Research On Fault Detection Method Of Elevator Braking Device Based On Line Structured Light

With the rapid development of urban modernization,the demand for elevators is increasing year by year,which puts forward higher requirements for the safety function of elevators.As the main brake component in the elevator brake system,brake device plays an important role.In the field of fault detection of elevator brake device,traditional detection methods are various,but there are some problems,such as low accuracy,labor-consuming,false detection and missed detection.In this paper,we use modem computer vision technology for reference to accurately and quickly obtain information in the image,discuss the common fault detection methods in the elevator brake system,and study the detection methods of the working state and brake clearance of the brake contactor,which has good theoretical basis and application value.The main research work of this thesis is as follows:(1)The structure of elevator brake device,common electrical and mechanical faults are analyzed,and the detection method of elevator brake device based on line structured light is determined.Gauss filter is used to remove the noise caused by the environment and CCD sensor in the image,and image normalization is used to solve the problem of low contrast caused by illumination intensity and optical properties of the object surface.(2)The calibration method of line structured light is studied.The internal and external parameters of the camera are obtained by calibration,and the actual size of the brake gap is obtained.The calibration principle and calibration method are analyzed,and the calibration method using Tsai two step method is proposed.Firstly,the camera parameters of the linear system are solved by the perspective matrix transformation method,then the parameters are taken as the initial values,and the distortion factors are considered.Then the calibration accuracy is improved by the optimization method.The advantage of this method is that the model assumes that the lens distortion of the camera is radial.No matter how the distortion changes,the vector from the image center to the image point direction remains unchanged,which significantly reduces the dimension of the parameter space.(3)The method of extracting the line structured light center is studied.The line structured light on the pre-processed image of the lock contactor and the image of the magnet block is extracted from the line structured light center.Aiming at the problem that the detection accuracy and speed can not be taken into account in the existing stripe center extraction methods,a stripe center extraction method based on the combination of Hessian matrix and region growth is proposed.The region of interest(ROI)of the image is extracted by adaptive threshold method,and the sub-pixel centers of line structured light are obtained by using Hessian matrix.The centers of light stripes are used as seed points for region growth iteration,so that the stripe centers can be accurately extracted.Compared with Steger method and gray center of gravity method,the results show that the processing accuracy of the proposed algorithm is the same as that of Steger method,but the processing time is significantly higher than that of Steger method.Compared with gray center of gravity method,the processing time of the proposed method is slightly slower than that of gray center of gravity method,but the processing accuracy is higher than that of gray center of gravity method.This method solves the problem of a large number of Gauss convolution operations in traditional methods,and improves the speed of extracting fringe centers.(4)On the basis of the strip center,the detection of elevator brake device is realized.The corner detection method is used to fit the line structured light fringes on the contactor with broken line distribution,and the working state of the contactor is monitored according to the equation of the straight line.A method of calculating the width of the brake clearance by calculating the difference between the coordinate value of the pixel points and the transverse component of the pixel points is proposed to quantify the brake arm and the brake wheel,which provides a theoretical basis for taking more targeted maintenance measures.