Kinematics Error Analysis And Simulation Of 3-CUR Parallel Mechanism

Parallel mechanism has lots of advantages compared to serial mechanism, however parallel mechanism has not been wildly used. One of the important limiting factors is the precision problem. Parallel mechanism’s manufacturing and assembly errors have serious nonlinear effects on the output of the moving plat due to its complex structure. This papper aims to implement the kinematics error analysis of 3-CUR complete decoupled parallel mechanism in order to guide the design of parallel mechanism from the perspective of error, and search for an effienct calibration method to reduce the influence of manufacturing and assembly errors and improve its motion precision. Main contents of this paper are as follows:A systematic introduction to parallel mechanism error classification is given. Based on the comprehensive analysis of exiting two parallel mechanism error modeling method, considering the configuration characteristics of 3-CUR parallel mechanism, a method of establishing the whole error model to this mechanism is proposed. Establish the kinematics error model of 3-CUR complete decoupled parallel mechanism. On this basis, the mapping matrix of manufacturing and assembly errors relative to the moving plat’s output errors is acquired after using differential transformation to the error model under tiny errors.Using the screw theory, analyse the 3-CUR parallel mechanism’s branch composition of kinematic screw systerm. Considering its kinematics decoupled property, a new theoretical anlysis is proposed aiming at the controllable DOF(degree of freedom) error and the uncontrollable DOF error of decoupled parallel mechanism with few DOF. Using the virtual prototype technology of Pro/E, verify the applicability of the new theoretical analysis to the 3-CUR parallel mechanisms.The three-dimensional model with four kinds of error sources is established via Pro/E. And then the influence law of four kinds error sources relative to the moving plat’s output is acquired through the precision analysis in the given work space.Adopting the error calibration method based on the spatial distance formula and the error compensation method based on correcting the drive input, combined with genetic algorithm, conduct the error simulation to 3-CUR parallel mechanism. By simulating a set of examples in Matlab, compensate the error based on the obtained error identification results and compare the result before and after error compensation.