DE10239254A1 - Driving stability regulation method for automobile using selective braking and/or reduction of engine torque for limiting slew velocity of vehicle - Google Patents

Abstract

The stability regulation method uses a vehicle reference model providing the inertia force in the transverse direction and the moment of rotation about the center of gravity axis, for generating at least one reference value for the slew velocity in correlation with the transverse inclination of the road surface, compared with the actual slew velocity of the vehicle for providing control signals for activation of at least one of the wheel brakes and/or for reduction of the engine torque.

Description

The invention relates to a method for controlling the driving stability, with a vehicle reference model in which from the equations of motion of Models representing the equilibrium of forces in the transverse direction and the moment equilibrium about the center of gravity, at least reference values for the yaw rate are generated.

From the DE 195 15 059 A1 a control circuit for controlling the driving stability of a vehicle is known in which a reference value for the yaw rate is determined on the basis of the measured steering angle and the driving speed based on the model. The calculation is carried out in a single-track model on the basis of equations of motion, which represent the balance of forces in the transverse direction and the moment equilibrium about the center of gravity axis.

In this vehicle dynamics control system becomes the reference yaw rate with a one-track vehicle model calculated as follows: First, the equations of motion for the horizontal Level set up.

a y m = ν (β + #) m = F lat, f + F lat, r # Θ = F lat, f l f - F lat, r l r (1) The lateral force F _{lat, r of} the rear axle is calculated with a linear tire model: F lat, r = C r α r

Der entsprechende Reifenschräglaufwinkel α_lim ist

For the calculation of the side force F _{lat, f of} the front axle is a bent linear tire model ( 4 ) with limitation of the maximum lateral force F _{latmax, f} used. The break point of the estimated coefficient of friction μ _est is determined as follows

The corresponding tire slip angle α _lim is

The maximum possible tire slip angle α _max was determined experimentally and is dependent on the coefficient of friction μ _est : α Max = k1 + k2 ∙ μ est (5)

Thereafter, the lateral force F _{lat, f of} the front axle is calculated as a function of the tire slip angle α _f as follows:

The tire slip angles α _f and α _r are calculated using the kinematic relationship:

The state variables β _ref and # _{Mod were calculated} from the equation ( 1 ) and the measured variable δ _M and the reference speed ν _ref used.

Bei der Berechnung von β_set wurde die Gleichung (1) mit den Annahmen von . _ref = 0 , #_Mod = 0 und F_lat,f – F_max benutzt .Substituting the two tire side forces into equation (1) results in the motion quantities. _ref and # _mod . By numerical integration of the motion quantities β _ref and # _Mod , the state variables β _ref and # _{Mod are} calculated. As long as this calculated yaw rate # _Mod does not exceed the maximum possible stable limit value, it is used as reference yaw rate # _ref . Otherwise, a reset of the state variables β _ref and # _{Mod is carried out} as follows:

In the calculation of β _set , equation (1) was adopted with the assumptions of. _ref = 0, # _Mod = 0 and F _{lat, f} - F _max used.

In order to avoid misregistration in the banked curves, another method for detecting the road bank (eg DE 195 38 616 A1 . EP 0 957 340 A2 . EP 0 957 339 A2 ) required. As a result, on the one hand always incorrect rules in the banked turns occur and on the other hand necessary regulations on a flat road due to incorrect detection of the road bank not done or made too late.

When resetting the state variables, the assumptions of. _{met ref} = 0, # _Mod = 0, which are sometimes wrong.

This causes large jumps for the state quantity _βset . In doing so, the reference yaw rate is calculated incorrectly for a long time and misregistration is inevitable in such situations.

