JPH1191608A - Vehicle motion control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow different vehicles to realize required motions irrespective of a road surface and the like by classifying transfer characteristics of a specific number of model formulae for calculating a target value of the vehicle motion into a primary characteristic capable of adjusting transition and steady-state characteristics and a secondary characteristic capable of adjusting the transition characteristics only for tuning values derived from different vehicles. SOLUTION: Among two setting portions BL1 and BL2 for setting target values of the vehicle motion, the first setting portion BL1 calculates a target yaw rate ψ' and a target yaw acceleration ψ" based on the detected angle θ and the detected vehicle speed VSP using parameters in accordance with the vehicle speed with the transfer function between the steering angle and the target yaw rate formed as the primary/secondary characteristics. The second setting portion BL2 calculates a target lateral velocity Vγ and a target lateral acceleration V'γ using the transfer function between the steering angle and the lateral velocity. The first and the second rear wheel steering angle instruction value calculation portions BL3 and BL4 calculate the first and the second target rear wheel steering angle ∫R1 , ∫R2 , respectively, and the rear wheel steering angle instruction value calculation portion BL5 calculates the target rear wheel steering angle ∫R so as to control the rear wheel steering angle device 2, thus simplifying the tuning operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle motion control device for controlling a vehicle motion such as a yaw rate and a lateral speed of a vehicle in response to a steering input, particularly, a vehicle motion during a turn.

[0002]

2. Description of the Related Art Conventionally, as a vehicle motion control device for controlling the yaw rate of a vehicle with respect to a steering input to maintain the stability of the vehicle, for example, a vehicle speed or a steering angle of a steering wheel, that is, a front wheel steering angle is determined. The target value of the yaw rate (vehicle motion) is calculated based on the model formula based on the vehicle equation, and the rear wheel steering angle command value required to match the yaw rate generated in the vehicle with the target value is calculated by a motion equation based on the vehicle specification value. In some cases, the yaw motion of the vehicle is controlled by calculating and controlling the rear wheel actual steering angle to follow the rear wheel steering angle command value so that the yaw rate set as the target value is achieved.

[0003] By the way, the main characteristic of the vehicle at the time of turning is set by the yaw motion, especially the yaw rate.
In recent vehicles, particularly sporty vehicles, there is a demand to control the lateral movement of the vehicle, that is, the movement such as lateral speed and lateral acceleration. That is, two different vehicle motions are controlled, and such a vehicle motion control device is described in, for example, Japanese Patent Publication No. 7-25320. In this vehicle motion control device, a target value of a yawing motion represented by, for example, a yaw rate and a target value of a lateral motion represented by a lateral speed are linearly combined from a vehicle model formula with respect to a steering input to obtain an overall vehicle By calculating a rear wheel steering angle command value such that the target value of the vehicle motion is achieved as a target value of the motion, different vehicle motions can be controlled by one control input. Note that the linear combination is a so-called weighted proportional sum, and the weight (proportional coefficient) related to one of the vehicle motion target values is D (D
= 0 to 1), the other weight (proportional coefficient) is represented by (1-D).

[0004]

However, although the conventional vehicle motion control device uses two different vehicle motion target values, the weights of the respective target values (stationary values) are basically equal. That is, for example, in a certain road surface friction coefficient state (hereinafter also simply referred to as road surface μ), a steady state yaw rate for a predetermined vehicle speed and a predetermined front wheel steering angle, that is, a steady characteristic of the yaw rate controls the vehicle's stability during turning. And want to set the vehicle motion characteristics at the time of turning as a direction. On the other hand, for example, it is desired that the steady-state characteristics of the lateral speed be basically the same even if the vehicle changes. Therefore, for example, when the weight (proportional coefficient) D or (1-D) is tuned so as to obtain a desired steady-state characteristic of the yaw rate, when, for example, it is desired to slightly modify the transient characteristic of the lateral speed, the entirety is again adjusted. It is highly likely that the weight (proportional coefficient) needs to be set again from the beginning while maintaining the balance.

[0005] Further, the model formula for calculating the target value of each vehicle motion basically assumes that the cornering power is constant. Therefore, depending on the road surface μ and the wheel slip angle,
Desired vehicle motion may not be achieved.

The present invention has been developed in view of these problems. Two different vehicle motion target values can be easily tuned, for example, between different vehicles, and the road surface μ can be adjusted.
It is an object of the present invention to provide a vehicle motion control device capable of achieving a desired vehicle motion irrespective of the wheel slip angle.

[0007]

In order to achieve the above object, according to the present invention, there is provided a vehicle motion control apparatus comprising:
Based on the steering angle and the vehicle speed, respective target values for two different vehicle motions are calculated from a predetermined model formula, and after each main vehicle is not steered so that each vehicle motion simultaneously achieves the two target values. In a vehicle motion control device that calculates a steering angle command value of a wheel and assists the rear wheel in accordance with the command value, a transfer characteristic of a model formula for calculating the two vehicle motion target values is primary / secondary. The following characteristics shall be adopted.Transient characteristics and steady-state characteristics can be adjusted for the transfer characteristics of the model formula of one of the vehicle motion target values, and only the transient characteristics can be adjusted for the transfer characteristics of the model formula of the other vehicle motion target value. By being adjustable, the achievement state of the two different vehicle motions can be controlled.

[0008] The main steering means to be intentionally steered or steered by an occupant, and the auxiliary steering means to be steered or steered by an independent actuator independently of the occupant's intention. Means In the present invention, for the other vehicle motion, for example, a lateral speed or the like that is likely to be adjusted for transient characteristics but does not need to be adjusted so much for steady-state characteristics is set. The yaw rate or the like that is likely to adjust both the steady-state characteristics and the transient characteristics is set.For example, by adjusting each parameter of a model formula for calculating a target value of each vehicle motion, the steady-state characteristics and the transfer characteristics of those transfer characteristics are set. By adjusting the transient characteristics, it becomes possible to finely control the state where two different vehicle motions such as yaw rate and lateral speed are achieved in the actual vehicle. Note that the transfer characteristic of the model equation of the vehicle motion is made primary / secondary because the Laplace transform is performed by expanding the equation of motion of the vehicle in the lateral direction, and the transfer function becomes primary / secondary. This is because, by adjusting these response parameters, various transient characteristics such as steady-state characteristics and vibration, convergence, and gradient of change in a transient state can be adjusted.

Further, the vehicle motion control device according to claim 2 of the present invention includes a steering angle detecting means for detecting a steering angle of a front wheel;
Vehicle speed detecting means for detecting the vehicle speed; and a model formula having at least a primary / secondary transfer characteristic with respect to the front wheel steering angle and adjustable for its steady-state and transient characteristics. First vehicle motion target value calculating means for calculating a first vehicle motion target value for a first vehicle motion set in advance based on the vehicle speed of the vehicle speed detecting means; Is set in advance different from the first vehicle motion based on the steering angle of the steering angle detection means and the vehicle speed of the vehicle speed detection means from a model formula having the transfer characteristics of and having only the transient characteristics adjustable. A second vehicle motion target value calculating means for calculating a second vehicle motion target value for the second vehicle motion, and a first vehicle motion target value calculated by the first vehicle motion target value calculating means. necessary, A first rear wheel steering angle command value calculating means for calculating a first rear wheel steering angle command value of a non-steered rear wheel, and a second vehicle motion target value calculated by the second vehicle motion target value calculating means are achieved. A second rear wheel steering angle command value calculating means for calculating a second rear wheel steering angle command value for the rear wheel,
The rear wheel steering angle is calculated from the sum of the first rear wheel steering angle command value of the first rear wheel steering angle command value calculation means and the second rear wheel steering angle command value of the second rear wheel steering angle command value calculation means. A rear wheel steering angle command value calculating means for calculating a command value, and auxiliary steering means for steering rear wheels according to the rear wheel steering angle command value of the rear wheel steering angle command value calculating means. Is what you do.

