CN115891544A - Vehicle height adjustment fault diagnosis method based on air suspension system - Google Patents

Abstract

The 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 comprises the following steps: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and a self-adaptive height dynamic adjustment fault detection method; the static self-balancing fault detection method comprises the following steps: sequentially detecting a suspension height fault, an airbag pressure fault, a vehicle body pitch angle fault, a vehicle body side inclination angle fault and a vehicle body side kneeling function fault; the fixed height dynamic adjustment fault detection method comprises the following steps: calculating the ideal fixed height of the suspension, adjusting the fixed height of the vehicle in a lifting manner according to the ideal fixed height of the suspension, and detecting hardware faults of a control system; the self-adaptive height dynamic adjustment fault detection method comprises the following steps: calculating the ideal dynamic height of the suspension, adjusting the self-adaptive height of the vehicle according to the ideal dynamic height, detecting the temperature rise fault of the loop and detecting the time fault of dynamic adjustment.

Description

Vehicle height adjustment fault diagnosis method based on air suspension system

Technical Field

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

Background

The suspension system is used as a part for connecting the wheels and the vehicle body, and can play a role in buffering and damping in the running process of the vehicle, so that the driving performance and the safety performance of the vehicle are ensured. Once the parameters of the traditional passive suspension system are designed, the parameters cannot be adjusted, so that the performance of the traditional passive suspension system has certain limitations and cannot adapt to the performance change requirement caused by environmental change.

With the continuous development and progress of electronic and information technology, a suspension system is gradually developed from a passive system with fixed parameters to a semi-active suspension system with adjustable parameters, and an air suspension system belongs to one of the semi-active suspension systems. The air suspension system adjusts the height of the vehicle body and the suspension rigidity by performing an air-charging/discharging operation on an air bag, and has a non-linear characteristic itself.

As shown in fig. 1, the air suspension system is mainly composed of an air pump motor, four air bags, four auxiliary air tanks, four communicating valves, four switching solenoid valves, four height sensors and four pressure sensors, and the dynamic adjustment of the vehicle height can be realized by switching the switches of the four switching solenoid valves and the selection of corresponding channels thereof.

In the actual vehicle height adjustment process, the vehicle height adjustment process needs to be diagnosed according to the change of the vehicle state, so as to clearly determine the current system state. Especially, for two different working conditions of a vehicle static state and an actual running state, fault diagnosis in a suspension height dynamic adjustment process becomes a critical problem to be solved urgently.

Disclosure of Invention

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

The technical scheme of the invention is as follows: a vehicle height adjustment fault diagnosis method based on an air suspension system comprises the following steps: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and a self-adaptive height dynamic adjustment fault detection method; the static self-balancing fault detection method comprises the following steps: sequentially detecting a suspension height fault, an airbag pressure fault, a vehicle body pitch angle fault, a vehicle body side inclination angle fault and a vehicle body side kneeling function fault; the fixed height dynamic adjustment fault detection method comprises the following steps: calculating the ideal fixed height of the suspension, adjusting the fixed height of the vehicle in a lifting manner according to the ideal fixed height of the suspension, and detecting hardware faults of a control system; the self-adaptive height dynamic adjustment fault detection method comprises the following steps: calculating the ideal dynamic height of the suspension, adjusting the self-adaptive height of the vehicle according to the ideal dynamic height, detecting the temperature rise fault of the loop and detecting the time fault of dynamic adjustment.

Preferably, the suspension height fault detection step is: opening a front communicating valve to enable the front left air bag and the front right air bag to be communicated with each other, and opening a rear communicating valve to enable the rear left air bag and the rear right air bag to be communicated with each other; after the gas self-balancing setting time, closing the front and rear communicating valves, and detecting the height positions of four air suspensions corresponding to the front left, the front right, the rear left and the rear right to be h respectively _fl 、h _fr 、h _rl And h _rr ；

According to the ideal height h of the vehicle _I And a height tolerance value h _err And calculating to obtain the expected value range of the vehicle height as [ h _I -h _err ,h _I +h _err ](ii) a If h is _i ∈[h _I -h _err ,h _I +h _err ]If yes, the fault is not reported; if it is used

The air suspension system sends a suspension height abnormal fault signal, and then the step of detecting the pressure fault of the air bag is carried out; where i = fl, fr, rl, rr.

Preferably, the step of detecting the failure of the air bag pressure is:

suppose thatIf the sampling step length of the external data acquisition device is Δ T, the corresponding sampling frequency is f _E =1/Δ T in terms of detection frequency f _E Circularly monitoring the pressure in the four air bags, and obtaining the pressure P in the ith air bag according to the inherent characteristics of the ith air bag _i And rate of change of pressure

Respectively is [ P ] _imin ,P _imax ]And &>

Wherein, in the time range of 0-T, the sampling number is N _E = T/Delta T, obtaining i-th air bag

And &>

The calculation method is as follows:

in the formula, P _ij And P _i(j+1) Respectively is the internal air pressure of the ith air bag under the sampling of the jth and j +1 times, and Λ is a bus delay coefficient, and the value of the lambda is related to the bus load rate eta, namely the following relation is provided:

if the internal pressure P of the ith air bag _i ∈[P _imin ,P _imax ]The air suspension system does not report the fault; if it is not

The air suspension system sends a suspension pressure failure signal when the rate of change of the pressure inside the air bag is further detected/>

If it is used

The air suspension system does not report a fault; if->

The air suspension system sends a gas path tightness fault signal; if +>

The air suspension system sends an air bag structural damage fault signal and the step of vehicle body pitch angle fault detection is transferred.

