DE102005062282A1 - Evaluation device for center of gravity (CG) of vehicle includes calculator processing CG values and producing combined probability value for CG height - Google Patents

Abstract

The evaluation device (10) includes a calculator (11) to evaluate the CG of a vehicle depending on reported operating state values (a y, psi, a x), from which several CG position values are produced. The calculator processes the CG position values to produce an individual probability value from each of them, and then uses these to produce a combined probability value for the CG height and of CG class.

Description

The The invention relates to an apparatus and a method for estimate the center of gravity in a vehicle having the features of the preamble of claim 1

In front All terrain vehicles due to their design one compared to ordinary road vehicles increased Focus position on. This has an effect on the driving dynamics Behavior of the vehicle. So the tipping influence of lateral acceleration, the vehicle when cornering, an evasive maneuver or learns the like, with the height to the center of gravity.

Height Lateral acceleration amounts can cause that the inside of the vehicle wheels the contact to the road surface lose and the vehicle difficult or at worst ever is no longer controllable. The amount of lateral acceleration, where this is the case defines the respective overturning limit of the vehicle. The overturning limit takes in turn with the height of the center of gravity from. To a possible Tilting the vehicle to be vehicle-stabilizing Systems, such as the Electronic Stability Program (ESP).

The Electronic Stability Program measures the current actual value of the yaw rate and / or the lateral acceleration of the vehicle and compares this with a given each nen Threshold resulting from the specific overturning limit of the vehicle results. If the current actual value reaches the specified threshold, Thus, vehicle-stabilizing braking interventions are made on individual vehicle wheels.

The Presetting the threshold value is such that an overturning of the Vehicle also in case of unfavorable Loading conditions which leads to an increase of the center of gravity, reliable is avoided. The actual Height of Center of gravity, however, can be considerable at low load of the vehicle differ. In such a case, it would be safe, the Threshold higher accordingly to be set. Thus let unnecessary Brake intervention by the Electronic Stability Program avoid and agility improve the vehicle.

It is regarded as an object of the present invention, a device or specify a method, the one or as possible simple yet accurate estimate the current center of gravity of the vehicle allowed.

To This is the purpose of the Electronic Stability Program and an active chassis provided sensor data evaluated. Since both systems are usually present in the vehicle anyway, it is possible, the estimation the center of gravity without significant additional effort. at The active chassis is in particular an air suspension.

The estimate the center of gravity is preferably such that between at least two load variants (main classes) can be distinguished can. On the one hand, these are loading conditions that are too low Gravity height ("lower Focus "), and on the other hand, if this is not the case ("increased emphasis").

liegt.If the vehicle is occupied only by the driver, the center of gravity height assumes its minimum possible value h _min . By contrast, its maximum possible value h _max indicates the center of gravity height when the vehicle is fully loaded and this carries a corresponding load on the roof. The center of gravity can therefore vary by the value (h _max -h _min ). The center of gravity is considered to be low, if this amount in the interval

lies.

The estimated Balance position or height is used in particular for tuning safety-relevant vehicle systems. The case that mistakenly is therefore assumed that the center of gravity is too low excluded.

It is therefore advantageous if a safety tolerance in the amount of twice the standard deviation σ between the respectively estimated center of gravity height and the lower interval limit (h _max - h _min ) / 2 is maintained. If this criterion is fulfilled, assuming a Gaussian normal distribution, it can be assumed with a probability of 97.85% that the vehicle currently has a low center of gravity.

der auftretenden Beladungszustände, bei denen das Fahrzeug einen niedrigen Schwerpunkt aufweist, auch als solche erkannt.Proportionately then only

the occurring loading conditions in which the vehicle has a low center of gravity, also recognized as such.

