Abstract:

A feature of all the recent well-recorded severe pilot-induced oscillations (PIOs) is related to the presence of actuator rate limiting. Rate limiting has been shown as a main contributor to triggering the PIOs, which are classified as category II PIO. In this paper, approximate describing functions are introduced to describe the nonlinear feature of rate limiting. And inverse describing function techniques are employed to provide a prediction of the limit cycle or PIO frequency with a modern fly-by-wire fighter in the landing task. A new criterion is then used to predict category II PIO and is applied to the above fighter to predict PIO. Application of software rate limiters to the design of the fighter with PIO is demonstrated to prove that the stability and performance are improved.

Key words: Pilot Induced Oscillation, rate limiter, describing function, categoryII PIO criterion, softwarerate limiter