Title: Automatic steering system for standing-crop harvester

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Abstract: A standing-crop harvester has a chassis adapted to be displaced along the ground in a transport direction and carrying a pair of guide wheels which are normally controlled from a steering wheel. A sensor carried on an arm in front of the machine detects the edge of a swath in a standing crop and generates an output which varies the impedance of one element of a bridge circuit. Another element of this bridge circuit has its impedance varied in accordance with inclination of the harvester on the ground, another element is varied in accordance with the speed of the harvester on the ground, and a fourth element is varied in accordance with the position of the wheels of the harvester relative to the direction of travel. A zerovoltage detector connected across this bridge operates an electromechanical valve which steers the vehicle automatically, compensating for inclination of the ground under the harvester and speed of the harvester along the ground, and using the feedback signal from the wheel positions so as to accurately guide the harvester along the edge of the swath. The steering wheel is provided with an electrical capacitative sensor which shuts off the automatic steering system immediately when the operator touches the wheel so that he can readily take over manual operation of the machine. In addition a double check valve is provided between the power steering system and the hydraulic cylinder serving to steer the wheel so as to prevent rotation of the steering wheel when the automatic pilot is in operation.


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