Characterization of Bespoke Force Sensors for Tailored Applications

Abstract

Bespoke force sensors made with active polymer composites are inexpensive, thin and flexible, hence popular in wearable electronics, however their wider application is limited due to the lack of literature studying their voltage response related errors. We present the voltage response characterization of bespoke force sensors made with an active polymer composite, silver coated fabric, stainless steel thread, and silver epoxy. Characterization of the effects of static and dynamic loading was completed with a mechanical testing machine. Static tests consisted of loading and unloading at 0.01, 0.1, 0.5 and 1 N/s, and drift tests for 120 minutes up to 10 N every 1 N. Dynamic tests consisted of a sinusoidal load of 5 N ±1 N applied at 0.05, 0.1, and 0.5 Hz for 60 min. The force-voltage relationships were modeled using an exponential function. Maximum mean drift error was observed when applying different static loads for 120 minutes each. Drift error is minimal at 5 s (<1%) and at 60 min (<5%) with loads under 1 N. Maximum hysteresis of 18% was observed at the 1 N/s loading rate. The maximum drift error after 1 h of dynamic loading was observed at 0.5 Hz and is minimal (−0.00004%). The cost of fabricating these sensors is very low compared with commercially available options. These sensors can be fabricated in any shape and size with the added advantage of being able to set the location of the electronic connections as desired.

Creep and Hysteresis Compensation in Pressure-Sensitive Mats for Improving Center-of-Pressure Measurements

“…First of all, the hysteresis and creep of a pressure sensor based on Velostat has been modeled. Although there have been several studies that have measured properties of Velostat based tactile sensors like sensitivity, hysteresis, response time, creep, or repeatability (see [11], [14], [28]- [30] or [31] and references therein) they just characterize these phenomena with simple parameters extracted from the sensor response. On the other hand, the current work uses a theory with a strong formal background to develop the model and opens the possibility of compensation by inverting it.…”