Description

Adaptive Control Research and Flight Testing by Buddy Michini

For non-conventional flight vehicles, it is difficult to develop accurate dynamic and aerodynamic physical models. Some examples include flapping, indoor and miniature flight vehicles that typically operate at low Reynolds numbers and transition through distinct phases of flight. This variation in flight dynamics makes adequate control of the vehicle difficult or impossible using classical control techniques. One possible solution is to use adaptive techniques whereby a control algorithm adapts to changes in plant dynamics and attempts to correct the system's response to some desired reference model (model reference adaptive control, or MRAC).

A variant of standard MRAC, known as L1 adaptive control, includes a low-pass filter in the loop to limit the bandwidth of the control signal. While this algorithm shows good stability properties and transient performance guarantees, selection of the parameters to generate some desired reference performance is not immediately obvious. Current research is focused on developing optimization algorithms to select these parameters based on a multi-objective cost function incorporating stability margins, closed-loop performance, and hardware limitations. Using RAVEN, controllers can eventually be implemented and flight tested on vehicles such as the three-wing tailsitter below.