A Velostat-Based Pressure-Sensitive Mat for Center-of-Pressure Measurements: A Preliminary Study

Abstract

Center-of-pressure (CoP) displacements play a key role in studies assessing postural stability. The accepted instrument to measure CoP trajectories is the force platform, but pressure-sensitive mats (PSMs) are an alternative composed of a matrix of sensitive cells. A typical cell comprises two electrodes with piezoresistive material in between, while a force platform has a force sensor at each of its corners. In this paper, we compare a homemade Velostat-based PSM and an affordable commercial mat with a commercial force platform in a test series with 42 healthy volunteers in single-legged trials (29 males, 13 females; height 1.74 (0.09) m, weight 74.3 (16.34) kg, age 31.21 (12.66) years). The aim of the research was to perform a preliminary study of the performance of our prototype to measure CoP, and more specifically, the standard deviation of the CoP path on both axes, the medial–lateral and anterior–posterior. We could thus discover several improvements for future clinical applications. The intraclass correlation coefficient (ICC) for agreement in the base experiment showed a moderate value for the prototype (0.38 to 0.63) and lower values for the commercial mat (0.11 to 0.12). However, we identified several factors that were relevant to improve ICC and reduce error by considering several processing options: (i) the known crosstalk problem between cells that appears in this kind of mats must be eliminated; (ii) the response time of the sensor has to be taken into account; and (iii) increasing the mat resolution also improves agreement. Therefore, as future work, we plan to test the improved version of the prototype in a clinical environment.

Enhanced Noise-Resilient Pressure Mat System Based on Hyperdimensional Computing

“…Since we have all the 32 lines sharing with the load resistors, it is important to separate the high-voltage releases between them. The decisions are made based on common practice reported in the literature [30,34].…”

Intelligent Medical Velostat Pressure Sensor Mat Based on Artificial Neural Network and Arduino Embedded System

“…In medical diagnosis and sports applications, the body posture control associated with the analysis and measurement of plantar pressure distribution reveals the pressure interface between the plantar surface of the foot and the sole of the shoe. Neonatal constant monitoring, sports training monitoring, and elderly care are applications of the Velostat-based pressure sensitive mat (PSM) [11][12][13]. The plantar pressure distribution allows for the analysis of the rhythm and size of the step, weight distribution between heel and foot, and timing of the gait phases by means of Velostatbased foot sensors installed in the shoe lining [14].…”

“…Studies on standing posture and stability use, as a quantitative measure, the displacement of the center of pressure (CoP) calculated through a force platform in aged or diabetic subjects, children with cerebral palsy, or subjects in the neonatal stage. Pressure-sensitive mats (PSMs) are generally adopted to measure pressure on seats, beds, or floors, for interactive multimedia systems, for interactive toys, and for measuring CoP and train sitting balance [11,19]. Elderly or long-term hospitalized patients with diseases have a significant risk of pressure sores, which are wounds of the skin and internal tissues caused by continuous pressure on a specific area of the body.…”

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

“…PSMs are one of them, outstanding for is low weight, flexibility, ease of transportation and cost in some cases. Several studies [6]- [10] have compared both systems by extracting some parameters of the CoP trajectory that have shown from moderate to strong correlation. The differences are not surprising given that the principle of operation is completely different.…”

“…Thus, an equilibration step is often recommended [17]. In [10] it was shown that removing crosstalk, improving resolution and a simple modeling of sensor time response could improve agreement between the instruments. In [6] the agreement between both instruments was improved by considering a filter in the frequency domain that relates their CoP displacements.…”