Mechanism, design and motion control of a linkage chewing device for food evaluation

A linkage-based chewing device is proposed to perform standardised chewing for use in food evaluation. The linkage for chewing is firstly specified in terms of the trajectory of the first molar and the chewing force, according to the in vivo measurements of the human chewing ranging from grinding (or lateral chewing) to crunching (or vertical chewing). A four-bar linkage is synthesized to achieve the lateral chewing trajectory of the molar, and by adjusting the ground link length to achieve any trajectory between the lateral and vertical chewing. A six-bar crank-slider linkage is then designed to guide the molar teeth moving in a set orientation while still following the chewing trajectory produced by the four-bar linkage. The chewing device based on the six-bar linkage is constructed with inclusion of anatomically correct teeth for reducing the food particle size, a food retention device for collecting the food particles being chewed and a shock absorber for preventing excessive chewing force. The linkage chewing device is evaluated by simulations of kinematics and dynamics and actual measurements of the trajectory and chewing force. For the motion control of the actuator, the chewing velocity along the trajectory is also profiled for occlusal phase and opening/closing phase of the chewing, and the variations of the chewing for different foods are set in a GUI (graphical user interface) in Labview. The device is finally validated by chewing on a cereal bar and comparing the resulting particle size of the bolus with those by human subjects.