JPH054268B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vehicle steering system control device that can freely control the motion performance of a vehicle during steering, and particularly relates to steady turning motion characteristics and transient motion characteristics. The present invention relates to a vehicle steering system control device that controls both motion characteristics and ensures safety in the event of failure.

(Prior art) Vehicles equipped with conventional mechanical link steering devices are configured to steer the front wheels in response to the amount of steering from the steering wheel, and the dynamic performance associated with steering depends on the vehicle's vehicle performance. The driving performance is determined uniformly based on specifications, and is unique to each vehicle type.

On the other hand, the applicant of this application previously filed a patent application filed in
No. 147018, Patent Application No. 188153, Patent Application No. 1881-
In No. 188158, etc., a target vehicle with target dynamic performance is assumed, and based on the vehicle specifications and equation of motion regarding the target vehicle, the target value of the motion variable corresponding to the steering wheel steering amount and vehicle speed, that is, the target vehicle The steering angle of the vehicle's wheels (at least one of the front wheels or rear wheels) is determined so that the vehicle (vehicle equipped with the device) achieves the motion variable target value representing the motion performance exhibited by the vehicle. We are proposing a device to control this.

In other words, if you use this device, for example, even if your vehicle is a sedan type vehicle, if you set the target vehicle to be a sports car type vehicle, you can achieve the driving performance of a sports car even though the body structure etc. is of the sedan type. It is possible to freely control exercise performance, such as by making the body possess the following characteristics.

(Problems to be Solved by the Invention) By the way, the inventor of the present application has the following problems regarding the above device:
Through further research, we discovered the following improvements.

In other words, although the above device can freely control the steering characteristics of the vehicle both during steady turning motion and during transient motion, it is possible to freely control the steering characteristics of the vehicle during both steady turning motion and transient motion. The system aims to achieve the target driving performance by controlling the angle, so if the control system were to malfunction, the vehicle's behavior could suddenly change or the vehicle could become unable to steer (the front , in the case of a device that controls both the rear wheels).

(Means for solving the problems) In order to solve the above problems, the present invention provides the first
It is equipped with the means shown in the figure.

The steady steering gain target value setting means 101 sets a target value of the steady steering gain corresponding to the vehicle speed V detected by the vehicle speed detecting means 100 according to a preset target steering characteristic.

The steering gear ratio target value calculation means 102 is
A steering gear ratio target value for realizing the steady steering gain target value while the host vehicle is in steady turning motion is determined by calculation using the vehicle specifications of the host vehicle.

Steering gear ratio variable means 103 sets the actual steering gear ratio of the host vehicle to the steering gear ratio target value.

On the other hand, the motion variable target value calculation means 105 calculates the vehicle speed based on the motion equation regarding the target vehicle having a preset target motion performance and the target steering characteristic used by the steady steering gain target value setting means 101. A target value of a vehicle motion variable corresponding to the vehicle speed V detected by the detection means 100 and the steering angle θ _S of the steering wheel detected by the steering wheel angle detection means 104 is determined.

The rear wheel steering angle target value calculation means 106 calculates the motion variable target value, the vehicle specifications of the host vehicle used by the steering gear ratio target value calculation means 102, and the steering gear ratio target value calculated by the same means. , from the vehicle speed V and the steering wheel steering angle θ _S , a target value _R of the rear wheel steering angle for realizing the motion variable target value in the own vehicle is determined.

The rear wheel steering means 107 adjusts the rear wheel steering angle target value _R.
Steer the rear wheels.

(Operation) The steering gear ratio variable means 103 controls the steady turning motion characteristics. This control is based on preset steering characteristics, and the vehicle speed V
The steady steering gain during steady turning motion of the own vehicle is determined by determining the target value of the steady steering gain corresponding to Almost equal to the target value.

On the other hand, the transient motion characteristics are controlled by the rear wheel steering means 1.
This is done by controlling the rear wheel steering angle using the control system 07. This control calculates target values of motion variables corresponding to vehicle speed V and steering wheel steering angle θ _S based on a target vehicle with a preset target motion performance. This is done by finding a target value _R of the wheel steering angle, and the motion variable during transient driving of the own vehicle becomes approximately equal to the target value.

