Gust alleviation control system of flexible aircraft considering rudder efficiency

The rudder surface effectiveness loss directly affects the gust alleviation effect of flexible aircraft, considering the rudder surface effectiveness loss is the key to the design of an active gust alleviation control system. In order to tackle the issue of gust interference in flexible aircraft, a high aspect ratio flexible aircraft model is utilized to create a structural dynamics model of the flexible aircraft that takes into account elastic modes and rigid body motion. Additionally, the rudder effectiveness loss of the rudder surface actuator is taken into consideration. An adaptive observer is designed to estimate the efficiency factor of the rudder surface actuator online in real-time, reconstruct and solve the adaptive active fault-tolerant $H_{\mathrm{\infty }}$ controller, and achieve aircraft gust load alleviation. Under discrete and continuous gust excitation, simulation of the aircraft’s open/closed loop time domain response demonstrates that both $H_{\mathrm{\infty }}$ control and proportional-integral-derivative (PID) control can achieve better alleviation effects under the rudder surface ineffective energy loss, and that $H_{\mathrm{\infty }}$ control’s response time is faster than PID control’s. Under the rudder efficiency loss, the adaptive observer can complete the efficiency factor evaluation in less than 4 seconds, and the $H_{\mathrm{\infty }}$ controller, which is designed based on this efficiency factor, can achieve gust alleviation that is comparable to the ideal scenario.