Robotic Chewing Experiments

Abstract

The Crank Actuation masticatory robot of 6RSS parallel mechanism is applied to the chewing of foods. The forces on food samples during experiments were calculated from the recorded torques measured for each of the six actuators. A series of experiments were carried out on model and real food systems, and the resulting forces were discussed with respect to food texture. To begin with, the robot was compared with traditional uni-axial compression testing by implementing a one dimensional vertical crushing motion on the robot with flat plates used in place of the teeth. Very good agreement was found between the robot and texture analyser force-deformation profiles. The robot was also tested against the measured force profiles recorded for a 2D trajectory used to simulate movement of the 2DOF 6-bar linkage robot. Again good agreement was found, particularly in the vertical dimension. Finally, the robot was used to simulate the trajectory of real time 3D recorded human mandible movements during mastication. Vertical force measurements were consistent with the expected failure mechanism for each food. In each experiment unexpected forces in the non-vertical dimensions were found. These forces could be due to internal friction in robot linkages under loaded conditions. After identification and resolution of the cause of the unexpected x- and y-axis forces, the chewing robot will be suitable for use in analysing the initial textural properties of foods. Research into appropriate force control strategies, food bolus retention and re-orientation of the food on the teeth between cycles is required before the machine can be realistically used to mimic whole chewing sequences and provide insight into the food texture dynamics during bolus formation.

This chapter is based on work conducted by Jonathan Torrance, PhD student at the School of Engineering and Advanced Technology, Massey University, New Zealand.