The motion variable target value is determined based on the target steering characteristic used by the steady steering gain target value setting means 101, so the motion characteristic is realized by controlling the steering gear ratio and the rear wheel steering angle. Since these are mutually related characteristics, no sudden change in characteristics occurs when switching between steady turning motion and transient motion.

(Example) The configuration of one embodiment of the present invention is shown in FIG.

The arithmetic processing unit 1 is configured by a microcomputer or other electric circuit, and calculates the steering angle θ _S of the steering wheel 8 detected by the steering wheel steering angle sensor 2 and the steering angle θ S of the steering wheel 8 detected by the vehicle speed sensor 3 in this embodiment. The vehicle speed V of the vehicle equipped with the device (hereinafter referred to as "own vehicle") is input, predetermined calculations are performed, and a steering gear ratio target value and a rear wheel steering angle target value _R are output.

The power steering controller 4 includes a power steering device 5 that steers the front wheels 9 and 10.
The steering gear ratio N is variably set by controlling the working hydraulic pressure of the steering gear ratio N, and the working hydraulic pressure is changed in magnitude in accordance with the magnitude of the steering gear ratio target value supplied from the arithmetic processing unit 1. That is, even if the steering angle θ _S of the steering wheel 8 is the same, the larger the steering gear ratio target value is, the smaller the actual steering angle δ _F of the front wheels 9, 10 is controlled. Furthermore, as an example of the technology for hydraulic control of a power steering device,
There is a device shown in No. 24665.

The rear wheels 11 and 12 are equipped with a hydraulic steering device 7.
The hydraulic steering device 7 is controlled by the rear wheel steering device 6. This rear wheel steering device 6 includes an arithmetic processing device 1
The hydraulic pressure applied to the hydraulic steering device 7 is changed in accordance with the rear wheel steering angle target value _R input from the
The hydraulic steering device 7 is controlled so that the actual steering angle δ _R of the rear wheels 11 and 12 becomes the rear wheel steering angle target value δ _R (details are described in Tokugan No. 59-188153). ).

FIGS. 3 and 4 show that when the arithmetic processing device 1 is configured using a microcomputer,
This is a flowchart showing the processing executed by this arithmetic processing device 1.

The steering gear ratio control process shown in FIG.
This process is repeatedly executed at regular intervals to obtain a steering gear ratio target value to be supplied to the power steering controller 4.

In step 21, the vehicle speed V detected by the vehicle speed sensor 2 is read, and in the next step 22, a steady steering gain (in this embodiment, a steady yaw rate gain) corresponding to the read vehicle speed V is read. The target value of (used) is determined.

This can be determined using the following equation (1).

=V/(0+A ₀ V ² ) N ₀ L ₀ ...(1) Here, A ₀ , N ₀ , and L ₀ are assumed to be the vehicle with the target steering characteristics. A stability factor A ₀ comprising:
Steering gear ratio N ₀ and wheelbase
_L0 . These A ₀ , N ₀ , and L ₀ are stored in advance in the memory and read out when performing the above calculation.

Note that the above steady yaw rate gain target value is calculated using the formula
The reason expressed in (1) is explained below.

Generally, the steady yaw rate _cpost changes in proportion to the steering angle θ _S , and the relationship is as follows: _cpost = V/(1+A ₁ V ² )N ₁ L ₁ θ _S (2). Here, A ₁ is the stability factor, N ₁ is the steering gear ratio, and L ₁ is the wheel base.

Therefore, the coefficient when θ _S on the right side is used as a variable is the steady yaw rate gain, and the above equation (1) can be obtained.

Next, in the process of step 23, a calculation is performed to find a target value of the steering gear ratio in the own vehicle (the vehicle equipped with this embodiment) in order to realize the above-mentioned steady yaw rate gain in the own vehicle. This operation is expressed as
It is determined by (3).

