The Robust Flight Control of an UAV Using MIMO QFT: GA-Based Automatic Loop-Shaping Method

Abstract

This paper presents a design method of the automatic loop-shaping which couples up manual loop-shaping method to genetic algorithm (GA) in multi-input multi-output (MIMO) quantitative feedback theory (QFT). The QFT is one of the robust control design methods to achieve a given set of performance and stability criteria over a specific range of plant parameter uncertainty. The design procedure of the QFT is developed in a constructive manner and involves several essential steps. In QFT controller design process, the most important step is the loop-shaping in frequency domain by manipulating the poles and zeros of the nominal loop transfer function. However, the loop-shaping is currently performed in computer aided design environments manually, and moreover, it is usually a trial and error procedure. To solve this problem, automatic loop-shaping method based on GAs is developed. Robust control techniques including the QFT are particularly useful for the design Unmanned Aerial Vehicle (UAV) because dynamics of UAV vary substantially throughout the flight envelope. The QFT loop-shaping is successfully applied to the enhancement of the robust stability and disturbance rejections performance of the UAV based on specific margin specifications.