Robust Observer Design for Polytopic Discrete-Time Nonlinear Descriptor Systems

This paper considers the design of robust state observers for a class of slope-restricted nonlinear descriptor systems with unknown time-varying parameters belonging to a known set. The proposed design accounts for process disturbances and measurement noise, while allowing for a trade-off between transient performance and sensitivity to noise and parameter mismatch. We exploit a polytopic structure of the system to derive linear-matrix-inequality-based synthesis conditions for robust parameter-dependent observers for the entire parameter set. In addition, we present (alternative) necessary and sufficient synthesis conditions for an important subclass within the considered class of systems and we show the effectiveness of the design for a numerical case study.