The Standard deviation σ can but not be chosen arbitrarily small. The smaller this one is, the lower the probability that driving conditions occur in which the center of gravity height at all estimate leaves. In the following, the standard deviation σ is specified such that at least 70 % of during of the driving operation occurring loading conditions, which leads to a low Focus on also be recognized as such.

betragen, um eine zuverlässige Aussage dahingehend treffen zu können, ob der aktuelle Schwerpunkt des Fahrzeugs niedrig ist oder nicht.If, for example, h _min = 69 cm, h _max = 80 cm are set, the result is a standard deviation of σ = 1.18 cm according to equation (1.2). The percentage deviation in the estimate of the center of gravity height may then be at most relative to the respective value (h _max -h _min )

in order to make a reliable statement as to whether the current center of gravity of the vehicle is low or not.

The inventive device or the inventive method will be explained in more detail below with reference to the accompanying drawings. there demonstrate:

1 a schematically illustrated embodiment of the device according to the invention,

2 3 is a diagram showing an exemplary spring characteristic of an air spring strut under the influence of a tension stop spring;

3 a diagram showing an exemplary spring characteristic of an air spring strut under the influence of a buffer,

4 a schematically illustrated vehicle body, which performs a rolling movement under lateral acceleration influence,

5 a diagram showing an exemplary relationship between the mass of the vehicle and the center of gravity,

6 a schematically illustrated vehicle structure which executes a pitching movement under longitudinal acceleration influence,

7 a diagram representing a set of straight lines to be evaluated for the estimation of the center of gravity height,

1 shows an embodiment of the inventive device for estimating the center of gravity of a vehicle. The device 10 also includes an active landing gear in addition to an electronic stability program. In estimating the center of gravity, components of both systems are used. The active chassis is, for example, an air suspension.

The algorithm used to estimate the center of gravity is provided by the computing and control device 11 evaluated by the Electronic Stability Program. Here are the measurement signals of a lateral acceleration sensor 12 and / or a yaw rate sensor 13 used. These provide an indication of the current transverse acceleration a _y, and yaw rate ψ of the vehicle. The lateral acceleration sensor 12 and / or the yaw rate sensor 13 is also part of the Electronic Stability Program.

The air suspension provides information about the on the vehicle wheels 14 _ij occurring spring forces. These become from the measuring signals of associated pressure sensors 15 _ij and / or Fe derwegsensoren 16 _years determined. The measuring signals also become the arithmetic and control device 11 fed. The pressure sensors 15 _ij and / or the spring travel sensors 16 _years are here air spring legs 20 _years assigned, which is between the vehicle body and the vehicle wheels 14 _ij are located.

Regarding the indexing ij the following agreement is made:

The Electronic Stability Program is designed to increase the driving safety of vehicles, by targeted braking interventions on individual vehicle wheels 14 _ij any impending spinning or tilting of the vehicle is prevented. For this purpose, the electronic stability program permanently compares the driver's default desired driving state with the actual actual driving state of the vehicle. Steering wheel angle sensor, pre-pressure sensor in the brake system and the engine management system provide information about the steering wheel impact as well as the position of the brake and / or accelerator pedal. From this information and from the estimated vehicle speed, the target driving state of the vehicle is determined. To record the actual driving state, information about the engine management system, the wheel speeds and the lateral acceleration sensor 12 and / or the yaw rate sensor 13 used. If the actual driving state differs in an impermissible manner from the predetermined desired driving state, then the electronic stability program adopts vehicle-stabilizing braking interventions on individual vehicle wheels 14 _ij by controlling associated wheel brakes 21 _ij in front.

Of the Ride comfort of a vehicle is essentially due to the driving Occurrence of vertical accelerations determined.

In particular, accelerations in the frequency range between 4 and 8 hertz have noticeable influence on the well-being of the vehicle occupants. The natural frequencies of vehicle body and vehicle wheels 14 _ij should therefore be outside this frequency range. By appropriate tuning of the chassis can be achieved that the natural frequency of the vehicle body is less than a hertz. For this purpose, a relatively soft spring characteristic (low spring stiffness) is required, as it is in particular air springs own.

