Dynamics of closed linked variable geometry truss manipulators

Abstract

This paper presents dynamical characteristics of a variable geometry truss (VGT) manipulator system which consists of a two-dimensional statically determinate truss for space applications. Formulation takes into account geometrical effects of the closed-link constraints, variable length mechanisms, rotational degrees of freedom at the joints and internal control forces; and is developed by Kane's dynamical equations. The conventional formulae of tree-like truss structures are extended to the procedure, which is adapted to statically determine truss structures using a Jacobian matrix derived by geometrical considerations. Inverse kinetics of the variable geometry truss have been formulated considering the minimum norm solution to the equations of motion. A two-dimensional variable geometry truss manipulator is simulated numerically as an example of activities on Space Station. Results show the effects of internal control forces on the attitude of the manipulator system in a space environment, and the characteristics of the inverse kinetics of the manipulator are investigated.