CN103612634A - Method for estimating road adhesion coefficient of electromobile driven by distributed hub motor - Google Patents

Abstract

The invention relates to a method for estimating the road adhesion coefficient of an electromobile driven by a distributed hub motor and belongs to the technical field of electromobiles. The current wheel speed, the current vehicle speed and the current driving moment of the electromobile are acquired in real time through a wheel speed sensor, a vehicle speed sensor and a motor controller; the slip rate, the vertical load and the driving force are calculated; the slope of a point corresponding to the current moment on a mu-lambda curve is calculated, if the slope is smaller than m, it is determined that the road adhesion coefficient at the moment is the peak road adhesion coefficient, and if not, the slope at the next moment is calculated continuously; or if the slope in one second is not smaller than m, the largest road adhesion coefficient calculated in one second is the relative peak road adhesion coefficient; by comparing the peak road adhesion coefficients obtained from four tires, whether the current road is a homogeneous road or a bisectional road or a butt-joint road or a single-wheel independent road is judged. The method is good in robustness, various roads can be well identified, and the method is suitable for estimating the road adhesion coefficients of a vehicle on various roads in the driving process.

Description

The evaluation method of distributing In-wheel motor driving electronlmobil coefficient of road adhesion

Technical field

The present invention relates to a kind of distributing In-wheel motor driving electronlmobil evaluation method of coefficient of road adhesion in the process of moving, particularly a real time measure method for enterprising road wheel tire and the longitudinal attachment characteristic in road surface on actual road surface, belongs to electric vehicle engineering field.

Background technology

Distributing In-wheel motor driving electronlmobil is that wheel hub motor is arranged on respectively in four wheels of electronlmobil or near wheel, there is the features such as response is fast, messenger chain is short, transmission is efficient, compact conformation, taking full advantage of motor accurate surveying and quick controlled feature, is important developing direction of electronlmobil.

The adhesion value variation characteristic of electronlmobil tire on different road surfaces is an important technology index evaluating motor tire performance, and it has material impact to automotive performance.Tire is also an important initial parameter of vehicle dynamic quality and deceleration and stopping performance simulation calculation from the adhesion value variation characteristic between different road surfaces.

All in coefficient of road adhesion identification field, do a lot of work both at home and abroad at present, mainly comprised following several method.

1) the coefficient of road adhesion evaluation method based on coefficient of road adhesion and wheel slip slope of a curve.The method is simply easy to implement, but can only be directed in the situation of automobile in low slip rate, the in the situation that of high slip rate, does not meet linear relationship between slip rate and adhesion value.

2) the coefficient of road adhesion evaluation method based on tire model.The method can obtain the slip characteristic of wheel by tire model, and directly estimates coefficient of road adhesion, and accuracy is higher.But its accuracy is too strong to the tire model dependence adopting, and utilizes complicated tire model to calculate slip rate overlong time, and the tire model of simplification can affect the accuracy of adhesion value again.

Also have a lot of other methods be all take these two kinds as prototype, changed, also respectively have merits and faults.

Summary of the invention

For existing coefficient of road adhesion, estimate inaccurate problem, the object of the invention is to provide a kind of coefficient of road adhesion evaluation method of distributing In-wheel motor driving electronlmobil, in order to accurate estimation road surface situation, so that it is safer to travel.

For achieving the above object, the present invention takes following technical scheme:

The coefficient of road adhesion evaluation method of the electronlmobil of distributing In-wheel motor driving, the method step is:

1) set up the estimating system of a kind of battery-driven car road surface adhesion value, comprising: be arranged on the drive torque sensor on electric machine controller, the wheel speed sensors that is arranged on wheel place, car speed sensor, wheel slip computing module, coefficient of road adhesion estimation module, the tire model module of simplifying.Coefficient of road adhesion estimation module has the algorithm of estimating coefficient of road adhesion based on coefficient of road adhesion and wheelslip rate curve.