＝Y＋√Y ² −4XZ／2X ...(3) Here, X＝１＋A _BASE V ² Y＝V／GL Z＝M／2L ²・2ξL _R ／K _S V ² , and furthermore, A _BASE ＝ −M/2L ²・L _F K _F −L _R K _R /K _F K _R. Also, the vehicle specifications used here are: K _F : Front wheel cornering power of the own vehicle (for one wheel) K _R : Rear wheel cornering power of the own vehicle (for one wheel) L: Wheelbase of the own vehicle L _F : Distance between the front axle and center of gravity of the own vehicle L _R : Distance between the rear axle and center of gravity of the own vehicle M: Body mass of the own vehicle ξ: Trail of the own vehicle (caster + neutral) K _S : Steering rigidity of the own vehicle It is.

Note that the above formula (3) is derived as follows.

The stability factor A of the vehicle is expressed as A=-M/2L ²・L _F eK _F −L _R K _R /eK _Fe K _R ……(4) where the front equivalent cornering power is ek _F. .

Here, front equivalent cornering power eK _F
I will provide a supplementary explanation. In general, the actual front wheel steering angle is returned by the torsion of the steering system such as the column shaft due to the restoring moment 2ξC _F (C _F is the front wheel cornering force) from the tires, so in practice it is θ _S /
N is smaller than ₁ . From the perspective of vehicle motion, this phenomenon is treated almost equivalently to a decrease in the cornering power of the front wheels, and the cornering power of the front wheels in this case is called front equivalent cornering power. This front equivalent cornering power is calculated from "Vehicle Dynamics and Control" by Masato Abe, published by Kyoritsu Shuppan.
As described on pages 111 and 112 of , eK _F = K _F /1+2ξ/N ² K _S K _F ...(5), so substitute equation (5) into equation (4). Then, A=−M/2L ²・L _F K _F −L _R K _R ／K _F K _R +M/2L ²
・2ξL _R /K _S・1/N ² ...(6) is obtained, and the first term on the right side is A _BASE .

By the way, from the above equation (2), the steady yaw rate gain (this is referred to as "G") is as follows: G=〓 _cpost /θ _S = V/(1+A ₁ V ² ) L ₁・1/N ₁ ...(7) Here, if we rewrite the relationship for the own vehicle, it becomes G=V/(1+AV ² )L・1/N...(8) Furthermore, since the above steady yaw rate gain target value is achieved by the own vehicle, Substituting G in equation (8) and transforming it yields (1+AV ² )=V/G・L・1/N (9). Multiply both sides of this equation (9) by N ² , and further,
Substituting the above formula (6), (1+A _BASE V ² )N ² +M/2L ²・2ξL _R /K _S V ² =V/G・LN ...(10) That is, XN ² −YN+Z=O ... It can be expressed as (11).

Therefore, when finding N from equation (11), N=Y±√Y ² −4XZ/2X, and since N>O, N=Y+√Y ² −4XZ/2X ...(12) is obtained. . The steering gear ratio N obtained by this equation (12) is the steering gear ratio of the own vehicle for realizing the above-mentioned steady yaw rate gain target value in the own vehicle.

The steering gear ratio target value N thus obtained is output to the power steering controller 4 through the process of step 25. As a result, the hydraulic pressure of the power steering device 5 is variably controlled, and the company's actual steering gear ratio N
is controlled so that it is equal to the steering gear ratio target value.

In addition, in the process of step 24, the front equivalent cornering power eK _F used in the rear wheel steering angle control process described later is calculated, and this eK _F is
It is obtained from an arithmetic expression obtained by substituting the above equation (5) as shown in the following equation (13).

eK _F = K _F /1+2ξ/ ² K _NS K _F ...(13) Next, the rear wheel steering angle control distance shown in Fig. 4 allows the vehicle to faithfully maintain the target steering characteristics mentioned above even during transient motion. This is a process for controlling the actual steering angle _δR of the rear wheels 11 and 12 so that it can be realized in the following manner, and is repeatedly executed at regular intervals.

In the process of step 33, the target value of the motion variable read in step 31 and corresponding to the steering wheel steering angle θ _S and the vehicle speed V is determined by calculation regarding the target vehicle having a preset target motion performance, that is, Yaw rate target value〓 and yaw angular acceleration target value〓
Calculate.

