Harvesting the negative work of an active exoskeleton robot to extend its operating duration

Abstract

Active exoskeleton robots can assist with the rehabilitation of those with disabilities, heavy manual work, and long-distance travel of soldiers. However, the operating duration of exoskeleton robots is limited to the battery volume. In this work, we propose a working mode to harvest the negative work of the exoskeleton robot itself to extend its operating duration. We also report an energy harvesting module to demonstrate the working mode. The module is mainly comprised of one shifting slide gear, one input gear, one output gear, one spiral spring, one generator and two mounting plates. The mass of the module is only 320 g. The module can be easily mounted on most commercially available active exoskeleton robots. Practical experiments show that the module can reduce battery chemical energy dissipation by 1.59 J per walking cycle. The maximum harvested voltage is up to 62.59 V and the maximum harvested power is 5.6 W. The power density of the negative harvesting module is up to 17.5 W/Kg. Under the negative work harvesting mode, the operating duration of the active exoskeleton robot can be extended by 20.95%, which provides the benefit of longer operating duration. The module has a long service life and a high reliability, and it does not affect the normal movement of human being. The advantages of high power density, high voltage, excellent compatibility, and light weight make the energy harvesting module a promising sustainable power source for the active exoskeleton robot.