Control of nonlinear aircraft models using dynamic state-feedback gain scheduling

When designing flight control laws using linearisations of an aircraft model about dierent flight conditions, some form of scheduling of the resultant gains will be required to implement the controller over wide operating regions. In practice, the controller gains are often scheduled against slowly-varying system states such as altitude or velocity. However, it may also be desirable to schedule gains against rapidly-varying states such as angle-of-attack, . To obtain optimum performance it may be necessary to schedule a state feedback gain with that same state, creating a cyclic dependence. This paper presents a numerical method of accounting for this dependence when scheduling state feedback gains against themselves. The resulting dynamic gain schedule is shown to overcome some limitations normally imposed on conventionally scheduled controllers, and is shown to improve transient response in nonlinear regions. The controller design process, using eigenstructure assignment, is demonstrated on a second order longitudinal aircraft model.