The above target vehicle is a simulation model (this is referred to as the "target vehicle model") in which a vehicle with the target dynamic performance is set using vehicle specifications and equations of motion, and the steering wheel steering angle θ is set as a variable. By giving _S and vehicle speed V, the target vehicle motion state corresponding to these θ _S and V can be found, and the yaw rate and yaw angular acceleration at this time are set to the above target values 〓, 〈
It is set as .

For these calculations, the target vehicle model is set so that the steady yaw rate gain is the same as the steady yaw rate gain target value used in the steering gear ratio control process by only front wheel steering, and the yaw rate with respect to the steering angle input is The transient response characteristics are set so that they are non-oscillatory regardless of vehicle speed.

One solution for making the yaw rate transient response characteristic non-oscillatory regardless of vehicle speed is to set the conditions for neutral steering, that is, the front wheel cornering power of the target vehicle model is K _F1 , the rear wheel cornering power is K _R1 , and the target vehicle When the distance between the model's front axis and center of gravity is L _F1 , and the distance between the rear axis and center of gravity is L _R1 , K _F1
Set =K _R1 and L _F1 =L _R1 .

Calculating the yaw rate gain G ₁ of the target vehicle model under these conditions, G ₁ = V/L ₁ · N ₁ ... (14') L ₁ : Wheelbase of the target vehicle model (L ₁ = L _F1
+L _R1 ) N ₁ : Steering gear ratio of the target vehicle model. In order to match G ₁ with , N ₁ is made a function of vehicle speed V, and N ₁ and L ₁ are given as shown in the following equations.

N ₁ = N ₀ (1 + A ₀ V ² ) L ₁ = L ₀ ... (14″) Specifically, with the above settings of the target vehicle model, by repeating the calculations shown below, Desired.

For equation (17), N ₁ = N ₀ (1+A ₀ V ² ) ...(14) Based on ¨ ₁ found in the previous equation (21), 〓 ₁ = ∫¨ ₁・dt ...( 15) Based on V〓 _y1 obtained using the previous equation (21'), _y1 =∫V〓 _y1・dt...(16) Using these〓 ₁ , _y1 and N ₁ of equation (14), β _F1 = θ _S /N ₁ − ( _y1 + L _F1 〓 ₁ ) / V ... (17) β _R1 = - ( _y1 − L _R1 〓 ₁ ) / V ... (18) Using these β _F1 and β _R1 C _F1 = K _F1 β _F1 ...(19) C _R1 = K _R1 β _R1 ...(20) Using these C _F1 and C _R1 , for equations (15) and (16), V〓 _y1 = {( 2C _F1 +2C _R1 )/M ₁ }〓 ₁ V ……(21′) ¨ ₁ = (2L _F1 C _F1 −2L _R1 C _R1 )/I _Z1 ……(21) ¨=¨ ₁ ……(22) 〓 =〓 ₁ ... (23) where, N ₁ : Steering gear ratio of the target vehicle model M ₁ : Body mass of the target vehicle model I _Z1 : Yaw inertia of the target vehicle model K _F1 : Front wheel cornering power K of the target vehicle model _R1 : Target vehicle model's rear wheel cornering power L _F1 : Distance between the target vehicle model's front axle and center of gravity L _R1 : Distance between the target vehicle model's rear axle and center of gravity L ₁ : Target vehicle model's wheelbase (L ₁ =L _F1
+L _R1 ) V _y1 : Lateral speed V of target vehicle model _y1 : Lateral acceleration β of target vehicle model _F1 : Front wheel sideslip angle of target vehicle model β _R1 : Rear wheel sideslip angle of target vehicle model C _F1 : Target vehicle Front wheel cornering force of the model C _R1 : Rear wheel cornering force of the target vehicle model ₁ : Yaw rate of the target vehicle model ₁ : Yaw angular acceleration of the target vehicle model.

As shown in equations (22) and (23) above, the yaw rate 〓 ₁ and the yaw angular acceleration 〈 ₁ of the target vehicle model become the yaw rate target value 〓 and the yaw angular acceleration target value 〓.

