Case Corporation

Donald D Carr

William L Schubert

Abraham Orbach

Steven W Seymour

Michael Stelzle

A hitch assembly control system for an off-highway vehicle such as an agricultural tractor is operable in both position and draft control modes. The control system is capable of transitioning from the position mode to the draft mode, and from the draft mode to the position mode, under particular conditions. For the transition from position to draft mode, these conditions include a target hitch position being greater than both a hitch position command and a hitch position feedback. For the transition from draft to position mode, these conditions include the hitch position command being greater than the hitch position plus a hysteresis factor, or less than the hitch position command that existed back at the transition into the draft mode.

Transition from position to draft mode controlled by hitch position

A system or method for controlling the position of an implement coupled to a work vehicle. The implement is moveable by a hydraulic positioning assembly including an actuator and a valve assembly which control the flow of fluid to the actuator in response to control signals. The valve assembly includes raise and lower valves, each valve requiring a control signal equal to a threshold value before the valve opens and fluid begins to flow. The system includes a sensor to detect the position of the implement and a control circuit. In response to a change in a position command, the control circuit applies a control signal to the appropriate raise or lower valve based upon the respective threshold value. The control signal may include a component for moving the implement at a desired rate of movement. After undesirable implement movement is detected, the control circuit modifies the threshold value. The modification may occur when the control circuit detects that the implement is moving at an excessive rate due to the effects of valve hysteresis and implement weight. The control circuit may detect the undesirable movement by determining that the position error value is more negative than a predetermined value. The modified threshold value then replaces the threshold value for subsequent implement movement. The new threshold value prevents the undesirable movement in subsequent implement movement.

Threshold current control system for hydraulic valves

A system or method for controlling the position of an implement coupled to a work vehicle. The implement is moveable by a hydraulic positioning assembly including an actuator and a valve assembly which control the flow of fluid to the actuator in response to control signals. The valve assembly includes raise and lower valves, each valve requiring a control signal equal to a threshold value before the valve opens and fluid begins to flow. The system includes a sensor to detect the position of the implement and a control circuit. In response to a change in a position command, the control circuit applies a control signal to the appropriate raise or lower valve based upon the respective threshold value. The control signal is generated by using a predetermined gain. When undesirable implement movement such as an overshoot condition is detected, the control circuit modifies the gain value. The modified gain value is used to generate subsequent control signals for actuating the implement.

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Valley City, ND, United States of America

Donald D Carr