Method and apparatus for steering a vehicle

• US 5,076,382 A
• Filed: 06/23/1989
• Issued: 12/31/1991
• Est. Priority Date: 06/23/1989
• Status: Expired due to Term

• Current Assignee: TRW Inc. (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Vaughn, Brian V., Miller, Laurence L.
• Primary Examiner(s): Rice, Kenneth R.
• Assistant Examiner(s): Kagen, Alan M.
• Application Number:
  US07/370,646
• Time in Patent Office: 921 Days
• Field of Search: 180/140, 180/141, 180/143, 180/132, 280/91
• US Class Current: 180/413
• CPC Class Codes: B62D 7/1509 with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A method and apparatus for controlling a vehicle steering system of the type having front steerable wheels and rear steerable wheels. The present invention permits the vehicle operator to select front wheel only steering, crab steering, or curl steering. If the vehicle speed is above a predetermined value, steering control is automatically switched to front wheel only steering, and the rear steerable wheels are locked in the straight-ahead direction. The lock mechanism is not actuatable until the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction. If the vehicle operator switches from one steering mode to another steering mode, the rear steerable wheels must return to a near straight-ahead direction before the mode will be switched. When the vehicle wheels are locked in front wheel only steering and the lock mechanism is deactuated so as to unlock the rear wheels from the vehicle frame but the rear wheels do not unlock, the present invention applies alternately driving forces to the rear steerable wheels so as to dither the wheels and free the locking mechanism. A lock mechanism is also disclosed.

Claims

1. A steering apparatus for a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said apparatus comprising:

a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle, said front steering assembly effecting steering movement of the front set of steering wheels in response to turning of the vehicle steering wheel;

a controllable rear steering assembly connected to the rear set of steerable wheels for effecting steering movement of the rear set of steerable wheels in response to a rear steering control signal;

means for selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

first sensing means for sensing steering angle of the front set of steerable wheels and for providing a signal indicative thereof;

second sensing means for sensing steering angle of the rear set of steerable wheels and for providing a signal indicative thereof;

control means connected to said selecting means, said first sensing means, said second sensing means, and said controllable rear steering assembly for providing said rear steering control signal to effect steering movement of the rear set of steerable wheels in response to the selected steering mode and in response to the signal from said first sensing means, said control means effecting a change from one steering mode to another steering mode in response to a change in the selected steering mode only after the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction;

vehicle speed sensing means connected to said control means for sensing vehicle speed and providing a signal indicative thereof;

actuatable locking means connected to said control means and operatively connected to the vehicle frame and the rear set of steerable wheels for, when actuated by said control means, locking the rear set of steerable wheels in a straight-ahead direction when the rear set of steerable wheels are in the straight-ahead direction, said control means actuating said locking means when the vehicle speed is sensed to be greater than a speed threshold value stored in said control means, said control means deactuating said locking means after sensed vehicle speed decreases below a second predetermined value less than the predetermined value used by the control means to actuate the locking means; and

lock sensing means for sensing if, upon deactuation of said locking means, said locking means has unlocked said rear set of steerable wheels from the vehicle frame and for providing a signal indicative thereof;

and wherein after said control means deactuates said locking means and said lock sensing means indicates that said locking means has not unlocked said rear set of steerable wheels from the vehicle frame, said control means provides said rear steering assembly with said rear steering control signal for a predetermined time period.

2. A steering apparatus for a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said apparatus comprising:

a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle, said front steering assembly effecting steering movement of the front set of steerable wheels in response to turning of the vehicle steering wheel;

a controllable rear steering assembly connected to the rear set of steerable wheels for effecting steering movement of the rear set of steerable wheels in response to a rear steering control signal;

means for selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

first sensing means for sensing steering angle of the front set of steerable wheels and for providing a signal indicative thereof;

second sensing means for sensing steering angle of the rear set of steerable wheels and for providing a signal indicative thereof;

control means connected to said selecting means, said first sensing means, said second sensing means, and said controllable rear steering assembly for providing said rear steering control signal to effect steering movement of the rear set of steerable wheels in response to the selected steering mode and in response to the signal from said first sensing means, said control means effecting a change from one steering mode to another steering mode in response to a change in the selected steering mode only after the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction;