Preferably, the step of detecting the vehicle body pitch angle fault is as follows:

according to the displacement z of the vehicle body at the four suspensions _bi And calculating to obtain the pitch angle theta of the vehicle body as follows:

wherein a and b are the distances from the center of mass of the vehicle to the front axle and the rear axle, respectively;

obtaining the limit change range [ theta ] corresponding to the pitch angle theta when the vehicle is static according to the pitch attitude change of the vehicle body movement _min ,θ _max ]The limit variation range corresponding to the pitch angle θ when the vehicle is traveling corresponds to [ D [ ] ₁ θ _min ,D ₂ θ _max ](ii) a Wherein D is ₁ And D ₂ Two dynamic correction coefficients of a pitch angle theta are respectively; setting D according to the fault-tolerant space requirement of the limit inflation/deflation process of the air suspension system, and simultaneously enabling the vehicle body to tilt forwards to ensure that the vehicle lamp points to the ground ₁ And D ₂ Respectively have a value range of [0.85,0.95 ]]And [1.05,1.1]；

If θ ∈ [ D ] ₁ θ _min ,D ₂ θ _max ]The system runs normally and does not report faults; if theta is greater than theta<D ₁ θ _min The system sends a fault signal indicating that the direction of the vehicle lamp deviates from the safe track, and whether the response of the electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if theta is greater than theta>D ₂ θ _max And the system sends a fault signal indicating that the longitudinal posture of the vehicle body is abnormal, and at the moment, whether communication valves of the four air bag inflation/deflation processes are normally opened and/or closed and whether an over-inflation and/or over-deflation phenomenon exists or not need to be overhauled.

Preferably, the step of detecting the vehicle body roll angle fault is as follows:

according to the displacement z of the vehicle body at the four suspensions _bi And calculating to obtain the roll angle of the vehicle body

Comprises the following steps:

wherein B is the vehicle wheelbase;

obtaining the roll angle at rest according to the change of the roll attitude of the vehicle body

Corresponding limit variation range is

The roll angle at which the vehicle is travelling pickup and pick up>

The corresponding limit change range is->

H ₁ And H ₂ Respectively in the roll angle>

Two stable correction coefficients of (a); set up H ₁ And H ₂ Are respectively in the value ranges of [1.02,1.08 ]]And [0.90,0.98]Thereby ensuring that the limit variation range of the vehicle body roll when the vehicle runs is smaller than the limit variation range of the roll angle when the vehicle is at rest

If it is not

The system runs normally without reporting faults; if->

The system sends a vehicle body left side inclination fault signal, and whether the response of a left side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if it is used

The system sends a vehicle body right side inclination fault signal, and whether the response of a right side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected.

Preferably, the detecting step of the vehicle body side kneeling function fault comprises the following steps:

considering the kneeling function margin of the vehicle body side

And &>

It is calculated according to the limit height of the spring inflation and deflation, and then the following equation is given:

in the formula, h _{i_lim_h} And h _{i_lim_l} The maximum height and the minimum height corresponding to the corresponding springs are respectively set;

is to a minimum roll angle>

The vehicle body side kneeling function margin for correction>

Is for the maximum side inclination angle->

Correcting the kneeling function allowance of the vehicle body side;

defining the variation range of kneeling limit of the vehicle body side as

In the function of kneeling on the side of the vehicle, if

Failure is not reported; if +>

Or->

The fault is not reported, but a side kneeling function starting command signal is synchronously sent at the moment; if->

The system sends a lateral safety fault signal of the vehicle body, and at the moment, the front and rear communicating valves are opened, and the active suppression control effect of the vehicle body posture is realized through the self-balancing of gas among different airbags; wherein +>

Preferably, the control isThe method for detecting the system hardware fault comprises the following steps: in the process of inflation/deflation, whether the controller has signal feedback or not is detected according to the control instruction; if the controller has signal response, the fault is not reported; if the controller does not have signal response, detecting the size of the bus load rate eta, and if the bus load rate eta is more than or equal to 75 percent, sending a fault signal that the bus load is too high by the system; if the bus load rate eta<75%, the control current I of the air pump motor is continuously detected _c According to the rated operating current I _A If I is _c ∈[0.5I _A ,1.2I _A ) Failure is not reported; if I _c <0.5I _A The system sends a bus line fault signal; if I _c ≥1.2I _A The system sends a fault signal of the air pump motor; and after the inflation and deflation are finished, carrying out fixed height dynamic adjustment fault detection according to a static self-balancing fault detection method.

