Physically Consistent Whole-Body Kinematics Assessment Based on an RGB-D Sensor. Application to Simple Rehabilitation Exercises

Jessica Colombel (1) , Vincent Bonnet (2) , David Daney (3) , Raphaël Dumas (4) , Antoine Seilles (5) , François Charpillet (1)

1 LARSEN - Lifelong Autonomy and interaction skills for Robots in a Sensing ENvironment
2 LISSI - Laboratoire Images, Signaux et Systèmes Intelligents
3 IMS - Laboratoire de l'intégration, du matériau au système
4 LBMC UMR T9406 - Laboratoire de Biomécanique et Mécanique des Chocs
5 NaturalPad [Montpellier]

This work proposes to improve the accuracy of joint angle estimates obtained from an RGB-D sensor. It is based on a constrained extended Kalman Filter that tracks inputted measured joint centers. Since the proposed approach uses a biomechanical model, it allows physically consistent constrained joint angles and constant segment lengths to be obtained. A practical method that is not sensor-specific for the optimal tuning of the extended Kalman filter covariance matrices is provided. It uses reference data obtained from a stereophotogrammetric system but it has to be tuned only once since it is task-specific only. The improvement of the optimal tuning over classical methods in setting the covariance matrices is shown with a statistical parametric mapping analysis. The proposed approach was tested with six healthy subjects who performed four rehabilitation tasks. The accuracy of joint angle estimates was assessed with a reference stereophotogrammetric system. Even if some joint angles, such as the internal/external rotations, were not well estimated, the proposed optimized algorithm reached a satisfactory average root mean square difference of 9.7 and a correlation coefficient of 0.8 for all joints. Our results show that an affordable RGB-D sensor can be used for simple in-home rehabilitation when using a constrained biomechanical model.

Mots clés: Markerless human motion analysis; Extended Kalman filter and rehabilitation

Domaines: Biomécanique [physics.med-ph]

Jessica Colombel, Vincent Bonnet, David Daney, Raphaël Dumas, Antoine Seilles, et al.. Physically Consistent Whole-Body Kinematics Assessment Based on an RGB-D Sensor. Application to Simple Rehabilitation Exercises. Sensors, 2020, 20 (10), 18p. ⟨10.3390/s20102848⟩. ⟨hal-02639281⟩