Who Wants An Extra Pair of Robot Arms?

 Robotics  

Researchers at MIT have created working prototypes of Supernumerary Robotic Limbs, extra robot arms that work with your body movements and machine learning, to help with tasks that are difficult to do with just your own two arms.

Supernumerary Robotic Limbs (SRLs) are robotic limbs that, when worn, give you more limbs than you'd normally have. In other words, they're not robotic limbs designed to replace biological limbs that you might be missing, but rather robotic limbs designed to augment the number of limbs that you have already. Think Doc Ock, from Spider-Man

Now, MIT researchers have been developing SRLs that can help you do those annoying, uncomfortable, or impossible tasks on your own. At the IEEE International Conference on Robotics and Automation (ICRA) in Hong Kong, they presented their latest SRL prototypes, with one model featuring a pair of limbs that spring from your shoulders and another with limbs that extend from your waist as part of their paper, "A Robot on the Shoulder: Coordinated Human-Wearable Robot Control using Coloured Petri Nets and Partial Least Squares Predictions."

"Once we combine the most significant behavioral modes we are able to control the robot such that, from the wearer's perspective, it behaves like an extension of his own body."

MIT's shoulder-mounted SRL is designed to assist in tasks that take place over your head, or in situations where your other two arms are busy and you need a hand (literally) with something. One example, shown in the video below, would be in a construction context, where anything that needs to be attached to a ceiling has to be held up and hammered or screwed into place at the same time. In another example the system is demonstrated while opening a door when the user holding something with both hands.

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The bionic shoulder robot uses two arms mounted on your shoulders such that the reaction forces on them are aligned with the spine. Each arm has five degrees of freedom, with interchangeable and customizable end effectors, and the complete systems weighs about 4.5 kilograms (10 pounds).

The control system for the SRL watches what you're doing with your arms to decide how to move. It does that by monitoring two inertial measurement units (IMUs) that the user wears on the wrists. A third IMU sits at the base of the robot’s shoulder mount, to track the overall orientation and motion of the SRL. This natural interface overcomes the inherent problem of controlling the extra arms, while keeping your own arms and hands free.

The SRL uses the gyro and accelerometer data from the IMUs to make a prediction (based on a model that's been created by machine learning) about what would be the most helpful, proactive position for its own arms. If you put your arms up above your head, for example, the SRLs raise above your head too, because it figures you're trying to hold something up. Using their SRL prototype, the researchers are testing different "behavioral modes" to program the limbs to do what they want.

"Once we combine the most significant behavioral modes we are able to control the robot such that, from the wearer's perspective, it behaves like an extension of his own body," says Baldin Llorens-Bonilla, a researcher at the d'Arbeloff Laboratory at MIT.

The researchers say that the constraint of an exoskeleton is that by definition it's bound to the body of the user: no matter what the most advantageous orientation for your limbs might be, the exoskeleton is putting all of its force wherever you decide to put your arms and legs. Having limbs that are powered yet completely separate gives the system many more option for helping you out.



SOURCE  IEEE Spectrum

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