Design and Validation of a Low-Cost Portable Device to Quantify Postural Stability

Abstract

Measurement of the displacement of the center-of-pressure (COP) is an important tool used in biomechanics to assess postural stability and human balance. The goal of this research was to design and validate a low-cost portable device that can offer a quick indication of the state of postural stability and human balance related conditions. Approximate entropy (ApEn) values reflecting the amount of irregularity hiding in COP oscillations were used to calculate the index. The prototype adopted a portable design using the measurements of the load cells located at the four corners of a low-cost force platform. The test subject was asked to stand on the device in a quiet, normal, upright stance for 30 s with eyes open and subsequently for 30 s with eyes closed. Based on the COP displacement signals, the ApEn values were calculated. The results indicated that the prototype device was capable of capturing the increase in regularity of postural control in the visual-deprivation conditions. It was also able to decipher the subtle postural control differences along anterior–posterior and medial–lateral directions. The data analysis demonstrated that the prototype would enable the quantification of postural stability and thus provide a low-cost portable device to assess many conditions related to postural stability and human balance such as aging and pathologies.

Activity Level Assessment Using a Smart Cushion for People with a Sedentary Lifestyle

“…The displacement of the Center of Pressure (CoP) can assess postural stability in the field of biomechanics [ 32 ]. The CoP is defined as the point location of the vertical seat reaction force vector.…”

“…Equipped with intelligent data analytics, their system can classify 19 kinds of complex user sedentary activities and it can also detect user functional activities and emotion based activities. Similarly to the smart cushion, Zhu [ 32 ] designed a low-cost device using Arduino and pressure sensor unit to quantify postural stability. Approximate entropy features of Center-of-Pressure (CoP) were used to reflect the irregularity of oscillations.…”

A Novel Trunk Rehabilitation Robot Based Evaluation of Seated Balance Under Varying Seat Surface and Visual Conditions

“…The COP is calculated using the forces gauged by four compression load cells placed one at each corner of the seat and interfaced with the PC, where a software running in the LabVIEW development environment (LabVIEW 2015, National Instruments) calculates the position of the user's COP referred to the center of the seat surface. The COP position is calculated using equations (1) and 2where, , , and are the forces measured by the four load cells, and L and W are the length (along X-axis) and width (along Y-axis) of the seat surface, respectively [29]. The value is the COP position in the ML direction and the value is the COP position in the AP direction.…”

System for Evaluation and Compensation of Leg Length Discrepancy for Human Body Balancing

“…The master device consists of an ATmega2560 microcontroller, eight analog-to-digital (ADC) HX711 converters, eight force sensors and a power unit. The force sensors are calibrated with etalon weights weighing 100 g, 200 g, 500 g and 1000 g prior to use [33]. The master device sends the slave devices a reference position of the linear actuators and at the same time communicates to the PC the current positions of the linear actuators and force sensor measurements.…”