Force feel actuator with limited proportional/integral error feedback

Claim 1

An aircraft control stick force feel actuator system comprising: an electrically controlled, hydraulic pressure control servo valve; a hydraulic actuator connected to the control stick and operable in response to differential fluid pressure applied to opposite ends of the actuator to provide a force to the stick having a magnitude and direction proportional to the fluidic pressure applied to the actuator, said hydraulic pressure being applied to the actuator in response to said servo valve; means responsive to the pressure applied to each end of said hydraulic actuator to provide a pressure signal indicative of the pressure difference therebetween; signal processing means for generating a force signal indicative of a raw force command corresponding to a desired force on the control stick, responsive to said force signal and to said pressure signal for providing a force error signal indicative of the difference between said pressure signal and said force signal, for integrating the force error signal to provide an integral feedback signal, and for providing a force command signal indicative of the summation of the integral feedback signal and the force signal; means providing a proportional error signal as the sum of a first proportion of said force command signal and a second proportion of said pressure signal, said second proportion being a fraction of said first proportion; and means responsive to said proportional error signal for providing a force commanding input signal to said electrically controlled, hydraulic pressure control servo valve.