3D posture estimation of upper limb considering clavicle using inertial sensor

Abstract

In this study, we proposed an advanced motion analysis method of the upper limbs including clavicle using inertial sensor. To estimate the posture of the upper limbs, inertial sensor system which is composed of a tri-axial accelerometer, a tri-axial gyroscope and a tri-axial geomagnetic sensor is developed. Two inertial sensors are attached to the right and left clavicle to observe the motion between sternoclavicular joint and acromioclavicular joint, and totally seven sensors are used to estimate the posture of upper limbs. The posture of each body part is obtained by applying extended Kalman filter during the slow motion and by integration of angular velocity during rapid movement. Ten subjects performed four types of upper arm motion in which position of shoulder joint changes (1) shoulder up and down, (2) shoulder forward and backward, (3) abduction of the upper limbs 90 deg. and (4) abduction of the upper limbs 180 deg. The position of the shoulder, elbow and wrist obtained from the inertial sensor was compared with reference obtained by optical motion capture system. The result demonstrated that proposed method could be used to measure the motion between sternoclavicular joint and acromioclavicular joint. Also, the error significantly decreased in both side shoulder joint during all motion. Therefore, the proposed method can observe the clavicle motion and provides high precision motion analysis of upper limbs.

Keywords

• inertial sensor
• upper limb
• clavicle
• wearable
• motion measurement