Design of a Soft Multi-Degree of Freedom Tool Positioner With Variable Stiffness Integrating Molded Air Muscles Actuation, Granular Jamming and Dielectric Elastomer Sensing

Abstract

Soft technology is more and more present in robotics allowing safe interaction with humans, high dexterity in constrained environments, and safe manipulation of fragile or undefined objects. However, soft robotics is limited by a fundamental trade-off between available workspace and stiffness. Position feedback is also challenging as soft robots generally use deformable mechanisms instead of discrete joints. Here, the design of a soft four-degree-of-freedom tool positioner integrating a brake system and a soft sensor is proposed to address these issues. The design integrates molded air muscle actuators, granular jamming brakes, and Dielectric Elastomer Sensors (DES). The design is experimentally validated based on the requirements of a manipulator for liver cancer treatment, which is a representative application of soft robotics. The use of granular jamming mitigates the fundamental trade-off of soft robotics as it allows the manipulator to reach a large workspace (1500 cm3) while having the capacity to provide a high stiffness (up to19 times the initial stiffness). DES provides satisfactory position feedback, demonstrating a 0.69 mm accuracy that is lower than the 1 mm requirement. The proposed design using granular jamming and DES could greatly benefit human-safe and medical robotics.