Study On Rapid Self-positioning Scanning Measurement And The Combination Measurement Method Of The Large-scale Workpiece

Three-dimensional coordinate measurement is the main means of geometric measurement.With the limitation of measuring precision and efficiency,traditional single point measurement devices cannot meet the measurement requirement of the large-scale workpiece.Conversely,scanning method can acquire so much surface and appearance data that it is widely used.Among the scanners,handheld scanner,without the external fixation device,has received much attention because of easy operation and high measurement efficiency.Therefore,in this paper,we proposed a structured light scanner based on the binocular stereo vision and the inertial navigation in order to realize rapid self-positioning scanning measurement.However,for the large-scale workpiece measurement,scanning is not the best solution.Because the measured volume is so large that the number of image matching increases obviously and errors are accumulated.So it's necessary to study the combined method of the global controlling and the local measuring.So in this paper,a combined method based on laser tracker and handheld scanner is presented.The main researches in this paper are described as follows:1.The structured light scanner based on the binocular stereo vision and the inertial navigation is designed.The system consists of the structured light measurement unit,the binocular stereo vision and the inertial navigation unit;2.System parameters are calibrated.It is composed of camera calibration,the light's center coordinates extraction,light-plane calibration,position calibration between two cameras and the performance test of inertial navigation unit;3.Mathematical model of the combined method is set up.The multi-sensor data fusion algorithm is used to ensure the conversion accuracy.We make experiments with different length by the handheld scanner and the combined method respectively to validate the feasibility of the combined method.4.A large-scale gear rim is measured by the combined method.The surface is reconstructed by Imageware based on the model of NURBS surface.The total error of measurement and reconstruction is 0.10 mm.