Guaranteed Robust Tracking with Flatness Based Controllers Applying Interval Methods

Flatness based tracking controller design (see e.g. [4, 5, 16]) is one of the most important tools for the control of nonlinear systems. A drawback of this approach is the lack of methods for the robustness analysis of such controllers with respect to uncertain parameters in the plant. In [1] the application of interval methods has been proposed for the guaranteed robustness analysis of flatness based tracking controllers. This approach allows to explicitly calculate the deviations from the reference trajectory which are caused by uncertain parameters in the plant in a guaranteed way. In this contribution the analysis using interval methods is extended to the case when a nonlinear tracking observer is necessary to estimate unmeasured states. Furthermore it is shown that unknown sensor offsets can be included into this robustness framework. The approach is illustrated for a magnetic levitation system.