Purpose -This paper aims to present a prototype of the diagnostic system for the examination of the distribution of the force applied by foot to substrate during usual human moving. Presented system is competitive to other currently available devices, thanks to sensors reliability, user-friendly operation manner and design based on cheap parts. The results of examinations are transmitted by radiomodem. Its recording and visualization are possible on either personal or mobile computers. Design/methodology/approach -During selection of the sensors substrate, many polymeric electrets were examined. Polyvinylidene fluoride films were selected, because they have good charge uniformity across the surface, wide range of acceptable temperatures, linear relation between mechanical stress and output signal and high resistance for squeezing. The system measures the charge generated in film. Findings -The pressures are recorded in relation to maximum value; therefore, measuring system does not require calibration. The simultaneous recording of data from all eight sensors allows tracking the signal without distortion. Originality/value -An array of sensors is installed in the shoe insole. The measuring device is fixed to the outer surface of the shoe. Its weight is 75 g. The range of transmission is suitable for examination in the natural environment, outside traditional consulting room. Software is dedicated for analysis of the pressure distribution in every moment of the foot movement. The system is suitable for examination of flat feet, diabetic foot and recovery progress after injures.
The paper presents a dynamic measurement method of the distribution of foot pressure exerted on the ground by a four-point shoe insole, developed by authors, which can be placed in any sport footwear. The value of pressure was measured on the heel, medial midfoot, metatarsal, and great toe by recording values of a generated voltage by sensors which were made of piezoelectric polymer PVDF film 110 µm thick with printed silver electrodes. As confirmed by scanning microscope studies, the foil applied in the sensors is semi-crystalline. The shoe measurement insert consists of two polyester films without piezoelectric properties between them, electroactive polymer sensors were placed. The films were glued together. To match the measuring circuit to the sensors used, two circuits were tested, a voltage measuring circuit with an input resistance of above 1012 Ω (open circuit), and a charge measuring circuit (shorted circuit). The charge measuring circuits with the RC high-pass filter, which attenuates the slow-changing pyroelectric signal was selected as it ensures the desired measurement accuracy. As presented in the paper, as PVDF sensors are very sensitive to any mechanical deformation, it is important to properly design the shoe insole to ensure its correct use during pressure distribution measurements. The measuring system developed by the authors, allows testing of foot pathology for any length of time in a dynamic way.
The paper presents an evaluation of human mobility by gait analysis, carried out in natural conditions (outside of the laboratory). Foot plantar pressure is measured using a shoe insole with 8 sensors placed in different anatomical zones of the foot, and placed inside a sports shoe. Polarized polyvinylidene fluoride (PVDF) foil is used as a sensor material. A wireless transmission system is used to transmit voltage values to the computer. Miniaturization was the priority during the design of the system. Due to the linear relationship between force and transducer voltage, energy and power released during walking in arbitrary units can be calculated as an integral of the square of the transducer voltage over time. Gait measurements were carried out over several days on healthy persons during normal walking and slow walking. The performed measurements allowed for the determination of walking speed (number of steps per second), gait rhythm and manner of walking (applying force to inside versus outside part of the sole). It was found that switching from normal to slow walk increases gait energy by 25% while the pressure distribution across the anatomical regions of the foot remains unchanged. The results will be used to develop a programme for the evaluation of patients with orthopedic diseases or even with cardiac failures, for an estimation of the results of health recovery and training efficiency in many sports activities.
Background There are many methods of dynamic analysis of foot loading, however, we still need a simple, easily applicable system for foot plantar pressure analysis. In this study we asked the question: “Can a new system for foot evaluation, the ITE System, provide a good quantitative dynamic foot pressure analysis? Can it be used in clinical practice?”. Material/Methods Twenty healthy volunteers, 8 females and 12 males, aged 20 to 25 years old took part in this study. Normal static foot loading was tested using a typical pedobarographic platform, followed by a dynamic analysis using the foot-pressure ITE System. A new algorithm for data analysis (from 8 sensors) was proposed. Results The sum of all maximal values from sensors was 11.71 N mean, with relatively low standard deviation (SD) of 1.81. Loading of sensor 1 (heel) was the highest – on average 29.84%. Sensor 2 (medial midfoot) received the lowest loading – normal range for this segment would be 0–4%. The manner of loading heel/toes, dynamics of changes in loading during gait was quite diverse; when analyzing courses of changes on sensors, 4 gait patterns were observed. Conclusions Use of the ITE System creates a new possibility for dynamic foot evaluation, drawing from pedobarography and methods of gait analysis. The proposed data analysis algorithm is simple and can be applied in all cases. Normally, 30% of the sum of all pressures during stance phase falls on the rearfoot; 39% falls on forefoot.
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