Combination of H/sup /spl infin// and PI control for an electromagnetically levitated vibration isolation system

A control system, featuring a combination of H/sup /spl infin// and PI control methods for control in the vertical direction, of an electromagnetically levitated vibration isolation system was designed. Experiments were carried out to verify this system's noncontact levitation and microvibration control performance. The main components of this system are a vibration isolation table with built-in acceleration sensors for detecting microvibration, electromagnetic actuators with built-in electromagnets and displacement sensors, and a digital controller with the DSP. An H/sup /spl infin// controller was designed to be used for an augmented system which included a PI-type controller of relative displacement feedback. This H/sup /spl infin// controller enabled effective, noncontact stable levitation as well as vibration isolation. Experimental results by a test apparatus revealed that the designed controller yielded a 90% in vibration transmissibility in vertical-direction.