A method for determination of equivalent nonlinear
stiffness and load of branchs on parallel machine tool is presented. In
this method, numerical analysis model of parallel machine tool with joint contact deformation is first established and then, deformation data of the parallel machine tool ending
obtained via the experiments are ushered in the analysis model so that a set of nonlinear equations concerning the equavalent
stiffness of branch chain of parallel machine tool can be obtained. Also, the linearization method of the nonlinear stiffness matrix is used to obtain the solution. After the branch chain stiffness and load of parallel machine tool are obtained, the branch chain can be considered as the serial machanism, whereby the stiffness and load on each joint of branch chain can be further obtained in such a way as to lay a solid foundation for the static and dynamic characteristic analysis of the whole parallel machine tool. With a set of parallel machine tool as an example, the joint load is calculated. As compared with the literature result, this method is reliable and effective.