The vehicle motion control device according to claim 3 of the present invention is characterized in that the first vehicle motion is a yaw rate and the second vehicle motion is a lateral speed.

The vehicle motion control device according to claim 4 of the present invention calculates respective target values for two different vehicle motions from a predetermined model formula based on the steering angle and the vehicle speed, Calculate the steering angle command value of the rear wheels that are not main-steered so that each vehicle motion simultaneously achieves the two target values,
In the vehicle motion control device adapted to assist the rear wheels in accordance with the above, the transfer characteristics of the model formula for calculating the two vehicle motion target values are set as primary / secondary characteristics, and By correcting the cornering power according to the road surface friction coefficient state and the wheel sideslip angle, the achievement state of the two different vehicle motions can be adapted to the road surface friction coefficient state.

Since the cornering power has the characteristic of decreasing with a decrease in the road surface friction coefficient and a large increase in the side slip angle of the wheels, the present invention provides, for example, a method of calculating the road surface friction coefficient from the slip state of the drive wheels with respect to the non-drive wheels. Detect the condition,
Further, the sideslip angles of the front and rear wheels are detected from the equation of motion of the vehicle, and the cornering power in the model formula used to calculate the target value of the vehicle motion is corrected from the detected values, and the road surface friction coefficient state is corrected. Vehicle motion adapted to the vehicle.

According to a fifth aspect of the present invention, there is provided a vehicle motion control device comprising: a steering angle detecting means for detecting a steering angle of a front wheel;
A vehicle speed detecting means for detecting a vehicle speed and a model formula having at least a primary / secondary transmission characteristic with respect to a front wheel steering angle are set in advance based on the steering angle of the steering angle detecting means and the vehicle speed of the vehicle speed detecting means. First and second vehicle motion target value calculating means for calculating two vehicle motion target values for two different vehicle motions, and two vehicle motions calculated by the first and second vehicle motion target value calculating means A rear wheel steering angle command value calculating means for calculating a rear wheel steering angle command value of a rear wheel that is not main-steered and required to achieve a target value, and a rear wheel steering angle command value of the rear wheel steering angle command value calculating means Auxiliary steering means for steering the rear wheels according to the value, road surface friction coefficient state detecting means for detecting a friction coefficient state of a road surface on which the vehicle is traveling, and wheel side slip angle detecting means for detecting a side slip angle of each of the front and rear wheels. And the road surface friction coefficient state detecting means Based on the wheel side slip angle of the road surface friction coefficient state and the wheel side slip angle detecting means, it is characterized in that a cornering power correcting means for correcting the cornering power in the model equation.

Further, in the vehicle motion control apparatus according to claim 6 of the present invention, the two vehicle motions are a yaw rate and a lateral speed.

[0015]

According to the vehicle motion control apparatus according to the first aspect of the present invention, for example, a yaw rate or the like that is likely to adjust both the steady-state characteristics and the transient characteristics is set for one vehicle motion, Transient characteristics are likely to be adjusted, but lateral speeds or the like that do not need to be adjusted so much are set for the other vehicle motion, for example, each parameter of a model formula for calculating a target value of each vehicle motion By individually adjusting the steady-state and transient characteristics of the transfer characteristics, such as by adjusting the transmission characteristics, it is possible to finely control the state in which two different vehicle motions such as yaw rate and lateral speed are achieved in the actual vehicle. If different vehicles have different transient or steady-state characteristics for different vehicle motions, tuning can be facilitated by adjusting only the part that needs to be changed. That.

According to the vehicle motion control device of the present invention, for example, a yaw rate or the like which is likely to adjust both the steady-state characteristics and the transient characteristics is set in the first vehicle motion, and the transient characteristics are set. Sets the lateral speed, etc., which is likely to be adjusted but does not need to adjust the steady-state characteristics so much, to the second vehicle motion, for example, adjusts each parameter of a model formula for calculating a target value of each vehicle motion By individually adjusting the steady-state and transient characteristics of the transfer characteristics, for example, it is possible to finely control the state where two different vehicle motions such as yaw rate and lateral speed are achieved in the actual vehicle. Therefore, when different transient characteristics or steady-state characteristics are given to different vehicle motions in different vehicles, tuning can be facilitated by adjusting only a portion to be changed.

Further, according to the vehicle motion control apparatus of the present invention, the yaw rate controlling the characteristics of the vehicle at the time of turning and having a high possibility of adjusting both the steady-state characteristics and the transient characteristics is determined by the first vehicle motion control. , And the transient speed is likely to be adjusted, but the lateral speed that does not need to be adjusted so much for the steady-state characteristics is set to the second vehicle motion, so that the tuning of the vehicle dynamics characteristics is further facilitated. .

According to the vehicle motion control device of the present invention, the road surface friction coefficient state and the sideslip angles of the front and rear wheels are detected, and the target value of the vehicle motion is determined from the detected values. By correcting the cornering power in the model formula used for the calculation, the vehicle motion adapted to the road surface friction coefficient state can be achieved.

According to the vehicle motion control device of the present invention, the road surface friction coefficient state and the sideslip angles of the front and rear wheels are detected, and the target value of the vehicle motion is determined from the detected values. By correcting the cornering power in the model formula used for the calculation, the vehicle motion adapted to the road surface friction coefficient state can be achieved.

Further, according to the vehicle motion control device of the present invention, the yaw rate and the lateral speed, which govern the characteristics of the vehicle at the time of turning, are set to the target vehicle motion, so that the vehicle motion can be finer. Vehicle motion can be achieved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a vehicle motion control device of the present invention is applied to a four-wheel steering device for steering rear wheels as auxiliary steering wheels will be described below with reference to the accompanying drawings. The vehicle is a rear-wheel drive vehicle.

First, FIG. 1 briefly shows the overall structure of a four-wheel steering system. In the figure, 10FL and 10FR are left and right front wheels serving as main steering wheels, and 10RL and 10RR are left and right rear wheels serving as auxiliary steering wheels. Of which, front wheel 1
0FL and 10FR are connected by a steering gear device 14 via tie rods 13, respectively. Further, a steering shaft 1 is connected to a steering input source of the steering gear device 14.
Since the steering wheel 15 is rotated, the front wheels 10FL and 10FR can be mechanically mainly steered by rotating the steering wheel 15.

FIG. 2 shows a rear wheel steering device mounted on the vehicle. In the rear wheel steering device 2, the rear wheel 10R
L and 10RR are connected via a tie rod 18 via a steering shaft 20 for rear wheel steering. The actuator unit 1 moves the steering shaft 20 in the left-right direction of the vehicle to assist the rear wheels. It is. The actuator unit 1 constitutes a rear wheel steering device 2 with high efficiency and irreversible characteristics as described later using the electric motor 22 as a power source.

