Optimal Control Allocation for Electric Aircraft Taxi Systems: A Preliminary Study

Demonstrators and research projects about electric aircraft taxi systems testify the current interest in low- or zero-emission ground propulsion technologies to lower the overall fuel consumption and emissions of commercial flights. Electric motors fitted in the main landing gears are one of the most promising layouts for these systems especially for narrow-body commercial aircraft. From a control theory point of view, the aircraft on ground becomes an over-actuated plant through adoption of this technology, i.e. a commanded ground trajectory can be reached through different combinations of actuator efforts. A strategy is required to choose the most suitable of these combinations in order to reach the best efficiency. This work aims to investigate a strategy for an optimal control allocation during path-following of prescribed ground trajectories. While the most obvious contributor to the optimizing cost function is energy efficiency, other aspects need to be considered such as the thermal behavior of the electric motors, the availability of energy storage systems resulting in a certain possible amount of regenerative braking, and other technical and normative constraints. Preliminary simulations of trajectory tracking based on the presented concept are shown.