Yaw rate target value determined in this way〓
The target value _R of the rear wheel steering angle for realizing the target value of the yaw angular acceleration and the target value of the yaw angular acceleration in the own vehicle is determined by the process of the next step 34.

In calculating this rear wheel steering angle target value _R , the steering gear ratio target value and the front equivalent cornering power eK are adjusted so that the steering characteristic of the own vehicle is equal to the target steering characteristic used in the steering gear ratio control process. using _F , and
The calculation is performed using the own vehicle specifications having the same values as the own vehicle specifications used in the steering gear ratio control process.

Specifically, the rear wheel steering angle target value _R is determined by the following calculation.

Based on V〓 _y obtained from the previous equation (30), V _r =∫V〓 _y・dt ...(24) Using this V _r and the above 〓, β _F = θ _S /N−( V _y +L _F 〓)/V ......(25) Using this β _F and the above eK _F , C _F = eK _F・β _F ...... (26) Using this C _F and the above ¨, C _R = (L _F C _F −1/2¨I _Z ) L _R ... (27) Using this C _R β _R = C _R /K _R ... (28) Using this β _R , the above V _y , and the above 〓 8 _R = B _R + _y L _R 〓)/V......(29) For equation (24), using the above C _F , _CR and 〓, V〓 _y = (2C _F + 2C _R )/M-〓 V...(30) The vehicle specifications of the own vehicle and the motion variables of the own vehicle used here are as follows (however, regarding the vehicle specifications of the own vehicle used in the steering gear ratio control process, (I have written this before, so I will omit it here).

I _Z : Yaw inertia of own vehicle V _y : Lateral velocity of own vehicle V〓 _y : Lateral acceleration of own vehicle β _F : Front wheel sideslip angle of own vehicle β _R : Own vehicle rear wheel sideslip angle C _F : Own vehicle Front wheel cornering force of the vehicle C _R : Rear wheel cornering force of the own vehicle Rear wheel steering angle target value _R determined in this way
is supplied to the rear wheel steering device 6. Then, the rear wheel steering device 6 supplies the hydraulic pressure necessary for steering the rear wheels 11 and 12 to the given rear wheel steering angle target value _R to the hydraulic steering device 7. As a result, steering angle control of the rear wheels 11 and 12 is performed.

In this way, the device of this embodiment controls the steering gear ratio and rear wheel steering angle so that the vehicle faithfully achieves the target steering characteristics, and also controls the steering gear ratio primarily during steady turning operation. Also, by controlling the rear wheel steering angle mainly during transient motion, the target steering characteristics can be achieved both during steady turning motion and during transient motion.

In addition, since the control of the rear wheel steering angle is based on the target steering characteristics used in the control of the steering gear ratio and uses the same vehicle specifications, the steering characteristics during steady turning motion and transient motion are different. Different characteristics can be avoided and smooth turning operation can be performed.

In particular, rear wheel steering angle control is performed using the front equivalent cornering power determined in connection with steering gear ratio control, thereby compensating for changes in the vehicle's driving characteristics due to changes in the steering gear ratio. This allows for more appropriate rear wheel steering angle control.

In order to explain the effect of this embodiment more specifically, we will compare the change in the actual steering angle δ _R of the rear wheels and the change in the actual yaw rate 〓 when the steering wheel is operated as shown in Fig. 5. Figures 6 and 7
As shown in the figure.

The characteristic shown by the solid line A in FIG. 6 is the change characteristic of the rear wheel actual steering angle δ R of the vehicle equipped with the device of this embodiment, and the characteristic shown by the broken line B in the same figure is the change characteristic of the rear wheel actual steering angle δ _R of the vehicle equipped with the device of this embodiment. This is the change characteristic of the actual rear wheel steering angle of the vehicle to be controlled.

In the vehicle according to the prior application, the yaw rate change characteristic is stable both during steady turning motion and during transient motion (as shown by the solid line C in FIG. 7), similarly to the device equipped with this embodiment. However, at the same steering wheel steering angle θ _S , the amount of rear wheel turning is larger than that of the vehicle equipped with the device of this embodiment.