2), in the situation that ignoring tire drag, according to formula (1), tire propulsive effort is carried out to real-time monitored.

$F_i=(T_z-J_{\mathrm{\ω}}*\stackrel{\·}{\mathrm{\ω}})/R,---\left(1\right)$

In formula, R-vehicle wheel roll radius, J ω-vehicle wheel rotation inertia,

-wheel angular acceleration, F _z-wheel vertical load, T _z-drive torque.

Wherein, T _zbeing drive torque, is known.If angular speed of wheel sensor gathers front and back adjacent moment k-1 and k, interval time is T, and the wheel speed signal ω (k) that Real-time Collection arrives and ω (k-1), so there is (2) formula to calculate wheel heart acceleration.

$\stackrel{\·}{\mathrm{\ω}}=\frac{\mathrm{\ω}\left(k\right)-\mathrm{\ω}(k-1)}{T},---\left(2\right)$

So the formula of obtaining (3) is calculated tire propulsive effort:

$F_i\left(k\right)=[T_z-J_{\mathrm{\ω}}*\frac{\mathrm{\ω}\left(k\right)-\mathrm{\ω}(k-1)}{T}]/R,---\left(3\right)$

The vertical load of distributing In-wheel motor driving electronlmobil is calculated as follows, and the vertical load of the left and right wheels before and after wherein getting is equal,

$F_{z1}=\frac{\mathrm{mg}{L}_r-\mathrm{mah}}{2L},---\left(4\right)$

$F_{z2}=\frac{\mathrm{mg}{L}_f-\mathrm{mah}}{2L},---\left(5\right)$

In formula, L _r-vehicle barycenter is to the vertical distance of rear axle, L _f-vehicle barycenter is to the vertical distance of front-wheel wheel shaft, the vertical distance between L-front and back wheel wheel shaft, and h-vehicle barycenter is to the height on ground.

Wherein, a is electronlmobil acceleration/accel, establishes car speed sensor and gathers front and back adjacent moment k-1 and k, and interval time is T, the wheel speed signal V(k that Real-time Collection arrives) and V(k-1), so there is (6) formula to calculate pickup.

$a=\frac{v\left(k\right)-v(k-1)}{T},$

Current coefficient of road adhesion is calculated by formula (6):

μ（k）=F _i（k）/F _zi （6）

The slip rate of current time calculates and can be calculated by formula (7):

$\mathrm{\λ}\left(k\right)=\left|\frac{\mathrm{\ω}\left(k\right)*R-v_w\left(k\right)}{\max \{\mathrm{\ω}\left(k\right)*R,v_w\left(k\right)\}}\right|,---\left(7\right)$

In formula, λ-slip rate, ω-angular speed of wheel, R-vehicle wheel roll radius, v _w-the speed of a motor vehicle.

3) through type (8) calculates current coefficient of road adhesion and slip rate slope of a curve:

$p=\frac{\mathrm{d\μ}}{\mathrm{d\λ}}=\frac{\mathrm{\μ}\left(k\right)-\mathrm{\μ}(k-1)}{\mathrm{\λ}\left(k\right)-\mathrm{\λ}(k-1)}---\left(8\right)$

Relatively: | p|<m, (9)

Wherein, m is setting value;

I) when | during p|<m, can judge that current coefficient of road adhesion is peak value coefficient of road adhesion, and zone bit flag=0 is set; If the absolute value of slope p | p|>m, continue to calculate next slope p constantly, until | p|<m;

If ii) in 1s, slope p does not still reach | p|<m, being taken at the maximum coefficient of road adhesion calculating in 1s is relative peak value of road adhesion coefficient, and sets up a zone bit flag=1;

