A montecarlo approach to test the modes of vibration of a 6-DoF parallel kinematic simulator

Parallel kinematic manipulator are for sure the best choice to fulfill the need of high accuracy and high stiffness. By the way due to the always increasing required performances, poor decisions during the early design stages might lead to the arising of vibration phenomena during the operating phase of the machine. Due to the intrinsic nonlinearities that characterize this kind of machines the modes of vibration of the structure strongly depend on the pose of the robot. In addition in many applications as the one presented in this paper the tasks the machine is required to perform are not known in advance. Usually the technical specification for a PKM in terms of workspace dimensions and maximum excitation frequencies are related to the end-effector. By the way the kinematics that links the motion of the mobile platform to the joints motion is highly nonlinear, and thus might produce the insurgence of higher frequencies excitations. This paper presents an approach to test the modes of vibration of a 6-DoF parallel kinematic simulator that relies on a statistical method to investigate different possible motions of the end-effector that involve a combination of translations and rotations on the basis of their probability density functions (PDF)