Sliding Mode Control of Pitch-Rate of an F-16 Aircraft

Abstract The control of the longitudinal flight dynamics of an F-16 aircraft is challenging because the system is highly nonlinear, and also non-affine in the input. We consider a sliding mode control design based on linearization of the aircraft, with the the altitude h and velocity V (Mach number) as the trim variables. The design further exploits the modal decomposition of the dynamics into its short-period and phugoid approximations. The primary design objective is model-following of the pitch rate q , which is the preferred system for aircraft approach and landing. Regulation of the aircraft velocity V (or the Mach-hold autopilot) is also considered, but as a secondary objective. It is shown that the inherent robustness of the SMC design provides a convenient way to design controllers without gain scheduling, with a steady-state response that is comparable to that of a conventional gain-scheduled approach with integral control, but with improved transient performance. Finally, we apply the recently developed technique of “conditional integrators” to achieve asymptotic regulation with constant exogenous signals, without degrading the transient response. Through extensive simulation on the nonlinear multiple-input multiple-output (MIMO) longitudinal model of the F-16 aircraft, we show that the conditional integrator design outperforms the one based on the conventional approach, without requiring any scheduling. Keywords: F-16 Longitudinal Dynamics; Pitch-Rate Control; Sliding-mode Control; Integral Control; Model Following.