With the known method for the calculation The reference yaw rate thus results in the following problems:

• (a) Equation (1) only applies to roads without Bank. Therefore, the reference yaw rate is on lanes with Bank not correct. To the possible mistreatment in the Avoiding steep turns is another measure for recognizing the road bank required. If the road bank is recognized, the control thresholds will be expanded accordingly. This creates further problems:
• (b) Because of the unreliable and not timely detection or calculation of the bank can Mistakes in the steep curves occur.
• (c) Because of the unreliable Calculation of the bank becomes the necessary regulation on the level carriageways not or too late activated.
• (d) Upon detection of the banked turns, the thresholds become widened evenly in the two directions. Because of the wrong reference yaw rate in the banked curves, the Control unbalanced.
• (e) When the state variables β _ref and # _Mod are reset, there is sometimes a big jump from β _set because the assumptions of. _ref = 0 and # _mod = 0 are wrong. In doing so, the reference yaw rate is calculated incorrectly for a long time, and misregistration is inevitable in such situations.

The invention is based on the object to improve a method of controlling the driving stability to that a setpoint specification is achieved, the real movement behavior corresponds to the vehicle and a more accurate driving stability control (ESP) allowed.

According to the invention, this object is achieved by designing a generic method such that the vehicle reference model also takes into account the lateral acceleration and / or the components of the lateral acceleration in such a way that the reference value of the yaw rate is determined in correlation to the bank inclination and from the comparison of the bank-dependent reference variable as desired value the yaw rate of the vehicle with by means of a continuously measured actual yaw rate of the vehicle drive signals to a deviation of the respective actual value of each relevant setpoint compensatory influencing activation of at least one wheel brake of the vehicle and / or Re Duction of the motor drive torque can be generated.

According to the invention this task will continue solved by that the vehicle reference model also the lateral acceleration and / or Proportions of the lateral acceleration are taken into account such that the reference value of the slip angle in correlation to the bank inclination determined and from the comparison of the bank-dependent reference variable as a setpoint the slip angle of the vehicle with by means of a continuously determined Actual slip angle of the vehicle control signals to a deviation of respective actual value of each relevant setpoint compensatory influencing activation of at least one wheel brake of the vehicle and / or to reduce the engine drive torque.

The object is achieved by solved a method for controlling the driving stability, as the reference the yaw rate and the slip angle is determined in the single-track model.

Advantageous developments of Invention are in the subclaims specified.

The special advantages of the new Procedure opposite the acquaintances are:

• a) The new procedure has the bank of the Lane already considered in the equations of motion. This is the calculated Reference size too for carriageways with Banks correct. That is why the known recognition of the road bank no longer necessary. This reduces the computational effort.
• b) The new method can correct the errors in the banked curves significantly reduce and improve the control quality.
• c) The new method does not need threshold expansion for yaw rate regulation because of a recognized bank. This situation can be avoided be that because of supposed detection of a lane bank and false expansion of the control thresholds a necessary regulation on the flat lane too late or not done.
• d) With a model can the two most important benchmarks for the driving dynamics regulations be calculated at the same time. This allows possible conflicts between the Both control variables are avoided.
• e) The new method no longer needs the assumptions of β _ref = 0 and # _Mod = 0 for the resetting of the state quantities, which are sometimes wrong and could cause a large jump for the state quantity _βset . As a result, the control quality can be improved after the state variables have been reset.
• f) In the new method, the state variable β _{ref is} no longer calculated by the integration of the motion quantity β _ref , but directly according to equation (19) or (20) or (21). This reduces the computational effort and improves model accuracy.

The consideration of gravity in the vehicle motion equations for the calculation of the reference quantities is advantageous. For this, the measured lateral acceleration a _{y, M is used} as the input variable. As a result, the calculated reference quantities are always correct regardless of the road bank. Therefore, an additional detection of the road bank and a rule threshold expansion in the banked curves is no longer necessary. This considerably simplifies calculations and application of vehicle regulations. By taking into account gravity in the vehicle motion equations, the calculation of the state quantity β _Mod according to equation (14) is also considerably simplified, since the calculation of the motion quantity β _Mod and its integration is no longer necessary. Furthermore, it is advantageous that the two reference variables are calculated simultaneously with the same model, so that the possible conflicts between the two control variables are avoided.

