CN104442450A - Method and system for judging operating condition of vehicle under traction state - Google Patents

Abstract

The invention relates to a method and a system for judging operating condition of a vehicle under a traction state. The method includes: measuring output torque T of a vehicle motor and wheel speed omega; estimating adhesion moment Td; computing an output torque change value T and an adhesion moment change value Td; judging the operating condition of the vehicle according to the output torque change value T and the adhesion moment change value Td. The operating condition of the vehicle under the traction state can be judged by only measuring the output torque outputted by the vehicle motor to wheels and wheel speed information, the judgment process is simple and reliable, and output parameters of the method can be applied to the vehicle slip control process. Besides, the method and the system are few in needed sensors, low in implementation cost and high in reliability.

Description

A kind of method and system of the vehicle operating status judged under traction state

Technical field

The present invention relates to vehicle operating status detection technique field, be specifically related to a kind of method and system of the vehicle operating status judged under traction state.

Background technology

In vehicle running under power or brake control process, when power system passes to the propulsive effort of tire or braking force exceedes adhesive force critical value (vehicle is to the maximum static friction force on ground) on tire and road surface, the tire of vehicle can send out idle running phenomenon, and this phenomenon is exactly the astable mode of operation of vehicle (vehicle slip state).Once skidding appears in vehicle, the maximum static friction force critical value meeting step-down on vehicle and ground, the ground kinetic frictional resistances that automobile is subject to will decline, and the antagonistic force of road surface to vehicle sharply reduces, and causes the critical Driving Force of tyre slip to reduce.No matter be in vehicle traction operational process or in brake control process, when automobile is in the astable mode of operation of skidding, the safety of meeting havoc vehicle drive and controllability.Ensure that wheel of vehicle is in steady-working state and has very important significance to vehicle in Different Ground situation.

Traditional vehicle stability judges mainly based on the identification of current slip rate and the judgement of optimal slip rate, many researchers are had to carry out large quantifier elimination with regard to slip rate λ at present, achievement in research roughly can be divided into two classes: a class directly obtains slip rate λ by the relation of the rotating speed (wheel linear speed) of vehicle chassis speed (vehicle actual travel speed) and wheel, changes by slip rate and friction coefficient the stability judging vehicle.From slip rate formula, the difference of the slip rate λ of vehicle and vehicle wheel rotational speed and vehicle chassis speed has nonlinear relationship.Therefore the slip rate parameter directly obtaining vehicle accurately must obtain rotating speed and the chassis speed of wheel.For vehicle chassis speed, although there are many method of measurement at present, the restriction of the susceptibility of sensors towards ambient, high cost and survey precision constrains practical application, and automobile vibration also has considerable influence to result of a measurement simultaneously.Equations of The Second Kind is called state observer method, the relation of vehicle wheel rotational speed and slip rate λ is obtained by wheel movement equation, estimate current slip rate, judge present tire, optimal slip rate under pavement conditions, and then judgement vehicle operating status, this method avoids this parameter of the speed of a motor vehicle, but the accuracy rate of the method when vehicle lower-speed state is poor, and practicality is not high.And optimal slip rate is different under different tires, road surface contact conditions, is difficult to real-time judge, limitation is in actual applications very large, and practical application effect is bad.

Summary of the invention

For this reason, technical matters to be solved by this invention is, vehicle operating status method of inspection common at present exist vehicle actual travel speed cannot accurately measure or lower-speed state time judge that the bad and optimal slip rate of effect is difficult to the technical matters of real-time judge.Thus propose a kind of need the Driving Torque of measuring vehicle motor and vehicle wheel rotational speed just can accurately identify the vehicle under traction state is in the determination methods of steady-working state or astable mode of operation.

For solving the problems of the technologies described above, the invention provides following technical scheme:

Judge a method for the vehicle operating status under traction state, comprising:

The Driving Torque T of measuring vehicle motor and vehicle wheel rotational speed ω;

Estimation adheres to moment T _d;

Calculate Driving Torque changing value △ T and adhere to moment changing value △ T _d;

According to Driving Torque changing value △ T and adhesion moment changing value △ T _djudge the vehicle operating status under traction state.

As optimization, also comprised before the Driving Torque T and vehicle wheel rotational speed ω of measuring vehicle motor:

The inertia constant J of initialization vehicle, inertia constant J is relevant to the parameter of car.

As optimization, adhere to moment T in estimation _dalso comprise before:

Filtering process is carried out to vehicle wheel rotational speed ω.

As optimization, Driving Torque T is obtained by the received current measuring motor, and under constant current state, Driving Torque T equals torque constant and motor input current is long-pending.

As optimization, adhere to moment T _daccording to formula estimation gained, wherein it is the derivative to vehicle wheel rotational speed ω.

