Communications: electrical – Land vehicle alarms or indicators – For trailer
Reexamination Certificate
2001-01-16
2001-09-18
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
For trailer
C340S671000, C701S070000, C701S041000, C701S042000, C701S043000, C701S044000
Reexamination Certificate
active
06292094
ABSTRACT:
TECHNICAL FIELD
This invention relates to steering control systems for automotive vehicles with front and rear wheel steering. More specifically, this invention relates to computer control systems for assisting the operator in backing-up a vehicle-trailer combination when the vehicle has driver-operated front wheel steering and on-board computer-controlled rear wheel steering.
BACKGROUND OF THE INVENTION
Automotive vehicles with coordinated front and rear wheel steering systems are known. In modern applications, such steering systems may be used, e.g., in relatively large sport utility vehicles or trucks. The operator retains control over the steering of the vehicle's front wheels, and a vehicle computer-based system controls steering of the rear wheels. For example, one rear wheel steering system includes an electric motor-driven, rack and pinion rear-wheel-steer actuator that, upon computer command, produces a desired rear-wheel-steer angle to enhance the handling and maneuverability of the vehicle.
When the steerable rear wheels are set at an angle to the same side of the longitudinal axis of the vehicles as the front wheels, the system is considered to be providing “in-phase” rear wheel steering. “Out-of-phase” steering, conversely, is where the rear wheels are disposed to the opposite side of the vehicle longitudinal axis from the front wheels. Out-of-phase rear wheel steering markedly shortens the turning radius of a large vehicle. The on-board steering controller determines the rear-wheel-steer angle as a function of vehicle speed and the operator hand steering-wheel angle. The system, in general, will provide an out-of-phase steering angle at low vehicle speed to reduce the turning radius of a vehicle and in-phase steering at high vehicle speed to enhance directional stability.
The steering controller, thus, continually monitors vehicle speed, forward or reverse, and the angles, right or left, of the steered wheels with respect to the longitudinal axis of the vehicle. The controller also determines the yaw rate (i.e., the turning motion) of the vehicle in setting the steering angle of the rear wheels. While the front wheels may be steered at angles, e.g., from +33° (left) to −33° (right) with respect to the vehicle axis, the steering range of the rear wheels is usually smaller, e.g., from +12° to −12°. In steering the front wheels, the operator typically can rotate the hand wheel up to about 540° in either direction from its wheel centered position.
Larger automotive vehicles are often used to pull trailers, and sometimes it is necessary for the operator to back up the vehicle-trailer combination. Backing-up a front wheel steering vehicle is now within the experience and skill of vehicle operators who need to perform such jobs. But performing the same task with a vehicle-trailer combination is counterintuitive and not within common experience. It is an object of this invention to provide a computer-based, driver-interactive process to assist in backing-up a vehicle-trailer combination with the aid of rear wheel steering.
SUMMARY OF THE INVENTION
The invention is a driver interactive, driver advisor process that is performed largely on an on-the-vehicle microprocessor which generally would also be employed for control of the rear wheel steering.
The invention is applicable to a vehicle having rear wheels that can be steered through a reversible electric motor, and rack and pinion gearing, commanded by a suitably programmed microprocessor (a controller). The controller utilizes a sensor of a known type to measure the rear wheel angle, &dgr;
r
, with respect to the vehicle axis. The vehicle has a hand steering wheel by which the operator controls the steering of the front wheels. The controller needs to know the angular position of the front wheels. This is suitably accomplished using a steering wheel position sensor and estimating the front wheel angle, &dgr;
f
, based on the input of the steering wheel sensor divided by the ratio of the steering gear. The vehicle also includes a trailer hitch for receiving the tongue of a trailer. The hitch includes a sensor for providing the angle of the trailer tongue or hitch to the longitudinal axis of the vehicle, &thgr;
0
, to the controller. The direction of the trailer is determined by the direction of its fixed tongue.
As stated, the vehicle includes a microprocessor-based controller for using the appropriate sensor signals for controlling the electric motor-driven rear wheel steering and, additionally, performing the computations and algorithm steps for the control of vehicle-trailer backup. The controller needs to know vehicle travelling speed (forward or reverse), v
x
, which may be obtained from a special sensor or, as is often the case, from a brake system control module or by direct measurement of prop-shaft pulses.
As will be described, the controller will also actuate the issuance of commands to the vehicle operator during the execution of the process of this invention. The unit broadcasting or issuing such commands will sometimes be referred to in this specification as “Driver Advisor.”
In the practice of the invention, the driver of a vehicle-trailer combination activates the controller when the driver wishes to receive aid in trailer backing or parking. Upon completion of the backing process, this aspect of the controller functions is shut off until needed on another trailer backing situation.
When the process is initiated by the driver, the vehicle-trailer combination has current front and rear wheel angles and a hitch angle reported to the controller by the respective sensors. The vehicle is then stopped or backing slowly. The controller system then performs calculations to determine whether the current hitch angle, &thgr;
0
, exceeds the maximum permissible hitch angle, &thgr;
0
max
, that can be overcome, while continuing to backup, utilizing the full capability of the front and rear steering. The maximum hitch angle, &thgr;
0
max
, is a function of the maximum wheel angles, the wheel base and track of the vehicle, the distance from the vehicle rear axle to the hitch, and the trailer tongue length. This inquiry by the controller is referred to in the following specific embodiment section of this specification as Criterion 1. If the current hitch angle is larger than the maximum permissible hitch angle, the answer to the inquiry is “yes” and Criterion 1 is met. The process then requires a “pull forward” mode. The controller actuates the Driver Advisor to prompt the driver to pull the vehicle forward to reduce the hitch angle. The controller continues to receive sensor signals and assess the changing current hitch angle until this criterion is not met, and the “pull forward” mode is cleared.
If Criterion 1 is not met or after a pull forward mode is cleared, the controller issues a command to the Driver Advisor to prompt the driver to first center the steering wheel and then steer such that the front wheel angle, &dgr;
*
f
, is in the direction and amount where the driver would steer during backing toward the target position if without towing a trailer. Based on the driver's steering decision of the front wheel angle, &dgr;
*
f
, the controller system determines a desired hitch angle, &thgr;
*
, that must be achieved in order to comply with the driver-determined front wheel angle.
The controller system now calculates the maximum allowed front steering wheel angle, &dgr;
f max
, for achieving the desired hitch angle without counter steering of the front wheels. The controller calculates to determine this maximum value allowed for the driver's command of the front wheel angle such that with a potential available assist of a given maximum rear wheel steering angle, the trailer can be backed to where the driver wants to put it. The controller then determines whether the driver's front wheel angle command, &dgr;
*
f
, (in road wheel angle) is beyond this maximum allowed front wheel angle, &dgr;
f max
. This is referred to here as Criterion 2. If the driver's command exceeds
Chin Yuen-Kwok
Chin-Woei Lin William
Deng Weiwen
Lee Yong Han
Rule David S.
General Motors Corporation
Grove George A.
Hofsass Jeffery
Previl Daniel
Sedlar Jeffrey A.
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