A compact and reliable generator for backpack energy harvesting
Abstract
A backpack energy harvesting system can not only serve as a portable source of power but also it can reduce the metabolic cost of walking and reduce the orthopedic injuries. The existing backpack energy harvester employs a rack-and-pinion system to convert the high-force, low-speed reciprocation of the backpack into a low-torque, high-speed rotation suitable for conventional ac generators. The mechanical rack-and-pinion suffers from drawbacks such as noise, friction, need for special grease and lubrication, and packaging challenges. An alternative solution would be to use a linear generator directly coupled to the motion of the backpack. However, because weight and volume of an electric machine are proportional to its force rating, such generator would become very bulky and heavy. In this project, a novel electromechanical energy conversion system is proposed for backpack energy harvesting. The proposed energy conversion system, which we have named machine-integrated trans-rotary magnetic gear (MITROMAG), is formed by the integration of two devices: a trans-rotary magnetic gear (TROMAG) and a rotary electric machine. TROMAG is a novel type of magnetic gear that converts a high-force, low-speed linear motion to a low-torque, high-speed rotation. The motion conversion is performed through magnetic fields; thus without any mechanical contact. Elimination of mechanical contact is expected to result in a silent operation, high efficiency, low maintenance, and inherent overload protection capability (hence high reliability), which are of particular importance in military applications. TROMAG can offer a very large force density (of the order of 250-400 kN/m2) and a very large gear ratio (of the order of 600 m-1) ; thus resulting in a light-weight and compact design. While initial research on the use of the TROMAG in wave energy harvesting has been performed recently by the PI and another research group, the use of the TROMAG in backpack energy harvesting is unprecedented and poses unique challenges. In this project, we will model, design, optimize, control, fabricate and test the proposed electromechanical energy conversion system for backpack energy harvesting. Notably, the application of the MITROMAG is not limited to backpack energy harvesting and, upon tackling the challenges, this idea can be adopted to many linear motion applications. Examples of potential applications span over a wide range from forcedense linear actuators for aerospace industry to large generators for ocean wave energy harvesting. We have shown that, depending on the application, the proposed idea has the potential to make order-of-magnitude reductions in weight and volume and reduce the overall cost compared to direct drive linear machines. The overall objectives of this project are 1) Dynamic analysis and control system design for the proposed system; 2) Magnetic analysis and design of the proposed system; 3) Experimental assessment of the proposed system.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2017
- Source ID
- N000141712180
Entities
People
- Siavash Pakdelian
Organizations
- Office of Naval Research
- United States Navy
- University of Massachusetts