An adaptive method for designing a robust IMC structured feedback active noise controller

In this paper, a method for designing a robust internal model control (IMC) structured feedback active noise controller is considered. For feedback active noise control (ANC) systems, the IMC structure is preferred because of the possibility of applying an adaptive filter in the controller and the simplicity of satisfying the stability if an accurate secondary path model is available. In practice, however, model uncertainties exist so that the robust stability of the controller must be considered during the controller design process. Moreover, the waterbed effect for feedback control of a time-delayed system will cause noise amplification (NA) at some frequencies out of the target band of control. Against these problems, this paper proposes a controller design method in which a constraint for the control filter coefficients is found to ensure the robust stability and limit the NA caused by the waterbed effect to within a given value. In comparison with the design process in the frequency domain, this method can use an adaptive algorithm to obtain a robust controller solution in the time domain. Once the time domain constraint has been obtained, it can also be used in the online IMC feedback ANC system. Computer simulations and experiments in an anechoic chamber are performed to validate the method. The results indicate that this method is effective for the design of a robust controller with constrained NA.