JPH05270422A - Method for determining transverse velocity and/or attitude angle of vehicle - Google Patents

Abstract

PURPOSE: To enhance traveling stability by similarly determining a normal force, determining a longitudinal force of each wheel from a brake pressure, calculating a transverse force obtained from a characteristic diagram and a normal force and a transverse acceleration from a longitudinal force, and calculating an attitude angle. CONSTITUTION: To simulate a transverse force of a tire in a nonlinear range of a relatively large transverse drift angle, a characteristic diagram 4 for the transverse force converted to a static normal force is determined. Thus, a transverse drift angle α1 from a block 2 and a using frictional coefficient μ0 from a block 3 are used, and a converted transverse force fy is obtained by an interpolating method. A transverse force of each wheel is obtained by a block 6 from a normal force Fz1 from the block 1 and a transverse force fy , and a transverse acceleration is obtained by a block 7 from the value. A transverse speed Vy is obtained by integrating the transverse acceleration, longitudinal acceleration vk and a yaw speed ω by a block 9, and vehicle stability and the angle β for the stability are obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to vehicle lateral velocity and / or
Alternatively, it relates to a method of determining the posture angle.

[0002]

Vehicle lateral velocity and / or attitude angle are important variables for determining vehicle stability in critical vehicle conditions and for control methods for vehicle stabilization.

Known methods for determining these variables are based on extremely expensive sensor technology.

[0004]

SUMMARY OF THE INVENTION It is an object of the invention to provide a model-supported vehicle lateral velocity and / or attitude angle determination method using inexpensive sensors.

[0005]

SUMMARY OF THE INVENTION Two types of evaluation devices are described here, which differ mainly in the required input variables. Version 1 requires steering angle, vehicle speed, yaw speed, lateral acceleration and wheel speed. Version 2 requires brake pressure instead of lateral acceleration.

Using the characteristic diagram for the determination of the cornering force on all wheels from the input variables, the model support evaluation algorithm described here provides the lateral velocity of the vehicle, The attitude angle can be determined.

The attitude angle is an important variable necessary for determining the running property of the vehicle. In particular, a large attitude angle must be reliably detected so that the running motion control device present in the vehicle can reliably stabilize the vehicle and avoid critical running conditions. Since the attitude angle or lateral velocity measurement is very expensive, an evaluation device is used in the present invention.

The attitude angle evaluation device must provide the attitude angle with sufficient accuracy not only in the linear range but also in the non-linear range, and in both the braked running motion and the unbraked running motion. I have to.

[0009]

EXAMPLE FIG. 1 shows a vehicle model used, a coordinate system used, and variables used.

This algorithm is divided into several parts. First, the normal force is approximately determined. The braking pressure determines the longitudinal force on each wheel. The lateral force is determined using the characteristic diagram and the normal force. From the lateral pulse set, the vehicle lateral speed evaluated by integration is calculated, and from this the attitude angle is calculated.

Two types of versions will be described here.
2 shows a block diagram of version 1, and FIG. 5 shows a block diagram of version 2.

The normal force F _z in FIG. 2 is obtained from a plane vehicle model (quasi-static observation). The normal force is divided into a static component that depends on the position of the center of gravity and two dynamic components that depend on longitudinal and lateral acceleration. The block 1 is supplied with the measured variable of the lateral acceleration a _y and the characteristic variable of the longitudinal acceleration a _x . Here the following holds:

[0013]

The longitudinal acceleration a _x can be determined from the reference velocity (a _x ≈V _ref ′). The reference speed or the vehicle speed is obtained from the wheel rotation speed by a known method.

The various symbols of the above equation will be seen in the last table of the text.

No longitudinal force is taken into account for the version 1 evaluation device.

Lateral force F _y and sideslip angle α at the tire
The generally non-linear relationship between and can be conditionally simulated with the simple equation F _y = −C _α · α · F _z . This formula provides a lateral force that can only be used in the small (linear) range of sideslip angles. In order to be able to simulate the lateral force of the tire even in the non-linear range, a characteristic diagram for the lateral force converted into a static normal force is determined (Fig. 3). The sideslip angle α _i coming from block 2 and the coefficient of friction of use μ ₀ obtained in block 3 are used as inputs for the characteristic diagram 4. At this time, the conversion lateral force f _y is obtained by the interpolation method as is known, and the equation (1-
The lateral force at each wheel is determined by multiplying the normal force determined in 4) (block 6). sign
α _i means the sign of α _i . Furthermore, this lateral force is reduced depending on the wheel slip λ in the block 5 to which the vehicle speed v _x and the wheel speed v _ri are fed. Characteristic diagrams are used for the front and rear axes, respectively.