As optimization, according to Driving Torque changing value △ T and adhesion moment changing value △ T _djudge the vehicle operating status under traction state, comprising:

Moment changing value △ T is adhered to as Driving Torque changing value △ T>0 _dduring >0, or work as Driving Torque changing value △ T<0 and adhere to moment changing value △ T _dduring <0, or work as Driving Torque changing value △ T=0 and adhere to moment changing value △ T _dduring >=0, judge that the vehicle under traction state is in steady-working state;

Moment changing value △ T is adhered to as Driving Torque changing value △ T>0 _dduring <0, or work as Driving Torque changing value △ T<0 and adhere to moment changing value △ T _dduring >0, or work as Driving Torque changing value △ T=0 and adhere to moment changing value △ T _dduring <0, judge that the vehicle of traction state is in astable mode of operation.

As optimization, according to Driving Torque changing value △ T and adhesion moment changing value △ T _djudge the vehicle operating status under traction state, comprising:

When △ T ≠ 0,

When and time, judge that vehicle is in the critical transformation condition being about to be converted to astable mode of operation from steady-working state;

When and time, judge that vehicle is in steady-working state;

When and time, judge that vehicle is in astable mode of operation;

When and time, judge that vehicle is in the Determination of Critical Transition Point being about to enter steady-working state from astable mode of operation;

When △ T=0,

As △ T _dduring <0, judge that vehicle is in unstable working state;

As △ T _dduring >=0, judge that vehicle is in steady-working state;

Wherein, Δ T (k) is the Driving Torque changing value of current calculating gained, and Δ T (k-1) is the Driving Torque changing value of last computation gained, Δ T _dk () is the adhesion moment changing value of current calculating gained, Δ T _d(k-1) be the adhesion moment changing value of last computation gained.

As optimization, according to Driving Torque changing value △ T and adhesion moment changing value △ T _dalso comprise after judging the step of the vehicle operating status under traction state: determine that whether implementing amplitude limit to Driving Torque T controls in real time according to judged vehicle operating status.

As optimization, determine that whether implementing amplitude limit to Driving Torque T controls to comprise in real time according to judged vehicle operating status:

When judging that vehicle is in astable mode of operation, then amplitude limit is implemented to Driving Torque T and control;

When judgement vehicle is in steady-working state, then amplitude limit is not implemented to Driving Torque T and control.

Judge a system for the vehicle operating status under traction state, comprising:

Measurement module, for Driving Torque T and the vehicle wheel rotational speed ω of measuring vehicle motor;

Estimation block, adheres to moment T for estimating _d;

Computing module, for calculating Driving Torque changing value △ T and adhering to moment changing value △ T _d;

Determination module, for according to Driving Torque changing value △ T with adhere to moment changing value △ T _djudge the vehicle operating status under traction state.

As optimization, judge that the system of vehicle operating status also comprises:

Initialization module, for obtaining the inertia constant J of vehicle; And/or

Filtration module, for carrying out filtering process to the vehicle wheel rotational speed ω measuring gained; And/or

Clipping module, implements amplitude limit to Driving Torque T when being in astable mode of operation for the vehicle under traction state and controls.

Technique scheme of the present invention has the following advantages compared to existing technology:

The method and system of a kind of vehicle operating status judged under traction state provided by the invention, physical mechanics based on vehicle slip process is theoretical, only need measuring vehicle motor transfer to the Driving Torque of wheel and vehicle wheel rotational speed information can judge traction state under vehicle operating status, do not need to know vehicle chassis speed and slip rate value, decision process is simple and reliable, and the output parameter of the method may be used for vehicle slip control process, this method is applicable to the practical application of wagon control very much.In addition, required sensor is few, implementation cost is low, reliability is also high.The present invention is also applicable to slip state detection when adopting motor-driven 4 wheel driven automobile and adopt the equipment work such as motor-driven various robot, machine exoskeleton.

Accompanying drawing explanation

Fig. 1 is the diagram of circuit of the method according to the vehicle operating status under the judgement traction state of the embodiment of the present invention;

Fig. 2 is the graph of a relation of vehicle slip rate λ and coefficientoffrictionμ when different road surface;

Distribution of force schematic diagram when Fig. 3 is wheel work;

Fig. 4 is the method flow diagram of the vehicle operating status judged according to another embodiment of the present invention under traction state;

Fig. 5 is the system schematic according to the vehicle operating status under the judgement traction state of the embodiment of the present invention.

Detailed description of the invention

In order to make those skilled in the art person understand the present invention program better, below in conjunction with drawings and Examples, technical scheme provided by the present invention is described in further detail.

In the following embodiments, d/dt represents the derivative of variable; △ represents small-signal, refers to the change detecting the moment.

Embodiment 1

Fig. 1 shows the diagram of circuit of the method according to the vehicle operating status under the judgement traction state of the embodiment of the present invention, and the method comprises the steps:

Step S1: the Driving Torque T of measuring vehicle motor and vehicle wheel rotational speed ω.Here, Driving Torque T can be obtained by the received current measuring motor, and under constant current state, the Driving Torque T of motor equals torque constant and motor input current is long-pending, and vehicle wheel rotational speed ω obtains by the rotating speed measuring motor.

