Multiobjective Parameter Optimization of an eVTOL Controller Incorporating Lead-Lag Filters for Increased Robustness

This paper outlines the methodology and findings of a parameter optimization process applied to an incrementel nonlinear dynamic inversion controller of an eVTOL vehicle. Considering a variety of soft and hard requirements with respect to the tracking performance, disturbance rejection, robustness and stability of the controlled system, a multiobjective optimization problem is formulated to optimize the controller gains and filter time constants. In addition to utilizing linear models, high-fidelity nonlinear models are employed in the optimization to ensure that the optimization results account for nonlinear effects like sensor errors, vibrations, absolute and rate limits. Furthermore, a detailed investigation into the influence of the proposed lead-lag filter is conducted demonstrating the advantages of the additional degrees of freedom in the controller tuning. The optimized controller is assessed in both simulation and flight tests, showcasing compelling performance in reference tracking and disturbance rejection while complying with all robustness requirements.