Generating Oscillations on UAVs with the Modified Relay Feedback Test in Outdoor Environments

Adaptation of control parameters in response to external effects or parametric changes is one of the basic capabilities required for high-performance unmanned aerial vehicle (UAV) applications. Adaptation can be done using forced excitations of the unknown UAV dynamics. In this work, we investigate the application of the modified relay feedback test (MRFT) to identify UAV dynamics in outdoor environments. In particular, we focus on UAVs using GPS for positioning and flying in the presence of external wind. The wind is introduced to the nonlinear UAV model and the resultant dynamics are analyzed. MRFT is also introduced to the position control loops to generate oscillations. The experimental results show that MRFT can be used to generate oscillations in outdoor environments. Some recommendations are given for the subsequent use of oscillations for identification and tuning.