A Unified Hybrid Control Approach to Maximum Endurance of Aircraft

Unmanned air vehicles and urban air mobility have driven the need for the development of new algorithms for flight management systems. However, for certification, there is a strong desire to compare the new algorithms with the ones used for more conventional aircraft such as turbofan fixed-wing vehicles. With this need in mind, the main contribution of this chapter is to propose a unified approach for the maximum endurance of turbojet, turboprop, turbofan, and all-electric aircraft. This chapter details the two main steps to achieve this goal. First, a unified model of energy-depletion dynamics encompassing both fuel-burning and all-electric aircraft is developed. Next, using the unified energy model, the problem of maximum cruise endurance is formulated in a unified framework for all aircraft configurations and for a flight with three phases: climb, cruise, and descent. The problem is formulated and solved using hybrid optimal control in conjunction with the unified energy model. The general solution is then applied to turbojet, turbofan, turboprop, and all-electric aircraft. Simulation results are provided for a turbofan and a turboprop aircraft. Conclusions compare the results and summarize the most important findings.