Ascertaining fire phenomena moment by momentt in the course of their progression is essential to detect a fire in the early stage, to issue a fire alarm, to provide adequate instructions for evacuation and to take early action to extinguish the fire. Since a fire is generally accompanied by both physical and chemical phenomena, a multi-dimensional measurement using various kinds of sensors is needed to obtain precise information about the fire behavior. In a multi-dimensional coordinate space where each coordinate axis represents the output of each sensor, a point in the coordinate space (or a position vector) represents the state of the fire behavior at a given time. If we could set up a border in this coordinate space that distinguishes between a fire and a non-fire, we can make a fire/non-fire judgment by observing the motion of the position vector.
This paper describes (1) a filtering method to determine the primary direction of the position vector motion, (2) the determination of the fire/non-fire border, and (3) the experimental results of the fire judgment.
Three kinds of sensor, temperature sensor, smoke sensor and gas sensor, were used in our experiments. To determine the primary direction of the position vector motion in the three-dimensional coordinate space, unwanted fluctuations of the measurements need to be removed. To do this, we used a method that calculates the center of gravity among three points in the coordinate space. We chose this method because it gives equal filtering effect to each of the three axes, it provides a stable point among position vectors, and it requires less computation time.
We set up a non-fire area in the three-dimensional coordinate space based on the position vector motions obtained from a number of non-fire experiments. The non-fire area is expressed as a combination of three rectangular solids. Also, we discuss, using fire experiment data, how the position vector moves within the non-fire area and finally goes into the fire area. This discussion includes the determination of the current state of fire/non-fire behavior and a forecast for the fire, by observing the position vector motion.
We used Newton's backward interpolation formula for the fire progression forecast, and we found that we can forecast the position vector motion of one minute later using up to the second term of the formula. Also, observation of the position vector motion allows us to know the details of fire and non-fire behaviors: for instance, we can distinguish between cigarette smoke and cooking, and we are able to know that when the CO gas concentration is increased in the smouldering fire stage, there is, in the current state, a high degree of danger of ignition.
抄録全体を表示