Line of sight stabilization using advanced control techniques
Inertial line of sight stabilization is a disturbance rejection problem: the goal is to hold steady in the inertial space, the line of sight of a camera, which is carried on a mobile vehicle. H-infinity robust control techniques are well suited for this type of problem, in particular the Loop-Shaping approach which relies on classical frequency domain concepts. However, this approach results in high order controllers which are hardly implementable on the real time embedded electronic unit of the sight system.In this thesis, fixed order and fixed structure controller design methodologies are proposed. This development follows two main axis: - Fixed order H-infinity Optimization. First, fixed order controllers have been investigated through the LMI (Linear Matrix Inequalities) optimization framework. However the numerical efficiency of this approach is still limited, despite the large amount of research in this area since the 90’s. Then, we used recently developed and more efficient tools that recast the fixed order H-infinity synthesis problem as a nonsmooth optimization problem.- Adaptation to the H-infinity Loop-Shaping frameworkWe adapted the 4 block H-infinity criterion in order to include the weighting filters in the fixed order controller optimization, which enhance the final controller order reduction. Then, we proposed a fixed order controller design approach, based only on graphically tuning a target open loop frequency gain.