| 摘要 |
An electronic control for a vehicle supplementary hydrostatic front wheel drive includes a rear sensor for providing a command signal representative of the speed of differential connected, engine-driven, main drive wheels. A front sensor provides a feedback signal representative of the speed of the hydrostatic drive motors. The command signal is modified to provide a modified command signal to be summed with the feedback signal to provide servo circuitry with a servo signal which is representative of the front wheels being driven 3% slower than the rear wheels. Electrically actuated, pressure responsive clutches allow the front wheels to overrun the hydrostatic drive motors until the slip at the rear wheels exceeds 3%, then the front wheels drive to supplement the main drive wheels. A selectable overspeed circuit is provided which can modify the modified command signal to provide a servo control signal which represents the front wheels being driven 1% faster than the rear wheels so as to provide a continuous, positive supplementary drive regardless of rear wheel slip. The servo control signal is processed through direction controllers which input the direction of the main drive wheels and which supply control signals to a servo actuator on a reversible hydraulic pump which powers the hydrostatic drive motors for drive in accordance with main drive speed and direction. Both the servo and overspeed circuits are connected to a hold circuit which activates and holds the overspeed circuit on to provide quick response when the direction of the main drive is changed. |