Step S2: estimation adheres to moment T _d.Here, moment T is adhered to _daccording to formula estimation gained, wherein J is the inertia variable of vehicle, it is the derivative to vehicle wheel rotational speed ω.The inertia variable J of vehicle is relevant to the parameter of car, its value does not change with environment and time, numerical value is determined by measuring acquisition, parameter J is known quantity under normal circumstances, but for using the situation of vehicle first, the step of the inertia variable J performing initialization vehicle was also needed, to determine the value of parameter J before step S2.To the differentiate process formula of vehicle wheel rotational speed ω be wherein Δ t represents the time difference of twice measurement in front and back, the difference (ω (k)-ω (k-1)) of vehicle wheel rotational speed ω when Δ ω represents that front and back are measured for twice.Namely can draw thus and adhere to moment T _d.

Preferably, can also comprise before step S2: filtering process is carried out to vehicle wheel rotational speed ω, noise jamming when measuring with filtering, improve the accuracy rate of follow-up derived function result.Further preferably, low-pass filter can be adopted to carry out filtering process to vehicle wheel rotational speed ω.

Step S3: calculate Driving Torque changing value △ T and adhere to moment changing value △ T _d.Here, Driving Torque changing value Δ T and adhesion moment changing value Δ T _drepresent that motor is delivered to Driving Torque T and the wheel adhesion moment T of wheel respectively _dthe difference of double survey calculation value, its computing formula is: Δ T=T (k)-T (k-1) and Δ T _d=T _d(k)-T _d(k-1), wherein, T (k) represents the Driving Torque value of current survey calculation, the Driving Torque value of motor when T (k-1) represents survey calculation last time, T _dk () represents the adhesion moment values of current estimation gained, T _d(k-1) the adhesion moment values estimating gained last time is represented.Thus, namely can calculate Driving Torque changing value △ T and adhere to moment changing value △ T _d.

Step S4: according to Driving Torque changing value △ T and adhesion moment changing value △ T _djudge the vehicle operating status under traction state.Specifically can there is the following two kinds criterion.

The first criterion is: adhere to moment changing value △ T as Driving Torque changing value △ T>0 _dduring >0, or work as Driving Torque changing value △ T<0 and adhere to moment changing value △ T _dduring <0, or work as Driving Torque changing value △ T=0 and adhere to moment changing value △ T _dduring >=0, judge that the vehicle under traction state is in steady-working state; Moment changing value △ T is adhered to as Driving Torque changing value △ T>0 _dduring <0, or work as Driving Torque changing value △ T<0 and adhere to moment changing value △ T _dduring >0, or work as Driving Torque changing value △ T=0 and adhere to moment changing value △ T _dduring <0, judge that the vehicle under traction state is in astable mode of operation.

The second criterion is: when △ T ≠ 0, when and time, judge that vehicle is in the critical transformation condition being about to be converted to astable mode of operation from steady-working state; When and time, judge that vehicle is in steady-working state; When and time, judge that vehicle is in astable mode of operation; When and time, judge that vehicle is in the Determination of Critical Transition Point being about to enter steady-working state from astable mode of operation;

When △ T=0, as △ T _dduring <0, judge that vehicle is in unstable working state; As △ T _dduring >=0, judge that vehicle is in steady-working state;

Wherein, Δ T (k) is the Driving Torque changing value of current calculating gained, and Δ T (k-1) is the Driving Torque changing value of last computation gained, Δ T _dk () is the adhesion moment changing value of current calculating gained, Δ T _d(k-1) be the adhesion moment changing value of last computation gained.

In brief, for the situation of △ T ≠ 0, when Driving Torque is identical with the variation tendency adhering to moment, when namely all becoming greatly or all diminish, vehicle is in steady-working state, otherwise is then in astable mode of operation.And for the situation of Δ T=0, vehicle is this moment in more special state of kinematic motion, and the Driving Torque of vehicle does not change, and this epidemic situation comparison is rare.If Δ T this moment _d>0, then illustrate that the adhesion moment on wheel and ground is increasing, and illustrates that vehicle is in steady-working state, or Δ T _d=0, then illustrate that the adhesion moment on wheel and ground is stablized constant, vehicle is in steady-working state; Otherwise, illustrate that vehicle is in astable mode of operation.

For Δ T ≠ 0 and Δ T _dthe situation of=0, the torque T that the motor due to vehicle is transferred to wheel is that wheel and ground adhere to moment variations, the T when Δ T ≠ 0 _dmust change, therefore Δ T during Δ T ≠ 0 _dthe state of=0 can not occur, and therefore this state is without the need to considering.

The following detailed description of the square ratio juris according to the vehicle operating status under the judgement traction state of the embodiment of the present invention.

