Digital Rate Controller for the Control Reconfigurable Combat Aircraft Design Using Quantitative Feedback Theory

摘要

The objective of this thesis is to develop a digital controller using Quantitative Feedback Theory for a fighter aircraft with unstable, nonminimum phase dynamics that meets performance specifications despite surface failures. Aircraft design trends for highly maneuverable fighter aircraft are relaxing stability requirements in order to increase performance in the transonic and supersonic regions. However, as a result, the aircraft is statically unstable in the subsonic region which makes the flight control system critical to flight safety. The conventional approach to the flight safety problem is to provide multiple redundancy throughout the fight control system. However, QFT provides an alternative to excessive hardware. The three controlled states are the pitch, roll, and yaw rates. A weighting matrix is derived which linearly combines the nine control surfaces into three control inputs. The plant is converted to a certain plane using the Hoffman algorithm. Three constant gain controllers and three prefilters are designed for a single flight condition of 0.9 Mach and 30000 ft altitude. The controllers and prefilters are transformed to the z plane for simulation purposes. The design is simulated with healthy plant and 24 combinations of surface failures. Keywords: Control theory, Multivariate control. (KR)