Sensor fusion applied to position estimation and gait identification of an ankle-foot orthosis

Abstract

This paper presents a sensor fusion strategy to estimate the absolute position and to identify the gait events of an active ankle-foot orthosis (AAFO). Sensor fusion is implemented using a Kalman filter with the signals of a gyroscope and an accelerometer, both present in an inertial measurement unit (IMU), besides the signals of three force sensitive resistors (FSRs) mounted in a sole of shoe. For correcting the gyroscopebased position, the redundant accelerometer-based position must be used only under reliable conditions, which are obtained by a proposed switching logic to enable the Kalman filter. Experimental results of the AAFO confirm the efficiency of the proposed sensor fusion strategy.

Fuzzy logic control for active ankle foot orthosis

“…However their output is affected by gravity and is known to vary with sensor location as well as axis of rotation. Hence gyroscopes are better suited to monitor gait patterns of the ankle foot joint [23][24][25]. The gyroscope LPY530AL IC includes a phase locked loop (PLL) circuit to synchronize driving and sensing interfaces.…”

“…where Omega is angular velocity of the foot, V out is output voltage of the gyroscope sensor, V ref is output voltage of gyroscope at standstill position [23][24][25]. Sensitivity is the smallest value of angular velocity which can be detected using gyroscope.…”

“…This is obtained by continuously integrating the angular velocity values with respect to time from zero to current time 't' [25]. The values of both angular velocity and angular displacement are plotted with respect to time.…”

Quantitative assessment of dual gait analysis based on inertial sensors with body sensor network

“…Dietz et al (2001) applied gyroscope and force sensor to get the gait cycle. Caltran and Siqueira (2011) used the IMU to study the motion information by fusing the sensor data. Sabatini et al (2005) used one IMU sensor bounded on the right instep to obtain the acceleration and angular velocity during walking.…”