VIRTUAL PROTOTYPING OF ELECTRICAL THSA FOCUSED ON MECHANICAL POWER TRANSMISSION FUNCTIONS

Trimmable horizontal stabilizer actuator (THSA) system is a safety-critical system for flight controls. It is not accepted that the THS steering is free to vary under airload which would cause a total loss of control of aircraft pitch in case of actuation fail to fault. The preferred ultimate response to a THSA fault consists in freezing its position by designing a so-called fail-freeze actuator. This is achieved by combining specific mechanical functions in the power paths and loads. However, very little literature has introduced these functions and addressed the modelling and simulation activities from a system-level point of view. This paper addresses the system-level virtual prototyping of an electrical THSA, which is also a type of redundant electromechanical actuator (EMA) for more electric aircraft. Emphasis is put on the modelling and simulation of mechanical functions that are involved to get a fail-freeze design. The models are developed with resort to the Bond Graph formalism, considering their technical realization with both power and signal views. A particular attention is paid to the models' architectures, interfaces and causalities to facilitate the reuse, integration and implementation of the models, in any relevant simulation platform.