A way to mitigate force-fight oscillation based on pressure and position compensation for fly-by-wire flight control systems

Abstract

This paper focuses on force-fight oscillation mitigation in fly-by-wire (FBW) flight control systems (FCSs) for civil aircraft. The theory of "force fight" was first introduced after analyzing its impact on active-active actuators system. The architecture of one typical FBW FCS and the layout of an electronic hydraulic servo actuator (EHSA) were described. A force-fight mitigation algorithm applying pressure and position compensation feedback was then presented. To validate algorithm performance, an associated actuator-surface model was created to simulate force fight. Finally, the algorithm was tested using worst-case scenarios by calculating the system latency and tolerance, and verified using special "Iron Bird" tests. The results show an obvious decrease in the difference delta press (DDP) when comparing with/without mitigation, and thereby meeting force fight limitation requirements.