Research On Dynamics And Control For Single Moving Mass Flight Vehicle

The moving mass control(MMC)technology changes the center of mass of the system by adjusting the relative positions of the movable body and the shell inside the aircraft so that the control of the attitude of the aircraft can be changed by changing the aerodynamic arm.Compared with the rudder control,the advantage of MMC technology is that actuators are in vehicles that does not have to consider the ablation of the rudder surface.Therefore,this control method is suitable for the hypersonic aircraft maneuvering in the atmosphere.However,the moving mass would destroy the internal structure of the vehicle and increase the difficulty of designing the layout.Reasonable optimization of the layout of the moving mass is a prerequisite for engineering.In addition,the motion of moving mass will cause the inertia offset,this offset will not only lead to coupling between channels,but also cause the gyroscopic effect and increase the additional moment of inertia.Therefore,the dynamic system consists of the aircraft and the moving mass is a strongly coupled and nonlinear dynamic system.These factors make the dynamics of the aircraft complex,and raise higher requirements of control system design.In order to solve the conflict between moving mass layout and maneuverability,this paper first proposed a bank-to-turn control with a large moving mass and jet control.According to the proposed layout,a complete dynamic model is established,including attitude dynamics and moving mass dynamics model.To reveal the control mechanism of MMC,a detailed dynamic analysis is carried out.Based on the linear pitch channel model,the trim relation between the angle of attack and the deflection angle,the stability conditions,the control ability and the dynamic characteristics are studied.The results show that the mass ratio and relative distance of mass center are important parameters that affect the control mechanism of the flight vehicle.The vibration mode and bifurcation analysis of a complete nonlinear pitch dynamic system with moving mass dynamics are carried out by using multi-scale method and bifurcation theory.The coupled dynamics equations of the angle of attack and the deflection angle of the moving mass are established.Since motion of the moving mass with large mass ratio leads to cubic nonlinearities in the equations,the internal resonance of the system is excited and this phenomenon can not be revealed by the linear model.The multi-scale method is used to study the system resonance and the amplitude-frequency response relationship of steady-state solution under first-order approximate solution is given.In addition,the arc motion of the moving mass increases the nonlinearity,the change of the deflection angle,the overall parameters and aerodynamic parameters would cause the dynamic behavior change.Therefore,for the pitch attitude dynamics equation,the characteristics of open-loop nonlinear bifurcation are mainly analyzed from the influence of the overall parameters on the equilibrium state.The single parameter and double parameter bifurcation are solved,respectively.The stability and bifurcation points of the balanced branches are analyzed to provide reference for the further optimization of the overall parameters.The motion of moving mass leads to the change of the inertia,which results in additional moment of inertia and the coupling between the attitude and the servo system.Based on the coupling model,the degree of coupling influence is analyzed.The dual-loop controller is designed based on the theory of immersion and invariance(I&I).According to the difficulty of solving the PDEs,the target system is redesigned to simplify the design process.For some shortcomings of dual-loop control system,the integrated attitude-servo control system of pitch channel is designed based on I&I theory to improve the dynamic quality.Estimator is designed to compensate for aerodynamic parameter uncertainty.Based on the closed-loop system dynamics model formed by the integrated controller,the closed-loop nonlinear bifurcation characteristics of the closed-loop system are studied with the mass ratio and the command angle of attack as the bifurcation parameters.Aiming at the Hopf bifurcation appearing in the system,the complex motion caused by the limit cycle is further studied and the important dynamic information is provided for the design of the controller.For the multi-channel coupled control model,this paper proposes a coupled controller based on I&I theory.The roll channel and yaw channel are coupled by the additional inertia,the original system is converted into a cascade system by using the coordinate transformation method.Then,the I&I controller is designed based on the new cascade system.The results show that the proposed underactuated control not only reduces the energy consumption but also reduces the control logic difficulty of the jet engine compared with the full-actuated control.Finally,the terminal guidance law of the moving mass flight vehicle is studied.Based on the instantaneous sight rotation,a dual-second order dynamic model is given,and the intercepting conditions are analyzed according to the characteristics of the motion camouflage theory.The further analysis of the intercept conditions and the relative motion model shows that the design of the 3D guidance law can simplify the design in two-dimensional instantaneous rotation plane of sight,which reduces the design difficulty.Finally,based on the estimation of target maneuver,the final guidance law of modified coring aircraft based on motion camouflage theory is given.