The Active 2004 conference in Williamsburg, Virginia, USA was once again a fascinating conference. The topics that were covered were very broad that included new types of acoustic sensors, algorithms, fundamental studies in active aerodynamic control systems, psychoacoustics, and many practical installations of active noise control systems.
It was interesting to hear the trend to steer away from large scale multiple input – multiple output control systems, and instead focus on the development of multiple independent single input single output systems. This is quite a change from the research in the early 80’s by Smith and Chaplin that proposed MIMO systems were need to prevent ‘fighting’ of multiple SISO systems.
Some researchers were also investigating limited communication between control systems. There is a spectrum between a fully coupled MIMO system and uncoupled multiple SISO systems. In between these two extremes is a region where there is limited communcation between the controllers.