Abstract
We have already formulated a human three-joint arm's optimal control model with a freezing-like mechanism in its hand joint and clarified the model's effectiveness in reproducing two-point reaching movement characteristics. An obstacle-avoiding movement is not only a kind of two-point reaching movements but also one of fundamental arm movements. However, there has been formulated no mathematical model for reproducing obstacle-avoiding movement characteristics. This research formulates a new optimal control model for simulating obstacle-avoiding movements through adding an obstacle-avoiding condition to the three-joint arm's optimal control model and examines how the proposed model can reproduce human arm's experimentally measured obstacle-avoiding movement characteristics. The obstacle-avoiding condition is an equality constraint representing that the model's hand point intersects with the circumference of a hypothetical circle with a radius (obstacle-avoiding radius) of rab around the obstacle at time (obstacle-avoiding time) of t_1. Consequently, the following results are obtained: (1) the proposed model can reproduce human arm's experimentally measured obstacle-avoiding movement characteristics by selecting appropriate values of the obstacle-avoiding radius and time; (2) the model's obstacle-avoiding radius and time can be factors for realizing obstacle-avoiding movements. These results suggest that the proposed model can be an effective and plausible model for the human arm's obstacle-avoiding movement mechanism.
