JP2005145106A - Vehicle motion control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle motion control device capable of controlling the behavior of a vehicle in a stable direction even if a drive force difference occurs on right and left drive wheels. <P>SOLUTION: This vehicle motion control device comprises a vehicle motion control means which calculates the front wheel auxiliary steer angle or rear wheel auxiliary steer angle of a vehicle model based on the detected steering wheel steer angle and vehicle speed and outputs instruction signals to an auxiliary steer angle adding means. The device also comprises a drive force difference detection means detecting the drive force difference between the right and left drive wheels and an auxiliary steer angle correction means correcting the auxilary steer angle based on the detected drive force difference. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle motion control device that includes a steering control device that gives an auxiliary steering angle to a front wheel or a rear wheel, and controls behavior of the vehicle.

Conventionally, a technique described in Patent Document 1 is described as a technique for stabilizing vehicle behavior when a drive wheel slips. In this publication, in a configuration in which an auxiliary rudder angle is given to the rear wheel, when the drive wheel slips, in the case of a front wheel drive vehicle, the rear wheel steering angle is used as a rear wheel steering angle to perform reverse-phase steering to alleviate the understeer tendency, In the case of a wheel drive vehicle, a technique is disclosed in which an in-phase steering with the front wheels is performed as the rear wheel steering angle to suppress the oversteer tendency.
JP-A-5-170122.

  Here, the upper limit value of the driving force is limited by the road surface friction coefficient from the relationship of action and reaction. Even if the left and right driving forces output from the driving device to the driving wheels are the same, if only the road surface friction coefficient of one driving wheel is grounded, the driving force of the driving wheel is reduced and the other driving force is reduced. The driving force of the wheel (the one with the higher road surface friction coefficient) becomes larger. Therefore, a yaw moment is generated due to the left / right driving force difference. Under such circumstances, the technique described in Patent Document 1 only corrects based on the slip amount of the drive wheel, and therefore obtains a steering target value for obtaining a desired vehicle behavior. There was a risk that the driver could feel uncomfortable.

  An object of the present invention is to provide a vehicle motion control device capable of controlling the behavior of a vehicle in a stable direction even when a driving force difference occurs between left and right drive wheels.

  In order to achieve the above object, vehicle motion control that calculates a front wheel auxiliary rudder angle or a rear wheel auxiliary rudder angle from a vehicle model based on the detected steering angle and vehicle speed, and outputs a command signal to the auxiliary rudder angle giving means. In the vehicle motion control apparatus comprising the means, a driving force difference detecting means for detecting a driving force difference between the left and right driving wheels, and an auxiliary steering angle correcting means for correcting the auxiliary steering angle based on the detected driving force difference. As a result, the above-mentioned problems have been solved.

  In the present invention, by correcting the auxiliary steering angle on the basis of the driving force difference between the left and right driving wheels, it is possible to suppress fluctuations in the vehicle behavior and to suppress the driver's uncomfortable feeling.

Hereinafter, although the embodiment of the steering control device for vehicles in the present invention is described based on an example, the present invention is not limited to the example.

  The vehicle steering control device of the present invention includes a front and rear wheel auxiliary steering angle control device that gives auxiliary steering angles to the front and rear wheels, and a brake control device that controls vehicle behavior by controlling the braking force of four wheels. .

  FIG. 1 is an overall system diagram illustrating a basic configuration of a vehicle behavior control device including a front and rear wheel auxiliary steering control device and a brake control device according to a first embodiment. A steering unit 14 for steering the front wheels 12L and 12R based on a driver's steering input is provided on the front wheels 12L and 12R of the vehicle to which the vehicle steering control device of the first embodiment is applied. Further, the steering unit 14 is provided with a front wheel steering actuator 7 that gives an auxiliary steering angle to the front wheels 12L and 12R by an electric motor. Further, a rear wheel steering actuator 8 for providing an auxiliary steering angle to the rear wheels 13L and 13R is provided.

  The front wheel steering actuator 7 and the rear wheel steering actuator 8 give desired steering angles to the front wheels 12L and 12R and the rear wheels 13L and 13R by an electric motor based on commands from the front wheel steering controller 4 and the rear wheel steering controller 5. It is configured as follows. At this time, the front wheel steering controller 4 receives the front wheel steering angle from the front wheel side steering angle sensor 41 that detects the actual steering angle of the front wheels, and executes feedback control so as to match the target front wheel steering angle. Similarly, the rear wheel steering controller 5 receives the rear wheel steering angle from the rear wheel side steering angle sensor 51 that detects the actual steering angle of the rear wheel, and executes feedback control so as to match the target rear wheel steering angle. Is done. Note that a specific providing mechanism is a well-known technique and will not be described.

