The real dynamic thrust measurement system usually tends to be nonlinear due to the complex characteristics of the rig, pipes connection, etc. For a real dynamic measuring system, the nonlinearity must be eliminated b...The real dynamic thrust measurement system usually tends to be nonlinear due to the complex characteristics of the rig, pipes connection, etc. For a real dynamic measuring system, the nonlinearity must be eliminated by some adequate methods. In this paper, a nonlinear model of dynamic thrust measurement system is established by using radial basis function neural network （RBF-NN）, where a novel multi-step force generator is designed to stimulate the nonlinearity of the system, and a practical compensation method for the measurement system using left inverse model is proposed. Left inverse model can be considered as a perfect dynamic compensation of the dynamic thrust measurement system, and in practice, it can be approximated by RBF-NN based on least mean square （LMS） algorithms. Different weights are set for producing the multi-step force, which is the ideal input signal of the nonlinear dynamic thrust measurement system. The validity of the compensation method depends on the engine＇s performance and the tolerance error 0.5%, which is commonly demanded in engineering. Results from simulations and experiments show that the practical compensation using left inverse model based on RBF-NN in dynamic thrust measuring system can yield high tracking accuracy than the conventional methods.展开更多
Tiltrotor exhibits a conversion mode with strong nonlinear aerodynamic characteristics.The thrust characteristics of propellers are one of the crucial factors determining the performance of tiltrotor with electric pro...Tiltrotor exhibits a conversion mode with strong nonlinear aerodynamic characteristics.The thrust characteristics of propellers are one of the crucial factors determining the performance of tiltrotor with electric propulsion systems in the conversion mode,which is affected by multiple factors such as the advance ratio,tilt angle,and wing blocking effect.In the present study,a numerical method based on the overset mesh method is established to simulate the six degrees of freedom motion of real blade models,which is suitable for simulations of the continuous conversion mode of tiltrotor.Numerical simulations are conducted on the continuous tilting process of the propeller/wing system with various propeller advance ratios to analyze the variation and the underlying principles of propeller dynamic thrust,and to summarize the equivalent inflow velocity under different tilt angles during the conversion process.The results show that the propeller thrust increases as the tilt angle increases and the propeller advance ratio decreases.The uneven force on the advancing and retreating blades causes an increase in thrust oscillation amplitude.The advance ratio influences the total thrust by affecting the forward component of the thrust.The resultant force direction angle of the propeller in the conversion mode is 2°–10°greater than the tilt angle,and the difference in angle increases as the propeller advance ratio increases.A new formula for the equivalent inflow velocity of the propeller during the tilting process is summarized.This could help to estimate the dynamic thrust of the propeller in the conversion mode of tiltrotor.展开更多
文摘The real dynamic thrust measurement system usually tends to be nonlinear due to the complex characteristics of the rig, pipes connection, etc. For a real dynamic measuring system, the nonlinearity must be eliminated by some adequate methods. In this paper, a nonlinear model of dynamic thrust measurement system is established by using radial basis function neural network （RBF-NN）, where a novel multi-step force generator is designed to stimulate the nonlinearity of the system, and a practical compensation method for the measurement system using left inverse model is proposed. Left inverse model can be considered as a perfect dynamic compensation of the dynamic thrust measurement system, and in practice, it can be approximated by RBF-NN based on least mean square （LMS） algorithms. Different weights are set for producing the multi-step force, which is the ideal input signal of the nonlinear dynamic thrust measurement system. The validity of the compensation method depends on the engine＇s performance and the tolerance error 0.5%, which is commonly demanded in engineering. Results from simulations and experiments show that the practical compensation using left inverse model based on RBF-NN in dynamic thrust measuring system can yield high tracking accuracy than the conventional methods.
基金co-supported by the National Natural Science Foundation of China(No.52236002)the specialized research projects of Huanjiang Laboratory。
文摘Tiltrotor exhibits a conversion mode with strong nonlinear aerodynamic characteristics.The thrust characteristics of propellers are one of the crucial factors determining the performance of tiltrotor with electric propulsion systems in the conversion mode,which is affected by multiple factors such as the advance ratio,tilt angle,and wing blocking effect.In the present study,a numerical method based on the overset mesh method is established to simulate the six degrees of freedom motion of real blade models,which is suitable for simulations of the continuous conversion mode of tiltrotor.Numerical simulations are conducted on the continuous tilting process of the propeller/wing system with various propeller advance ratios to analyze the variation and the underlying principles of propeller dynamic thrust,and to summarize the equivalent inflow velocity under different tilt angles during the conversion process.The results show that the propeller thrust increases as the tilt angle increases and the propeller advance ratio decreases.The uneven force on the advancing and retreating blades causes an increase in thrust oscillation amplitude.The advance ratio influences the total thrust by affecting the forward component of the thrust.The resultant force direction angle of the propeller in the conversion mode is 2°–10°greater than the tilt angle,and the difference in angle increases as the propeller advance ratio increases.A new formula for the equivalent inflow velocity of the propeller during the tilting process is summarized.This could help to estimate the dynamic thrust of the propeller in the conversion mode of tiltrotor.
