A fully flexible coaxial rotor UAV path tracking method based on virtual force analysis
[Objective]Coaxial rotor unmanned aerial vehicles(UAVs)are known for their robust driving force,flexible mobility,efficient energy use,high stability,and fault tolerance.However,their lightweight nature makes them prone to deflection by minor external forces,rendering them vulnerable to environmental factors such as airflow and gusts.At the same time,in the research of path tracking control methods for coaxial rotor UAVs,there is often a trade-off between simplicity and practical application.To address these challenges,this paper proposes a control method based on virtual force analysis to improve the anti-interference ability of coaxial rotor UAVs.[Methods]This paper establishes the dynamic model of a fully flexible coaxial rotor UAV based on a comprehensive analysis at the overall and local levels.At the overall level,the UAV is regarded as a rigid body,while at the local level,emphasis is placed on examining the flexible vibration characteristics of the connecting joint components,particularly the rotors.By analyzing the forces acting on the rotor,a deformation equation is obtained through full flexible modeling.The virtual force feedback control law is formulated based on virtual force analysis,enabling the UAV to navigate along a predetermined path while countering external interference.In addition,a long short-term memory network is used for path planning to address issues related to gradient disappearance and explosion.The algorithm unfolds in several steps:① Discarding irrelevant information from previous stages through the forgetting gate.② Filtering incoming data through the input gate and updating the cell with new information processed by the hyperbolic tangent layer.③ Refreshing the data by eliminating obsolete information and filtering useful information of the input gate.④ Outputting valid information after processing by the output gate.[Results]Simulation experiments commence with dynamic modeling of the UAV,followed by the design of a virtual force feedback control law that incorporates virtual forces and influencing factors.Subsequently,a proportional integral differential regulator is used,and stability analysis is carried out to construct the overall research model.The experimental results show that the UAV path tracking method delivers an effective tracking performance.Furthermore,it can stably adjust to changes in the desired attitude angle.However,when the attitude angle remains stable,the tracking attitude angle may fluctuate around the expected value.[Conclusions]Given the broad range of application scenarios and the variable environments in which UAVs operate,this paper proposes a path tracking method for fully flexible coaxial rotor UAVs based on virtual force analysis.Through detailed model analysis and simulation experiments,the proposed method is validated as superior and practical for path tracking and mitigating the impact of external interference.
virtual forcecoaxial rotor UAVpath trackingfull flexibilitycontrol law
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