Study of High Order Dynamics Effects on Flight Control Systems

This work presents a study of different architectures for fly by wire flight control, emphasizing the dynamic effects of time delays and data conversion processes generated by the insertion of digital computers and electronic components into the control loop. High order dynamic effects, made up of processing delays and the dynamics of sensors, converters and filters are investigated. The influence exerted by each one of these elements is assessed by means of sensitivity analyses, which are performed on the longitudinal model of a civil aircraft. Aiming at higher levels of safety, it is suggested that the control laws design processes incorporate these associated dynamics inherent to the fly by wire approach. In fact, if, on one hand, the introduction of electronic components into flight control architectures has brought a number of operational and technical advantages, on the other it has become necessary to take into account their dynamic behaviour during flight control laws formulation and design, at the risk of aircraft-pilot coupling phenomena occurrence. Comparative analyses, based on Matlab simulations, show that the components which have greater effect on the longitudinal mode responses are pitch sensors, notch filters and computational delays.