| Scanning lidar can expand the space remote sensing detection capability of traditional lidar,so as to realize the rapid and large-scale real-time detection of atmospheric state in the region,as well as monitor the spatial and temporal distribution of aerosols near the surface,the location and diffusion of urban air pollution sources.Therefore,it is necessary to add scanning system to lidar system to realize remote sensing detection.The main research contents of this thesis are as follows:Firstly,based on the application of existing scanning system in lidar detection,the problems of vibration and inaccurate positioning are analyzed,and specific solutions are proposed.According to the technical index and solution of lidar scanning system,the mechanical system of lidar scanning is designed.In the transmission structure,a two-stage deceleration systes of double arc-tooth synchronous belt drive and self-locking ZA worm drive is designed.The total deceleration ratio of azimuth and pitch structure is 1:40 and 1:58 respectively.Verification analysis shows that the bending stress of worm drive is 1.38MPa,which is less than the allowable bending stress of its material 32MPa.Thin-wall ball bearings were used as pitch rotation motion pairs,and cap type conductive slip rings were used as horizontal motion pairs.A mechanical limit is designed to limit the pitching rotation system to a operating Angle of-45～45°.The stress simulation analysis of the whole mechanical system is carried out by Simulation,and the resonance simulation analysis of the worm drive seat and the frame part is carried out.The resonance frequency of the worm seat is between 6k～11kHz,and the resonance frequency of the frame is between 4k～4.2kHz.Secondly,the lidar two-dimensional scanning control system based on ARM core is developed,RS422 transceiver circuit based on ISL3173 chip is designed,and GDT(Gas developed,RS422 transceiver circuit based on ISL3173 chip is designed,and GDT(Gas Discharge Tube)and TVS(Transient Voltage Suppressor)are used to carry out secondary surge protection for serial port.A two-phase stepper motor driver chip A3986 was designed,and the full bridge circuit was used to realize the motor subdivision drive.The digital photoelectric sensor is used as the horizontal zero and pitch limit.LM75B chip is used as the temperature sensor to monitor the ambient temperature,darlington transistor chip ULN2803 is used to drive the relay and heating plate,so that the system can work normally at low temperature.The closed-loop simulation of the control system is carried out by Simulink,and the PID parameters are adjusted by attenuation curve method,and the PI parameter values with small steady-state error are obtained.Finally,based on the advantages of RS422 full-duplex differential long-distance communication,the special communication protocol of lidar is designed to realize the functions of manual adjustment and automatic control(fixed point mode and scanning mode).In the VS development environment,the upper computer of lidar scanning system is developed using C#language,and the trapezoidal acceleration and acceleration calculation method is adopted.The two-phase stepper motor is driven by the resolution of 0.0028° level and 0.0019° elevation on the upper computer,and the azimuth Angle of 360 degrees and the elevation Angle of-45～45° are realized.The upper computer sets the speed to the integer value of 0～6°/s,avoiding the resonance frequency of the system and reducing the vibration of the system.The experimental results show that the maximum positioning error of the scanning control system is 0.01° when the maximum load is 50kg and the maximum speed is 6°/s.The whole mechanical movement is stable and the vibration and noise are small,and the desired accuracy of 0.05° is achieved. |
PDF Full Text Request