The effect of biomechanical variables on force sensitive resistor error: Implications for calibration and improved accuracy

Abstract

Force Sensitive Resistors (FSRs) are commercially available thin film polymer sensors commonly employed in a multitude of biomechanical measurement environments. Reasons for such wide spread usage lie in the versatility, small profile, and low cost of these sensors. Yet FSRs have limitations. It is commonly accepted that temperature, curvature and biological tissue compliance may impact sensor conductance and resulting force readings. The effect of these variables and degree to which they interact has yet to be comprehensively investigated and quantified. This work systematically assesses varying levels of temperature, sensor curvature and surface compliance using a full factorial design-of-experiments approach. Three models of Interlink FSRs were evaluated. Calibration equations under 12 unique combinations of temperature, curvature and compliance were determined for each sensor. Root mean squared error, mean absolute error, and maximum error were quantified as measures of the impact these thermo/mechanical factors have on sensor performance. It was found that all three variables have the potential to affect FSR calibration curves. The FSR model and corresponding sensor geometry are sensitive to these three mechanical factors at varying levels. Experimental results suggest that reducing sensor error requires calibration of each sensor in an environment as close to its intended use as possible and if multiple FSRs are used in a system, they must be calibrated independently.

Experimental characterization, modeling and compensation of hysteresis in force sensing resistors

“…The performance of the CMA to estimate F was comparatively evaluated with the linear regression model (1), which is the manufacturer recommended method. It must be noted that the linear regression model is the preferred method in research applications [4,5,[9][10][11][12][13]. Two sets of m and b constants were calculated using the triangle force profiles of Section III.B.…”

“…The reduction in the force MSE is paid by a larger computation time, which may limit the usability of the CMA in some real-time applications, but if time is not a constraint; the CMA can run off-line and get the best of a FSR. This is the case of most biomechanics researches in which data are collected and later analyzed [4,5]. However, a fast implementation of the CMA is possible if dedicated hardware is used, i.e., employing FPGA technology [22].…”

“…Force Sensing Resistors (FSRs) are cost-affordable force sensors that can be easily integrated into multiple Biomechanical applications [4][5][6]. Nonetheless, the main reasons for its widespread usage are their low profile and low weight, which are highly desirable characteristics when attempting to perform non-invasive force measurements [6].…”

“…Relevant works on this scope have been developed by Lebosse [9], Schofield [5], Dabling [12], Vecchi [13] and Urban [14]. Likewise, authors' previous work has demonstrated that the A201 sensors, working on the piezoresistive principle, are also capable of exhibiting a piezocapacitive response.…”

Wearable Resistive-based Gesture-Sensing Interface Bracelet

“…The FSR were selected in this system due to its light weight, small size, high sensing accuracy, ultra-thin material and low power consumption [14]. The FSR chosen in this system, a two-wire resistance, is medium round (13 mm diameter) [15]. This pressure sensor converts the pressure applied in the thin film area of the FSR sensor into the change of resistance value which obtains pressure information.…”