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.

I. Introduction

Human-centered environment is one of the most important application scenarios for robot [1]. Close cooperation between human beings and robots significantly enhances the working efficiency. Robots can also serve as the companion and assistant to humans as part of human life. Under human-centered conditions, the vital considerations for robot design are safety, adaptability, task-worthiness, and affordability compared to robots focused on force, speed and accuracy of traditional industrial robots [2]. Soft robots with inherent compliance provide an effective solution for safe robot-environment and robot-human interaction [3], [4]. Existing works have demonstrated potential of soft robot to solve challenges in areas such as human-centered grasping [5], [6], manipulation [7], [8], rehabilitation [9], [10], medical applications [11], [12], and novel robotic applications [13], [14].