Multivariable methods for helicopter flight control law design: a review

The design of flight control systems for actively controlled helicopters presents problems which are associated not only with the complex nature of the dynamics of the vehicle itself but also with the range of design objectives which must be satisfied. The techniques of multivariable control system design provide tools of potential value for helicopter flight control applications. The paper describes an approach which has been developed for the comparison of multivariable design methods using control law design criteria which can be related to handling quality requirements, robustness, noise rejection properties and insensitivity to atmospheric disturbances. The definition of the flight control task for these comparative investigations involves a reduced design problem with performance measurements based on linearised models