Low-cost actuators offer new twist on artificial ‘muscles’ for safer, softer robots

Crawling robotic and synthetic muscle collectively. Credit: Ryan Truby/Taekyoung Kim/Northwestern University

Northwestern University engineers have developed a brand new delicate, versatile system that makes robots transfer by increasing and contracting—similar to a human muscle.

To reveal their new system, known as an actuator, the researchers used it to create a cylindrical, worm-like soft robot and a synthetic bicep. In experiments, the cylindrical delicate robotic navigated the tight, hairpin curves of a slender pipe-like atmosphere, and the bicep was in a position to elevate a 500-gram weight 5,000 instances in a row with out failing.

As a result of the researchers 3D-printed the physique of the delicate actuator utilizing a typical rubber, the ensuing robots value about $3 in supplies, excluding the small motor that drives the actuator’s form change. That sharply contrasts typical stiff, inflexible actuators utilized in robotics, which frequently value a whole lot to 1000’s of {dollars}.

The brand new actuator may very well be used to develop cheap, delicate, versatile robots, that are safer and extra sensible for real-world functions, researchers stated.

The analysis was published July 8 within the journal Superior Clever Methods.

“Roboticists have been motivated by a long-standing goal to make robots safer,” stated Northwestern’s Ryan Truby, who led the examine.

“If a soft robot hit a person, it would not hurt nearly as much as getting hit with a rigid, hard robot. Our actuator could be used in robots that are more practical for human-centric environments. And, because they are inexpensive, we potentially could use more of them in ways that, historically, have been too cost prohibitive.”

Truby is the June and Donald Brewer Junior Professor of Supplies Science and Engineering and Mechanical Engineering at Northwestern’s McCormick College of Engineering, the place he directs The Robotic Matter Lab. Taekyoung Kim, a postdoctoral scholar in Truby’s lab and first writer on the paper, led the analysis. Pranav Kaarthik, a Ph.D. candidate in mechanical engineering, additionally contributed to the work.

Robots that ‘behave and transfer like residing organisms’

Whereas inflexible actuators have lengthy been the cornerstone of robotic design, their restricted flexibility, adaptability and security have pushed roboticists to discover soft actuators instead. To design delicate actuators, Truby and his staff take inspiration from human muscle groups, which contract and stiffen concurrently.

“How do you make materials that can move like a muscle?” Truby requested. “If we can do that, then we can make robots that behave and move like living organisms.”

To develop the brand new actuator, the staff 3D-printed cylindrical constructions known as “handed shearing auxetics” (HSAs) out of rubber. Troublesome to manufacture, HSAs embody a complex structure that permits distinctive actions and properties. For instance, when twisted, HSAs prolong and broaden. Though Truby and Kaarthik 3D-printed related HSA constructions for robots prior to now, they have been certain to utilizing costly printers and inflexible plastic resins. In consequence, their earlier HSAs couldn’t bend or deform simply.

“For this to work, we needed to find a way to make HSAs softer and more durable,” stated Kim. “We figured out how to fabricate soft but robust HSAs from rubber using a cheaper and more easily available desktop 3D printer.”

Kim printed the HSAs from thermoplastic polyurethane, a typical rubber typically utilized in cellphone circumstances. Whereas this made the HSAs a lot softer and extra versatile, one problem remained: the best way to twist the HSAs to get them to increase and broaden.

Earlier variations of HSA delicate actuators used widespread servo motors to twist the supplies into prolonged and expanded states. However the researchers solely achieved profitable actuation after assembling two or 4 HSAs—every with its personal motor —collectively. Constructing delicate actuators on this manner offered fabrication and operational challenges. It additionally decreased the softness of the HSA actuators.

To construct an improved delicate actuator, the researchers aimed to design a single HSA pushed by one servo motor. However first, the staff wanted to discover a technique to make a single motor twist a single HSA.

New twist on artificial 'muscles' for safer, softer robots
Single actuator stretches and bends. Credit: Ryan Truby/Taekyoung Kim/Northwestern University

Simplifying ‘the complete pipeline’

To unravel this downside, Kim added a delicate, extendable, rubber bellows to the construction that carried out like a deformable, rotating shaft. Because the motor offered torque—an motion that causes an object to rotate—the actuator prolonged. Merely turning the motor in a single course or the opposite drives the actuator to increase or contract.

“Essentially, Taekyoung engineered two rubber parts to create muscle-like movements with the turn of a motor,” Truby stated. “While the field has made soft actuators in more cumbersome ways, Taekyoung greatly simplified the entire pipeline with 3D printing. Now, we have a practical soft actuator that any roboticist can use and make.”

The bellows added sufficient help for Kim to construct a crawling delicate robotic from a single actuator that moved by itself. The pushing and pulling motions of the actuator propelled the robotic ahead via a winding, constrained atmosphere simulating a pipe.

“Our robot can make this extension motion using a single structure,” Kim stated. “That makes our actuator more useful because it can be universally integrated into all types of robotic systems.”

The lacking piece: Muscle stiffening

The ensuing worm-like robotic was compact (measuring simply 26 centimeters in size) and crawled—each back and forth—at a pace of simply over 32 centimeters per minute. Truby famous that each the robot and synthetic bicep develop into stiffer when the actuator is totally prolonged. This was yet one more property that earlier delicate robots have been unable to attain.

“Like a muscle, these soft actuators actually stiffen,” Truby stated. “If you have ever twisted the lid off a jar, for example, you know your muscles tighten and get stiffer to transmit force. That’s how your muscles help your body do work. This has been an overlooked feature in soft robotics. Many soft actuators get softer when in use, but our flexible actuators get stiffer as they operate.”

Truby and Kim say their new actuator gives yet one more step towards extra bioinspired robots.

“Robots that can move like living organisms are going to enable us to think about robots performing tasks that conventional robots can’t do,” Truby stated.

Extra info:
Taekyoung Kim et al, A Versatile, Architected Delicate Robotic Actuator for Motorized Extensional Movement, Superior Clever Methods (2024). DOI: 10.1002/aisy.202300866

Low-cost actuators provide new twist on synthetic ‘muscle groups’ for safer, softer robots (2024, July 10)
retrieved 10 July 2024

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