CN1329722C - Cargo vehicle ABS road identification method - Google Patents

Abstract

The present invention makes a request for protecting a cargo vehicle anti-skid brake system (ABS) road identification method which relates to the technical field of electronic control of vehicles. The maximum wheel speed of a vehicle wheel is used as the reference speed of a vehicle, and then ground friction force exerted to each wheel is calculated and obtained according to the angular acceleration of the wheel; the weight of the vehicle and the parameter of a vehicle body under the condition of carrying load are calculated, and therefore, the positive pressure of the vehicle wheels is obtained. Consequently, a ground adhesion coefficient is calculated and obtained, and the skid rate of the wheel is calculated. Theoretical adhesion coefficients of different road surfaces under current skid rate are calculated according to a theoretical formula. The adhesion coefficients calculated under the two conditions are compared so as to identify a road surface condition. The cargo vehicle anti-skid brake system (ABS) road identification method is suitable for vehicle anti-skid brake systems (ABS) and particularly can solve road surface identification under the condition that cargo vehicles have different loads.

Description

A kind of cargo vehicle ABS road identification method

Technical field

The invention belongs to the auto electronic control technology field, be specifically related to a kind of method of cargo vehicle ABS road identification.

Background technology

The ABS anti-locking system for car is the important electron system that guarantees automobile not locking of wheel in brake process, for guaranteeing not locking of wheel, can brake with fast speeds again simultaneously, ABS must adopt different control strategies at different road surface situations, so the ABS system must real-time identification road surface situation.Yet because the number of sensors that body of a motor car loads is limited, the information that ABS can obtain has only the speed of wheel, so ABS road identification algorithm must identify the information on road surface from finite information.College journal in June, 2003 northeastward such as Chen Jun for this reason, " based on the ABS road surface identification of competition neural network " that the 24th the 6th phase of volume delivered adopts nerual network technique to carry out the road identification technology, agricultural mechanical journal, " the discerning the ABS Study on Fuzzy Controlling System automatically based on road " of delivering September calendar year 2001 adopted the method identification road surface of theoretical retarded velocity of contrast wheel and wheel actual deceleration degree, Jin-Oh Hahn etc. adopt based on the method identification tire of GPS and the friction factor on ground (Jin-Oh Hahn, Rajesh Rajamani, and Lee Alexander.GPS-Based Real-Time Identification of Tire-RoadFriction Coefficient, IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, VOL.10, NO.3).Yet make a general survey of above these methods, need a large amount of sample datas that network is trained based on neural network method, the method of theoretical retarded velocity of contrast wheel and wheel actual deceleration degree need be known the quality of automobile, and the ABS system and do not know any quality of lorry loading after gross mass, so this method can not realize the automatic identification on road surface in the ABS of bogie, and need automobile to be equipped with GPS based on the method for GPS, so cost is higher.

Summary of the invention

The present invention relates to a kind of with low costly, computing method are simple, do not need the new method that is applicable to cargo vehicle ABS road identification that network is trained.The present invention proposes a kind of method of cargo vehicle ABS road identification, its objective is that solving a large amount of sample data of needs that exists in the existing road surface recognition methods trains, or can't obtain bogie quality and the high shortcoming of manufacturing cost in the method for theoretical retarded velocity of contrast wheel and wheel actual deceleration degree.

Solving the problems of the technologies described above the technical scheme that is adopted is: utilize wheel speed sensors wheel speed signal in the line drawing braking procedure, obtain the angular acceleration of 4 wheels in the automobile brake, and the wheel speed of extraction maximum is as the reference speed of automobile, calculate the braking moment that automotive brake produces according to formula then, again by the braking moment of angular acceleration and 4 wheel drags of 4 wheels, calculate the frictional ground force that 4 wheels are subjected to respectively, the frictional ground force that is subjected to according to 4 wheels and the acceleration of vehicle body, calculate the quality of automobile, go out the height of center of mass of automobile and barycenter distance by the Mass Calculation of automobile again apart from front axle and rear axle, again according to the quality of automobile, the height of center of mass of automobile and barycenter are apart from the distance of front axle and rear axle, the acceleration of automobile, calculate the normal pressure that 4 wheels of automobile are subjected to, the frictional ground force that is subjected to by normal pressure and wheel calculates current attachment coefficient again.Calculate the theoretical attachment coefficient on different road surfaces under current slip rate at last by theoretical formula, the attachment coefficient that will be obtained by normal pressure and friction calculation and the theoretical attachment coefficient on different road surfaces calculate continuously and contrast, if the attachment coefficient that obtains by normal pressure and friction calculation double all with certain road surface under attachment coefficient approaching, but the then current pavement behavior of identification, and judgement wheel is on this road surface.

Description of drawings

Fig. 1 truck ABS road identification method process flow diagram

Fig. 2 four-wheel car system model

Embodiment

Now reach embodiment in conjunction with the accompanying drawings the implementation process of this road identification method is specifically described, Figure 1 shows that truck ABS road identification method process flow diagram, its step is as follows:

1, utilize wheel speed sensors wheel speed signal in the line drawing braking procedure: the linear velocity ν of automobile, angular speed of wheel ω, obtain the slip rate of 4 wheels in the automobile brake, the slip rate of wheel when calculating braking according to formula then: $S=\frac{v-\mathrm{r\ω}}{v}\×100\%$

Rolling radius when wherein r represents that wheel is not subjected to ground damping force.

