Developing a hardware in-the-loop simulator for a backpack energy harvester

Energy harvesting from ambient sources has been the subject of several studies. Some of the proposed approaches attempt to generate electrical energy from the human movement. However, many of them can be uncomfortable or they impose a significant burden on the person's gait. In the current article, the design of a hardware in-the-loop simulator for an energy-harvesting backpack is presented. The idea is based on the energy produced by a suspended load that moves vertically on a backpack while a person walks. The energy created from such a linear system can be maximised when it resonates with the walking frequency of the person. However, such a configuration can also cause great forces to be applied on the back of the user. The system that is proposed here consists of a mass attached on a rucksack, which is controlled by a motor in order to simulate the suspended-load backpack. The advantage of this setup is the ability to test different settings, regarding the spring stiffness or the damping coefficient, of the backpack harvester, and study their effect on the energy-harvesting potential, as well as on the human gait. The present contribution describes the design, analysis and preliminary testing of the hardware in-the-loop backpack system.