The propulsive effort that vehicle advances is from the friction force on wheel and ground, and power system is converted into propulsive effort and wheel that vehicle advances to the propulsive effort of wheel and ground friction generates heat.Therefore vehicle under traction state the speed of a motor vehicle lower than the rotating speed (wheel line speed) of wheel; Under braking mode, the speed of a motor vehicle is greater than the rotating speed (wheel line speed) of wheel.The expression formula of vehicle slip rate λ is:

λ＝{(ωr-ν)/max(ωr,ν,ε)}

Wherein: ω represents angular speed of wheel, r refers to radius of wheel, and ν represents the speed of a motor vehicle, ε be prevent formula denominator be zero little constant.

The method of the judgement vehicle operating status that the present embodiment provides is only applicable to the vehicle under traction state, therefore

λ=(ω r-ν)/ω r}, wherein ω r ≠ 0 (1)

The slip rate λ of automobile reflects the interaction relationship of vehicle tyre and kiss the earth, by the variation relation of slip rate λ and friction factor μ stability during vehicle operation can be judged.Research shows: on different ground (do ground, have face, water route and ice face), the slip rate λ of automobile and coefficientoffrictionμ exist regular nonlinear relationship.As shown in Figure 2, for the relation schematic diagram of automobile λ-μ when different road surface, can find out under three kinds of road environments, the friction force of vehicle closes with the change of slip rate exists similar variation tendency: in stable region, the slip rate of vehicle increases the increase along with friction force, and friction force provides adhesive force that vehicle is normally worked for vehicle; And when automobile is operated in critical conditions and unstable region, after the friction force of vehicle reaches maxim, friction force does not increase following vehicle slip rate, now skidding appears in the wheel of vehicle.

The correlativity of vehicle slip coefficient lambda and friction coefficient μ can be divided into 2 regions, and a region is stabilized zone, and another part is called unstable region (skidding region).

If slip rate λ and friction force factor mu meet formula this illustrates that vehicle operating is at steady-working state, and now the friction force of automobile is followed the change of slip rate and changes.

If slip rate λ and friction are μ meet formula then illustrate that automotive operation is in critical conditions, now the friction force of automobile reaches maxim, no longer follows the change of slip rate.

If slip rate λ and friction are μ meet formula then illustrate that automobile is operated in astable mode of operation (slipping state), now the friction force of wheel reduces on the contrary with slip rate increase.

The direct causal relationship of stability when wheel change in friction force and slip rate change work with automobile, can by right carry out strict analytical derivation to obtain, its derivation is as shown in formula (2):

$\frac{\mathrm{d\&mu;}}{\mathrm{d\&lambda;}}=\frac{1}{N}\frac{\mathrm{d\&mu;}*N}{\mathrm{d\&lambda;}}=\frac{1}{N}*\frac{{\mathrm{dF}}_d}{\mathrm{d\&lambda;}}---\left(2\right)$

Wherein: N represents the method phase pressure of automotive wheel to ground, is constant; F _drepresent the adhesive force (friction force) on wheel and ground.

As shown in Figure 3, distribution of force schematic diagram when being wheel of vehicle work.By analyzing known to the distribution of force of wheel model, the propulsive effort that during vehicle wheel rotation, the adhesive force on wheel and ground and wheel drive vehicle advance is a pair interaction force, when the output drive strength of vehicular electric machine is greater than the maximum frictional force on wheel and ground, wheel just there will be skidding.When there is slipping state, now the rotating speed of wheel can increase, and the resistance of wheel is made up of wheel and the adhesive force on ground and the force of inertia of vehicle wheel rotation.According to rotation of wheel motion-promotion force theory, moment distribution during wheel work meets formula (3):

$J\frac{\mathrm{d\&omega;}}{\mathrm{dt}}=T-r*F_d,$ Namely $J\frac{\mathrm{d\&omega;}}{\mathrm{dt}}=T-T_d---\left(3\right)$

Wherein: J is the inertia constant of tire; T represents the Driving Torque of motor; F _drepresent the adhesive force on wheel and ground; T _drepresent the moment that wheel and frictional ground force produce wheel, namely wheel adheres to moment, and due to the reciprocity of power, friction moment is also the drive torque driving wheel to advance; The Driving Torque of motor is deducted the moment that friction force produces, be exactly the slipping torque of wheel when difference is greater than 0, namely the friction force of wheel is less than the propulsive effort of wheel, and skidding appears in wheel, and excess energy is consumed by skidding heating.Utilize the force of inertia of wheel and angular speed of wheel rate of change product just can calculate tyre skidding moment.

Automobile longitudinal motion dynamic formula is:

MV＝(F _d-F _dr)t (4)

Wherein: M represents car mass; V represents the speed of a motor vehicle; F _drinertia resistance when being vehicle wheel rotation is constant.