Preferably, in the adaptive height dynamic adjustment mode, the suspension dynamic ideal height calculation method includes: the controller calculates the dynamic ideal height position h of the vehicle in real time according to the environmental road excitation and the vehicle state _DI (ii) a At this time, the dynamic ideal height position h of the vehicle _DI And its dynamic error h _Derr The calculation method is as follows:

wherein A is the cross-sectional area of the balloon and P _ti And P _I Respectively the pressure when the electromagnetic valve is closed and after the gas in the air bag is balanced, n is a gas index, and the value range is [1,1.38 ]]，V ₀ Is the initial volume of the balloon, h _ti The height change value of the suspension at the current moment;

and the pressure P after the gas inside the air bag is dynamically balanced _DI The calculation formula of (c) is:

in the formula, P ₀ For initiating the air bagPressure intensity, P _C And V _C Pressure and volume changes in the air bag change process respectively;

in an ideal state, the air bag is approximated to be a cylinder, so that the cross-sectional area A of the air bag is approximated according to a fixed value; but the actual balloon volume is not cylindrical, and a correction calculation is performed thereon as follows:

wherein H is the height of the air bag in the natural state and D ₁ And D ₂ The section diameters of the lower end and the upper end of the air bag respectively, and psi is a curved surface correction coefficient of the air bag and is determined through experimental tests.

Preferably, the step of detecting a dynamic adjustment time fault comprises: in the multiple adjustment processes of the system, the time interval delta T between every two adjustments needs to satisfy the following condition:

in the formula, T _O And T _I A complete deflation and inflation cycle for the air bag respectively; otherwise, the system sends out a fault signal of frequent switching of the air pump, at the moment, the relay is forcibly closed, and the vehicle height adjusting process is forcibly interrupted;

and after the inflation and deflation are finished, carrying out self-adaptive height dynamic adjustment fault detection according to a static self-balancing fault detection method.

Preferably, the step of detecting the loop temperature rise fault comprises: when the air pump motor works normally, the work W done by the resistance R in the loop _A Comprises the following steps:

W _A ＝I _A U _A T

in the formula of U _A The rated voltage is the rated voltage when the air pump works normally, and T is the working duration;

the resistance R in the circuit increases with the temperature, so the work W actually performed _S Comprises the following steps:

wherein C is the temperature coefficient of resistance, t ₁ And t ₂ The temperature of the resistance value R at the initial moment and the current moment respectively;

defining a temperature rise proportion coefficient psi, then:

if psi is less than or equal to 1.45, the system works normally and does not report faults; if psi is greater than 1.45, the system sends out abnormal temperature rise fault warning signal, at this time, the relay is closed until psi is less than or equal to 1.45.

Has the beneficial effects that:

1. according to the method, aiming at different vehicle height adjusting processes, through fault detection in three modes (a static self-balancing mode, a fixed height dynamic adjusting mode and a self-adaptive height dynamic adjusting mode), online detection of the air suspension system and vehicle height adjusting fault diagnosis under multiple parameters and multiple working conditions can be realized, so that operation reference can be provided for a driver, effective reference can be provided for further control optimization, and a reference can be provided for active intervention of a control system; the static self-balancing fault detection realizes system diagnosis under a static condition through suspension height fault detection, air bag pressure fault detection, vehicle body pitch angle and side inclination angle fault detection and vehicle body side kneeling function fault detection; the fixed height dynamic adjustment fault detection realizes the system diagnosis of the fixed gear adjustment process by calculating the ideal height of the suspension and controlling the hardware fault detection of the system; and the self-adaptive height dynamic adjustment fault detection realizes system diagnosis under dynamic adjustment through suspension ideal dynamic height calculation, loop temperature rise fault detection and dynamic adjustment time fault detection.

2. The suspension height fault detection in the invention detects the suspension height in a static state according to the collected sensor and vehicle state dataFault diagnosis is carried out according to the ideal height position h of the vehicle _I And a height tolerance value h _err The height positions of the four suspensions are subjected to fault detection respectively, so that the on-line diagnosis of the vehicle height adjustment fault under multiple parameters and multiple working conditions is facilitated, and effective early warning and control reference are provided for a controller and a driver.

3. According to the air bag pressure fault detection method, the pressure intensities in the four air bags are subjected to fault detection respectively according to the acquired sensor and vehicle state data and tolerance ranges corresponding to the internal pressure and the pressure change rate of the air bags, so that the online diagnosis of vehicle height adjustment faults under multiple parameters and multiple working conditions is further facilitated, and effective early warning and control reference are provided for a controller and a driver.

4. The vehicle body pitch angle fault detection method is based on suspension height fault detection and airbag pressure fault detection, the pitch angle of a vehicle body can be calculated by utilizing suspension displacement, the vehicle wheel base and the wheel base, fault diagnosis of the whole vehicle body attitude (pitch angle) in a static state can be further realized according to the corresponding limit change range, and vehicle height adjustment fault online diagnosis under multiple parameters and multiple working conditions is further facilitated, so that effective early warning and control reference are provided for a controller and a driver; meanwhile, the system parameters in the dynamic adjustment process can be dynamically corrected.

5. The hardware fault detection of the control system can firstly determine the dead zone adjusting range, calculate the ideal fixed height position of the suspension in the adjusting process and allow the error value in the dynamic adjusting process of the fixed height of the vehicle; on the basis, fault detection is carried out on the communication process of the controller according to the bus load rate and the control current; and after the system finishes inflating and deflating, further performing fault diagnosis according to the vehicle height adjusting process in the vehicle static state.

