Parallel Architecture Manipulators for Use in Masticatory Studies

Introduction

The goal of this research is to develop an experimental testbed for analyzing the masticatory jaw motions of animals (including humans) and establish the quantitative relationship between relevant geometric parameters (tooth geometries, numbers and types) as well as regimen parameters (joint forces, motions) during the mastication process for further detailed studies. Such an understanding would be of tremendous importance from different perspectives. From a biological science perspective, it is critical to understand the physiological variability in mastication across individuals in a species as well as across the entire population. It is also very useful to know how various animals preprocess food while chewing and biting so that the research scientists can hypothesize behavioral analyses of how certain breeds of animals kill their prey with an accurate estimate of biting forces (Signore, Krovi, & Mendel, 2005) and understand the resulting muscles functioning to draw interesting conclusions. From an engineering perspective, such a study on masticatory performance would enable to quantitatively assess the “chewability or performance index” due to variations in food properties as well as facilitate the parametric design of dentitions/prosthetic additions.

To this end our work focused on developing quantitative engineering tools to enable this process (Figure 1). Specifically, we focused on (i) designing a general purpose mastication simulator test-bed based on parallel architecture manipulator, capable of producing the motions and forces encountered; and (ii) validating this simulator with a range of test-foods undergoing varying mastication cycles under controlled and carefully monitored circumstances. Such an implementation could provide a testbed to quantitatively characterize the mastication based on “chewability index” factor for a wide range of applications. Building a generic engineering test-bed that can be used to study mastication for these diverse goals offers significant challenges. The multiple facets of the overall project are shown in Figure 1 – in this paper, we will focus only on the highlighted sections. Specifically, various design variants of parallel manipulators were examined for jaw simulators before finalizing on 6-P-U-S keeping in mind the high force requirements as well as desirable workspace required for various masticatory motions. A detailed workspace analysis based on the Jacobian measures is considered to be significant to ensure desired characteristics for the manipulator that is presented in mathematical background section. We then drive the kinematic model with the jaw motion trajectories obtained from the motion capture (MoCap) analysis system. Finally, the optimal configuration and workspace analysis results of 6-P-U-S parallel manipulators will be presented in results section. This paper also discusses the validation performed on the physical platforms using the recorded MoCap data.

Figure 1.

Project flowchart