Abstract
Recent advances in wearable sensor technologies for motion capture have produced devices, mainly based on magneto and inertial measurement units (M-IMU), that are now suitable for out-of-the-lab use with children. In fact, the reduced size, weight and the wireless connectivity meet the requirement of minimum obtrusivity and give scientists the possibility to analyze children's motion in daily life contexts. Typical use of magneto and inertial measurement units (M-IMU) motion capture systems is based on attaching a sensing unit to each body segment of interest. The correct use of this setup requires a specific calibration methodology that allows mapping measurements from the sensors' frames of reference into useful kinematic information in the human limbs' frames of reference. The present work addresses this specific issue, presenting a calibration protocol to capture the kinematics of the upper limbs and thorax in typically developing (TD) children. The proposed method allows the construction, on each body segment, of a meaningful system of coordinates that are representative of real physiological motions and that are referred to as functional frames (FFs). We will also present a novel cost function for the Levenberg–Marquardt algorithm, to retrieve the rotation matrices between each sensor frame (SF) and the corresponding FF. Reported results on a group of 40 children suggest that the method is repeatable and reliable, opening the way to the extensive use of this technology for out-of-the-lab motion capture in children.
Highlights
The possibility of capturing and quantitatively measuring children’s motion repertoire in a daily life scenario is of great interest for a number of reasons
Without loss of generality, we describe the method for the case of the thorax segment (RFSFF T horax ), where exactly 3 axis estimates are available from the protocol and will provide a means to generalize the method to the other body segments
This paper describes a novel calibration protocol for the kinematic tracking of the thorax and upper limbs with magneto and inertial measurement units (M-IMU) wearable sensors, designed to be used with children
Summary
The possibility of capturing and quantitatively measuring children’s motion repertoire in a daily life scenario is of great interest for a number of reasons. Examples of widely used test to measure motor skills in children are the Gross Motor. The lack of reliable, objective measurements foster interest in the development of tools to accurately capture information about children’s motion skills in real-life environments. It would be of key importance in the rehabilitation of children with a chronic health condition, such as cerebral palsy, to guide and evaluate interventions, to monitor progress and to provide families with objective feedback [4]. Quantitative motion evaluation can support standard clinical rating scales, providing clinicians with enriched information on patients’ health [5]
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