Development of an in-shoe pressure-sensitive device for gait analysis

The BioRobotics Institute, Scuola Superiore Sant’Anna, viale Rinaldo Piaggio 34, 56025 Pontedera, Pi, Italy.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:5637-40. DOI: 10.1109/IEMBS.2011.6091364
Source: PubMed


In this work, we present the development of an in-shoe device to monitor plantar pressure distribution for gait analysis. The device consists in a matrix of 64 sensitive elements, integrated with in-shoe electronics and battery which provide an high-frequency data acquisition, wireless transmission and an average autonomy of 7 hours in continuous working mode. The device is presented along with its experimental characterization and a preliminary validation on a healthy subject.

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    • "Both types of configurations have been reported in literature based on capacitive, piezoresistive elements, micro-electromechanical systems (MEMS) and opto-electronic sensors [23] [24] [25] [26]. However, most of the applications have drawbacks such as limited pressure monitoring range [26] and susceptibility to electromagnetic interference (EMI), which may not only reduce the signal to noise ratio (SNR), demand additional post measurement data processing or may lead to inaccurate pressure measurement. Although modern MEMS based sensors offer compact wireless monitoring, however, they are prone to EMI and the power consumption level is much/ higher than the available industry standard. "
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    ABSTRACT: Clinical monitoring of planar pressure is vital in several pathological conditions, such as diabetes, where excess pressure might have serious repercussions on health of the patient, even to the extent of amputation. The main objective of this paper is to experimentally evaluate the combined application of the Fibre Bragg Grating (FBG) and the lead zirconate titanate (PZT) piezoceramic sensors for plantar pressure monitoring during walk at low and high speeds. For fabrication of the pressure sensors, the FBGs are embedded within layers of carbon composite material and stacked in an arc shape. From this embedding technique, average pressure sensitivity of 1.3 pm/kPa and resolution of nearly 0.8 kPa is obtained. These sensors are found to be suitable for measuring the static and the low-speed walk generated foot pressure. Simultaneously, PZT patches of size 10×10×0.3 mm were used as sensors, utilizing the d33 (thickness) coupling mode. A sensitivity of 7.06 mV/kPa and a pressure resolution of 0.14 kPa is obtained from these sensors, which are found to be suitable for foot pressure measurement during high speed walking and running. Both types of sensors are attached to the underside of the sole of commercially available shoes. In the experiments, a healthy male subject walks/ runs over the treadmill wearing the fabricated shoes at various speeds and the peak pressure is measured using both the sensors. Commercially available low-cost hardware is used for interrogation of the two sensor types. The test results clearly show the feasibility of the FBG and the PZT sensors for measurement of plantar pressure. The PZT sensors are more accurate for measurement of pressure during walking at high speeds. The FBG sensors, on the other hand, are found to be suitable for static and quasi-dynamic (slow walking) conditions. . Typically, the measured pressure varied from 400 to 600 kPa below the forefoot and 100 to 1000 kPa at the heel as the walking speed varid from 1 kilometer per hour (kmph) to 7 kmph.When instrumented in combination, the two sensors can enable measurements ranging from static to high speed conditions Both the sensor types are rugged, small sized and can be easily embedded in commercial shoes and enable plantar pressure measurement in a cost-effective manner. This research is expected to have application in the treatment of patients suffering from diabetes and gonarthrosis.
    Full-text · Article · Sep 2014 · Technology and health care: official journal of the European Society for Engineering and Medicine
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    • "The technology was developed in-house and first used in pressure-sensitive cuffs [22], then adapted for insoles. This specific design has been validated [23] [24] and requires no user-specific calibration. "
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    ABSTRACT: This paper presents algorithms for detection of gait initiation and termination using wearable inertial measurement units and pressure-sensitive insoles. Body joint angles, joint angular velocities, ground reaction force and center of plantar pressure of each foot are obtained from these sensors and input into supervised machine learning algorithms. The proposed initiation detection method recognizes two events: gait onset (an anticipatory movement preceding foot lifting) and toe-off. The termination detection algorithm segments gait into steps, measures the signals over a buffer at the beginning of each step, and determines whether this measurement belongs to the final step. The approach is validated with 10 subjects at two gait speeds, using within-subject and subject-independent cross-validation. Results show that gait initiation can be detected timely and accurately, with few errors in the case of within-subject cross-validation and overall good performance in subject-independent cross-validation. Gait termination can be predicted in over 80% of trials well before the subject comes to a complete stop. Results also show that the two sensor types are equivalent in predicting gait initiation while inertial measurement units are generally superior in predicting gait termination. Potential use of the algorithms is foreseen primarily with assistive devices such as prostheses and exoskeletons.
    Full-text · Article · Aug 2013 · Medical Engineering & Physics
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    • "De Rossi et al. [58] employed 64 silicone-covered opto-electronic pressure sensors array, four 16-channel 14-bit analog-to-digital converters, a microcontroller and a Bluetooth module. The sensors have 12 mm × 12 mm × 5.5 mm dimension, maximum loading of 500 kPa without damaging the sensor. "
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    ABSTRACT: Foot plantar pressure is the pressure field that acts between the foot and the support surface during everyday locomotor activities. Information derived from such pressure measures is important in gait and posture research for diagnosing lower limb problems, footwear design, sport biomechanics, injury prevention and other applications. This paper reviews foot plantar sensors characteristics as reported in the literature in addition to foot plantar pressure measurement systems applied to a variety of research problems. Strengths and limitations of current systems are discussed and a wireless foot plantar pressure system is proposed suitable for measuring high pressure distributions under the foot with high accuracy and reliability. The novel system is based on highly linear pressure sensors with no hysteresis.
    Full-text · Article · Dec 2012 · Sensors
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