Navigation And Control Of A Small Unmanned Helicopter For Autonomous Landing On A Moving Platform

The ship based helicopter is now playing a more and more important role in modern marine application,for battle missions,the helicopter is usually used for marine reconnoitrer,anti-submarine,transportation,aerial alerting,electronic warfare and mine warfare.As the technology advances,the unmanned helicopter will take place of the traditional helicopters to complete the missions above.In order to be qualified of taking these missions,besides using payload,the unmanned helicopter needs to be able to autonomously take off and land on a moving platform.The thesis focuses on autonomous taking off and landing of the unmanned helicopter,it consists of three parts: the state description of autonomous taking off and landing on a moving platform,relative navigation algorithm based on IR markers and helicopter control system design.First the thesis gives the definition of the whole working process,and five sub-processes are defined.For approaching process,three methods are provided and comparison among them are presented.Landing window are determined by using Ship-Helicopter Landing Limits(SHLLs)method.For descending process,two methods are provided,each method is used for specified condition.In order to successfully land on a moving platform,the helicopter needs to determine the relative states between the platform and the helicopter.The thesis presents steep descent algorithm for AHRS and robust high-degree cubature Kalman filter for relative states estimation.Through simulation,the navigation algorithm is proved to be valid.The thesis presents the helicopter's mathematic model which includes the main rotor flapping,as the system exist severe coupling effect,it is hard to design the control system directly.The thesis assumes the helicopter is always in steady state,based on this hypothesis,the m athematic model is linearized and separated into two parts: lateral and longitudinal channels,then the cascading control loops are used.For yaw rate control loop,ADRC is used while PID is used for other loops.For heading,velocity and height control,feedforward compensation is used for improving the anti-interference.The thesis also presents the platform mathematic model based on Longuet-Higgins model,the platform model is then used for analyzing the interaction.Through relative control simulation,the results show that the control system is able to meet the requirements.Using F-25 B as the flying platform,the thesis takes some flying tests for helicopter control system,such as ADRC based rate control,attitude stabilized mode,forward flying,height fixed mode and path tracking mode.The results show that the algorithm fulfills control target very well.