For the front axis, the following holds:

[0019]

For the rear axis, the following holds:

[0021] here,

The friction coefficient μ ₀ used is determined in block 3 by the following relationship.

In order to be able to perform the interpolation of the characteristic diagram, the sideslip angle has to be determined. Be done. In block 2, the sideslip angle α _i of each axis is determined in a simple manner.

Side slip angle on the front axle:

[0025]

Side slip angle on the rear axle:

[0027] Here, a sensor is used for the yaw speed ω.

At block 7, the lateral acceleration a _y is determined from the wheel longitudinal and lateral forces as follows:

[0029]

[0030] it can.

Therefore, the lateral acceleration for the evaluation device is determined as follows:

[0032]

Therefore, the estimated lateral velocity is calculated by the multiplier 1
0, can be determined by subtractor 8 and integrator 9:

[0034]

If the measured lateral acceleration a _y is integrated,
For example, a lateral velocity with "drift" would be introduced when an offset occurs. By using the lateral acceleration determined from the evaluated force, the sideslip angle α
There is a negative feedback via the negative feedback which will prevent lateral velocity drift.

[0036]

[0037]

[0038]

In order to prevent a gradual increase of the attitude angle (model error dominates the lateral force value) in the case of straight running, in each case the lateral acceleration,
When the yaw angular velocity and the steering angle are below the specific limit values for a certain time or more, the evaluation lateral velocity is set to 0 by the block 12.

[0040] Reset:

(15) | a _y | <a _y0 and | ω
| <Ω ₀ and | δ _v | <δ _v0 where the values of a _y0 , ω ₀ and δ _v0 are constants.

FIG. 4 shows a comparison with the measured values of the evaluation of the posture angle and the lateral acceleration according to version 1. here,
The behavior of a two-sided steering angle jump at low friction coefficient (μ≈0.3) is shown. In this case, the vehicle is braked.

For version 2 described in FIGS. 5 and 6, most blocks correspond to the blocks of FIG. These blocks are given the same reference numerals but with a "'".

Also in this case, the normal force F _z is obtained from the plane vehicle model (quasi-static observation) in block 1 '. The normal force is divided into a static component that depends on the position of the center of gravity and two dynamic components that depend on longitudinal and lateral acceleration. here Be paid. Here the following holds:

[0045]

The longitudinal acceleration a _x can likewise be determined from the reference speed of the vehicle (a _x ≈v _ref ′). The reference speed or the vehicle speed is obtained from the wheel rotation speed by a known method.

The various symbols of the above equation will be seen from the last table in the text.

For the version 2 evaluation device (FIG. 5), the longitudinal force at the wheel is determined from the measured braking pressure or the evaluation braking pressure. The longitudinal force is set to zero when the brakes are not applied.

[0049]

In order to be able to simulate the lateral force of the tire even in the non-linear range, a characteristic diagram for the lateral force converted into a static normal force is determined (FIG. 3).
As inputs for the characteristic diagram (block 4 ′), the sideslip angle coming from block 2 ′ and the coefficient of friction used μ ₀ coming from block 3 ′ are again used. At this time, as is known, the converted lateral force is obtained by the interpolation method, and the normal force determined by the equation (16-19) is multiplied in the block 6'to obtain the lateral force at each wheel. Furthermore, this lateral force is reduced in the block _5'to which the vehicle speed v _x and the wheel speed v _ri are fed, depending on the wheel slip λ. Characteristic diagrams are used for the front and rear axes, respectively.

For the front axis, the following holds:

[0052]

For the rear axis, the following holds:

[0054] here,

The coefficient of friction used μ ₀ is obtained in block 3'by the following relation.

[0056]

In order to be able to carry out the interpolation of the characteristic diagram, the sideslip angle must also be determined. For the estimated lateral velocity, the value from the preceding calculation cycle is used. In block 2 ', the sideslip angle α _i of each axis is determined in a simple manner.

Side slip angle on front axis:

[0059]

Side slip angle on the rear axle:

[0061] Here, it is assumed that a sensor is used for the yaw speed ω and δ _h exists at this time.

[0062] The yaw rate is modeled. An error signal is determined from the difference between the modeled yaw angular velocity and the measured yaw angular velocity, and the error signal is used to modify the estimated lateral force on the front axis (block 15). This improves accuracy in most situations. Next, the evaluation yaw angular velocity must be determined by the law of conservation of angular momentum. In this case, for simplicity, δ _v and δ _h are small, that is, cos
(Δ _v ) ≈1, sin (δ _v ) ≈δ _v and cos (δ
_h ) ≈1, sin (δ _h ) ≈δ _h

[0063]

[0064]

The lateral force on the front axis determined by equation (21) is modified in block 15 using the error signal as follows:

[0066]

[0067] Is a function. With both parameters k ₁ and k ₂ , both error components are weighted accordingly in the correction. For example, k ₁ and k ₂ may have the following values:

K ₁ = 3000 × N _s / rad k ₂ =
3000 × N _s2 / rad.

