Abstract: Based on influence coefficient method and principle of virtual work, continuous stiffness nonlinear mapping general model of spatial parallel mechanism is established, including the elastic deformation of active and passive hinge and gravities factor. Different from the traditional model, the stiffness nonlinear general mapping model of spatial parallel mechanism is reverted, not only considering the influence of elastic deformation of active and passive hinge and gravities factor on the mechanism stiffness, but also considering the stiffness continuous change. The change of the Jacobian matrix is not neglected under the outside force, introducing the second-order influence coefficient matrix of mechanism. Then, simple restricted equations of parallel mechanism are described, and several continuous stiffness mapping matrixes are deduced respectively. On this foundation, combining Rayleigh quotient of the continuous stiffness matrix, the performance index k used to estimate the mechanism stiffness is defined, a stiffness analysis example of spatial parallel mechanism is presented. The stiffness matrixes in two models are calculated, and the stiffness performances are contrasted, respectively.

Key words: Continuous stiffness, Influence coefficient, Nonlinear mapping, Principle of virtual work, Spatial parallel mechanism