Research On Attitude And Height Measurement System Based On Dual Laser Scanners And Its Calibration Technology

Vehicle-mounted multi-sensor platform is widely applied in 3D reconstruction of street view, unmanned vehicle and road damage detection. In order to realize location, navigation and data fusion of sensors, real-time and high-precision measurement of attitude and height of platform relative to ground are needed.To meet with the measurement needs proposed above, our group made a research on attitude and height measurement system based on dual laser scanners, which functioned well in measurement of attitude and height for vehicle-mounted multi-sensors platform, and took the advantages of convenience of installation and low cost. However, research on the system was just in the beginning. Therefore this thesis made a further study on the measurement mechanism, measurement error and calibration technology.Firstly, principle and error of attitude and height measurement system based on dual laser scanners was studied. The principle of the system was introduced in detail, by which the source and transfer of the measurement errors were analysed. For the influences of performance, structure of laser scanners and measurement environment on the measurement precision of system, the corresponding methods to decrease the influences were analysed and researched by simulations.An extrinsic calibration method of laser scanner based on target reconstruction was proposed to calibrate the system. Analysis on mathematical model of calibration of system was made, by which the calibration of system was formulated as extrinsic calibration of laser scanner in the system. And according to the running characteristics of laser scanner, the calibration method was put forward on the basis of transformation model of 3D coordinate system based on space vector, in which a trihedron target was designed, and through reconstruction of the target, segmentation of point cloud of target using RANSAC algorithm and extraction of features, the system was calibrated. Feasibility and precision of the calibration method was analysed in simulations, and the method was successfully used in calibration of the system in actual experiments.Effect of methods for error processing and calibration in improving precision of system was proved based on the experiment platform for verifying the measurement precision of system. First the measurement errors and processing methods were summarized. Experiment platform was built to verify the measurement precision of system, as the coordinate system of system did not coincide with that of turntable, correction model of attitude angles based on the principle of least square method was deduced to estimate the precision of system. By the reference of attitude value of turntable, the improvement of measurement precision by adopting the methods for error processing and the calibration was verified, and eventually, the measurement precision of the system on pitching angle and rolling angle were improved to 0.034°and 0.023°respectively.