Design of Decoupled and Dynamically Isotropic Parallel Manipulators With Five Degrees of Freedom

Abstract A six degree of freedom (DOF) two-radii Gough-Stewart Platform (GSP) can be designed to be dynamically isotropic and has been proposed for micro-vibration isolation. In many applications, the torsional mode can be ignored, and a 5-DOF dynamically isotropic, parallel manipulator capable of attenuating three translational (3T) and two rotational (2R) modes are sufficient. In this work, we present the design of a novel two radii, 5-DOF dynamically isotropic parallel manipulator, which can be used for vibration isolation purposes where the torsion mode can be ignored. We present closed-form solutions in their explicit form to this design problem, and these are obtained using a geometry-based approach. The first design is based on a modification to the two radii GSP and provides enhanced design flexibility and feasibility. The second design of a decoupled 5-DOF GSP is based on superposing two 3-DOF dynamically isotropic or decoupled parallel manipulators, which are the well-known 3-3 RPS parallel manipulators. The closed-form solutions for these 3-DOF isotropic designs are obtained. It is shown that the 5-DOF decoupled design have two translational modes, namely the (X, Y) modes, which are decoupled from two rotational modes (Rot(X), Rot(Y)) and are controlled by two different sets of three struts. This feature can lead to simpler control and less power requirements if active vibration control is chosen. The designs presented in this work include the effect of asymmetricity and payload’s centre of mass variation in the moving platform. The dynamically isotropic and decoupled designs obtained were successfully validated using the finite element software ANSYS®.