally, and whether there is overcharging and / or over-discharging.

[0089] In static self-balancing fault detection, in order to ensure the stability of the vehicle, the following steps are performed:

[0090] Step 1.4: Detect body roll angle fault

[0091] In order to ensure the stability of the vehicle, the displacement z of the vehicle body at the four suspensions is bi(i=fl,fr,rl,rr), the body roll angle can be calculated for:

[0092]

[0093] Where, B is the vehicle wheelbase;

[0094] According to the roll angle change of the vehicle body, the roll angle at rest can be obtained. The corresponding limit change range is The vehicle's roll angle when moving The corresponding limit change range is H1 and H2 are the roll angles To ensure that the vehicle body rolls to the limit of the vehicle posture, the rollover accident caused by excessive roll of the vehicle body can be prevented. Therefore, the value ranges of H1 and H2 are [1.02, 1.08] and [0.90, 0.98] respectively, thereby ensuring that the maximum range of the vehicle body roll when the vehicle is moving is slightly smaller than the maximum range of the roll angle when the vehicle is stationary.

[0095] if The system operates normally without reporting any faults; if The system sends a left-side tilt fault signal. At this time, it is necessary to detect whether the left-side solenoid valve responds normally during the system's charging / deflating process. If The system sends a right-side vehicle tilt fault signal. At this time, it is necessary to detect whether the right-side solenoid valve responds normally during the system's charging / deflating process.

[0096] Step 1.5: Check the vehicle body side kneeling function failure

[0097] Consider the side kneeling function margin of the vehicle body and ( The minimum roll angle The body side kneeling function margin is corrected, The maximum roll angle The corrected body side kneeling function margin) is calculated based on the limit height of the spring inflation and deflation, and the following equation is used:

[0098]

[0099] In the formula, h i_lim_h and h i_lim_l (i=fl,fr,rl,rr) are the maximum limit height and minimum limit height of the corresponding spring respectively;

[0100] Define the range of the vehicle body side kneeling limit change as In the vehicle side kneeling function, if The system operates normally without reporting any faults; if or The system is operating normally without reporting any faults, but at this time, the side kneeling function start command signal is sent synchronously; if The system sends a vehicle body lateral safety fault signal. At this time, the front and rear connecting valves need to be opened to achieve active suppression and control of the vehicle body posture through the self-balancing of the gas between different airbags.

[0101] 2. Fixed height dynamic adjustment fault detection method

[0102] During the vehicle's travel, the driver will adjust the fixed height of the vehicle body according to environmental changes. The controller provides a control signal to the air pump motor according to the rise / fall command, so as to achieve dynamic adjustment of the fixed height during the vehicle's travel.

[0103] Step 2.1: Calculate the ideal suspension height and adjust the vehicle height accordingly

[0104] Due to the effect of road excitation, the actual air suspension height will fluctuate. At this time, in order to prevent the air pump from repeatedly switching on and off during the filling / deflation process due to the influence of road excitation, the dead zone adjustment range of the air suspension height is set to [h dead_min ,h dead_max ]; At this time, according to the preset target height h of the vehicle g , the ideal height position h of the air suspension during the lifting and lowering adjustment process can be obtained I and the allowable error value h err The calculation method is:

[0105]

[0106] Where ω is the time hysteresis coefficient, and are the speeds of change of sprung mass velocity, unsprung mass velocity and road excitation respectively;

[0107] According to the dead zone adjustment range [h dead_min ,h dead_max ]、Ideal height position h I and the allowable error value h err Determine [h I -|h err |-h dead_min ,h I +|h err |+h dead_min]; As road excitation can cause air spring vibration, in order to avoid the frequent opening and closing of the solenoid valve caused by normal vibration and extend the service life of the system, the system is [h I -h dead_min ,h I +h dead_min ] range does not respond, but within the height position adjustment range [h I -|h err |-h dead_min ,h I -h dead_min ] and [h I +h dead_min ,h I +|h err |+h dead_min ]The control system inside the vehicle is activated, and the airbag is inflated / deflated to adjust the height of the vehicle by controlling the solenoid valve switch.