The propulsive effort computing formula that wheel accelerates is:

F _d＝μ*N (5)

According to the relation curve of the μ-λ in Fig. 2, represent the rate of curve at curve operation point place with g, suppose that μ-λ curve presents linear relationship in a bit of distance, can be expressed as in the value of i place, operation point slope of a curve g:

i.e. Δ μ=g* Δ λ (6)

When operation point i, following equation can be obtained by slip rate:

$\mathrm{\&Delta;\&lambda;}=\frac{\mathrm{d\&lambda;}}{\mathrm{dV}}\mathrm{\&Delta;V}+\frac{\mathrm{d\&lambda;}}{\mathrm{d\&omega;}}\mathrm{\&Delta;\&omega;}=-\frac{1}{r{\mathrm{\&omega;}}_i}\mathrm{\&Delta;V}+\frac{V_i}{r{\mathrm{\&omega;}}_i^2}\mathrm{\&Delta;\&omega;}---\left(7\right)$

This is the small signal linearization formula in controlling.

Can be obtained by formula (3): $\mathrm{\&Delta;T}-\mathrm{r\&Delta;}{F}_d=J\frac{d\left(\mathrm{\&Delta;\&omega;}\right)}{\mathrm{dt}}---\left(8\right)$

Can be obtained by formula (4): $M\frac{d\left(\mathrm{\&Delta;V}\right)}{\mathrm{dt}}=\mathrm{\&Delta;}{F}_d---\left(9\right)$

Can be obtained by formula (5) and (6): Δ F _d=N* Δ μ=N*g* Δ λ (10)

From formula (7): $\mathrm{\&Delta;\&omega;}=(\mathrm{\&Delta;\&lambda;}+\frac{\mathrm{\&Delta;V}}{r{\mathrm{\&omega;}}_i})\frac{r{\mathrm{\&omega;}}_i^2}{V_i}---\left(11\right)$

From formula (1) and (10):

V _i＝(1-λ _i)rω _i； (12)

Δλ＝ΔF _d/g*N； (13)

So the expression formula of Δ ω can be converted to: $\mathrm{\&Delta;\&omega;}=\frac{{\mathrm{\&omega;}}_i}{(1-{\mathrm{\&lambda;}}_i)\mathrm{gN}}\mathrm{\&Delta;}{F}_d+\frac{1}{r(1-{\mathrm{\&lambda;}}_i)}\mathrm{\&Delta;V}---\left(14\right)$

From formula (8), formula (9) and formula (14):

$\mathrm{\&Delta;T}-\mathrm{r\&Delta;}{F}_d=\frac{J{\mathrm{\&omega;}}_i}{(1-{\mathrm{\&lambda;}}_i)\mathrm{gN}}\frac{d\left(\mathrm{\&Delta;}{F}_d\right)}{\mathrm{dt}}+\frac{J}{\mathrm{rM}(1-{\mathrm{\&lambda;}}_i)}\mathrm{\&Delta;}{F}_d---\left(15\right)$

Can obtain after Laplace transform is carried out to formula (15):

$\mathrm{\&Delta;T}\left(s\right)-\mathrm{r\&Delta;}{F}_d\left(s\right)=\frac{J{\mathrm{\&omega;}}_i}{(1-{\mathrm{\&lambda;}}_i)\mathrm{gN}}*s*\mathrm{\&Delta;}{F}_d\left(s\right)+\frac{J}{\mathrm{Mr}(1-{\mathrm{\&lambda;}}_i)}\mathrm{\&Delta;}{F}_d\left(s\right)---\left(16\right)$

Finally, we can obtain the linear open loop transfer function of the vehicle stabilization factor:

$\mathrm{\&phi;}\left(s\right)=\frac{\mathrm{\&Delta;}{T}_d\left(s\right)}{\mathrm{\&Delta;T}\left(s\right)}=\frac{r*\mathrm{\&Delta;}{F}_d\left(s\right)}{\mathrm{\&Delta;T}\left(s\right)}=K\left(\frac{1}{\mathrm{\&tau;s}+1}\right)---\left(17\right)$

K is a static gain parameter, and it shows when slip rate increases, and the drive torque of motor reduces ability, and the expression formula of K is:

$K=\mathrm{\&phi;}\left(s\right){|}_{s=0}=>K=\frac{{\mathrm{Mr}}^2(1-{\mathrm{\&lambda;}}_1)}{J+{\mathrm{Mr}}^2(1-{\mathrm{\&lambda;}}_1)}---\left(18\right)$

The value of time parameter τ is: $\mathrm{\&tau;}=\frac{\mathrm{JMr}{\mathrm{\&omega;}}_i}{\mathrm{gN}(J+{\mathrm{Mr}}^2(1-{\mathrm{\&lambda;}}_1))};(g\&NotEqual;0)---\left(19\right)$

Assuming that near certain operation point, motor there occurs the variable quantity △ T of a step to the torque that wheel applies, and its amplitude is ε, so just has:

△T＝ε·1(t) (20)

Wherein, 1 (t) represents a unit step signal.

