Artificial muscle driven soft hydraulic robot: electromechanical actuation and simplified modeling

Soft pneumatic actuators possess attributes of large deformation, high driving force and light weight in the application of soft robots and smart devices. However, most reported soft pneumatic actuators are with rigid hydraulic source such as motor driven pump, piston and pressurized reservoir. These rigid and heavy hydraulic sources limit the actuation and compliance of the soft robots. Inspired by the bladders and hydrostatic skeleton of natural creatures, we propose a soft hydraulic robot consisting of dielectric elastomer (DE) and hydrogel, exhibiting an excellent actuating performance. An inflated DE balloon functions as the soft hydraulic source, in which the pressure of the containing water can be tuned by voltage. Hydrogel chambers are connected to the DE balloon as the hydraulic actuator, deforming as a soft robotic gripper. A new analytical approach is proposed to describe the system's behaviors, which couples the electromechanical actuation of DE and the hydraulic deformation of hydrogel chamber. The proposed model is validated by good agreement between the numerical and experimental data. The proposed model could serve as a new tool for modeling and characterizing soft robots with hydraulic actuation. The working principles can guide the design and control of soft robots and smart structures.