Abstract: A steering control system for a tracked vehicle includes an engine driven variable displacement steering pump which drives a hydraulic motor. The motor drives a differential drive mechanism which drives left and right track drive wheels. An electronic control unit, as a function of steering wheel position, vehicle speed, engine speed, forward/reverse vehicle direction and other parameters, generates a command signal which controls the swashplate of the steering pump. The system operates so that, for a given position of the steering wheel, a turn curvature of the vehicle decreases as vehicle speed increases, wherein turn curvature is inversely proportional to a radius of turn. This is accomplished by calculating a turn speed value equal to the vehicle speed multiplied by a ratio of a nominal engine speed divided by sensed engine speed, and by calculating the command signal equal to a steering gain value multiplied by a ratio of the turn speed value divided by a nominal vehicle speed value.

Abstract: A steering control system for a tracked vehicle includes a spring centered steering wheel which is rotatable in both directions to endstops. A steering control unit executes a transitional counter-rotation (TCR) mode algorithm which disables steering or counter-rotation when the gear lever moves from park to neutral or from park to neutral to gear while the clutch is disengaged. Steering function can be re-enabled by turning the steering wheel to its centered position and then turning the steering wheel in either direction away from its centered position, or by turning steering wheel towards one of its endstop positions (without centering the steering wheel). If steering or counter-rotating is enabled the second way, then during a transition period the turning rate as a function of the position of the steering wheel will be less than that of normal operation.