| The diversification of space missions has put forward higher requirements for the new generation of rocket technology.China's rockets also developed from conventional rockets to heavy rockets.The structure of heavy rocket is more complex and has more uncertain factors.Many key dynamic parameters cannot be accurately obtained through ground tests.In order to overcome the influence of these uncertainties,it is necessary to improve the adaptive ability of the rocket attitude control system.At the same time,the control system must have a certain fault-tolerant ability to ensure the reliability of the system for the fault of the rocket engine servo mechanism stuck.Aiming at the above technical requirements,this paper carries out the design and research of the rocket attitude control system based on L1 adaptive control method.The main contents include:(1)The attitude dynamics model of three-channel rocket considering elastic vibration was established.Taking pitch channel as an example,the attitude controller is designed based on PD control method,and the control effect is verified when the model parameters are changed.In order to eliminate the influence of rocket elastic vibration on attitude stability,the design of a wave trap was introduced and the effect of PD+wave trap on the attitude control of rigid-elastic coupling arrow was verified.(2)As the application basis of L1 control method,the theoretical basis and composition of two basic forms of L1 adaptive control(state feedback L1 adaptive control and output feedback L1 adaptive control)are analyzed.The expressions of state observer,adaptive law and control law are given respectively for the two L1 controllers,and the stability of L1 controller is illustrated by combining with related theorems.(3)Aiming at the parameter uncertainty problem of the launch vehicle model,the attitude control system of the pitch channel of the rocket is designed by using the model reference adaptive control method,state feedback L1 control method and output feedback L1 control method respectively.State feedback L1 method is compared with PD control and model reference adaptive control,and the advantages of L1 method are summarized.In the research of output feedback L1 method,the influence of the relationship between the bandwidth of the low-pass filter and the elastic frequency of the arrow on the system stability is analyzed.When the low pass filter of the controller can not solve the influence of the rocket's low order elasticity on the control system,a joint design method of the correction network and L1 adaptive controller is presented,and the validity of the method is verified.(4)The attitude control problem when the engine servo mechanism is stuck is studied.When a fault occurs,the engine generates a disturbance control torque.In order to ensure the reliability of the rocket attitude control system,the servo mechanism swing angle reconstruction strategy is proposed based on the design criterion of the actual control torque is equal before and after the failure.The rocket attitude control system was designed by combining the above swing angle reconstruction strategy with L1 adaptive control,and the simulation of various engine servo mechanisms was carried out to verify the feasibility of the designed swing angle reconstruction strategy. |
PDF Full Text Request