![]() Within this field, there are two common methodologies to solve the motion of such a mechanical system. Modelling the control chain as well as the aerodynamic chain (two rigid mechanical sets of joints that form a closed-loop system of links) necessitates the use of parallel multibody dynamics. One of the other distinguishing features of this paper is that it suggests the importance of the control chain on the overall motion of the helicopter blades-something commonly overlooked in typical treaties on helicopter rotor dynamics, to list a few. They outline the utility of various methods: 1D + 2D solvers for quick, accurate results shell methods for flexible beams and bearingless rotors and 3D solid models to capture realistic beam effects. ![]() They use a model based on the variational asymptotic method, and include joints, modularity, and Lagrange multipliers for matrix sparsity. Laulusa and Bauchau review these methods in a more recent paper.īauchau, with Bottasso and Nikishkov examine a history of blade models and multibody methods. It is suggested that energy decaying methods provide unconditional stability, especially in the presence of constraints. He notes that energy preserving schemes have difficulty with high frequency numerical dissipation, which can cause convergence problems. Bauchau examines the matrix condition number for a system of equations due to the effects of Lagrange multiplier constraints. ![]() They discuss the addition of constraints and the destabilising effect adding rigid mechanisms has on a system. It also explains the difficulties with existing models: CAMRAD II and DYMORE are helicopter structural models that are expensive, difficult to expand, difficult to use and modify, and, for experimental purposes, restrictive in their generality.īauchau and Kang model the combined elastic and rigid body motion, rather than solving the body motions separately. In his paper, Lagrange multipliers provide the mathematical coupling between the hub and a blade system. There are quite a few papers specifically pertaining to helicopter multibody dynamics however, those of interest are the ones that incorporate the blade mechanics with the articulation, such as Agrawal, who explains a method for analysing the multibody blade dynamics with a full helicopter model. ![]() Since the impetus for the research contained herein is based on the multibody dynamics of a rotor hub, a brief outline of some of the work from the helicopter coupled mechanics provides context. Thus, a method to describe the parallel-chain mechanics of the rigid and elastic body system together is required. In this situation, the flexible rotor blades are connected to rigid linkages, which are additionally constrained to move as a closed-loop mechanism. Within the SHARCS program, an adaptive pitch link (APL) controls the vibrations transmitted from the rotor blades to the fuselage via a system of linkages that control the aerodynamics of the rotor. For example, this phenomenon is central to the smart hybrid active rotor control system (SHARCS) program at Carleton University, which seeks to experimentally and mathematically simulate devices to attenuate vibration and noise emanating from a helicopter hub. Numerically solving high-stiffness rigid bodies coupled with flexible elastic bodies is an important, but difficult, problem within computational dynamics. ![]()
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