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Subject: search.filters.subject.Mastication simulation

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    A novel wearable assistive device for jaw motion disability rehabilitation : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Auckland, New Zealand
    (Massey University, 2014) Wang, Xiaoyun
    Temporomandibular disorder (TMD) is a group of dysfunctions in the masticatory system that cause muscle stiffness and weakened masticatory ability. TMD is commonly suffered by a considerate percentage of the population, impairs oral hygiene and brings inconveniences to a great number of patients. The therapeutic exercise with significant efficacy is widely advised among patients in the treatment of the mandibular hypomobility to reduce pain and increase the inter-incisal opening of the mouth. This thesis proposes a novel wearable device to passively assist to deliver the mandibular movement. The mandible, attached to the skull via masticatory muscles and pivoted at the condyles at the temporomandibular joint (TMJ), can be simplified as moving in the two-dimensional sagittal plane. A planar four-bar linkage was synthesized to reproduce the specified normal jaw motion in terms of incisor and condyle trajectory on the coupler point to meet the kinematic specification. Adjustable lengths of the links were used to achieve a group of trajectories of any possibility. The prototype of the linkage has been fabricated, integrated with the sensory units and electronic hardware into a Mechatronic system. The dynamics of the entire system was analyzed, along with the model thoroughly built up in Simulink, to facilitate further controller design. A closed-loop control scheme based on the device was proposed, and it is able to achieve the accurate position control to the crank to ensure the position of the jaw to be notified. A series of experiments with the device has been carried to evaluate the performance of the controller, with the control algorithm implemented into a micro-controller based board. The exoskeleton was then evaluated in terms of the kinematic and dynamic interaction in the hybrid human-machine system, in which the condyle movement was recorded by AG500 tracking machine. Simulation and experimental methods were respectively developed to investigate the joint force which is in-vivo inaccessible. Simulation was conducted by adding the dynamic model of the mandible into the linkage model with controller. A test-rig was designed to mount the skull and the jaw replicas which simulated the counterparts in human body. Experiments were carried to evaluate the joint force and the performance of the controller; results obtained from both simulations and experiments have indicated the force level inside the TMJ is rather small compared with the one in the circumstance where maximum chewing force is applied.
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    Modelling and compliance control of a linkage chewing robot and its application in food evaluation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Albany, New Zealand
    (Massey University, 2012) Sun, Cheng
    Many instrumental techniques have been developed to provide quantitative data on food texture as an alternative to sensory methods for food texture characterisation. However, most instrumental measurements are not able to simulate whole chewing sequences, the jaw movements and the influence of teeth geometry involved in mastication. Several devices have been proposed to simulate human mastication but they either cannot simulate human chewing trajectory or are difficult to be controlled. A novel simple linkage chewing robot was previously developed to reproduce human chewing trajectory. The aim of this thesis is to simulate human chewing behaviour by applying compliant chewing forces and velocity on the food during mastication. In order to allow the entire mastication process to be continuously reproduced, the chewing robot was upgraded with a 3D force sensor, an automatic food manipulation system with 3D carved teeth and a spring mass system to apply passive force control. Aiming at the compliant chewing, the dynamic model of the chewing robotic system was developed, including the linkage mechanism, gear transmission, DC motor and food models. The simulation model of the chewing robot was validated by comparing the simulated torques and the experimental torques of the crank required to drive the robot. A control algorithm to achieve the compliant chewing for the robot is formulated in terms of adaptive fuzzy logic control, and is able to achieve fast coordination of chewing velocity and forces required for different type of foods, and validated in simulations in terms of chewing velocity and forces. The chewing experiments with the robot chewing on real foods were carried out and analyzed in terms of the adaptation of chewing velocity and force to the food texture changes during chewing process. Both simulation and experimental results show that the proposed algorithm is adaptive and able to simulate human chewing behaviour on foods with different texture, which indicates the usefulness of the developed robot in food texture evaluation. The chewing robot developed has been used routinely in our laboratory and exhibited a great potential as a tool for the evaluation of food properties and bolus preparation.