The Natural frequency of the vehicle body typically depends on the Mass of the vehicle, thus from the respective load. Furthermore, the spring stiffness of the air springs used must be taken into account. The spring stiffness of an air spring hangs again - as in following is shown - by the loading. With a suitable design of the air springs, both Effects - Loading Dependence the natural frequency of the vehicle body and the spring stiffness the air springs - such linked together be that a virtually load-independent natural frequency behavior is achieved.

The The resilient element of the air spring is replaced by that in a rubber bellows trapped air formed. The amount of air in the rubber bellows can be used for the purpose of regulating the vehicle construction level with a Inlet and outlet valves are influenced.

Other components of the air strut 20 _years are a pull stop spring and a buffer. They serve as additional springs, the spring stiffness of the air spring strut 20 _years increase at large deflections to avoid possible damage - especially a "strike through" -.

In the air strut 20 _years Thus, a total of three springs are connected in parallel. The spring force of the Zuganschlagfeder or the buffer results from the associated spring characteristics that reflect the relationship between travel and spring force. The spring characteristics are known from the respective design data of the buffer or the Zuganschlagfeder.

The spring characteristic of the third spring - the actual air spring - depends on the amount of air in the rubber bellows and thus changes depending on an operation of the intake and exhaust valve. The following is an expression for the spring characteristic of the air spring and their dependence on the amount of air to be derived. The starting point of this derivation is the so-called polytropic equation, P ij · V n ij = const. (2.1)

In equation (2.1), n denotes the polytropic exponent, which describes the character of the state change. If the change in state is isotropic, then n = 1, but for adiabatic state changes n ≈ 1.4. Further, V _ij denotes the actual internal volume of the rubber bellows and p _ij the associated internal pressure reduced by the atmospheric pressure.

The internal pressure p _ij exerts a force F _ij on the piston of the air spring, F ij = P ij · A ij , (2.2) where A _{ij is} the pressure-effective cross-sectional area of the piston. If equation (2.1) is solved for p _ij and used in equation (2.2), we obtain

The dependence of the cross-sectional area A _ij and the inner volume V _{ij of} the spring travel s _ij is known from the design data of the air spring.

For the following we assume n = 1. As already mentioned, this value only applies in the case of isotropic state changes. Isotropic changes in state occur when the transition between the different states of rebound or rebound of the air spring is slower than the heat exchange with the environment. The determination of the spring force F _{F, ij} is thus possible only in driving conditions in which the input or Ausfederungsgeschwindigkeit is sufficiently small. During these driving conditions, the proportionality constant in equation (2.3) can also be determined by measuring internal pressure p _ij and internal volume V _{ij of} the rubber bellows. Based on a specific measurement time t ^*, this results in a value of p * / ijV * / ij, whereby this value remains valid as long as the air quantity in the rubber bellows remains unchanged. This follows for the spring force F _ij as a function of the spring travel s _ij

betrachtet. Mit steigender Masse des Fahrzeugs muss die Luftfeder eine dementsprechend höhere Last tragen. Die Luftfederung ist derart konzipiert, dass unabhängig von der Beladung stets das gleiche Fahrzeugniveau aufrechterhalten bleibt. Die Größen A_ij und V_ij werden in diesem Fall konstant gehalten, sodass gemäß Gleichung (2.4) die Federkraft F_ij ausschließ lich durch Änderung des Produkts p * / ijV * / ij an die aktuelle Beladung des Fahrzeugs angepasst werden kann. Das Produkt p * / ijV * / ij muss folglich um den selben Faktor erhöht werden wie die von der Luftfeder zu tragende Last. Dies wirkt sich wiederum auf die Federsteifigkeit c_ij der Luftfeder aus. Da sich die Federsteifigkeit c_ij gemäß Gleichung (2.5) proportional zum Produkt p * / ijV * / ij verhält, nimmt auch diese um den gleichen Faktor zu. Insgesamt ist die Änderung der Federsteifigkeit c_ij somit proportional zur Änderung der von der Luftfeder zu tragenden Last.Based on equation (2.4), the behavior of the air spring can also be determined in the event of a load-related change in the mass of the vehicle. This is the spring stiffness

