Study On Flying Trajectory And Control System Design For Rolling Guided Projectile

The guided projectiles are demanded to satisfy the tactical and technical index of "large range, big tenninal angle, high accuracy" in modern wars. As the actual flight process is a nonlinear, coupling, time-varying, constrained and effected by random outside disturbance control process, the flight trajectory and control system need to be designed well. Some theoretical and technical problems regarding the flight trajectory and control system design for canard guided projectiles are analyzed and studied in this paper.1) According to the aerodynamic, motion characteistics and rigid coordinate systems relationship of the canard configuration guided projectiles, the six degree of feedom flight dynamic model and attiude control system model are established. Based on instantaneous balance assumption, the longtitudinal particle trajectory equation of projectiles is proposed.2) A guidance scheme consisting of programmed guidance and terminal guidance is applied to achieve the tactical guideline of "large range, big hitting angle, high accuracy" effectively, the flight trajectory design is researched. Base on the guided projectile longitudinal partile trajectory equation, constraint conditions and the maximal range objective function, the extend range trajectory optimal model is established. The guided projectile optimal trajectory is obtained by parametric method combined with sequadratic programming. Based on3-DOF mass trajectory equation, the3-DOF nonlinear terminal guidance law with angle constraint is designed via differential geometry theory. The ballistic performance of guided projectiles in the terminal trajectory is analysed, the condition of minimum distance to hit the target is provided. Compared with traditional methods, the project trajectory has more advantages of ballistic performance, and the terminal guidance make the guided projectiles show some adaptability to different objects.3) Problems of trajectory reconstruction about drag coefficients, angle-of-attack and sideslip angle of guided projectiles are investigated using Kalman filter, smoother and Luenberger observer. Aiming at extracting drag coefficients from flight test data containing large measurement noise, a post reconstruction algorithm based on URTSS is proposed. Then the drag coefficients function of mach number is obtained, and the precision of other ballistic parameters is improved. A nonlinear Luenberger observer based on coordinate transformation for guided projectiles has also been designed for estimating the angle-of-attack and slideslip angle. The results provide some reference methods for these ballistic paramters that can not be acquired easily. 4) The nonlinear control method for guided projectiles is studied. Based on feedback linearization, the mass point and attitude nonlinear sliding mode controllers for rolling projectiles are proposed. Theoretical analysis and simulations indicate that the nonlinear sliding mode control is robust with respect to guided projectiles model error. However, lack of unkown dynamic parameters demand that the pure sliding mode control need to set big switching gain conservatively, which induce large control authority requirement, chattering or significant tracking error. In order to deal with dynamic parameters error, the symmetry property of rolling projectiles is analysed, parameter adaptive method considering boundary layer is introduced. Then an adaptive sliding mode controller (ASMC) applied to projectiles is proposed via Lyapunov stability principle. Simulation demonstrates that ASMC has good performance, and eliminates chattering caused by large paramter uncertainty.5) The discrete nonlinear control method for guided projectiles is studied. The accurate discretization method for nonlinear continuous system is introduced, the complex nonlinear systerm is converted to two standard subsystems equivalently via feedback linearization, then the subsystems are transformed into discrete-time systems, and a nonlinear discrete-time controller for guided projectiles is designed based on sliding mode control principle. Analysis shows, parameters of discrete reaching law and system uncertainties are the main source of chattering. In the case of other parameters certain, large contol sampling time or dynamic parameter uncertainties induce the tracking error and strong chattering. To reduce chattering caused by dynamic parameters uncertainties, the desceret parameter adaptive algorithm is introduced, then a discrete adaptive sliding mode controller (DASMC) applied to projectiles is proposed. Simulation demonstrates that DASMC can deal with large dynamic paramter uncertainties of guided projectiles, and improve control performance.6) The influence of various disturbance resources during the flight of projectiles is analyzed, and the performance of flight control is investigated. To reduce the rudder saturation caused by initial point deviation during the trajectory tracking segment, a transitional reference trajectory is designed. The smooth command information is derived by programming trajectory that guided projectiles fly along. Because of strong robustness of adaptive sliding mode control, guided projectiles are adapt to various situation with disturbance, also have good ballistic performance, and can hit the target with long-distance launching, big impact angle and high precision.