Development Of Lower Limb Exoskeleton Based On Series Elastic Actuator

Lower limb exoskeleton has a wide range of application prospects,such as human strength enhancement,rehabilitation,elderly and the disabled assist,etc.,and has become a research hotspot all over the world.Although many types of lower limb exoskeleton have been developed by various research institutions in China,the research on lower limb exoskeleton with compliant joints is relatively few.Series elastic actuator has been widely used in robot joints design because of its compliance,low impedance,safety and force controllable.In this paper,a lower limb exoskeleton with split series elastic actuators is designed,A prototype exoskeleton was developed and tested.In order to adapt the exoskeleton to the human body structure and motion,the degree of freedom of human lower limb were analyzed as well as the range of them,the proportion of each segment of the human lower limb to the total height was analyzed.Dynamic analysis of the exoskeleton was carried out to determine the velocity and torque of the exoskeleton joints,which provides a theoretical basis for the exoskeleton design.As a wearable device,compact flat joints are more suitable for wearing.Split series elastic actuator is divided into two parts: motor module and reducer module,the modules are of flat structure.The two modules are arranged in parallel and driven by synchronous belt,make the shape of series elastic actuator more suitable for wearing.Elastic element is the core component of series elastic actuators,in order to obtain a elastic element with compact structure and high bearing capacity,a multi-branch planar vortex torsional spring was proposed,the stiffness of the torsional spring is partialy nonlinear(with linear stiffness and nonlinear stiffness interval),the mechanical design,deformation,bearing capacity,stiffness curve ware analyzed and tested.An assistive lower limb exoskeleton was developed with the above series elastic actuator.Based on the bionic analysis,the exoskeleton active/passive degree of freedom is configured,the adjustable rods and the adjustment range was designed.The selection of key parts of exoskeleton was introduced.In order to realize the lightweight design,the weight reduction design was carried out from the aspects of finite element analysis and material weight reduction.The experimental tests show that,the exoskeleton has a performance of loading 30 kg,walking at 4.5 km / h,and the exoskeleton weights 25 kg.