Gaze controls with interactions and delays

摘要

Five control systems loosely corresponding to primate saccadic, vergence, pursuit, vestibule-ocular, and head control operate on a simulated two-eyed robot head maneuvered by a robot arm. The goal is to get some qualitative understanding of the interaction of such reflexes under various assumptions. The simulation is meant to be relevant to U. Rochester's robot. Thus it incorporates kinematics of the robot head but assumes a "tool-coordinate" system available to robot arm commands, so that arm kinematic calculations are unnecessary. Dynamics are not modeled, since they are handled by the commercial controllers currently used in the Rochester robot. Even small delays render the effect of delay-free controllers unstable, but multi-delay version of a Smith predictor can cope with delays. If each controller acts on the predicted system and ignores other controllers, the situation is improved but still potentially unstable if controllers with different delays act on the same control output. The system's performance is much improved if controllers consider the effect of other controllers, and the resulting system is stable in the presence of a certain amount of stochastic disturbance of control delays and inputs, and also in the presence of systematic error arising from inaccurate plant and world models.