Development of Prognosis system for Farm Work Accident Prevention Based on Chaotic Dynamics of Human Ear Plethysmography

农场工作事故的原因之一是机器操作员在做重复性工作时的意识水平下降。为了防止此类人为失误造成的农业生产事故，开发了基于耳容积脉搏波混沌动力学的预测系统。该系统由耳容积脉搏波检测传感器、内置AD转换器的耳容积脉搏波遥测仪和混沌分析软件组成。为了解操作者在静态和动态工作时的应激水平，进行了实验研究。混沌吸引子和李雅普诺夫指数在这项研究中使用。本研究的主要结果如下：1.静态作业时，用夹具拾取直径为2 mm的圆形物体并将其转移到另一个容器中，然后将一根棍子插入直径更大的孔中而不接触。实验结果表明，随着应力水平的增加，混沌吸引子发生变形，李雅普诺夫指数增大。2.动力学实验包括：围栏区偶尔刷草、倾斜草地上骑式割草机驾驶实验和倾斜平台上翻车的心理应激实验。实验结果表明，当草地倾角大于等于15°时，割灌机的发动机转速越高，作用在操作者身上的应力集中程度越大。因此，可以使用人耳体积描记法，使用混沌吸引子和李雅普诺夫指数来确定操作者精神压力的水平。

One of the causes of farm work accidents generated is the decreasing level of awareness of the machine operator when doing repetitive work. Then, to prevent the farm work accident by such a human error, the prognosis system based on chaotic dynamics of ear plethysmography was developed. The system is composed of the sensor for ear plethysmography detection, the telemeter to send and receive data with built-in AD converter, and software for Chaos analysis. Experiments were carried out to known the level of stress of operator when doing static and dynamic work. Chaos attractor and Lyapunov index was used in this study. The following are main results of this study.1.For static works, the following were carried out : picking round objects with 2 mm diameter using chopstick and transferring it to another container, and inserting a stick on a hole with bigger diameter without touching. The result of the experiment showed that there were deformation the Chaos attractor and increase in the Lyapunov index as the level of stress increases.2.For dynamic works, the following were carried out : occasional brushing of grasses on fenced areas, driving experiment on riding type mower in inclined grassland and mental stress experiment on car tipping over an inclined platform. As a result of the experiment, it was verified that the level of stress concentration on operator increases as the inclination of grassland angle becomes 15° and higher, and as engine speed of the brush cutter increased. Thus, the level of operator mental stress can be determine using a Chaos attractor and Lyapunov index, using human ear plethysmography.