Research On Key Technologies Of Multi-beam Several Photons Detection Lidar

Space autonomous navigation is the process of calculating and controlling the flight path of a spacecraft to achieve its intended target,mainly relying on the relative position and attitude information of the target provided by the high-precision sensor system carried by itself.Lidar is one of the sensors with high resolution,small size and high precision.Combined with computer vision technology,it can measure the relative position,velocity,azimuth and relative angular velocity of dynamic targets in a wide range,which becomes an important part of the autonomous navigation system.Lidar is a new technology based on laser ranging technology.To achive 3D imaging,it inverts and merges the whole angle-angle-distance information of all laser spots obtained by covering over the target surface.For lidar applied in spatial autonomous navigation,in order to reduce image distortion and distortion caused by relative motion,extremely high requirements are imposed on single imaging rate and image resolution.However,the imaging rate of Lidar mainly depends on the time taken by the laser footprint to completely cover the target surface.For traditional unit detection,it uses single beam laser emission,and the imaging rate is slow.Large-area flash lidar can completely cover the target with a single laser emission,but its resolution is limited on the other hand.On the contrary,the multi-beam laser scanning method can greatly reduce the scanning imaging time while achieving high resolution,and meet the application requirements of high resolution,large field of view and fast imaging.However,as the laser beam increases,the power consumption and volume of the Lidar system will increase accordingly.Under the same laser emission energy,the working distance is greatly reduced.In recent years,the emerging photon counting imaging lidar develops and can reduce system power consumption.However,photon counting detectors are difficult to distinguish between noise and signal echo,and with dead time effects,causing problems such as noise filtering and real-time data processing in multi-beam Lidar system,which also difficult to use on spatial autonomous navigation.The significance of this thesis is to propose a working mode combining the detection of several photons sensitivity and multi-beam scanning.The 64-beam highprecision scanning lidar prototype is designed to reduce the energy requirement of the laser without filtering and denoising the point cloud data,which satisfies the requirements of high resolution,large field of view and fast scanning imaging in spatial autonomous navigation.The main contents and innovations of the dissertation can be summarized as follows:1.A new laser ranging method based on the sensitivity of several photons was proposed and the principle was analyzed.Combining with the lidar equation,the several photons response model was established.A theoretical framework for system design based on multi-beam fast scanning(100ms),large vision(20°×20°),and high resolution(512 pixels × 512 pixels)imaging lidar was constructed.2.For the application requirements of high-precision three-dimensional imaging of moving targets,the speciality of response in the several photons working mode was modeled and analyzed on the time axis.The sources of laser ranging errors were also analyzed.Finally,the design scheme of multi-beam several photons detection lidar was given.3.The prototype of the multi-beam scanning lidar based on several photons was built and related experiments were carried out.The results show that the proposed several photons high-precision method is feasible and the ranging accuracy of the system is up to 1 cm at 1 sigma.In 3D point clouds imaging,plane thickness is better than 5cm of multi-beam lidar prototype,which can effectively identify the boundary of the target.For static targets,the relative pose resolution accuracy is better than 2°.For the rotating target within 25°/s,the rotational speed measurement error is better than 2°/s.