  A brake actuator 9 is provided that can independently control the brake hydraulic pressure of each wheel. Based on a command from the brake controller 6, the brake fluid pressure of the four wheels is controlled to a desired fluid pressure. The brake controller 6 receives the pressure from the pressure sensor 10 that detects the brake fluid pressure of each wheel, and executes feedback control so as to match the target fluid pressure. Note that a specific hydraulic pressure control mechanism is a well-known technique and will not be described.

  A steering control controller 3 includes a steering angle sensor 1 (corresponding to a steering wheel angle detection means) that detects a driver's steering angle θ using a pulse encoder or the like, and a vehicle speed sensor 2 (vehicle speed detection) that detects an actual vehicle speed V of the vehicle. The detection signals from the pressure sensor 10 for detecting the wheel cylinder pressure of each wheel and the wheel speed sensor 11 for detecting the wheel speed of each wheel are inputted. Based on these input signals, the front wheel auxiliary rudder angle, the rear wheel auxiliary rudder angle and the brake fluid pressure are calculated, and command signals are output to the actuators. Hereinafter, the configuration of the steering control controller 3 will be described.

  FIG. 2 is a block diagram showing the configuration of the steering control controller 3. The steering control controller 3 includes a target value generation unit 31 and a target output value generation unit 32.

The target value generation unit 31 includes a vehicle model calculation unit 311 and a target value calculation unit 312 as shown in the block diagram showing the configuration of the target value generation unit 31 in FIG.
The vehicle model calculation unit 311 calculates vehicle parameters from the steering angle θ and the vehicle body speed V using a two-wheel model. The vehicle parameter calculation will be described in detail later.
The target value calculation unit 312 determines the target yaw rate ψ ′ ^* and the target lateral velocity V ^* y of the vehicle from the steering angle θ, the vehicle body speed V, and the vehicle parameters.

As shown in the block diagram showing the configuration of the target output value generation unit 32 in FIG. 4, the target output value generation unit 32 has a target rear wheel steering angle calculation unit 321, a target front wheel steering angle and target brake hydraulic pressure calculation unit 322, and The target front / rear wheel correction steering angle calculation unit 323 is configured.
The target front wheel steering angle calculation unit 321 determines the target rear wheel steering angle δ ^* from the target yaw rate ψ ′ ^* of the vehicle and the target lateral speed V ^* y.
The target front wheel steering angle and target brake hydraulic pressure calculation unit 322 calculates the target front wheel steering angle θ ^* and the target brake of each wheel from the target yaw rate ψ ′ ^* , the target lateral speed V ^* y, and the target rear wheel steering angle δ ^{* of the} vehicle. Determine the hydraulic pressure P ^* _br .
The target front and rear wheel correction steering angle calculation unit 323 includes a left driving wheel rotation angular velocity ω _L , a right driving wheel rotation angular velocity ω _R , a left driving wheel brake hydraulic pressure P _BL , a right driving wheel brake hydraulic pressure P _BR , and a target rear wheel steering angle. From δ ^* and target front wheel steering angle θ ^* , rear wheel steering angle target value δ ^* _s when driving on road surfaces with different road surface friction coefficients, and front wheel steering angle target value θ ^* when driving on road surfaces with different road surface friction coefficients _s , the final rear wheel steering angle target value δ ^* _f , and the final front wheel steering angle target value θ ^* _f are determined.

The front wheel steering controller 4 controls the front wheel steering actuator 7 so that the actual front wheel steering angle detected by the front wheel side steering angle sensor 41 matches the target front wheel steering angle θ ^* .

The rear wheel steering controller 5 controls the rear wheel steering actuator 8 so that the actual steering angle of the rear wheel detected from the rear wheel side steering angle sensor 51 coincides with the target front wheel steering angle δ ^* .

The brake controller 6 controls the brake actuator 9 so that the wheel cylinder pressure of each wheel detected from the pressure sensor 10 matches the target brake fluid pressure P ^* _br of each wheel.

ここで、

（式２）

である。 [Vehicle Model Calculation in Vehicle Model Calculation Unit 311]
The vehicle model calculation unit 311 calculates vehicle parameters from the vehicle model shown below.
In general, assuming a two-wheel model, the yaw rate and lateral speed of the vehicle can be expressed by the following equation (1).
(Formula 1)

here,

(Formula 2)

It is.

