Optimal distribution of the actuating torques for a redundantly actuated masticatory robot with two higher kinematic pairs

Abstract

Optimal distribution of the actuating torques for a masticatory robot, which is in the form of a redundantly actuated parallel mechanism with two point-contact higher kinematic pairs (HKPs), is investigated in this paper. First, the mechanism of the robot is described, in which the two HKPs are used to model the temporomandibular joints between the condyles and the maxilla in the human masticatory system, and the six kinematic chains are used to model the six groups of the muscles of mastication. Then the inverse dynamics is studied using the Lagrange’s equations of the first type, resulting in the closed-form solution for the actuating torques. Considering the infinite solutions of the inverse dynamics for the actuating torque distribution in the redundantly actuated parallel robot, six optimal criteria that signify the practical performance of the robot are proposed. Finally, two simulations without and with bite force exerting to the teeth, respectively, given that the robot is specified to track a real human mandibular movement are conducted. Results are discussed and it is found that the dynamic performance of the robot varies significantly from one optimal criterion to another.