The actuator unit 1 will be briefly described with reference to FIG. 2. The central portion of the steering shaft 20 is housed in a tubular housing 24 so as to be movable in the left-right direction of the vehicle. Steering axis 2
The rack 26 is formed in a part of the “0”. The shaft 29 of the pinion 28 that meshes with the rack 26
The steering shaft 20 projects in the moving direction of the steering shaft 20, that is, in the direction perpendicular to the left-right direction of the vehicle, that is, in the front-rear direction of the vehicle. Further, a hypoid ring gear 30 is coaxially mounted on the pinion shaft 29, and the ring gear 30
A pinion gear 31 that meshes with the electric motor 22 is attached to a rotating shaft 32 of the electric motor 22. Therefore, the electric motor 22
Are rotated from the pinion gear 31 to the ring gear 30,
Since power is transmitted to the pinion 28 and the rack 26, when the electric motor 22 is rotated in both directions, the rack 26,
That is, the steering shaft 20 is reciprocated in the left-right direction of the vehicle, so that the rear wheels 10RL, 10RR, which are auxiliary steering wheels, can be steered in the left-right direction.

The hypoid gear composed of the pinion gear 31 and the ring gear 30 used here exhibits the above-mentioned high efficiency and irreversible characteristics. That is, as shown in FIG. 3, the rotational driving force from the pinion gear 31 can rotate the ring gear 30 in a desired direction because the gear efficiency with the ring gear 30 becomes a positive value (for example, about 40%). Conversely, even if the ring gear 30 is to be rotated, only a force is generated in the axial direction of the pinion gear 31 due to the angle of the teeth, and the gear efficiency is substantially "0" or less, and both the ring gear 30 and the pinion gear 31 rotate. Not done. Therefore, when the cornering force or road surface irregularities acting on the rear wheels 10RL, 10RR are input, the entire area from the pinion gear 31 to the rack 26 is locked, so that it is not possible to change the directions of the rear wheels 10RL, 10RR, that is, the steering angles. Can not.

Incidentally, the reference numeral 9 in FIG.
0 and the rotation angle of the pinion gear 31, the electric motor 22
, That is, the rear wheel steering angle δ _{R of the} rear wheels 10RL and 10RR.
Is a rear wheel steering angle sensor including a rotary potentiometer and the like for detecting the rear wheel steering angle. Similarly, reference numeral 9 'is a rear wheel steering angle sensor including a linear potentiometer and the like for detecting the rear wheel steering angle from the displacement amount of the steering shaft 20. . Among them, in the present embodiment using a wheel steering angle sensor 9 after the former as the main, then used in the wheel steering angle control after below the wheel steering angle [delta] _R. Note that the sub-rear wheel steering angle sensor 9 ′ initializes (initializes) the steering shaft 20 and the rear wheels 10 RL and 10 RR as comparison targets for detecting abnormality of one of the rear wheel steering angle sensors. Used for

Further, the vehicle is provided with a vehicle speed sensor 6 for detecting the front-rear direction speed (vehicle speed) _VSP of the vehicle, and, if necessary, the average front wheel speed n _F and the average rear wheel speed n _{R of} each of the front and rear wheels.
The steering shaft 16 is provided with a steering angle sensor 8 for detecting a steering angle θ of the steering wheel 15. The output signals of the sensors have directionality corresponding to the traveling direction and the turning direction of the vehicle, respectively, but the description is omitted here.

Further, the vehicle includes the rear wheels 10RL, 10RL.
A control unit 3 for controlling the steering angle of the RR is provided. As shown in FIG. 4, the control unit 3 includes an input interface circuit 40a having at least an A / D conversion function, a central processing unit (CPU) 40b, a storage device (ROM, RAM) 40c, and an output having a D / A conversion function. A microcomputer 40 having an interface circuit 40d and the like, a relay drive circuit 41 for outputting a drive current signal _{DF / S} to a relay 51 described later, and a current signal to the electric motor 22 in the switch circuit 4 also described later I _RL, FET _URL provided to adjust the direction of current I _RR, the drive signal D _RL to FET _URL, the FET driving circuit 42 for outputting a D _RR, also the switch circuit 4
FET _LRL , FET _LRR provided to adjust the current value of the current signals I _RL , I _RR to the electric motor 22
A PWM drive circuit 43 for outputting drive signals PWM _RL and PWM _RR to the four FETs _URL , FET _URR and FE
And a switch circuit 4 in which T _LRL and FET _LRR are formed in an H-type bridge.

The switch circuit 4 is connected to the switch circuit 4 as described above.
Four FETs_URL, FET_URR, FET_LRL, FET
_LRRConstitutes an H-type bridge, one end of which is a relay 51.
Connected to battery B via the other end and grounded at the other end.
You. And FET_URLAnd FET_LRRElectric motor between
22 is connected to one terminal of_URRAnd FET_LR
LThe space is connected to the other terminal of the electric motor 22.
Therefore, in this switch circuit 4, the FET_URLAnd FE
T_LRLIs turned on, the motor 22 turns counterclockwise,
The current signal I in the direction of turning the rear wheel to the left_RLFlows, FE
T_URRAnd FET _LRRIs turned on, the electric motor 2
2, the current signal I in the right-hand direction, that is, the direction in which the rear wheels are turned right
_RRFlows (actually FET_LRL, FET_LRRIs PWM
ON / OFF control is performed in a short cycle by the drive signal).
The current signal I_RL, I_RRIs my
It is also taken into the computer 40.

The drive signal D _{F / S} for closing the relay 51 when the fail-safe control signal F / S from the microcomputer 40 has a logical value “0”.
Is supplied to the solenoid of the relay 51, and when the fail-safe control signal F / S has the logical value "1", the relay 5
Open 1. Further, the FET drive circuit 42 is configured to output a corresponding FET _URL or F when one of the FET control signals S _RL and S _RR from the microcomputer 40 has a logical value “1”.
FET drive signals D _RL , D _RR for _turning on one of the ET _URRs are supplied, and when the FET control signals S _RL , S _RR are at logical value “0”, the corresponding FET _URL , FET _URR
Is turned off. Further, the PWM drive circuit 43
Forms a voltage signal of a PWM waveform corresponding to the duty ratio control signals D / T _RL and D / T _RR from the microcomputer 40, and converts them into PWM drive signals PWM _RL and PWM _RR.
To the corresponding FET _LRL , FET _LRR .

FIG. 5 is a functional block diagram of the control unit 3. The control unit 3 constitutes the functional blocks shown in FIG. 5 by performing the arithmetic processing shown in FIG. 8 described later.
That is, in this functional block, the first angle is obtained based on the steering angle θ from the steering angle sensor 8 and the vehicle speed V _SP from the vehicle speed sensor 6.
Vehicle motion target value setting section (first vehicle motion target value calculating means)
Target yaw rate as first vehicle motion target value in BL1１
^{'* And} target yaw angular acceleration ψ ^"*, and a second vehicle movement target value setting unit (second vehicle movement target value calculation means) B
At L2, a target lateral speed _VY ^* and a target lateral acceleration _VY ^'* as a second vehicle motion target value are calculated, and the target yaw rate ψ
^{'* And the} target yaw angular velocity ψ ^"* , the first target rear wheel steering angle δ _R1 ^* as the first rear wheel steering angle command value for independently achieving the target yaw angular velocity ψ ^{" *} The value calculation unit (first rear wheel steering angle command value calculation means) BL3 calculates the target lateral velocity _VY ^* and the target lateral acceleration _VY ^'* independently of the target lateral velocity _VY ^* . 2 The second as the rear wheel steering angle command value
The target rear wheel steering angle δ _R2 ^* is _converted into a second rear wheel steering angle command value calculation unit (second
The rear wheel steering angle command value calculation means (rear wheel steering angle command value calculation means) BL5 calculates the first and second output values of the two calculation sections BL3 and BL4. the second rear wheel steering angle command value δ _R1 ^*, δ _R2 ^* and calculates a target rear wheel steering angle [delta] _R ^* as the rear wheel steering angle command value from a simple sum of, receiving the target rear wheel steering angle [delta] _R ^* in wheel steering angle servo calculating section BL6 after, on the basis of the wheel steering angle [delta] _R after from the rear-wheel steering angle sensor 9, and creating the various control signals to the electric motor 22,
This is output to the rear wheel steering device 2.

