Design, manufacturing, and inverse dynamic modeling of soft parallel robots actuated by dielectric elastomer actuators

TL;DR

This paper presents the design, fabrication, and inverse dynamic modeling of a soft parallel Delta robot actuated by dielectric elastomer actuators, demonstrating improved force prediction and trajectory tracking accuracy.

Contribution

It introduces a novel design with an angular stroke amplification mechanism and a new electrode fabrication method, along with an inverse dynamic model for dielectric elastomer actuators.

Findings

Robot output force prediction RMSE of 12.4%

Trajectory tracking RMSE less than 2.5%

Enhanced electrode consistency and dynamic behavior

Abstract

Soft parallel robots with their manipulation safety and low commercial cost show a promising future for delicate operations and safe human-robot interactions. However, promoting the use of electroactive polymers (EAPs) is still challenging due to the under-improving quality of the product and the dynamic modelling of the collaborations between multiple actuators. This article presents the design, fabrication, modelling and control of a parallel kinematics Delta robot actuated by dielectric elastomer actuators (DEAs). The trade-off between the actuation force and stroke is retaken by an angular stroke amplification mechanism, and the weight of the robot frame is reduced by utilizing 3D puzzling strip structures. A generic way of constructing a high-stability conductive paint on a silicon-based film has been achieved by laser scanning the DE-film and then sandwiching a conductive particle-based electrode with a paint which is mixed by the particles and photosensitive resin. Compared to the wildly used carbon grease, the fabricated electrode shows a higher consistency in its dynamic behaviour before and after the on-stand test. Finally, to predict the output force and inverse motion of the robot end effector, we constructed the inverse dynamic model by introducing an expanded Bergstrom-Boyce model to the constitutive behavior of the dielectric film. The experimental results show a prediction of robot output force with RSME of 12.4% when the end effector remains stationary, and a well-followed trajectory with less than RSME 2.5%.