4) calculate respectively peak value of road adhesion coefficient and the zone bit of four tires, be designated as u1, u2, u3, u4, flag1, flag2, flag3, flag4; Wherein, u1, flag1 represent peak value of road adhesion coefficient and the zone bit of the near front wheel; U2, flag2 represent peak value of road adhesion coefficient and the zone bit of off front wheel; U3, flag3 represent peak value of road adhesion coefficient and the zone bit of left rear wheel; U4, flag4 represent peak value of road adhesion coefficient and the zone bit of off hind wheel;

Peak value of road adhesion coefficient u1, u2, u3, u4 and zone bit flag1, the flag2, flag3, the flag4 that compare four tires; Further judge that current road surface is homogeneous road surface, splits road surface, docks road surface or single-wheel independence road surface;

If the zone bit of four tires is identical, the difference of peak value of road adhesion coefficient is in n, and n is setting value, judges that current road surface is as homogeneous road surface, its coefficient of road adhesion U=(u1+u2+u3+u4)/4;

If the first two tire is identical with latter two designation of tyres position, and the difference of peak value of road coefficient is respectively all in n, and n is setting value, judges that current road surface is as docking road surface, its coefficient of road adhesion U1=(u1+u2)/2, U2=(u3+u4)/2;

If two, left side tire is identical with designation of tyres position, two, the right, and the difference of coefficient of road adhesion is respectively all in n, and n is setting value, judges that current road surface is as splitting road surface, its coefficient of road adhesion U1=(u1+u3)/2, U2=(u2+u4)/2;

If do not meet above-mentioned situation, judge that current road surface is as single-wheel independence road surface, coefficient of road adhesion according to circumstances calculates.

The present invention is owing to taking above technical scheme, it has the following advantages: the present invention, first by current wheel speed, the speed of a motor vehicle and the drive torque of wheel speed sensors, car speed sensor and electric machine controller Real-time Collection electronlmobil, then calculates respectively current slip rate, vertical load and the propulsive effort of four tires.The slope that calculates current time corresponding point on μ-λ curve by these three values, when slope approaches zero, the coefficient of road adhesion of judging this moment is peak value of road adhesion coefficient, otherwise continues to calculate next slope constantly; If or slope does not approach zero in 1s, getting the maximum coefficient of road adhesion calculating in 1s is relative peak value of road adhesion coefficient.By the coefficient of road adhesion relatively being calculated by four tires, judge that current road surface is homogeneous road surface, splits road surface, docks road surface or single-wheel independence road surface.Robustness of the present invention is good, can identify preferably various road surface, is applicable to the vehicle real-time estimation of the coefficient of road adhesion on various road surfaces in the process of moving.

Accompanying drawing explanation

Fig. 1 is phylogenetic relationship schematic diagram of the present invention.

Fig. 2 is method flow diagram of the present invention.

The specific embodiment

Below in conjunction with drawings and Examples, describe the present invention.

Fig. 1 is phylogenetic relationship schematic diagram of the present invention.System comprises a vehicular drive moment sensor, wheel speed sensors, speed of a motor vehicle observer as shown in Figure 1.Coefficient of road adhesion estimation block, comprises tire force estimation module, wheel slip computing module and simplifies tire model.

Based on above system, the present invention comprises the following steps the real-time estimation method of the coefficient of road adhesion in Vehicle Driving Cycle process, as shown in Figure 2 (Fig. 2 is method flow diagram of the present invention).

The coefficient of road adhesion evaluation method of the electronlmobil of distributing In-wheel motor driving, the method step is:

1), in the situation that ignoring tire drag, according to formula (1), tire propulsive effort is carried out to real-time monitored.

$F_i=(T_z-J_{\mathrm{\&omega;}}*\stackrel{\&CenterDot;}{\mathrm{\&omega;}})/R,---\left(1\right)$

In formula, R-vehicle wheel roll radius, J ω-vehicle wheel rotation inertia,

-wheel angular acceleration, F _z-wheel vertical load, T _z-drive torque.

