METHOD OF AND APPARATUS FOR CONTROLLING STEERING OF A VEHICLE

• US 20100100267A1
• Filed: 01/21/2008
• Published: 04/22/2010
• Est. Priority Date: 07/19/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries Engineering, Ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Hoshi, Mitsuaki, Katahira, Kousuke, Morita, Katsuaki, Yamaguchi, Masahiro, Morichika, Shunji
• Granted Patent: US 8,209,091 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: B61B 10/04 with vehicles rolling trackless on the ground
• CPC Class Codes: B62D 1/265 especially adapted for guiding road vehicles carrying loads or passengers, e.g. in urban networks for public transportation

Abstract

In a track type transportation system, there is provided an automatic steering mechanism with which a vehicle can be moved forward and backward, and which can carry our fine control so as to allow the positions of the centers of axles of the front and rear wheels to substantially follow up one and the same locus. Before starting, a pattern steering angle table on which pattern steering angles for the front and rear wheels at respective change points of the track are listed is prepared in view of a track condition, a running condition and a vehicle condition from a departure point to a destination point, the vehicle 12 is steered in accordance with a pattern steering angle read from the table, a track widthwise position of the vehicle 12 on running is detected so as to calculate correcting steering angles ΔXa, ΔXb by which the track widthwise position of the vehicle coincides with a desired position, and the correcting steering angles are added to pattern steering angles Xao, Xbo so as to obtain desired steering angles by which the front wheels 18, 22 are steered. The pattern steering angle, the corrected steering angle and the desired steering angle are calculated for each of the front and rear wheels, independent from each other.

Claims

1. A steering control method for automatically steering a vehicle so as to cause the vehicle to run on a predetermined track, the vehicle incorporating steering mechanisms including actuators by means of which front and rear wheels run on the track, characterized by the steps of

preparing a pattern steering angle table on which pattern steering angles for front and rear wheels are listed for respective change points of the track before stating, in view of a track condition, a running condition and a vehicle condition from a departure point to a destination point in order to steer the vehicle in accordance with pattern steering angles which are read from the table at every change point while a travel distance from the departure point is detected

detecting a track widthwise position of the vehicle on running so as to calculate correcting steering angles with which the track widthwise position of the vehicle coincides with a desired position, and

adding the correcting steering angels to the pattern steering angles so as to calculate desired steering angles in order to steer the front and rear wheels in accordance with the desired steering angles,

wherein the pattern steering angles, the correcting steering angles and the desired steering angles are calculated for the respective front and rear wheels, independent therebetween.

2. A steering control method for a vehicle as set forth in claim 1, characterized in that the pattern steering angles in a curved track are computed in view of a geometrical steering angle obtained from a radius of curvature of the track and a space between the front and rear wheels, a speed of the vehicle running on the curved track, and a slip angle produced at a tire and affected by a cant.

3. A steering control method for a vehicle as set forth in claim 1, further characterized by the steps of

obtaining a distance from the departure point to each of the change points of the track from a detected number of revolutions of the wheels from the departure point to the change point, and

deriving a distance coefficient which exhibits a ratio between a know distance from a departure point to a destination point of the last running block and a number of revolutions of the wheels which has been detected in this running block, in order to correct a distance detection error due to worn wheels.

4. A steering control method as set forth in claim 1, characterized in that the pattern steering angles along a transition curve between a curved track and a straight track are calculated by linear interpolation of steering angles on the curved track.

5. A steering control method for a vehicle as set forth in claim 1, characterized in that the corrected steering angles are calculated by adding the product of a deviation between the track widthwise position of the vehicle and a desired position, and a proportional gain to the product of a derivative gain and a time differential of the deviation.

6. A steering control method for a vehicle as set forth in claim 5, characterized in that the proportional gain is set to be variable in dependence upon a speed of the vehicle, the higher the vehicle speed, the smaller the proportional gain.

7. A steering control method for a vehicle as set forth in claim 1, characterized in that the correcting steering angle for the rear wheels is obtained by multiplying the correcting steering angle for the front wheel by a variable coefficient a which is set to α

<

1 when the vehicle speed is high, but is set to α

≧

1 when the vehicle speed is low or when the vehicle runs on a curved track.

8. A steering control apparatus for a vehicle, including a steering mechanism for automatically steering front and rear wheels of the vehicle by actuators so to cause the vehicle to run on a predetermined track, characterized by:

a start preparation means including

a storage means storing therein a distance, a track condition, a running condition and a vehicle condition from a departure point to a destination point, and

a first computing means for computing pattern steering angles for the front and rear wheels at respective change points of the track from data stored in the storage means so as to prepare a pattern steering angle table on which the pattern steering angles for the front and rear wheels at the respective change points are listed,

an on-running steering control means including;

a means for detecting a track widthwise position of the vehicle,

a distance detecting means for detecting a distance from a departure point,

a second computing means receiving steering angle data on the pattern steering angle table, and distance data from the distance detecting means, for calculating a pattern steering angle at an arbitrary running point, and receiving vehicle position data from the vehicle position detecting means so as to calculate a correcting steering angle with which the track widthwise position of the vehicle coincides with the desired position, and

a control means for controlling the actuators in accordance with the pattern steering angle and the correcting steering angle calculated by the computing means,

wherein the on-running steering control means is provided to each of the front and rear wheels, independent therebetween.

9. A steering control apparatus as set forth in claim 8, characterized in that there is provided a vehicle weight detecting means from which detection data is delivered to the computing means in the start preparation means.

10. A steering control apparatus as set forth in claim 8, characterized in that the track widthwise position detecting means is mounted on the vehicle, and is adapted to detect a track widthwise relative position with respect to a ground structure which is laid along the track with such a positional relationship that the relative position to the track is not changed.

11. A steering control apparatus as set forth in claim 10, characterized in that there is provided a fail-safe mechanism comprising a protection track laid on the track, and protection wheels provided underneath the vehicle and adapted to travel along the protection track, the track widthwise position detecting means is mounted to the lower portion of the vehicle at a position located in the protection track so as to detect track widthwise distances to left and right walls of the protection track in order to detect a track widthwise position of the vehicle.