Date of Award:

9-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Advisor/Chair:

Byard Wood

Abstract

In 2011, a team of senior engineering students at Utah State University, in connection with the university’s Center for Persons with Disabilities, designed and prototyped an assistive technician creeper. Building on successful features and resolving issues discovered in design validation testing of the initial prototype, this thesis includes the refined development of a fully assistive technician creeper with emphasis on improvement of kinematic functionality, overall manufacturability, and integration of system safety features. The final design solution is a creeper that transforms a user bi-directionally between the seated position, and a maneuverable supine position, while requiring only simple manual actuation.

New design requirements were established including specifications for user height, weight, and body mass distribution, driven by census and medical data suitable for 95% of individuals. Using 3D modeling software, an iterative design approach was used in conjunction with kinematic, and structural analyses, to generate an improved feature set that can be easily manufactured and assembled. Of particular interest is the modification to the kinematic system, which produces multiple single-degree-of-freedom kinematic motions from a single multi-degree-of-freedom kinematic mechanism. This promotes the use of a single motor to produce separate motions for adjusting upper body inclination, and raising the seat surface. The revised design adheres to principles of design for manufacturability and assembly, by using common economical manufacturing processes, minimizing part asymmetry and maximizing part reuse.

Employment of engineering analyses, including kinematic, finite element, and failure modes and effects analyses quantified design validation and risk mitigation. Static force analysis and computations of fatigue and life expectancy of critical components supplement the analysis set. Analysis suggests all structural components were designed to meet a safety factor of 3.0 or better. This combined with the addition of safety features and system protection redundancies provide confidence in structural integrity and system reliability. This creeper will contribute to the world of assistive technologies by providing new mobility opportunities, improving the quality of life of individuals with certain physical disabilities. It is also well suited for users of all abilities and has potential to become a premium creeper for professionals.

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