The first vehicle motion target value setting section BL1 calculates a first vehicle motion target value for the steering angle θ at that time from an arithmetic expression using a transfer function of the yaw rate with respect to the steering angle as shown in the following equation. The target yaw rate ψ ^{′ *} is calculated (in the equation, both the steering angle θ and the target yaw rate ψ ^{′ *} are expressed as θ (t) and ψ ^{′ *} (t) as functions of time).

[0033] For the derivation principle of this formula, refer to the derived part of the calculation formula for calculating the target yaw rate with respect to the steering angle from the equation of motion of the vehicle described in Japanese Patent Application Laid-Open No. Hei 6-321087 previously proposed by the present applicant. For details on the principle of converting the calculation formula into this one formula, see, for example, "Motion and Control of Automobiles" (Sankaido), pp. 84-94.

G ₁ (V), ζ ₁ (V), ω _n1 (V) and n ₁₁ (V) in the equation are parameters dependent on the vehicle speed.
₁ (V) is the yaw rate gain, ζ ₁ (V) is the yaw rate damping factor (attenuation coefficient), ω _n1 (V) is the natural frequency of the yaw rate, and n ₁₁ (V) is the value corresponding to the zero point of the yaw rate. wherein when one set of morphological transformation, for example, the cornering power and the center of gravity of each wheel before and after - since it is substituted and a vehicle specification and the vehicle speed V _SP such as the distance between axles, the vehicle speed V _SP
Each time, it is set based on a control map previously set and stored in the storage device 40c of the microcomputer 40. Since the transfer function of the target yaw rate ψ ^{′ *} (t) with respect to the steering angle θ has a primary / secondary form, these vehicle speed dependent parameters are, for example, step input of the steering angle θ as shown in FIG. On the other hand, since the yaw rate gain Gψ ′ specifies a steady gain, that is, a steady yaw rate with respect to the steering angle θ, it is also described as a vehicle speed dependent steady characteristic parameter for yaw rate control. Also, the zero equivalent value n
₁₁ (V) specifies the rate of rise of the yaw rate with respect to the change in the steering angle θ, that is, the rise characteristic of the yaw rate.The natural frequency ω _n1 (V) specifies the secondary vibration frequency of the yaw rate after the rise. Since the damping coefficient ζ ₁ (V) specifies the speed of the convergence of the vibration, that is, the convergence of the yaw rate, these are also collectively described as a vehicle speed-dependent transient characteristic parameter for yaw rate control. Therefore, by setting these vehicle speed-dependent parameters in accordance with the vehicle speed V _SP , the transfer characteristics of the target yaw rate ^{* ′ *} become different transfer characteristics in accordance with the vehicle speed V _SP , and by changing each parameter individually, For example, it is possible to obtain a transfer characteristic that differs only in the steady gain, that is, only in the steady characteristic, or only in the vibration frequency, that is, only in the transient characteristic.

However, a first rear wheel steering angle command value calculation unit, which will be described later,
In BL3, the first target rear wheel steering angle δ_R1 ^*When calculating
Target yaw angular accelerationψ^"*It is necessary to use
1 vehicle motion target value setting unit BL1 is a block diagram of FIG.
And the target yaw angular velocity ψ^"*Was calculated
Later, this is integrated and the target yaw rate ψ^'*Calculate
Like that. The gain B in each block diagram₀₁,
B₁₁, F₁₁, F₀₁Is a value calculated based on the following equation.

[0036] _{B 01 = ω n1 (V)} 2 ......... (1-1) B 11 = 2ζ 1 (V) · ω n1 (V) ......... (1-2) F 11 = n 11 (V) ^{_{· ω n1 (V) 2 .........}} (1-3) F 01 = ω n1 (V) 2 -B 11 · F 11 ......... (1-4) Further, the second vehicle motion target value setting unit BL2 Then, a target lateral speed V _Y ^* as a second vehicle motion target value with respect to the steering angle θ at that time is calculated from an arithmetic expression using a transfer function of the lateral speed with respect to the steering angle shown in the following two equations (wherein Then, both the steering angle θ and the target lateral velocity V _Y ^*
(t) and V _Y ^* (t)).

[0037] For the principle of deriving these two equations, refer to the above-mentioned prior arts and references. Also, G ₂ (V), 式
₂ (V), ω _n2 (V) and n ₀₂ (V) are parameters depending on the vehicle speed, G ₁ (V) is the lateral speed gain, and ζ ₁ (V) is the lateral speed damping factor (damping coefficient). , Ω _n1 (V) is the natural frequency of the lateral velocity, and n ₁₁ (V) is the value corresponding to the zero point of the lateral velocity. since it was replaced and a vehicle specifications such as the distance between the axle and the vehicle speed V _SP, the vehicle speed V _SP
Each time, it is set based on a control map previously set and stored in the storage device 40c of the microcomputer 40. The transfer function of the target lateral speed _VY ^* (t) with respect to the steering angle?
Since it has a quadratic form, the lateral speed gain Gψ ′ specifies a stationary lateral speed, and is also described as a vehicle speed-dependent stationary characteristic parameter for lateral speed control. The zero-equivalent value n ₀₂ (V) specifies the rise characteristic of the lateral velocity with respect to the change in the steering angle θ, and the natural frequency ω _n1 (V) specifies the secondary vibration frequency of the lateral velocity after the rise. Since the damping coefficient ζ ₁ (V) specifies the convergence of the lateral speed, these are also collectively referred to as vehicle speed-dependent transient characteristic parameters for lateral speed control. Again, by setting these vehicle speed dependent parameters according to the vehicle speed _VSP , the transfer characteristics of the target lateral speed _VY ^* will be different according to the vehicle speed _VSP , and each parameter must be changed individually. by, for example, the steady state gain only, i.e. steady characteristic only, or vibration frequency only, i.e. only the transient characteristics is also possible to obtain different transfer characteristics, in this embodiment, steady-state characteristics of the lateral velocity V _Y or change Since there is no need to make adjustments, the value is set to a value equivalent to that of a two-wheel steering vehicle that does not steer the rear wheels.

Further, a second rear wheel steering angle command value calculation unit, which will be described later,
In BL4, the second target rear wheel steering angle δ_R2 ^*When calculating
Target lateral acceleration V_Y ^'*It is necessary to use
The vehicle motion target value setting unit BL2 is represented by a block diagram in FIG. 7B.
And the target lateral acceleration V_Y ^'*After calculating
This is integrated and the target lateral velocity V_Y ^*To calculate
doing. The gain B in each block diagram₀₂, B₁₂,
F₁₂, F₀₂Is a value calculated based on the following equation.

