Numerical Framework and Design Optimization of an Intrinsically Compliant 3-DOF Parallel Robot

Parallel robots are multiple degree of freedom (DOFs) systems which are typically used in applications characterized by enhanced accuracy, rigidity and large force requirements within a compact workspace. In the present research, an intrinsically compliant parallel robot with 3- DOFs, which is actuated by using four pneumatic muscle actuators (PMA) is conceptualized, developed and analyzed. Despite many benefits, parallel robots also offer certain challenges which arise from highly coupled and non-linear motion of their actuators. Small workspace of parallel robots has many singularities and solving a closed form forward kinematics for its end effector motion is complicated. The PMA are able to provide intrinsically compliant robotic motions; however, they are flexible, and their unilateral actuation poses constraints on the achievable DOFs. The present research focuses on analyzing kinematics and dynamics of the developed parallel robot encompassing the stiffness together with force closure analyses besides suggesting design improvements as a consequence of the singularity analysis. Design synthesis and multi-criteria optimization has been performed to obtain a robot design providing higher accuracies (near unity condition number), quick response to external wrench (stiffness and rigidity) and reduced actuator force requirements. SPEA2 (Improved Strength Pareto Evolutionary Algorithm) has been implemented to carry out simultaneous optimization of design objectives and provide Pareto optimal design solutions.