Force Reduction in a Short-Stroke Vibration Tubular Generator for Vehicle Energy Harvesting Application

This paper examines methods to reduce the detent force and electromagnetic force in a short-stroke vibration tubular generator used to harvest energy from a vehicle suspension system but still achieve the design targets of power and power density. A well-known skewing permanent magnet approach and a novel approach named the unbalanced model (or moving teeth arrangement) were considered. A multi-objective optimization-based response surface method was also investigated. The results from 2D and 3D finite element analyses (FEA) revealed that when the permanent magnet array in the proposed machine was skewed by 45°, the detent force decreased by 13.1%. When parts of the slot were shifted by the same angle (45°), the unbalanced model could even reduce detent force by 32.7%. However, output power and power density also decreased accordingly. Among these approaches, multi-objective optimization, which can find the trade-off between various physical responses, seemed to be the best solution. A prototype based on an optimal design was fabricated, tested and its behavior was in excellent agreement with the FEA.