B ₀₂ = ω _n2 (V) ² ... (2-1) B ₁₂ = 2V ₂ (V) · ω _n2 (V)... (2-2) F ₁₂ = ω _n2 (V) ² (2-3) F ₀₂ = n ₀₂ (V) · ω _n2 (V) ² −B ₁₂ · F ₁₂ (2-4) Further, the first rear wheel steering angle command value calculation In the section BL3, the target yaw rate ψ ^'* and the target yaw angular acceleration ψ ^"* from the first rear wheel steering angle command value calculation section BL1 and the steering angle sensor 8
Based on the steering angle θ from the vehicle and the vehicle speed V _SP from the vehicle speed sensor 6, the actual yaw rate ^{* ′ *} is calculated based on the following three equations by the inverse calculation of the well-known two-degree-of-freedom vehicle motion equation. A rear wheel steering angle capable of matching the yaw rate is calculated, and this is used as a first rear wheel steering angle command value as a first target rear wheel steering angle δ _R1 ^*.
And

Δ _R1 ^* = β _R + (V _Y −L _R ψ ^{′ *} ) / V _SP (3) β _R = C _R / K _R (3-1) C _R = (L _F · _CF− I _Z · ψ ^“* / 2) / L _R (3-2) C _F = eK _F · β _F (3-3) β _F = θ / N− (V _Y + L ^{_{F · ψ '*) / V}} SP ...... (3-4) V Y = (2C F + 2C R) / M-V SP · ψ' * ...... (3-5) in the formula, V _Y is the lateral Speed, β _F is the front wheel sideslip angle, β _R
The rear wheel side slip angle, L _F is the distance from the front axle to vehicle center of gravity, L _R is the distance from the rear axle to the vehicle center of gravity, C _F is the front wheel cornering force, C _R is the rear wheel cornering force, K _R is the cornering power of the rear wheel of the vehicle, e
K _F is the equivalent cornering power of the front wheels of the vehicle (the cornering power of the front wheels, but also a value that takes into account the decrease in the cornering power with respect to the steering angle due to the influence of the steering stiffness), I _Z is the yaw moment of inertia of the vehicle,
M represents the mass of the vehicle, and N represents the steering gear ratio. Incidentally, here the target yaw rate [psi ^'*, which is the calculated to the yaw rate, the yaw angular acceleration using the calculated target yaw angle acceleration [psi ^"*, do not assist steering the rear wheel in the transverse speed V _Y two-wheeled Use the same value as the steered vehicle.

The second rear wheel steering angle command value calculation unit BL
4, the second rear wheel steering angle command value calculation unit BL2
Lateral speed V_Y ^*And target lateral acceleration V_Y ^'*And the steering angle
The steering angle θ from the sensor 8 and the vehicle speed V from the vehicle speed sensor 6
_SPBased on the following four formulas based on
By the inverse calculation of both equations of motion, the target lateral velocity V_Y ^*
Then, calculate the rear wheel steering angle that can match the actual lateral speed,
To the second target rear wheel steering angle δ as a second rear wheel steering angle command value._R2
^*And

[0042] ^{_{δ R2 * = β R + (}} V Y * -L R · ψ ') / V SP ......... (4) β R = C R / K R ...... (4-1) C R = (L _{F · C F -I Z · ψ} "/ 2) / L R ...... (4-2) C F = eK F · β F ...... (4-3) β F = θ / N- (V Y * + L _F · ψ ^′ ) / V _SP (4-4) V _Y = ∫V _Y ^'* (t) dt (4-5) Here, the lateral velocity is the target lateral velocity V calculated above.
_Y ^* and the calculated lateral acceleration V _Y
^{Use '*'} and use the same values for yaw rate and yaw angular acceleration as for a two-wheel steered vehicle that does not assist the rear wheels.

The rear wheel steering angle command value calculation section BL5
Then, the first target rear wheel steering angle δ_R1 ^*And the second target rear wheel steering angle
δ_R2 ^*And the target rear wheel steering angle as the rear wheel steering angle command value from the sum of
δ_R ^*Is calculated by the rear wheel steering angle servo calculator BL6.
Is the target rear wheel steering angle δ_R ^*And the rear wheel steering angle sensor 6
Rear wheel steering angle δ_ROf the electric motor 22 based on the deviation from
Motor operation amount S consisting of rotation direction and rotation angle (rotation amount)
TP is set, and accordingly, any of the H-type bridges is set.
Close the circuit and turn the electric motor 22 for several steps during that time.
Control signal S depending on whether_RL, S_RR, D / T_RL, D
/ T_RRIs generated and output.

Next, the arithmetic processing executed by the microcomputer 40 of the control unit 3 to construct the functional blocks will be described with reference to the flowchart of FIG. This arithmetic processing is performed for a predetermined sampling time Δ
This is executed as a timer interrupt process for each T (for example, 10 msec.). In this arithmetic processing, no step for communication is provided. However, programs and maps stored in the ROM of the storage device 40c and various data stored in the RAM are always stored in the arithmetic processing device 40b. Each calculation result transmitted to a buffer or the like and calculated by the arithmetic processing device 40b is also stored in the storage device 40c as needed.

In this calculation processing, first, in step S1
And the vehicle speed V from the vehicle speed sensor 6_SPAnd the steering angle
Steering angle θ from the sensor 8 and rear wheels from the rear wheel steering angle sensor 9
Steering angle δ _RRead.

Next, the process proceeds to step S5 to perform individual arithmetic processing, whereby the vehicle speed-dependent steady-state characteristic parameter G ₁ (for yaw rate control) is obtained according to the control map and the like stored in the storage device 40c as described above. V) and their transient characteristic parameters ζ ₁ (V), ω _n1 (V), and n ₁₁ (V) are calculated and set, respectively.

Next, the process proceeds to step S6, where individual arithmetic processing is performed, and according to the control map and the like stored in the storage device 40c, the vehicle speed dependent steady-state characteristic parameters G ₂ (V) and The transient characteristic parameter ζ
₂ (V), ω _n2 (V), and n ₀₂ (V) are calculated and set, respectively.

Next, the routine proceeds to step S7, where the target yaw rate ψ ^{′ *} is calculated according to the above equation (1). Next, step S
8, the target lateral speed V _Y ^* is calculated according to the above two equations.

Next, the process proceeds to step S9, where the first target rear wheel steering angle δ _R1 ^* is calculated according to the above three equations by performing individual detailed arithmetic processing. At the next step S10, by performing the individual fine processing, to calculate a second target rear wheel steering angle [delta] _R2 ^* in accordance with the 4 expression.

Next, the flow shifts to step S11, where the first
Calculating a target rear wheel steering angle [delta] _R ^* from the sum of the target rear wheel steering angle [delta] _R1 ^* and the second target rear wheel steering angle [delta] _R2 ^*. Next, step S
The process proceeds to 12, by performing the individual processing to calculate the motor operation amount STP for match (servo) of the rear wheel steering angle [delta] _R to the target rear-wheel steering angle [delta] _R ^*.

Next, the process proceeds to step S13, where the control signals S _RL , S _RR , D / T _RL , and D / T _RR for achieving the motor operation amount STP are obtained by performing individual arithmetic processing. After creating and outputting, return to the main program.

Next, the operation of the arithmetic processing of FIG. 8 will be described. In this calculation process, the calculation processing in step S5 after, the target yaw rate [psi ^'* after the first goal to achieve wheel steering angle [delta] _R1 ^*, after the second goal to achieve the target lateral velocity V _Y ^* The wheel steering angles δ _R2 ^* are individually calculated, and the added value thereof is used as the final target rear wheel steering angle δ _R ^* . As described above, during operation of the process, the yaw rate when calculating the or using a flat rate when calculating the first target rear wheel steering angle [delta] _R1 ^*, second target rear wheel steering angle [delta] _R2 ^* Although they intervene with each other, for example, by using the same thing as that of a two-wheel steering vehicle with no rear wheel steering, for example, the first target rear wheel steering The angle δ _R1 ^* may achieve only the target yaw rate ψ ^{′ *} , and the second target rear wheel steering angle δ _R2 ^* may achieve only the target lateral velocity V _Y ^*. You can.

