Design of a Novel Compact Adaptive Ankle Exoskeleton for Walking Assistance
Series elastic actuators (SEAs) are commonly used in ankle exoskeletons for friendly human-robot interaction and high power efficiency. However, most ankle exoskeletons face a common performance limitation due to the use of fixed stiffness series springs. In this paper, we present an adaptive ankle exoskeleton for walking assistance. A novel compact variable stiffness SEA with a non-linear spring, which is able to passively change the spring stiffness as a function of output load, is developed to overcome the limitation of the conventional SEAs. The predefined nonlinear elasticity of the proposed passively variable stiffness SEA (pVS-SEA) is achieved with a cam mechanism and leaf springs, which result in a compact design. Furthermore, a variable transmission mechanism is adopted to modulate the physical exoskeleton stiffness as a function of ankle joint angle. The exoskeleton mechanism is optimized based on the human gait data by employing a genetic algorithm. The results show that the presented ankle exoskeleton is adaptable under different walking conditions, and the energy efficiency of the system is improved compared with the conventional ones.
KeywordsAnkle Exoskeleton Series Elastic Actuator (SEA) Nonlinear Spring Power Efficiency Design Optimization
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This research is supported by the National Natural Science Foundation of China (NSFC) under grant No. 91848104, and the National Key R&D Program of China under grant No. 2016YFE0105000.
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