No abstract

No abstract

The objective of this paper is to review recent advances in the sensors used to measure seismic linear vibrations at low frequencies. The main types of inertial sensors are reviewed: absolute displacement sensors, geophones, accelerometers, and seismometers. The working principle of each of them is explained, along with the general strategies to extend their bandwidth. Finally, the principle fundamental limitations of all inertial sensors are reviewed: tilt-to-horizontal coupling, zerolength springs, and sources of noise.

a b s t r a c tThe future Compact LInear particle Collider (CLIC) under study at CERN will require to stabilize heavy electromagnets, and also to provide them some positioning capabilities. Firstly, this paper presents the concept adopted to address both requirements. Secondly, the control strategy adopted for the stabilization is studied numerically, showing that the quadrupole can be stabilized in both lateral and vertical direction. Finally, the strategy is validated experimentally on a single degree of freedom scaled test bench.

This paper reviews recent patented developments in active vibration isolation. First of all, the fundamental limitations of passive vibration isolations are established, to understand the motivations to introduce active control in vibration isolation. Then, the main different active strategies are presented using simple systems and compared. Finally, several specific issues are listed and briefly discussed.