[0053] Then, the target rear wheel steering angle comprising a first target rear wheel steering angle [delta] _R1 ^* and the sum of the second target rear wheel steering angle [delta] _R2 ^* [delta] _R
Considering ^* , at least the first target rear wheel steering angle δ
_The steady-state target yaw rate ψ ^'* achieved by _R1 ^* , that is, the steady-state characteristic of the yaw rate is determined by, for example, the vehicle speed-dependent steady-state characteristic parameter G ₁ (V) for yaw rate control, and the second target rear wheel steering angle δ _R2 ^* The steady state target lateral speed _VY ^* to be achieved, that is, the steady-state characteristic of the lateral speed is also determined by, for example, the vehicle speed-dependent steady-state characteristic parameter G ₂ (V) for lateral speed control. In addition, since the steady state of the lateral speed for finely adjusting the vehicle motion characteristics at the time of turning does not need to be changed so much as described above, regardless of whether or not the rear wheel is assisted, the lateral speed control is not required. The vehicle speed dependent steady characteristic parameter G ₂ (V) is set to be equal to that of a two-wheel steering vehicle. That is, if the vehicle speed-dependent steady-state characteristic parameter G ₁ (V) for yaw rate control is appropriately set for each vehicle speed V _SP , the steady-state characteristics of the yaw rate and the lateral speed achieved by the target rear wheel steering angle δ _R ^* are unique. And at least tuning in this state is very clear and simple.

The target yaw rate ψ ^{′ *} in the transient state, that is, the transient characteristic of the yaw rate is, for example, the vehicle speed dependent transient characteristic parameter ζ ₁ (V), ω _n1 (V), n for the yaw rate control.
₁₁ (V), the target lateral velocity V _Y ^* in the transient state,
In other words, the transient characteristics of the lateral speed also include, for example, the vehicle speed-dependent transient characteristic parameters ζ ₂ (V), ω _n2 (V), and n ₀₂ (V) for the lateral speed control.
The rules, yet each parameter, respectively, since it is the one used for adjusting the what transient characteristics of the yaw rate and lateral velocity are determined, each parameter for each vehicle speed V _SP in response to transient characteristics desired With proper settings, the transient characteristics achieved are also determined accordingly. That is, by appropriately adjusting these parameters, transient characteristic of the yaw rate and lateral velocity is achieved by the target rear wheel steering angle [delta] _R ^* is also uniquely determined, since it becomes easy tuning this state, the vehicle This makes it relatively easy to respond to different requests.

FIG. 9 shows a simulation of this tuning.
I tried it. This simulation shows a stable high μ
This assumes a turn from a straight road on a road surface. Ma
Instead, assuming a step input of the steering angle θ as shown in FIG.
You. Then, the ideal that secondary vibration converges relatively early
Target yaw rateψ^'*Is determined as in FIG. 9b.
In other words, this target yaw rate ψ^'*Control waveform
It is the vehicle speed dependent steady-state characteristic parameter for yaw rate control.
Meter G₁(V) and its transient characteristics parameter ζ₁(V), ω
_n1(V), n₁₁(V). This target yaw rate ψ^'*only
The so-called first target rear wheel steering angle δ_R1 ^*Figure 9d
Is shown by a solid line. Then, the first target rear wheel steering angle δ _R1 ^*But
The yaw rate gain when achieved is shown in FIG.
FIG. 9F shows the gain of the lateral acceleration, which is the derivative of the degree, in the yaw rate.
9g and the lateral acceleration phase in FIG. 9h, respectively.
Show. Yaw rate excluding gain of lateral acceleration
The gain and phase of the vehicle and the phase of the lateral acceleration are
Although it is almost ideal as a motion characteristic,
Is slightly lower in the high frequency region of, for example, 1 Hz or more
As a result, the rise of the lateral acceleration was weak.

Therefore, the vehicle speed dependent steady-state characteristic parameter G ₂ (V) for the lateral speed control and its transient characteristic parameter ζ
While appropriately adjusting ₂ (V), ω _n2 (V), and n ₀₂ (V), the target lateral acceleration V _Y ^'* with respect to the steering angle θ is set as shown in FIG. 9C. As can be seen from the figure, the target lateral acceleration V _Y ^'* is an ideal one in which the rise is sharp and fast, and the secondary vibration converges relatively early. Since the steady gain is relatively large like a vehicle, the vehicle also has a sporty feeling. The second target rear wheel steering angle δ for achieving the target lateral acceleration V _Y ^{′ *}
_R2 ^* is calculated, indicating the first target rear wheel steering angle [delta] _R1 ^* and the addition to the target rear wheel steering angle obtained by [delta] _R ^* by a broken line in FIG 9d. According to this, the timing of starting the turning of the rear wheel steering angle is slightly delayed, and the turning is sharply and quickly increased. The gain of the yaw rate, the gain of the lateral acceleration, the phase of the yaw rate, and the phase of the lateral acceleration at this time are indicated by broken lines in the corresponding drawings. As is apparent from these figures, the ideal motion characteristics achieved at the first target rear wheel steering angle δ _R1 ^* for achieving only the target yaw rate ψ ^{′ *} , that is, the gain and phase of the yaw rate and the lateral acceleration The phase hardly changed, and the gain of the lateral acceleration in the high frequency region, which was slightly lacking, increased, and all vehicle motion characteristics were almost satisfied.

As described above, the present embodiment is an embodiment of the vehicle motion control apparatus according to claims 1 to 3 of the present invention, and the steering angle sensor 8 and step S1 of the calculation processing in FIG. Similarly, the vehicle speed sensor 6 and step S1 of the calculation processing in FIG. 8 constitute vehicle speed detection means, and steps S5 and S7 of the calculation processing in FIG. Steps S6 and S8 of the calculation process of FIG. 8 constitute a second vehicle motion target value calculation unit, and Step S9 of the calculation process of FIG. 8 constitutes a first rear wheel steering angle command value calculation unit. Figure 8
8 constitutes a second rear wheel steering angle command value calculation means, step S11 of the calculation processing of FIG. 8 constitutes rear wheel steering angle command value calculation means, and step S12 of the calculation processing of FIG. Step S13 and the rear wheel steering device constitute auxiliary steering means.

Next, a second embodiment of the vehicle motion control device according to the present invention will be described with reference to FIGS. The main configuration of the vehicle in this embodiment is the same as that in FIGS. 1 to 3 of the first embodiment. The main control after the calculation of the target value of the vehicle motion is the same as that shown in FIGS. 4, 5 and 7 of the first embodiment, and the explanation of various parameters and the like used therefor is also given. , The first
It is the same as that shown in FIG. 6 of the embodiment. On the other hand, the arithmetic processing executed by the microcomputer 40 in the control unit 3 is changed from that of FIG. 8 to that of FIG. However, the calculation processing of FIG.
Is similar to the arithmetic processing described above, and some of the steps are equivalent. Therefore, the same reference numerals are given to the same steps, and the detailed description thereof will be omitted. Then, when listing differences between the arithmetic processing of FIG. 7 and the arithmetic processing of FIG. 10, first, steps S2 to S4 are inserted between step S1 and step S5. In addition, even if the calculation formulas and the like used in the arithmetic processing are equivalent, step S9 and step S9
In 10, there is a change in the content such that the parameters used for the calculation are specifically changed.

