Toward Human-Powered Lower Limb Exoskeletons: A Review

Most of the commercially available exoskeletons use rechargeable Li-ion batteries, which require frequent charging. The battery charging becomes a big bottleneck, when the person, wearing the exoskeleton, needs to go for a week trip on trekking or mountaineering. In order to make batteries more reliable and portable, an alternative energy source can be a good option. Human-powered devices are useful as an emergency electric power source, during natural disaster, war, or civil disturbance make regular power supplies unavailable. These devices have also been treated as an economical and environment-friendly option for use in underdeveloped countries, where batteries may be expensive and main power supply is unreliable or sometimes unavailable. Some of the environmental-energy-producing sources are piezoelectric devices, vibrational sources, RF transmitters, etc., where each method produces different amount of electricity. Some of these sources do not produce enough energy to charge an exoskeleton’s battery. Therefore, in this article, an effort has been made to review the human-powered products in order to develop a mechanism that can be used for charging the battery of exoskeletons. Human power is defined as the use of human work for energy generation. The energy is harvested from the user’s daily actions (walking, breathing, body heat, blood pressure, finger motion, etc.). This paper compares the various conventional and alternative methods to charge lower limb exoskeletons to be used for elderly people.