Exact Linearization of Multibody Systems Using User-defined Coordinates

An exact approach to linearize the equations of motion of multibody systems is presented. The method has general applicability and it is well suited to linearize the index-3 Differential Algebraic Equations (DAE) governing the state of a dynamical system. Moreover, the method was extended to linearize a dynamical system in terms of user-defined coordinates without the need to reformulate the governing equations; this feature is of particular interest in disciplines like rotordynamics where eigensolutions are requested in terms of coordinates defined in a rotating frame.

Contrary to other linearization methods, the proposed approach implements a closed-form computation of the linearized equations of motion; all second order effects are taken into account and no numerical differentiation is required. The proposed method inflates the governing equations and then computes a set of sensitivities that provide the linearization of interest. The method is attractive because (a) it handles large heterogeneous problems, (b) it optionally linearizes a system in terms of user-defined coordinates, (c) it can be optimized using parallel algorithms, and (d) it provides a straightforward implementation in a general-purpose dynamics simulation code such as MSC.ADAMS.