Determination of constraint forces for an offshore crane on a moving base

Abstract

In this paper we propose an efficient method for calculating the forces of constraints in an open-chain multibody system, like a robot mounted on a vehicle with 6 degrees of freedom. The dynamical model is based on Kane's equation of motion, where screw theory is used to calculate the projection matrices from the link twists of the multibody system. This leads to a general modeling procedure relying on screw transformations that is presented in the paper. The procedure for determination of the constraint forces is given as an extension of the dynamical model and can be implemented after the equations of motion have been formulated and solved. We implement the described method for the specific case of a vessel with a heavy crane, and provide the simulation results. The method provides a basis for future work on the detailed modeling of friction in the joints of serial link mechanisms, and on the evaluation of potential fatigue consequences of different control solutions.