An embodiment of the invention is shown in the drawing and will be described in more detail below.

Show it:

1 a schematic representation of the essential variables of a one-track vehicle model in a coordinate system according to the invention

2 a schematic representation of the gravity component for the vehicle movement

3 a schematic representation of the proportions of the measured lateral acceleration

4 a schematic representation of a model for the tire force on the front axle

5 a scheme for the calculation of the reference quantities This is a new method for the calculation of the reference quantities of yaw rate and slip angle for the vehicle regulations. The calculation of the reference yaw rate (also called reference yaw rate) is an improvement over the known method since the calculated reference yaw rate is suitable for all possible lanes. The calculation of the reference floating angle is a completely new procedure.

In this case, the equations of motion of the vehicle are set up in the vehicle-fixed coordinate system x, y and z, which is parallel to the transverse plane with the z-axis perpendicular to the road plane and with the y-axis ( 1 ). Taking into account the gravity component F _{y, G} in the y direction the equations of motion are as follows: a y m = F lat, f + F lat, r + F y, G = F lat, f l f - F lat, r l r ( 9 )

The gravity component F _{y, G} depends on the road bank ( 2 ). There is the following relationship between F _{y, G} and the road bank angle αQ F y, G = -mg sin (α Q ) (10)

In the driving stability control (ESP system), the lateral acceleration is measured with a sensor. The measured variable is denoted by a _{y, M} , which contains, in addition to the correct vehicle acceleration a _y, also further components a _{y , W} and a _{y , G} which are produced by superstructure rolling motion (FIG. 3 , Roll angle φ) and the road bank are caused. a y, M = a y + a y, W + a y, G ≈ a y + gsinφ + gsinα Q (11)

The roll angle φ can be achieved with a quasi-stationary roll model estimated.

Dabei entspricht der Konstante k_W dem Aufbauwankwinkel bei einer Stationärkreisfahrt mit a_y,W = g.Combining the two equations yields the following relation with the simplification φ ≈ sinφ

In this case, the constant k _W corresponds to the body roll angle during a stationary cycle with a _{y, W} = g.

Substituting equations (10) and (13) into equation (9) yields the following equations of motion: a y, M ∙ (1 - k W ) ∙ m = F lat, f + F lat, r (14) and F lat, f l f - F lat, r l r (15)

For the estimation of the slip angles # _f , the state variables β _{ref, old} and # _Mod from the last calculation step and the equation (7) are used:

Depending on the relationship between the estimated slip angle # _f to the quantities α _lim from equation (4) and α _max from equation (5), the model state is defined as follows:

undAccordingly, the tire side forces are calculated by equations (2) and (6) in consideration of equation (7) as follows:

and

In this case, the state quantity β _mod to be newly searched is used in the equations. The sign ± in equation (18) is always identical to the sign of # _f . Substituting the equations ( 18 ) and (19) into the equation (14), the new state quantity β _ref is calculated as follows:

• a) For the case | # _f | ≤ α _lim , namely Mst = 1, holds
  
• b) For α _lim <| # _f | <α _max , ie with Mst = 2 there are
  
• c) For | # _f | ≥ α _max , ie with Mst = 3
  

With the new state quantity β _Mod , the tire side forces F _{lat, f} and F _{lat, r are} calculated according to (18) and (19). If one puts the tire forces into equation (15), then the yaw acceleration results

The new state variable Ψ _Mod is calculated by the numerical integration of Ψ _Mod .

mit |#Mod| > #set (26) überschreitet, darin wird eine Zurücksetzung für die Referenzgierrate #_ref durch geführt. Dann gilt: #Mod = sign(#Mod)∙#set (2) If the state variable Ψ _{Mod sets} the following maximum possible stable limit Ψ _set