vehicle speed sensing means connected to said control means for sensing vehicle speed and providing a signal indicative thereof;

actuatable locking means connected to said control means and operatively connected to the vehicle frame and the rear set of steerable wheels for, when actuated by said control means, locking the rear set of steerable wheels in a straight-ahead direction when the rear set of steerable wheels are in the straight-ahead direction, said control means actuating said locking means when the vehicle speed is sensed to be greater than a speed threshold value stored in said control means; and

locking sensing means for sensing if, upon actuation of said locking means, said locking means has locked said rear set of steerable wheels to the vehicle frame and for providing a signal indicative thereof;

and wherein said control means, after actuating said locking means and sensing said locking means has not steerably locked said rear set of steerable wheels to the vehicle frame, providing said rear steering assembly with said rear steering control signal so as to steer the rear steerable wheels toward a straight-ahead direction.

3. The apparatus of claim 2 wherein said control means effects a reversal of the steering direction of the rear steerable wheels by said rear steering control signal if said rear set of steerable wheels are sensed to have passed the straight-ahead direction and the locking means is sensed to have not locked said rear set of steerable wheels in a straight-ahead direction.

4. A steering apparatus for a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steering wheels steerably secured to a vehicle frame, said apparatus comprising:

a front steering assembly connected to the front set of steerable wheels and a steering wheel of the vehicle, said front steering assembly effecting steering movement of the front set of steerable wheels in response to turning of the vehicle steering wheel;

a controllable rear steering assembly connected to the rear set of steerable wheels for effecting steering movement of the rear set of steerable wheels in response to a rear steering control signal;

means for selecting one of a plurality of steering modes including (i) front wheel steering only, (ii) crab steering, and (iii) curl steering;

first sensing means for sensing steering angle of the front set of steerable wheels and for providing a signal indicative thereof;

second sensing means for sensing steering angle of the rear set of steerable wheels and for providing a signal indicative thereof;

third sensing means for sensing speed of the vehicle and providing a signal indicative thereof;

actuatable locking means connected to the vehicle frame and to the rear set of steerable wheels for, when actuated and when said rear set of steerable wheels are in a straight-ahead direction, locking said rear set of steerable wheels in the straight-ahead direction;

data input means accessible to and operable by an operator of the vehicle for establishing a rear wheel steering lock speed value;

control means connected to said first, second, and third sensing means, said steering mode selecting means, said actuable locking means, said data means, and said controllable rear steering assembly for controlling the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the signal from said first sensing means, said control means actuating said locking means when the sensed vehicle speed is greater than said rear wheel steering lock speed value, said control means deactuating said locking means after sensed vehicle speed decreases below a second predetermined value less than the predetermined value used by the control means to actuate the locking means; and

lock sensing means connected to said control means for sensing if said locking means has unlocked said rear set of steerable wheels from the vehicle frame and for providing a signal indicative thereof;

and wherein after said control means has deactuated said locking means, said lock sensing means indicates that said locking means has not unlocked said rear set of steerable wheels from the vehicle frame, said control means providing said rear steering assembly with said rear steering control signal for a predetermined time period.

5. A steering apparatus for a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steering wheels steerably secured to a vehicle frame, said apparatus comprising:

a front steering assembly connected to the front set of steerable wheels and a steering wheel of the vehicle, said front steering assembly effecting steering movement of the front set of steerable wheels in response to turning of the vehicle steering wheel;

a controllable rear steering assembly connected to the rear set of steerable wheels for effecting steering movement of the rear set of steerable wheels in response to a rear steering control signal;

means for selecting one of a plurality of steering modes including (i) front wheel steering only, (ii) crab steering, and (iii) curl steering;

first sensing means for sensing steering angle of the front set of steerable wheels and for providing a signal indicative thereof;

second sensing means for sensing steering angle of the rear set of steerable wheels and for providing a signal indicative thereof;

third sensing means for sensing speed of the vehicle and providing a signal indicative thereof;

actuatable locking means connected to the vehicle frame and to the rear set of steerable wheels for, when actuated and when said rear set of steerable wheels are in a straight-ahead direction, locking said rear set of steerable wheels in the straight-ahead direction;

