07/11/2022
By Sokny Long

The Francis College of Engineering, Department of Electrical and Computer Engineering, invites you to attend a dissertation defense by Amin Abolhasani on “Magnetically Geared Generator for Backpack Energy Harvesting.”

Doctoral Candidate: Amin Abolhasani
Date: Monday, July 25, 2022
Time: 10 a.m. to noon
Location: This will be a virtual defense via Zoom
Dissertation Title: Magnetically geared generator for backpack energy harvesting

Committee Chair (Adviser): Siavash Pakdelian, Assistant Professor, Department of Electrical and Computer Engineering, University of Massachusetts Lowell

Committee Members:

  • Tingshu Hu, Professor, Department of Electrical and Computer Engineering, University of Massachusetts Lowell
  • Mufeed MahD, Associate Professor, Department of Electrical and Computer Engineering, University of Massachusetts Lowell

Brief Abstract:

A backpack energy harvesting system (BEHS) can harness power from reciprocation of the backpack while reducing the metabolic cost of walking as well as the risk of orthopedic injuries. The idea behind the BEHS is to create a phase shift between the body’s reciprocation and the backpack’s reciprocation through a decoupling spring. To prevent uncontrolled oscillations and generate power, a damping system is needed.

The existing BEHS system employs mechanical rack and pinion (MRP) to convert the backpack’s low speed reciprocating motion to high speed rotation so as to spin a conventional generator. However, it suffers from friction, noise, wear, and a need for maintenance and lubrication. An alternative is to use a direct drive linear generator which can mitigate all the shortcomings of MRP. Nevertheless, the direct drive system requires a bulky and heavy generator on account of the high-force, low-speed motion characteristic of the backpack.

In this work, a contactless and inherently low friction magnetic gear is developed to overcome these concerns, leading to significant weight savings. The proposed BEHS is much lighter and more compact than a direct drive linear generator. Moreover, it has lower friction and noise and benefits from less maintenance requirements compared to the MRP system. For the purpose of harvesting maximum energy from the BEHS, two control strategies are studied. To better understand the essence and implications of the control strategies, a dynamic equivalent circuit of the electromechanical system is developed and employed. The equivalent circuit utilizes a per-unit system as a means to facilitate the analysis and provides a unique insight into the system behavior and control. Simulation results prove the superiority of the proposed system in terms of overall performance. Moreover, a test bed is developed to experimentally verify the performance of the proposed system. The backpack’s motion is emulated via a rotary motor coupled to mechanical rack and pinion. Experimental results corroborate theoretical findings.