Dynamic calibration of tactile sensors for measurement of soil pressures in centrifuge

Tactile pressure sensors are flexible, thin sheets containing a matrix of sensors, which are used to measure earth pressures in geotechnical applications. Although more successful in static and 1-g shaking table tests, available tactile sensors do not capture the full amplitude content of dynamic signals in centrifuge experiments. This is due to under-sampling and the sensor's frequency-dependent response. A minimum sampling rate of 3000 samples per second is recommended in centrifuge testing to avoid under-sampling and capture frequencies up to 300 Hz in model scale. A new dynamic calibration methodology is proposed to characterize the sensor's frequency-dependent response by evaluating how it attenuates pressure at higher frequencies. Sinusoidal loads are applied to the sensor at different frequencies, and the applied pressure is simultaneously recorded by a reference load cell and a tactile sensor. A transfer function is then calculated by dividing the Fourier pressure amplitude of the load cell by that of the tactile sensor at a given frequency. To dynamically calibrate tactile sensors, this transfer function may be used as an amplitude correction function under general loading. Through a series of blind dynamic tests, the proposed frequency-dependent, dynamic calibration methodology is shown to reduce the peak residuals between the tactile and reference sensor recordings from approximately 0.55 to 0.15 at frequencies below 300 Hz.