  This paper presents an offset-free model predictive controller for fast and
accurate control of a spherical soft robotic arm. In this control scheme, a
linear model is combined with an online disturbance estimation technique to
systematically compensate model deviations. Dynamic effects such as material
relaxation resulting from the use of soft materials can be addressed to achieve
offset-free tracking. The tracking error can be reduced by 35% when compared to
a standard model predictive controller without a disturbance compensation
scheme. The improved tracking performance enables the realization of a ball
catching application, where the spherical soft robotic arm can catch a ball
thrown by a human.
