Effect of load on active friction control using ultrasonic vibrations

The ability to control the effective friction coefficient between sliding surfaces is of particular fundamental and technological interest for automotive applications. It has been shown that the friction force between sliding surfaces can be reduced by superimposing ultrasonic vibrations on the macroscopic sliding velocity. We developed a systematic approach based on experiments and models to describe and characterize the friction force between sliding surfaces in the presence of ultrasonic vibrations generated by a piezoelectric transducer. The controlling parameters in this study are static contact pressure, relative velocity, voltage, and frequency. Using a low power PMN-PT driver, we experimentally demonstrate a decrease of up to 68 % in effective friction coefficient and analytically show the underlying principle behind the friction reduction. The trends show a decrease in the effect with increasing sliding velocity and normal load. The results underscore the role of ultrasonic power in harnessing the friction control concept in applications.