Robust control strategy for improving the performance of a soft robotic link

The robotic neck mechanism considered in this paper has as main element a soft link that emulates a human neck with two DOF (flexion, extension and lateral bending). The mechanism is based on a Cable-Driven Parallel Mechanism (CDPM) with components easy to manufacture in a 3D printer.Due to the soft link properties and the platform mechanics, it is important to provide a robust control system. Two designs, a robust PID controller and a Fractional Order PI controller (FOPI) are proposed and compared, the fractional order control showing an enhanced performance. Both control approaches are tested in the real prototype, validating the soft neck feasibility and showing the robustness of the platform to mass changes at the neck tip.