Mechanism Analysis And Suppression Of Limit Cycle Of Elastic Aircraft

Modern missiles are characterized by high speed,light weight and super maneuverability.Therefore,in the design,the slender shape of the missile can reduce its resistance during flight and ensure fuel reserve.If the body is still analyzed according to the traditional rigid body dynamics model,and the influence of elastic deformation is not considered,the designed controller will be difficult to ensure the stability of the actual system and even cause damage to the missile.It can be seen that the adverse effects of elastic deformation on the system cannot be ignored.The steering gear is an essential part when controlling the attitude of the missile.The components in the actual steering gear are affected by various aspects such as design,production and processing.There are some non-linear factors,which may cause the system to generate a "limit cycle" oscillation with constant frequency and amplitude,which will damage the system performance.Therefore,it is very important to study the mechanism of the nonlinearity of the steering gear causing the limit ring oscillation of the elastic aircraft and how to suppress this oscillation.Accurate dynamics model is the basis of attitude control analysis.Therefore,the basic theory of modeling is introduced in this paper.The dynamic model of rigid elastic body and the vibration model of elastic body are established under the relevant coordinate system.Subsequently solve the transmission of the pitch channel to prepare.Secondly,this paper analyzes the working principle of each component in the steering system,lists the relationship equation between the variables,and gives the transfer function of the rudder loop according to the relevant parameters;the condition and stability of the limit cycle based on the description function method The theoretical analysis was carried out;and two nonlinear characteristics in the steering gear were analyzed.Thirdly,the transfer function of the rigid projectile and the elastic projectile pitch channel is solved respectively.According to the Nyquist stability criterion,the stability of the longitudinal channel of the missile under the condition of no nonlinearity and different nonlinear parameters of the steering gear is analyzed.The rigid elastic body and elastic body are designed with a PID controller.Through simulation analysis,the dynamic performance and steady state of the system are improved.Finally,an optimized second-order sliding mode variable structure controller is designed for the problem that the PID controller is difficult to meet the control performance of the missile's pitch channel with dead zone nonlinearity.In order to verify the control effect of the controller,it is applied to the rigid body and elastic body of the servo with dead zone respectively.The simulation results show that the control results are better than the PID controller.