Workspace Analysis and Experimental Verification of a RedundantlyActuated Jaw Movement Robot

The mandible is constrained by temporomandibular joint (TMJ) and actuated by more numbers of muscles than its own degrees of freedom (DOF), so the human mastication system is redundantly actuated. Based on this characteristics, a redundantly actuated parallel mechanism with point contact higher kinematic pair (6PUS-2HKP) for simulating mastication movement is introduced, which can be used for dental materials testing. Firstly, the coordinate system of the robot is established. Considering the characteristics of existing point contact higher kinematic pairs, the position parameters and the kinematics equation of the redundant parallel mechanism are analyzed and derived. The border movement of the test subjects' mandibular incisor point is obtained by using the mandibular kinesiograph in the experiment. The workspace of the redundantly actuated robot is analyzed with numerical method through calculating the movement ranges of the driving rods and the point contact higher kinematic pairs. The trajectory of the lower incisor point of the robot is measured through experiment when the robot moves along the edge of the largest workspace. Comparing with test subjects' border movement and the simulated workspace result, it is shown that the jaw movement robot can meet the movement space requirements of the mandible.