Design And Simulation Of Flight Control System Based On LQG/LTR Method

It is a common concern to achieve controllers that have excellent stability and performance robustness since the unmodeled dynamics can act to destabilize the control system and disturbances such as wind gust and also for sensor measurement noise can often act to cause unsatisfactory performance of a system. The linear quadratic Gaussian/loop-transfer recovery (LQG/LTR) is a design methodology which works in the multivariable frequency domain, and is exploited in this paper to design robust feedback control systems. Simulations results present its strong robustness and the decoupling speciality.The paper is organized as follows.Since classic robust design notions in the frequency domain are generally in SISO system, the extending of classical notions to MIMO system is first provided by using the notion of singular value. It follows the develop of Kalman filter and state-feedback control law which are individually guaranteed to have nice properties and the combination of them as a LQG controller relies on the separation principle. Then a modification technique of LTR is presented so that the performance characteristics employed in the original LQG design can be full recovered.Flight control systems designed for robustness are carried out using the LQG/LTR procedure. A set of typical aircraft modes, such as attitude hold, altitude hold, automatic landing, turn coordination, given heading and lateral bias modification are designed and simulated. Case studies demonstrate the design step for practical problems and desired properties in both frequency and time domains are achieved.A critical comparison is made between the LQG/LTR and PID controllers. Simulation results have shown suitable performance of the LQG/LTR controllers when systems are submitted to wind disturbances. The robustness of the LQG/LTR controllers significantly exceed those of the PID approach especially in the case that coupling exits between channels of the control system, and with less computation cost associated with the chosen of parameters.The paper concludes with a software package programmed for flight control law which has good interface and is convenient to use.Based on the investigation presented in this paper, the LQG/LTR controller is proved to be effective in achieving the control objects and represents a potential useful control methodology for flight control applications.