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Vibration and noise are generally considered to be the major problems in power transmission chains. This paper presents an adaptive, active control strategy for the reduction of vibration in automotive timing chain drives and examines the effects of the active control on noise reduction. Experimental results show that the average vibration amplitude is diminished by as much as 90% under low to moderate tension conditions, and the chain noise is reduced by about 3 dB. The experimental apparatus has low cost and is readily applicable to an industrial environment.

The understanding, prediction and prevention of brake squeal is a difficult and challenging problem because of the large number of design variables involved in a complex brake system and many operational and environmental conditions under which squeal may occur. The design variables may have different optimal values and different contribution trends for different brake systems. Since the 1930's, much progress has been made in gaining physical insight into brake squeal mechanisms and causes, and brakes have become quieter. However, the recurring occurrence of disc brake squeal indicates that our understanding of the phenomenon is both insufficient and incomplete, and that brake squeal is still a quality issue in the automotive industry and its prevention is far from reality. Part I of this series of articles first reviews the various hypotheses put forth for brake squeal mechanisms and causes.

Disc brake squeal is a manifestation of the friction-induced self-excited instability of the brake system. One of known techniques in suppressing dynamic instabilities in nonlinear systems is by applying dither. The focus of this paper is to examine, through numerical examples, the feasibility and effects of dither on nonlinear systems as a means of quenching large-amplitude limit cycles. In particular, various ways of introducing the dither, either via modifications of the system characteristics or as external excitation, are explored. The investigation is extended to a disc brake system using finite elements simulations. Numerical results show that large-amplitude vibrations can be suppressed by dither and careful tuning of the amplitude and frequency of the dither can result in an effective quenching. The potential application of this technique to disc brake squeal control is also discussed.