Watch This Robot Control a Person's Arm Using Electrodes

When this robot needs a hand, it borrows yours

3 min read

Erico Guizzo is IEEE Spectrum's Digital Innovation Director.

Watch This Robot Control a Person's Arm Using Electrodes

robot control human arm

When this robot needs a hand, it borrows yours.

In an experiment that opens a new chapter in human-machine interaction, a French research team has demonstrated how a robot can control both its own arm and a person’s arm to manipulate objects in a collaborative manner.

The robot controls the human limb by sending small electrical currents to electrodes taped to the person's forearm and biceps, which allows it to command the elbow and hand to move. In the experiment, the person holds a ball, and the robot a hoop; the robot, a small humanoid, has to coordinate the movement of both arms to successfully drop the ball through the hoop.

The researchers, from the Montpellier Laboratory of Informatics, Robotics, and Microelectronics (known by its French acronym LIRMM), say the approach is still in the proof-of-concept stage, but they are confident that performing more complex tasks is possible. Their goal is to develop robotic technologies that can help people suffering from paralysis and other disabilities to regain some of their motor skills.

To be sure, an advanced, dexterous robot arm would be capable of assisting paralyzed people with daily tasks. And other technologies such as robot teleoperation, brain-machine interfaces, and powered exoskeletons also promise to give physically disabled people more mobility.

But Adorno and his colleagues say there are advantages in having a robot controlling a person's body. The technique they're using to do that, known as functional electrical stimulation (FES), is used in rehabilitation and has physical and psychological benefits to patients.

"Imagine a robot that brings a glass of water to a person with limited movements," says Bruno Vilhena Adorno, the study's lead researcher. "From a medical point of view, you might want to encourage the person to move more, and that's when the robot can help, by moving the person's arm to reach and hold the glass."

Another advantage, he adds, is that capable robotic arms are still big, heavy, and expensive. By relying on a person's physical abilities, robotic arms designed to assist people can have their complexity and cost reduced. Many research teams are teaching robots how to perform bimanual manipulations, and Adorno says it seemed like a natural step to bring human arms into the mix.

Still, if the idea of a robot commandeering your limbs sounds a bit, uh, scary, you're not alone. The audience at the IEEE International Conference on Intelligent Robots and Systems (IROS), where the researchers presented their results in September, let out a nervous gasp upon seeing the video of the experiment:

In the study, Adorno and his colleagues, Antônio Padilha Lanari Bó and Philippe Fraisse, attached four electrodes to the arms of five healthy volunteers test subjects, who were also blindfolded, to avoid visual feedback.

Two electrodes on the forearm controlled the hand, making it open. Two electrodes on the uppear arm controlled the elbow joint, making it move in one direction, towards the torso. In other words, the researchers modeled the human arm as a 1-degree-of-freedom serial robot [image below] and developed a controller to operate it, using FES.

robot controls human arm using electrical stimulation

In each trial, a test subject placed his or her arm on a flat surface and grabbed the ball. Then the robot, a Fujitsu HOAP-3 humanoid, took over, making the elbow move to bring the ball closer to its workspace. The robot also moved its own arm, which had 4 degrees of freedom, to position the hoop right below the ball. Finally, it made the human hand open and drop the ball.

The researchers emphasize that the control of the human arm doesn't have to be precise, just "good enough" to place it inside the robot's workspace. They claim that having a robot able to control a person's arm is better than having a very dexterous robot and a person's weak, unsteady limb.

"Two good-enough agents are better than one very good and one bad in this case," says Adorno, who is Brazilian and will become a professor at the Federal University of Minas Gerais later this year.

He plans to continue the project and adds that they're now improving the electrical stimulation. They're now able to move the elbow in both directions, for example. Eventually they hope to move the arm to any point in space.

The work is part of Project Assist, whose goal is to develop a two-arm mobile robot capable of assisting quadriplegic people to manipulate common objects.

At the end of their presentation at the IROS conference, someone in the audience asked if having an arm controlled by a robot by means of electrical currents applied to the skin hurt.

Adorno said the approach is safe and with some tweaks the stimulation could be made "comfortable" for people. "You get used to it," he said.

Images: Bruno Adorno/LIRMM

The Conversation (1)
Joan O'neill
Joan O'neill13 Nov, 2021

Like to know more about human arm argumentation. I'm an engineer, with nerve damage in arms, need robotic assist.