Research On Rotation Angle Detection System Of Automobile Front-lighting Ball Based On Binocular Vision

The beam produced by the headlamp will be illuminated in the forward direction of the car when the car is driving in a bend.It can only illuminate the front part of the road surface,and it will produce a dead angle of illumination on the inside of the bend,which can not achieve better bend illumination.The Adaptive Front-Lighting System(AFS)adjusts the rotation of the Front-Lighting ball in real time according to the speed and steering angle of the car,so that the Front-Lighting ball can follow the body of the car,thus producing better lighting effect in the bend and effectively reducing accidents.In order to realize the accurate rotation of the bulb,it is necessary to measure its rotation angle accurately.At present,there are two main methods to measure the rotational angle of headlamp bulb: photoelectric encoder and photoelectric displacement sensor.The former can not detect the vibration error of the rotating shaft in the process of rotation.The latter is limited by the size of the sensor and the measurement range is small.In recent years,binocular stereo vision technology has become more and more mature.It has been widely used in space position and attitude measurement with good adaptability.The detection object of this article is G2 type lamp ball produced by Hubei Valeo Automobile Lamp Co.,Ltd.The angle measurement range should be greater than(±15 degrees)and the measurement accuracy should not be less than 0.2 degrees.Through binocular stereo vision technology and three-dimensional reconstruction of space points,this article realizes the measurement of the rotation angle of headlamp bulb of automobile,and completes the following work:Firstly,two CMOS industrial digital cameras are used to build a binocular vision measurement system.Aiming at this system,the acquisition software system is designed and developed.Secondly,the color recognition technology is used to identify the red circular marker feature points in HSV space,and then the center coordinates of the marker points are extracted by edge detection and center fitting.According to the basic theory of binocular stereo vision,the three-dimensional coordinates of the marker feature points are reconstructed by combining the internal and external parameters obtained by camera calibration,and the plane normal directions before and after rotation are obtained by threedimensional coordinates.The rotation angle of the bulb and the rotation matrix are calculated.Finally,the stereo vision calibration experiment of binocular camera is completed for binocular vision measurement system,and the stereo vision accuracy calibration of binocular camera is completed by using high precision turntable.When the measuring range of rotation angle is(± 30 degree),the measuring error of system rotation angle is less than 0.15 degree,satisfied the measurement requirement..