A Wire-Driven Series Elastic Mechanism Based on Ultrasonic Motor for Walking Assistive System

In order to improve the elderly people's quality of life,supporting their walking behaviors is a promising technology.Therefore,based on one ultrasonic motor,a wire-driven series elastic mechanism for walking assistive system is proposed and investigated in this research.In contrast to tradition,it innovatively utilizes an ultrasonic motor and a wire-driven series elastic mechanism to achieve superior system performances in aspects of simple structure,high torque/weight ratio,quiet operation,quick response,favorable electromagnetic compatibility,strong shock resistance,better safety,and accurately stable force control.The proposed device is mainly composed of an ultrasonic motor,a linear spring,a steel wire,four pulleys and one rotating part.To overcome the ultrasonic motor's insufficient output torque,a steel wire and pulleys are smartly combined to directly magnify the torque instead of using a conventional gear reducer.Among the pulleys,there is one tailored pulley playing an important role to keep the reduction ratio as 4.5 constantly.Meanwhile,the prototype is manufactured and its actual performance is verified by experimental results.In a one-second operating cycle,it only takes 86 ms for this mechanism to output an assistive torque of 1.6 N·m.At this torque,the ultrasonic motor's speed is around 4.1 rad/s.Moreover,experiments with different operation periods have been conducted for different application scenarios.This study provides a useful idea for the application of ultrasonic motor in walking assistance system.

Immediate effects of the honda walking assist on spatiotemporal gait characteristics in individuals after stroke

The use of unconstrained lower limb exoskeletons has become a promising approach to assist individuals with gait impairments.The Honda Walking Assist(HWA)is a hip-assistive exoskeleton functioning as a gait trainer and has been shown to improve several gait related outcomes after training.Studies investigating its immediate effects on spatiotemporal gait parameters other than walking speed in stroke survivors are lacking.The aim of this study was to investigate immediate differences in spatiotemporal gait parameters of stroke survivors between normal overground walking,walking with an unpowered,non-assisting HWA and walking with an optimally assisting HWA.Five ischemic stroke survivors(mean time since stroke 115±213.6 days)walked 3 times 5 m in each condition.Differences in 14 spatiotemporal gait parameters between all 3 conditions were registered and reported in a descriptive manner.With optimal assistance,4 patients walked faster(0.057–0.095 m/s)with longer strides of the paretic(0.055–0.069 m)and non-paretic(0.053–0.077 m)leg compared to normal walking.Compared to unpowered walking,all patients walked faster(0.020–0.063 m/s)in the optimal assist condition,with longer strides of the paretic(0.036–0.072 m)and non-paretic leg(0.045–0.082 m).During unpowered walking,gait velocity remained unchanged in 2 patients,increased(0.012_0.051 m/s)in 2 patients and decreased(-0.022 m/s)in 1 patient compared to normal walking.Changes in paretic stride lengths ranged from-0.066 to 0.029 m.The optimal individualized motor assistance provided by the HWA induces small,positive changes in gait parameters.This indicates that this light-weight hip-assistive exoskeleton can be of value in rehabilitation setting,where multiple training sessions with the device are possible.