  Existing gaze controllers for head-eye robots can only handle single fixation
points. Here, a generic controller for head-eye robots capable of executing
simultaneous and prioritized fixation trajectories in Cartesian space is
presented. This enables the specification of multiple operational-space
behaviors with priority such that the execution of a low priority head
orientation task does not disturb the satisfaction of a higher prioritized eye
gaze task. Through our approach, the head-eye robot inherently gains the
biomimetic vestibulo-ocular reflex (VOR), which is the ability of gaze
stabilization under self generated movements. The described controller utilizes
recursive null space projections to encode joint limit constraints and task
priorities. To handle the solution discontinuity that occurs when joint limit
tasks are inserted or removed as a constraint, the Intermediate Desired Value
(IDV) approach is applied. Experimental validation of the controller's
properties is demonstrated with the Dreamer humanoid robot. Our contribution is
on (1) the formulation of a desired gaze task as an operational space
orientation task, (2) the application details of the IDV approach for the
prioritized head-eye robot controller that can handle intermediate joint
constraints, and (3) a minimum-jerk specification for behavior and trajectory
generation in Cartesian space.