Wherein, T _zbeing drive torque, is known.If angular speed of wheel sensor gathers front and back adjacent moment k-1 and k, interval time is T, and the wheel speed signal ω (k) that Real-time Collection arrives and ω (k-1), so there is (2) formula to calculate wheel heart acceleration.

$\stackrel{\&CenterDot;}{\mathrm{\&omega;}}=\frac{\mathrm{\&omega;}\left(k\right)-\mathrm{\&omega;}(k-1)}{T},---\left(2\right)$

So the formula of obtaining (3) is calculated tire propulsive effort:

$F_i\left(k\right)=[T_z-J_{\mathrm{\&omega;}}*\frac{\mathrm{\&omega;}\left(k\right)-\mathrm{\&omega;}(k-1)}{T}]/R,---\left(3\right)$

The vertical load of distributing In-wheel motor driving electronlmobil is calculated as follows, and the vertical load of the left and right wheels before and after wherein getting is equal,

$F_{z1}=\frac{\mathrm{mg}{L}_r-\mathrm{mah}}{2L},---\left(4\right)$

$F_{z2}=\frac{\mathrm{mg}{L}_f-\mathrm{mah}}{2L},---\left(5\right)$

In formula, L _r-vehicle barycenter is to the vertical distance of rear axle, L _f-vehicle barycenter is to the vertical distance of front-wheel wheel shaft, the vertical distance between L-front and back wheel wheel shaft, and h-vehicle barycenter is to the height on ground.

Wherein, a is electronlmobil acceleration/accel, establishes car speed sensor and gathers front and back adjacent moment k-1 and k, and interval time is T, the wheel speed signal v(k that Real-time Collection arrives) and v(k-1), so there is (6) formula to calculate pickup.

$a=\frac{v\left(k\right)-v(k-1)}{T},$

The current coefficient of road adhesion that utilizes can be calculated by formula (6):

μ（k）=F _i（k）/F _zi，（6）

The slip rate of current time calculates and can be calculated by formula (7):

$\mathrm{\&lambda;}\left(k\right)=\left|\frac{\mathrm{\&omega;}\left(k\right)*R-v_w\left(k\right)}{\max \{\mathrm{\&omega;}\left(k\right)*R,v_w\left(k\right)\}}\right|,---\left(7\right)$

In formula, λ-slip rate, ω-angular speed of wheel, R-vehicle wheel roll radius, v _w-the speed of a motor vehicle.

2) through type (8) calculates current coefficient of road adhesion and slip rate slope of a curve:

$p=\frac{\mathrm{d\&mu;}}{\mathrm{d\&lambda;}}=\frac{\mathrm{\&mu;}\left(k\right)-\mathrm{\&mu;}(k-1)}{\mathrm{\&lambda;}\left(k\right)-\mathrm{\&lambda;}(k-1)}---\left(8\right)$

Relatively: | p|<m, (9),

Wherein, m is 0.1 here; N is 0.05.

I) when | during p|<0.1, can judge that current coefficient of road adhesion is peak value coefficient of road adhesion, and zone bit flag=0 is set; If the absolute value of slope p | p|>0.1, continue to calculate next slope p constantly, until | p|<0.1;

If ii) in 1s, slope p does not still reach | p|<0.1, being taken at the maximum coefficient of road adhesion calculating in 1s is relative peak value of road adhesion coefficient, and sets up a zone bit flag=1;

3) calculate respectively peak value of road adhesion coefficient and the zone bit of four tires, be designated as u1, u2, u3, u4, flag1, flag2, flag3, flag4; Wherein, u1, flag1 represent peak value of road adhesion coefficient and the zone bit of the near front wheel; U2, flag2 represent peak value of road adhesion coefficient and the zone bit of off front wheel; U3, flag3 represent peak value of road adhesion coefficient and the zone bit of left rear wheel; U4, flag4 represent peak value of road adhesion coefficient and the zone bit of off hind wheel;

