Objective Falling is a great threat to the physical and mental health of the elderly. In view of the problems about the complicated structure of the existing fall protection device and the unsafe way to inflate the gas,this paper designs a mechanical device based on detecting and tripping inflate automatically, which can help the elderly avoid injuring by the air bag inflatable protection when they accidentally fall. Methods The protective device was composed of a compressed carbon dioxide gas cylinder, an inflatable mechanism and a protective airbag. Firstly, the protective module used CO2 as aeration source, and the transmission mechanism used a high-power steering gear to drive the rotation of the coaxial cam. With the cam rotating, the puncture needle with linear motion punctured the gas cylinder. Secondly, The tensile machine was used to test the puncture needle ' s strength of piercing cylinder, and then selected the appropriate torque servo according to the maximum piercing force and the cam drive. Finally, the gas-kinetic isentropic flow formula was used to predict the airbag inflation time. Results The students whose height was between 163 cm and 174 cm were tested to imitate the gait of the elderly about performing forward, backward and side fall tests respectively, and measured these three ways to fall in the time of (865±41.49) ms,(788±53.56) ms, and (852±65.37) ms respectively;simultaneously,the air balloon inflation was (441± 29.6) ms by simulating the airbag inflation process. Comparing the fall time obtained by the experiment with the inflating time of the airbag, we know that there was ample time for the airbag to inflate during the fall of the elderly,and verified the feasibility of using compressed carbon dioxide to realize the fall protection with the airbag inflation. Conclusions The fall protection device based on the fall detection can achieve the fall protection and reduce the damage caused by the fall. The device has the advantages of simple structure, high reliability and low price, and is suitable for popularization and application.%目的 跌倒对老年人身心健康有着巨大威胁.针对现存跌倒防护装置结构复杂且充气方式不安全等问题,设计一套基于检测跌倒能自动充气的机械装置,以帮助老人在意外跌倒时能够通过气囊充气防护免受伤害.方法 该保护装置由压缩二氧化碳气瓶、充气机构和保护气囊3部分组成,首先防护模块以CO2为充气源,传动机构采用大功率舵机带动同轴的凸轮旋转,随着凸轮旋转刺针直线运动刺破气瓶;然后采用拉伸机对刺针刺破钢瓶力度进行测试,进而通过最大刺穿力和凸轮推程选定合适扭矩舵机;最后利用气体动力学等熵流公式预测气囊充气时间.结果 对身高在163～174 cm的学生进行测试,模仿老人步态分别进行向前、向后和侧面跌倒实验,测得3种方式跌倒的时间分别为(865±41.49)ms、(788±53.56)ms和(852±65.37)ms;同时通过模拟气囊充气过程,获得气囊充气时间为(441±29.6)ms.将实验获得的跌倒时间和气囊充气时间进行对比可知,在老人跌倒过程中有较为充裕的时间为气囊充气,验证了利用压缩二氧化碳对气囊充气实现跌倒保护的可行性.结论 本跌倒防护装置在跌倒检测的基础上,能够实现跌倒防护、减少跌倒带来的伤害,且装置具有结构简单、可靠性高、价格低廉等优点,适宜于推广应用.
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