6. In the method for calculating the dynamic ideal height of the suspension, the dynamic change of the cross section area of an air bag in the vehicle height adjusting process is considered in the vehicle self-adaptive height dynamic adjusting process, and the position of the ideal dynamic height of the vehicle, the dynamic error and the dynamic gas balance pressure are required to be calculated at first, so that fault diagnosis can be carried out according to the vehicle height adjusting process in the vehicle static state.

Drawings

Fig. 1 is a schematic view of the composition of an air suspension system.

Fig. 2 is a schematic view of the height adjustment fault diagnosis process of the vehicle based on the air suspension system.

Detailed Description

The invention is described in detail below by way of example with reference to the accompanying drawings.

The embodiment provides a vehicle height adjustment fault diagnosis method based on an air suspension system, which can realize system state online detection and fault diagnosis under static and dynamic running conditions of a vehicle, so that the driving experience of a driver can be further optimized, and effective reference and basis are provided for comprehensive optimization of system performance.

When the vehicle runs under different working conditions, the dynamic response of the system of the vehicle is dynamically changed along with the actual working conditions, and by utilizing the collected system state data, on one hand, the fluctuation and the change condition of the environment can be reflected, and on the other hand, the state detection of the system can be carried out according to the state fluctuation, so that the system stability and the subsystem fault state in the running process of the vehicle can be obtained in real time.

As shown in fig. 2, the method is divided into three parts, namely, a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and an adaptive height dynamic adjustment fault detection method;

1. static self-balancing fault detection method (i.e. vehicle height adjustment fault diagnosis method in vehicle stationary state)

Step 1.1: detecting suspension height faults

Opening a front communicating valve to enable the front left air bag and the front right air bag to be communicated with each other, and opening a rear communicating valve to enable the rear left air bag and the rear right air bag to be communicated with each other; after the gas self-balancing setting time (preferably 4-6 s), closing the front and rear communicating valves, and detecting the height positions of the four air suspensions corresponding to the front left, the front right, the rear left and the rear right to be h respectively _fl 、h _fr 、h _rl And h _rr ；

According to the ideal height position h of the vehicle _I And a height tolerance value h _err The expected value range of the vehicle height can be calculated as [ h [ ] _I -h _err ,h _I +h _err ](ii) a If h is _i (i＝fl,fr,rl,rr)∈[h _I -h _err ,h _I +h _err ]The air suspension system operates normally, and the fault of the air suspension system is not reported; if h is _i (i＝fl,fr,rl,rr)

[h _I -h _err ,h _I +h _err ]The air suspension system sends a suspension height abnormal fault signal, and at the moment, the step 1.2 needs to be carried out to examine whether the structures of the four air bags and the pipeline tightness are intact; />

Step 1.2: detecting air bag pressure failure

Assuming that the sampling step of the external data acquisition device is Δ T, the corresponding sampling frequency is f _E =1 Δ T, at the detection frequency f _E The pressure inside the four air bags is monitored in a circulating way, and the pressure P inside the ith air bag can be obtained according to the inherent characteristics of the ith (i = fl, fr, rl, rr) air bag _i And rate of change of pressure

Respectively correspond to [ P ] _imin ,P _imax ]And &>

Wherein, in the time range of 0-T, the sampling number is N _E = T/Delta T, can get the ith air bag

And &>

The specific calculation method is as follows:

in the formula, P _ij And P _i(j+1) Respectively is the internal air pressure of the ith air bag under the sampling of the jth and j +1 times, and Λ is a bus delay coefficient, and the value of the lambda is related to the bus load rate eta, namely the following relation is provided:

if the internal pressure P of the ith air bag _i ∈[P _imin ,P _imax ]If the pressure in the air bag is normal, the air suspension system does not report faults; if it is not

The air suspension system signals a suspension pressure failure in which a further detection of the rate of change of the pressure inside the airbag is required>

If it is used

The pressure change in the ith air bag is normal, and the air suspension system does not report faults; if->

The pressure change in the ith air bag is abnormal, and the air suspension system sends a gas path sealing fault signal; if->

If the pressure change in the ith air bag is abnormal, the air suspension system sends an air bag structural damage fault signal, and the step 1.3 is carried out;

step 1.3: detecting vehicle body pitch angle faults

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

wherein a and b are the distances from the center of mass of the vehicle to the front axle and the rear axle, respectively;

according to the change of the pitching attitude of the vehicle body movement, the limit change range [ theta ] corresponding to the pitching angle theta when the vehicle is static can be obtained _min ,θ _max ]The limit variation range corresponding to the pitch angle θ when the vehicle is traveling corresponds to [ D [ ] ₁ θ _min ,D ₂ θ _max ](ii) a Wherein D is ₁ And D ₂ Two dynamic correction coefficients of a pitch angle theta are respectively; according to the requirement of the air suspension system on the fault-tolerant space in the limiting inflation/deflation process, the vehicle body is slightly inclined forwards to ensure that the vehicle lamp points to the ground, so that the driver can see the road condition clearly, and D is arranged ₁ And D ₂ Are respectively in the value ranges of [0.85,0.95 ]]And [1.05,1.1]；

If θ ∈ [ D ] ₁ θ _min ,D ₂ θ _max ]The system runs normally and does not report faults; if theta is greater than theta<D ₁ θ _min The system sends a fault signal indicating that the direction of the vehicle lamp deviates from the safe track, and whether the response of the electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if theta is greater than theta>D ₂ θ _max And the system sends a fault signal indicating that the longitudinal posture of the vehicle body is abnormal, and at the moment, whether communication valves of the four air bag inflation/deflation processes are normally opened and/or closed and whether an over-inflation and/or over-deflation phenomenon exists or not need to be overhauled.

