CN101581659A - Tyre-pavement maximum attachment coefficient test method - Google Patents

Abstract

The invention relates to a tyre-pavement maximum attachment coefficient test method. The method uses a test device which comprises an information acquisition unit for acquiring information of an automobile, a control unit preset with a nominal curve and used for processing information input by the information acquisition unit and outputting tyre-pavement maximum attachment coefficient, and a display device for displaying the output of the control unit; the test method comprises the following steps: 1) acquiring the speed of the automobile; 2) acquiring the wheel slip rate lambda of the automobile; 3) acquiring the longitudinal driving force or the longitudinal braking force of the wheels; 4) acquiring the vertical load of the wheels; 5) acquiring the wheel tyre-pavement maximum attachment coefficient mu; 6) acquiring the wheel slip rate of the current automobile; 7) acquiring the (lamba0, mu0) of the wheel slip rate K of the current automobile corresponding to the step 6); 8) acquiring the current maximum pavement attachment coefficient mu<max>; 9) carrying out filtering processing on the mu<max> obtained in step 8) and displaying by the display device. The method of the invention is efficient and precise and can on-line display the tyre-pavement maximum attachment coefficient in real time.

Description

A kind of tire-road surface maximum grip coefficient method of testing

Technical field

The present invention relates to a kind of method of testing, especially relate to a kind of tire-road surface maximum grip coefficient method of testing.

Background technology

The Vehicle Stability Control technology has now become one of research emphasis of auto industry circle guaranteeing to have very significant meaning aspect the vehicle active safety.Doughnut-road surface maximum grip coefficient μ _MaxThe important information that can provide vehicle to keep stable maximum allowance is the important reference of design vehicle Stability Control device parameter.Utilize vehicle-mounted common sensor to tire-road surface maximum grip coefficient μ _MaxCarrying out real-time online observation, is that intact stability is controlled one of needed gordian technique.

At present, carry out tire-road surface maximum grip coefficient μ based on vehicle-mounted common sensor _MaxA kind of method of observation is: at first, by measuring the wheel speed and the speed information of tire, calculate the slip rate λ of tire; By the vertical line load of driving on the tire/braking moment and tire, calculate the adhesive rate μ of tire again; At last, organize by gathering (λ, μ) data point, the adherence curve on the current road surface of match under λ-μ coordinate system, and by judging that the fixed point on the curve obtains as front tyre-road surface maximum grip coefficient μ more _MaxAs seen, the accuracy of the current road surface of said method match adherence curve depends on that (λ, μ) what of data point will certainly influence μ like this _MaxThe real-time of observation.Another kind method is: the current (λ that will collect, μ) the corresponding nominal dot of same slip rate λ compares on data point and some the nominal curves, by comparing the similarity of actual observation point and corresponding nominal dot, the method in conjunction with fuzzy reasoning obtains actual tire-road surface maximum grip coefficient μ again _MaxBut, in order in universe, to observe μ _MaxNeed obtain some the nominal curves under (4-5 bar usually) different road surfaces by the off-line experiment, this need expend a large amount of energy and times, in addition, under different road surfaces, same slip rate λ corresponding physical meaning is different, and the physical significance that these data points are compared is unintelligible, and the result who obtains is also inaccurate.

Summary of the invention

At the problems referred to above, the purpose of this invention is to provide a kind of efficient, accurate tire-road surface maximum grip coefficient method of testing that tire-road surface maximum grip coefficient also can onlinely in real time be provided.

For achieving the above object, the present invention takes following technical scheme: a kind of tire-road surface maximum grip coefficient method of testing, and this method is used a kind of proving installation, and this device comprises: one is used to gather the information acquisition unit of automobile information; The one default control module handling described information acquisition unit input information and export tire-road surface maximum grip coefficient of being used to that is equipped with the nominal curve; And display device that shows described control module output; Described method of testing comprises the steps: 1) filtering operation handles rotating speed, steering wheel angle input, automobile barycenter longitudinal acceleration and the transverse acceleration of the tire record, to obtain automobile speed; 2) according to speed information that obtains in the step 1) and the wheel speed information that records, to obtain automotive wheel slip rate λ; 3) braking clamp body that records of calculation process and wheel contact area, caliper acting force equivalent point are to distance and the driving torque on the wheel or the braking moment of wheel center, to obtain vertical driving force of wheel or the vertical damping force of wheel; 4) between the barycenter longitudinal acceleration that records of calculation process, barycenter transverse acceleration, complete vehicle quality, automobile front axle distance, vehicle front to the distance of barycenter, automobile hind axle to barycenter between wheelspan, automobile back wheel wheelspan and automobile barycenter to the distance on road surface, to obtain the wheel vertical load; 5) according to step 3) and 4) in the vertical driving force of wheel or vertical damping force of wheel and the wheel vertical load that obtain, to obtain wheel tyre-coefficient of road adhesion μ; 6) according to step 2) and 5) in the current wheel slip λ that obtains and as front tyre-coefficient of road adhesion μ, to obtain current doughnut slippage slope; 7) on described nominal curve, utilize mapping relations to obtain the (λ of current doughnut slippage slope K in the corresponding step 6) ₀, μ ₀); 8) will (λ, μ) corresponding as front tyre-road surface maximum grip coefficient μ _MaxWith (λ ₀, μ ₀) corresponding tire-road surface maximum grip coefficient μ _Max0Compare, to obtain current maximum coefficient of road adhesion μ _Max9) μ to obtaining by step 8) _MaxCarry out Filtering Processing and on described display device, show.