According to formula (17) and formula (20), and inverse Laplace transformation principle can obtain:

$\begin{array}{c}\mathrm{\&Delta;}{T}_d=L^{-1}[\mathrm{\&Phi;}\left(s\right)*\frac{\mathrm{\&epsiv;}}{s}]=L^{-1}[\frac{\mathrm{K\&epsiv;}}{s}-\frac{\mathrm{K\&epsiv;}}{s+1/\mathrm{\&tau;}}]\\ =K(1-e^{-t/\mathrm{\&tau;}})*\mathrm{\&epsiv;}=K(1-e^{-t/\mathrm{\&tau;}})*\mathrm{\&Delta;T}=A_i*\mathrm{\&Delta;T}\end{array}---\left(21\right)$

Can be obtained by formula (21):

$A_i=\frac{\mathrm{\&Delta;}{T}_d}{\mathrm{\&Delta;T}}=K(1-e^{-t/\mathrm{\&tau;}});---\left(22\right)$

From formula (3), T _dthe computing formula of value is:

$T_d=(T-J\stackrel{\&CenterDot;}{\mathrm{\&omega;}})---\left(23\right)$

From formula (18) (19) (22) and formula (23):

When value when being less than 0, then 1-e ^{-t/ τ}<0, so certain free constant τ is less than 0; Now parameter g is also less than 0 certainly, and finally we can release:

$g=\frac{\mathrm{\&Delta;\&mu;}}{\mathrm{\&Delta;\&lambda;}}<0;$

It can thus be appreciated that the mode of operation of vehicle is astable mode of operation.

In like manner:

When value when being greater than 0, then 1-e ^{-t/ τ}<0, so certain free constant τ is greater than 0; Now parameter g is also greater than 0 certainly, and finally we can release:

$g=\frac{\mathrm{\&Delta;\&mu;}}{\mathrm{\&Delta;\&lambda;}}>0;$

It can thus be appreciated that the mode of operation of vehicle is steady-working state.

Therefore, can be drawn by above-mentioned derivation, pass through value can obtain vehicle operating status.

Analyze the situation as Δ T=0: now can not directly with above-mentioned computing of being divided by, therefore this extraordinary circumstances need to consider separately.During Δ T=0, expression motor exports a constant moment size, and namely variable quantity is zero.Now, in transient state situation, when being in stabilized zone, have Δ T _d>0, should have Δ T _d=0.In addition, when road surface changes suddenly, when becoming low attachment road surface from height attachment road surface, even if motor output torque is constant, i.e. Δ T=0, we also can observe adhesive ability and reduce, i.e. Δ T _d<0, so during unstable region, Δ T _d<0.Therefore comprehensive above-mentioned judgement, provides the criterion under this special case:

If Δ T=0 and Δ T _d<0, then vehicle is in unstable working state;

If Δ T=0 and Δ T _d>=0, then vehicle is in as steady-working state.

In reality detects, the motor of automobile is delivered to the Driving Torque of wheel and the detection of wheel adhesive force torque is all discrete, therefore Δ T _drepresent that motor is delivered to Driving Torque T and the wheel adhesion moment T of wheel with Δ T _dthe difference of double detection computations value.Its computing formula is: Δ T _d=T _d(k)-T _dand Δ T=T (k)-T (k-1) (k-1).Therefore in practical application, being described below of vehicle operation stability judging method:

(1). as Δ T _d>0 and Δ T>0 time, then suppose dT (s) >0, so dT _ds () >0, namely the adhesive force of wheel to ground increases with the increase of motor output torque, illustrates that vehicle is in steady-working state.

(2). as Δ T _d<0 and Δ T<0 time, then wheel reduces with motor output torque the adhesive force on ground and reduces, and illustrates that vehicle is in steady-working state.

(3). as Δ T _d<0 and Δ T>0 time, then wheel reduces on the contrary to the increase of the adhesive force on ground with vehicular electric machine Driving Torque, and illustrate that skidding has appearred in wheel, vehicle is in astable mode of operation.

(4). as Δ T _d>0 and Δ T<0 time, then namely wheel reduces with motor output torque the adhesive force on ground and increases, and illustrate that vehicle is in astable work area, vehicle operating status moves to stabilized zone.

(5). as Δ T=0, vehicle is this moment in more special state of kinematic motion, and the Driving Torque of vehicle does not change, and this epidemic situation comparison is rare.If Δ T this moment _d>=0, then illustrate that the adhesion moment on wheel and ground is increasing or balancing, and illustrates that vehicle is in steady-working state; Otherwise, illustrate that vehicle is in astable mode of operation.

Therefore, the vehicle operating status under traction state can be judged by the adhesion moment changing value of the Driving Torque changing value of vehicular electric machine and wheel, do not need to know vehicle chassis speed and slip rate value, decision process is simple and reliable, and the output parameter of the method may be used for vehicle slip control process, this method is applicable to the practical application of wagon control very much.In addition, required sensor is few, implementation cost is low, reliability is also high.

Embodiment 2

Fig. 4 shows the diagram of circuit of the method for the vehicle operating status judged according to another embodiment of the present invention under traction state, and the method comprises the steps:

Step S21: the inertia constant J of initialization vehicle.

Step S22: the Driving Torque T of measuring vehicle motor and vehicle wheel rotational speed ω.

