Motor vehicles – Steering by driving – Auxiliary steering motor
Reexamination Certificate
1999-12-09
2001-10-09
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering by driving
Auxiliary steering motor
C180S009440, C701S041000, C192S03000R
Reexamination Certificate
active
06298931
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a tracked vehicle drive/steering system.
When operating a vehicle, it is desirable for the operator to be able to perceive the turning status of the vehicle and/or to prevent unintentional vehicle turning upon initiation of vehicle motion. For example, when an operator starts a vehicle moving, it is desirable that the operator be able to know whether or not the vehicle will begin turning as it starts to move. In most conventional tractors, it is possible to discern the turning status of the tractor by viewing the position of the steerable wheels. On most current production tracked vehicles, there are no steerable wheels, but there is a spring centered steering wheel, and the steering is centered unless the operator holds the steering wheel away from its centered position.
Recently, non-centered steering wheel input mechanisms have been proposed for tracked vehicles, such as described in U.S. Pat. No. 6,000,490. In a vehicle with such a mechanism there may be no indication of its turning status until the vehicle starts to move. Thus, an operator who has previously performed a counterrotation turn and then stops the vehicle for some time, may not remember the vehicle turning status upon resumption of vehicle motion. It would be undesirable for an operator to rapidly accelerate a vehicle, while believing it would travel straight, when in reality it would begin turning.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to provide a steering control system for a vehicle with a non-centered steering wheel which prevents or reduces the severity or likelihood of unintended turning upon rapid vehicle acceleration during startup.
These and other objects are achieved by the present invention, wherein a control system is provided for a tracked vehicle drive/steering system which has an engine driven hydraulic steering pump which drives a hydraulic steering motor. The steering pump is responsive to steering pump control signals, and an operator manipulated non-centered steering wheel generates steering pump command signals. A steering motor provides an input to a differential track drive mechanism which responds to manipulation of the steering wheel and drives left and right tracks, and turns the vehicle at turning rates which depend on the magnitude of the steering pump control signals. In one embodiment, the control system operates to gradually reduce the magnitude of the steering pump control signals if the vehicle is stationary, the clutch is engaged and these conditions persist for at least a certain time period, and to further or more rapidly reduce the magnitude if the vehicle seat is not occupied. In an alternate embodiment, the control system operates to limit the magnitude of the steering pump control signals as a function of the acceleration of wheel speed. In another alternate embodiment, the control system operates to quickly reduce the magnitude of the steering pump control signals if the vehicle is stationary, the clutch is engaged and the transmission is commanded to be in a non-neutral gear, between the time the gear is commanded and the vehicle motion begins.
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National Semiconductor, LM628/LM629 Precision Motion Controller, Feb. 1995, 1 page.
Deere & Company
Johnson Brian L.
Lerner Avraham H.
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