  The 'infinite' passive degrees of freedom of soft robotic arms render their
control especially challenging. In this paper, we leverage a previously
developed model, which drawing equivalence of the soft arm to a series of
universal joints, to design two closed-loop controllers: a configuration space
controller for trajectory tracking and a task space controller for position
control of the end effector. Extensive experiments and simulations on a
four-segment soft arm attest to substantial improvement in terms of: a)
superior tracking accuracy of the configuration space controller and b) reduced
settling time and steady-state error of the task space controller. The task
space controller is also verified to be effective in the presence of
interactions between the soft arm and the environment.
