JPH05238403A - Four-wheel steering gear - Google Patents

Abstract

PURPOSE:To exhibit avoiding ability to the maximum extent, by computing a vehicle locus from a car speed and a steering wheel angle defree of danger of collision from distance and relative speed to an obstacle, and a space for avoidance from distant to a movable body on the side and the relative speed, respectively and by calculating locus for avoiding the danger, and determining ratio of steering angles between front and rear wheels. CONSTITUTION:A controller 20 calculates a vehicle locus based on information of a car speed sensor 14 and a steering wheel angle sensor 15. A distance and relative speed to an obstacle positioned ahead are calculated based on information of a front obstacle sensor 11 or a rear obstacle sensor 12. It is determined whether there is any danger to collide or not, based on the relation between respectively calculated vehicle locus and the obstacle. When there is a danger to collide, the space for avoidance is calculated based on information of a side obstacle detecting means 13. Next, a locus for avoidance is determined based on these results. Ratio of steering angles in front and rear wheels is thus determined, and a rear wheel steering actuator is controlled so that the set ratio of steering angle is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-wheel steering system which can maximize its avoidance ability in an emergency avoidance.

[0002]

2. Description of the Related Art A four-wheel steering system is widely known in which the steering characteristics of a vehicle are improved by steering the rear wheels in the same phase or in the opposite phase according to the steering of the front wheels. Such a four-wheel steering system determines the steering angle of the rear wheels according to the vehicle condition such as vehicle speed and yaw rate.
I try to steer the rear wheels.

[0003]

However, in the conventional device, the steering angle of the rear wheels is not physically configured to be steered to the maximum angle, so that the steering angle amount of the rear wheels is insufficient during emergency avoidance. There was a problem. The present invention has been made in view of the above points, and an object of the present invention is to provide a four-wheel steering device capable of maximizing the avoidance ability during emergency avoidance.

[0004]

A four-wheel steering system according to the present invention is a vehicle locus calculation means for calculating a locus of a vehicle, and the locus of the vehicle calculated by the vehicle locus calculation means is an obstacle in front of the vehicle. Collision risk judging means for judging the risk of collision, moving body state detecting means for detecting the state of the moving body on the side of the vehicle, and moving body on the side of the vehicle detected by this moving body state detecting means In consideration of the state, the avoidance space calculating means for calculating the avoidance space for avoiding the obstacle ahead of the vehicle, and the avoidance space calculated by the avoidance space calculating means are considered. Avoidance trajectory calculation means for calculating the avoidance trajectory of the vehicle, front and rear wheel steering ratio calculation means for calculating the front and rear wheel steering ratio according to the avoidance trajectory of the vehicle calculated by the avoidance trajectory calculation means, front wheel steering angle and rear wheel The ratio to the steering angle is the front-rear wheel steering ratio. ; And a wheel steering means after steering the rear wheels.

[0005]

The locus of the vehicle is calculated based on the data such as the vehicle speed and the steering wheel angle, and the risk of the vehicle colliding with the obstacle is judged based on the inter-vehicle distance and the relative speed of the obstacle ahead. Further, the distance to the moving body on the side surface of the vehicle and the relative speed with respect to the moving body are calculated, and the avoidance space that the vehicle can avoid is calculated. When it is determined that there is a risk of collision, the avoidance space is considered to calculate the avoidance trajectory, and the front / rear wheel turning ratio is calculated according to the avoidance trajectory. Then, the rear wheels are steered so that the ratio between the front wheel steering angle and the rear wheel steering angle becomes the front-rear wheel turning ratio.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A four-wheel steering system according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a four-wheel steering system, FIG. 2 is a perspective view of a vehicle showing mounting locations of sensors mounted on the vehicle, and FIG. 3 is a diagram showing an avoidance trajectory of the vehicle in an emergency. 4 and 5 are controls
FIG. 6 is a block diagram showing the detailed configuration of the steering wheel, and FIG.
It is a figure which shows / d characteristic.

In FIG. 1 and FIG. 2, 11 is an obstacle sensor in front of the vehicle and a forward obstacle sensor such as a CCD camera provided for taking a white line on the road, and 12 is for taking an obstacle behind the vehicle. A rear obstacle sensor, such as a CCD camera, provided at the side of the vehicle is provided for detecting a distance to a moving body on the side of the vehicle. For example, a side obstacle is composed of a plurality of ultrasonic transceivers. Means, 1
Reference numeral 4 is a vehicle speed sensor for detecting the vehicle speed, and 15 is a steering wheel angle sensor for detecting the steering angle of the steering wheel.

The above-mentioned lateral obstacle sensor 13 is composed of a plurality of ultrasonic wave transmitters / receivers 13 _{1 to} 13 _{4, and} ultrasonic waves are transmitted to both side surfaces of the vehicle in a direction orthogonal to the side surface of the vehicle and diagonally forward. It is set up to be transmitted.

