Gust alleviation H_∞ control law design and wind tunnel test for a high-aspect-ratio flexible wing

High-aspect-ratio aircraft are widely used in military and civilian fields, such as reconnaissance, surveillance, and attacks, due to their high lift-to-drag ratio, strong payload capability, significant endurance effect, and good stealth performance. However, compared to conventional aircraft, high-aspect-ratio aircraft are more susceptible to gust disturbances during flight. In response to this phenomenon, a full-scale dynamic model of a high-aspect-ratio unmanned aerial vehicle was developed. Considering the coupling among control surfaces, structural forces, and aerodynamic forces, along with sensor, actuator, and delay effects, an H_∞ control law was designed using the principle of singular value energy flow reduction and weighted function, with a PID(Proportional-Integral-Derivative) control law for comparison. The two controllers were then subjected to pulse-response and jury stability tests. Finally, wind tunnel tests were conducted to investigate the gust alleviation principle, in which gust disturbances were generated using gust generators and control surface self-excitation. The results present that the average wing root bending moment and wing tip overload under the PID control law decrease by approximately 30%, while under the H_∞ control law, both the average wing root bending moment and wing tip overload reduction rate exceed 50%, with peaks reaching 60%. This validates the feasibility and efficiency of the designed H_∞ controller.