Two-input two-output port model for mechanical systems

Abstract

This paper proposes a double input output port transfer to model complex mechanical systems composed of several sub-systems. The sub-structure decomposition is revisited from the control designer point of view. The objective is to develop modelling tools to be used for mechanical/control co-design of large space flexible structures involving various substructures (boom, links of robotic arm,...) connected one to each other through dynamics local (actuated) mechanisms inducing complex boundary conditions. The double input output port model of each substructure is a transfer where accelerations and external forces at the connection points are both on the model inputs and outputs. Such a model : * allows to the boundary conditions linked to interactions with the other substructures to be externalized outside the model, * is defined by the only substructure own dynamic parameters, * allows to build the dynamic model of the whole structure by just assembling the double port models of each substructure. The principle is first introduced on a single axis spring-mass system and then extented to the 6 degress-of-freedom case. This generalization uses the clamped-free substructure dynamic parameters such as finite element softwares can provide.