A Method of estimating environmental friction based on a body dynamics model of

線虫の身体動力学モデルに基づく環境摩擦の推定法

曽 智*; 正岡 和弥*; 鈴木 芳代; 服部 佑哉; 辻 敏夫*

Soh, Zu*; Masaoka, Kazuya*; Suzuki, Michiyo; Hattori, Yuya; Tsuji, Toshio*

Information on the forces generated by the is important in exploring the mechanism of its locomotion. The present study was performed to investigate a method for estimating environmental friction based on the use of a dynamics model and image analysis. The model is described using Newton-Euler equations of rigid links serially coupled by rotational joints. The friction forces acting between the environment and the body are modeled using dynamic and viscous friction. Although the motion equation can be solved for friction coefficients as a function of the worm's motion, this straightforward solution is an ill-posed problem because the friction model contains four unknown coefficients, while a worm crawling on an x-y plane has only two degrees of freedom. To solve this problem, the proposed method involves simultaneous analysis of two different worm motions in the same environment for which identical friction coefficients are assumed. In addition, as the images used in analysis to determine a worm's motion inevitably contain noise, a coefficient-optimization approach was adopted to minimize the error between trajectories of an actual worm and the corresponding dynamics model in terms of the four friction coefficients. The proposed method was applied to estimate the preset coefficients. The results indicated that the percentage error between the preset and estimated coefficients was within 4%.