Research On Key Techniques Of Remote Sensing UAV System For Surveying And Mapping

With the development of modern remote sensing technology,there are a lot urgent requirements for the high spatial resolution,high spectral resolution and high time resolution local area remote sensing products in the field of surveying and mapping,land use planning,electricity,police,urban construction,etc.The research of small surveying UAVs become a new hotspot because the UAVs have the advantages of flexible,convenient,All-weather,no space constraints,low cost,and carrying a variety of payloads.This paper mainly focus on key technologies of small UAV remote sensing systems,such as autopilot,navigation algorithms,three-axis-stabilized platform,camera calibration research,etc.The main work and innovations are as follows:1)To meet three key technologies requirements of navigation data fusion based on multi-source and multi-sensor information,strip photography based on fuzzy control flight and three-axis stabilized platform for need of hardware systems,the design and realization of small autopilot system architecture,circuit parameter calculation,component selection and prototype production work have been completed.2)In the basis of a full analysis of SINS(Strapdown Inertial Navigation System),GNSS(Global Navigation Satellite System),air navigation and magnetic navigation on the autopilot hardware design,the utility integrated navigation algorithms used centralized Kalman filter were given.The Simulation results show that the integrated navigation have more obvious advantages of improving system stability and the accuracy than independent navigation system.The heading angle error was 0.28°(dynamic range 10°),the roll angle error was 0.39°(Dynamic range 10°),the pitch angle error reached 0.77°(dynamic range of 40°),the horizontal error was 2.25 m and the height error was up to 0.7m,After Kalman filter.3)According to national standards of aerial photogrammetry,the control precision standard of UAV flight control and triaxial self-stabilizing PTZ were proposed,the Fuzzy-PID control algorithm of UAV flight and triaxial stable PTZ have been designed and implemented.Experiments show that,the fuzzy-PID controller was the better than classic controller in the terms of step response time,undershoot,overshoot,settling time,steady state error and stability,but rise time was the worse than classic PID.Especially the overshoot characteristic is very conducive to stability control UAVs.The rise time of Fuzzy-PID was 0.13 s slower than classic PID 0.05 s,but within an acceptable range.The flight experiment showed that strip deformation was the less than 2.5% and the maximum error of flight height was 5m.Indoor precision experiments and real flight test showed that the index has reached or exceeded the design requirements.It met requirements of the large-scale stereo topographic map in small area.4)For non-metric CCD digital camera features and the needs of rapid field non-metric cameras calibration,the error sources was detailed analyzed and a mathematical calibration model has been founded.Both detailed multi-image group iterative method for solving DLT coefficient,the elements of interior orientation and distortion parameters of lens and the multi-image resection method for solving the elements of interior orientation,elements of exterior orientation and distortion parameters of lens have been discussed.A standard steel cage has been made for real calibrating non-metric cameras outside quickly.In order to verify the accuracy,each method mentioned has been used to solve elements of interior orientation and distortion parameters with the same camera and the same test images.The the results of accuracy show that the maximum X error was 0.2585 mm,the maximum Y error was 0.6719 mm and the maximum Z error was 0.1319 mm by using multi-image DLT algorithm.On the other hand,the maximum X error was 0.1914 mm,the maximum Y error was 0.9808 mm and the maximum Z error was 0.1453 mm by using multi-image resection algorithm.The forward intersection accuracy of the two methods was quite,and the both were less than 1mm.By using multi-image DLT algorithm the planimetric accuracy was less than 0.2585 mm and the height accuracy was less than 0.6719 mm.On the other hand,by using multi-image resection algorithm the planimetric accuracy was less than 0.1914 mm and the height accuracy was less than 0.9808 mm.The planimetric accuracy of resection algorithm was the better than DLT algorithm,but the elevation accuracy of DLT algorithm was the better than resection algorithm.In summary both method can be accepted for non-metric camera calibration.But also the solver accuracy in the inner orientation elements and distortion parameters was not high has been noted.However for non-metric camera,the true value of inner orientation elements and lens distortion were unknown did not affect the accuracy of photogrammetry.