Optimal power management and mission profile for a Hybrid Aircraft

The paper focusses on a methodology developed to determine both mission parameters and power management for a generic Hybrid aircraft in such a way its energy consumption and/or flight time can be minimised. In fact the system dynamics of a Hybrid aircraft has generally one or more degree of freedom, when compared to a conventional one, related to the number of energy (or power) sources present on board with the consequences that classic solutions of mission analysis (e.g. climb rate that minimise the burn fuel) can be no longer valid. The approach adopted in this study is to couple mission perfomance analysis to optimal control methods so that the core mathematical problem is reduced to an optimiziation problem that aims at finding optimal values for certain control variables in such a way an arbitrary objective function can be minimized in presence of a certain set of constraints deriving from limitations of both flight envelope and propulsion operating conditions. To fully characterize the problem, the optimal contol algorithms are coupled to a simulator developed in house to model the operating characterisitic of a generic Hybrid powertrain. The simulator, based on Objected Oriented Paradigm, consists of modules that are used to describe the operation conditions (in terms of efficiency map and delivered Power/Energy) of each powertrain component. Subsequently, those modules can be assembled together to model either a Serial or a Parallel architecture, with several possible power sources: batteries, Combustion Engine, Fuel Cell. Two optimal control approaches (Single Phase and Multi-Phase) have been tested on a Hybrid Electric study case considering different objective functions, namely minimum energy, minimum fuel (when a Combustion Engine is considered) and minimum time. Prelimiary results show an agreement of both the Single-Phase and Multi-Phase approaches. In addition, both the power management and the mission profile differ greatly at varying the considered objective function.