Peak value of road adhesion coefficient u1, u2, u3, u4 and zone bit flag1, the flag2, flag3, the flag4 that compare four tires; Further judge that current road surface is homogeneous road surface, splits road surface, docks road surface or single-wheel independence road surface;

If the zone bit of four tires is identical, the difference of peak value of road adhesion coefficient is in n, and n is setting value, judges that current road surface is as homogeneous road surface, its coefficient of road adhesion U=(u1+u2+u3+u4)/4;

If the first two tire is identical with latter two designation of tyres position, and the difference of peak value of road coefficient is respectively all in n, and n is setting value, judges that current road surface is as docking road surface, its coefficient of road adhesion U1=(u1+u2)/2, U2=(u3+u4)/2;

If two, left side tire is identical with designation of tyres position, two, the right, and the difference of coefficient of road adhesion is respectively all in n, and n is setting value, judges that current road surface is as splitting road surface, its coefficient of road adhesion U1=(u1+u3)/2, U2=(u2+u4)/2;

If do not meet above-mentioned situation, judge that current road surface is as single-wheel independence road surface, coefficient of road adhesion according to circumstances calculates.

The present invention is owing to taking above technical scheme, it has the following advantages: the present invention, first by current wheel speed, the speed of a motor vehicle and the drive torque of wheel speed sensors, car speed sensor and electric machine controller Real-time Collection electronlmobil, then calculates respectively current slip rate, vertical load and the propulsive effort of four tires.The slope that calculates current time corresponding point on μ-λ curve by these three values, when slope approaches zero, the coefficient of road adhesion of judging this moment is peak value of road adhesion coefficient.By the coefficient of road adhesion relatively being calculated by four tires, judge that current road surface is homogeneous road surface, splits road surface, docks road surface or single-wheel independence road surface.Robustness of the present invention is good, can identify preferably various road surface, is applicable to the vehicle real-time estimation of the coefficient of road adhesion on various road surfaces in the process of moving.

Claims (3)

1. the evaluation method of distributing In-wheel motor driving electronlmobil coefficient of road adhesion, is characterized in that, the method contains in steps:

1) ignore tire drag, according to formula (1), tire propulsive effort is carried out to real-time monitored;

Described formula (1) is: $F_i=(T_z-J_{\mathrm{\&omega;}}*\stackrel{\&CenterDot;}{\mathrm{\&omega;}})/R,---\left(1\right)$

In formula, R-vehicle wheel roll radius, J _ω-vehicle wheel rotation inertia,

-wheel angular acceleration, F _z-wheel vertical load, T _z-drive torque;

Wherein, T _zbeing drive torque, is known; If angular speed of wheel sensor gathers front and back adjacent moment k-1 and k, interval time is T, the wheel speed signal ω (k) that Real-time Collection arrives and ω (k-1), so calculate wheel heart acceleration by formula (2):

$\stackrel{\&CenterDot;}{\mathrm{\&omega;}}=\frac{\mathrm{\&omega;}\left(k\right)-\mathrm{\&omega;}(k-1)}{T},---\left(2\right)$

According to formula (3), calculate tire propulsive effort:

$F_i\left(k\right)=[T_z-J_{\mathrm{\&omega;}}*\frac{\mathrm{\&omega;}\left(k\right)-\mathrm{\&omega;}(k-1)}{T}]/R,---\left(3\right)$

The vertical load of distributing In-wheel motor driving electronlmobil is calculated as follows, and the vertical load of the left and right wheels before and after wherein getting is equal, that is:

$F_{z1}=\frac{\mathrm{mg}{L}_r-\mathrm{mah}}{2L},---\left(4\right)$

$F_{z2}=\frac{\mathrm{mg}{L}_f-\mathrm{mah}}{2L},---\left(5\right)$

In formula, L _r-vehicle barycenter is to the vertical distance of rear axle, L _f-vehicle barycenter is to the vertical distance of front-wheel wheel shaft, the vertical distance between L-front and back wheel wheel shaft, and h-vehicle barycenter is to the height on ground;

