A Proprioceptive Bellows (PB) Actuator with Position Feedback and Force Estimation

Soft robot is known for great safety in human-centered environments due to its inherent compliance. However, the compliance resulting from the soft continuum structure and viscoelastic material also induces challenges for sensing and control of soft robots. In this letter, we propose a proprioceptive soft actuator design approach based on 3D printed conductive material and 3D printed deformable structure, such as bellows. The conductive bellow exhibits effective resistance change and structural deformation, thus provides a promising solution for the challenge of deformable soft robots that need integrated actuation and sensing. The proposed proprioceptive bellow actuator (PB actuator) achieves effective position feedback and real-time output force estimation. Using a dedicated control logic of the pressure controller, the PB actuator can not only provide anticipated motion but also estimate the interactive force based on real-time position sensing and input pressure. The design, fabrication, modeling, control, and experimental validation of our proposed PB actuator are discussed in detail in this letter. The parameters of PB actuator are highly customizable depending on the intended applications. Based on the proposed PB actuator, two specialized grippers, T and Y gripper, are designed and prototyped to demonstrate the grasping force estimation capability. The proposed proprioceptive soft robotic approach provides a promising solution to design behavior steerable soft robots.