In static self-balancing fault detection, in order to ensure the stability of a vehicle, the following steps are carried out:

step 1.4: detecting vehicle body roll angle faults

In order to ensure that the vehicle is smooth, the displacement z of the vehicle body at the four suspensions is used as a basis _bi (i = fl, fr, rl, rr), the roll angle of the vehicle body can be calculated

Comprises the following steps:

in the formula, B is a vehicle wheel base;

the roll angle at rest can be obtained according to the change of the roll posture of the vehicle body

Corresponding limit range->

The roll angle at which the vehicle is travelling pickup and pick up>

The corresponding limit change range is->

H ₁ And H ₂ Respectively in the roll angle>

Two stable correction coefficients of (a); in order to ensure that the rollover accident caused by the overlarge rolling degree of the vehicle body is prevented under the limit rolling condition of the posture of the vehicle body, H ₁ And H ₂ The value ranges of (1) to (1.02) and (1.08) respectively]And [0.90,0.98]Thus, the limit change range of the vehicle body rolling during the vehicle running is ensured to be slightly smaller than the limit change range of the roll angle at rest->

If it is not

The system runs normally without reporting faults; if->

The system sends a vehicle body left side inclination fault signal, and whether the response of a left side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if it is not

The system sends a vehicle body right side inclination fault signal, and whether the response of a right side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected.

Step 1.5: detecting vehicle body side kneeling function fault

Considering the body side kneeling function allowance

And &>

(/>

Is based on the minimum roll angle->

The vehicle body side kneeling function margin for correction>

Is for the maximum side inclination angle->

The corrected body kneeling function margin) calculated from the limit heights of the spring charge and discharge, the following equation is given: />

In the formula, h _{i_lim_h} And h _{i_lim_l} (i = fl, fr, rl, rr) are the extreme maximum and minimum heights, respectively, for the respective springs;

defining the variation range of kneeling limit of the vehicle body side as

In the function of kneeling on the side of the vehicle, if

The system runs normally without reporting faults; if->

Or->

The system normally runs, the fault is not reported, but a side kneeling function starting command signal is synchronously sent at the moment; if->

The system sends a lateral safety fault signal of the vehicle body, at the moment, a front communicating valve and a rear communicating valve need to be opened, and the active suppression control effect of the vehicle body posture is realized through the self-balancing of gas among different airbags; wherein the content of the first and second substances,

2. fixed height dynamic adjustment fault detection method

In the vehicle advancing process, a driver can adjust the fixed height of the vehicle body in the ascending/descending process according to the environmental change, and the controller provides a control signal for the air pump motor according to the ascending/descending instruction, so that the dynamic adjustment of the fixed height in the vehicle advancing process is realized;

step 2.1: calculating ideal fixed height of suspension and adjusting fixed height of vehicle by lifting

The actual air suspension height will fluctuate due to road excitation; at this time, to prevent the channelThe air pump is repeatedly switched on and off during the air charging/discharging process due to the influence of road excitation, thereby setting the dead zone adjusting range of the height of the air suspension to be h _{dead_min} ,h _{dead_max} ](ii) a At this time, according to the preset target height h of the vehicle _g The ideal height position h of the air suspension in the lifting adjustment process can be obtained _I And an allowable error value h _err The calculation method is as follows:

wherein, omega is a time lag coefficient,

and &>

Respectively sprung mass velocity, unsprung mass velocity and road excitation variation velocity;

thereby adjusting the range [ h ] according to the dead zone _{dead_min} ,h _{dead_max} ]Ideal height position h _I And an allowable error value h _err Determination of [ h _I -|h _err |-h _{dead_min} ,h _I +|h _err |+h _{dead_min} ](ii) a Because the road excitation can cause the vibration of the air spring, in order to avoid the frequent opening and closing of the electromagnetic valve caused by the normal vibration and prolong the service life of the system, the system is in [ h ] _I -h _{dead_min} ,h _I +h _{dead_min} ]Within range unresponsive, and within 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 inner control system acts and controls the air bag to inflate/deflate by controlling the switch of the electromagnetic valve so as to adjust the height of the vehicle.

Step 2.2: detecting control system hardware faults

In the process of inflation/deflation, whether the controller has signal feedback or not is detected according to the control instruction; if the controller has a signalResponding, the system normally operates, and faults are not reported; if the controller does not have signal response, the size of the bus load rate eta needs to be detected, and if the bus load rate eta is larger than or equal to 75%, the system sends a fault signal that the bus load is too high; if the bus load rate eta<75%, the control current I of the air pump motor is continuously detected _c According to the rated operating current I _A Ensuring the control current I of the air pump motor _c In the case of either too small or too large a valve (too small a battery valve cannot open and too large a solenoid valve burns out), if I _c ∈[0.5I _A ,1.2I _A ) The system runs normally and does not report faults; if I _c <0.5I _A The system sends a bus line fault signal; if I _c ≥1.2I _A The system sends a fault signal of the air pump motor; and after the inflation and deflation are finished, carrying out fixed height dynamic adjustment fault detection according to the sequence shown by the static self-balancing fault detection method.

