A method for the dynamic analysis of planar multibody systems, which consist of interconnected rigid and flexible bodies, is presented. Instead of traditional angle coordinates, unit vector coordinates are suggested to represent the orientation of a body. It is much easier than the previous methods to drive equation of motion by using unit vector coordinates. Two sources of nonlinearities are considerd: geometric nonlinearities and inertia nonlinearities. Geometric nonlinearities are caused by large deflections, that is, nonlinear strain terms. Inertia nonlinearities result from the large amount of rigid body rotations of the system component.
A computer program has been developed based on the proposed algorithm and two examples have been solved. Through the analysis of the dynamic response of a simply supported beam, the proposed algorithm is verified as an accurate method. As a second problem slider-crank mechanism is simulated. As the driving speed increases, the geometric nonlinear effects become impotant. Also, the effect of the number of modes and finite elements on the dynamic response have been investigated.