Research On Ankle Waliking-assisted Device Based On Bowden Cable Transmission

As a device that can enhance the walking ability of human body,the WAD(walking assisted device)can reduce the energy consumption of muscles and prolong the walking time.However,there are some shortcomings in the current research of WAD: on one hand,rigid WADs have lower energy utilization because of the large weight of the device themselves;on the other hand,the main research of flexible WADs focuses on the index of reducing the metabolic cost of human body by improving the structure and control,and have not pay much attention to the topic of auxiliary efficiency.However,using less energy to reduce more metabolic cost of the human body is of great value for such research and product promotion.Therefore,exploring the factors that affect assist efficiency and using them to guide the improvement of energy utilization of WAD is what this paper needs to do.At the very beginning,this paper combines kinematic,anatomical,physiological and biomechanical analysis of human lower limbs to understand the important role of the ankle in driving the human body for gait switching and center of gravity transfer.On this basis,this paper proposes the bionic design principle of imitating the gastrocnemius-Achilles,and uses the servo motor-Bowden cable as the power device of the booster.Based on the theoretical analysis,this paper firstly designs a wearable WAD for free walking,with an overall mass of 5.2 kg.This preliminary result demonstrates the effectiveness of the flexible WAD.Compared to other studies,the initial prototype we designed had a smaller peak assist force but was able to achieve a significant metabolic cost reduction.Based on the effectiveness,we continued to explore the issue of WAD efficiency.We investigated the mechanical efficiency of the WAD under different weight by giving different levels of assist under different load-carried walking.By creatively introducing the concept of "critical force",we calculated the input and output work of the WAD in the critical state,and thus calculated the efficiency of the WAD.The experimental results confirm that as the load increases,the device needs to pay more mechanical work to offset the negative impact of the device itself on the human body.This paper on the mechanical efficiency of the WAD deduces the effect of the weight of the WAD and other negative effects on the mechanical efficiency in lower limb walking assist,and explains the importance of lightweight design of WADs from an innovative perspective.