CN103234900A - Method for identifying sliding friction coefficient between tire and ground - Google Patents

Abstract

The invention relates to a method for identifying a sliding friction coefficient between a tire and ground. The method comprises the following steps of: respectively measuring a steering wheel hand torque by means of a dynamometric steering wheel under condition that a turntable is available or unavailable on two front wheels of a whole vehicle; indirectly measuring a friction torque at the turntable when a front axle of the whole vehicle has a load by means of the dynamometric steering wheel, substituting the friction torque into a torque equilibrium equation of a whole steering system, thus obtaining an in-situ steering drag torque between the tire and the ground; substituting the in-situ steering drag torque between the tire and the ground into an empirical calculation formula of the in-situ steering drag torque between the tire and the ground, thus obtaining the sliding friction coefficient between the tire and the ground in a process of an automobile steering in situ. During measurement, a special test bed rack is not required, the whole parts are not required to be detached, only the steering wheel torque and corner data are required to be respectively measured under the condition that the turntable is available or unavailable, and the method is simple and practical and has high practical significance for the part selection of the automobile power-assisted steering system and the design of a power-assisted characteristic curve.

Description

Coefficient of sliding friction discrimination method between a kind of tire and ground

Technical field

The present invention relates to the systematic parameter identification field in the Vehicle Engineering, the tire during particularly about a kind of automobile pivot stud and the coefficient of sliding friction discrimination method between ground.

Background technology

The size of the pivot stud moment of resistance between tire and ground is significant to the design of the selection of the critical component of automobile assisted power steering system and assist characteristic curve, and the identification of the coefficient of sliding friction between tire and ground is to adopt formula to calculate the key of the pivot stud moment of resistance between tire and ground during pivot stud.Therefore, obtain the coefficient of sliding friction between tire and ground exactly, play crucial effects for the selection of the critical component of automobile assisted power steering system and the design of assist characteristic curve.When adopting the pivot stud moment of resistance between formula calculating tire and ground at present, the coefficient of sliding friction that adopts mostly is the data in the 60 to 70's, and through technical development decades, the structure and material of tire has had great changes, bigger variation has also taken place in the numerical value of the coefficient of sliding friction between between tire and ground, and the assist characteristic curve that designs must reach the power-assisted effect of expection.Though the coefficient of sliding friction discrimination method between tire and ground also has additive methods such as portable pendulum tester method, braking distance method, brake instrument method and trailer method, they all have certain limitation.Wherein, portable pendulum tester method measuring point has certain limitation, and with vehicle running state certain discrepancy is arranged; And braking distance method and brake instrument method all need the brake hard vehicle, and both data dangerous and measurement calculating were not accurate enough, only just used under the situation of no special measurement instrument mostly; Though the trailer method can be measured tire-road surface coefficient of sliding friction preferably, but tire-road surface coefficient of sliding friction is subject to the influence of vertical load, the measured coefficient of sliding friction of trailer method is the friction factor under the trailer load, and there is certain deviation in the coefficient of sliding friction under its result and the carload.

Summary of the invention

At the problems referred to above, purpose of the present invention just provides the coefficient of sliding friction discrimination method between a kind of tire and ground, this method can be under the situation of not dismantling the car load parts, and tire and the coefficient of sliding friction between ground during to the automobile pivot stud carry out identification comparatively accurately.

For achieving the above object, the present invention takes following technical scheme: the coefficient of sliding friction discrimination method between a kind of tire and ground, and it may further comprise the steps: 1) at the original steering wheel of car load the dynamometry bearing circle is installed; 2) measure the steering wheel hand-power square that has under car load two front-wheels under rotating disk and two kinds of situations of no rotating disk respectively by the dynamometry bearing circle, calculate both difference T _H1-T _H2, T _H1And T _H2It is respectively the steering wheel hand-power square when rotating disk and no rotating disk are arranged; 3) load of unalterable rules shape on steering wheel, just the dynamometry bearing circle is installed on the steering wheel of bearing load again, guarantees that simultaneously the center of dynamometry bearing circle overlaps with the vertical axes that load is crossed geometric center of gravity; The two moment of friction M of front-wheel lower rotary table place when 4) measuring the car load propons and bear above-mentioned load by the dynamometry bearing circle _ZP5) the steering wheel hand-power square difference T that step 3) is obtained _H1-T _H2The moment of friction M of rotating disk place with the step 5) acquisition _ZpThe substitution following formula calculates the pivot stud moment of resistance M between tire and ground _R:

M _R＝(T _h1-T _h2)×i×η+M _ZP

In the following formula, i is the angular gear ratio of known steering, and η is the forward efficiency of known rack and pinion steering gear; 6) known steps 5) the pivot stud moment of resistance M that obtains _R, according to the experience computing formula of the pivot stud moment of resistance between tire and ground, the tire when calculating the automobile pivot stud and the coefficient of sliding friction f between ground.

