  Controlling soft continuum robotic arms is challenging due to their
hyper-redundancy and dexterity. In this paper we demonstrate, for the first
time, closed-loop control of the configuration space variables of a soft
robotic arm, composed of independently controllable segments, using a Cosserat
rod model of the robot and the distributed sensing and actuation capabilities
of the segments. Our controller solves the inverse dynamic problem by
simulating the Cosserat rod model in MATLAB using a computationally efficient
numerical solution scheme, and it applies the computed control output to the
actual robot in real time. The position and orientation of the tip of each
segment are measured in real time, while the remaining unknown variables that
are needed to solve the inverse dynamics are estimated simultaneously in the
simulation. We implement the controller on a multi-segment silicone robotic arm
with pneumatic actuation, using a motion capture system to measure the
segments' positions and orientations. The controller is used to reshape the arm
into configurations that are achieved through different combinations of bending
and extension deformations in 3D space. The resulting tracking performance
indicates the effectiveness of the controller and the accuracy of the simulated
Cosserat rod model that is used to estimate the unmeasured variables.