Described control module utilizes the theoretical off-line of normalization tire to obtain described nominal curve, tire on this nominal curve-road surface maximum grip coefficient μ _Max0=1.

The current maximum coefficient of road adhesion μ that described control module obtains described step 8) _MaxCarrying out the quadratic regression filtering operation handles.

The present invention is owing to take above technical scheme, it has the following advantages: 1, the adherence curve that has adopted the theoretical off-line of normalization tire to obtain on the nominal road surface owing to the inventive method (is called for short: the nominal curve), greatly reduced the off-line calibration workload of nominal curve, so the inventive method efficient height, saved the time, can real-time online have been measured by tire-road surface maximum grip coefficient.2, because the present invention has adopted the quadratic regression filtering operation based on forgetting factor that observed result has been carried out Filtering Processing, and forgetting factor also rationally chooses according to actual conditions, therefore improved the accuracy and the smoothness of tire-road surface maximum grip coefficient observation effectively.

Embodiment

Below in conjunction with embodiment, the present invention is described in detail.

The inventive method is used a kind of proving installation, this device comprises: one is used to gather the information acquisition unit of automobile information, one default is equipped with being used for process information collecting unit input information and exporting the control module of tire-road surface maximum grip coefficient of nominal curve, and the display device of an indicative control unit output.Wherein, information acquisition unit comprises wheel speed sensors, acceleration transducer, bearing circle torque sensor, steering wheel angle sensor, CAN bus and pressure of wheel braking cylinder sensor.The nominal curve is that control module utilizes the theoretical off-line of normalization tire to obtain, and on the nominal curve tire-road surface maximum grip coefficient μ _Max0=1.The inventive method comprises the steps:

1) the tire rotational speed ω that wheel speed sensors is recorded _i, the steering wheel angle input δ that records of bearing circle torque sensor _w, the automobile barycenter longitudinal acceleration a that records of acceleration transducer _xWith barycenter transverse acceleration a _yCarry out the Kalman filtering calculation process, to obtain automobile speed V _xWherein, the motor racing discrete state equations of Kalman filtering calculation process utilization comprises:

V _x(k+1)＝V _x(k)+a _xΔT+W _p (1)

rV _w(k)＝V _x(k)+W _m (2)

W _p＝V _yγΔT+W _a (3)

W _m＝ΔV+W′ _m (4)

ΔV＝λω _i (5)

ΔV＝λ/[(1+λ)ω _i] (6)

In the formula (1), V _x(k+1) be the k+1 speed of a motor vehicle constantly, V _x(k) be the k speed of a motor vehicle constantly, Δ T is the sampling time of proving installation, W _pIt is the error of proving installation.

In the formula (2), r is the doughnut radius, V _w(k) be k wheel wheel speed constantly, W _mBe the k speed of a motor vehicle and wheel speed poor constantly.

In the formula (3), V _yBe to turn to the speed of a motor vehicle, γ is the yaw velocity of automobile, W _aIt is the signal noise of acceleration transducer itself.

In the formula (4), W ' _mBe the signal noise of wheel speed sensors itself, Δ V is the poor of wheel speed and rotating speed.

Wheel speed and rotating speed was poor when formula (5) was the automobile driving; Formula (6) wheel speed and rotating speed poor when being automobile brake.Wherein i represents i wheel, i={1,2,3,4}.λ is the doughnut slip rate, and slip rate λ can be automobile longitudinal acceleration a _xWith wheel acceleration

The approximate value of difference.X, y and z represent vertical, the horizontal and vertical direction of automobile respectively.

