DE4216301A1 - Method for determining the behavior of characterizing variables - Google Patents

Description

The invention relates to a method for determining the driving behaving characterizing quantities according to the preamble of Claim 1.

It is already known a generic method, according to which for determining the yaw angular velocity of the Sagnac effect is applied. This is monochromatic, coherent light divided and in the opposite direction by means of fiber optic cables guided on a circular path. Due to a rotation (yawing supply) of the optical fiber cable thus results for the split Light a rotating frame of reference. Because in this rotie reference frame corresponding to the electromagnetic waves behave differently in relativistic transformation equations As in a dormant frame of reference, so too do the Interference phenomena of divided light depending on from spin (yaw angle acceleration) and Rotational speed (yaw rate). By Auswer tion of these interference phenomena can thus be attributed to the ent closing down the quantities of the rotary motion.

In this process it might be considered disadvantageous that initially be a light source with interference-capable light be must be provided. In addition, the arrangement of the light be supported in terms of vibrations so that the interference can occur.  

Furthermore, a linear Einspurmodell a vehicle known, where the height of the center of gravity of the vehicle is neglected. Thus, in this approximation, the hard point of the vehicle in the plane of the contact points of the wheels laid. Since rolling and pitching movements are excluded, In this model, the wheels of an axle can become a wheel in the center of the axis are united. This model is included For example, in German book: Zomotor, Adam: chassis technology, driving behavior, ed. Jörnsen Reimpell, Würzburg: Vogel 1987, ISBN 3-8023-0774-7 is described on pages 99 to 116.

This representation is not apparent, as the greed angular velocity and yaw angular acceleration measurable quantities can be derived.

The object of the invention is to provide a method for determining the To design driving behavior of characterizing variables in such a way that the best possible accuracy at a possible ge can be achieved effort on required hardware.

This object is achieved in a generic method for Be mood the driving behavior characterizing sizes according to the invention with the characterizing features of the claim 1, wherein the features of the dependent claims characterize some education and training.

First, some equations are to be derived by means of which are the quantities to be determined depending on measurable Sizes are displayed. This is initially a table he which are the meaning of those used below Symbols clarified.

symbol meaning d / dt first time derivative of a quantity that is one of the sizes included in this table d² / dt second time derivative one size, which is one of the sizes included in this table a Vehicle longitudinal acceleration a _q Vehicle lateral acceleration a _qh Vehicle lateral acceleration behind a _qv Vehicle lateral acceleration in front c _h Cornering Stiffness behind c _v Cornering Stiffness in front cs _h Rear spring stiffness cs _v Cross spring stiffness in front c _x Torsional stiffness during roll movement around vehicle longitudinal axis _h Installation height of the lateral acceleration sensor at the rear h _p Roll pole height (distance of the point during a rolling movement from the ground, which is stationary) h _s Gravity height h _v Installation height of the lateral acceleration sensor in front J _x Moment of inertia around the vehicle's longitudinal axis J _z Moment of inertia around the vehicle's vertical axis k _x Rotary damping during roll motion around vehicle longitudinal axis l wheelbase l _h Distance between lateral acceleration sensor rear and front axle l _v Distance between front lateral acceleration sensor and front axle l _s Distance between center of gravity and front axle m vehicle mass S _h Side force on the rear wheels S _v Lateral force on the front wheels   v Vehicle longitudinal speed v _q Vehicle longitudinal speed α _h Slip angle on the rear axle a _v Slip angle on the front axle β float angle δ wheel steering angle .delta.t Integration step manner Φ yaw t roll angle

The balance of forces in the transverse direction of the vehicle provides the Equation:

m _* a _q = S _{v *} cos (δ) + S _h (1)

The torque balance around the vehicle's vertical axis provides the relationship:

J _{z *} d 2 Φ / dt 2 = l _{s *} S _{v *} cos (δ) - (ll _s ) _* S _h (2)

In addition, the dynamics of a rolling motion are modeled by the Approach of a differential equation 2nd order:

J _{x *} d 2 τ / dt 2 + k _{x *} dτ / dt + c _{x *} τ = m _* (h _s -h _p ) _* a _q (3)

A modeling of the transverse force build-up on the tires is done after following equations:

α _v = v _* sin (δ) - l _{s *} dΦ / dt - v _q - (h _s -h _p ) _* dτ / dt (6)

α _h = (ll _s ) _* dΦ / dt -v _q - (h _s -h _p ) _* dτ / dt (7)

These equations describing the lateral force structure have one strong dependence on the vehicle longitudinal speed v on.