More specifically, in step S2, the average front wheel speed n _F and the average rear wheel speed n _R of the front and rear wheels are read, and the process proceeds to step S3. In this step S3, individual calculation processing (not shown) is performed. For example, after calculating the road surface μ from the front and rear wheel speed ratio n _F / n _R during acceleration, step S
Move to 4. That is, the lower the road surface mu, the average rear wheel speed n _R during acceleration of the rear wheels is a drive wheel, faster than the average front wheel speed n _F is a vehicle speed equivalent to the non-driving wheels,
Since the ratio between the two is almost as low as the road surface μ, it can be used to detect the approximate road surface μ. In addition, for the detection of the road surface μ, for example, in a vehicle provided with an ABS (anti-lock brake control device),
The ratio of the road surface reaction torque may be obtained from the return speed (acceleration) of each wheel speed during the process of reducing the working fluid pressure to the wheel cylinder by the BS, and the ratio may be used as the road surface μ. Also,
Switching between the two may be performed by using a signal such as a throttle opening ON or a brake switch ON as a trigger.

In step S4, the road surface μ
And front and rear wheel sideslip angle β_F, Β_RFrom, to individual arithmetic processing
For example, according to the control map of FIG.
Cornering power K_F, K_RAfter calculating
The process proceeds to Step S5. About the control map of FIG.
Is the side slip angle β of the front and rear wheels_F, Β _R
For step S9 or step
In S10, the above formulas 3-1 to 3-5 or 4-
What is calculated by Equations 1 to 4-5 may be used.

Then, step S5 or step S6 is performed.
Now, the corners of the front and rear wheels calculated in step S4
Ring power K_F, K_RTarget yaw rate using^'*And
Target lateral speed V_Y ^*Is calculated.
Existing cornering power K _F, K_RBy correcting
Possible. See the reference above for details). Ma
In step S9 and step S10, the step
Cornering power K of front and rear wheels calculated in step S4
_F, K_RBy solving the above equations 3 and 4 using
Rear wheel steering angle δ_R1 ^*, Δ_R1 ^*Is calculated.

Next, the operation of the present embodiment will be described.
You. Cornering power K for front and rear wheels _F, K_RIs stable
The operation after step S5 when
Similar to the first embodiment, but in this embodiment, an additional
In steps S2 to S4, the cornering
Work K_F, K_RHas been reset (corrected).
Generally, the product of cornering power and wheel sideslip angle
The appearing cornering force has a small wheel skid angle
Increases linearly with the increase in the sideslip angle.
Second, the rate of increase decreases, and the wheel sideslip angle exceeds a certain
When becomes large, it starts to decrease. Formula 3-1 or
As is clear from the definition of Formula 4-1, this cornering
The rate of increase or decrease in gforce is the cornering power
And shows the change with respect to the sideslip angle on high μ road surface.
Then, it becomes as shown in FIG. In other words, cornering power
May be negative above a certain skid angle.
You.

The cornering force is a part of the grip force of the tire, and the grip force of the tire may be considered to be almost the frictional force with the road surface. Is smaller and the cornering force is smaller, so that the cornering power on the high μ road surface is as shown in FIG. 11 on the low μ road surface. Therefore, in this embodiment,
Accurate vehicle motion by using the road surface μ and the wheel sideslip angles β _F , β _R that fluctuate the cornering power, and correcting the current cornering powers K _F , K _R to an accurate value accordingly. To be able to

Here, differences in vehicle motion due to differences in road surface μ will be compared with those in the first embodiment. First, for example, the yaw rate of a rear-wheel-drive vehicle that is not rear-wheel steered, that is, a normal FR two-wheel-steered vehicle on a high μ road surface is shown by a solid line in FIG.
On the other hand, in the first embodiment and the second embodiment in which the rear wheels are assisted, for example, the rising speed of the yaw rate is improved to improve the turning performance, and the convergence of the secondary vibration is accelerated. Further, in order to make the gain in the steady state smaller and approach the neutral steer, a target response characteristic as shown in FIG. As shown in FIG. 12b, the target response characteristic of the steady-state characteristic (steady-state value) is made to match that of the rear-wheel unsteered vehicle as described above, and the rise of the lateral speed is rapidly increased for the transient characteristic, as shown in FIG. And the setting is made to enhance the convergence of the secondary vibration. FIG. 13 shows the change over time of the rear wheel steering angle satisfying these characteristics.

However, in the first embodiment, since the cornering power is not set according to the road surface μ, for example, the target response characteristic of the low μ road surface is given in the same manner as that of the high μ road surface as shown by the broken line in FIG. Similarly, the target response characteristic of the lateral speed is given in the same manner as that of the high μ road surface as shown by the broken line in FIG. On the other hand, the actually achievable yaw rate for a rear-wheel unsteered vehicle appears as shown by the solid line in FIG. 12c, and the achievable lateral speed only appears as shown by the solid line in FIG. 12d. In other words, the target response characteristic that is the same as the high μ road surface is too large for the vehicle motion such as the yaw rate and the lateral speed that can be actually achieved by the two-wheel steering vehicle, and the target response characteristic that is actually the same as the high μ road surface If the rear wheels are assisted by steering, the characteristics of the two-wheel steering vehicle can be slightly improved as shown by the dashed line in FIG. 12c.

Therefore, for example, on a low μ road surface, the lateral speed (vehicle side slip angle) increases because it is inevitable in terms of maneuverability and acceleration. It is only necessary to slightly accelerate the rise to obtain a turning property, and as a steady characteristic after suppressing the secondary vibration, it is better to lower the gain and increase the stability. This is shown by a two-dot chain line in FIG. I showed it. In addition, the lateral speed may be started up a little earlier in order to call attention to the driver, and thereafter, it may be stabilized at a gain equivalent to that of the rear-wheel non-steered vehicle so that the vehicle does not vibrate as much as possible. I showed it with a two-dot chain line. That is,
As is clear from this description, the desired target response characteristics on the low μ road surface may be the same as those on the high μ road surface in terms of the directionality given to each parameter, and simply include the cornering power included in them. Is the road surface μ
It can be seen that if the correction is made according to the formula (1), the value is appropriately given. By correcting the target response characteristics in this manner, a desired rear wheel steering angle on a low μ road surface is automatically obtained as shown by a two-dot chain line in FIG.

That is, by setting the target value (including the transient characteristics and the steady-state characteristics) of the vehicle motion while appropriately correcting the cornering power, it is possible to use a common response from the linear region to the limit region of the cornering force. For example, from the steer characteristic control corresponding to the linear range, through the braking / driving control where the cornering force reaches a plateau, to the load (roll stiffness) control corresponding to the limit range, the stability and the response of The effect is automatically maximized.

In this embodiment, if the cornering power, the sideslip angle, and the road surface μ are all unknown, the vehicle motion equation described above cannot be solved. Initialize cornering power on μ road surface (calibration)
Then, for example, when the judgment of the low μ road surface is advanced, the cornering power is first corrected based on that, and when the steering input is made, the front wheel side slip angle is corrected, and the correction of the three is sequentially updated and stored repeatedly. By doing so, both are brought close to the true value.

As described above, the present embodiment is an embodiment of the vehicle motion control apparatus according to claims 1 to 6 of the present invention, and the steering angle sensor 8 and the step S1 of the arithmetic processing in FIG. The vehicle speed sensor 6 and step S1 of the calculation processing of FIG. 10 similarly constitute the vehicle speed detection means, and step S5 of the calculation processing of FIG.
And step S7 constitute a first vehicle movement target value calculating means, and steps S6 and S8 of the calculation processing in FIG.
Constitutes a second vehicle movement target value calculating means, step S9 of the arithmetic processing of FIG. 10 constitutes a first rear wheel steering angle command value calculating means, and step S10 of the arithmetic processing of FIG. Step S11 of the calculation processing in FIG. 10 constitutes a rear wheel steering angle command value calculation means, and steps S12 and S13 of the calculation processing in FIG. 10 and the rear wheel steering device constitute auxiliary steering means. 10, the step S3 of the calculation processing of FIG. 10 constitutes the road surface friction coefficient state detecting means, and the step S9 or S10 of the calculation processing of FIG. 10 constitutes the wheel side slip angle detection means, and the calculation processing of FIG. Step S4 constitutes the cornering power correction means.

