Control Of Helicopter Parallel Hybrid Propulsion System

Abstract

Helicopter and engine manufacturers have been conducting R&T work for several years to design and improve parallel hybrid-electric propulsion system for rotorcrafts. A significant part of the benefits of hybridization is directly dependent on the control system. The hybrid power sharing control solution presented herein is designed as an integral control system of an electrical and a turboshaft engine, powering the helicopter main gearbox in parallel. The present paper elaborates the numerous concurrent objectives and mandatory constraints the hybrid propulsion system must fulfill. Then a global control architecture is proposed to handle all this objectives and to tackle possible conflicts by priorization logics. Finally, illustrating results obtained on a representative hybrid engine test bench are presented. The first case study deals with the safeguarding of the propulsion battery's energy. The second test scenario focuses on the automatic takeover of the backup electrical engine after an in-flight shut down of the main turboshaft engine. The control concept highlighted here offers interesting flexibility in managing multiple objectives and minimizes the risk of adverse interaction between the two power sources.