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Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract:
Reducing the impact of seismic activity on the motion of suspended optics is
essential for the operation of ground-based gravitational wave detectors.
During periods of increased seismic activity, low-frequency ground translation
and tilt cause the Advanced LIGO observatories to lose `lock', reducing their
duty cycles. This paper applies modern global-optimisation algorithms to aid in
the design of the `sensor correction' filter, used in the control of the active
platforms. It is shown that a particle swarm algorithm that minimises a
cost-function approximating the differential RMS velocity between platforms can
produce control filters that perform better across most frequencies in the
control bandwidth than those currently installed. These tests were conducted
using training data from the LIGO Hanford Observatory seismic instruments and
simulations of the HAM-ISI (Horizontal Access Module Internal Seismic
Isolation) platforms. These results show that new methods of producing control
filters are ready for use at LIGO. The filters were implemented at LIGO's
Hanford Observatory, and use the resulting data to refine the cost function.
