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Development and Evaluation of a Hybrid Measurement System to Determine the Kinematics of the Wrist

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Optical Motion Capture Systems (OMCS) are considered the gold standard for kinematic measurement of human movements. However, in situations such as measuring hand kinematics during a hairdressing activity, markers can be obscured, resulting in a loss of data. Other measurement methods based on non-optical data can be considered, such as magneto-inertial measurement units (MIMUs). Their accuracy is generally lower than that of an OMCS. In this context, it may be worth considering a hybrid system [MIMU + OMCS] to take advantage of OMCS accuracy while limiting occultation problems. The aim of this work was (1) to propose a methodology for coupling a low cost MIMU (BNO055) to an OMCS in order to evaluate wrist kinematics, and then (2) to evaluate the accuracy of this hybrid system [MIMU + OMCS] during a simple hairdressing gesture. During hair-cutting gestures, the root-mean-square error compared with OMCS was 4.53 (1.45 ) for flexion/extension, 5.07 (1.30 ) for adduction/abduction and 3.65 (1.19 ) for pronation/supination. During combing gestures, they were significantly higher, but remained below 10 . In conclusion, this system allows for maintaining wrist kinematics in case of the loss of hand markers while preserving an acceptable level of precision (<10 ) for ergonomic measurement or entertainment purposes.