Discrete-time well-conditioned observer design for two-output systems

It has been shown previously that the robustness of deterministic observers with respect to modeling errors, measurement bias and roundoff errors can be represented by a single performance index, κ ₂(P), the condition number of the observer eigenvector matrix. In this paper, based on the performance index, a robust observer design method is proposed for two-output systems where the observer gain can not be determined uniquely with respect to the desired observer poles. The proposed design method is evaluated in a spindle-drive simulation example where the load speed needs to be estimated based on the measured signals.