Therefore, in the unlikely event that the device malfunctions and the rear wheels cannot be steered (when the actual rear wheel steering angle δ _R becomes 0), a sudden change in vehicle behavior may occur. It will be done.

On the other hand, in the vehicle equipped with the device of this embodiment, since the amount of steering of the rear wheels is generally small, even if the above situation occurs, the behavior of the vehicle body does not change much.

Furthermore, in the case of a vehicle in which only the steering gear ratio is controlled, it is not possible to control the steering characteristics during transient motion, as shown by the broken line D in FIG.
Although the yaw rate change up to steady turning motion becomes oscillatory, the vehicle equipped with the device of this embodiment can obtain stable yaw rate change characteristics both during steady turning motion and during transient motion, as described above.

(Effects of the Invention) As explained in detail above, the present invention controls the steering gear ratio and the rear wheel steering angle in order to achieve the target steering characteristics in the own vehicle. The target steering characteristic can be faithfully realized by the vehicle both during motion and during transient motion, regardless of changes in vehicle speed. Therefore, by freely setting the target steering characteristics, it is possible to freely control the steering characteristics of the vehicle.

In addition, by controlling the steering system using two types of control: rear wheel steering angle control and steering gear ratio control, even if a failure occurs in the device of the present invention, vehicle behavior will not change significantly. Safety can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment of the present invention, and FIGS. 3 and 4 are flowcharts showing processing executed in the arithmetic processing device in FIG. FIG. 5 is a diagram showing an example of a change in steering angle of the steering wheel during a turning operation, and FIG. 6 is a diagram showing an actual steering angle of the rear wheels in a vehicle equipped with the device of the present invention when the steering angle of the steering wheel shown in FIG. 5 is changed. FIG. 7 is a characteristic diagram showing changes in the yaw rate. 100... Vehicle speed detection means, 101... Steady steering gain target value setting means, 102... Steering gear ratio target value calculation means, 103... Steering gear ratio variable means, 104... Handle steering angle detection means, 105... Motion variable target value calculation means, 10
6... Rear wheel steering angle target value calculation means, 107... Rear wheel steering means, 1... Arithmetic processing unit, 2... Steering wheel steering angle sensor, 3... Vehicle speed sensor, 4... Power steering controller (steering gear ratio variable means), 5... power steering device, 6
... Rear wheel steering device, 7 ... Hydraulic steering device, 8 ... Steering handle, 9, 10 ...
Front wheels, 11, 12... Rear wheels, θ _S ... Handle steering angle, V... Vehicle speed,... Steering gear ratio target value, _R ... Rear wheel steering angle target value, 〓... Yaw rate target value (motion variable Target value), ¨... Yaw angular acceleration target value (motion variable target value),... Steady yaw rate gain target value (steady steering gain target value), eK _F ...
...Front equivalent cornering power.

Claims (1)

[Scope of Claims] 1. Steering wheel steering angle detection means for detecting the steering angle of the steering wheel; Vehicle speed detection means for detecting vehicle speed; Steady steering that corresponds to the vehicle speed according to a preset target steering characteristic. Steady steering gain target value setting means for setting a target value of a gain; A steering gear ratio target value calculation means that calculates a steering gear ratio target value based on the vehicle speed by calculation using the vehicle specifications of the own vehicle, and a steering device that sets the actual steering gear ratio of the own vehicle to the steering gear ratio target value calculated by the calculation. The steering angle and the steering angle of the steering wheel are determined based on a gear ratio variable means, a motion system for a target vehicle having a preset target motion performance, and a target steering characteristic used by the steady steering gain target value setting means. a motion variable target value calculation means for calculating a target value of a vehicle motion variable corresponding to the vehicle speed; Rear wheel steering angle target value calculation for calculating a target value of a rear wheel steering angle to realize the motion variable target value from the steering gear ratio target value, the steering angle of the steering wheel, and the vehicle speed determined by the means. A steering system control device for a vehicle, comprising: means; and rear wheel steering means for steering the rear wheels according to the rear wheel steering angle target value determined by the means.