Elastodynamic performance of a spatial redundantly actuated parallel mechanism constrained by two point-contact higher kinematic pairs via a model reduction technique

A spatial redundantly actuated parallel mechanism constrained by two point-contact higher ki-nematic pairs (HKPs) has been designed to evaluate food texture changes during the mastication process. To evaluate its elastodynamic performance, a model reduction algorithm that mainly incorporates the idea of the matrix structural analysis is employed. Two models are established by treating the end effector as completely and partially rigid, respectively, to explore how the HKPs influence its performance. In the first model, the overall stiffness and mass matrices contain deformation nodal coordinates, and the generalised coordinate vector in the second model is longer than that in the first model. The roles of HKPs, actuator and stiffness, and static condensation on the performance are thoroughly studied and compared. The results confirm that the mechanism has a high natural frequency and large stiffness. Increasing the diameter of the HKP-related links can effectively improve the performance. HKPs that bring constraints directly and then cause redundant actuations considerably improve the performance. Actuator stiffness is significantly important in determining the performance. The comparison between the reduced and full models shows that the former can enhance the computational efficiency, and the lower orders of the natural frequencies are accurate.