（式４）

となる。

When the transfer function of the yaw rate and the lateral speed with respect to the front wheel steering is obtained from the state equation, it is expressed by the following equations (3) and (4).
(Formula 3)

(Formula 4)

It becomes.

ここで、
（式６）

The yaw rate transfer function is expressed by the following equation (5) from equation 3.
(Formula 5)

here,
(Formula 6)

ここで、
（式８）

Similarly, the lateral velocity transfer function is expressed by the following equation 7 from equation 4.
(Formula 7)

here,
(Formula 8)

が求められる。 From the above, vehicle parameters

Is required.

[Target Value Calculation in Target Value Calculation Unit 312]
A target yaw rate and a target lateral speed are obtained from the vehicle speed and vehicle parameters in the target value calculation unit 312 and a target value parameter described later.

The target yaw rate is expressed by the following equation 9 from equation 5.
(Formula 9)

The target lateral velocity is expressed by the following equation 10 from equation 7.
(Formula 10)

ただし、yrate_gain_map，yrate_omegn_map，yrate_zeta_map，yrate_zero_mapはそれぞれ図５，図６，図７及び図８に示す車速に応じて設定されたマップから算出されるチューニングパラメータである。 Here, the parameter of the target yaw rate is expressed by the following equation 11.
(Formula 11)

However, yrate_gain_map, yrate_omegn_map, yrate_zeta_map, and yrate_zero_map are tuning parameters calculated from maps set in accordance with the vehicle speeds shown in FIGS. 5, 6, 7 and 8, respectively.

ただし、vy_gain_map，vy_omegn_map，vy_zeta_map，vy_zero_mapはそれぞれ図９，図１０，図１１及び図１２に示す車速に応じて設定されたマップから算出されるチューニングパラメータである。 The parameter of the target lateral speed is expressed by the following formula 12.
(Formula 12)

However, vy_gain_map, vy_omegn_map, vy_zeta_map, and vy_zero_map are tuning parameters calculated from maps set in accordance with the vehicle speeds shown in FIGS. 9, 10, 11, and 12, respectively.

このモデルから下記式１４を得る。
（式１４）

よって、目標前輪舵角δ^*は、下記式１５により表される。
（式１５）

[Target Steering Angle Calculation in Target Output Value Generation Unit 32]
(Target rear wheel steering angle calculation in the target rear wheel steering angle calculation unit 321)
The target rear wheel steering angle δ ^* is calculated from the target yaw rate ψ ′ ^* and the target lateral velocity Vy ^* . Here, the following equation 13 is obtained from the two-wheel model of equation 1.
(Formula 13)

From this model, the following equation 14 is obtained.
(Formula 14)

Therefore, the target front wheel steering angle δ ^* is expressed by the following formula 15.
(Formula 15)

ここで、δ^* _maxは、後輪最大操舵角とする。また、sign(a)とは、ａの符号のみを出力するもので、a＝10であれば、＋１を出力し、a＝-10であれば−１を出力する関数である。 However, since the steering angle of the rear wheel steering angle is generally limited, the target rear wheel steering angle is set to a value δ ^* _lim obtained from the following equation 16 as a value with an upper limit by the following equation.
(Formula 16)

Here, δ ^* _max is the rear wheel maximum steering angle. Sign (a) is a function that outputs only the sign of a, and outputs +1 if a = 10 and outputs -1 if a = -10.

[Target Front Wheel Steering Angle and Target Brake Fluid Pressure Calculation Unit 322 Target Front Wheel Steering Angle and Brake Fluid Pressure Calculation]
When the rear wheel steering angle control is saturated, vehicle motion control is executed by front wheel steering angle control and braking force control. That is, an equation of motion based on the yaw angular acceleration generated by the front wheel steering angle and the left and right brake hydraulic pressure difference is used. Then, the target front wheel steering angle θ ^* and the target brake hydraulic pressure P ^* _br of each wheel are calculated from the target yaw rate ψ ′ ^* , the target lateral speed Vy ^* , and the limited target rear wheel steering angle δ ^* _lim .

