DE10325485A1 - Determining vehicle float angle involves modeling lateral force component on tire, linearizing relative to skew angle, determining relationship between skew, float angles, using kinetic relationship - Google Patents

Abstract

The method involves determining the lateral force component (Fy) on a tire in the y-direction (y) based on a model, linearizing the component relative to a skew angle (alpha) of the tire, determining an offset value and a value proportional to the skew angle value, determining the relationship between the skew angle of the tire and the float angle and using a model to determine the float angle (beta) according to a kinetic relationship.

Description

The invention relates to a method to determine the float angle when regulating / controlling Driving dynamics variables one Vehicle.

Today's vehicle dynamics control systems work without floating angle control because there is no procedure the float angle reliably and to estimate robustly.

There are currently two different approaches for estimating the float angle: A known method ( WO 01/81139 A1 ) uses a β observer with a kinetic vehicle model:

und

direkt abgeschätzt. Durch Integration der abgeschätzten Bewegungsgrößen

und

werden die Zustandsgrößen ν_y und

berechnet. Mit der abgeschätzten Quergeschwindigkeit ν_y wird der Schwimmwinkel nach

berechnet.So that the movement quantities

and

directly estimated. By integrating the estimated movement quantities

and

the state variables ν _y and

calculated. With the estimated transverse speed ν _y the float angle decreases

calculated.

Another known method ( DE 195 15 054 A1 ). uses a β observer with the kinematic relationship

abgeschätzt. Durch Integration von der abgeschätzten Schwimmwinkelgeschwindigkeit

wird der Schwimmwinkel berechnet.This is the first step at the velocity of the slip angle

estimated. By integrating the estimated slip angle speed

the float angle is calculated.

In the known methods the model errors and measurement errors are continuously summed up by the integration. This makes the estimated Floating angle very imprecise. About that In addition, the road bank slope must be known, which is difficult is to be determined.

The invention is based on the object to specify a method by which the estimated float angle is determined can be improved. The float angle should be estimated more precisely.

nach einer kinetischen Beziehung.According to the invention, this object is achieved in that a generic method is carried out with the following steps:
Model-based determination of a tire lateral force component F _{y, i} in the y direction, linearization of the tire lateral force component F _{v, i} relative to the slip angle of the tire α _i ,
Determining an offset value F _offset, i (α / i) and a value proportional to the slip angle α _i ,
Determining the relationship between the slip angle of the tire α _i and the slip angle, and
Model-based determination of the float angle

after a kinetic relationship.

ermittelt wird. Die Linearisierung der Reifenkraft gegenüber dem Reifenschräglaufwinkel α_i erfolgt lokal mit den Beziehungen

Vorteilhaft ist, dass der Offset-Wert F_Offset,i (α / i) und der dem Schräglaufwinkel α_i proportionale Wert nach der Beziehung

ermittelt wird, wobei der Offset-Wert F_Offset,i (α / i) aus dem Term (F_y,i(α / i)–F / y,i(α / i)·α / i) und der dem Schräglaufwinkel α_i proportionale Wert aus dem Term F / y,i(α / i)·α / i bestimmt werden.It is advantageous that the tire force component F _{y, i} compared to the slip angle of the tire α _i according to the relationship

is determined. The linearization of the tire force with respect to the tire slip angle α _i takes place locally with the relationships

It is advantageous that the offset value F _{offset, i} (α / i) and the value proportional to the slip angle α _i according to the relationship

is determined, the offset value F _{offset, i} (α / i) from the term (F _{y, i} (α / i) −F / y, i (α / i) · α / i) and that of the slip angle α _i proportional value can be determined from the term F / y, i (α / i) · α / i.

wobei der Schwimmwinkel β als Funktion des proportionalen Werts nach der Beziehung

ermittelt wird.The relationship between the slip angle α _i and the float angle takes place via the relationships

where the float angle β is a function of the proportional value according to the relationship

is determined.

The method is advantageous provided that when determining the slip angle the roll angle and / or the road bank inclination is taken into account in a model become.

kann man Fahrdynamikregelungen, wie sie beispielsweise in DE 195 15 061 A1 , DE 195 15 056 A1 und DE 195 15 059 A1 beschrieben sind und deren Inhalt Bestandteil der vorliegenden Anmeldung ist, ganz neu gestalten:

• 1) Das Untersteuer- und Übersteuerverhalten des Fahrzeugs kann in Abhängigkeit von den Reifenschräglaufwinkeln und lokalen Reifensteifigkeiten geregelt werden;
• 2) Der Reibwert kann nach den Reifenschräglaufwinkeln und lokalen Reifensteifigkeiten frühzeitig und kontinuierlich angeschätzt werden;
• 3) Die kritische Fahrsituation "langsame Eindrehung" des Fahrzeugs um die Hochachse kann frühzeitig erkannt und durch die Fahrdynamikregelung verhindert werden;
• 4) Eine Schräglaufwinkelregelung kann vorgesehen werden.

