Multibody Dynamics

Abstract

Due to the operation of the rotor, the helicopter is subject to important vibration levels affecting namely the fatigue of the mechanical parts and the passenger comfort. Suspensions between the main gear box (MGB) and the fuselage help to filter theses problematic vibrations. Their design can be difficult since the filtering should be efficient for different types of external forces (pumping force and roll/pitch torque) which may appear during the flight. As passive solutions classically show their limits, intelligent active solutions are proposed so that the filtering can be adjusted according to the vibration sources. Such studies still suffer from a lack of tools and methods, firstly, necessary to the design of complex mechanical systems (due to their multi-phase multi-physics multi-interaction characteristic, ...) and secondly, to develop of an intelligent joint. The main objective of this chapter is to provide a methodology for designing and analyzing an intelligent joint using an energetic representation approach: the multibond graph (MBG). This method is applied here to a complex mechanical system with closed kinematic chains (CKC) which is the joint between the main gear box (MGB) and the aircraft structure of a helicopter. Firstly, the MBG method is analyzed. Secondly, after a brief state of art of the MGB-Fuselage joint, developments focus on the 2D and 3D modeling of the MGB-Fuselage joint with a MBG approach. The 20-sim software is used to conduct the simulation of bond graph. Finally, the MBG models results are presented, illustrating the potential of the MBG tool to predict the dynamic of a complex CKC mechanical system.