Reliability-Based Design Optimization of Omnidirectional Energy Harvesting Sidewalk Block Considering Human Gait Analysis

Abstract

Piezoelectric energy harvesting (PEH) which scavenges electric power from ambient, otherwise wasted, mechanical energy has received significant attention as an ultimate solution to possibly eliminate batteries for powering portable electronics. As a compact and durable design paradigm of a piezoelectric energy harvester, energy harvesting skin (EH skin) which can be directly attached onto the surface of an engineered system has been proposed and thus requires no need for clamping fixtures and proof mass. The objective of this thesis is to propose an innovative energy harvesting sidewalk block concept by advancing the design methodology of EH skin. Even though few energy harvesting sidewalk blocks have been commercialized, however, there has been no scientific approach to design an energy harvesting sidewalk block considering human gait analysis. This thesis thus presents a systematic design methodology for the omnidirectional energy harvesting (OEH) sidewalk block considering human gait, which consists of four sequentially-executed tasks as: 1) the extraction of a loading profile from ground reaction force of normal gait, 2) the multiphysics modeling with finite element method (FEM) to estimate the time-variant stress and output voltage of OEH sidewalk block according to gait cycle, 3) development of conceptual design of OEH sidewalk block, and 4) reliability-based design optimization (RBDO) of OEH sidewalk block. In RBDO, the design problem is formulated as the maximization of the output energy subjected to fatigue failure constraints in a probabilistic manner. Since Kriging and polynomial surrogate models are constructed based on the Latin Hypercube sampling (LHS) for design of experiment (DOE). Monte Carlo Simulation (MCS) was used to calculate the reliability for a probabilistic constraint with affordable computational effort. To the best of the authors knowledge, this study is the pioneering work to perform RBDO of OEH sidewalk block while accounting directional uncertainty in human gait as well as variability in material properties and geometry.