The Study for Detecting a Dangerous Situation through the Application of 3-dimensional Triangle Model

Four‐wheeled walker is designed for assisting walker, but it cannot handle all unusual walking trouble. Moreover, if walker user is disabled person or senior citizen and cannot control it in some problem, he or she will be in danger. For preventing this, we should know what situation is the dangerous situation for walker user. In this study, several states of walker is defined in use with its factor which related to walker moving and relation with its user. Also, we suggest a model that classify the states as stable or abnormal one. The target four‐wheeled walker. for the research is standard form of walker, and we assume that the slowing it make its user to avoid precarious situation. The abnormal state is divided into four status that the distance between walker and its user are too long; that its acceleration is too strong because of a steep incline; that the wheel of walker fall into a hole; that the wheel of walker fall downstairs. The raw data, its distance to its user, frontal and horizontal angle, and acceleration, are collected to define the abnormal states of walker numerically. The present study proposed a model that discriminates a dangerous situation by using raw data from two sensors(accel-gyro sensor(mpu6050-GY521) and ultrasonic range finder(HY-SRF05)). Accel-gyro sensor measured acceleration(A), horizontal degree(θ), and vertical degree(θ‘). Ultrasonic range finder measured a real time distance(S) between user and Walker. The model is composed of three points(triangle) on three-dimensional region and affected by distance, degree, and velocity. Firstly, for calculate each points of the model, the center of range finder's cradle was set as ground point. And then the front and back of the user was set as x-axis, the left and the right as y-axis, and the up and down as z-axis. After we assume that the width of Walker is w. Then we can set the first fixed point of the triangle as (0, w, 0). The other points moving fluently. So if we could get the coordinates of them, the area of triangle can be calculated. One other point is the center of user. This coordinate((s+0.5*a*t*t), 0, 0) moves following x-axis. The final point is located in the opposite of first point relative to xy-plane. But this point(-w*tan(θ), -w, -w*tan(θ’)) become to be far from the ground point when the Walker's frontal and horizontal symmetry is collapsed. In consequently, if the user faces a dangerous situation, the area of triangle will change according to the distance, velocity and degree. In six kinds of abnormality situation, the area(m×m) of ​​the triangle is calculated iteratively by this model to identify abnormality situation. The area of the triangle is between 0.35 and 0.55 in case all experimental conditions is stable. Also, if the area of the triangle is more than 0.80, experimental conditions enter the abnormality situation. As a result, it is general state in normal situation in case the area of the triangle is between 0.35 and 0.55, it is dangerous state in case the area of the triangle is between 0.55 and 0.80, and it is a state in which the need to control the wheels in case the area of the triangle is more 0.80. This research can make recognizing the status of four‐wheeled walker immediately and taking proper sequencing action for elderly person to use walker.