Robust multivariable control of an active acoustic grillage: Modeling, design and implementation

Active Noise Control has found wide application in recent years due to availability of fast computers, embedded and data acquisition systems. An Active Acoustic Grillage (AAG) is an array of sound sources and microphones forming an acoustic barrier trapping sound but allowing air and light to pass through. The objective of research reported in this dissertation is to apply multi-input-multi-output (MIMO) design methods and increase the system robustness while retaining or improving the performance in comparison with single-input-single-output (SISO) design. The AAG concept can be used for noise cancellation in ducts with relatively large cross-section. Although previously available distributed single-input-single-output (SISO) design provides an inexpensive and expandable system, the MIMO approach significantly improves stability and robustness of the AAG. Methods considered for controller design include Linear Quadratic Gaussian (LQG) and H_∞ mixed sensitivity optimization. Serious challenges are imposed by the non-minimum phase behavior and lightly damped acoustic modes. Several linear quadratic and robust controllers have been developed that provide 10–15 dB attenuation in the frequency range of 100–300 Hz. Benefits of MIM0 design are demonstrated on a test grillage. These results can be applied to other noise control systems with multiple sensors and actuators where cross coupling is significant.