Proceedings Article | 25 March 2008
KEYWORDS: Control systems, Adaptive optics, Sensors, Network architectures, Actuators, Control systems design, Cameras, Switches, Telecommunications, Data communications
The communication architecture for most pointing, tracking, and high order adaptive optics control systems has been based
on a centralized point-to-point and bus based approach. With the increased use of larger arrays and multiple sensors,
actuators and processing nodes, these evolving systems require decentralized control, modularity, flexibility redundancy,
integrated diagnostics, dynamic resource allocation, and ease of maintenance to support a wide range of experiments.
Network control systems provide all of these critical functionalities. This paper begins with a quick overview of adaptive
optics as a control system and communication architecture. It then provides an introduction to network control systems,
identifying the key design areas that impact system performance. The paper then discusses the performance test results of a
fielded network control system used to implement an adaptive optics system comprised of: a 10KHz, 32x32 spatial selfreferencing
interferometer wave front sensor, a 705 channel "Tweeter" deformable mirror, a 177 channel "Woofer"
deformable mirror, ten processing nodes, and six data acquisition nodes. The reconstructor algorithm utilized a modulo-2pi
wave front phase measurement and a least-squares phase un-wrapper with branch point correction. The servo control
algorithm is a hybrid of exponential and infinite impulse response controllers, with tweeter-to-woofer saturation offloading.
This system achieved a first-pixel-out to last-mirror-voltage latency of 86 microseconds, with the network accounting for 4
microseconds of the measured latency. Finally, the extensibility of this architecture will be illustrated, by detailing the
integration of a tracking sub-system into the existing network.
