Integrated Design And Vibration Control Of A SCARA Type High-speed Parallel Robot

Driven by many practical needs from food,pharmaceutical,packaging and many other light industries for high-speed pick-and-place parallel robots,this dissertation investigates into the methodologies for enhancing the capability and efficiency of a novel 4-DOF SCARA pick-and-place parallel robot composed of parallelogram limbs plus an articulated travelling plate.The main contents are closedly related to conceptual design,kinematic and dynamic modeling,integrated design,trajectory planning and input shaping for residual vibration suppression.The following contributions have been made.The underlying principle to form 4-DOF SCARA type parallel robot composed of parallelogram limbs and articulated travelling plates are revealed using displacement manifold method.A compact,light-weight yet rigid articulated travelling plate is then designed using rack-and-pinion assemblies and linear guide rail pairs,allowing the mechanical realization of a novel C4 parallel robot having high transmission accuracy and long service life.In order to ensure comprehensive performance of the high-speed pick-and-place parallel robots,a set of comprehensive performance indices are proposed in terms of not only kinematics but also rigid body as well elastic dynamics.This leads to the establishment of an integrated framework that enables the optimal design to be hierarchically and iteratively implemented in three steps,i.e.dynamic dimensional synthesis,dynamic stress verification,and motor sizing.The proposed approach has successfully been employed to the development of a C4 parallel robot prototype with capacities for achieving a maximum speed up to 10 m/s and a maximum acceleration up to 150 m/s~2.A new,highly effective approach for optimal smooth trajectory planning of high-speed pick-and-place parallel robots is proposed using the fifth-order B-splines.By using symmetrical properties of the geometric path defined in the Cartesian space,this method features an initial offline determination of two key factors dominating the normalized motion profiles along a path,followed by the online generation of the smooth joint trajectories using a look-up table.The simulation and experimental results show that the time profiles of the joint torques are relatively small and very continuous and smooth,with residual vibration of the end-effector substantially reduced.Having revealed the dominant flexible mode that varies with payloads and system configurations,a robust input shaping method is presented by minimizing the maximum percentage vibration of the end-effector throughout the entire workspace.Numerical simulations of a statistical experiment are then conducted to verify the effectiveness of the proposed method in random pick-and-place operations.The experimental results show that up to 80%residual vibrations can be dramatically reduced by using the proposed input shaper over the unshaped commands,resulting in significant improvement of the dynamic positioning accuracy of the end-effector.The outcomes of this dissertation have been successfully applied to the design and development of a 4-DOF high-speed pick-and-place parallel robot for achieving superior performance.