Engineers are currently working on developing a two-legged, humanoid robot that is capable of exerting force and pushing against something while keeping its balance. A team at MIT and the University of Illinois at Urbana-Champaign have successfully found a way to control the balance in a teleoperated robot. This will play a critical role in getting humanoids to complete high-impact tasks in difficult environments.
The robot that was created by the team has a “machined torso and two legs.” They can control the robot remotely through a human that wears a vest transmitting information regarding the human’s motion and ground reaction forces.
The human operator is able to control the robot’s locomotion, and the vest also allows the human to feel the robot’s motions. For example, the human will feel a pull on the vest if the robot begins to fall over or lose its balance. This allows the human to readjust and steady the robot.
In the experiments and tests that were carried out, the humans were able to successfully hold the robot’s balance, even as it jumped and walked in place with the human.
Joao Ramos, an MIT postdoc, developed the new approach.
“It's like running with a heavy backpack — you can feel how the dynamics of the backpack move around you, and you can compensate properly,” he says. “Now if you want to open a heavy door, the human can command the robot to throw its body at the door and push it open, without losing balance.”
Ramos is currently an assistant professor at the University of Illinois at Urbana-Champaign, and he published the study in Science Robotics. Sangbae Kim, associate professor of mechanical engineering at MIT, is the co-author on the study.
The research was also partly supported by Hon Hai Precision Industry Co, Ltd. and Naver Labs Corporation.
Kim and Ramos previously developed the two-legged robot HERMES (for Highly Efficient Robotic Mechanisms and Electromechanical System), and they also worked on methods that made it capable of mimicking an operator via teleoperation. According to the researchers, this way of operation has humanistic advantages.
“Because you have a person who can learn and adapt on the fly, a robot can perform motions that it's never practiced before [via teleoperation],” Ramos says.
HERMES was able to do certain actions such as pouring coffee into a cup, chopping wood with an ax, and using an extinguisher to put out a fire. These actions require the use of the robot’s upper body, and the algorithms match the robot’s limb positioning with the operator’s. The only reason HERMES was able to perform high-impact actions was because it was set in place, which makes it much easier to maintain balance. Taking any steps would have likely resulted in the robot falling over.
“We realized in order to generate high forces or move heavy objects, just copying motions wouldn't be enough, because the robot would fall easily,” Kim says. “We needed to copy the operator's dynamic balance.”
The team developed Little HERMES, which is a miniature version of the original. The robot is about a third of the size of an average human adult. It was created with a torso and two legs, and it was specifically developed to test actions that rely on the lower-body, including locomotion and balance.
Little HERMES utilizes teleoperation, and the operator wears a vest that is used to control the robot.
Mimicking the human’s motions was one thing, but mimicking the balance is more difficult. The team identified balance as containing two main aspects, a person’s center of mass and their center of pressure.
Ramos found that the balance of a person is determined by the center of mass in relation to the center of pressure.
After condensing the data and developing several models, they began to conduct tests. They eventually found a model to use on Little HERMES.
Little HERMES was able to be controlled through the vest, and Ramos could feel the robot’s motions. One of the tests involved Little HERMES being struck by a hammer, and Ramos felt the vest jerk in the direction that the robot moved. As Ramos resisted the movement, the robot followed, allowing it to keep its balance and avoid falling over.
Kim and Ramos plan to keep working on developing a full-body humanoid. They hope that one day it will be able to operate in a disaster zone, helping aid in rescue missions.
“Now we can do heavy door opening or lifting or throwing heavy objects, with proper balance communication,” Kim says.