Accuracy Analysis And Synthesis Of TriMule Hybrid Robot

To build the prototype of the 5-DOF(degrees of freedom)hybrid robot named Tri Mule,this thesis investigates the accuracy analysis and synthesis of the 3-DOF parallel mechanism within the robot.The research includes error modeling,tolerance modeling,accuracy analysis and synthesis,aiming to reveal the relationship between the tolerances of parts and the pose error of the platform,and carry out the accuracy synthesis at tolerance level.The outputs of this investigation provides a guideline for manufacturing and assembly of the robot.The following contributions have been made.1.Since the pose accuracy of the hybrid robot is mainly affected by that of the 3-DOF parallel mechanism,the error modeling of the parallel mechanism is established,drawing on the vector chain method and perturbation principle.The generalized Jacobian matrix is derived by introducing constraint equations.Thereby,the uncompensatable and compensatable geometric source errors are effectively identified by the Jacobian of constraints and actuations.2.The tolerance modeling is established by the method of SDT(small displacement torsor),in which tolerances are expressed in the form of 6-DOF(i.e.three translations and three rotations).Then,the mapping between the tolerances and the uncompensatable geometric error sources is derived.Sequentially,combined with the developed error model,the relationship between the tolerances of components and the pose error of the mechanism is achieved.3.The sensitivity coefficients are defined by considering probability of the error model,which reveal the influence of the uncompensatable geometric error sources on the pose accuracy of the platform in the task workspace.For the simplification of the accuracy synthesis,the Monte Carlo method is employed to analyze the distribution of the volume error.Consequently,the area in the task workspace of having the maximal volume error is found.4.With the aid of genetic algorithm,the accuracy synthesis of the parallel mechanism is solved by minimizing the manufacturing cost and taking the accuracy requirements as constraints.