Lateral Axis Autopilot Design For Large Transport Aircraft: An Explicit Model-Matching Approach

In this paper we describe the application of a technique favoured by GE engineers for linear multivariable control law design to an autopilot design problem for large transport aircraft. The method is based on an explicit model matching approach in the frequency domain, whereby compensator parameters are tuned via a least-square approach to minimize the error between a desired and the actual closed-loop frequency responses. This method was first proposed by John Edmunds in 1979 and has been in use at GE since the early `80´s as part of the CLADP design package. Recently, the design method has been overhauled to incorporate some of the latest theoretical advances, including controller parameterization and plant factorization. The resulting design technique has been considerably streamlined and is now implemented within the ISICLE package, a PRO-MATLAB based toolbox. One of the unique features of the ISICLE design package is the ability to deal with constraints on the compensator dynamic order and structure in a straightforward manner. Such constraints often arise in practical problems from the necessity for reduced complexity in the compensator, in order to effectively deal with issues such as gain scheduling and limit protection.