Experimental Research Of Powerless Soft-wing UAV On Accuracy Landing Control Method

Soft-wing UAV is a new unmanned Aerial Vehicle.It has special structure and flight characteristics,which has the advantage compared to conventional fixed-wing and rotary-wing unmanned aerial vehicles.In the transport of goods,it has an extremely important role.Achieving accurate landings is critical to this system.At present,there are two problems concerning the precise landing.The first problem is that most of the homing route planning algorithms are one-time planning,poor adaptability to environmental changes,resulting in inaccurate landing.The second problem is that most of the current track-tracking algorithms are not robust against wind disturbance and have large deviation from expected path in flight.In view of the above two problems,this thesis presents a set of homing route planning algorithm and tracking algorithm,achieving the effectiveness of the algorithm evaluation.In chapter 2,this thesis mainly introduces the platform construction and experiment.Based on the experimental platform,the flight test of the actual remote control was carried out.Under the state of steady powerless landing,the lateral unilateral pull-down input excitation and output response data were acquired.Based on the input and output data,the identification of lateral model is carried out,and the identification model is validated by model cross validation method,which lays the foundation for the simulation of trajectory planning and trajectory tracking.In chapter 3,this thesis mainly introduces the homing route planning and adopts the Multi-phase homing strategy.Multi-phase homing is to divide the whole homing route segment into three segments,namely radial homing segment,coiling segment,and terminal landing segment.Genetic algorithm find the optimal coiling high circling radius,so that the final landing error is reduced.Taking into account the various interference during the flight,tracking error will gradually increase.One-time planning can not meet the demand.Therefore,this thesis substitutes the Bezier curve for the straight line of the terminal landing segment,and realizes the real-time planning,obstacle avoidance and path re-planning of the path segment and reduces the landing point error of the final planning path.In chapter 4,this thesis introduces a nonlinear trajectory tracking algorithm-L1 trajectory tracking algorithm,which is firstly applied to the Powerless Soft-wing UAV.Based on the expected trajectory segment generated in Chapter 3,three kinds of fake target points generation and tracking strategies are proposed for different track segments.In this thesis,two trajectory tracking algorithms are simulated and compared.The results show that the performance of the L1 trajectory tracking algorithm is better than that of the PID trajectory tracking algorithm under the condition with wind.In chapter 5,this thesis combines the above mentioned path planning and tracking to realize the re-planning of the end track and reduce the landing point error caused by wind disturbance and system tracking error.Finally,the Monte Carlo simulation method is used to evaluate the precision landing algorithm proposed in this thesis.The circular probabilistic error(CEP)is used as an index to evaluate the performance of the precision landing algorithm,and it is proved that the precision landing algorithm proposed in this thesis can be applied to the Soft-wing UAV.