The accelerations a _q and a depend on the temporal change of the amount of the respective speed as well as on the temporal change of the direction of the respective speed. The following equations result:

a _q = dv _q / dt + v _* dΦ / dt (8)

a = dv / dt -v _{q *} dΦ / dt (9)

As measured variables, the steering angle δ, the vehicle longitudinal speed v, and two transverse accelerations a _qv and a _qh should now be used. The two lateral acceleration sensors can be described in each case by the distance to the front axle and the jewei time level. Due to the geometry results for these two acceleration sensors:

a _qv = a _q + (l _s -l _v ) _* d 2 Φ / dt 2 + (h _s -h _v ) _* d 2 τ / dt 2 (10)

a _qh = a _q + (l _s -l _v ) _* d 2 Φ / dt 2 + (h _s -h _h ) _* d 2 τ / dt 2 (11)

Since equations (10) and (11) are thus a system of two equations which are linearly independent in that l _{h is} not equal to l _v , d ² τ / dt ² can thus be obtained given known or negligible acceleration of the roll the yaw angle acceleration d ² Φ / dt ² and the vehicle lateral acceleration be true. Combining the two equations (10) and (11) yields:

Advantageously, when mounting the Querbeschleu nigungssensoren be provided that h _v ≡h _h ≡h _p applies. Then the Wankbeschleunigungsterme account regardless of the size order of the roll acceleration, which greatly simplifies the evaluation.

Alternatively, the rolling dynamics by a known per se numerical evaluation of the differential equation ( 3 ) example, by means of the Runge-Kutta method or by means of the expli ziten Eulersfahren with the integration step size δt suc conditions:

τ _new : = τ + dτ / dt _* δt; dτ / dt _new : = dτ / dt = d 2 τ / dt 2 _* Δt 15)

The yaw angle and lateral acceleration as well as the roll sizes Thus, using Equations (12), (13), (14) and (15) or by state estimates by means of equations (3), (10) and (11).

From the force balance according to equation (1) and the moment balance according to equation (2), the lateral forces can be obtained:

By differentiation of the two equations (16) and (17) results thus:

From the equations (4), (5), (6) and (7), two linear equations thus result, by means of which the quantities v _q and dΦ / dt can be determined from known quantities.

The equations (16), (17), (18) and (19) contain only variables which are measured directly (δ, v, a _qh, a _qv) or may be determined as described above on the basis of measured quantities. Time derivatives of known sizes can be derived by quotient education. Thus, the quantities v _q and dΦ / dt can be calculated at any time. The slip angle β is finally obtained:

β = arctane (v _q / v) (22)

So far it has been described, as from known parameters, that the Vehicle concern, the driving behavior characterizing sizes be determined. These parameters are subject to certain Fluctuations. The vehicle mass and the center of gravity vari It is characterized by different loadings. The tire dep gigen sizes vary with the tire temperature and with different road surfaces. The most significant fluctuation occurs at Cornering Stiffness. The following is a procedure presented with an adaptation of Cornering Stiffness is possible. Likewise, then an adaptation of the other parameters respectively. First of all, system equations have to be used for this adaptation are found, the only known or derivable sizes enthal and the linear are independent of the equations that are at used to determine the known or derived quantities  were. Suitable equations are obtained for example by the Differentiation of equations (20) and (21).

c _v ≡ c _v (t) = (S _{v *} cos (δ) _* dv / dt + v _* cos (δ) _* dS _v / dt + v _* S _{v *} sin (δ) _* dδ / dt) _* f _v (t) (23)

c _h ≡c _h (t) = (S _{h *} dv / dt + v _* dS _h / dt) _* f _h (t) (25)

The yaw rate is given by equations (20) and (21) by eliminating v _q . The lateral forces are calculated by means of equations (16) (17), (18) and (19) as well as corresponding difference quotients. This results in current estimates for Cornering Stiffness in front and behind. An updating of the values of Cornering Stiffness used in the further calculations can be carried out by means of a L ₂ approximation with sliding time averaging. The parameters to be used in the following calculations are denoted c _{v, akt} and c _{h, akt} . The previous parameters are denoted by c _v and c _h . The current estimates are called C _v (t) and C _h (t).

c _{v, act} = (l-Γ) _* c _v + Γ _* C _v (t) (27)

c _{h, act} = (l-Γ) _* c _h + Γ _* C _h (t) (28)

Here, Γ is a factor with a value between 0 and 1. The larger Γ, the more the current estimates are taken into account. With a small value of Γ a slow adaptation takes place. If the adaptation is to take place, for example, with a limiting frequency Ω _G , then Γ = Ω _{G *} δt.

