| Belt conveyor is an important transportation tool for conveying solid bulk materials in industrial production,which has the advantages of long transportation distance,continuous operation and stable transportation.Real-time acquisition of the material transportation volume on the belt conveyor is an important indicator for achieving belt speed control.The development of a real-time and accurate material volume dynamic measurement system is of great significance to the safety of production and energy-saving optimization of enterprises.At present,the main methods used to measure the volume of materials on the belt conveyor are electronic belt scale,nuclear belt scale,ultrasonic rangefinder,etc.Electronic belt scale is cumbersome to calibrate and has many sources of errors.Nuclear belt scale uses radioactive materials and has safety hazards.Ultrasonic rangefinder has poor anti-interference ability.The material volume measurement system based on line structured light has the advantages of simple structure,low cost,high accuracy,and easy promotion.In recent years,it has been gradually used for dynamic measurement of the volume of materials transported on belt conveyors in industrial production.According to the actual needs of material volume measurement on the belt conveyor,this paper analyzes the principles and limitations of the existing material volume measurement methods,and determines system calibration principle based on the homography transformation,and the material surface line is extracted by the weighted gray barycentric method.Contour line fusion is based on multi-angle imaging,double-speed sampling is realized by the separation method based on double line structured lights,and a material volume measurement system on the belt conveyor based on double cameras and double structured lights is designed.The main research work is as follows:(1)The fusion method of material surface contour line for multi-angle imaging is given.Combined with the system calibration information,the material surface contour lines collected from different angles are mapped to the world coordinate system for contour fusion,which effectively reduces the loss of the material surface contours collected from a single perspective due to the occlusion between materials,and obtains a more real and complete material surface contour.The complete surface contour line of the material greatly reduces the detection error caused by the occlusion between the materials.(2)The double-speed sampling method of the double line structured lights is given.The double line structured lights are used to irradiate the surface of the material,and the double line structured lights stripe separation method based on straight line fitting and two-dimensional search is used to accurately separate the double line structured lights stripe.Two contour lines are processed at the same time in one sampling,which effectively solves the problem of too large sampling interval caused by the fast moving speed of the belt conveyor in actual production and realizes double-speed sampling under the condition of the same camera frame rate.(3)Based on the QT platform and C++ programming language,a software system for dynamic measurement of the volume of materials on the belt conveyor is developed.The volume of ordinary coal and sand was measured by verifiable experiments at different belt speeds respectively,and compared with the measurement results of traditional single-camera and single-line structured light system.The maximum error of traditional measurement system volume measurement exceeds 10%,while the maximum error of this system volume measurement is 4.71%.The experimental results show that the measurement accuracy and stability of the material volume measurement system based on double cameras and double line structured lights given in this paper are better than traditional measurement system when materials are occluded and at higher belt speeds,with simple structure,accurate measurement,safety operation,broad research prospects,and convenient for promotion and application. |
