BiFlex: A Passive Bimodal Stiffness Flexible Wrist for Manipulation in Unstructured Environments

Gu-Cheol Jeong, Stefano Dalla Gasperina, Ashish Deshpande, Lillian Chin, Roberto Martín-Martín

Keywords: Bimodal Stiffness, Manipulation, Soft Robotics, Flexible Robotic Wrist, Collision Robustness

TL;DR: BiFlex is a flexible robotic wrist with a soft buckling honeycomb structure providing high stiffness for precision and low stiffness for compliance, ensuring safe and simple robot control in unstructured environments.

Abstract: Robotic manipulation in unstructured, human-centric environments poses a dual challenge: achieving the precision need for delicate free-space operation while ensuring safety during unexpected contact events. Traditional wrists struggle to balance these demands, often relying on complex control schemes or complicated mechanical designs to mitigate potential damage from force overload. In response, we present BiFlex, a flexible robotic wrist that uses a soft buckling honeycomb structure to provides a natural bimodal stiffness response. The higher stiffness mode enables precise household object manipulation, while the lower stiffness mode provides the compliance needed to adapt to external forces. We design BiFlex to maintain a fingertip deflection of less than 1cm while supporting loads up to 500g and create a BiFlex wrist for many grippers, including Panda, Robotiq, and BaRiFlex. We validate BiFlex under several real-world experimental evaluations, including surface wiping, precise pick-and-place, and grasping under environmental constraints. We demonstrate that BiFlex simplifies control while maintaining precise object manipulation and enhanced safety in real-world applications. More information and videos at https://robin-lab.cs.utexas.edu/BiFlex/

Submission Number: 3