considered. With increasing mass of the vehicle, the air spring must carry a correspondingly higher load. The air suspension is designed in such a way that the same vehicle level is always maintained regardless of the load. The quantities A _ij and V _ij are kept constant in this case, so that, according to equation (2.4), the spring force F _ij can be adapted exclusively to the current load of the vehicle by changing the product p * / ijV * / ij. The product p * / ijV * / ij must therefore be increased by the same factor as the load to be borne by the air spring. This in turn affects the spring stiffness c _{ij of} the air spring out. Since the spring stiffness c _ij according to equation (2.5) is proportional to the product p * / ijV * / ij, this also increases by the same factor. Overall, the change in the spring stiffness c _{ij is} thus proportional to the change in the load to be borne by the air spring.

How the 2 and 3 can be seen, the spring travel s _ij areas in which the entire spring force F _{ij is applied} exclusively by the air spring, ie neither the Zuganschlagfeder nor the buffer provide a contribution here. For example, this is the range between 0 and 22 mm. Here, the spring stiffness c _{ij of} the air spring strut behaves substantially in proportion to the load to be supported.

In order to be able to calculate the spring force F _{F, ij} , therefore, the actual spring travel s _ij , the internal pressure p * / ij or the internal volume V * / ij during a stationary driving state at the measurement time t ^* , must be the internal volume V _ij as a function of the spring travel s _ij , the cross-sectional area A _{ij of} the piston of the air spring as a function of the spring travel s _ij , as well as the spring characteristic of the Zuganschlagfeder and the buffer be known.

Interrelations are used for the actual estimation of the center of gravity, which are based on an analysis of drive-related movements of the vehicle body under lateral acceleration (a _y , ψ. ≠ 0) and unaccelerated driving (a _y , ψ. ≈ 0).

following become these connections explained and derived from them equations used in the preparation of Algorithms for emphasis estimation be used. The goal is to make statements about the center of gravity at different, independent from each other Because of meeting. Based on the degree of agreement the results obtained in this way Statements about the goodness the esteemed Center of gravity hit become. For this purpose, methods of fuzzy logic are used.

4 shows a schematic representation of a vehicle body under lateral acceleration influence.

ein, in der m die Masse des Fahrzeugs, h den vertikalen Abstand zwischen der Wankachse und dem Schwerpunkt des Fahrzeugs, M₀ ein stationäres Drehmoment um die Wankachse und b die Spurbreite des Fahrzeugs bezeichnet.The lateral acceleration a _y engages in the center of gravity SP of the vehicle and leads to a rolling movement of the vehicle body about the roll axis WA, wherein the air spring struts 20 _years Spring forces F _{ij are} caused to counteract the rolling motion. If the counter-torque generated by the spring forces F _{F, ij} equals the moment which results from the transverse acceleration a _y , then a torque balance of the shape is established

in which m denotes the mass of the vehicle, h the vertical distance between the roll axis and the center of gravity of the vehicle, M ₀ denotes a stationary torque about the roll axis and b the track width of the vehicle.

Above Equation (2.6) is used to estimate the product mh. This Product is particularly sensitive to changes in the center of gravity. On the one hand is the distance h between the roll axis and the center of gravity of the Vehicle approximately twice smaller than the height of the center of gravity compared to the Road surface, on the other hand, the relative changes of h but comparable with those of the center of gravity. The relative changes of h are thus about twice as high as the center of gravity height. Further the center of gravity is correlated with the mass m of the vehicle.

In 5 By way of example, an empirically determined relationship between the center of gravity height h _sp and the mass m of the vehicle is shown for different loading variants.

As can be seen, the center of gravity h _sp tends to increase as the mass m of the vehicle increases. The relationship between the center of gravity height h _sp and the product mh obeys approximately the same shape as mhα2 · h 2 / sp.

