Error Modeling And Tolerance Design Of A3 Parallel Machining Tool

This dissertation deals with the precision analysis of a parallel machining tool named A3, which is independently developed in Tianjin University, Including kinematics, error modeling, tolerance design and error parameter identification. The following achievements have been obtained.The kinematic model is established based on the closed-loop vector method. The workspace is searched by considering the engineering constrains, then the kinematic performance analysis is carried out using the condition number of the Jacobian.The error model of the machine is formulated with the aid of perturbation theory, which can be used to separate the compensatable and uncompensatable error sources. The sensitivity probabilistic model is used to analyse the influence of the error sources on the accuracy of the machine, followed by the tolerance design of the errors based on genetic algorithm.The parameter identification model of the compensatable error sources is derived based on the detection of all the position and orientation errors. The testing trajectory is optimized by using the index of isotropy. The effectiveness of the proposed model is verified by simulation, then the error parameter identification is implemented based on least square method.The aforementioned achievements provide basic guidelines for the error compensation.