| Due to the characteristics of vertical take-off and landing,fixed-point hovering and full vector propulsion,the multi-rotor cyclocopter based on cycloidal propellers have the potential to carry plant protection equipment to accomplish tasks such as aerial spraying and seeding.However,the research on multi-rotor cyclocopter is still in its initial stage,for example,the overall design method needs to be further optimized,the spatial and temporal evolution law of complex flow field is not yet clear,which makes it difficult to clarify the transport mechanism and deposition distribution law of droplets in the process of aerial spraying.To address such issue,this paper conducts the following research:(1)A small lightweight quad-rotor cyclocopter prototype based on cycloidal propeller using carbon fiber and other lightweight and high-strength materials is designed,which has 35° and 40° pitch angles up and down,respectively.The 1:8 gear drive is chosen as the drive scheme for the cycloidal propeller,and a radio-driven control system based on microcontroller technology is designed for the small-scale cyclocopter.The overall size of the assembled cyclocopter is 880 mm × 740 mm ×500mm,weighing about 2.6kg(2)A three-dimensional high-fidelity aerodynamic model of a multi-axis cycloidal propeller UAV is established based on the hydrodynamic method and nested sliding mesh technique,aiming to reveal the complex non-constant and non-linear behavioral characteristics of the UAV blade generated under the high-speed rotational and rotational speed.The spatial and temporal distribution characteristics of the flow field of the UAV are calculated under different rotational speeds,different incoming flow conditions and different aerodynamic layouts,and the validity of the finite element model is verified by bench lift measurement experiments.The results show that the lift force of the UAV varies nonlinearly with the increase of rotational speed,and the aerodynamic coupling phenomenon between adjacent cycloidal propellers is obvious.The forward rotation scheme of the cycloidal propeller produces a more concentrated flow field distribution and stronger airflow in the local area,while the reverse rotation scheme has a uniform airflow strength but a wider distribution.(3)The experimental research on the law of underwash flow field of quad-rotor cyclocopter is carried out.Conducting wind speed determination tests in different areas of the underwash flow field of a quad-rotor cyclocopter based on the bench test method.The test results show that at the farthest height of 1.3m from the ground,the measured wind speed in the blade area is the largest,reaching 8.942m/s,while the measured wind speed in the transverse area is the smallest,at 2.593m/s;at the closest height of 0.3m from the ground,the measured wind speed in the transverse area is the largest,reaching 4.473m/s,while the wind speed in the longitudinal area is the smallest,at 3.040m/s;The test was carried out on a bench spraying test based on a quad-rotor cyclocopter.Under the test conditions set in this paper,it was finally determined that the highest droplet deposition ratio of 60.5% was achieved when the nozzles are fixed on the symmetrical surface of the UAV,the pump was turned on at70%,and the nozzle spacing was 20 cm,and the effective spraying width was the largest,about 1.2 m.The research results related to this topic can provide a reference for the overall design of the cyclocopter,and at the same time enrich the way of aerial spraying and sowing operation. |
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