Fault Tolerant Control of an Experimental Flexible Wing

Active control techniques are a key factor in today’s aircraft developments to reduce structural loads and thereby enable highly efficient aircraft designs. Likewise, increasing the autonomy of aircraft systems aims to maintain the highest degree of operational performance also in fault scenarios. Motivated by these two aspects, this article describes the design and validation of a fault tolerant gust load alleviation control system on a flexible wing in a wind tunnel. The baseline gust load alleviation controller isolates and damps the weakly damped first wing bending mode. The mode isolation is performed via an H 2 -optimal blending of control inputs and measurement outputs, which allows for the design of a simple single-input single-output controller to actively damp the mode. To handle actuator faults, a control allocation scheme based on quadratic programming is implemented, which distributes the required control energy to the remaining available control surfaces. The control allocation is triggered in fault scenarios by a fault detection scheme developed to monitor the actuators using nullspace based filter design techniques. Finally, the fault tolerant control scheme is verified by wind tunnel experiments.