If the yaw angular acceleration generated by the left and right brake fluid pressure difference is set as ψ ″ ^* _br , the equation of motion of the vehicle is expressed by the following equation (17).
(Formula 17)

（式１９）

Here, when the limited target rear wheel steering angle δ ^* _lim is known (basically, this control is performed when the rear wheel steering angle is saturated, so δ ^* _lim = δ ^* _max ). The target front wheel rudder angle θ ^* for realizing the target yaw rate ψ ′ ^* , the target lateral acceleration Vy ^*, and the yaw angular acceleration ψ ″ ^* _br due to the left and right brake hydraulic pressure difference are expressed by the following equations (18) and (19). .
(Formula 18)

(Formula 19)

（式２１）

Next, the target brake fluid pressure differences P ^* _brf and P ^* _brr between the front and rear wheels are expressed by the following equations (20) and (21) from the yaw angular acceleration ψ ″ ^* _br generated by the left and right brake fluid pressure difference.
(Formula 20)

(Formula 21)

Therefore, the target brake fluid pressure of each wheel has the following relationship.

[Correction steering amount calculation]
When driving is performed on road surfaces having different road surface friction coefficients on the left and right, idling occurs on the drive wheel having the lower friction coefficient due to the difference between the left and right friction coefficients. Since the driving force is generated on the driving wheel having the higher road surface friction coefficient, vehicle yaw rate due to the driving force is generated.

ここで、T_tは駆動軸トレッドである。 The left wheel driving force is FL, the right wheel driving force is FR, and the yaw angular acceleration ψ ″ _s of the vehicle generated by the left / right difference is expressed by the following equation (22).
(Formula 22)

Here, T _t is a drive shaft tread.

（式２４）

よって、上記式２３，２４から左右駆動力差は下記式２５の関係を得る（特許請求の範囲に記載の駆動力差検出手段に相当）。
（式２５）

ここで、

(When installing a conventional differential gear on the drive wheel)
The following equations 23 and 24 are obtained from the equation of motion of the wheel.
(Formula 23)

(Formula 24)

Therefore, the right and left driving force difference from the above equations 23 and 24 obtains the relationship of the following equation 25 (corresponding to the driving force difference detecting means described in the claims).
(Formula 25)

here,

（式２７）

よって、上記式２６，２７から左右駆動力差は下記式２８の関係を得る（特許請求の範囲に記載の駆動力差検出手段に相当）。
（式２８）

ここで、
（式２９）

ただし、

(When a conventional differential gear is mounted on the drive wheel and the brake has a limited slip differential gear (brake LSD) function)
From the brake torque T _BL generated by the left and right brake LSD, the brake torque T _BR generated by the right wheel brake LSD, and the equation of motion of the wheel, the following relations 26 and 27 are obtained.
(Formula 26)

(Formula 27)

Therefore, the right and left driving force difference from the above equations 26 and 27 obtains the relationship of the following equation 28 (corresponding to the driving force difference detecting means described in the claims).
(Formula 28)

here,
(Formula 29)

However,

From the above relationship, the yaw angular acceleration ψ ″ _{s of} the vehicle generated by the difference between the left and right driving forces is obtained.

ここで、θ_s ^* は路面摩擦係数の異なる路面を走行した場合の前輪舵角目標値、δ_s ^* は路面摩擦係数の異なる路面を走行した場合の後輪舵角目標値である。 On the other hand, vehicle target values ψ ′ ^* and Vy ^* for suppressing vehicle yaw rate generated when driving on road surfaces having different road surface friction coefficients on the left and right are:
ψ ' ^* = 0, Vy ^* = 0
And the target value ψ '' _s ^* of the vehicle yaw angular acceleration necessary to suppress the generated vehicle yaw rate is
ψ '' _s ^* = -ψ '' _s
Therefore, when substituting into the equation 14, the following equation 30 is obtained.
(Formula 30)

Here, θ _s ^* is the front wheel steering angle target value when traveling on road surfaces with different road surface friction coefficients, and δ _s ^* is the rear wheel steering angle target value when traveling on road surfaces with different road surface friction coefficients.

Therefore, the rear wheel steering angle target value δ _s ^* when traveling on road surfaces with different road surface friction coefficients of the left and right drive wheels is expressed by the following equation 31.
(Formula 31)

しかしながら、後輪の制御可能舵角には制限があるため、制限された最終的な後輪舵角目標値δ_s ^* _lim は、下記式３３により表される。
（式３３）

Here, the final rear wheel steering angle target value δ _f ^* is expressed by the following equation 32.
(Formula 32)

However, since the controllable steering angle of the rear wheels is limited, the limited final rear wheel steering angle target value δ _s ^* _lim is expressed by the following equation 33.
(Formula 33)