In the following, equations are to be derived with which both the mass m of the vehicle and the distance h between the center of gravity and the roll axis of the vehicle can be estimated independently of each other. For this purpose, it is necessary to disassemble the spring force F _ij in their components. As in 4 already indicated, the spring force F _{ij is} composed of a dynamic component F _{dyn, ij} and a stationary component F _{stat, ij} , F ij = F stat, ij + F dyn, ij , (2.7)

≈ 0) auftretende Federkraft wieder. Aus ihr können Informationen über die Masse m des Fahrzeugs, m = Fstat,vl + Fstat,vr + Fstat,hl + Fstat,hr + muf, (2.8)und das stationäre Drehmoment M₀ um die Wankachse,

gewonnen werden, wobei m_uf die ungefederte Masse des Fahrzeugs darstellt. Letztere setzt sich aus der bekannten Masse der Fahrzeugräder sowie Teilen der Radaufhängung zusammen.The stationary component F _{stat, ij} indicates that during a substantially unaccelerated ride (a _y ,

≈ 0) occurring spring force again. From it information about the mass m of the vehicle, m = F stat, vl + F stat, vr + F stat, hl + F stat, hr + m uf , (2.8) and the stationary torque M ₀ about the roll axis,

are obtained, where m _uf is the unsprung mass of the vehicle. The latter is composed of the known mass of the vehicle wheels and parts of the suspension.

an. Gleichung (2.10) stellt eine Alternative zu Gleichung (2.6) dar und erlaubt gleichfalls eine Schätzung des Produkts mh. Ausgehend von Gleichung (2.8) ist ferner eine unmittelbare Schätzung der Masse m des Fahrzeugs möglich.With the equation (2.9) valid for the quantity M ₀ , equation (2.6) takes the form

at. Equation (2.10) represents an alternative to equation (2.6) and also allows an estimate of the product mh. Based on equation (2.8), an immediate estimate of the mass m of the vehicle is also possible.

wobei F N / dyn,ij die sich für den Fall einer Masse m^N des Fahrzeugs am Fahrzeugrad 14_ij ergebende dynamische Federkraft bezeichnet.In order to obtain an expression for determining the distance h, the above-described properties of the air spring must be used. In a certain Federwegbereich - namely, where the Zuganschlagfeder and the buffer provide no contributions - the spring stiffness c _ij the air spring is proportional to the force supported by the air spring leg force F _ij . Assuming that the spring forces F _ij on all four vehicle wheels change in the same way with an increase or decrease in the mass m of the vehicle, a relationship of the shape applies in said spring travel range

where FN / dyn, ij which in the case of a mass m ^{N of} the vehicle on the vehicle 14 _ij resulting dynamic spring force referred.

In the case of the suspension travel range valid for equation (2.12), the spring stiffness c _ij can be regarded as constant. The spring force F _ij can then be calculated on the basis of a computationally simple multiplication of the spring travel s _ij with the spring stiffness c _ij , F ij = c ij (s stat, ij + s dyn, ij (2.13) wherein the spring travel s _ij from a stationary component s _{stat, ij} and a dynamic component s _{dyn, ij} composed. The stationary component s _{stat, ij} corresponds to the spring travel s _ij , as it occurs in the case of a substantially unaccelerated ride (a _y , ψ. ≈ 0), whereas the dynamic component s _{dyn, ij} under the lateral acceleration influence (a _y , ψ ≠ 0) indicating the adjusting spring travel s _ij . Equation (2.13) can be used to rewrite equation (2.12) in

Assuming for the sake of simplification that c _vr = c _vl = c _v and furthermore c _vl = c _hl = c _h , it follows from equation (2.14)

Equation (2.15) makes it possible to determine the distance h directly by detecting the two spring- _path differences (s _{dyn, vr -s dyn, vl} ) and (s _{dyn, hr -s dyn, hl} ).

