Smart Passive Exoskeleton for Everyday Use with Lower Limb Paralysis: Design and First Results of Knee Joint Kinetics

Abstract

Exoskeletal systems become more important for the rehabilitation of people with lower limb paralysis. Today these systems are mainly used in clinical settings, but also devices to support activities of daily living are becoming reality. The uncontrolled environment of home use leads to new design challenges and loading situations that are not yet well known. In this paper a novel orthotic system that supports people with lower limb paralysis in their everyday life is introduced. To learn more about the mechanical stress on the device, the knee joint unit was equipped with various sensors to measure motion, forces and power in real-world situations. The influence of the user's residual function on these parameters was investigated. First results from a clinical trial with 3 paralyzed patients show that knee power is in the same range as for healthy humans, with peak values up to 5.9 W/kg. Peak torque on the knee joint can be as high as 1.8 Nm/kg. There are large differences between patients depending on their diagnosis. All systems were exposed to impacts with accelerations higher than 85 m/s2at exceptional events. These results show that patient pathology significantly influences system loads, and that mechanical robustness is important for the design of supportive systems.