[0108] Step 2.2: Detect control system hardware failure

[0109] During the inflation / deflation process, the controller is checked for signal feedback according to the control command; if the controller responds with a signal, the system operates normally without reporting a fault; if the controller does not respond with a signal, the bus load rate η needs to be detected. If the bus load rate η ≥ 75%, the system sends a bus overload fault signal; if the bus load rate η < 75%, the air pump motor control current I continues to be detected. c The size is based on the rated working current I A , while ensuring the air pump motor control current I c If the value is neither too small nor too large (too small the battery valve cannot be opened, too large the solenoid valve will burn out), c ∈[0.5I A ,1.2I A ), the system operates normally without reporting any faults; if I c <0.5I A , the system sends a bus line fault signal; if I c ≥ 1.2I A , the system sends an air pump motor fault signal; after the inflation and deflation are completed, the fixed height dynamic adjustment fault detection is performed in the order shown in the static self-balancing fault detection method.

[0110] 3. Adaptive height dynamic adjustment fault detection method

[0111] Step 3.1: Calculate the ideal dynamic height of the suspension and adjust the vehicle's adaptive height accordingly

[0112] In this mode (adaptive height dynamic adjustment mode), the controller calculates the ideal dynamic height position h of the vehicle in real time based on the environmental road stimulus and vehicle status. DI , in order to achieve good vehicle trafficability and smoothness under complex conditions; at this time, the ideal dynamic height position of the vehicle h DI Its dynamic error h Derr The calculation method is:

[0113]

[0114] Where A is the cross-sectional area of ​​the airbag, P ti and P I are the pressures when the solenoid valve is just closed and after the gas inside the airbag is balanced, n is the gas index, and its value range is [1,1.38], V0 is the initial volume of the airbag, h ti is the height change value of the suspension at the current moment;

[0115] After the gas inside the airbag is in dynamic equilibrium, the pressure P DI The calculation formula is:

[0116]

[0117] Where P0 is the initial pressure of the airbag, P C and V C They are the pressure and volume changes during the airbag change process;

[0118] Ideally, the airbag is approximated as an ideal cylinder, so the cross-sectional area A of the airbag is approximately calculated according to a fixed value; however, the actual volume of the airbag is not a strict cylinder, and further correction calculation is required, as follows:

[0119]

[0120] Where H is the height of the airbag in its natural state (the natural state refers to the state when the airbag is not compressed, at which point the shape of the airbag is similar to a truncated cone), D1 and D2 are the cross-sectional diameters of the lower and upper ends of the airbag, respectively, and ψ is the surface correction coefficient of the airbag, which can be determined through experimental tests;

[0121] Therefore, according to the dead zone adjustment range [h dead_min ,h dead_max ], the ideal height position h in the adaptive height dynamic adjustment fault detection method DI and the allowable error value h Derr The vehicle height can be raised or lowered according to step 1, and the control system hardware fault detection can be performed according to the steps described in step 2.2;

[0122] Step 3.2: Detect circuit temperature rise fault

[0123] The air pump motor needs to be switched on and off by closing the relay, and the control current of the relay is relatively large. During the process of adaptive repeated adjustment, the relay may be damaged due to abnormal temperature rise, thus affecting the device life and system reliability. Therefore, it is necessary to dynamically monitor the system safety by testing the relay circuit;

[0124] When the air pump motor is working normally, the work done by the resistance R in the circuit is W A for:

[0125] W A =I A U A T

[0126] Where U A is the rated voltage of the air pump when it is working normally, and T is the working duration;

[0127] The resistance value R in the circuit will increase with the increase of temperature, so the actual work done W S for:

[0128]

[0129] In the formula, C is the resistance temperature coefficient, t1 and t2 are the temperatures of the resistance R at the initial moment and the current moment respectively;

[0130] Define the temperature rise proportionality coefficient Ψ, then:

[0131]

[0132] If Ψ≤1.45, the system works normally and no fault is reported; if Ψ>1.45, the system issues an abnormal temperature rise fault warning signal, and the relay is closed until Ψ≤1.45; the limit value 1.45 is calculated based on the normal current value of the components.

[0133] Step 3.3: Detecting Dynamic Adjustment Time Failure

[0134] Differences in environmental roads may lead to the need to repeatedly adjust the vehicle height. However, in order to avoid a sudden reduction in system life caused by frequent opening and closing, during multiple adjustments of the system, the time interval ΔT between each two adjustments should meet the following conditions:

[0135]

[0136] Where, T O and T IThe airbag height adjustment process is interrupted.

[0137] After the inflation and deflation are completed, adaptive height dynamic adjustment fault detection is performed according to the static self-balancing fault detection method.

[0138] If after the three types of height adjustment fault diagnosis corresponding to the static self-balancing fault detection method, the fixed height dynamic adjustment fault detection method and the adaptive height dynamic adjustment fault detection method, the system does not send out a fault signal, it means that the system is working normally at this time. Otherwise, the driver should troubleshoot the fault according to the specific fault alarm information before driving and debugging the vehicle.

