Efficiency Opitomization For High-altitude Propeller And Airship Control Considering Propeller Dynamic Model

The on-design optimization and off-design characteristic analysis were investigated in accordance to Vortex Lattice lifting line Method(VLM)theory.Then high-altitude propeller control scheme based on nonlinear observer system was proposed,as well as the performance of airship fly system considering propeller dynamic control was addressed.The paper was organized as follows:A simple approach to analyze the efficiency and propulsive characteristics of the high-altitude propeller in accordance to the VLM theory was proposed.The Computational Fluid Dynamics(CFD)method was used to obtain airfoil aerodynamic data.The optimal pitch angle and propeller blade chord length(along the radial direction)can be calculated by applying Lagrange multiplier method as well as using the information from the database.The propeller wake model saw helical slipstreams applied to both lightly and moderately loaded propellers.The proposed method was capable of identifying the optimal efficiency through varying the number of propeller blades,radius and the rotational speed.The relationship between the optimal efficiency and design parameters was then established.Newton method was performed on off-design characteristic analysis in accordance to the number of propeller blades,propeller radius,chord distribution and torsion angle distribution.Thrust coefficient,torque coefficient,and efficiency curves were described in a range of the advanced ratio.The results obtained by the proposed method were compared with CFD results.A novel propeller dynamic model combing with the 6-DOF airship dynamic model was proposed based on the off design characteristic curves of propellers.The propeller dynamic model directly considered the command torque of the motor installed in the propeller system as the control input,and a motor-propeller dynamic equation and a propeller thrust loss dynamic equation considering external disturbances and differences between flows on the propeller disk were proposed.The feedback control law based on the nonlinear state observer estimated the propeller thrust loss and Lyapunov function analysis was introduced to guarantee “input-to-state” stabilities of the feedback system and the nonlinear observer system.A comparative study was conducted using the new model presented in this paper and the conventional one.The simulation indicated that the proposed method could track three Cartesian positions and three Euler attitude angles better than the conventional one.Also,the consumed energy was much less,which was great of benefit to the energy use.Furthermore,the motor torque of the new dynamic model was less than that of the conventional model,which reduced the occurrence of the motor torque saturation problem.