Study On The Sailing Control Strategies Of Unmanned Sailboat For Lake Monitoring

For the current serious pollution of lake water in China and the lack of monitoring methods for dynamic parameters of water,this paper takes the unmanned sailboat for lake monitoring as the research object,and takes the autonomous monitoring of lake water environment by the unmanned sailboat as the research purpose.Through the combination of theory,simulation and experiment,the improvement of the sail angle of attack control strategy for virtual anchoring of lake water quality monitoring tasks and autonomous cruise conditions is studied.Firstly,the unmanned sailboat for lake monitoring is designed.The main scale of the design boat platform is determined by the scaling method,and the boat profile design and stability analysis are performed on the MAXSURF software to ensure the unmanned sailboat satisfies the sailing requirements with the roll angle of less than 15 degrees at 9m/s wind speed.Also,the key characteristic parameters of the target sail are designed based on the sail shape modification design method.Besides,the hardware circuit is built.A control system is formed,which uses STM32F103ZET6 as a controller and integrates multiple modules,such as wind direction and speed sensors,Attitude and Heading Reference System(AHRS)attitude sensors,Global Positioning System(GPS)position sensors,wireless communication modules,and solar power generation units.This system provides a reliable test foundation for the test verification of sail control strategies.Secondly,the aerodynamic characteristics of the target sail are researched.Using STAR-CCM+software to perform numerical simulation on the target sail,the target sail lift and resistance coefficient are obtained.Combined with the results of sailing force analysis,a joint assessment is made to establish the control strategy for sail angle of attack under maximum boost,and a range of 25 to 180 degree relative wind direction angle is proposed as the navigable area of the target sail.It lays a foundation for building sailing model and the comparative study.Then,the improvement of the sail angle of attack control strategy is studied.In the process of sail propelling a boat,the sail generates both thrust and side thrust.Under autonomous cruising conditions,the sail’s boosting force is beneficial to navigation,but the sail’s side thrust interferes with the boat’s normal navigation.However,under the virtual anchoring conditions,the slewing torque generated by the side thrust of the sail is beneficial to the slewing performance of the boat.This paper studies the unmanned sailboat which is applied for virtual anchoring of the lake monitoring field and the sail control strategy under autonomous cruise conditions.(1)Virtual anchoring conditions.Based on MATLAB/Simulink software,a sailing motion model based on the combined slewing motion of sail and rudder is established.Through the simulation study on the variation rules of the sailing gyration diameter and other parameters with the angle of attack of the sail under varying relative wind direction angles,a joint slewing diameter-speed evaluation mechanism is established to obtain the control strategy of the sail’s angle of attack with the smallest gyration diameter.(2)Autonomous cruise conditions.Based on the MATLAB/Simulink software,a sailing motion model based on the combined action of sail and rudder to determine heading is established.Through the simulation study on the variation rules of the sailing speed and other parameters with the angle of attack of the sail under variable relative wind direction angles,a joint speed-sail force evaluation mechanism is established to obtain the control strategy of the sail’s angle of attack under the maximum speed.Finally,a comparative study is performed on the improved results of the sail angle of attack control strategy.According to different control strategies,the autonomous navigation control program for the unmanned sailboat is written,and two sets of comparative tests are performed on slewing and fixed navigation.In the slewing test,the control strategy of sail angle of attack with the minimum slewing diameter and the maximum boosting force is adopted to test the left and right slewing motions of the unmanned sailboat.The results indicate that the control strategy of the sail angle of attack with the minimum turning diameter can reduce the turning diameter by more than 20%compared with the sail control strategy with maximum thrust.In the fixed navigation test,the sail angle of attack control strategies of maximum speed and boost are used to test the unmanned sailboat at 30°,60°,90°,120° and 150°respectively.The results show that compared to the maximum boost control sail angle of attack strategy,the maximum speed control sail angle of attack strategy can increase the speed by more than 4.9%.Compared with the traditional sail control strategy,the minimum gyration diameter and maximum speed control proposed in this paper have better applicability(significant superiority)under specific sailing conditions,which provides a new idea for the research of multi-operating sailing control of the unmanned sailboat.