Wearable sensor systems in biomechanics: assessment of unrestrained walking features

A wearable sensor system is proposed to determine several walking features. including stride length, cadence, walking speed, incline. The sensor system is composed of an inertial measurement unit (IMU) mounted on the foot instep and a biaxial accelerometer mounted on the waist. The IMU integrates a biaxial accelerometer and a rate gyroscope. Both the foot gyroscope and the waist accelerometer are capable to accurately estimate the cadence. Strapdown integration applied to the inertial data allows to reconstruct the trajectory in the sagittal plane of the sensed anatomical point on the foot, yielding the opportunity to determine the desired walking features. Double-integration of the waist accelerometer signals to determine the trunk vertical displacement and root mean square analysis of the waist acceleration modulus allow to construct two predictors of the walking speed, which integrate the information gathered from the inertial estimator. In this paper, preliminary results concerning the accuracy of level walking speed prediction by different methods are presented.