In block 7 ', the lateral acceleration a _y
Is determined from the longitudinal and lateral forces at the wheels as follows:

[0070]

Assuming that the steering angles δ _v and δ _h are small, the term containing F _xi can be ignored.

Therefore, the lateral acceleration for the evaluation device 7'is determined as follows:

[0073]

[0074] It can be determined by 9 ':

[0075]

[0076] .

[0077] Ru:

[0078]

In order to prevent the posture angle from gradually increasing (the model error is superior to the value of the lateral force) in the case of straight running, the yaw angular velocity and the steering angle each exceed a specific limit value for a certain time or more. If it does, the block 12 'again sets the estimated lateral velocity to 0.

In the method according to version 2, when the following relations are established for a certain time or longer,

(33) | ω | <ω ₀ and | δ _v | <
δ _v0 where the values of ω ₀ and δ _v0 are constants.

[0082] A comparison is shown. Here, the behavior of a double-sided steering angle jump at a low friction coefficient (μ≈0.3) is shown. In this case, the vehicle is braked.

[Brief description of drawings]

FIG. 1 shows a vehicle model, coordinate system and variables used to describe the method of the present invention.

FIG. 2 is a block diagram of the version 1 method of the present invention.

FIG. 3 is a characteristic diagram with a coefficient of friction as a parameter between a ratio f _y and a sideslip angle α _v for obtaining a lateral force that can be converted into a static normal force.

FIG. 4 is a method of version 1 of the present invention, where μ =
Double-sided steering angle jump at 0.3 (90, -90,
The time transition of each variable at 0 degree is shown.

FIG. 5 is a block diagram of a version 2 method of the present invention.

FIG. 6 shows that in the method of version 2 of the present invention, μ =
Double-sided steering angle jump at 0.3 (90, -90,
The time transition of each variable at 0 degree is shown.

[Explanation of symbols]

Power v _x , v _y longitudinal / lateral velocity a _x , a _y longitudinal / lateral acceleration of vehicle δ _v , δ _h steering angle of front and rear axles ω yaw angular velocity α _v , α _h front and rear axle sideslip angle mu ₀ using the friction coefficient v _ri wheel speed of the shaft P _Bi brake pressure λi tire slip l _v, the distance l wheelbase b Wa距h the height of the center of gravity c _pi brake between the _{l h} front axle or rear axle and the center of gravity Amplification coefficient between pressure and brake torque r _R Wheel radius Θ Vehicle inertia moment about center of gravity vertical axis m Vehicle mass q Gravitational acceleration f _y Lateral force converted to normal force v _Fi Vehicle speed at wheel i v _sp Vehicle speed at center of gravity

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B62D 113: 00 137: 00 (72) Inventor William Stbert Federal Republic of Germany 7000 Stuttgart 1, Ha Optmannsreute 85 (72) Inventor Andreas Elvan Germany 7120 Bettichheim-Bissingen, Berliner Strasse 24

Claims (7)

[Claims] 1. The coefficient of friction μ obtained (in 3)
₀ and a characteristic diagram for determining the lateral slip force α _i obtained (in 2) and the lateral force F _y converted to the static normal force F _z0 , and the parameter depending on the lateral slip angle α _i Using μ ₀ as the ratio (at 4) the ratio F _y / F _z = f _y
From the calculated normal force F _zi (in 1) and the ratio f _y (in 6) And; A method for determining a lateral velocity and / or an attitude angle of a vehicle characterized by: 2. 2. The method of claim 1, wherein the sideslip angle [alpha] _i is determined (at 2) from the acquisition variables of [delta] _v , [delta] _h (one or both). 3. The friction coefficient μ ₀ (in each axis) (in 3) is determined from the variables for obtaining or evaluating the lateral acceleration a _y and the variables for the longitudinal acceleration a _x. Method 1 or 2. 4. A vehicle mass longitudinal acceleration a _x acquisition or evaluation variable, and a vehicle mass lateral acceleration a _y acquisition or evaluation variable, and a vehicle conversion constant. 1 to 3. 5. The method according to any one of claims 1 to 4, wherein: 6. 6. The method according to claim 1, wherein the method is derived from δ _h . 7. 7. The method of claim 6, wherein the method is induced.