Research Of Methods For Material Volume Measurement Based On Laser Triangulation

Some irregularly shaped materials often require real-time measurement of the volume. For example, in the process of sorting the courier, it is difficult to accurately measure the volume of the express, because express have different sizes and shapes. The traditional method of volume measurement of irregular object with artificial estimate or coordinate measuring machine. Artificial estimation use rules object instead of the dimensions of irregular to estimate the volume, this method is difficult to accurately calculate the object volume. Some limitations of coordinate measuring machine are presence, like:there is contact between objects, both the presence of measuring force, measuring time is longer, the need to compensate for the contact probe, soft material cannot be measured, etc. Therefore a method of fast, simple, small damage, high precision measurement of material surface shape or volume is important to improve production efficiency and reduce costs.Volume measurement method is researched based on laser triangulation method. Point source of light is generated by laser, and then through the optical system to produce line light source to scan section of material. Laser stripe is collected by fixed camera, and the image is transmitted to the computer. Therefore three-dimensional point cloud data of materials is calculated, the volume of materials is also calculated by integration. Camera calibration algorithm is analyzed and adopts Zhang Zhengyou’s camera calibration algorithm to complete the camera calibration. Calibration board is manufactured and the calibration system is completed. In the process of parameter calibration, parameters are reduced and piecewise dogleg algorithm is applied to improve the computing speed.In the process of image processing, the source of image noise and the noise effect on precision of measurement is analyzed. For improving the noise effect on precision of measurement, median method is applied. The system adopts the curve fitting method to calculate the center line of the structured light, Experiments show that the center line of the structured light can be calculated stability, accuracy achieve to sub-pixel level. In the process of calculating material volume, First mathematical model is establish and then two calculation methods of cross section area of irregular objects is analyzed, finally the volume of the irregular objects on the conveyor belt is calculated by integral.This system software is developed in Visual Studio 2010 programming environment, after a lot of experimental data show that the system measurement precision is 2.58%, meet the requirements of volume measurement of irregular object.