The detection signals of the sensors 11, 12, 14, 15 and the detection means 13 are input to the controller 20. The detailed configuration of the controller 20 is shown in FIGS.
Will be described later.

The controller 20 includes a braking device 21 for braking the front and rear wheels, a rear wheel steering actuator 22 for controlling the steering of the rear wheels, and an alarm device 23 for warning that an obstacle ahead cannot be avoided. Connected.

Next, the detailed configuration of the controller 20 will be described with reference to FIGS. 4 and 5. Vehicle speed sensor 1
The vehicle speed detected at 4 and the steering wheel angle detected at the steering wheel angle sensor 15 are input to the vehicle trajectory calculation unit 31. A memory 32 that stores the driving characteristic data of the vehicle is connected to the vehicle trajectory calculation unit 31. The driving characteristic data is data necessary for estimating the locus of the vehicle when the vehicle speed and the steering wheel angle are specified, and is, for example, data such as vehicle weight and wheel base. ..

The vehicle trajectory calculation unit 31 reads the vehicle speed and the steering wheel angle at every predetermined sampling time, and the memory 3 is read each time.
The vehicle trajectory is calculated in consideration of the vehicle driving characteristic data stored in 2.

Further, the front video signal taken by the front obstacle sensor 11 is output to the inter-vehicle distance / relative speed calculation unit 33, the vehicle recognition unit 34, and the white line recognition unit 35. The inter-vehicle distance / relative speed calculation unit 33 calculates the inter-vehicle distance L and the relative speed Vr between the obstacle ahead and the vehicle based on the input video signal. Further, the vehicle recognition unit 34 calculates the lateral position x of the vehicle with respect to the obstacle based on the input video signal. Further, the white line recognition unit 35 performs recognition processing for recognizing a white line on the road from the input video signal. Then, the recognition processing data is a corner R calculating section 36 for calculating the turning radius R of the road.
Is output to.

The inter-vehicle distance L and the relative speed Vr calculated by the inter-vehicle distance / relative speed calculating section 33 and the lateral position X of the vehicle with respect to the obstacle calculated by the vehicle recognizing section 34 are output to the collision risk judging section 37, respectively. It Based on the vehicle trajectory data calculated by the vehicle trajectory calculator 31, the collision risk determiner 37 determines an inter-vehicle distance L between the obstacle and the vehicle ahead, a relative speed Vr, and a lateral position x of the vehicle with respect to the obstacle. Considering the above, the risk of a vehicle collision is determined. Specifically, if it is predicted that the vehicle will collide with an obstacle ahead even if the maximum braking (for example, 0.4 g) is performed, a collision risk determination signal is output, and other than that. Outputs a judgment signal that has no risk of collision.

The reception signals of the ultrasonic signals transmitted by the ultrasonic transmitters / receivers 13 _{1 to} 13 ₄ constituting the lateral obstacle detecting means 13 are output to the distance calculating section 38. This distance calculation unit 3
8 _{1-38 4} denotes a distance between the transmission time and the ultrasound is mobile and the vehicle in consideration of the reception time input is reflected by the movement of the output ultrasonic signal from the side obstacle sensor 13 x1 to x4 are calculated respectively.

The distances x1 to x4 calculated by the distance calculation units 38 _{1 to} 38 ₄ are output to the moving body recognition unit 39. The moving body recognizing unit 39 calculates relative velocities Vr1 to Vr4 with a moving body existing on the side of the vehicle in consideration of the installation locations and installation directions of the ultrasonic transmitters / receivers 13 _{1 to} 13 ₄ and avoids space. To the calculation unit 40.

The video signal of the rear vehicle taken by the rear obstacle sensor 12 is output to the inter-vehicle distance calculating section 41 and the vehicle recognizing section 42. The inter-vehicle distance calculation unit 41 calculates the inter-vehicle distance L1 with the vehicle behind based on the input video signal, and outputs it to the avoidance space calculation unit 40. Further, the vehicle recognition unit 42 calculates the lateral position x5 of the vehicle with respect to the rear vehicle based on the input video signal, and the avoidance space calculation unit 4
Output to 0.

The avoidance space calculation unit 40 is output from the inter-vehicle distance / relative speed calculation unit 33 and the vehicle recognition unit 34, the inter-vehicle distance L and the relative speed Vr, the left / right position x, and the moving body recognition unit 39. Based on the relative speeds Vr1 to Vr4 with respect to the vehicle on the side of the vehicle, the inter-vehicle distance L1 with the rear vehicle output from the inter-vehicle distance calculating section 41, and the left-right position x5 with respect to the rear vehicle output from the vehicle recognizing section 42. An avoidance space for avoiding an obstacle ahead is calculated.

