Multi criteria design of a spherical 3-DoF parallel manipulator for optimal dynamic performance

Since rapid positioning and high accuracy is an important characteristic of closed-chain manipulators, the design of parallel manipulator should satisfy this performance. Dynamic analysis and optimization problem of a Spherical 3-DoF Parallel Manipulator (SPM) is the main subject of this paper. Based on Lagrange method, the closed-form dynamic formulation of the mechanism is investigated. Using jacobian and generalized inertia matrix, Global Dynamic Conditioning Index (GDCI) is proposed to evaluate the manipulator behavior in task space. Optimization procedure is formulated as maximization of GDCI, applying a simple genetic algorithm subjected to a set of appropriate constraints. So, a multi-criteria optimization analysis including both kinematics and dynamics behavior is considered on which achieving the largest workspace, fewest singularities and appropriate dynamic performance are available. Optimization results are used to have an optimum design of Agile-wrist mechanism that is represented in relevant tables and graphs.