Optimal Design Of2-、3-、4-DOF High-speed Parallel Manipulators: Theory And Application

Driven by the exhaustive needs from pharmaceutical, logistics, and electronics,where pick-and-place operations at very high speed are the essential requirement, thisdissertation presents an integrated methodology for optimal design of2-,3-, and4-DOF Delta-like high-speed parallel manipulators, including kinematic and dynamicanalyses，dynamic dimensional synthesis，servomotor specification, and performancetests on two prototype machines. The following achievements have been acquired:A novel4-DOF parallel manipulator, named the Cross-IV, is invented. Themanipulator is of two moving platforms connected by slideways-leadscrew assembly,allowing a SCARA motion to be achieved, thanks to the elaborately designedmechanical structure of the moving platforms.A simplified model of rigid dynamics for each manipulator has been developed.Compared with their complete dynamic models, merits of the simplified models lie inthat they are easier to implement optimal design without losing computationalaccuracy.Based on the simplified rigid dynamic models, a novel approach for dynamicdimensional synthesis is proposed. The originality of this approach can besummarized as follows.(1) Two novel normalized global dynamic performance indices associated respect-ively with the inertial and centrifuge/Coriolis components of the driving torque foreach limb are proposed. This leads to an important conclusion that the performanceindex of inertial torque will turn to be infinite when either direct or indirectsingularities occur.(2) By a deep insight into the algebraic characteristics of direct and indirectJacobian, two types of pressure angles are defined, with which the direct and indirectsingularities can be observed in a direct manner and thereby the force transmissionability within and amongst limbs can be visibly evaluated.(3) Equipped with these dynamic performance indices as objective functions andthe pressure angles as kinematic constraints, a multi-objective optimization problem has been formulated for solving dynamic dimensional synthesis problem of Delta-likehigh-speed parallel manipulators which are actuated by proximal revolute joints andcomposed of limbs containing parallelograms.The proposed model and methodology have been successfully employed for thedevelopment of two prototype machines (Delta and Cross-IV), and the performancetests have been carried out. The experiment results show that the kinematic anddynamic performance of the two prototypes have good match with those achieved bytheoretical development and computer simulation.