Guidance And Control Approach For Single Moving Mass Controlled Reentry Vehicle

The centroid of the moving mass controlled reentry vehicle is altered by changing the position of the internal moving mass,which generates additional aerodynamic torque to control the attitude and trajectory.Among them,the single moving mass controlled reentry vehicle(SMMCRV)which controls the roll channel has been widely concerned.Compared with the multi-moving mass controlled reentry vehicles,it has advantages of simple internal layout,fewer actuators and so on.However,it can only control the roll channel directly,and the stability of the pitch and yaw channels depends on its static stability,which brings many difficult problems to the research of the guidance and control methods.For example,the divergence of the pitch and yaw channels caused by the saturation and severe motion of the actuator;it is difficult to control the angle of attack directly,which leads to the large dispersion of terminal velocity;the lift force is uncontrollable,which leads to line of sight rate unable to converge to zero,affecting the accuracy of tracking ground targets;it is difficult to accurately track range and velocity at the same time with the single bank angle,which affects the guidance accuracy.Therefore,the dissertation takes the SMMCRV as the research object,and proposes the control,guidance and integrated guidance & control(IGC)methods.The research work of this dissertation mainly includes the following aspects:The mathematical models of SMMCRV are built,including the centroid motion model,motion around the centroid model,the relative motion model and so on.Combined with the established models and the open-loop numerical simulations,the difficulties of guidance and control method design caused by the coupling and under actuated characteristics are analyzed,which lays the foundation for the follow-up research of guidance and control methods.During the reentry phase,some problems of tracking attitude command should be paid attention,such as actuator input saturation,exceeding power constraint.Aiming at aforementioned problems,an improved prescribed performance control method based on quantitative saturation auxiliary system is studied.Firstly,the attitude control design model is obtained by simplifying the mathematical model of motion around the centroid.Then,the finite-time extended state observer is designed to estimate the ignored items.By compensating the disturbance in the control law,the robustness of the system is improved.Furthermore,the singular problem of the controller is avoided by studying the novel performance function and the error transformation function and the improved prescribed performance control method is designed to reduce the overshoot of the roll angle response.On this basis,the auxiliary system is designed to quantify the saturation degree/ risk,and the input saturation of the actuator is reduced by adjusting the input of the actuator.Finally,the nonlinear limiter is employed to meet the power constraint and reduce the influence on the stability of the SMMCRV caused by the severe motion of the moving mass.In the dive phase,it is difficult to control the miss distance,the velocity and the impact angle accurately with the bank angle at the same time.In order to solve the above problem,a finite-time guidance law is proposed based on the virtual target with time varying velocity.Firstly,the variation trend of error angle command is designed to reduce the roll speed based on the relationship between the convergence of the error angle and the roll speed.On this basis,the virtual target is employed,of which position is adjusted by the feedback of the speed deviation.Then,the terminal velocity dispersion is reduced by adjusting the deceleration time.After that,the strategy of landing point prediction is adopted to transform the problem of tracking maneuvering target into the problem of attacking fixed target.Furthermore,the virtual target with time varying velocity moving along the desired direction is also employed to achieve the goal of tracking the maneuvering target with desired angles.In the reentry phase,it is difficult to control the speed and the range at the same time by using the single bank angle.Aiming at the aforementioned problem,the guidance method is studied,which is adjusted adaptively based on the range deviation.Firstly,a variable weight guidance command updating method and improved B-spline fitting method are proposed to meet the expected range and reduce the velocity dispersion at the handover point.Then,a reference trajectory tracking method considering relationship between the tracking deviations is proposed.By converting the speed deviation into the desired range increment,the high range tracking accuracy is obtained and the computational complexity of guidance command solution is reduced.Furthermore,combined with the finite-time guidance method in the dive phase,the terminal and process constraints are satisfied and the terminal velocity dispersion caused by the uncertainties of aerodynamic environment and vehicle parameters is reduced.Aiming at the divergences of pitch and yaw channels caused by the input saturation of the actuator and the violent movement of the moving mass during the high-speed rotation of the SMMCRV in the dive phase,the IGC method is proposed,considering the limited actuator capability.Firstly,the cause of actuator input saturation and the influence on the stability of the SMMCRV are analyzed.On this basis,the IGC method based on the virtual instruction preprocessing is proposed to reduce the input saturation.Then,considering the influence of the violent motion of the moving mass on the stability of the SMMCRV,the IGC model is built with actuator dynamics.Considering the stability and the terminal accuracy at the same time,the strategy of variable constraint amplitude is adopted.For establishing the relationship between the states of the guidance system and the constraint of actuator state,the auxiliary system is designed.On this basis,an IGC method considering the constrained displacement and velocity of the moving mass is studied and high terminal accuracy is achieved.