Using Distributed Wearable Sensors to Measure and Evaluate Human Lower Limb Motions

Abstract

Abstract-This paper presents a wearable sensor approach to motion measurements of human lower limbs, in which subjects perform specified walking trials at self-administered speeds so that their level walking and stair ascent capacity can be effectively evaluated. After an initial sensor alignment with the reduced error, quaternion is used to represent 3-D orientation and an optimized gradient descent algorithm is deployed to calculate the quaternion derivative. Sensors on the shank offer additional information to accurately determine the instances of both swing and stance phases. The Denavit-Hartenberg convention is used to set up the kinematic chains when the foot stays stationary on the ground, producing state constraints to minimize the estimation error of knee position. The reliability of this system, from the measurement point of view, has been validated by means of the results obtained from a commercial motion tracking system, namely, Vicon, on healthy subjects. The step size error and the position estimation accuracy change are studied. The experimental results demonstrated that the extensively existed sensor misplacement and sensor drift problems can be well solved. The proposed self-contained and environment-independent system is capable of providing consistent tracking of human lower limbs without significant drift.

Accurate Estimation of Gait Altitude Using One Wearable IMU Sensor

“…Considering the above sensor data characteristics and to reduce the drifts of acceleration, several data fusion algorithms were presented, such as Kalman filters [19] [18], complementary filters [23], and particle filters [24]. In this work, we used a CF algorithm that fuses the acceleration and angular velocity data to correct acceleration in the swing phase, as shown in Fig.5.…”

“…On the vertical direction, multi-sensor-based methods were developed to reduce the error of the estimated altitude. For example, the Denavit-Hartenberg (DH) method was built based on three sensor nodes worn on one lower limb [18]. But in most occasions, people prefer wearing fewer sensors on their body.…”

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“…We assumed that these experimental settings were practical for use by general agricultural workers, directors, and managers to obtain time-series of visual data for diverse analyses of outdoor experiments with reference to past studies [5], [10], [12], [14], [15].…”

Inertial/magnetic sensors based pedestrian dead reckoning by means of multi-sensor fusion

“…It is convenient to incorporated ZVU into the PDR 250 system by formulating it as pseudomeasurements of zero velocity. ZVU must only be implemented when the foot is completely at the stance phase [25] [26].…”