Mastication Robot of a Crank-Slider Linkage

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This chapter outlines the development of a linkage-based masticatory device for use in food evaluation that is capable of performing a range of standardised chewing trajectories. The robot design was required to match the trajectory of the first molar and the forces applied on the foods as measured during human chewing experiments performed in-vivo. A four-bar linkage was synthesized to achieve a lateral chewing trajectory of the molar. By adjustment of the ground link length, any trajectory between lateral (grinding) and vertical (crushing) chewing motions was possible. A six-bar crank-slider linkage was then designed in order to guide the movement of the mandible in a set orientation whilst maintaining the chewing trajectory produced by the four-bar linkage. The chewing device based on the six-bar linkage was constructed inclusive of: anatomically correct teeth for reducing the food particle size, a food retention device for collection of the food particles being chewed and a shock absorber for preventing the application of excessive chewing forces. The linkage chewing device was evaluated by way of kinematics and dynamics simulations together with a comparative analysis of the actual measurements of the trajectory and chewing force. The chewing velocity along the trajectory was profiled for both the occlusal and opening/closing phases of the chewing process and used for the set points for motion control. Variations to account for differences in chewing cycle velocity profiles were made to be adjustable through a graphical user interface developed in LabView. The masticatory device was validated against experimentation involving the chewing of example food systems and comparison of the resultant particle size within the bolus produced by the device and those produced by human subjects for the same food stuffs.