The method according to the invention provides that the tire force in the Y direction is locally compared to the tire slip angle according to Eq. (7) (8) and (9) to be linearized and divided into two terms: one term describes an offset and the other term a proportion proportional to the tire slip angle. If you insert the four tire forces into the equation of motion (1), the float angle can be calculated directly. This means that no integration of estimated or measured size is necessary. The method is independent of what is used for a tire model or vehicle model. With the estimated float angle

you can control vehicle dynamics, such as in DE 195 15 061 A1 . DE 195 15 056 A1 and DE 195 15 059 A1 are described and their content is part of the present application, completely redesign:

• 1) The understeer and oversteer behavior of the vehicle can be regulated depending on the tire slip angle and local tire stiffness;
• 2) The coefficient of friction can be estimated early and continuously according to the tire slip angle and local tire stiffness;
• 3) The critical driving situation "slow turning" of the vehicle about the vertical axis can be recognized at an early stage and prevented by the driving dynamics control;
• 4) A slip angle control can be provided.

• a) Der Schwimmwinkel wird direkt nach der kinetischer Beziehung Gl. (1) abgeschätzt, ohne Integration von einer anderen abgeschätzten Größe. Damit werden die Modellfehler und Messfehler minimiert.
• b) Das Verfahren nach Gl. (21) ist unabhängig von den Fahrbahnneigungen.
• c) Das Verfahren nach Gl. (21) ist unabhängig vom Fahrzeugmodell und Reifenmodell. Man braucht lediglich die Reifenkraft in der y-Richtung in einem kleinen lokalen Bereich nach Reifenschräglaufwinkel nach Gl. (8) zu Linearisieren. Je nach Bedarf der Genauigkeit des abgeschätzten Schwimmwinkels können verschiedene Reifen- und Fahrzeugmodell benutzt werden. Danach lässt sich das Verfahren in verschiedenen Formen ausdrücken wie z. B. nach Gl. (21), (23), (27) bis (30).
• d) Das Verfahren kann bei Verwendung des linearen Reifenmodells stark vereinfacht werden (Gl. (27)). Durch Kombination mit der kinematischen Beziehung nach Gl. (31) kann der Schwimmwinkel für alle Fahrsituationen einfach abgeschätzt werden.
• e) Das Verfahren kann die Messgrößen vom jetzigen ESP-System direkt benutzen und braucht keine weiteren Messsensoren.
• f) Das Verfahren ist einfach, robust und zuverlässig. Es ist leicht realisierbar in jetzigen ESP-System.

The special advantages of the new process compared to the known processes are:

• a) The float angle is determined directly according to the kinetic relationship Eq. (1) estimated without integration of another estimated size. This minimizes the model errors and measurement errors.
• b) The method according to Eq. (21) is independent of the road gradient.
• c) The method according to Eq. (21) is independent of the vehicle model and tire model. You only need the tire force in the y-direction in a small local area according to the tire slip angle according to Eq. (8) to linearize. Depending on the need for the accuracy of the estimated float angle, different tire and vehicle models can be used. Then the process can be expressed in various forms such as. B. according to Eq. (21), (23), (27) to (30).
• d) The procedure can be greatly simplified when using the linear tire model (Eq. (27)). By combining it with the kinematic relationship according to Eq. (31) the float angle for all driving situations can be easily estimated.
• e) The method can use the measurement parameters from the current ESP system directly and does not require any further measurement sensors.
• f) The process is simple, robust and reliable. It is easy to implement in the current ESP system.

An embodiment is in the drawing specified and is described in more detail below.

Show it

1 a schematic representation of the driving dynamics

2 is a schematic representation of the dependence of the gravity component F _{y, G} on the road incline

3 is a schematic representation of the individual tire force components

4 a schematic representation of the relationship between the tire force component and the tire slip angle

5 a schematic representation of the rolling movement of a vehicle

6 a schematic representation of a single track model

7 a representation of a simplified tire model.