[0139] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A vehicle height adjustment fault diagnosis method based on an air suspension system, characterized in that: include: Static self-balancing fault detection method, fixed height dynamic adjustment fault detection method and adaptive height dynamic adjustment fault detection method; wherein, the static self-balancing fault detection method includes: sequentially detecting suspension height fault, airbag pressure fault, vehicle pitch angle fault, vehicle roll angle fault and vehicle side kneeling function fault; the fixed height dynamic adjustment fault detection method includes: calculating the ideal fixed height of the suspension and adjusting the fixed height of the vehicle accordingly and detecting control system hardware fault; the adaptive height dynamic adjustment fault detection method includes: calculating the ideal dynamic height of the suspension and adjusting the adaptive height of the vehicle accordingly, detecting circuit temperature rise fault and detecting dynamic adjustment time fault; the air suspension system consists of an air pump motor, four airbags, four auxiliary air tanks, four connecting valves, four switch solenoid valves, four height sensors and four pressure sensors. By switching the switches of the four switch solenoid valves and selecting their corresponding channels, dynamic adjustment of the vehicle height can be achieved.

2. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 1, characterized in that: The steps of the suspension height fault detection are: opening the front connecting valve to connect the front left and front right airbags, opening the rear connecting valve to connect the rear left and rear right airbags; after the gas self-balances for a set time, closing the front and rear connecting valves, detecting the height positions of the four air suspensions corresponding to the front left, front right, rear left and rear right, respectively. , , and ; According to the ideal height position of the vehicle and height tolerance , the expected range of vehicle height is calculated as [ ];if [ ], no fault is reported; if [ ], the air suspension system sends a suspension height abnormality fault signal, and then enters the airbag pressure fault detection step; wherein, .

3. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 2, characterized in that: The steps of the air bag pressure fault detection are: Assume that the sampling step size of the external data acquisition device is , then the corresponding sampling frequency is , by detection frequency The pressure inside the four airbags is monitored cyclically. The inherent characteristics of the airbag are obtained The pressure inside the airbag and pressure change rate The tolerance ranges are [ ]and[ ]; Among them, Within the time range, the number of samples is , get the Airbag and The calculation method is: In the formula, and Respectively The airbag is and The internal air pressure of the airbag was sampled. is the bus delay coefficient, and its value is related to the bus load rate Related, that is, there is the following relationship: If The internal pressure of the airbag [ ], the air suspension system will not report a fault; if [ ], the air suspension system sends a suspension pressure fault signal, and then further detects the pressure change rate inside the airbag ; if [ ], the air suspension system will not report a fault; if < , the air suspension system sends an air circuit sealing fault signal; if > , the air suspension system sends an airbag structural damage fault signal and enters the step of vehicle body pitch angle fault detection.

4. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 3, characterized in that: The steps of vehicle body pitch angle fault detection are: According to the displacement of the vehicle body at the four suspensions ,in, , calculate the vehicle body pitch angle for: In the formula, and are the distances from the vehicle’s center of mass to the front and rear axles, respectively; According to the pitch attitude change of the vehicle body movement, the pitch angle of the vehicle when it is stationary is obtained The corresponding limit change range is [ ], then the pitch angle of the vehicle when moving The corresponding limit change range is [ ];in, and Pitch angle According to the error tolerance requirements of the air suspension system's limit inflation / deflation process, the vehicle body is tilted forward to ensure that the headlights point to the ground. and The value ranges of are [0.85, 0.95] and [1.05, 1.1] respectively; if [ ], the system operates normally without reporting any faults; if , the system sends a fault signal that the vehicle light indicates that the direction has deviated from the safe trajectory. At this time, it is necessary to detect whether the solenoid valve responds normally during the system's charging / deflating process; if , the system sends a fault signal of abnormal longitudinal posture of the vehicle body. At this time, it is necessary to inspect whether the connecting valves of the four airbags' inflation / deflation process are opened and / or closed normally, and whether there is overcharging and / or over-discharging.

5. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 4, characterized in that: The steps of vehicle body roll angle fault detection are: According to the displacement of the vehicle body at the four suspensions ,in, , calculate the body roll angle for: In the formula, is the vehicle wheelbase; According to the roll angle change of the vehicle body movement, the roll angle at rest is obtained The corresponding limit change range is [ ], then the roll angle of the vehicle when moving The corresponding limit change range is [ ], and Roll Angle Two stability correction factors for and The value ranges of are [1.02, 1.08] and [0.90, 0.98], respectively, which ensures that the maximum range of the vehicle body roll when the vehicle is moving is smaller than the maximum range of the roll angle when it is stationary [ ]; if [ ], the system operates normally without reporting any faults; if , the system sends a left-side tilt fault signal. At this time, it is necessary to detect whether the left-side solenoid valve responds normally during the system's charging / deflating process; if , the system sends a right-side vehicle tilt fault signal. At this time, it is necessary to detect whether the right-side solenoid valve responds normally during the system's charging / deflating process.

6. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 5, characterized in that: The steps of the vehicle body side kneeling function fault detection are: Consider the side kneeling function margin of the vehicle body and , which is calculated based on the limit height of spring inflation and deflation, the following equation is obtained: In the formula, and are the maximum and minimum height limits of the corresponding springs, respectively, where: ; The minimum roll angle The body side kneeling function margin is corrected, The maximum roll angle The body side kneeling function margin is corrected; Define the vehicle body side kneeling limit change range as [ ], in the vehicle side kneeling function, if [ ], no fault is reported; if [ )or ( ], no fault is reported, but the side kneeling function start command signal is sent synchronously at this time; if [ ], the system sends a vehicle body lateral safety fault signal, at this time open the front and rear connecting valves, through the gas self-balancing between different airbags to achieve the active suppression control of the vehicle body posture; Among them, ( )<( )<( )<( ).

7. The vehicle height adjustment fault diagnosis method based on the air suspension system according to any one of claims 1 to 6, characterized in that: The control system hardware fault detection steps are: in the process of filling / deflating, detect whether the controller has signal feedback according to the control instruction; if the controller has signal response, no fault is reported; if the controller has no signal response, detect the bus load rate If the bus load rate , the system sends a bus overload fault signal; if the bus load rate , then continue to detect the air pump motor control current The size of the rated working current ,if , no fault is reported; if , the system sends a bus line fault signal; if , the system sends an air pump motor fault signal; after the filling and deflation are completed, fixed height dynamic adjustment fault detection is performed according to the static self-balancing fault detection method.

8. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 7, characterized in that: In the adaptive height dynamic adjustment mode, the method for calculating the ideal dynamic height of the suspension is as follows: the controller calculates the ideal dynamic height position of the vehicle in real time according to the environmental road excitation and the vehicle state. ; At this time, the dynamic ideal height position of the vehicle Its dynamic error The calculation method is: In the formula, is the cross-sectional area of ​​the airbag, and They are the pressure when the solenoid valve is closed and the pressure after the gas inside the airbag is balanced. is the gas index, and its value range is [1, 1.38], is the initial volume of the airbag, is the height change value of the suspension at the current moment; After the gas inside the airbag is in dynamic equilibrium, the pressure The calculation formula is: In the formula, P 0 is the initial pressure of the airbag, P C and V C They are the pressure and volume changes during the airbag change process; Ideally, the airbag is approximated as a cylinder, so the cross-sectional area of ​​the airbag is The approximate calculation is performed according to the fixed value; however, the actual volume of the airbag is not a cylinder, so a correction calculation is performed as follows: In the formula, is the height of the airbag in its natural state, and are the cross-sectional diameters of the lower and upper ends of the airbag, is the surface correction coefficient of the airbag, which is determined through experimental tests.

9. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 8, characterized in that: The step of detecting a dynamic adjustment time failure includes: during multiple adjustments of the system, the time interval between each two adjustments The following conditions must be met: In the formula, and The airbag is deflated and inflated for a complete cycle respectively; otherwise, the system sends out an air pump frequent switching fault signal, at which time the relay is forced to close and the vehicle height adjustment process is forced to be interrupted; After the inflation and deflation are completed, adaptive height dynamic adjustment fault detection is performed according to the static self-balancing fault detection method.

10. The vehicle height adjustment fault diagnosis method based on the air suspension system according to claim 7, characterized in that: The step of detecting the circuit temperature rise fault includes: when the air pump motor is working normally, the resistance in the circuit R Work done for: In the formula, It is the rated voltage when the air pump is working normally. Duration of work; The resistance value in the circuit R will increase with increasing temperature, so the actual work done for: In the formula, is the temperature coefficient of resistance, and Respectively, the resistance value R Temperature at the initial moment and the current moment; Define the temperature rise proportionality factor , then: if , then the system works normally and no fault is reported; if , the system issues an abnormal temperature rise fault warning signal, and the relay is closed until .

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