Conceptual Design of Energy Efficient Lower Extremity Exoskeleton for Human Motion Enhancement and Medical Assistance

The paper describes conceptual design and control strategies for a new fully autonomous lower limb exoskeleton system. The main advantage of the system is its ability to decouple the weight/mass carrying function of the system from its forward motion function to reduce power consumption, weight and size of the propulsion motors. An efficient human machine interface has been achieved by means two sets of sensors: one (flexible sensors) to monitor subject leg’s shank and ankle movements and the second to monitor subject’s foot pressure. The weight is supported by a couple of passive pneumatic cylinders with electronically controlled ports. Joint motors of the exoskeleton then are only left to timely drive links of the exoskeleton when the legs take step. Therefore, motors consume less electrical energy and are small in size. In contrast to other existing exoskeleton designs, the motor batteries are able to sustain the energy supply for a longer travel distance before discharging.