Robust Pitch Autopilot Design Based on Logarithmic Barrier Lyapunov Method

Abstract

When the phased array radar-guided missile intercepts a high speed target with large maneuvering, the aerodynamic parameters of the missile body vary dramatically and become nonlinear, which affects the response of the control system to the large angle-of-attack, the robust autopilot control law should be designed considering the tracking error constraint of the angle-of-attack command. A robust nonlinear autopilot control law is designed based on the double power reaching law and logarithmic barrier Lyapunov function can make the tracking error of the angle-of-attack command converge to the constraint range rapidly. The aerodynamic parameter uncertainty and external disturbance of the system are estimated and compensated online by using the reduced order extended state observer. Stability analysis and numerical simulation show the angle-of-attack can reach a steady state within 1 second and the steady-state error of the angle-of-attack response<10-4°.The proposed autopilot control law has strong robustness, can accurately and stably track the command of angle of attack, control the missile produces the required overload accurately to intercept the target.

Keywords

• |barrier lyapunov function|double power reaching law|robust nonlinear autopilot|extended state observer