Research on uncertainty minimum ellipsoid envelope model of laser measurement system

In order to effectively evaluate the three-dimensional spatial distribution of measurement errors of the laser measurement system, a new uncertainty model based on the calculation of the minimum envelope ellipsoid was proposed. Based on the measured or simulated location data, the isolated forest algorithm was introduced to filter out abnormal data in the point cloud. With the valid data, the minimum envelope ellipsoid uncertainty model was established based on the particle swarm optimization and the error ellipsoid theory. By the coordinate system transformation between the measurement field and the single point uncertainty, the minimum envelope ellipsoid model was applied to the spatial uncertainty distribution analysis. Through the test of the measured data of a single point and a 10m-level space scene, the model can efficiently screen the sampling data and perform different levels of minimum envelope ellipsoid calculations according to the requirements. And then the corresponding uncertainty can be obtained. The results show that based on the measurement position data, the model can efficiently and accurately describe the three-dimensional uncertainty range of a single point position, and can effectively reproduce the uncertainty distribution in the measurement space. With the experimental conditions of a measurement distance 4.7m, the effective data after screening 94.2%, and an envelope ratio 97.5%, an ellipsoid with an uncertainty range of three-axis length 4.95μm, 18.39μm, 30.53μm is obtained by the model calculation. The minimum envelope ellipsoid uncertainty model has important value in many aspects, such as theoretical model verification based on actual measurement, equipment state and measurement environment analysis, and measurement layout design.