Abstract: A hitch control system generates a rockshaft valve control signal as a function of sensed draft force, rockshaft position and operator input. Periodically, an auxiliary or disturbance signal of certain amplitude, frequency and duration is superimposed on the valve command signal. A calculated soil/implement gain is derived from components of the valve command signal and the measured draft force which have certain phase relationships with the disturbance signal. An electronic gain is modified so that the overall soil/implement gain remains substantially constant.

Abstract: A tractor-mounted hitch is movable to control the working depth of an implement in response to control signals generated by a model reference adaptive control system. The control system senses draft force and rockshaft position and receives operator-controlled reference signals representative thereof. A model reference adaptive draft control signal is derived from a model error signal, an adaptive gain value and a compensated position feedback term. A position error control signal is also generated. One or the other of the control signals is used to control the implement, depending upon whether or not the implement is in the ground and depending upon the relationship of the control signals.

Abstract: The invention provides an improvement in a conventional recoil system comsing a piston-cylinder arrangement, wherein a piston driven by recoil energy forces hydraulic fluid out of the cylinder through an orifice to dissipate recoil force. The invention provides an additional flowpath for hydraulic fluid, which contains a servo valve for controlling the pressure in the cylinder so that the desired recoil peak pressure/time curve can be achieved for any firing impulse. The invention also includes sensors for measuring hydraulic fluid pressure and the initial velocity of the recoiling parts imparted by the firing impulse, and a controller means including a microprocessor for calculating or determining the desired peak pressure based on this initial velocity and available recoil distance and transducers for measuring any variation of pressure from the desired peak pressure and applying an appropriate voltage to the servo valve to control the pressure and achieve the desired peak pressure during the recoil cycle.