Dynamic Evaluation of a Nanocomposite Force Sensor

This paper describes the dynamic characteristics of a newly-designed force sensor comprised of carbon nanoparticles embedded in a polyphenylene sulfide matrix and operating on the principle of contact resistance change with pressure. Sensor performance was investigated for frequencies ranging from 1 to 1,000 Hz using two testing setups: a load frame for low frequency characterization and a piezo-electric stack for describing higher-frequency behavior. Bode magnitude and phase response plots were developed and it was determined that the sensor under study can be modeled as a first order system up to 600 Hz. The −3 dB bandwidth was found to be 90 Hz and the sensor’s time constant was determined to be 0.0018 seconds. A dynamic model of the sensor is constructed and compared against performance data. The sensor was found to have non-linear spring properties, allowing for two damping coefficients, one for each spring constant range, to be calculated. The damping coefficient was calculated to be 619 lb-s/in for loadings under 600 lbs and 1928 lb-s/in for loadings greater than 600 lbs. The sensor’s time response was also found to be more similar in shape to the input loading waveform when it was compared to piezoelectric load transducers.