With | # Mod | ># set (26) exceeds, in which a reset for the reference _yaw rate # _{ref is performed} by. Then: # Mod = sign (# Mod ) ∙ # set (2)

und βMod = βset (29) For the state quantity β _Mod , a reset is also performed according to equation (22) as follows:

and β Mod = β set (29)

The reference quantities β _ref and # _ref can be derived by a low pass from the state variables β _Mod and # _Mod as follows: β ref = λ beta ∙ (β ref, old - β Mod ) + β Mod (30) # ref = λ PSIP ∙ (# ref, old - # Mod ) + # Mod (31)

The procedure for calculating the reference quantities according to the new method is described in 5 shown with a flow chart.

Because the influence of the road bank on the vehicle dynamics is already taken into account in the equations of motion (9), the reference variables β _ref and # _{ref are} also suitable for lanes with transverse slopes. Thus, an expansion of the control thresholds for the yaw rate control in the banked curves is no longer necessary. As a result, possible errors can be avoided.

In addition to the steering angle δ _M , the reference speed ν _ref , the estimated coefficient of friction μ _est and the measured lateral acceleration a _{y, M is} required as input variables for the new method.

Claims (10)

A method for controlling driving stability, comprising a vehicle reference model in which at least reference values for the yaw rate are generated from the model's equations of motion representing the transverse and center equilibrium of forces, characterized in that the vehicle reference model also includes the lateral acceleration and / or or components of the lateral acceleration are taken into account in such a way that the reference value of the yaw rate is determined in correlation to the lateral inclination of the roadway and from the comparison of the bank-dependent reference variable as desired value of the yaw rate of the vehicle with drive signals to a deviation of the respective actual value by means of a continuously measured actual yaw rate of the vehicle from the respective relevant setpoint compensatory influencing activation of at least one wheel brake of the vehicle and / or to reduce the engine drive torque produce become T. A method according to claim 1, characterized in that the Reference size in one Single track model is determined. Device according to claim 2, characterized in that the reference value of the yaw rate by the evaluation of the equations of motion a y m = F lat, f + F lat, r + F y, G # Θ = F lat, f l f - F lat, r l r (9) is checked with the dependent of the road bank gravity proportion F _{y, G.} A method according to claim 3, characterized in that the reference value of the yaw rate by the evaluation of the relationship between F _{y, G} and the road bank angle α _Q F y, G = -Mg sin (α Q ) 1 is determined. Method according to one of claims 1 to 4, characterized in that the reference value of the yaw rate # _Mod by numerical integration according to the relationship

involving

is determined. Method for controlling driving stability, with a vehicle reference model, in which of the equations of motion of the model, the balance of power in the transverse direction and the moment equilibrium about the axis of gravity reproduce, reference values are generated, characterized in that the vehicle reference model also the lateral acceleration and / or Proportions of the lateral acceleration are taken into account such that the reference value of the slip angle in correlation to the bank inclination it averages and from the comparison of the bank-dependent reference value as a setpoint the slip angle of the vehicle with by means of a continuously determined Actual float angle the vehicle drive signals to a deviation of the respective Actual value of the respective relevant Setpoint compensatory influencing activation at least a wheel brake of the vehicle and / or to reduce the engine drive torque be generated. A method according to claim 6, characterized in that the Reference size of the slip angle is determined in a single-track model. Method according to claim 6 or 7, characterized in that in | # _f | ≥ α _max , ie for Mst = 3 the slip angle according to the relationship

is determined. Method according to claim 6 or 7, characterized in that in | # _f | ≤ α _lim , namely Mst = 1, the slip angle according to the relationship

is determined. 10. Method according to claim 6 or 7, characterized in that when α _lim <| # _f | <α _max , so with Mst = 2 the slip angle according to the relationship

is determined. Method according to one of the preceding claims, characterized characterized in that as a reference the yaw rate and the slip angle are determined in the single track model.