An automatic fire searching and suppression system for large spaces

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ARTICLE IN PRESS 302 T. Chen et al. / Fire Safety Journal 39 (2004) 297–307 Y ¼ Y 2 cos o 2 Z 2 sin o 2 þ D sin o 2 ; Z ¼ Y 2 sin o 2 þ Z 2 cos o 2 þ D cos o 2 : ð4Þ Take Eq. (2) into (3) and eliminate Y 1 , the relationshipbetween Y and Z has an expression Y ¼ ðy 1 cos o 1 f sin o 1 ÞðZ D cos o 1 Þ þ D sin o 1 : ð5Þ y 1 sin o 1 þ f cos o 1 Take Eq. (2) into (4) and eliminate Y 2 , the relation between Y and Z has another expression Z ¼ ðy 2 sin o 2 þ f cos o 2 ÞðY D sin o 2 Þ þ D cos o 2 : ð6Þ y 2 cos o 2 f sin o 2 Solution of Y and Z can be obtained from Eqs. (5) and (6), as shown in Eq. (7). Y ¼ Dðy 2 f tan o 2 Þ½ðsin o 2 sin o 1 þ A cos o 1 B cos o 2 Þ=ðA þ BÞ D cos o 2 Š y 2 tan o 2 þ f þ D sin o 2 ; Z ¼ D A B ðsin o 2 sin o 1 þ A cos o 1 B cos o 2 Þ; ð7Þ where A ¼ðy 1 f tan o 1 Þ=ðy 1 tan o 1 þ f Þ; B ¼ðy 2 f tan o 2 Þ=ðy 2 tan o 2 þ f Þ: ð8Þ In the above equations, y 1 and y 2 are still unknown. Actually, they can be calculated from the pixel coordinates (i, j) of the images, because most of the CCD camera are of the same standard specifications. Suppose the CCD camera’s scanning area is known as H V pixels and h v m 2 , the relationshipbetween [y 1 , y 2 ] and [j 1 , j 2 ] can be found. y 1 ¼ðj 1 V=2Þv=V; y 2 ¼ðj 2 V=2Þv=V: ð9Þ Thus the fire position P(d,a) in the space is confirmed and expressed as pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi d ¼ Z 2 þ Y 2 ; ð10Þ a ¼ tan 1 ðY=ZÞ: ð11Þ 2.3. Working process Initially, the fire monitor is set at the horizontal-left limit position. Once a fire is detected by a fire detector in the system, the corresponding fire monitor will be activated. It will start searching for fire and be driven to the down-right limit position step-by-step (shown in Fig. 3). The fire monitor rests for a short time after each step. During this period of time, continuous images are captured from the CCD
ARTICLE IN PRESS T. Chen et al. / Fire Safety Journal 39 (2004) 297–307 303 Fig. 3. Fire monitor’s scanning process. 1: horizontal-left limit; 6: down-right limit. I II t 1 y fire monitor pivot fire monitor pivot x III t 2 fire monitor pivot IV Fig. 4. Aiming process when a fire is detected. camera and sent into computer to be processed by image fire detection algorithm [12]. In the searching process, the robotic fire monitor scans in horizontal direction for three times however, each time in a different vertical angle. If no fire is detected in the entire searching process when the fire monitor reaches its down-right limit, it will be reset to its initial position. Otherwise, the locating algorithm is employed. In the locating algorithm, the distance between the fire monitor and fire is calculated. The stepangle of the fire monitor is chosen as b (less stepangle can be chosen) which is the visual angle of the CCD camera, thus no protection area is skipped. By pivoting the fire monitor, we perform the calculation by the displacement at different time. Images I, II, III and IV in Fig. 4 show the searching and aiming movements.
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An automatic fire searching and suppression system for large spaces

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