The avoidance space data output from the avoidance space calculating section 40 and the collision risk judging section 3 described above.
The determination signal output from 7 is input to the avoidance trajectory calculation unit 43. A memory 32 for storing the motion characteristic data of the vehicle is connected to the avoidance trajectory calculation unit 43. The avoidance locus calculation unit 43 is input from the avoidance space calculation unit 40 when the collision risk determination signal output from the collision risk determination unit 37 is a signal that determines that there is a collision risk. Based on the avoidance space data, the avoidance trajectory for avoiding the obstacle ahead of the vehicle is calculated. This avoidance trajectory is calculated by estimating a trajectory that can minimize the lateral G that occurs when avoiding, and a trajectory that maximizes the distance d to the obstacle ahead is calculated as shown in FIG. To be done.

If the collision risk determination signal output from the collision risk determination unit 37 is a signal that determines that there is no collision risk, the avoidance trajectory calculation unit 43 eliminates the risk of collision. The braking amount necessary for the above is determined, and braking data is created.

The avoidance locus calculation unit 43 includes a braking control unit 4
A braking device 45 is connected via 4. Further, a front wheel steering unit 47 is connected to the avoidance trajectory calculation unit 43 via a front wheel steering control unit 46 that automatically steers the front wheels.

Further, a front / rear wheel turning ratio control unit 48 is connected to the avoidance trajectory calculation unit 43. The front wheel steering angle signal θf output from the front wheel steering control unit 46 is input to the front / rear wheel turning ratio control unit 48, and the turning radius R of the road and the vehicle speed sensor 14 calculated by the corner R calculation unit 36 are input. The vehicle speed V detected at is input.

The avoidance locus calculation unit 43 determines the vehicle speed V and the turning radius R.
A more necessary yaw rate number 1 is calculated. And
The maximum front-rear wheel turning ratio Kmax (Equation 2) corresponding to this yaw rate is calculated. Further, the steering ratio K of the front and rear wheels is calculated according to the avoidance trajectory data calculated by the avoidance trajectory calculating unit 43. This turning ratio K is represented by the function of w / d shown in FIG.

[0024]

[Equation 1]

[0025]

[Equation 2]

That is, K = f (w / d), and the relationship between the steering ratio K and w / d is as shown in FIG. As shown in FIG. 6, when w / d is small, the steering ratio is 4w, which is the conventional value.
It is set to the steering ratio Ko of s (however, Ko is a function of the vehicle speed V), and gradually increases to 1 when w / d increases. The steered ratio K is the ratio of the steering angles of the front wheels and the rear wheels, and is a value of "1" or less. If the steering ratio K calculated by the front / rear wheel steering ratio control unit 48 is smaller than Kmax, the steering ratio K is determined as the final steering ratio.

The front / rear wheel steering ratio control unit 48 calculates the steering angle θr of the rear wheels by multiplying the steering angle K of the front wheels by the steering ratio K, and outputs the steering angle θr to the rear wheel steering actuator 22. The rear wheel steering actuator 22 controls the steering angle of the rear wheels so that the input steering angle θr of the rear wheels is obtained.

Next, the operation of the embodiment of the present invention constructed as above will be described. Vehicle trajectory calculation unit 31
Reads the vehicle speed and the steering wheel angle at every predetermined sampling time, and calculates the locus of the vehicle in consideration of the driving characteristic data of the vehicle stored in the memory 32 each time.

The collision risk judgment unit 37 is the vehicle trajectory calculation unit 3
Based on the vehicle trajectory data calculated in step 1, the risk of collision of the vehicle is determined in consideration of the inter-vehicle distance L between the front obstacle and the vehicle, the relative speed Vr, and the lateral position x of the vehicle with respect to the obstacle. .. Specifically, if it is predicted that the vehicle will collide with an obstacle ahead even if the maximum braking (for example, 0.4 g) is performed, a collision risk determination signal is output, and other than that. Outputs a judgment signal that has no risk of collision.

The moving body recognizing section 39 is the side obstacle sensor 13
The relative velocities Vr1 to Vr4 with respect to the moving body existing on the side of the vehicle are calculated in consideration of the installation location and the installation direction thereof and output to the avoidance space calculation unit 40.

The avoidance space calculating section 40 is outputted from the following distance / relative speed calculating section 33 and the vehicle recognizing section 34, the following distance L and relative speed Vr, the left / right position x and the moving body recognizing section 39. Based on the relative speeds Vr1 to Vr4 with respect to the vehicle on the side of the vehicle, the inter-vehicle distance L1 with the rear vehicle output from the inter-vehicle distance calculating section 41, and the left-right position x5 with respect to the rear vehicle output from the vehicle recognizing section 42. An avoidance space for avoiding an obstacle ahead is calculated.