Step S23: carry out filtering process to vehicle wheel rotational speed ω, preferably can adopt low-pass filter to carry out filtering process to vehicle wheel rotational speed ω.

Step S24: estimation adheres to moment T _d.According to formula estimate and adhere to moment T _d, wherein it is the derivative to vehicle wheel rotational speed ω.

Step S25: calculate Driving Torque changing value △ T and adhere to moment changing value △ T _d.

Step S26: according to Driving Torque changing value △ T and adhesion moment changing value △ T _djudge the vehicle operating status under traction state.

Step S27: according to judged vehicle operating status, whether real-time decision implements amplitude limit to Driving Torque T controls, specifically comprise: when vehicle is in astable mode of operation, then determine that implementing amplitude limit to the Driving Torque T of vehicular electric machine controls, and makes vehicle get back to steady-working state; When vehicle is in steady-working state, then determine that not implementing amplitude limit to the Driving Torque T of vehicular electric machine controls.Implement amplitude limit to Driving Torque T to control, the value by Driving Torque T is limited in a less value, to reduce vehicle wheel rotational speed ω, thus vehicle is slowly settled out no longer skid, and finally stablely under lower-speed state travels.

Repeated execution of steps S22 to S27, wherein in step s 27, when finding that the vehicle under traction state converts astable mode of operation to from steady-working state, then implements amplitude limit to Driving Torque and controls, when detecting next time, if when this vehicle is still in astable mode of operation, then continue to implement amplitude limit to Driving Torque to control, if when this vehicle is converted to steady-working state from astable mode of operation, then cancel and the amplitude limit of Driving Torque is controlled, so that chaufeur can adapter control, otherwise, this vehicle adheres to road surface always amplitude limit value before will maintaining carrys out the Driving Torque of limiting motor, even if after high adhesive force road surface is changed on road surface into, the amplitude limit of Driving Torque controls also cannot cancel, cause this vehicle that the adhesive ability on high adhesion force road surface cannot be utilized to realize the normal acceleration of vehicle.The method of a kind of vehicle operating status judged under traction state that the present embodiment provides, physical mechanics based on vehicle slip process is theoretical, only need measuring vehicle motor transfer to the Driving Torque of wheel and vehicle wheel rotational speed information can judge traction state under vehicle operating status, do not need to know vehicle chassis speed and slip rate value, decision process is simple and reliable, and the output parameter of the method may be used for vehicle slip control process, this method is applicable to the practical application of wagon control very much.In addition, required sensor is few, implementation cost is low, reliability is also high.The present invention is also applicable to slip state detection when adopting motor-driven 4 wheel driven automobile and adopt the equipment work such as motor-driven various robot, machine exoskeleton.

Embodiment 3

As shown in Figure 5, present invention also offers a kind of system of the vehicle operating status judged under traction state, comprising:

Measurement module 32, for Driving Torque T and the vehicle wheel rotational speed ω of measuring vehicle motor;

Estimation block 34, adheres to moment T for estimating _d;

Computing module 35, for calculating Driving Torque changing value △ T and adhering to moment changing value △ T _d;

Determination module 36, for according to Driving Torque changing value △ T with adhere to moment changing value △ T _djudge the vehicle operating status under traction state.

The system of a kind of vehicle operating status judged under traction state that the present embodiment provides, only need measuring vehicle motor transfer to the Driving Torque of wheel and vehicle wheel rotational speed information can judge traction state under vehicle operating status, do not need to know vehicle chassis speed and slip rate value, decision process is simple and reliable, and the output parameter of the method may be used for vehicle slip control process, be applicable to very much the practical application of wagon control.

Except above-mentioned module, this system can also comprise: initialization module 31, for obtaining the inertia constant J of vehicle.Initialization module 31 is only enabled when using vehicle first usually, to determine the value of parameter J, and for the follow-up use of vehicle, because inertia constant J is given value, then without the need to enabling initialization module 31 again.

Preferably, this system can also comprise: filtration module 33, for carrying out filtering process, noise jamming when measuring with filtering to the vehicle wheel rotational speed ω measuring gained, improves the accuracy rate of follow-up derived function result.Further preferably, low-pass filter can be adopted to carry out filtering process to vehicle wheel rotational speed ω.

Optimally, this system can also comprise: clipping module 37, controls for implementing amplitude limit when vehicle is in astable mode of operation to the Driving Torque of vehicular electric machine.Namely when vehicle is in astable mode of operation, Driving Torque T is limited in a less value, vehicle wheel rotational speed reduces, and to make vehicle break away from slipping state gradually, is in the steady-working state of low speed driving.

The system of a kind of vehicle operating status judged under traction state that the present embodiment provides, only need measuring vehicle motor transfer to the Driving Torque of wheel and vehicle wheel rotational speed information can judge traction state under vehicle operating status, do not need to know vehicle chassis speed and slip rate value, decision process is simple and reliable, and the output parameter of the method may be used for vehicle slip control process, this method is applicable to the practical application of wagon control very much.In addition, required sensor is few, implementation cost is low, reliability is also high.

