טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAharoni Lital
SubjectDesign and Analysis of the Dynamics of a Propelling
Mechanism: A Self-Locking Elastic Traveling Wave
Motor With a High Transmission Ratio
Ratio
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Izhak Bucher
Dr. Nadav Cohen
Full Thesis textFull thesis text - English Version


Abstract

The study discusses a small propulsion system capable of injecting a viscous fluid through a needle attached to a standard syringe. The design requirements raise considerable engineering difficulties that lead towards a dynamic mechanism that can, on the one hand, provide large static forces, such as are required during injection of viscous fluid and, on the other hand, to produce precise, controlled displacements without causing failure of the enclosing glass shell. Finally, the system is developed to be mass-production ready and is realized by additive manufacturing methods. To develop such a propulsion mechanism, several configurations were tested, one based on a vibrating piezoelectric motor that intermittently contacts the glass casing. Such a mechanism experiences a non-linear oscillation regime and the need to design an operation configuration that drives the syringe plunger requires the construction of a physical model and numerical simulation-based design. An alternative configuration considered and finally chosen in this work, offers an elastic structure that produces casing waves at the interface between the plunger and the syringe so that the design constraints, namely static holding power and progress in the glass tube are controlled. Progress is created by envelope traveling waves that produce relative motion on the glass. Its physical phenomenon and mathematical modeling require complex modeling and analysis tools that describe the contact between the elastic casing waves and the glass container. This configuration was chosen as a solution that addresses the need and an experiment is built that demonstrates the phenomenon. In this work, a novel propulsion mechanism with two main parts is presented. A helical wave generator and a deformable, toothed sleeve. Once the helical part rotates, it induces deformation waves in the toothed part, which is pressed against a rigid tube. It is demonstrated that this mechanism can exhibit a significant static force, when stationary and a large axial force under continuous operation. Opposed to ultrasonic wave-motors, the present mechanism operates in a quasi-static manner by alternating between nonlinear elastic equilibria. By controlling the geometrical parameters, the level of preload due to sizes overlap, the ratio of holding force and transmission ratio can be controlled. The rigid helix and the deformable sleeve are made by standard 3D printing process, exploiting plastic and rubber-like materials. The work describes the kinematics and layout of the mechanism, analyzes its behavior in simulation and experiments and highlights design alternatives