Out equations (2.6), (2.8), (2.10) and (2.12) or (2.15) can be solved the distance h between the center of gravity and roll axis of the vehicle body, derive the mass m of the vehicle and the product mh. The calculated Sizes are but of course with errors afflicted. On the one hand, the equations do not give all conceivable Effects again, on the other hand, those for calculating the equations used measuring signals not free of interference.

Around possible To minimize errors, it is therefore beneficial if the evaluation the equations exclusively in such driving conditions takes place, in which the non-modeled effects largely without Stay in influence.

by virtue of of simplifications in the derivation of the equations (2.6), (2.8), (2.10) and (2.12) or (2.15) these formulas not in all driving conditions.

In the formulation of equation (2.10), the counter-torque generated by the dynamic spring forces F _{dyn, ij} is set equal to the moment caused by the lateral acceleration a _ij . Equation (2.10) only applies exactly if this moment leads exclusively to the build-up of spring forces. In non-stationary states but now damper forces are built up in addition to the spring forces. At the same time, the vehicle body undergoes a rolling acceleration caused by the rolling motion. How precise Equation (2.10) is satisfied can be estimated by comparing the dynamic spring forces F _{dyn, ij} with the damper force and the force leading to roll acceleration.

In the sense of equation (1.3), equation (2.10) can be considered sufficient enough if the two forces individually are not greater than 10% of the dynamic spring force F _{dyn, ij} .

Under Using the equations (2.6), (2.8), (2.10) and (2.12) or (2.15), the quantities m, h and mh each calculate now in different ways.

und zum anderen von Gleichung (2.10),

The product mh can be calculated in two ways. First, by using equation (2.6),

and secondly equation (2.10),

Equation (2.10) enables an estimate of the center of gravity even if there is only a single value pair for a _y and (F _{dyn, vr} - F _{dyn, vl} + F _{dyn, hr} - F _{dyn, hl} ). Thus equation (2.10) defines a straight line passing through the origin of coordinates, the slope of which gives directly the product mh. In order to be able to evaluate equation (2.10), however, the dynamic spring forces F _{dyn, ij must be} known. A determination of the product mh on the basis of equation (2.10) can therefore not be made directly at the beginning of the journey consequences. Here instead equation (2.6) is used.

The stationary spring paths s _{stat, ij,} from which in turn the stationary spring forces F _{stat, ij are} calculated, can in turn be determined in two different ways.

On the one hand, the stationary spring travel s _{stat, ij can be determined} directly from the spring travel s _ij occurring during unaccelerated travel (a _y , ψ, ≈ 0). On the other hand, there is a possibility that the breakaway torque of the air spring strut to be overcome for rebounding and rebounding 20 _years This leads to the fact that an exact determination of the stationary spring travel s _{stat, ij is} not possible directly. The influence of the breakaway torque can be reduced by the vehicle being excited to roll during driving and the resulting spring travel s _ij and the associated lateral accelerations a _{y being} determined. The pairs of values obtained in this way are approximated by means of a straight line equation, the value of the straight line equation for a _y = 0 then representing the desired stationary spring travel s _{stat, ij} . The accuracy of this method depends on the selected lateral acceleration range in which the approximation is made.

Thus, there are two possibilities for determining the static spring travel s _{stat, ij} - on the one hand by direct detection of the spring paths s _ij resulting from an unaccelerated vehicle (a _y , ψ. ≈ 0) and on the other hand by approximating the transverse acceleration influence (a _y , ψ. ≠ 0) spring travel s _ij occurring during the course of the journey.