An embodiment of the invention is shown schematically in the drawing and will be described in more detail below. Figures 1 and 2 are to be taken from representations showing the sizes of the above table on a vehicle. Fig. 3 shows a possible sequence of the method according to the invention. In a first step 301 , the values are determined on the basis of which the variables characterizing the driving behavior are determined. These values are the steering angle δ, the vehicle longitudinal speed v and the two transverse accelerations a _qv and a _qh . The steering angle is preferably measured directly, the vehicle longitudinal speed can be determined for example from the signals of speed sensors. The two transverse accelerations are preferably measured directly by means of suitably mounted lateral acceleration sensors. Optionally, it is also possible to measure the yaw rate immediately. However, this is not mandatory erforder Lich, since the yaw rate can also be determined from the above measured variables, for example by means of the indicated method. In a second step 302 , the lateral acceleration a _q and the yaw angular acceleration d ² Φ / dt ^{2 are} determined from these quantities, for example by means of equations (12) and (13). For example, by means of equations (14) and (15), the roll angle τ is then determined with its time derivatives in a step 303 . Difference quotients then form the higher derivatives of the state variables, which are still needed in the following. By means of the equations (16), (17), (18) and (19), the lateral forces and their derivatives are then obtained in a step 304 . By means of the equations (20), (21) and (22), in a step 305 the slip angle and the yaw angular velocity are then obtained, if this quantity has not already been measured directly.

In addition, it can be seen from FIG. 4 that an adaptation of the parameters can take place. For this purpose, higher derivatives of the lateral forces are first determined in a step 401 by means of difference quotients. Equations (23), (24), (25) and (26) are then used to determine current estimated values of the parameters in a step 402 . By means of equations (27) and (28), in a step 403, values of the parameters are then determined which are then used in subsequent calculations for determining the variables that characterize the driving behavior.

Alternatively, it is also possible if the yaw angle Speed is measured from deviations of the measured Yaw angular velocity from the derived yaw angle speed to adapt the parameters.

FIG. 5 shows a computing device 501 to which the aforementioned variables are supplied as input signals 502 , 503 , 504 , 505 and possibly 506 in accordance with step 301 of FIG. 3. After the corresponding quantities have been determined in the computing device by means of the equations given in the flowchart of FIG. 3, output signals 506 , 507 , 508 are output which represent the determined quantities. These particular sizes may be the slip angle, the Gierwin kelgeschwindigkeit and / or another size that was determined during the course of the process. Furthermore, according to the flowchart of FIG. 4, an adaptation of the parameters by means of which the vehicle model is described.

Claims (8)

1. A method for determining the behavior of characterizing variables, characterized

• - That a computing device ( 501 ) signals ( 502 , 503 , 504 , 505 ) are fed ( 301, 502, 503, 504, 505 ), the steering angle (δ), the vehicle longitudinal speed (v) and two in the vehicle longitudinal direction one behind the other (l _v , l _h ) represent lateral accelerations (a _qv , a _qh ),
• - That due to these measured quantities in the computing device ( 501 ) using vehicle-specific variables and a vehicle model further sizes are derived ( 302, 303, 304 ) and
• - That then further by means of the vehicle model in the computing device ( 501 ) at least one of the parameters slip angle and / or yaw rate is determined and output ( 305, 506, 507, 508 ).

2. The method according to claim 1, characterized in that in the vehicle model rolling movements of the vehicle are taken into account ( 303 ). 3. The method according to claim 1, characterized in that the transverse accelerations (a _qv , a _qh ) are measured by means of Querbeschleuni tion sensors whose respective installation heights (h _h , h _v ) are equal and the center of gravity height (h _s ) correspond. 4. The method according to any one of claims 1 to 3, characterized in that an adaptation of the vehicle-specific variables takes place ( 401, 402, 403 ). 5. The method according to claim 4, characterized in that the adaptation by means of a moving average method takes place ( 403 ). 6. The method according to any one of claims 1 to 5, characterized in that at least one further variable is output ( 506, 507, 508 ), which was determined during the course of the method. 7. The method according to any one of claims 1 to 6, characterized in that the computing means ( 501 ) is supplied with a signal ( 506 ) representing the yaw rate. 8. The method according to claim 7 and 4 or 5, characterized in that the adaptation of the parameters due to the computing device ( 501 ) supplied yaw angular velocity.