A design of low-order active noise controllers in a small cavity

We designed low-order controllers for active control of acoustic noise in a small cavity. The conventional robust control synthesis methods usually give controllers with the same or higher order than the generalized plants, and these controllers are difficult to handle and to be implemented. Any implementation error would make the performance of the system degrade, or even make the closed loop system unstable. Therefore, it is necessary, if possible, to find a lower order controller with a similar performance of a full order controller. We use a convex optimization algorithm with a nonlinear equality constraint to find a controller with predetermined order. To verify the performances, the designed controllers are implemented with TMS320C31 DSP, and their performances are compared with that of the full order controller. The results show that the low order controllers have almost same performances as the full order one. Therefore, the designed low-order controller could be used more efficiently in practice.