The avoidance trajectory calculation unit 43 is a collision risk judgment unit 3
If the collision risk determination signal output from 7 is a signal that determines that there is a collision risk, the vehicle is detected based on the avoidance space data input from the avoidance space calculator 40. Calculate the mark that can avoid the obstacle in front. This locus is calculated by estimating a locus that can minimize the lateral G that occurs when avoiding, and a locus that maximizes the distance d to the obstacle ahead is calculated as shown in FIG. It

If the collision risk determination signal output from the collision risk determination unit 37 is a signal for determining that there is no collision risk, the avoidance trajectory calculation unit 43 eliminates the risk of collision. The braking amount necessary for the above is determined, and braking data is created.

The avoidance locus calculation unit 43 determines the vehicle speed V and the turning radius R.
The required yaw rate of 3 is calculated. And
The maximum front-rear wheel turning ratio Kmax (Equation 4) corresponding to this yaw rate is obtained. Further, the steering ratio K of the front and rear wheels is calculated according to the avoidance trajectory data calculated by the avoidance trajectory calculating unit 43. If the turning ratio K is smaller than Kmax, the turning ratio K is determined as the final turning ratio.

[0035]

[Equation 3]

[0036]

[Equation 4]

Then, the front wheel steering control section 46 automatically steers the front wheels. The front / rear wheel steering ratio control unit 48 calculates the steering angle θr of the rear wheels by multiplying the steering ratio K by the front wheel steering angle θr output from the front wheel steering control unit 46, and outputs the steering angle θr to the rear wheel steering actuator 22. To do. The rear wheel steering actuator 22 controls the steering angle of the rear wheels so that the input steering angle θr of the rear wheels is obtained. Although the above embodiment is an apparatus that automatically steers the front wheels, the same can be applied to an apparatus that a driver steers the front wheels.

As described above, the avoidance trajectory calculated by the avoidance trajectory calculating section 43 is calculated by estimating a trajectory that can minimize the lateral G generated when avoiding, and the steering ratio K is calculated as the avoidance trajectory deduction. Since it is calculated according to the data, the yaw rate generated in the vehicle when avoiding an obstacle can be suppressed to the minimum required size. Further, if the avoidance locus shown in FIG. 3 is d = d1 and w = w1, the steering ratio K at this time is as shown in FIG.
It becomes K1. Since this turning ratio K is larger than the conventional turning ratio Ko, it is possible to set the avoidance ability larger than the conventional one.

Further, the required number of yaw rates 5 is calculated from the vehicle speed V and the turning radius R, the maximum front-rear wheel steering ratio Kmax (equation 6) corresponding to the yaw rate is calculated, and the steering ratio K is calculated. Since the maximum front-rear wheel turning ratio Kmax (equation 7) is set in the range, it is possible to reduce divergence due to excessive turning in an emergency. That is, it is possible to exert the maximum avoidance ability among the physically possible avoidance ability.

[0040]

[Equation 5]

[0041]

[Equation 6]

[0042]

[Equation 7]

[0043]

As described above in detail, according to the present invention, it is possible to maximize the avoidance ability at the time of emergency avoidance.
A wheel steering device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a four-wheel steering system according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mounting location of sensors mounted on the vehicle body.

FIG. 3 is a diagram showing a vehicle avoidance trajectory in an emergency.

FIG. 4 is a block diagram showing a part of a detailed configuration of the controller shown in FIG.

5 is a block diagram showing a part of a detailed configuration of the controller shown in FIG.

FIG. 6 is a diagram showing a steering ratio Kw / d characteristic.

[Explanation of symbols]

11 ... Front obstacle sensor, 12 ... Rear obstacle sensor, 1
3 ... Side obstacle sensor, 14 ... Vehicle speed sensor, 15 ... Steering wheel angle sensor.

Claims (1)

[Claims] 1. A vehicle trajectory calculating means for calculating a vehicle trajectory, and a collision risk determining means for determining a risk that the vehicle trajectory calculated by the vehicle trajectory calculating means collides with an obstacle in front of the vehicle. A moving body state detecting means for detecting the state of the moving body on the side of the vehicle and an obstacle in front of the vehicle in consideration of the state of the moving body on the side of the vehicle detected by the moving body state detecting means. An avoidance space calculating means for calculating an avoidance space for avoiding the vehicle, and an avoidance trajectory calculating means for calculating an avoidance trajectory of the vehicle in consideration of the avoidance space calculated by the avoidance space calculating means. The front-rear wheel steering ratio calculation means for calculating the front-rear wheel steering ratio according to the vehicle avoidance trajectory calculated by the avoidance trajectory calculation means, and the ratio of the front wheel steering angle to the rear wheel steering angle become the front-rear wheel steering ratio. And rear wheel steering means for steering the rear wheels A four-wheel steering device characterized by the above.