Abstract: A backlash eliminating device is provided in which two members are biased outwardly in opposite directions in an opening in a housing. Rotatable members with arcuate outer surfaces are connected through self-aligning bearings to these members and can rotate about transverse axes. The end of a crank arm at either end of the unit has an arcuate surface that engages the arcuate surface of one of the rotatable members. Self-aligning bearings, rotatable about axes transverse to the housing, connect the crank arm ends to the housing. The biasing force eliminates clearance at the bearings and the self-aligning bearings allow the crank arms to be slightly cocked without resulting in malfunction.

Abstract: A dual servo actuation system is automatically equalized or rigged by electronic control circuits. A static auto rigging bias is applied to one or the other, or both, of a pair of electro hydraulic servo valves that respectively control two hydraulic actuators driving a common member, such as an aircraft control surface. An auto rigging bias, which substantially eliminates force fight, is automatically generated and stored as a fixed quantity prior to use of the system for control of the common member. With a zero commanded output of the two actuators, a difference of differential pressures at the actuators is obtained and caused to change the number in a counter as long as the difference exceeds a threshold. The counter number, while it is above the threshold, is continuously applied as a bias signal to decrease the force fight, and the number in the counter is stored as a fixed bias signal when the force fight indicated by the difference of differential pressures drops below the threshold.