Evaluating the performance of robust controllers for a nanopositioning platform under loading

Piezoactuated nanopositioners are an integral component in Scanning Probe Microscopes (SPM). The imaging application of SPMs necessitate the loading of the nanopositioning platform with various samples. This causes an increase in mass thereby altering the dynamics of the system. Various methods have been proposed to control uncertain systems such as H_∞ robust control, µ-synthesis and mixed µ-synthesis. Additionally, low-order damping controllers, such as Integral Resonance Control (IRC) and Positive Position Feedback (PPF), have been shown to be robustly stable via the negative imaginary lemma. In this paper, IRC is used as a benchmark for robust performance, and robust controllers are developed using the aforementioned methods. It is found that the best performance, in terms of the H_∞ norm over the range of uncertainty, is achieved using the IRC control scheme. In addition, IRC provides more accurate tracking of a reference signal.