Overall, the quantities m and h are respectively calculated in two different ways - according to the two possible approaches in determining the stationary spring travel s _{stat, ij} - using equations (2.8) and (2.12). In addition, the product mh is calculated in three different ways - on the one hand starting from equation (2.6) and on the other hand starting from equation (2.10) - also taking into account the two possible approaches in determining the stationary spring travel s _{stat, ij} .

wobei N_v bzw. N_h eine an der Vorder- bzw. Hinterachse des Fahrzeugs wirkende Normalkraft, g die Gravitationsbeschleunigung, l_x den Radstand in Fahrzeuglängsrichtung, x den horizontalen Abstand zwischen Schwerpunkt und Nickachse des Fahrzeugs, h_sp die Schwerpunkthöhe und a_x die zum Auftreten der Nickbewegung führende Längsbeschleunigung des Fahrzeugs bezeichnet.Additionally or alternatively, an estimate of the center of gravity height is carried out by evaluating a torque balance that applies in relation to a pitching motion of the vehicle body

where N _v or N _{h is} a force acting on the front and rear axle of the vehicle normal force, g the gravitational acceleration, l _x the wheelbase in the vehicle longitudinal direction, x the horizontal distance between the center of gravity and pitch axis of the vehicle, h _sp the center of gravity height and a _x denotes the occurrence of pitching leading longitudinal acceleration of the vehicle.

The fact represented by equation (3.1) is in 6 illustrated.

The longitudinal acceleration a _x is in this case from the measurement signals of a longitudinal acceleration sensor 22 which is also part of the Electronic Stability Program.

wobei ΔN_N die Differenz der Normalkräfte zwischen der Vorderachse und der Hinterachse des Fahrzeugs wiedergibt. Durch Einführung eines für die Vorderachse des Fahrzeugs geltenden Zusammenhangs der Gestalt (F_vr = F_vl = F_v) Nv = Fv + kvm·ax·tan(εv), (3.3)bzw. eines für die Hinterachse des Fahrzeugs geltenden Zusammenhangs der Gestalt (F_hr = F_hl = F_h) Nh = Fh + khm·ax·tan(εh), (3.4)lässt sich in Gleichung (3.1) die zum Auftreten der Nickbewegung des Fahrzeugaufbaus führende Anfahr- bzw. Abbremsdynamik des Fahrzeugs berücksichtigen,

wobei k_v die Antriebs- bzw. Bremsmomentenverteilung an der Vorderachse, k_h die Antriebs- bzw. Bremsmomentenverteilung an der Hinterachse, tan(ε_v) den Anfahr- bzw. Bremsstützwinkel an der Vorderachse und tan(ε_h) den Anfahr- bzw. Bremsstützwinkel an der Hinterachse des Fahrzeugs bezeichnet. m^* stellt hierbei eine fiktive, von der jeweiligen Schwerpunkthöhe des Fahrzeugs abhängige Masse dar.Equation (3.1) allows an estimate of the center of gravity height in such driving conditions in which the vehicle body is caused to pitch due to the influence of longitudinal acceleration caused by driving. These include in particular start-up or braking operations. By transformation of equation (3.1) results

where ΔN _{N represents} the difference in normal forces between the front axle and the rear axle of the vehicle. By introducing a relation of shape to the front axle of the vehicle (F _vr = F _vl = F _v ) N v = F v + k v m · a x · Tan (ε v (3.3) or a relation of the shape applicable to the rear axle of the vehicle (F _hr = F _hl = F _h ) N H = F H + k H m · a x · Tan (ε H ), (3.4) can be considered in equation (3.1) leading to the occurrence of the pitching motion of the vehicle body starting or Abbremsdynamik the vehicle,

where k _{v is} the drive or braking torque distribution at the front axle, k _h the drive or braking torque distribution at the rear axle, tan (ε _v ) the starting or braking support angle at the front axle and tan (ε _h ) the starting or Brake support angle at the rear axle of the vehicle called. In this case, m ^* represents a fictitious mass which depends on the respective center of gravity height of the vehicle.

7 shows by way of example the relationship between the spring force difference .DELTA.F and the longitudinal acceleration a _{x of} the vehicle for different loads of the vehicle. Here, the dotted line represents an unloaded vehicle, the solid line represents the presence of a load in the luggage compartment of the vehicle and the dotted line represents the presence of a charge in both the luggage compartment and on the roof of the vehicle.

