Turning radius calculation method, steering assistance apparatus and parking assistance apparatus employing the turning radius calculation method, turning radius calculation program, and recording medium

• US 20060247834A1
• Filed: 03/23/2005
• Published: 11/02/2006
• Est. Priority Date: 04/26/2004
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Original Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Inventors: Shimazaki, Kazunori
• Granted Patent: US 7,706,943 B2
• Time in Patent Office: Days
• US Class Current: 701/36
• CPC Class Codes: B62D 15/021 Determination of steering angle
• CPC Class Codes: B62D 15/0225 by measuring on a steering gear element, e.g. on a rack bar
• CPC Class Codes: B62D 15/024 Other means for determination of steering angle without directly measuring it, e.g. deriving from wheel speeds on different sides of the car
• CPC Class Codes: B62D 15/0275 by overlaying a vehicle path based on present steering angle over an image without processing that image

Abstract

Disclosed is a turning radius calculation method including: expressing a steering system model by means of relational expressions having a steering angle and turning angles of outer and inner tires as variables and including known parameters and unknown parameters; entering data on the known parameters based on design data; calculating the unknown parameter from the relational expressions corresponding to a zero-steering state and the relational expressions corresponding to a full-steering state; calculating turning angles of outer and inner tires respectively corresponding to a plurality of steering angles between the zero-steering state and the full-steering state using the relational expressions where calculated data on the unknown parameters are entered; calculating turning radii corresponding to the calculated turning angles of the outer and inner tires; and calculating an approximate function of turning radius for steering angle based on the plurality of steering angles and the turning radii.

Claims

1. A turning radius calculation method comprising the steps of:

formulating relational expressions having a steering angle and turning angles of outer and inner tires as variables and including known parameters and unknown parameters by constructing a steering system model;

applying data on the known parameters based on design data to the relational expressions;

calculating values of the unknown parameters from conditional expressions obtained by applying values of the variables corresponding to a zero-steering state to the relational expressions and from conditional expressions obtained by applying values of the variables corresponding to a full-steering state to the relational expressions;

calculating turning angles of the outer and inner tires corresponding to a plurality of steering angles obtained by dividing a range between the zero-steering state and the full-steering state, respectively, by using the relational expressions to which the values of the unknown parameters are applied;

calculating turning radii corresponding to the steering angles from the calculated turning angles of the outer and inner wheels; and

calculating an approximate function of turning radius for steering angle based on the plurality of steering angles and the turning radii corresponding to the plurality of steering angles.

2. A turning radius calculation method according to claim 1, wherein a stroke of a rack moving in a lateral direction of the vehicle in accordance with steering of a steering wheel is included in the relational expressions as a variable corresponding to a steering angle.

3. A turning radius calculation method according to claim 1, wherein the turning radii corresponding to the turning angles of the outer and inner tires are calculated by taking as a turning center a midpoint between an intersection point of an axis of a right front wheel and an axis of rear wheels and an intersection point of an axis of a left front wheel and the axis of the rear wheels.

4. A turning radius calculation method according to claim 1, wherein the turning radii corresponding to the turning angles of the outer and inner tires are calculated by taking as a turning center a center of a turning circle which is set to balance slipping forces applied to right and left front wheels in a radial direction of the turning circle.

5. A turning radius calculation method according to claim 1, wherein the approximate function of turning radius is a power function.

6. A turning radius calculation method according to claim 1,

wherein the approximate function of turning radius is a function for calculating the turning radius from a tire turning angle of a two-wheel model, the tire turning angle of the two-wheel model being expressed as a function of the steering angle with an order of two or more.

7. A turning radius calculation method according to claim 5, wherein the turning radius is a turning radius of a steered vehicle wheel on an outside of a turn.

8. A steering assistance apparatus displaying on a monitor in a superimposed manner a vehicle rear view image during backward movement of a vehicle and a backward movement locus of the vehicle corresponding to a steering angle,

wherein the backward movement locus of the vehicle is displayed on the monitor based on a turning radius calculated from a steering angle by the turning radius calculation method according to claim 1.

9. A parking assistance apparatus providing guidance on an operation of parking a vehicle into a target parking space,

wherein guidance on the operation of parking the vehicle is provided based on a turning radius calculated from a steering angle by the turning radius calculation method according to claim 1.

10. A turning radius calculation program comprising relational expressions formulated from a steering system model, the relational expressions having a steering angle and turning angles of outer and inner tires as variables and including known parameters and unknown parameters, the program causing a computer to execute the steps of:

reading data on the known parameters based on design data on a vehicle;

calculating values of the unknown parameters from conditional expressions obtained by applying values of the variables corresponding to a zero-steering state to the relational expressions and from conditional expressions obtained by applying values of the variables corresponding to a full-steering state to the relational expressions;

calculating a plurality of steering angles and turning angles of the outer and inner tires corresponding to the plurality of steering angles between the zero-steering state and the full-steering state, respectively, by using the relational expressions to which the values of the unknown parameters are applied;

calculating turning radii corresponding to the steering angles from the calculated turning angles of the outer and inner wheels; and

calculating an approximate function of turning radius for steering angle based on the plurality of steering angles and the turning radii corresponding to the plurality of steering angles.

11. A turning radius calculation program according to claim 10, wherein a stroke of a rack moving in a lateral direction of the vehicle in accordance with steering of a steering wheel is included in the relational expressions as a variable corresponding to a steering angle.

12. A turning radius calculation program according to claim 10, wherein the turning radii corresponding to the turning angles of the outer and inner tires are calculated by taking as a turning center a midpoint between an intersection point of an axis of a right front wheel and an axis of rear wheels and an intersection point of an axis of a left front wheel and the axis of the rear wheels.

13. A turning radius calculation program according to claim 10, wherein the turning radii corresponding to the turning angles of the outer and inner tires are calculated by taking as a turning center a center of a turning circle which is set to balance slipping forces applied to right and left front wheels in a radial direction of the turning circle.

14. A computer-readable recording medium in which the turning radius calculation program according to claim 10 is recorded.