  This paper presents a visual-inertial-based control strategy to address the
task space control problem of robot manipulators. To this end, an
observer-based hybrid controller is employed to control end-effector motion. In
addition, a hybrid observer is introduced for a visual-inertial navigation
system to close the control loop directly at the Cartesian space by estimating
the end-effector pose. Accordingly, the robot tip is equipped with an inertial
measurement unit (IMU) and a stereo camera to provide task-space feedback
information for the proposed observer. It is demonstrated through the Lyapunov
stability theorem that the resulting closed-loop system under the proposed
observer-based controller is globally asymptotically stable. Besides this
notable merit (global asymptotic stability), the proposed control method
eliminates the need to compute inverse kinematics and increases trajectory
tracking accuracy in task-space. The effectiveness and accuracy of the proposed
control scheme are evaluated through computer simulations, where the proposed
control structure is applied to a 6 degrees-of-freedom long-reach hydraulic
robot manipulator.
