Dynamics-switching optimal control model for human sitting movements on chair

We have formulated a three-link and three-joint optimal control model that reproduces human sitting movements on a chair. The model switches its dynamics at the moment (switching time) when its body sits down on the chair, and optimizes its criterion function composed of three kinds of energy costs, a center-of-gravity cost, and an input cost. We clarify its reproducible performance in sitting on a chair and discuss factors indispensable for reproducing the same sitting movements on a chair as humans. Consequently, the following results were obtained: (1) the proposed model successfully reproduced experimentally measured sitting movements on the chair by appropriately adjusting the switching time; (2) there existed the optimum switching time for each sitting condition. These results suggest that the proposed model is effective as a model of the human sitting mechanism on a chair and that the switching time can be a factor involved strongly in human sitting movements on a chair.