KINEMATICS MODELLING AND OPTIMIZATION DESIGN OF A 5-DOF HYBRID MANIPULATOR

As most hybrid serial-parallel manipulator (HSPM) structures are complicated, it is difficult to establish dual forward and inverse kinematic models. In this paper, to simplify the structural model for HSPMs, an equivalent model method according to the motion properties of parallel mechanism is used and a serial equivalent model of the 2RPU/UPR + R + P, a five-degrees-of-freedom (DOF) HSPM, is established using this method, which also contributes to establish the kinematic model by means of the Denavit-Hertenberg notation. Especially, to solve the kinematics of lower-mobility (less than six DOFs) serial robots, a new way is put forward, and the velocity Jacobian square matrix is obtained easily on the basis of the proposed kinematics solving method; this also makes a significant contribution to acceleration analysis. Based on the global performance indices of velocity and acceleration, the physical dimension of a single-DOF tilting head on the mobile platform is optimized with an emphasis on improving the manipulator's dynamic performance. The numerical simulation considering the kinematic models is performed, and the results verify the validity of inverse and forward kinematic models. Systematic and comprehensive analysis of a five-DOF HSPM shows that the kinematics of this manipulator with a high degree of modularity is quite simple, which makes parameter calibration convenient and is essential for trajectory planning, computer simulation and real-time control.