Wherein, a is electronlmobil acceleration/accel, establishes car speed sensor and gathers front and back adjacent moment k-1 and k, and interval time is T, the wheel speed signal v(k that Real-time Collection arrives) and v(k-1), so calculate pickup by following formula:

$a=\frac{v\left(k\right)-v(k-1)}{T},$

Current coefficient of road adhesion is calculated by formula (6):

μ（k）=F _i（k）/F _zi（6）

The slip rate of current time calculates and can be calculated by formula (7):

$\mathrm{\&lambda;}\left(k\right)=\left|\frac{\mathrm{\&omega;}\left(k\right)*R-v_w\left(k\right)}{\max \{\mathrm{\&omega;}\left(k\right)*R,v_w\left(k\right)\}}\right|,---\left(7\right)$

In formula, λ-slip rate, ω-angular speed of wheel, R-vehicle wheel roll radius, v _w-the speed of a motor vehicle;

2) through type (8) calculates current coefficient of road adhesion and slip rate slope of a curve p:

$p=\frac{\mathrm{d\&mu;}}{\mathrm{d\&lambda;}}=\frac{\mathrm{\&mu;}\left(k\right)-\mathrm{\&mu;}(k-1)}{\mathrm{\&lambda;}\left(k\right)-\mathrm{\&lambda;}(k-1)}---\left(8\right)$

Relatively: | p|<m, (9)

Wherein, m is setting value;

When | during p|<m, can judge that current coefficient of road adhesion is peak value coefficient of road adhesion, and zone bit flag=0 is set; If | p|>m, continue to calculate next slope p constantly, until | p|<m;

If slope p does not still reach in 1s | p|<m, being taken at the maximum coefficient of road adhesion calculating in 1s is relative peak value of road adhesion coefficient, and sets up a zone bit flag=1;

3) calculate respectively peak value of road adhesion coefficient and the zone bit of four tires, be designated as u1, u2, u3, u4, flag1, flag2, flag3, flag4; Wherein, u1, flag1 represent peak value of road adhesion coefficient and the zone bit of the near front wheel; U2, flag2 represent peak value of road adhesion coefficient and the zone bit of off front wheel; U3, flag3 represent peak value of road adhesion coefficient and the zone bit of left rear wheel; U4, flag4 represent peak value of road adhesion coefficient and the zone bit of off hind wheel;

Peak value of road adhesion coefficient u1, u2, u3, u4 and zone bit flag1, the flag2, flag3, the flag4 that compare four tires; Further judge that current road surface is homogeneous road surface, splits road surface, docks road surface or single-wheel independence road surface;

If the zone bit of four tires is identical, the difference of peak value of road adhesion coefficient is in n, and n is setting value, judges that current road surface is as homogeneous road surface, its coefficient of road adhesion U=(u1+u2+u3+u4)/4;

If the first two tire is identical with latter two designation of tyres position, and the difference of peak value of road coefficient is respectively all in n, and n is setting value, judges that current road surface is as docking road surface, its coefficient of road adhesion U1=(u1+u2)/2, U2=(u3+u4)/2;

If two, left side tire is identical with designation of tyres position, two, the right, and the difference of coefficient of road adhesion is respectively all in n, and n is setting value, judges that current road surface is as splitting road surface, its coefficient of road adhesion U1=(u1+u3)/2, U2=(u2+u4)/2;

If do not meet above-mentioned situation, judge that current road surface is as single-wheel independence road surface, coefficient of road adhesion according to circumstances calculates.

2. the evaluation method of distributing In-wheel motor driving electronlmobil coefficient of road adhesion according to claim 1, is characterized in that, described m is 0.1.

3. the evaluation method of distributing In-wheel motor driving electronlmobil coefficient of road adhesion according to claim 1, is characterized in that, described n is 0.05.

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