Rapid Onset Impulsive Loading: Three Dynamical Case Studies
In this dissertation I present research undertaken on three dynamical systems, which I
term ‘case-studies’. The most interesting dynamics in these systems were largely precipitated
by abbreviated periods where impulsive loading dominated.
The first case-study features an impulsively-loaded wave energy converter (WEC) for
which mass modulation schemes have been proposed which take advantage of the ambient
water motion. Experimental results for a pair of passively and impulsively initiated
schemes are presented and one of them is shown to be effective in increasing the energy
harvesting potential of a WEC; numerical analysis of the model also shows the potential
benefits of the mass-modulation scheme and, moreover, validates the benefits of harnessing
impulsively applied fluid pressures which are often neglected in the design of a WEC.
The second case-study examines the accidental untying of a shoelace while walking. In
this case-study, I discuss the series of events that lead to a shoelace knot becoming untied.
Slow-motion video footage and a series of experiments show the failure of the knot happens
in a matter of seconds, often without warning, and is catastrophic. Controlled experiments
show that increasing inertial effects of the swinging laces leads to increased rate of knot
untying, that the directions of the impact and swing influence the rate of failure, and that the
knot structure has a profound influence on a knot’s tendency to untie under cyclic impact
The final case-study concerns the ground-up development of prototyping techniques for
a soft-robot modeled after the common caterpillar. I sought to suggest an analysis path for
rapid prototyping of a SMA based, caterpillar inspired soft-robot to undergo undulatory
motion. Analysis of the kinematics and dynamics of the caterpillar are structured through
simple models which yield estimates of forces and energetics that would be extremely
difficult to determine directly, in addition to suggestions for open-loop motion patterns.
Simultaneously, simple experiments and optical tracking of SMA segments were performed
to yield properties input directly into a robust numerical solver used to simulate a prototype
soft-robot’s undulatory motion and reveal facets leading to the success or failure of its