Electrohydraulic Jammed Variable Stiffness Robotic Link

Robotic links play a vital role in transmitting force and torque, ensuring precise robotic movements. Traditional rigid links, typically made from metals, pose a risk of injury in human-robot interactions or damage to other objects due to their noncompliant and stiff nature and have limited adaptability across various tasks. Variable stiffness robotic links (VSRLs) using hydraulically amplified self-healing electrostatic (HASEL) actuators offer a solution, enhancing safety and adaptability while maintaining precision. This study introduces an electrohydraulic jammed VSRL utilizing a strip-shaped HASEL actuator, which stiffens upon application of high-voltage, pressurizing dielectric liquid encased in a dielectric bladder to achieve stiffness variations up to 8.3 times. The VSRL, optimized by adjusting liquid volume and sealing patterns, is lightweight and compact and eliminates the need for bulky pumps and motors. It also functions as a capacitor, enabling a self-sensing strategy to detect deformation. Experimental results demonstrate significant stiffness variability and effective load-bearing capabilities. Multi-VSRL assemblies further enhance stiffness for practical applications, including collaborative robotic links and wearable robots for joint support. A unique drone application showcases the VSRL's potential for energy-efficient aerial operations. The proposed VSRL represents a promising advancement in robotic technology, offering improved safety, adaptability, and functionality for diverse real-world applications.