Abstract: The industrial demand for high-performance and low energy consume has highlighted the need to develop lightweight manipulators and robots. However, their design and control result more difficult with respect to rigid-link robotic systems mainly due to the structural flexibility of the arms. To this end, the Equivalent Rigid-Link System (ERLS) approach for 3-D flexible link robots has been developed and, in this work, is considered in its recent developments. In particular, two recently published 3-D Equivalent Rigid-Link System formulations are discussed and compared by means of numerical simulations to highlight their strengths and possible weaknesses. The former deals with the Equivalent Rigid-Link System concept extension to spatial manipulators and robots through a Finite Element Method approach (ERLS-FEM), whereas the latter reformulates the model through a Component Mode Synthesis technique (ERLS-CMS). After the definition and discussion of the kinematic and dynamic equations, which account for the coupling between rigid-body and flexible-body motions, an extensive comparison is made. A benchmark manipulator is implemented and the formulations numerically compared
in terms of accuracy and computational load under different input conditions.