Active control of vibration: Displacement, velocity, or acceleration feedback?

Active vibration control is conventionally implemented through acceleration measurement, and integration action is usually exercised if the velocity and/or displacement feedbacks are required. It is not widely recognized that each feedback can enforce (possibly severe) restriction on design freedom, and such restriction can then put constraints upon system performance, even leading to infeasibility of performance specifications. The aim of the note is to investigate fundamental design constraints from each feedback, and further derive the corresponding performance limits. It remains to see that the analysis provides important information explaining why some design fails and how the specification is not realizable without carrying out the detailed design process. This also forms the contribution of the note.