1) Field of the Invention
The present invention relates generally to position control for agricultural implements and more specifically to an improved transducer arrangement for providing an electrical feedback signal to an electrohydraulic depth control system.
2) Related Art
Numerous systems are available for automatically controlling implement position. One such system is shown in U.S. Pat. No. 5,132,347, of common ownership with the present application. An electronic control unit (ECU), such as shown and described in U.S. Pat. No. 4,979,092, is utilized to control the trailing implement in response to input signals including a lever control signal, a position sensor signal and a draft force sensor signal. When the control input from the implement is plugged into the ECU, control is shut off to the 3-point hitch and automatically transferred to the trailing implement. An implement position sensor, such as a rotary potentiometer, is mounted on the towed implement to sense the position of the frame and tools relative to the wheels.
One problem encountered with such automatic position control of a trailing implement is providing a good feedback system which is accurate and supplies repeatable feedback signals so that implement position can be easily ascertained and repeated after the position control cylinder has been cycled. The depth control range for operating a tillage tool in the field-working position is usually a relatively small fraction of the overall range of vertical adjustment of the implement from the uppermost transport position to the lowermost field-working position. The normal depth control range for ground working operations of an implement such as a disk harrow may be several inches while the complete cylinder stroke results in frame movement of sixteen to twenty inches or more. Once the implement is lifted from the ground, returning the implement to the depth setting of the previous ground-working pass is dependant on the accuracy and repeatability of the feedback signal. Providing accurate and repeatable feedback from the implement, particularly when the depth control range is relatively small, has been a continuing source of difficulty.