data input means accessible to and operable by an operator of the vehicle for establishing a rear wheel steering lock speed value;

control means connected to said first, second, and third sensing means, said steering mode selecting means, said actuable locking means, said data input means, and said controllable rear steering assembly for controlling the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the signal from said first sensing means, said control means actuating said locking means when the sensed vehicle speed is greater that said rear wheel steering lock speed value;

said control means providing said rear steering control signal so as to initially cause said rear steerable wheels to be moved to a straight-ahead direction independent of the selected steering mode and independent of the sensed vehicle speed; and

lock sensing means connected to said control means for sensing if said locking means has locked said rear set of steerable wheels to the vehicle frame and for providing a signal indicative thereof;

and wherein said control means, after actuating said locking means and sensing said locking means has not steerably locked said rear set of steerable wheels to the vehicle frame, providing said rear steering assembly with said rear steering control signal so as to steer the rear steerable wheels toward a straight-ahead direction.

6. The apparatus of claim 5 wherein said control means effects a reversal of the steering direction of the rear steerable wheels if said rear set of steerable wheels are sensed to have passed the straight-ahead direction and the locking means is sensed to have not locked the rear set of steerable wheels to the vehicle frame.

7. A steering apparatus for a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steering wheels steerably secured to a vehicle frame, said apparatus comprising:

a front steering assembly connected to the front set of steerable wheels and a steering wheel of the vehicle, said front steering assembly effecting steering movement of the front set of steerable wheels in response to turning of the vehicle steering wheel;

a controllable rear steering assembly connected to the rear set of steerable wheels for effecting steering movement of the rear set of steerable wheels in response to a rear steering control signal;

means for selecting one of a plurality of steering modes including (i) front wheel steering only, (ii) crab steering, and (iii) curl steering;

first sensing means for sensing steering angle of the front set of steerable wheels and for providing a signal indicative thereof;

second sensing means for sensing steering angle of the rear set of steerable wheels and for providing a signal indicative thereof;

third sensing means for sensing speed of the vehicle and providing a signal indicative thereof;

actuatable locking means connected to the vehicle frame and to the rear set of steerable wheels for, when actuated and when said rear set of steerable wheels are in a straight-ahead direction, locking said rear set of steerable wheels in the straight-ahead direction;

data input means accessible to and operable by an operator of the vehicle for establishing a rear wheel steering lock speed value;

control means connected to said first, second, and third sensing means, said steering mode selecting means, said actuable locking means, said data input means, and said controllable rear steering assembly for controlling the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the signal from said first sensing means, said control means actuating said locking means when the sensed vehicle speed is greater than said rear wheel steering lock speed value; and

said actuatable locking means including a lock actuator mounted to a pivotal portion of the rear steerable wheels, said lock actuator including a slidable locking pin, said lock actuator sliding said locking pin outward when actuated thereby extending said locking pin and sliding said locking pin inward when unactuated, a latching block secured to a frame of the vehicle and including a locking pin receiving groove for, when said locking pin is extended and the rear steerable wheels are in a straight-ahead direction, receiving said locking pin so as to maintain the rear steerable wheels in the straight-ahead direction.

8. The apparatus of claim 7 wherein said locking means further includes spring bias means which, upon actuation of said lock actuator, applies a bias force to said locking pin toward a direction which extends said locking pin.

9. The apparatus of claim 7 wherein said lock actuator further includes an electric motor and a rotary-to-linear motion converter arranged such that, when said lock actuator is actuated, said electric motor in combination with said rotary-to-linear motion converter slides said locking pin outward.

10. The apparatus of claim 7 wherein said locking means further includes a locking pin position sensor for, when said locking pin is received in said locking pin receiving groove of said latching block, providing a first electrical signal, and when said locking pin is not received in said locking pin receiving groove of said latching block, providing a second electrical signal.