3. Self-adaptive height dynamic adjustment fault detection method

Step 3.1: calculating ideal dynamic height of suspension and adjusting adaptive height of vehicle according to ideal dynamic height

In this mode (adaptive altitude dynamic adjustment mode), the controller calculates the ideal dynamic altitude position h of the vehicle in real time based on the environmental road excitation and the vehicle state _DI So as to realize good passing performance and smoothness of the vehicle under complex conditions; at this time, the ideal dynamic height position h of the vehicle _DI And its dynamic error h _Derr The calculation method is as follows:

wherein A is the cross-sectional area of the balloon and P _ti And P _I The pressure intensity when the electromagnetic valve is just closed and after the gas in the air bag is balanced respectively, n is a gas index, and the value range is [1,1.38 ]]，V ₀ Is the initial volume of the balloon, h _ti The height change value of the suspension at the current moment;

and the pressure intensity after the gas inside the air bag is dynamically balancedP _DI The calculation formula of (2) is as follows:

in the formula, P ₀ Is the initial pressure of the bladder, P _C And V _C Respectively the pressure and volume changes in the air bag changing process;

in an ideal state, the air bag is approximated to be an ideal cylinder, so that the cross-sectional area A of the air bag is approximated according to a fixed value; however, the actual balloon volume is not a strict cylinder and further calibration calculations are needed, as follows:

wherein H is the height of the airbag in the natural state (the natural state refers to the state when the airbag is not compressed, and the shape of the airbag is similar to a circular truncated cone), D ₁ And D ₂ The section diameters of the lower end and the upper end of the air bag respectively, and psi is a curved surface correction coefficient of the air bag and can be determined through experimental tests;

this results in a dead band adjustment range [ h ] set in step 2.1 _{dead_min} ,h _{dead_max} ]Ideal height position h in self-adaptive height dynamic regulation fault detection method _DI And an allowable error value h _Derr The lifting adjustment of the vehicle height can be carried out according to the step one, and the hardware fault detection of the control system is carried out according to the step described in the step 2.2;

step 3.2: detecting loop temperature rise faults

The air pump motor needs to be switched on and off through the closing of the relay, the control current of the relay is large, and the relay is possibly damaged due to abnormal temperature rise in the self-adaptive repeated adjustment process, so that the service life of a device and the reliability of a system are influenced; therefore, the system safety needs to be dynamically monitored by detecting the relay loop;

when the air pump motor works normallyWork W done by the resistance R in the loop _A Comprises the following steps:

W _A ＝I _A U _A T

in the formula of U _A The rated voltage is the rated voltage when the air pump works normally, and T is the working duration;

the resistance R in the circuit increases with the temperature, so the work W actually performed _S Comprises the following steps:

wherein C is the temperature coefficient of resistance, t ₁ And t ₂ The temperature of the resistance value R at the initial moment and the current moment respectively;

defining a temperature rise proportion coefficient psi, then:

if psi is less than or equal to 1.45, the system works normally and does not report faults; if Ψ is greater than 1.45, the system sends out an abnormal temperature rise fault warning signal, and the relay is closed until Ψ is less than or equal to 1.45; wherein, the threshold value of 1.45 is obtained by back calculation according to the normal current value of the component.

Step 3.3: detecting dynamic adjustment time faults

The difference of the environmental road can lead to the need to adjust the height of the vehicle body repeatedly, but in order to avoid the sudden reduction of the service life of the system caused by frequent opening and closing, in the multiple adjustment process of the system, the time interval delta T between every two times of adjustment should meet the following conditions:

in the formula, T _O And T _I A complete deflation and inflation cycle for the air bag respectively; otherwise (i.e. the time interval deltat between each two adjustments does not satisfy the above condition), the system sends a failure message that the air pump is frequently switched on and offThe relay is forcibly closed at the moment, and the vehicle height adjusting process is forcibly interrupted;

and after the inflation and deflation are finished, carrying out self-adaptive height dynamic adjustment fault detection according to a static self-balancing fault detection method.

If the system has no fault signal sent out after fault diagnosis in three height adjustments corresponding to the static self-balancing fault detection method, the fixed height dynamic adjustment fault detection method and the self-adaptive height dynamic adjustment fault detection method, the system at the moment is indicated to work normally, otherwise, a driver needs to carry out driving and debugging of the vehicle after troubleshooting according to specific fault alarm information.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A vehicle height adjustment fault diagnosis method based on an air suspension system, characterized by comprising: a static self-balancing fault detection method, a fixed height dynamic adjustment fault detection method and a self-adaptive height dynamic adjustment fault detection method; the static self-balancing fault detection method comprises the following steps: sequentially detecting a suspension height fault, an airbag pressure fault, a vehicle body pitch angle fault, a vehicle body side inclination angle fault and a vehicle body side kneeling function fault; the fixed height dynamic adjustment fault detection method comprises the following steps: calculating the ideal fixed height of the suspension, adjusting the fixed height of the vehicle in a lifting manner according to the ideal fixed height of the suspension, and detecting hardware faults of a control system; the self-adaptive height dynamic adjustment fault detection method comprises the following steps: calculating the ideal dynamic height of the suspension, adjusting the self-adaptive height of the vehicle according to the ideal dynamic height, detecting the temperature rise fault of the loop and detecting the time fault of dynamic adjustment.

