The Ligo Suspended Optic Digital Control System

The original LIGO suspension control system [1] used analog circuitry to implement the closed loop damping required for local control of each of the suspended optics. As installation and commissioning activities have progressed, it has become apparent that these controls do not provide the performance and flexibility that will be required for operation of the interferometers. Recent developments in ADCs, DACs, increased processor speed and performance, and the use of reflective memory have made a digital alternative possible. This paper will describe the real-time digital servo control systems that have been designed, developed and implemented for the LIGO suspended optics. In addition, the paper will describe how the suspension controls have been integrated into the overall LIGO control and data acquisition systems [2].