Evaluating and Modeling Force Sensing Resistors for Low Force Applications

Abstract

There has been an increasing demand for force measurement in applications that are portable, wearable, have limited space, low power, or low cost requirements. Such applications cannot support the power and computing requirements of the load cells. Force sensing resistor (FSR) is a passive component that is composed of polymer thick films that change resistance between its terminals due to force applied at its surface. An FSR can provide a suitable alternative to the bulky load cell. However, it inherently exhibits many nonlinear behaviors. This paper evaluates five different FSR sensors (IEE FSR 151 NS, Interlink FSR 402, Sensitronics ShuntMode FSR. FlexiForce A201 FSR, and Sensitorincs ThruMode FSR). The FSRs were evaluated for sensitivity, minimum measurable force, repeatability, creep, and hysteresis. In addition, system identification techniques were used to model each FSR behavior so they can be used as calibrated standalone force sensors. Results show that the Sensitronics ThruMode FSR had the best repeatability and the least hysteresis, while the FlexiForce A201 had the lowest creep, and the Interlinks 402 FSR had the lowest threshold force.

Hybrid genetic algorithm-system identification approach to model force sensing resistors

“…For this work, five commercially available FSRs of the same circular shape and comparable sizes have been selected (Figure 2). The author along with his team compared the performance of the five FSRs in an earlier work (Saadeh et al, 2017). The evaluation considered several tests including: sensitivity, threshold, repeatability, creep, and hysteresis analysis.…”

“…However, the user should enter at minimum the suggested input nonlinearity (if any), its parameters, the order of the linear model (its zeroes and poles) and the output nonlinearity with its parameters (if any). A similar work using system identification with user selected parameters was introduced earlier (Saadeh et al, 2017). This limitation narrows down the search space to only the suggested structure provided by the user.…”

“…The regional linear behavior of the FSR appears in the middle of the loading cycle but it can not explain the entire cyclic behavior. Saadeh et al (2017) showed that FSRs exhibit many nonlinear behaviors, such as: hysteresis, backlash, and creep.…”

“…Sadun et al (2016) compared the FlexiForce A201 to Interlink FSR 406 and found that both sensors were reliable for open and closed loop applications. Also, Saadeh et al (2017) evaluated five different FSRs (IEE FSR 151 NS, Interlink FSR 402, Sensitronics ShuntMode FSR, FlexiForce A201 FSR, and Sensitorincs ThruMode FSR) for sensitivity, minimum threshold, repeatability, creep, and hysteresis. They found that the Sensitronics ThruMode FSR had the best repeatability and the least hysteresis, while the FlexiForce A201 had the lowest creep, and the Interlinks 402 FSR had the lowest threshold force.…”

Comparison of Performances of Flexible Tailor-Made Force Sensing Resistors Fabricated Using Inkjet and Xurographic Techniques

“…402 (Interlink Electronics) was enclosed with steel plates and dental protection to create device for measurement of bite forces produced with posterior teeth [20]. Several studies [21][22][23][24][25] compared characteristics of commercial force sensing resistors (usually from Interlink, FlexiForce and LuSense), but there is a lack of publications which reports performances of custom-made force sensing resistors with properties comparable or better with commercial ones. This work describes a design of tailor-made force sensing resistors intended to be used in dental medicine (dimensions are adapted for application in oral cavity on the teeth surfaces).…”