In connection with the 1 to 7 describes a new method for a robust estimation of the swimming angle without additional sensors.

für die Y-Richtung darstellen. Dabei ist α_y die Querbeschleunigung des Fahrzeugs im Schwerpunkt, m die Fahrzeugmasse und F_y die resultierende Kraftkomponente in der y-Richtung (1). Bei Vernachlässigung der Windkraft besteht F_y aus den vier Reifenkräften ∑F_y,i (i = 1, 2, 3, 4) in der Y-Richtung und dem Schwerkraftanteil F_y,G in der Y-Richtung,

The method is based on the kinetic relationship of vehicle dynamics:
The equation of motion of the vehicle can be based on the relationship in the vehicle-fixed coordinate system

represent for the Y direction. Here α _{y is} the lateral acceleration of the vehicle in the center of gravity, m the vehicle mass and F _y the resulting force component in the y direction ( 1 ). If wind power is neglected, F _y consists of the four tire forces ∑F _{y, i} (i = 1, 2, 3, 4) in the Y direction and the gravity component F _{y, G} in the Y direction,

The proportion of gravity F _{y, G} in the Y direction depends on the road gradient ( 2 ). There is the following relationship between F _{y, G} and the road bank angle α _Q

The individual tire force components F _{y, i} (i = 1, 2, 3, 4) depend on the corresponding tire lateral force F _{S, i} and the tire circumferential force F _{U, i} ( 3 ) With

Here δ _{i is} the steering angle (steering angle). The following applies to the two rear wheels:

The two tire force components F _S and F _{U of} each wheel are mainly dependent on the tire slip angle α, the wheel load F _z , the circumferential slip S _x and the coefficient of friction μ.

The tire slip angle α has the greatest influence for the tire lateral force F _S. The tire force component F _{y, i} is therefore primarily dependent on the tire slip angle α _i . The relationship between the tire force component F _{y, i} and the individual influencing factors can generally be expressed as follows:

For any tire slip angle α _i , the relationship between the tire force component F _{y, i} and the tire slip angle α _i can be linearized in a certain small range as follows:

F _{y, i} (α ') is the tire force component F _{y, i} at the tire slip angle α / i and F / y, i (α') is its partial derivative at this point. This partial derivative F / y, i (α ') is the gradient of the tire force component F _{y, i} at the tire slip angle α / i. This means that the tire force component F _{y, i} at the tire slip angle α _i can be calculated from the F _{y, i} ( Approximately calculate α ') and the gradient F / y, i (α') at any other tire slip angle α _i nearby as follows.

The first term (F _{y, i} (α / i) - F / y, i (α / i) · α / i is the intersection of the linearized tire line at α / i with the F _{y, i} (α) axis and corresponds to the offset F _{offset, i} (α / i). The second term describes the proportion proportional to the tire slip angle α _i . This means that the tire force component in the y direction of each wheel consists of an offset F _{offset, i} (α / i) and a proportion proportional to the tire slip angle α _i (F / y, i (α / i) · α / i), the gradient F / y, i (α ') corresponding to the local tire rigidity.

If you set the Eq. (9) into Eq. (2), the resulting tire force results in the y direction

The four tire slip angles can be calculated from the following equations (Eq.):

gegenüber ν_x ergeben sich die folgenden vereinfachten Beziehungen:

By linearization or neglect of the small part

compared to ν _x , the following simplified relationships result:

The float angle β is defined as follows:

If you put equations (12) into Eq. (10) one, then the last term of the tire forces, namely the proportion proportional to the tire slip angle α _i as a function of the slip angle β:

From Eq. (14), (10) and (1) the float angle β can be solved directly:

With Eq. (15) the float angle β can be estimated directly, if all sizes on the right side are known. This connection has general validity and is independent of what a Vehicle model or what a tire model is used.

In the known ESP system the yaw rate, the steering angle and the lateral acceleration with sensors measured.

δ_M und α_y,M bezeichnet . Die gemessene Querbeschleunigung α_y,M enthält außer der richtigen Fahrzeugbeschleunigung α_y auch weitere Anteile a_y,W und a_y,G, die durch die Aufbauwankbewegung (5, Wankwinkel φ) des Fahrzeugs und die Fahrbahnquerneigung verursacht werden. Die gemessene Querbeschleunigung α_y,M lässt sich wie folgt beschreiben:

These measurands are with

δ _M and α _{y, M} denotes. The measured lateral acceleration α _{y, M} contains, in addition the correct vehicle acceleration α _y also play a _{y, W} and A _{y, G,} by the Aufbauwankbewegung ( 5 , Roll angle φ) of the vehicle and the road inclination are caused. The measured lateral acceleration α _{y, M} can be described as follows:

The roll angle φ can be calculated using a quasi-stationary roll model estimated.

Combining the two equations gives the following relationship with the simplification φ ≈ sinφ

The quantity ν _x required in equation (15) can be replaced by the existing vehicle reference speed ν _ref , which is determined in a known manner from the wheel speeds.

For the calculations of the tire forces F _{y, i} (α / i) _i and the gradients F ' _{y, i} (α / i), first use equation (12) and the estimated float angle β from the last calculation step by the four slip angles to determine α / i.

