Robust Synergetic Design of Structural Dynamic Engine Out Controllers in Parameter Space

Engine out is a design criterion for a large transport aircraft from the viewpoint of flight safety, handling qualities, and structural dynamics. A structural dynamic engine out controller covers these aspects, especially the reduction of the loads level at the vertical tail. It is designed by a new robust synergetic design method, using Ackermann's parameter space method (Ackermann, J., Robust Control, Springer-Verlag, Berlin, 1993, Chap. 11, pp. 307-353). It allows the combination of different controller structures, each of which satisfies specific requirements. This combination of controllers robustly satisfies all of the multidisciplinary requirements. Here, three controllers are combined: a standard lateral controller and a proportional-integral controller for safety and handling qualities and a structural dynamic controller, which robustly decouples the shear force at the vertical tail from the yaw rate. This unilateral decoupling controller achieves an early efficient yawing moment compensation before the pilot. The controller consists of a feedback of the yaw rate to the rudder. Thereby, critical flight and load conditions due to a delayed overreaction of the pilot are prevented. The three controllers are characterized by eigenvalue regions for the closed-loop system. These Gamma regions offer compromises between the conflicts in design goals. Using the parameter space method, this approach yields a set of robust controllers. A controller is selected and simulated on a nonlinear model.