Abstract:Aiming at the lack of door position detection function of subway civil air defence doors at present, there is a hidden danger that the civil air defence doors intrude into the boundaries of trains. A method of detecting the door position based on visual measurement is proposed. Image acquisition of calibration objects set behind civil air defence doors, after preprocessing the captured image, using the external parameters of the camera, coordinate transformation of the three characteristic points whose coordinates are known on the calibration object is carried out, and the light center of the camera to the plane of the civil air defence door is solved according to the knowledge of space geometry mathematics. The vertical distance and the angle at which the door turns. The experimental results show that the angle detection accuracy of the air defence door measured by this method is less than 1 degree and the distance detection accuracy is less than 25 mm, which meets the requirements of the air defence door detection accuracy.