Nonlinear Optimal Control of a Soft Robotic Structure Actuated by Dielectric Elastomer Artificial Muscles

In the field of soft robotics, Dielectric Elastomer Actuators (DEAs) represent a compact and efficient alternative to bulky pneumatic drives. Both soft robots and DEAs show highly nonlinear behaviours due to their intrinsic large deformations, making the design of dynamic controllers highly challenging. At present, the problem of position control of DEA soft robots has not yet been explored in the literature. In this paper, we directly account for the nonlinearities of a DEA-driven soft robotic structure using an Adaptive Dynamic Programming (ADP) approach. We develop for the first time a closed-loop optimal controllers for position regulation of a DEA soft robot, by approximating the solution of the Hamilton-Jacobi-Bellman equation with Neural Networks (NNs). We extend an existing model-based ADP approach to deal also with asymmetric input constraints. Simulation studies asses the improvements in positioning performance of the proposed approach, in comparison to traditional strategies.