2, the gaseous tension according to brake chamber obtains the braking moment that automotive brake produces

Obtain empirical value by experiment and deposit in the database, obtain detent application factor k _p, brake chamber pressure P, overcome the required pressure P of spring force in the checking cylinder _mThe braking moment of wheel provides the gaseous tension of brake chamber and braking moment M by the pressure of the gas generation of the brake chamber of detent _bRelation satisfy following formula: $M_b=\left\{\begin{array}{cc}0& p-p_m<0\\ k_p(p-p_m)& p-p_m>0\end{array}\right.$

The gaseous tension of brake chamber is relevant with brake chamber inflationtime and inflation end of a period value, and its " pressure-time " dynamic characteristic curve is a kind of curve of asymptotic expression, is similar to sigmoid curve, adopts exponential form S type curvilinear equation: $p\left(t\right)=\frac{a}{1+b\&CenterDot;e^{m\&CenterDot;t}}$ Wherein a is an air chamber inflation end of a period value, and b and m are two gains, do not have concrete physical significance, can determine by test.

3, calculate 4 frictional ground forces that wheel is subjected to

Automobile wheel in braking procedure is subjected to the effect of the moment of friction on braking moment that detent produces and ground, the braking moment that detent produces will make wheel decelerates, and the moment of friction on ground will make wheel quicken, the vehicle wheel rotational speed that records according to wheel speed sensors, can obtain the angular acceleration of wheel, under the known situation of the moment of inertia of wheel, the friction force F that wheel is subjected to _SiCan calculate by following formula

M wherein _BiBe the braking moment of i wheel, J _iThe parameters such as moment of inertia that are i wheel deposit in the database by measuring to extract, Be the angular acceleration of i wheel, the wheel velocity that records for twice by front and back calculates with method of difference.

4, by respectively with the maximal value of the wheel speed that records for twice speed as vehicle body, calculate the acceleration of vehicle body then with method of difference, the frictional ground force that is subjected to according to 4 wheels and the acceleration of vehicle body, calculate the quality of automobile, go out the height of center of mass of automobile and barycenter distance by the Mass Calculation of automobile again apart from front axle and rear axle.The frictional ground force that is subjected to according to 4 wheels calculates the quality of automobile

∑ F wherein _SiBe the friction force that is subjected to of wheel and,  _xBe automobile in linear acceleration longitudinally,

Be the angular velocity of Vehicular yaw, v _yIt is the lateral direction of car movement velocity.

With the reference speed of maximum wheel speed, set up four-wheel car system model as shown in Figure 2, (v wherein as automobile _xBe vehicular longitudinal velocity, v _yBe vehicle lateral speed, v is a car speed, F _XiBe the longitudinal frictional force that wheel is subjected to, F _YiBe the side-friction that wheel is subjected to,  is the Vehicular yaw angle, β be vehicle body and vertically between angle), as shown in Figure 2, v _y=vsin β because β is very little, so sin β is approximately 0, that is to say v _yCan be approximately 0, and the speed available reference speed approximate representation of body of a motor car, the method of calculating reference velocity roughly comprises maximum wheel speed method, slope method and X-II method and recurrence method, the reference velocity that several method calculates is all very approaching with the vehicle body speed that records with speed pickup, consider the easy of maximum wheel speed method, can use the computing method of maximum wheel speed method as vehicle body acceleration, following formula can be reduced to thus $M=\frac{\mathrm{\&Sigma;}{F}_{\mathrm{si}}}{{\stackrel{.}{v}}_x}.$ If car mass was M when bogie was unloaded ₁, front axle is a to the distance of barycenter ₁, rear axle is b to the distance of barycenter ₁, height of center of mass is h ₁, bogie full load car mass is M ₂, front axle is a to the distance of barycenter ₂, rear axle is b to the distance of barycenter ₂, height of center of mass is h ₂, then can be similar to the increase of thinking along with dead weight capacity, linear relationship is satisfied in the variation apart from a of the variation of automobile height of center of mass h and automobile centroid distance front axle, promptly

$a=\frac{a_2-a1}{M_2-M_1}M+\frac{a_1{M}_2-a_2{M}_1}{M_2-M_1}$

$h=\frac{h_2-h1}{M_2-M_1}M+\frac{h_1{M}_2-h_2{M}_1}{M_2-M_1}$

5, according to car mass, the frictional ground force that normal pressure that vehicle body acceleration and vehicle body calculation of parameter wheel are subjected to and wheel are subjected to calculates attachment coefficient

The automobile normal pressure that wheel is subjected in braking procedure is not only the function of the quality of automobile, and is the function of the linear acceleration and the vehicle body parameter of automobile, and its relation is as follows:

$\left\{\begin{array}{c}{N}_1=M((b\&CenterDot;g-{\stackrel{.}{v}}_{x}h)/2L+{\stackrel{.}{v}}_{y}h/2C)\\ N_2=M((b\&CenterDot;g-{\stackrel{.}{v}}_{x}h)/2L-{\stackrel{.}{v}}_{y}h/2C)\\ N_3=M((a\&CenterDot;g+{\stackrel{.}{v}}_{x}h)/2L+{\stackrel{.}{v}}_{y}h/2C)\\ N_4=M((a\&CenterDot;g+{\stackrel{.}{v}}_{x}h)/2L-{\stackrel{.}{v}}_{y}h/2C)\end{array}\right.$ N wherein _iBe i the normal pressure that wheel is subjected to, M is a complete vehicle quality, v _xBe vehicular longitudinal velocity, v _yBe vehicle lateral speed, C vehicle wheelbase, a, b are front axle and the rear axle distances to the vehicle barycenter, and L is a vehicle wheelbase.

Because v _yVery little, following formula can be reduced to $\left\{\begin{array}{c}{N}_1=M(b\&CenterDot;g-{\stackrel{.}{v}}_{x}h)/2L\\ N_2=M(b\&CenterDot;g-{\stackrel{.}{v}}_{x}h)/2L\\ N_3=M(a\&CenterDot;g+{\stackrel{.}{v}}_{x}h)/2L\\ N_4=M(a\&CenterDot;g+{\stackrel{.}{v}}_{x}h)/2L\end{array}\right.$

Then the attachment coefficient on any one wheel and ground can be tried to achieve by following formula: ${\mathrm{\&mu;}}_i=\frac{N_i}{F_{\mathrm{si}}}$

6, according to the current road surface slip rate of sensor acquisition, calculate the theoretical attachment coefficient on different road surfaces under current slip rate by theoretical formula, and deposit in the storer.Automobile is when different road travelings, and the friction force that wheel is subjected to is relevant with slip rate, under identical slip rate s, and the attachment coefficient μ difference that different road surfaces produce, its relation is as follows:

The current attachment coefficient that will be obtained by normal pressure and friction calculation and the theoretical attachment coefficient of corresponding road surface calculate continuously and contrast, if current attachment coefficient double all with certain road surface under theoretical attachment coefficient approaching, then can judge wheel on this road surface, and the pavement state of automobile current driving.

The inventive method is simple, calculate rapidly, only need calculate the frictional ground force that wheel be subjected to and the quality of automobile according to the angular acceleration of 4 wheels, calculate the normal pressure that wheel is subjected to again thus and obtain current attachment coefficient, slip rate according to wheel calculates the theoretical attachment coefficient of wheel under different road surfaces then, at last current attachment coefficient and theoretical attachment coefficient is compared the pavement state of judging running car thus.The road identification method that this method has overcome based on neural network needs a large amount of sample datas that network is trained, and the high shortcoming of cost.

Claims (5)

1, a kind of cargo vehicle ABS road identification method is characterized in that, comprises the steps:

(1) wheel speed sensors automobile wheel speed signal in the line drawing braking procedure is according to the slip rate of wheel in the wheel speed signal calculating automobile brake;

(2) gaseous tension according to brake chamber calculates the braking moment that automotive brake produces;

(3) braking moment that produces of the detent that is subjected to by wheel and the angular acceleration of wheel are determined the frictional ground force that wheel is subjected to;

(4), determine that according to quality the height of center of mass of automobile and barycenter apart from the distance of front axle and rear axle, determine the normal pressure that wheel is subjected to according to quality, vehicle body acceleration and vehicle body parameter again according to the quality of the acceleration calculation automobile of frictional ground force and vehicle body;

(5) frictional ground force and the normal pressure that is subjected to according to wheel determined current attachment coefficient;

(6) be extracted in the theoretical attachment coefficient on different road surfaces under the current slip rate;

(7) more current attachment coefficient and theoretical attachment coefficient are if double comparative result near the theoretical attachment coefficient under certain road surface, judges that then wheel is on this road surface.

2, method according to claim 1 is characterized in that: described wheel speed signal comprises linear velocity, the angular speed of wheel of automobile.

3, method according to claim 1 is characterized in that: the vehicle wheel rotational speed that records according to wheel speed sensors is determined the angular acceleration of wheel, adopts maximum wheel speed method to calculate the acceleration of vehicle body.

4, according to one of them described method of claim 1 to 3, it is characterized in that: the gaseous tension P of braking moment Mb and brake chamber satisfies following relational expression: $M_b=\left\{\begin{array}{cc}0& P-P_m<0\\ k_p(P-P_m)& P-P_m>0\end{array}\right.$ , wherein, P _mFor overcoming the required pressure of spring force in the checking cylinder, k _pBe the detent application factor.

5, according to one of them described method of claim 1 to 3, it is characterized in that: by formula ${\mathrm{\&mu;}}_i=\frac{N_i}{F_{\mathrm{si}}}$ Determine current attachment coefficient μ _i, N wherein _iAnd F _SiRepresent normal pressure and frictional ground force that i wheel is subjected to respectively.

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