Trajectory Optimization And Active-Disturbance-Rejection Control System For Gliding Guided Projectiles

The range-extended precision guided projectiles with the advantages of low cost,rapid response,high combat effectiveness,good damage effect,and small incidental loss,become one of the key development directions of the future guided weapons.In this dissertation,a type of range-extended gliding guided projectile equipped with the rocket assisted engine and two pairs of canard surfaces is considered as the subject.Focusing on some theoretical and technical problems during the research process,the trajectory optimization,guidance law and control system design scheme of this type of guided projectile are investigated.Firstly,based on the flight characteristics of low-spin gliding guided projectiles,a nonlinear six degree of freedom rigid ballistic model is established via defining the relevant coordinates with the rotation sequence of pitch-yaw-roll.To facilitate the design of the control system,alternative representation of the dynamic model of the center-of-gravity motion and center-of-mass rotation is presented,as well as the control coupling model of actuators in the non-spinning body coordinate.Next,the performance index model for the trajectory optimization of guided projectile is studied.Considering the glide capability and maneuverability of gliding guided projectiles,the concepts of glide efficiency,maneuver efficiency and composite efficiency factor are proposed.The characteristics of the composite efficiency factor and its influence on flight state parameters are also analyzed.A glide trajectory optimization scheme during the glide segment based on minimizing the composite efficiency factor and simultaneously tightly constraining the canard deflection is proposed to achieve better results in the glide efficiency,while the correspondingly reserved glide ability and maneuverability are both strong.At the same time,the canard deflection commands are small and stable in the whole control process.Subsequently,the entire trajectory optimization scheme based on minimizing the composite efficiency factor model is proposed.The scheme minimizes the composite efficiency factor of the whole trajectory under certain constraints to optimize and determine the trajectory parameters of different flight phases,such as the initial flight-path-angle,ignition time of the rocket engine,and start-up time of the glide phase.Then,in view of the limited flight control authority and guidance information of gliding guided projectile,a concise control model is built,and the guidance law with the characteristic of low requirements for sensors and actuators,high efficiency and precision is researched.A novel three-dimensional ballistic correction guidance law based on the combination of the correction of the velocity direction via impact-point prediction and the continuous distribution of acceleration commands within the control time is proposed to reduce the possibility of control commands saturation.Taking the proposed guidance method for terminal guidance as an example,the characteristics of each component in the ballistic correction guidance law are analyzed,and the selection range of relevant control parameters are also given.At the same time,the proposed two methods for solving the direction angles corrections of the current speed based on the deviation between the preset target and the predicted impact point are also compared and analyzed and their applicable conditions are given as well.Finally,the related issues of control system design for gliding guided projectiles are investigated.One,considering the problem of acceleration tracking of gliding guided projectiles in the case of the uncertain internal and external disturbances and the lag response of canard deflection commands,a nonlinear active disturbance rejection pitch acceleration tracking controller is designed.This scheme does not depend on the exact mathematical model and only needs measured acceleration information.Two,taking the influence of factors,such as cross-coupling dynamics,actuator response delay,induced control coupling effects,uncertain internal and external disturbances,and constraints of the control capability and system complexity,in the design of attitude control system for gliding guided projectiles into account,the active disturbance rejection and decoupling attitude autopilot is designed.Three,a novel active disturbance rejection decoupling acceleration autopilot with less measurement information is proposed for gliding guided projectiles.Unlike the traditional two/three-loop autopilot,only the measured accelerations are directly adopted as feedback in the proposed autopilot to reduce the cost and the system complexity.The control parameter is reflected in the form of closed-loop bandwidth and easy to adjust.The designed acceleration autopilot not only has the decoupling tracking effect of quick,high precision,and no overshoot,with the characteristics of the strong disturbance-rejection ability,robustness and adaptability,but also can effectively avoid the control saturation and oscillation,which is beneficial to guarantee the flight stability.In addition,aiming at the problem that there are large errors and phase lag in the transition process arranged for the discrete input signals with large change via the traditional tracking differentiator which is used in the architecture of the active disturbance rejection control,an adaptive mesh tracking differentiator is proposed.