Nonlinear H∞ Robust Control for Six DOF equations of motion of Rigid Body with Mass Uncertainty

This paper derives the analytic solution of nonlinear H∞ robust controller for a system with mass and moments of inertia uncertainties and investigates the implementation using control surface inverse algorithm. A special Lyapunov function with mass and moments of inertia uncertainties is introduced to solve the associated Hamilton-Jacobi partial differential inequality (HJPDI). The HJPDI is solved analytically, resulting in a nonlinear H∞ robust controller with simple proportional feedback structure. The control surface inverse algorithm (CSIA) is employed to determine the angles of control surface deflection from the nonlinear H∞ control command. The ranges that guarantee stability and robustness of nonlinear H∞ flight control system implemented by vehicle actuators are derived. Numerical simulation is carried out and the results show that the responses still show good convergence for large initial perturbation.