Research On Flight Envelope Safety Protection And Control Technology For Compound Coaxial High-Speed Helicopter

Composite coaxial high-speed helicopter(CCHSH)is promising in military and civilian use with its advantages in speed and maneuverability.However,its complex aerodynamic and control structures result in lots of difficulties in research.This paper studies the flight safety boundary range and boundary protection control strategy of coaxial high-speed helicopter out of flight safety protection,which provides theoretical basis for improving the flight reliability and engineering realization of high-speed helicopter in the future.Firstly,the structure and control characteristics of CCHSH are introduced.A full-scale nonlinear mathematical model of the goal is established by modular design and mechanism modeling,whose rationality is verified by a trim mathematical model.Then the linear model is obtained by simplifies the nonlinear model with small perturbation linearization.Secondly,in view of the flight characteristics of CCHSH,three typical modes of controller are designed include low-speed,high-speed and transition sections.Considering the engineering implementation,the inner and outer loop control laws of each mode are designed in the classical control manner.Thirdly,aimed at the flight safety envelope problem of CCHSH,this paper uses the method of combining theoretical analysis and engineering experience to determine the key parameters needed to be protected,and generates common flight state boundary of high-speed helicopter by solving backward reachable and power balance.Considering the maneuvering redundancy and complexity of the transition phase,the equilibrium points of the transition phase are balanced.The security boundary of the transition section is determined under the constraints of the safety evaluation function.Finally,based on the flight control system designed above and the determined safe flight range,a security protection strategy is formed that is control quantity and instruction limitations are combined,and internal environmental protection is priori to outer loop protection.Neural network adaptive dynamic inversion is adopted for fast variable state variables of inner loop,whereas dynamic trim for slows of outer.The simulation whose results indicate that both methods can achieve the proper protection functions,verifies the feasibility,and effectiveness of the method.