Optimization-based Feedforward Path Following for Model Reference Adaptive Control of an Unmanned Helicopter
This paper addresses an optimization based approach to follow a geometrically defined path by an unmanned helicopter. In particular, this approach extends reference model following concepts. Instead of using vehicle dynamics, the optimization is based on the reference model of the controller. This way, we can calculate the time-wise evolution on the path by means of dynamic optimization. The progression on the geometric path, namely the timing law, is defined as a dynamic system subject to an additional virtual control input. The inputs of the reference model and that of the timing law are the decision variables used in the dynamic optimization. It will be shown that this way, an accurate following of the path is possible although the actually identified flight mechanical model is limited to a linear hover model. Furthermore, the approach allows to take constraints on inputs and states into account. Simulation results as well as preliminary flight tests conducted with the ARTIS testbed are presented for two nonlinear and planar paths underlining that good performance and constrains satisfaction can be achieved.