Full-body Grasping Strategy for Planar Underactuated Soft Manipulators using Passivity-based Control

Abstract

Soft robotics is a branch of robotics that aims to emulate nature by exploring so-called soft materials. By utilizing the embedded softness, various degrees of dexterity in grasping can be achieved without the need for advanced controllers. However, when compared to nature (and modern rigid robots), comparable levels of dexterity and object manipulation are still lacking. For example, when considering the elephant's trunk, whole-body manipulation and sensory feedback are explored to achieve simultaneous, robust, and adaptive grasping. In this work, we incorporate closed-loop control into soft robotic grasping. Using passivity-based control, we achieve whole-body grasping for planar, slender, soft manipulators with torque actuation. Our approach also accounts for the underactuation present in these systems and adapts the grasping strategy accordingly. Furthermore, we explore damping injection without velocity measurements to enhance the attenuation of undesired oscillatory motion. The performance of the closed-loop system is evaluated through simulation and experiments.