2) according to the automobile speed V that tries to achieve in the step 1) _xWith the wheel i tire rotational speed ω that records _i, to obtain automotive wheel slip rate λ, its calculating formula is as follows:

$\mathrm{\&lambda;}=\frac{\mathrm{r\&omega;}-V_x}{\max (\mathrm{r\&omega;},V_x)}---\left(7\right)$

Max (r ω, V _x) refer to r ω and V _xBetween maximal value.

3) according to the braking clamp body that records and wheel contact area A, caliper acting force equivalent point to wheel center apart from driving torque on r ' and the wheel i or braking moment T _i, obtain the vertical driving force of wheel i or vertical damping force F _Xi:

When automobile is in driving condition, directly obtain the driving torque T of automotive wheel i by the CAN bus on the control unit of engine _i, vertical driving force F of wheel i then _XiFor:

$F_{\mathrm{xi}}=\frac{T_i}{r}---\left(8\right)$

When automobile is in on-position, at first pass through the pressure of wheel braking cylinder p of pressure of wheel braking cylinder sensor measurement tire _i, obtain automotive wheels braking moment T by following formula again _i, vertical damping force F of wheel i then _XiFor:

T _i＝p _wiAr′ (9)

$F_{\mathrm{xi}}=\frac{T_i}{r}---\left(10\right)$

4) according to the barycenter longitudinal acceleration a that records _x, barycenter transverse acceleration a _y, complete vehicle quality m, automobile front axle to barycenter apart from l _f, automobile hind axle to barycenter apart from l _r, wheelspan w between vehicle front _f, wheelspan w between automobile back wheel _rWith the distance h of automobile barycenter, obtain wheel vertical load F to the road surface _Zi, its calculating formula is as follows:

$F_{z1}=\frac{{\mathrm{mgl}}_r}{21}-\frac{{\mathrm{ma}}_{x}h}{21}-\frac{{\mathrm{ma}}_y{l}_{r}h}{l{w}_f}---\left(11\right)$

$F_{z2}=\frac{{\mathrm{mgl}}_r}{21}-\frac{{\mathrm{ma}}_{x}h}{21}-\frac{{\mathrm{ma}}_y{l}_{r}h}{{\mathrm{lw}}_f}---\left(12\right)$

$F_{z3}=\frac{{\mathrm{mgl}}_f}{21}+\frac{{\mathrm{ma}}_{x}h}{21}+\frac{{\mathrm{ma}}_y{l}_{f}h}{{\mathrm{lw}}_r}---\left(13\right)$

$F_{z4}=\frac{{\mathrm{mgl}}_f}{21}+\frac{{\mathrm{ma}}_{x}h}{21}-\frac{{\mathrm{ma}}_y{l}_{f}h}{{\mathrm{lw}}_r}---\left(14\right)$

5) according to step 3) and 4) in vertical driving force of the wheel of trying to achieve or the vertical damping force F of wheel _XiWith wheel vertical load F _Zi, obtain wheel tyre-coefficient of road adhesion μ, its calculating formula is as follows:

$\mathrm{\&mu;}=\frac{F_{\mathrm{xi}}}{F_{\mathrm{zi}}}---\left(15\right)$

6) according to step 2) and 5) in the current wheel slip λ that tries to achieve and as front tyre-coefficient of road adhesion μ, obtain current doughnut slippage slope K, the computing formula of K is as follows:

$K=\frac{\mathrm{\&mu;}}{\mathrm{\&lambda;}}---\left(16\right)$

7) on default nominal curve, utilize mapping relations to obtain the (λ of current doughnut slippage slope K in the corresponding step 6) ₀, μ ₀).

8) will (λ, μ) corresponding as front tyre-road surface maximum grip coefficient μ _MaxWith (λ ₀, μ ₀) corresponding tire-road surface maximum grip coefficient μ _Max0Compare, to obtain current maximum coefficient of road adhesion μ _Max: because identical tire has identical tyre skidding slope K on different road surfaces, promptly

$\frac{\mathrm{\&mu;}}{{\mathrm{\&mu;}}_0}=\frac{{\mathrm{\&mu;}}_{\max }}{{\mathrm{\&mu;}}_{\max 0}}---\left(17\right)$

Because tire-road surface maximum grip coefficient μ on the nominal curve _Max0=1, then work as the maximum grip coefficient μ on front tyre-road surface _MaxFor:

${\mathrm{\&mu;}}_{\max }=\frac{\mathrm{\&mu;}}{{\mathrm{\&mu;}}_0}---\left(18\right)$

9) control module adopts the maximum grip coefficient μ when front tyre-road surface of quadratic regression method to being obtained by step 8) based on forgetting factor _MaxCarry out filtering operation and handle, the result after the processing shows by display unit: since the restriction of observation instrument, the tire that step 8) obtains-road surface maximum grip coefficient

Observed result inevitably has noise and burr.The inventive method adopts the current maximum grip coefficient μ of quadratic regression method to being obtained by step 7) _MaxCarry out filtering operation and handle, to improve the smoothness and the accuracy of observed result.The concrete steps of quadratic regression method are as follows:

1. calculating observation error e _k, its calculation expression is as follows:

$e_k={\widehat{\mathrm{\&mu;}}}_{\max ,k}-{\stackrel{\&OverBar;}{\mathrm{\&mu;}}}_{\max ,k-1}---\left(19\right)$

In the formula, μ _{Max, k-1}Be k-1 filtered observed result constantly,

It is k sampled result constantly.