Then you can use any tire model (e.g. HSRI tire model, Magic tire model, etc.) or tire map to directly determine the tire lateral and circumferential force for the individual wheels men. The remaining input variables for the tire model, such as wheel load F _z , circumferential slip S _x and coefficient of friction μ, are recalculated from measured variables or models for each calculation step. According to Eq. (4) and (5) the tire force components F _{y, i} (a / i) are calculated from the corresponding lateral and circumferential forces.

The gradients F / y, i (a / i) can then be calculated by numerical differentiation with:

The quantities F _{y, i} (α / i + Δα) must be calculated exactly like F _{y, i} (α / i) with the same tire model and the same other input variables.

und δ_M sowie die Referenzgeschwindigkeit ν_ref in die Gl. (15) ein, dann wird der Schwimmwinkel β wie folgt abgeschätzt:

If you put Eq. (18), Eq. (3) and the measurands

and δ _M and the reference speed ν _ref in Eq. (15), then the float angle β is estimated as follows:

If you compare the single-track vehicle model ( 6 ) is used, then the tire forces of each axle are summarized with:

With a complex tire model or tire map, Eq. (21) for the estimation of the slip angle can be simplified as follows:

If you have a simple tire model, like maps of kinked curves ( 7 ) used, then the tire forces can be calculated as follows:

Here C (F _z , μ, F _U ), C _K (F _z , μ, F _U ) and α _K depend on the axle load, the coefficient of friction and the circumferential force.

The corresponding gradients are:

With a small steering angle δ, Eq. (4) can also be simplified:

• a) Für den Fall (|α_f| <= α_K,f) und (|α_r| <= α_K,r)
  
• c) Für den Fall (|α_f| < α_K,f) und (|α_r| <= α_K,r)

If you put equations (24), (25) and (26) into Eq. (23), then the following formulas result for the estimation of the slip angle β:

• a) For the case (| α _f | <= α _{K, f} ) and (| α _r | <= α _{K, r} )
  
• c) For the case (| α _f | <α _{K, f} ) and (| α _r | <= α _{K, r} )

Another alternative is to use the following kinematic model (without the kinetic model with the simple linear tire characteristic according to Eq. (27)):

berechnet:

In the stable driving range, the float angle β according to Eq. (27) estimated. Then the derivation from the estimated float angle

calculated:

The vehicle lateral acceleration ^ _y can be estimated as follows:

If you put the estimated lateral acceleration ^ _y into Eq. (18) on, then the roadway slope ^ _{y, G is} estimated for stable journeys:

In the unstable rides that is Model error with the simple linear tire characteristic according to Eq. (27) too large. The kinematic model according to Eq. (31) used for a short time be further to the float angle β estimate.

als Anfangswert benutzt und die Fahrbahnquerneigung ^ _y,G für kurze Zeit als konstant angenommen. Für jeden Schritt wird die Fahrzeugquerbeschleunigung ^ _y wie folgt neu abgeschätzt:

Here, the long-estimated angle of attack

used as the initial value and the road inclination ^ _{y, G is} assumed to be constant for a short time. For each step, the vehicle lateral acceleration ^ _y is re-estimated as follows:

After that, the slip angle velocity is calculated according to Eq. (31) estimated:

wird durch numerische Integration von

berechnet.The float angle

is achieved through numerical integration of

calculated.

Claims (6)

Method for determining a float angle in the regulation / control of driving dynamics variables of a vehicle with the steps model-based determination of a tire lateral force component F _{y, i} in the y direction, linearizing the tire lateral force component F _{y, i} with respect to the slip angle of the tire α _i , determining an offset Value F _{offset, i} (α / i) and a value proportional to the slip angle α _i , determining the relationship between the slip angle of the tire α _i and the float angle and model-based determination of the float angle

after a kinetic relationship. A method according to claim 1, characterized in that the tire force component F _{Y, i} compared to the slip angle of the tire α _i according to the relationship

is determined. Method according to claim 1 or 2, characterized in that the linearization of the tire slip angle α _i locally as a function of the relationships

he follows. Method according to one of claims 1 to 3, characterized in that the offset value F _{offset, i} (α / i) and the value proportional to the slip angle α _i according to the relationship

is determined, the offset value F _{offset, i} (α / i) from the term F _{y, i} (α / i) −F _{y, i} (α / i) · α / i) and that of the slip angle α _i proportional value can be determined from the term F / y, i (α / i) · α / i). Method according to one of claims 1 to 4, characterized in that the relationship of the slip angle α _i with the slip angle via the relationships

takes place, the float angle β as a function of the proportional value according to the relationship

is determined. Method according to one of claims 1 to 5, characterized in that that the roll angle and / or the road bank slope can be taken into account in a model.