Above-mentioned steps 6) in, the pivot stud moment of resistance experience computing formula between tire and ground is:

$M_R=\frac{f}{3}\sqrt{\frac{G^3}{p}}$

In the following formula, G is the gravity of known car load propons institute negative load, and p is known single pressure of tire.

The present invention is owing to take above technical scheme, it has the following advantages: 1, the present invention estimates the coefficient of sliding friction between tire and ground by detecting the vehicle pivot stud moment of resistance, during measurement, test-bed that need not be special, also need not to dismantle the car load parts, only need to measure respectively steering-wheel torque and the corner data that have under rotating disk and two kinds of situations of no rotating disk.Compare with the coefficient of sliding friction discrimination method between ground with existing tire, this method does not need to start up the car, the original place carry out steering operation can the identification tire and ground between the coefficient of sliding friction, simple and practical.2, the present invention need not to dismantle the car load parts, and the tire that institute's identification obtains and the coefficient of sliding friction between ground are subjected to the influence of vertical load less, and the measurement result accuracy is higher.The present invention can be widely used in the automobile assisted power steering system test, and the parts selection of automobile assisted power steering system and the design of assist characteristic curve are had stronger practical application meaning.

Description of drawings

Fig. 1 is the steering wheel hand-power square-outer corner measurement synoptic diagram during no rotating disk under car load two front-wheels of the present invention;

Fig. 2 is the steering wheel hand-power square-outer corner measurement synoptic diagram when under car load two front-wheels of the present invention rotating disk being arranged;

Fig. 3 has steering wheel hand-power square difference data processing synoptic diagram under rotating disk and two kinds of situations of no rotating disk for the present invention;

Rotating disk place moment of friction instrumentation plan when Fig. 4 bears regular shape load for car load propons of the present invention.

Embodiment

Below in conjunction with drawings and Examples the present invention is described in detail.

Principle of work of the present invention is as follows:

Generally speaking, the steering of automobile mainly is subjected to the effect of four power (moment): steering wheel hand-power square (being driver's hand-power square) T _hPivot stud moment of resistance M between tire and ground _R, M _R=M _RL+ M _RR, M _RLAnd M _RRBe respectively the pivot stud moment of resistance between left and right tire and ground; Gravity aligning torque M _Fz, M _Fz=M _FzL+ M _FzR, M _FzLAnd M _FzRBe respectively the gravity aligning torque of left and right tire; The friction force of whole steering (moment).

Wherein, be object of reference with the steering gear, the friction force (moment) of whole steering can be divided into three parts again: the equivalent friction moment T at steering gear input end steering column place _Fc, the friction force F of steering gear place _fMoment of friction T with steering gear output terminal stub place _Fp, T _Fp=T _FpL+ T _FpR, T _FpLAnd T _FpRBe respectively the moment of friction on left and right both sides, steering gear output terminal stub place.

The moment of steering gear input end is:

T _in=T _h－T _fc （1）

The moment of steering gear output terminal is:

T _out=M _Fz+M _R+T _fp （2）

The rotating speed of known gears tooth bar steering gear input end pinion wheel is ω _In, the angular gear ratio of steering is i, then tire is ω around the rotating speed of stub _Out=ω _In/ i.The power input of rack and pinion steering gear input end is:

P _in＝T _in×ω _in＝(T _h-T _fc)×ω _in （3）

The output power of rack and pinion steering gear output terminal is:

$P_{\mathrm{out}}=T_{\mathrm{out}}\×{\mathrm{\ω}}_{\mathrm{out}}=\frac{(M_{\mathrm{Fz}}+M_R+T_{\mathrm{fp}})\×{\mathrm{\ω}}_{\mathrm{in}}}{i}---\left(4\right)$

The forward efficiency of known gears tooth bar steering gear is η, can be got by law of conservation of energy:

$\mathrm{\η}=\frac{P_{\mathrm{out}}}{P_{\mathrm{in}}}=\frac{(M_{\mathrm{Fz}}+M_R+T_{\mathrm{fp}})}{(T_h-T_{\mathrm{fc}})\×i}---\left(5\right)$

Arrangement formula (5) can get:

$T_h=\frac{M_{\mathrm{Fz}}+M_R+T_{\mathrm{fp}}}{\mathrm{i\η}}+T_{\mathrm{fc}}---\left(6\right)$

Steering wheel hand-power square difference when by formula (6) as can be known, rotating disk and no rotating disk being arranged under car load two front-wheels is:

$T_{h1}-T_{h2}=\frac{M_R-M_{\mathrm{ZP}}}{\mathrm{i\η}}---\left(7\right)$

In the following formula, M _ZPBe rotating disk place moment of friction, M _ZP=M _ZPL+ M _ZPR, M _ZPLAnd M _ZPRBe respectively left and right tire rotating disk place moment of friction, its size can be demarcated it by the load of dynamometry bearing circle and regular shape in experiment, the implementation method that detailed process sees below.