よって、制限された路面摩擦係数の異なる路面を走行した場合の後輪舵角目標値δ_sf ^* は下記式３５により表される。
（式３５）

Therefore, the final rear wheel steering angle target value δ _f ^* is expressed by the following equation 34 from the limited final rear wheel steering angle target value δ _s ^* _lim .
(Formula 34)

Therefore, the rear wheel steering angle target value δ _sf ^* when traveling on road surfaces with different limited road surface friction coefficients is expressed by the following Expression 35.
(Formula 35)

The front wheel steering angle target value θ _s ^* based on the rear wheel steering angle target value δ _sf ^* when traveling on road surfaces with different limited road surface friction coefficients is expressed by the following Expression 36.
(Formula 36)

From the above, the final front wheel steering angle target value θ _f ^* and the final rear wheel steering angle target value δ _f ^* are calculated as the following Expression 37.
(Formula 37)

  As described above, in the vehicle motion control apparatus of the first embodiment, the road surface friction coefficient is obtained by correcting the target front wheel steering angle and the target rear wheel steering angle based on the difference between the left and right driving forces of the driving wheels. Even when traveling on different road surfaces on the left and right, the yaw rate generated in the vehicle can be suppressed.

  In the first embodiment, the front wheel steering actuator, the rear wheel steering actuator, and the brake actuator are provided to correct the target front wheel steering angle and the target rear wheel steering angle. However, the present invention is not limited to this configuration. For example, it may be configured to include at least one of the actuators, and the target value for each actuator may be corrected based on the left-right driving force difference.

(simulation)
In FIG. 13, when the right driving wheel is on a dry road surface (friction coefficient: about 1.0) and the left driving wheel is on a low μ road (friction coefficient: about 0.3), the steering starts straight from the stop. It is a time chart in.

  13A shows the yaw angle generated in the vehicle, FIG. 13B shows the yaw rate generated in the vehicle, FIG. 13C shows the rear wheel auxiliary steering angle, and FIG. Represents the front wheel auxiliary rudder angle.

  When the vehicle starts, yaw rate is generated in the vehicle due to the difference between the left and right driving forces, but yaw rate = 0 is realized by giving the rear wheel auxiliary rudder angle and the front wheel auxiliary rudder angle based on the calculation in the first embodiment. I understand that I can do it.

It is the schematic which shows the basic composition of the vehicle motion control apparatus in Example 1. FIG. 2 is a block diagram illustrating a configuration of a steering control controller in Embodiment 1. FIG. FIG. 3 is a block diagram illustrating a configuration of a target value generation unit in the first embodiment. FIG. 3 is a block diagram illustrating a configuration of a target output value generation unit in the first embodiment. 3 is a map showing a yaw rate parameter in the first embodiment. 3 is a map showing a yaw rate parameter in the first embodiment. 3 is a map showing a yaw rate parameter in the first embodiment. 3 is a map showing a yaw rate parameter in the first embodiment. 3 is a map showing a lateral speed parameter in the first embodiment. 3 is a map showing a lateral speed parameter in the first embodiment. 3 is a map showing a lateral speed parameter in the first embodiment. 3 is a map showing a lateral speed parameter in the first embodiment. 6 is a time chart showing a simulation result in consideration of a difference in right and left driving force in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering angle sensor 2 Vehicle speed sensor 3 Steering control controller 4 Front wheel steering controller 5 Rear wheel steering controller 6 Brake controller 7 Front wheel steering actuator 8 Rear wheel steering actuator 9 Brake actuator 10 Pressure sensor 11 Wheel speed sensor 12 Front wheel 13 Rear wheel 14 Steering unit 41 Front wheel side steering angle sensor 51 Rear wheel side steering angle sensor

Claims (2)

A steering wheel angle detecting means for detecting a steering wheel angle;
Vehicle speed detection means for detecting the vehicle speed;
An auxiliary rudder angle giving means for giving an auxiliary rudder angle to the front wheel or the rear wheel;
Vehicle motion control means for calculating a front wheel auxiliary rudder angle or a rear wheel auxiliary rudder angle from a vehicle model based on the detected steering wheel steering angle and vehicle speed, and outputting a command signal to the auxiliary rudder angle giving means;
In a vehicle motion control device comprising:
A driving force difference detecting means for detecting a driving force difference between the left and right driving wheels;
Auxiliary steering angle correction means for correcting the auxiliary steering angle based on the detected driving force difference;
A vehicle motion control device characterized by comprising: The vehicle motion control device according to claim 1,
The auxiliary rudder angle correcting means corrects the vehicle based on a yaw angular acceleration obtained from a left / right driving force difference.

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