Narrow-band active damping using higher-order band-pass control: A loop-shaping perspective

Lightly damped structural resonances limit the performance of high-precision mechatronic systems and flexible structures. Conventional active damping schemes, such as positive and negative position feedback, provide moderate damping at the targeted mode but often suffer from spillover at low and high frequencies, especially in systems with closely spaced modes or high noise sensitivity. This paper presents a generalized higher-order band-pass active damping framework that enhances modal selectivity and stability for narrow-band damping. Analytical formulations establish relationships between controller order, band-pass slope characteristics, and stability margins, enabling systematic design with high phase robustness. A non-minimum-phase filter is incorporated to compensate for delay-induced phase degradation, while a tunable damping coefficient increases design flexibility. The framework is evaluated experimentally on a collocated nanopositioning system, through closed-loop simulations using an experimentally identified non-collocated beam response, and through a numerical study of closely spaced resonances. The results demonstrate that the proposed controller achieves sharp resonance suppression, improved noise attenuation, reduced spillover compared to conventional active damping schemes and modal selectivity distinguishing preservation of untargeted resonance peaks from aggregate vibration reduction.