The size of the pivot stud moment of resistance between tire and ground is:

M _R＝(T _h1-T _h2)× _i×η+M _ZP （8）

The experience computing formula of the pivot stud moment of resistance between tire and ground is:

$M_R=\frac{f}{3}\sqrt{\frac{G^3}{p}}---\left(9\right)$

In the following formula, the tire when f is automobile pivot stud to be found the solution and the coefficient of sliding friction between ground; G is the gravity of car load propons institute negative load, and p is single pressure of tire, and is all given.

With the tire that obtains in the formula (8) and the pivot stud moment of resistance value M between ground _RSubstitution formula (9), the tire in the time of can obtaining the automobile pivot stud and the coefficient of sliding friction f between ground.

When the present invention specifically implements, can adopt following scheme:

1) as shown in Figure 1 and Figure 2, at the original steering wheel of car load the dynamometry bearing circle is installed.

2) as shown in Figure 1, do not have rotating disk under two front-wheels of car load, steering wheel (handling maneuver speed can less than 0.2r/s) is beaten in the original place slowly, gathers torque and the corner data at steering wheel place simultaneously with the dynamometry bearing circle.

3) as shown in Figure 2, two front-wheel underlay rotating disks of car load, steering wheel is beaten in the original place slowly, gathers torque and the corner data at steering wheel place simultaneously with the dynamometry bearing circle.

4) as shown in Figure 3, under having gathered front-wheel, have after the steering-wheel torque and corner data under rotating disk and two kinds of situations of no rotating disk, can carry out match to these data, then according to the data after the match, calculate the difference T that steering wheel hand-power square under rotating disk and two kinds of situations of no rotating disk is arranged _H1-T _H2

5) as shown in Figure 4, the load of unalterable rules shape on steering wheel is installed on the dynamometry bearing circle on this steering wheel again, guarantees that simultaneously the center of dynamometry bearing circle overlaps with the vertical axes that load is crossed geometric center of gravity.Rotate the dynamometry bearing circle, gather dtc signal, the moment of friction M of rotating disk place when acquisition car load propons is born load _ZP

6) the steering wheel hand-power square difference T that step 4) is obtained _H1-T _H2The moment of friction M of rotating disk place with the step 5) acquisition _ZPSubstitution formula (8) can obtain the pivot stud moment of resistance M between tire and ground _R

7) tire that step 6) is obtained and the pivot stud moment of resistance M between ground _RBe updated to the pivot stud moment of resistance experience computing formula (9) between tire and ground, the tire in the time of can obtaining the automobile pivot stud and the coefficient of sliding friction f between ground.

The various embodiments described above only are used for explanation the present invention, and wherein the structure of each parts, connected mode etc. all can change to some extent, and every equivalents and improvement of carrying out on the basis of technical solution of the present invention all should do not got rid of outside protection scope of the present invention.

Claims (2)

1. the coefficient of sliding friction discrimination method between a tire and ground, it may further comprise the steps:

1) at the original steering wheel of car load the dynamometry bearing circle is installed;

2) measure the steering wheel hand-power square that has under car load two front-wheels under rotating disk and two kinds of situations of no rotating disk respectively by the dynamometry bearing circle, calculate both difference T _H1-T _H2, T _H1And T _H2It is respectively the steering wheel hand-power square when rotating disk and no rotating disk are arranged;

3) load of unalterable rules shape on steering wheel, just the dynamometry bearing circle is installed on the steering wheel of bearing load again, guarantees that simultaneously the center of dynamometry bearing circle overlaps with the vertical axes that load is crossed geometric center of gravity;

The two moment of friction M of front-wheel lower rotary table place when 4) measuring the car load propons and bear above-mentioned load by the dynamometry bearing circle _ZP

5) the steering wheel hand-power square difference T that step 3) is obtained _H1-T _H2The moment of friction M of rotating disk place with the step 5) acquisition _ZpThe substitution following formula calculates the pivot stud moment of resistance M between tire and ground _R:

M _R＝(T _h1-T _h2)×i×η+M _ZP

In the following formula, i is the angular gear ratio of known steering, and η is the forward efficiency of known rack and pinion steering gear;

6) known steps 5) the pivot stud moment of resistance M that obtains _R, according to the experience computing formula of the pivot stud moment of resistance between tire and ground, the tire when calculating the automobile pivot stud and the coefficient of sliding friction f between ground.

2. the coefficient of sliding friction discrimination method between a kind of tire as claimed in claim 1 and ground is characterized in that, in the described step 6), the pivot stud moment of resistance experience computing formula between tire and ground is:

$M_R=\frac{f}{3}\sqrt{\frac{G^3}{p}}$

In the following formula, G is the gravity of known car load propons institute negative load, and p is known single pressure of tire.

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