In the 7 shown straight line is in the arithmetic and control device 11 stored the electronic stability program, the selection of the applicable straight line on the basis of the determined spring deflection .DELTA.F and the associated longitudinal acceleration a _{x of} the vehicle takes place. From the slope of the selected straight line, the fictitious mass m ^* then results directly from equation (3.5).

As can be seen, the straight lines at a _x = 0 have a kink which has its origin in that the variables k _v , k _h , tan (ε _v ) and tan (ε _h ) have different values in the case of a starting operation than in the case of a deceleration process.

In order to secure the center of gravity estimated on the basis of the fictitious mass m ^* , the spring deflection _{ΔF ax≈0} occurring between the front and rear axles of the vehicle during unaccelerated driving (a _x ≈ 0) is additionally evaluated. If the spring path _difference ΔF _{ax≈0 has} a high amount, then it is possible to conclude that the vehicle has a corresponding load (for example in the luggage compartment), that is to say an increased center of gravity.

The actual estimation of the center of gravity height is made by the fuzzy probabilities w (m), w (h), w (mh) and w (m ^* ) corresponding to m, h, mh and m ^* for the presence of a low center of gravity be assigned. The fuzzy probabilities w (m), w (h), w (mh) and w (m ^* ) thus obtained are then multiplicatively linked to a total probability w _ges .

As a result, a particularly reliable statement regarding the current center of gravity height of the vehicle is possible. If the total probability w _{ges is} greater than a predefined threshold value, it is concluded that the vehicle currently has a low center of gravity.

These Information is then in particular for the appropriate adaptation of triggering threshold of the Electronic Stability Program.

Claims (5)

Device for estimating the center of gravity in a vehicle, having a computing device ( 11 ), which in dependence of determined operating state variables (a _y , ψ., a _x , p _ij , s _ij ), which represent a driving condition occurring operating condition of the vehicle, a plurality of the center of gravity of the vehicle representing center of gravity position sizes (m, h, mh, m ^* ) calculated, the computing device ( 11 ) in a first step each of the calculated center of gravity position sizes (m, h, mh, m ^* ) depending on their magnitude a single probability (w (m), w (h), w (mh), w (m ^* )) for the presence assigns to a certain center of gravity and / or the center of gravity and in a second step the determined individual probabilities (w (m), w (h), w (mh), w (m ^* )) are linked to a total probability (w _ges ) for the presence of a particular center of gravity height and / or center of gravity class. Apparatus according to claim 1, characterized in that the computing device ( 11 ) the center of gravity positions (m, h, mh, m ^* ) calculated for different driving conditions of the vehicle. Apparatus according to claim 2, characterized in that the computing device ( 11 ) calculates a first set of CG positions (m, h, mh, m ^* ) in driving conditions in which the vehicle has substantially unaccelerated travel, and calculates a second set of CG positions (m, h, mh, m ^* ) in driving conditions in which the vehicle is characterized by an accelerated ride. Apparatus according to claim 1, characterized in that the computing device ( 11 ) evaluates a pitching movement occurring under longitudinal acceleration influence (a _x ) and / or a rolling motion of the vehicle occurring under lateral acceleration influence (a _y , ψ) in order to estimate the current center of gravity. Method for estimating the center of gravity in a vehicle, in which, as a function of determined operating state variables (a _y , ψ., A _x , p _ij , s _ij ), which represent a driving condition of the vehicle as a result of the journey, a plurality of center of gravity position values representing the center of gravity of the vehicle (m are computed h, mh, m ^*), wherein in a first step, each of the calculated center of gravity quantities (m, h, mh, m ^*) in dependence on its amount a single probability (w (m), w (h) w (mh ), w (m ^* )) is assigned for the presence of a certain center of gravity height and / or center of gravity class and in a second step the determined individual probabilities (w (m), w (h), w (mh), w (m ^* )) linked to a total probability (w _ges ) for the existence of a given center of gravity and / or category of center of gravity.