A portable plantar pressure system: Specifications, design, and preliminary results

Abstract

BACKGROUND: In recent years, there has been an increasing interest in developing in-shoe foot plantar pressure systems. Although such devices are not novel, devising insole devices for gait analysis is still an important issue. OBJECTIVE: The goal of this study is to develop a new portable system for plantar pressure distribution measurement based on a three-axis accelerometer. METHODS: The portable system includes: PJRC Teensy 3.6 microcontroller with 32-bit ARM Cortex-M4 microprocessor with a clock speed of 180 MHz; HC-11 radio modules (transmitter and receiver); a battery; a fixing band; pressure sensors; MPU-9150 inertial navigation module; and FFC tape. The pressure insole is leather-based and consists of seven layers. It is divided into 16 areas and the outcome of the system is data concerning plantar pressure distribution under foot during gait. The system was tested on 22 healthy volunteer subjects, and the data was compared with a commercially available system: Medilogic. RESULT: The SNR value for the proposed sensor is 28.27 dB. For a range of pressure of 30–100 N, the sensitivity is 0.0066 V/N while the linearity error is 0.05. The difference in plantar pressure from both the portable plantar pressure system and Medilogic is not statistically significant. CONCLUSION: The proposed system could be recommended for research applications both inside and outside of a typical gait laboratory.