int . , . noil . 1989 December 4 - 6 89 ADAPTIVE VIBRATION CONTROL USING AN LMS - BASED CONTROL ALGORITHM

The fundamental principles governing the reduction of energy in an acoustic or vibration field have been understood for decades. In recent years, the concept of active control has been investigated as a means of controlling the acoustic or vibration field [1-3]. To implement active control, a number of "secondary" sources are introduced into the system which interact with the original "primary" source in such a way as to achieve the desired control, Active control has been found to be most effective for low frequency attenuation. Thus, it is often desirable to use active control in combination with passive techniques since effective high frequency attenuation is possible using conventional passive control. Recent advances in high-speed digital signal processors have made adaptive implementations of active control attractive. In a number of applications, the frequency or spatial distribution of the primary field may change with time. In addition, the parameters of the system to be controlled may also change with time. Adaptive systems have the ability to track such changes and provide optimal control over a much broader range of conditions than conventional fixed control systems. This paper will discuss a control system based on the least-mean-squares (LMS) algorithm which has been developed for active control applications. The control algorithm is applicable for time varying systems, including systems whose response to the secondary source input varies with time. Thus, the algorithm must simultaneously perform system identification and control. Both of these processes are achieved adaptively, which results in a control system which is fully adaptive and requires no apriori measurements or training.