2. The air suspension system based vehicle height adjustment fault diagnostic method of claim 1, wherein the step of suspension height fault detectionComprises the following steps: opening a front communicating valve to enable the front left air bag and the front right air bag to be communicated with each other, and opening a rear communicating valve to enable the rear left air bag and the rear right air bag to be communicated with each other; after the gas self-balancing setting time, closing the front and rear communicating valves, and detecting the height positions of four air suspensions corresponding to the front left, the front right, the rear left and the rear right as h respectively _fl 、h _fr 、h _rl And h _rr ；

According to the ideal height position h of the vehicle _I And a height tolerance value h _err And calculating to obtain the expected value range of the vehicle height as [ h _I -h _err ,h _I +h _err ](ii) a If h is _i ∈[h _I -h _err ,h _I +h _err ]If yes, the fault is not reported; if it is not

The air suspension system sends a suspension height abnormal fault signal, and then the step of air bag pressure fault detection is carried out; where i = fl, fr, rl, rr.

3. The air suspension system-based vehicle height adjustment fault diagnosis method according to claim 2, wherein the step of air bag pressure fault detection is:

assuming that the sampling step of the external data acquisition device is Δ T, the corresponding sampling frequency is f _E =1/Δ T in terms of detection frequency f _E The pressure in the four air bags is monitored circularly, and the pressure P in the ith air bag is obtained according to the inherent characteristic of the ith air bag _i And rate of change of pressure

Respectively is [ P ] _imin ,P _imax ]And &>

Wherein, in the time range of 0-T, the sampling number is N _E = T/Delta T, obtaining i-th air bag

And &>

The calculation method is as follows:

in the formula, P _ij And P _i(j+1) The internal air pressure of the air bag under the sampling of the ith air bag at the j th time and the j +1 th time is respectively, lambda is a bus delay coefficient, and the value of Lambda is related to the bus load rate eta, namely the following relation is provided:

if the internal pressure P of the ith air bag _i ∈[P _imin ,P _imax ]The air suspension system does not report the fault; if it is not

The air suspension system sends a suspension pressure failure signal, in which case the rate of change of the pressure inside the airbag is further detected>

If it is not

The air suspension system does not report a fault; if->

The air suspension system sends a gas path tightness fault signal; if->

The air suspension system sends out an air bag structural damage fault signal and the step of detecting the pitch angle fault of the vehicle body is transferred.

4. The air suspension system based vehicle height adjustment fault diagnosis method according to claim 3, wherein the body pitch angle fault detection step is:

according to the displacement z of the vehicle body at the four suspensions _bi And calculating to obtain a vehicle body pitch angle theta as follows:

wherein a and b are the distances from the center of mass of the vehicle to the front axle and the rear axle, respectively;

obtaining the limit change range [ theta ] corresponding to the pitch angle theta when the vehicle is static according to the change of the pitching attitude of the vehicle body _min ,θ _max ]The limit variation range corresponding to the pitch angle θ when the vehicle is traveling is [ D ] ₁ θ _min ,D ₂ θ _max ](ii) a Wherein D is ₁ And D ₂ Two dynamic correction coefficients of a pitch angle theta are respectively; setting D according to the fault-tolerant space requirement of the limit inflation/deflation process of the air suspension system, and simultaneously enabling the vehicle body to tilt forwards to ensure that the vehicle lamp points to the ground ₁ And D ₂ Are respectively in the value ranges of [0.85,0.95 ]]And [1.05,1.1]；

If θ ∈ [ D ] ₁ θ _min ,D ₂ θ _max ]The system runs normally and does not report faults; if theta is greater than theta<D ₁ θ _min The system sends a fault signal indicating that the direction of the vehicle lamp deviates from the safe track, and whether the response of the electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if theta is greater than theta>D ₂ θ _max And the system sends a fault signal indicating that the longitudinal posture of the vehicle body is abnormal, and at the moment, whether communication valves of the four air bag inflation/deflation processes are normally opened and/or closed and whether an over-inflation and/or over-deflation phenomenon exists or not need to be overhauled.

5. The air suspension system based vehicle height adjustment fault diagnosis method according to claim 4, wherein the vehicle body roll angle fault detection step is:

according to the displacement z of the vehicle body at the four suspensions _bi Calculating to obtain the roll angle of the vehicle body

Comprises the following steps:

in the formula, B is a vehicle wheel base;

obtaining the roll angle at rest according to the change of the roll attitude of the vehicle body

Corresponding limit variation range is

The roll angle at which the vehicle is travelling pickup and pick up>

The corresponding limit change range is->

H ₁ And H ₂ Respectively in the roll angle>

Two stable correction coefficients of (a); set up H ₁ And H ₂ The value ranges of (1) to (1.02) and (1.08) respectively]And [0.90,0.98]Thereby ensuring that the limit change range of the vehicle body rolling when the vehicle runs is smaller than the limit change range of the roll angle when the vehicle is static

If it is not

The system runs normally without reporting faults; if->

The system sends a vehicle body left side inclination fault signal, and whether the response of a left side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected; if it is not

The system sends a vehicle body right side inclination fault signal, and whether the response of a right side electromagnetic valve is normal or not in the charging/discharging process of the system needs to be detected.