11. A method for locking a rear set of steerable wheels in a straight-ahead direction and for unlocking the rear set of steerable wheels in a vehicle having a front set of steerable wheels and a rear set of steerable wheels, said method comprising the steps of:

(a) providing actuatable locking means operatively connected to the rear set of steerable wheels and the vehicle frame for, when actuated and when the rear set of steerable wheels are in a straight-ahead direction, locking the rear set of steerable wheels in the straight-ahead direction;

(b) sensing if the rear set of steerable wheels are locked or unlocked and providing a signal indicative thereof;

(c) providing means for steerably moving the rear set of steerable wheels left and right of a straight-ahead direction;

(d) providing a first signal to actuate the locking means in response to a first control signal and providing a second signal to unlock the rear set of steerable wheels in response to a second control signal; and

(e) if, after providing the second signal to unlock the rear set of steerable wheels and sensing the rear set of steerable wheels is not unlocked, controlling the steerable moving means so as to attempt to steer the rear set of steerable wheels away from the straight-ahead direction for a predetermined time period.

12. A method for controlling a steering apparatus for a vehicle of the type having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said method comprising the steps of:

(a) providing a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle;

(b) effecting steering movement of the front set of steerable wheels through the front steering assembly in response to turning of the vehicle steering wheel;

(c) providing a controllable rear steering assembly connected to the rear set of steering wheels;

(d) effecting steering movement of the rear set of steerable wheels through the rear steering assembly in response to a rear steering control signal;

(e) selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

(f) sensing steering angle of the front set of steerable wheels and providing a signal indicative thereof;

(g) sensing steering angle of the rear set of steerable wheels and providing a signal indicative thereof;

(h) providing said rear steering control signal to effect the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the signal indicative of the steering angle of the front set of steerable wheels;

(i) effecting a change from one steering mode to another steering mode in response to a change in the selected steering mode only after the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction;

(j) sensing vehicle speed and providing a signal indicative thereof;

(k) selecting a rear wheel steering lock speed value such that when sensed vehicle speed is greater than the selected rear wheel steering lock speed value, it is desirable to maintain the rear steerable wheels in a straight-ahead direction;

(l) providing actuatable locking means operatively connected between the vehicle frame and the rear set of steerable wheels for, when actuated and when the rear set of steerable wheels is in the straight-ahead direction, locking the rear set of steerable wheels in a straight-ahead direction, and actuating said locking means when the vehicle speed is sensed to be greater than the selected rear wheel steering lock speed value;

(m) deactuating said locking means after sensed vehicle speed decreases below a second predetermined value less than the selected rear wheel steering lock speed value;

(n) sensing if, upon deactuation of said locking means, said locking means has unlocked the rear set of steerable wheels from the vehicle frame and providing a signal indicative thereof; and

(o) if, after deactuating said locking means it is sensed that the locking means has not unlocked the rear set of steerable wheels from the vehicle frame, providing the rear steering assembly with a rear steering control signal for a predetermined time period.

13. A method for controlling a steering apparatus for a vehicle of the type having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said method comprising the steps of:

(a) providing a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle;

(b) effecting steering movement of the front set of steerable wheels through the front steering assembly in response to turning of the vehicle steering wheel;

(c) providing a controllable rear steering assembly connected to the rear set of steering wheels;

(d) effecting steering movement of the rear set of steerable wheels through the rear steering assembly in response to a rear steering control signal;

(e) selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

(f) sensing steering angle of the front set of steerable wheels and providing a signal indicative thereof;

(g) sensing steering angle of the rear set of steerable wheels and providing a signal indicative thereof;

(h) providing said rear steering control signal to effect the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the signal indicative of the steering angle of the front set of steerable wheels;

(i) effecting a change from one steering mode to another steering mode in response to a change in the selected steering mode only after the rear steerable wheels are sensed to be within a predetermined angle of a straight-ahead direction;

(j) sensing if, upon actuation of the locking means, the rear set of steerable wheels is locked to the vehicle frame and providing a signal indicative thereof; and

(k) if it is sensed that after actuation of the locking means the rear set of steerable wheels is not locked to the vehicle frame, providing the rear steering assembly with a rear steering control signal so as to steer the rear steerable wheels toward a straight-ahead direction.

14. The method of claim 13 further including the steps of effecting a reversal of the steering direction of the rear steerable wheels if it is sensed that the rear set of steerable wheels are sensed to have passed the straight-ahead direction and that the rear set of steerable wheels is not locked to the vehicle frame.

