Design and Modeling of a Polymer Force Sensor

This paper presents the design, modeling, force correction strategies and experimental validation of a force sensor designed for robotized medical applications. The proposed sensor offers a new solution for force measurement in the presence of specific constraints such as medical imaging transparency, limited size, satisfactory rigidity and measurement performance. More specifically, the presented prototype has been purposely adapted to comply with the requirements of needle insertion applications, in the context of interventional radiology. A systematic viscoelastic model identification method is discussed for choosing the best time-dependent model for the force sensor. A novel compensation law is proposed based on the chosen model to correct for the viscoelastic effects of the utilized polymer material. The developed compensation law is inexpensive, stable to noise and can be applied in real-time to the sensor signal. A comparative assessment of the experimental results, obtained from quasi-static to dynamic experiments including harmonic analysis, shows the efficacy of the proposed compensation law, as compared to calibration with static gain and without compensation. The improvement in the sensor response results in decreased hysteresis levels and increased bandwidth, which are improved by more than a factor of 4.