In the world of gardening, certain vines are particularly attractive. As they grow, the woody tendrils can wrap around obstacles with enough force to bring down entire fences and trees.
Inspired by the durability of twisting vines, engineers from MIT and Stanford University developed a robotic gripper that can circle and pick up various objects, including a glass vase and a watermelon, providing a more gentle approach compared to conventional gripper designs. A larger version of the robo-whisker can also safely lift a person out of bed.
The recent bot consists of a pressurized box placed near a target object, from which long vine-like tubes inflate and sprout like inside-out socks. As they stretch, the vines wrap and wrap around the object before returning to the box, where they are automatically secured in place and mechanically retracted to gently lift the object in a supple, slingshot-like embrace.
Scientists have demonstrated that the vine robot can safely and stably lift a variety of bulky and exquisite objects. The robot can also squeeze through tight spaces and push through clutter to reach and grab a desired object.
The team anticipates that this type of robotic gripper could be used in a wide range of scenarios, from agricultural harvesting to loading and unloading bulky loads. In the near future, the group is exploring applications in aged care facilities, where supple inflatable automatic vines could aid gently lift a person out of bed.
“Moving a person out of bed is one of the most physically demanding tasks a caregiver performs,” says Kentaro Barhydt, a graduate student in MIT’s Department of Mechanical Engineering. “This type of robot can help reduce the burden on the caregiver and may be gentler and more comfortable for the patient.”
Barhydt, along with his Stanford co-first author O. Godson Osele and their colleagues, present a new robot design in the magazine today . Co-authors of the study include Harry Asada, the Ford Professor of Engineering at MIT, and Allison Okamura, the Richard W. Weiland Professor of Engineering at Stanford University, as well as Sreela Kodali and Cosmia du Pasquier at Stanford University, and former MIT graduate Chase Hartquist, now at the University of Florida in Gainesville.
Open and closed
Source: courtesy of researchers
The Stanford team, led by Okamura, pioneered the development of vine-inspired supple robots that grow outward from tips. These structures are largely constructed of slim but robust pneumatic tubes that grow and inflate under controlled air pressure. As they grow, the tubes can twist, bend and snake through their surroundings and squeeze through tight and cluttered spaces.
Researchers mainly investigated the apply of vine robots in security inspections and search and rescue operations. But at MIT, Barhydt and Asada, whose group has developed assistive robots for the elderly, wondered whether such vine-inspired robots could address certain challenges in elder care—specifically, the challenge of safely lifting a person out of bed. Often in nursing and rehabilitation facilities, the patient transfer process is accomplished using a lift operated by a caregiver who must first physically move the patient to the side and then back onto a hammock-like sheet. The caregiver ties a sheet around the patient and suspends it from a mechanical lift, which can then gently lift the patient out of bed, much like hanging a hammock or scarf.
The MIT and Stanford team came up with an alternative solution that would be a vine-like robot that could gently snake under and around the patient, creating its own kind of sling, without the caregiver having to physically maneuver the patient. But to lift the slingshot, researchers realized they would have to add an element that was missing in existing vine robot designs: they would essentially have to close the loop.
Most vine-inspired robots are designed as “open loop” systems, meaning they act like open strings that can stretch and bend in various configurations, but are not designed to attach to anything and form a closed loop. Barhydt speculated that if a climbing robot could be made to transform from an open loop to a closed loop, it could transform into a slingshot around an object and pull itself up with anything or anyone it might be holding.
For the recent study, Barhydt, Osele and their colleagues outline the design of a recent vine-inspired gripping robot that combines open- and closed-loop operation. In an open-loop configuration, the robotic vine can grow and twist around an object to provide a firm grip. It can even burrow under a person lying on the bed. Once captured, the vine can continue to grow towards the source and attach to it, creating a closed loop that can then be retracted to retrieve the object.
“People may assume that to grab something, you just reach out and grab it,” Barhydt says. “But there are different stages, such as positioning and holding. By switching between open and closed loops, we can achieve new levels of performance by using the advantages of both forms at the appropriate stages.”
Exquisite suspension
To demonstrate their recent open and closed loop concept, the team built a large-scale robotic system designed to safely lift a person out of bed. The system consists of a set of pressure boxes attached to both ends of a suspension rod. An air pump inside the boxes slowly inflates and unwinds slim vine-like tubes that extend down towards the head and foot of the bed. Air pressure can be adjusted to gently move the tubes under and around the person before stretching them back into their appropriate boxes. The vine is then threaded through a clamping mechanism that secures the vine to each box. The winch winds the vines back towards the boxes, gently lifting the person.
“Heavy but delicate objects like the human body are difficult to grasp with currently available robotic hands,” Asada says. “We have developed a vine-like growing robotic gripper that can wrap around an object and suspend it gently and safely.”
“There is a whole design space out there, we hope this work will inspire our colleagues to explore further,” says co-author Osele. “I am particularly looking forward to the implications for patient transfer requests in health care.”
“I am very excited about future work on using such robots to physically assist people with mobility problems,” adds co-author Okamura. “Soft robots can be relatively safe, inexpensive, and optimally designed for specific human needs, unlike other approaches such as humanoid robots.”
Although the team’s design was motivated by the challenges of caring for the elderly, the researchers realized that the recent design could also be adapted to perform other grasping tasks. In addition to the large-scale system, they built a smaller version that can be attached to a commercial robotic arm. With this version, the team showed that the vine robot could grab and lift a variety of bulky and exquisite objects, including a watermelon, a glass vase, a kettle bell, a stack of metal bars, and a toy ball. The vine can also slither through a cluttered basket to retrieve a desired item.
“We think this type of robot design can be adapted to many applications,” says Barhydt. “We are also thinking about using it in heavy industry and, for example, automating the operation of cranes in ports and warehouses.”
This work was supported in part by the National Science Foundation and the Ford Foundation.