15. A method for steering a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said method comprising the steps of:

(a) providing a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle;

(b) effecting steering movement of the front set of steerable wheels through the front steering assembly in response to turning of the vehicle steering wheel;

(c) providing a controllable rear steering assembly connected to the rear set of steering wheels;

(d) effecting steering movement of the rear set of steerable wheels through the rear steering assembly in response to a rear steering control signal;

(e) selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

(f) sensing steering angle of the front steerable wheels and providing a signal indicative thereof;

(g) sensing steering angle of the rear steerable wheels and providing a signal indicative thereof;

(h) sensing vehicle speed and providing a signal indicative thereof;

(i) providing actuatable locking means connected to the vehicle frame and to the rear set of steerable wheels for, when actuated and when the rear set of steerable wheels are in a straight-ahead direction, locking the rear set of steerable wheels in the straight-ahead direction;

(j) selecting a rear wheel steering lock speed value such that when the vehicle speed is sensed to be greater than the rear wheel steering lock speed value, it is desirable to prevent the rear steerable wheels from further steerable movement;

(k) controlling the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the sensed steering angle of the front set of steerable wheels;

(l) actuating the locking means when the sensed vehicle speed is greater than the selected rear wheel steering lock speed value;

(m) deactuating the locking means after sensed vehicle speed decreases below a second predetermined value less than the value used to actuate the locking means;

(n) sensing if, upon the step of deactuating the locking means, the locking means has unlocked the rear set of steerable wheels from the vehicle frame and providing a signal indicative thereof; and

(o) after the locking means is deactuated but the locking means is sensed to not be unlocked, providing the rear steering assembly with the rear steering control signal for a predetermined time period.

16. A method for steering a vehicle having a front set of steerable wheels and a rear set of steerable wheels arranged in tandem, each of the steerable wheels steerably secured to a vehicle frame, said method comprising the steps of:

(a) providing a front steering assembly connected to the front set of steerable wheels and to a steering wheel of the vehicle;

(b) effecting steering movement of the front set of steerable wheels through the front steering assembly in response to turning of the vehicle steering wheel;

(c) providing a controllable rear steering assembly connected to the rear set of steering wheels;

(d) effecting steering movement of the rear set of steerable wheels through the rear steering assembly in response to a rear steering control signal;

(e) selecting one of a plurality of steering modes including (i) front wheel only steering, (ii) crab steering, and (iii) curl steering;

(f) sensing steering angle of the front steerable wheels and providing a signal indicative thereof;

(g) sensing steering angle of the rear steerable wheels and providing a signal indicative thereof;

(h) sensing vehicle speed and providing a signal indicative thereof;

(i) providing actuatable locking means connected to the vehicle frame and to the rear set of steerable wheels for, when actuated and when the rear set of steerable wheels are in a straight-ahead direction, locking the rear set of steerable wheels in the straight-ahead direction;

(j) selecting a rear wheel steering lock speed value such that when the vehicle speed is sensed to be greater than the rear wheel steering lock speed value, it is desirable to prevent the rear steerable wheels from further steerable movement;

(k) controlling the steering of the rear set of steerable wheels in response to the selected steering mode and in response to the sensed steering angle of the front set of steerable wheels;

(l) actuating the locking means when the sensed vehicle speed is greater than the selected rear wheel steering lock speed value;

(m) initially causing said rear steerable wheels to be steered to a straight-ahead direction independent of the selected steering mode and independent of the sensed vehicle speed;

(n) sensing if, upon the step of actuating the locking means, the locking means has locked the rear set of steerable wheels to the vehicle frame and providing a signal indicative thereof; and

(o) after actuating the locking means and sensing the locking means has not steerably locked the rear set of steerable wheels to the vehicle frame, providing the rear steering assembly with the rear steering control signal so as to steer the rear steerable wheels toward a straight-ahead direction.

17. The method of claim 16 further including the steps of effecting a reversal of the steering direction of the rear steerable wheels if, after being steered to the straight-ahead direction, the locking means is sensed to have not locked and the rear set of steerable wheels are sensed to have passed the straight-ahead direction.