Implementation of CAPIO for Composite Adaptive Control of Cross-Coupled Unstable Aircraft

Abstract

This paper presents an implementation of a recently developed control allocation algorithm CAPIO (a Control Allocation technique to recover from Pilot Induced Oscillations) for composite adaptive control of an inertially cross coupled unstable aircraft. When actuators are rate-saturated due to either an aggressive pilot command, high gain of the ight control system or some anomaly in the system, the phase shift between the desired and the actual aircraft outputs and the eective time delay can increase. This eective time delay may degrade the performance or, depending on the severity of rate saturation, even destabilize the closed-loop system. The CAPIO reduces the eective time delay by minimizing the phase shift between the commanded and the actual attitude accelerations. While the original intent of CAPIO was to mitigate pilot induced oscillations, we have also found that CAPIO can help automatic ight controllers, in particular, adaptive ight controllers, avoid and recover from similar conditions caused by rate saturation eects. In the paper we report simulation results for a challenging scenario of an unstable aircraft with cross-coupling controlled by a composite adaptive controller in the presence of rate saturation. The simulations conrm the capability of CAPIO to serve as an eective rate saturation compensator in adverse conditions.