Grasping mechanisms must both create and subsequently hold grasps that permit safe and effective object manipulation. Traditional mechanisms address the different functional requirements of grasp creation and grasp holding using a single morphology, but have yet to achieve the simultaneous strength, gentleness, and versatility needed for many applications. We present “loop closure grasping,” a method of robotic grasping that addresses these different functional requirements through topological transformations between open-loop and closed-loop morphologies. Topologically open-loop mechanisms enable versatile grasp creation via unencumbered tip movement around the object, but lack the simultaneous strength and compliance needed for holding heavy yet fragile objects. Closed-loop mechanisms (e.g., slings) can bear heavy loads in a passive cradled state with effectively infinite bending compliance, but present challenges for grasp creation because the object must somehow enter the loop. Loop closure grasping circumvents the tradeoffs of single-morphology designs by transforming the mechanism’s topology from open-loop to closed-loop between the grasp creation and holding stages. We formalize these morphologies for grasping, formulate the loop closure grasping method, and present a design architecture and implementation using soft growing inflated beams, winches, and clamps. Finally, we demonstrate grasps involving historically challenging objects, environments, and configurations.  

Pneumatic soft everting robotic structures have the potential to facilitate human transfer tasks due to their ability to grow underneath humans without sliding friction and their utility as a flexible sling when deflated. Tubular structures naturally yield circular cross-sections when inflated, whereas a robotic sling must be both thin enough to grow between them and their resting surface and wide enough to cradle the human. Recent works have achieved flattened cross-sections by including rigid components into the structure, but this reduces conformability to the human. We present a method of mechanically programming the cross-section of soft everting robotic structures using flexible strips that constrain radial expansion between points along the outer membrane. Our method enables simultaneously wide and thin profiles while maintaining the full multi-axis flexibility of traditional slings. We develop and validate a model relating the geometric design specifications to the fabrication parameters, and experimentally characterize their effects on growth rate. Finally, we prototype a soft growing robotic sling system and demonstrate its use for assisting a single caregiver in bed-to-chair patient transfer.

The navigational abilities of tip-everting soft growing robots, known as vine robots, are compromised when tip-mount devices are added to enable carrying of payloads. We present a new method for securing a vine robot to objects or its environment that exploits the unique eversion-based growth mechanism and flexibility of vine robots, while keeping the tip of the vine robot free of encumbrance. Our implementation is a tip-clutching winch, into which vine robots can insert themselves and anchor to via powerful overlapping belt friction. The device enables passive, high-strength, and reversible fastening, and can easily release the vine robot. This approach enables carrying of loads of at least 28 kg (limited by the tensile strength of the vine robot body material and winch actuator torque capacity), as well as novel material transport and locomotion capabilities.

* Tutorial: softrobotics.io/post/make-a-robotic-strap 

Safely harnessing and lifting humans for transfer is a challenging unsolved problem for current robots because of the high forces and gentle interaction necessary to do so. Humans are heavy, delicate, deformable, and vary widely in shape and pose. Standard robotic manipulators and end-effectors cannot achieve sufficiently gentle human interaction while applying the high forces needed to lift the body effectively, although many high impact tasks depend on this functionality. Straps, however, are highly beneficial for manually performing this task primarily because of their simultaneously high tensile strength and high compliant bending flexibility, in that (1) the high tensile strength allows for load bearing capacities great enough to lift the full weight of the human, and (2) the high bending flexibility allows for the high passive compliance and conformity needed to safely distribute these large forces across the body.

We present the Robotic Strap, a novel concept and design for a new type of manipulator that can passively harness and lift humans safely as straps can, as well as actively articulate itself around the human into the desired harnessing configurations. The Robotic Strap manipulator is the first robot to demonstrate automatic harnessing and lifting of a human above the ground. The design is characterized by the high tensile strength and bending flexibility of straps, and its implementation consists of a hyper-articulated backbone with rolling-contact joints and embedded soft pneumatic artificial muscles. In our paper, “A High-Strength, Highly-Flexible Robotic Strap for Harnessing, Lifting, and Transferring Humans", we present the concept, framework, realization, and implementation of the Robotic Strap design, as well as model and experimentally validate the key characteristics. The prototype has a tensile load capacity of 1314.0 N, a maximum joint bending resistance of <0.1 Nm, and successfully demonstrated safe and effective harnessing and lifting of three human participants without any manual intervention. This new manipulator design paradigm unlocks significant advances in robotic handling of heavy yet gentle objects, enabling new capabilities in important applications such as elderly care, occupational therapy, emergency medical response, search and rescue.

I worked as a visiting scholar with Dr. Yan Gu on bipedal walking control and simulation. I assisted the development of a trajectory tracking controller for multi-domain hybrid models of bipedal walking based on control Lyapunov functions and quadratic programming.

I worked as a research assistant with Dr. William Messner on the design and development of an assistive robotic platform for people with physical disabilities during my first year at Tufts University. I developed a teleoperated assistive mobile manipulator based on a minimal-DOF design approach I formulated. This approach allows direct-manipulation control to maximize the user’s agency over its behavior while maintaining sufficient functionality. With the goal of developing a practical platform that could be accepted into people’s everyday lives, I developed the project by formulating a direction that addressed the relationship between the system’s DOF and the user’s control agency. I collaborated with the Tufts Occupational Therapy department to conduct multiple user studies with participants with tetraplegia to evaluate the performance and usability of the platform.

I designed and developed a wireless vibrating tensegrity robot during my junior and senior years of my undergraduate at Union College as a part of Dr. John Rieffel’s research on evolutionary robotics and morphological communication. The struts were designed to excite the resonant frequencies of the robot.

• Designed, modeled, fabricated, and tested a wireless vibrating tensegrity strut to complete the world’s first wireless vibrating tensegrity robot, which serves as a reliable and modular test subject for genetic algorithm experiments.

• Designed for rapid manufacturing (only necessary fabrication processes are: laser cutting, waterjet cutting, and soldering)

• Developed a resonance model of a single strut to validate the FEA model for the resonant modes of the robot.

• Designed a custom vibration motor to match the resonant frequency range and maximize amplitude.

• Implemented onboard IMU and data collection for motion tracking of individual struts during locomotion.