6. The air suspension system based vehicle height adjustment fault diagnosis method of claim 5 wherein the step of body side kneeling function fault detection is:

considering the body side kneeling function allowance

And &>

It is calculated according to the limit height of the spring inflation and deflation, and then the following equation is given:

in the formula, h _{i_lim_h} And h _{i_lim_l} The maximum height and the minimum height corresponding to the corresponding springs are respectively set;

is to the smallest sideInclination angle>

The vehicle body side kneeling function margin for correction>

Is for the maximum side inclination angle->

Correcting the kneeling function allowance of the vehicle body side;

defining the variation range of kneeling limit of the vehicle body side as

In the function of kneeling on the side of the vehicle, if

Failure is not reported; if +>

Or>

The fault is not reported, but a side kneeling function starting command signal is synchronously sent at the moment; if it is not

The system sends a lateral safety fault signal of the vehicle body, the front and rear communicating valves are opened at the moment, and the active suppression control effect of the vehicle body posture is realized through the self-balancing of gas among different airbags; wherein +>

7. The air suspension system-based vehicle height adjustment fault diagnosis method according to any one of claims 1-6, wherein the control system hardware fault detection step is: in the process of inflation/deflation, whether the controller has signal feedback or not is detected according to the control instruction; if the controller has signal response, the fault is not reported; if the controller does not have signal response, detecting the size of the bus load rate eta, and if the bus load rate eta is more than or equal to 75 percent, sending a fault signal that the bus load is too high by the system; if the bus load rate eta<75%, the control current I of the air pump motor is continuously detected _c According to the rated operating current I _A If I is _c ∈[0.5I _A ,1.2I _A ) Failure is not reported; if I _c <0.5I _A The system sends a bus line fault signal; if I _c ≥1.2I _A The system sends a fault signal of the air pump motor; and after the inflation and deflation are finished, carrying out fixed height dynamic adjustment fault detection according to a static self-balancing fault detection method.

8. The air suspension system based vehicle height adjustment fault diagnosis method of claim 7, wherein in the adaptive height dynamic adjustment mode, the suspension dynamic ideal height calculation method is: the controller calculates the dynamic ideal height position h of the vehicle in real time according to the environmental road excitation and the vehicle state _DI (ii) a At this time, the dynamic ideal height position h of the vehicle _DI And its dynamic error h _Derr The calculation method of (A) is as follows:

wherein A is the cross-sectional area of the balloon and P _ti And P _I The pressure intensity when the electromagnetic valve is closed and after the gas in the air bag is balanced, n is a gas index, and the value range is [1,1.38 ]]，V ₀ Is the initial volume of the balloon, h _ti The height change value of the suspension at the current moment;

and the pressure P after the gas inside the air bag is dynamically balanced _DI The calculation formula of (c) is:

in the formula, P ₀ Is the initial pressure of the bladder, P _C And V _C Pressure and volume changes in the air bag change process respectively;

in an ideal state, the air bag is approximated to be a cylinder, so that the cross-sectional area A of the air bag is approximated according to a fixed value; but the actual balloon volume is not cylindrical, and a correction calculation is performed thereon as follows:

wherein H is the height of the air bag in the natural state, D ₁ And D ₂ The section diameters of the lower end and the upper end of the air bag respectively, and psi is a curved surface correction coefficient of the air bag and is determined through experimental tests.

9. The air suspension system based vehicle height adjustment fault diagnostic method according to claim 8, wherein the step of detecting a dynamic adjustment time fault comprises: in the process of adjusting the system for multiple times, the time interval delta T between every two times of adjustment needs to satisfy the following condition:

in the formula, T _O And T _I A complete deflation and inflation cycle for the air bag respectively; otherwise, the system sends out a fault signal of frequent switching of the air pump, at the moment, the relay is forcibly closed, and the vehicle height adjusting process is forcibly interrupted;

and after the inflation and deflation are finished, carrying out self-adaptive height dynamic adjustment fault detection according to a static self-balancing fault detection method.

10. The air suspension system-based vehicle height adjustment fault diagnosis method according to claim 7, wherein the step of detecting a loop temperature rise fault comprises: when the air pump motor works normally, the work W done by the resistance R in the loop _A Comprises the following steps:

W _A ＝I _A U _A T

in the formula of U _A Is the rated voltage when the air pump works normally, and T is the working duration;

the resistance R in the loop increases with the temperature, so the work W is actually done _S Comprises the following steps:

/>

wherein C is the temperature coefficient of resistance, t ₁ And t ₂ The temperature of the resistance value R at the initial moment and the current moment respectively;

defining a temperature rise proportion coefficient psi, then:

if psi is less than or equal to 1.45, the system works normally and does not report faults; if Ψ >1.45, the system issues an abnormal temperature rise fault warning signal, at which time the relay closes until Ψ ≦ 1.45.

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