Dynamic Control of Soft Robotic Arm: An Experimental Study

The objective of this letter is to investigate the dynamic control of a soft robotic arm. First, a modular soft robotic hardware and an affordable actuator-space encoder were presented. We then discussed the soft robot modeling, and adaptive passivity control strategy with stability proof. The proposed controller was tested in different operation scenarios, and compared to the standard PD feedback linearization control and passivity control. In all experimental settings, the adaptive passivity control scheme was able to achieve superior performance, even with significant modeling uncertainties and disturbances. The theoretical analysis and experimental validations of the proposed controller will pave the way toward the practical implementations of the soft robotic system in the dynamic scenarios.

I. Introduction

Soft robots, inspired by nature, have been introduced to the robotics community to provide abilities that can surpass their rigid counterparts [1]. These robots are made from inherently elastic materials such as silicone or rubber, emulating biological structures while improving robot safety and compliance [2]. They can be considered as the infinite degree of freedom systems due to the elastic materials, which can present different adaptive, agile motions ranging from elongation, twisting, bending, etc. [3]. These behaviors make soft robots an ideal tool for different applications, including grasping [4], [5], medical procedures [6], [7], rehabilitation [8], agricultural harvesting [9], snake locomotion [10], etc. Among them, manipulation has often been considered one of the most important robotic applications. Despite much progress have been made in the past 20 years, controlling these soft robots to achieve desired tracking performance in dynamic operation scenarios remains challenging [11].