Comparison of a Modal-Expansion- and a Finite-Element-Model for a Two-Beam Flexible Robot Arm

Abstract For the investigations the motion of a robot arm consisting of two equal elastic beams is separated in rigid body motion and displacements due to distributed flexibilities. Movement was allowed only in one plane not taking into account gravity. The links were modelled as Bernoulli-beams with constant cross sections and density. The results, obtained by time integration, show the main problems of the application of both methods: Using modal-expansion-methods it is difficult to find the best shape functions and best combination of them for all kinds of motion. The application of clamped-free eigen functions only does not lead to satisfactory results. Using finite-element-methods the biggest problem is the high calculation time.