Identifying Stick-Slip Characteristics of a Smart Device on a Seismically Excited Surface Using On-Board Sensors

Accelerometers in smart devices have been used to successfully detect the occurrence of seismic activity. Taking the next step of using the measured acceleration response to compute floor displacements for the purpose of assessing building seismic damage is a more challenging application. In particular, sliding of smart devices or their underlying support hinders their use for this purpose because that means that the floor drifts cannot be directly measured using the onboard sensors. This paper discusses the dynamic behavior of a free-standing smart device and presents a method for estimating the kinetic coefficient of friction between the smart device and the underlying surface based on wavelet transforms. A methodology is then presented by which a smart device can decide if its motion is representative of the motion of the floor underneath or whether it is tainted by excessive sliding action. The noise associated with a smart device’s measurement of acceleration is established and noise reduction methods to overcome them are compared. Computational simulation results and experimental data are used to demonstrate the concepts discussed in this paper.