Active/passive counter-force vibration control and isolation systems

Active counter-force control has significant advantages over the more traditional motion based active vibration suppression for isolation of disturbance sources. In this paper, features of four specific actuators, two hybrid isolation struts, and three system level realizations are reviewed with a focus on vibration isolation/suppression to reduce cryocooler disturbance forces. All of the discussed hardware and systems are based on electromagnetic reaction mass actuators. Significant vibration reductions can be achieved with such systems. The best measured tonal performance for all three systems discussed exceeds two orders of magnitude (40 dB) of vibration reduction. Control bandwidth can exceed 500 Hz. The necessary actuators are also robust, compact, and lightweight. Two of the systems were realized with miniature actuators weighing 3.8 ounces (107 grams) and 3.12 ounces (88 grams) respectively. Such systems have significant promise for addressing critical vibration isolation needs for upcoming space missions such as SIM, NGST, TPF, SBL, etc., through isolation of on-orbit noise sources such as cryocoolers and reaction wheels. They could also be quite useful for terrestrial applications in telecommunication, manufacturing, and semiconductor processing industries.