Active control apparatus using adaptive digital filter

DETAILED DESCRIPTION It is therefore one object of the invention to achieve stable filter coefficient updating in an active control apparatus using an adaptive digital filter.
Another object of the invention is to perform noise cancellation effect to periodic sounds in an active noise control apparatus using an adaptive digital filter.
Yet another object of the invention is to make it easier to update coefficients in an active control apparatus using an adaptive digital filter.
A still further object of the invention is to increase stability in an active control apparatus using an adaptive digital filter.
The above-described objects of the invention are achieved by an active control apparatus including the following elements for controlling the physical amount of events at a desired value.
More specifically, an active control apparatus according to the invention includes a detector for detecting the amount of physical development; a control signal output unit responsive to a detection signal obtained by the detector for outputting a control signal for controlling the amount of physical development to be a desired amount; an error output unit for outputting an error between a desired amount of physical development and an actual amount of physical development.
The control signal output unit includes an adaptive digital filter formed of a non-recursive filter and a recursive filter, a first coefficient controller for updating the filter coefficient of the adaptive digital filter so as to minimize the level of an output signal from the error output unit, and a second coefficient controller for controlling the filter coefficient of the recursive filter so as to minimize the level of an output signal from the recursive filter.
The active control apparatus according to the invention includes the first coefficient controller for updating the filter coefficient so as to minimize the output level of the error output unit, and the second coefficient controller for updating the filter coefficient so as to minimize the output level of the recursive filter, and therefore divergence of a signal in the recursive filter can be suppressed