2. calculated gains matrix U _k, its calculation expression is as follows:

$U_k=\frac{P_{k-1}\left[\begin{array}{cc}0& 1\end{array}\right]}{{\mathrm{\&lambda;}}_F+\left[\begin{array}{cc}0& 1\end{array}\right]P_{k-1}\left[\begin{array}{c}0\\ 1\end{array}\right]}---\left(20\right)$

In the formula, P _K-1Be k-1 variance matrix constantly, λ _FBe forgetting factor, take all factors into consideration the flatness of observed result and the speed of convergence of observation here, choose λ _F=0.98.

3. calculate variance matrix, its calculation expression is as follows:

$P_k=\frac{1}{{\mathrm{\&lambda;}}_F}[P_{k-1}-\frac{P_{k-1}\left[\begin{array}{cc}0& 1\end{array}\right]{\left[\begin{array}{cc}0& 1\end{array}\right]}^T{P}_{k-1}}{{\mathrm{\&lambda;}}_F+\left[\begin{array}{cc}0& 1\end{array}\right]P_{k-1}{\left[\begin{array}{cc}0& 1\end{array}\right]}^T}]---\left(21\right)$

4. observed result is after upgrading k filtering constantly:

μ _max，k＝μ _max，k-1+U _ke _k (22)

Realize the quadratic regression algorithm of band forgetting factor by above step, thereby realize observation maximum coefficient of road adhesion.

Claims (3)

1, a kind of tire-road surface maximum grip coefficient method of testing, this method is used a kind of proving installation, and this device comprises: one is used to gather the information acquisition unit of automobile information; The one default control module handling described information acquisition unit input information and export tire-road surface maximum grip coefficient of being used to that is equipped with the nominal curve; And display device that shows described control module output; Described method of testing comprises the steps:

1) filtering operation is handled rotating speed, steering wheel angle input, automobile barycenter longitudinal acceleration and the transverse acceleration of the tire that records, to obtain automobile speed;

2) according to speed information that obtains in the step 1) and the wheel speed information that records, to obtain automotive wheel slip rate λ;

3) braking clamp body that records of calculation process and wheel contact area, caliper acting force equivalent point are to distance and the driving torque on the wheel or the braking moment of wheel center, to obtain vertical driving force of wheel or the vertical damping force of wheel;

4) between the barycenter longitudinal acceleration that records of calculation process, barycenter transverse acceleration, complete vehicle quality, automobile front axle distance, vehicle front to the distance of barycenter, automobile hind axle to barycenter between wheelspan, automobile back wheel wheelspan and automobile barycenter to the distance on road surface, to obtain the wheel vertical load;

5) according to step 3) and 4) in the vertical driving force of wheel or vertical damping force of wheel and the wheel vertical load that obtain, to obtain wheel tyre-coefficient of road adhesion μ;

6) according to step 2) and 5) in the current wheel slip λ that obtains and as front tyre-coefficient of road adhesion μ, to obtain current doughnut slippage slope;

7) on described nominal curve, utilize mapping relations to obtain the (λ of current doughnut slippage slope K in the corresponding step 6) ₀, μ ₀);

8) will (λ, μ) corresponding as front tyre-road surface maximum grip coefficient μ _MaxWith (λ ₀, μ ₀) corresponding tire-road surface maximum grip coefficient μ _Max0Compare, to obtain current maximum coefficient of road adhesion μ _Max

9) μ to obtaining by step 8) _MaxCarry out Filtering Processing and on described display device, show.

2, a kind of tire as claimed in claim 1-road surface maximum grip coefficient method of testing is characterized in that: described control module utilizes the theoretical off-line of normalization tire to obtain described nominal curve, tire on this nominal curve-road surface maximum grip coefficient μ _Max0=1.

3, a kind of tire as claimed in claim 1 or 2-road surface maximum grip coefficient method of testing is characterized in that: the current maximum coefficient of road adhesion μ that described control module obtains described step 8) _MaxCarrying out the quadratic regression filtering operation handles.