Obviously, above-described embodiment is only for clearly example being described, and the restriction not to embodiment.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here exhaustive without the need to also giving all embodiments.And thus the apparent change of extending out or variation be still among the protection domain of the invention.

Claims (11)

1. judge a method for the vehicle operating status under traction state, it is characterized in that, comprising:

The Driving Torque T of measuring vehicle motor and vehicle wheel rotational speed ω;

Estimation adheres to moment T _d;

Calculate Driving Torque changing value △ T and adhere to moment changing value △ T _d;

According to described Driving Torque changing value △ T and described adhesion moment changing value △ T _djudge the vehicle operating status under traction state.

2. the method for claim 1, is characterized in that, also comprises before the Driving Torque T of described measuring vehicle motor and the step of vehicle wheel rotational speed ω:

The inertia constant J of initialization vehicle, described inertia constant J is relevant to the parameter of car.

3. method as claimed in claim 1 or 2, is characterized in that, adheres to moment T in described estimation _dstep before also comprise:

Filtering process is carried out to described vehicle wheel rotational speed ω.

4. the method according to any one of claim 1-3, is characterized in that, described Driving Torque T is obtained by the received current measuring motor, and under constant current state, described Driving Torque T equals torque constant and motor input current is long-pending.

5. the method according to any one of claim 1-4, is characterized in that, described adhesion moment T _daccording to formula estimation gained, wherein it is the derivative to described vehicle wheel rotational speed ω.

6. the method according to any one of claim 1-5, is characterized in that, described according to described Driving Torque changing value △ T and described adhesion moment changing value △ T _djudge the vehicle operating status under traction state, comprising:

As described Driving Torque changing value △ T>0 and described adhesion moment changing value △ T _dduring >0, or work as described Driving Torque changing value △ T<0 and described adhesion moment changing value △ T _dduring <0, or work as described Driving Torque changing value △ T=0 and described adhesion moment changing value △ T _dduring >=0, judge that the vehicle under traction state is in steady-working state;

As described Driving Torque changing value △ T>0 and described adhesion moment changing value △ T _dduring <0, or work as described Driving Torque changing value △ T<0 and described adhesion moment changing value △ T _dduring >0, or work as described Driving Torque changing value △ T=0 and described adhesion moment changing value △ T _dduring <0, judge that the vehicle under traction state is in astable mode of operation.

7. the method according to any one of claim 1-6, is characterized in that, described according to described Driving Torque changing value △ T and described adhesion moment changing value △ T _djudge the vehicle operating status under traction state, comprising:

When △ T ≠ 0,

When and time, judge that vehicle is in the critical transformation condition being about to be converted to astable mode of operation from steady-working state;

When and time, judge that vehicle is in steady-working state;

When and time, judge that vehicle is in astable mode of operation;

When and time, judge that vehicle is in the Determination of Critical Transition Point being about to enter steady-working state from astable mode of operation;

When △ T=0,

As △ T _dduring <0, judge that vehicle is in unstable working state;

As △ T _dduring >=0, judge that vehicle is in steady-working state;

Wherein, Δ T (k) is the Driving Torque changing value of current calculating gained, and Δ T (k-1) is the Driving Torque changing value of last computation gained, Δ T _dk () is the adhesion moment changing value of current calculating gained, Δ T _d(k-1) be the adhesion moment changing value of last computation gained.

8. the method according to any one of claim 1-7, is characterized in that, described according to described Driving Torque changing value △ T and described adhesion moment changing value △ T _dalso comprise after judging the step of the vehicle operating status under traction state: determine that whether implementing amplitude limit to described Driving Torque T controls in real time according to judged vehicle operating status.

9. method as claimed in claim 8, is characterized in that, describedly determines that whether implementing amplitude limit to described Driving Torque T controls to comprise in real time according to judged vehicle operating status:

When judging that vehicle is in astable mode of operation, then amplitude limit is implemented to described Driving Torque T and control;

When judgement vehicle is in steady-working state, then amplitude limit is not implemented to described Driving Torque T and control.

10. judge a system for the vehicle operating status under traction state, it is characterized in that, comprising:

Measurement module, for described Driving Torque T and the described vehicle wheel rotational speed ω of measuring vehicle motor;

Estimation block, for estimating described adhesion moment T _d;

Computing module, for calculating described Driving Torque changing value △ T and described adhesion moment changing value △ T _d;

Determination module, for according to described Driving Torque changing value △ T and described adhesion moment changing value △ T _djudge the vehicle operating status under traction state.

11. systems as claimed in claim 10, is characterized in that, also comprise:

Initialization module, for obtaining the described inertia constant J of vehicle; And/or

Filtration module, for carrying out filtering process to the described vehicle wheel rotational speed ω measuring gained; And/or

Clipping module, implements amplitude limit to described Driving Torque T when being in astable mode of operation for the vehicle under traction state and controls.