Model Based Position Control of Soft Hydraulic Actuators

-- In this article, we investigate the model based position control of soft hydraulic actuators arranged in an antagonistic pair . A dynamical model of the system is constructed by employing the port-Hamiltonian formulation. A control algorithm is designed with an energy shaping approach, which accounts for the pressure dynamics of the fluid. A nonlinear observer is included to compensate the effect of unknown external forces. Simulations demonstrate the effectiveness of the proposed approach, and experiments achieve positioning accuracy of 0.043 mm with a standard deviation of 0.033 mm in the presence of constant external forces up to 1 N. Soft robotic systems possess many of the features required in minimally invasive surgery (MIS), including low weight and compliance similar to that of biological systems [1]. In addition, soft robots allow for affordable designs by replacing expensive actuators with low-cost solutions that can be produced locally in a low-resource setting [2].