In the above embodiment, the steering angle of the front wheels is calculated from the steering angle of the steering wheel. However, since what is substantially desired is the front wheel steering angle δ _F (= θ / N),
This may be detected directly.

Further, in the above-described embodiment, a case has been described where each vehicle speed-dependent parameter for determining a transfer characteristic is set based on a control map set in advance. However, the present invention is not limited to this. In addition, it is also possible to set by performing a function operation based on the vehicle speed. In short, any method can be used as long as the vehicle speed-dependent parameter can be uniquely set for the vehicle speed.

Further, in the above-described embodiment, the case where each vehicle speed dependent parameter is set according to the vehicle speed has been described. However, the present invention is not limited to this. For example, the vehicle travels at high speed based on the selected gear ratio. It is also possible to estimate the running speed of the vehicle, such as whether the vehicle is running or running at low speed, and set the vehicle speed-dependent parameter based on this.

Each of these parameters can be adjusted not only by the vehicle speed but also by the driving state and steering state of the difference. In the above-described embodiment, the case where a microcomputer is applied as the control unit 3 has been described. Alternatively, an electronic circuit such as a counter and a comparator may be combined.

[Brief description of the drawings]

FIG. 1 shows an example of a rear wheel steerable vehicle in which a vehicle motion control device of the present invention is developed, wherein (a) is a schematic diagram of the entire vehicle configuration, and (b) is a schematic configuration diagram of an actuator.

FIG. 2 is a detailed explanatory view of the actuator of FIG. 1;

FIG. 3 is an explanatory diagram of irreversible characteristics of the actuator of FIG. 2;

FIG. 4 is an explanatory diagram of a configuration of a control unit in FIG. 1;

FIG. 5 is a functional block diagram constructed by the control unit of FIG. 4;

FIG. 6 is an explanatory diagram of each parameter used in the block diagram of FIG. 5;

FIG. 7 is an explanatory diagram showing each internal block of the block in FIG. 5;

FIG. 8 is a flowchart illustrating a first embodiment of a calculation process executed by the control unit in FIG. 4;

FIG. 9 is an operation explanatory diagram of the calculation processing of FIG. 8;

FIG. 10 is a flowchart illustrating a second embodiment of the arithmetic processing executed by the control unit in FIG. 4;

FIG. 11 is a control map used for the calculation processing of FIG. 10;

FIG. 12 is an operation explanatory diagram of the calculation processing of FIG. 10;

FIG. 13 is an operation explanatory diagram of the calculation processing of FIG. 10;

FIG. 14 is an operation explanatory diagram of the calculation processing of FIG. 10;

[Explanation of symbols]

 1 is an actuator unit 2 is a rear wheel steering device 3 is a control unit 4 is a switch circuit 6 is a vehicle speed sensor 8 is a steering angle sensor 9 is a rear wheel steering angle sensor 10 FL to 10 RR is a front left wheel to a rear right wheel 15 is a steering wheel 20 The steering shaft 22 is an electric motor 40 is a microcomputer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takaaki Eguchi 2 Nissan Motor Co., Ltd., Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (6)

[Claims] 1. A method according to claim 1, further comprising: calculating, based on a steering angle and a vehicle speed, respective target values for two different vehicle motions from a predetermined model formula, so that each vehicle motion simultaneously achieves the two target values. , Calculate the steering angle command value of the rear wheels that are not main-steered,
In the vehicle motion control device adapted to assist steering of the rear wheels in response to this, the transfer characteristics of the model formula for calculating the two vehicle motion target values are set as primary / secondary characteristics, and either one of them is used. For the transfer characteristic of the model expression of the vehicle motion target value, the transient characteristic and the steady characteristic can be adjusted, and for the transfer characteristic of the model expression of the other vehicle motion target value, only the transient characteristic can be adjusted. A vehicle motion control device, wherein different vehicle motion achievement states can be controlled. 2. A steering angle detecting means for detecting a steering angle of a front wheel;
Vehicle speed detecting means for detecting the vehicle speed; and a model formula having at least a primary / secondary transfer characteristic with respect to the front wheel steering angle and adjustable for its steady-state and transient characteristics. First vehicle motion target value calculating means for calculating a first vehicle motion target value for a first vehicle motion set in advance based on the vehicle speed of the vehicle speed detecting means; Is set in advance different from the first vehicle motion based on the steering angle of the steering angle detection means and the vehicle speed of the vehicle speed detection means from a model formula having the transfer characteristics of and having only the transient characteristics adjustable. A second vehicle movement target value calculating means for calculating a second vehicle movement target value for the second vehicle movement, and a first vehicle movement target value calculated by the first vehicle movement target value calculating means. necessary, A first rear wheel steering angle command value calculating means for calculating a first rear wheel steering angle command value of a non-steered rear wheel, and a second vehicle motion target value calculated by the second vehicle motion target value calculating means are achieved. A second rear wheel steering angle command value calculating means for calculating a second rear wheel steering angle command value for the rear wheel,
The rear wheel steering angle is calculated from the sum of the first rear wheel steering angle command value of the first rear wheel steering angle command value calculation means and the second rear wheel steering angle command value of the second rear wheel steering angle command value calculation means. A rear wheel steering angle command value calculating means for calculating a command value, and auxiliary steering means for steering rear wheels according to the rear wheel steering angle command value of the rear wheel steering angle command value calculating means. Vehicle motion control device. 3. The vehicle motion control device according to claim 2, wherein the first vehicle motion is a yaw rate, and the second vehicle motion is a lateral speed. 4. Based on a steering angle and a vehicle speed, respective target values for two different vehicle motions are calculated from a predetermined model formula so that each vehicle motion simultaneously achieves the two target values. , Calculate the steering angle command value of the rear wheels that are not main-steered,
In the vehicle motion control device adapted to assist the rear wheels in accordance with the above, the transfer characteristics of the model formula for calculating the two vehicle motion target values are set as primary / secondary characteristics, and A vehicle motion control device characterized in that the two different vehicle motion achievement states can be adapted to the road surface friction coefficient state by correcting the cornering power according to the road surface friction coefficient state and the wheel side slip angle. 5. A steering angle detecting means for detecting a steering angle of a front wheel,
A vehicle speed detecting means for detecting a vehicle speed and a model formula having at least a primary / secondary transmission characteristic with respect to a front wheel steering angle are set in advance based on the steering angle of the steering angle detecting means and the vehicle speed of the vehicle speed detecting means. First and second vehicle motion target value calculating means for calculating two vehicle motion target values for two different vehicle motions, and two vehicle motions calculated by the first and second vehicle motion target value calculating means A rear wheel steering angle command value calculating means for calculating a rear wheel steering angle command value of a rear wheel that is not main-steered and required to achieve a target value, and a rear wheel steering angle command value of the rear wheel steering angle command value calculating means Auxiliary steering means for steering the rear wheels according to the value, road surface friction coefficient state detecting means for detecting a friction coefficient state of a road surface on which the vehicle is traveling, and wheel side slip angle detecting means for detecting a side slip angle of each of the front and rear wheels. And the road surface friction coefficient state detecting means On the basis on the wheel side slip angle of the road surface friction coefficient state and the wheel side slip angle detecting means, a vehicle motion control apparatus being characterized in that a cornering power correcting means for correcting the cornering power in the model equation. 6. The vehicle motion control device according to claim 5, wherein the two vehicle motions are a yaw rate and a lateral speed.