Theory And Application Of Geometric-Constraint Synthesis Method For Parallel Robots

Although theoretical research on parallel robots has matured,the application of parallel robots in the industry is limited.The author suggests two main reasons for the gap between theory and practical applications: the advanced mathematical foundation of the existing design theory of parallel robots,which has limited their application and promotion in the engineering field,and the small workspaces of parallel robots,which inhibits their range of industrial applications.To establish a simple and easy-to-use type synthesis method and explore various configurations of parallel robots with large workspaces,this study conducts theoretical and practical investigations related to the design of parallel robots.The main research content is summarized below.Starting with an expression for serial chains,the study first defines the incidence matrix,constraint matrix,and constraint incidence matrix(CIM)of the serial chain.The CIM reveals the motion and constraint information of the serial chains and the inter-relationship between motion and constraints.This work lays the foundation for the type synthesis of parallel robots.Based on the geometrical characteristics of screw theory,this study proposes a geometric-constraint synthesis method that converts the type synthesis of serial chins to a geometric derivation of CIMs.To reduce the complexity of parallel robots’ design,a serial chain database is established,in which the designer can directly find the target serial chains to construct the desired parallel robots.Moreover,the constraint matrix is used to represent the mechanism-constraint system of a parallel robot and judge the full-cycle mobility of the parallel robot.Furthermore,the geometric-constraint synthesis method was employed for the type synthesis of metamorphic parallel robots and gave the general synthesis steps of metamorphic parallel robots.Ten new types of 6-degree-of-freedom(DOF)metamorphic parallel robots are synthesized,and their motion-mode switching conditions are analyzed.Twin parallel robots are then synthesized using the geometric-constraint synthesis method,and the design principle of twin parallel robots is presented.The structural characteristics of target serial chains are analyzed,and several new configurations of 2R and 2R1 T twin parallel robots with large workspaces are synthesized.The study introduces wheels to the parallel robot field,realizing a wheeled parallel robot that combines the advantages of mobile and parallel robots.Besides having high moving efficiency and a wide range,this robot performs high-precision operations over a small local range.Based on the algebraic characteristics of screw theory,the study proposes an automatic type synthesis method for parallel robots and applies it to the type synthesis of wheeled parallel robots.Aided by a computer,this method converts the type synthesis of serial chains with wheels to the generation and selection of incidence matrices,thus realizing automatic type synthesis of serial chains.Finally,four types of 6-DOF wheeled parallel robots are synthesized,and two prototypes of 6-DOF wheeled parallel robots are developed.