Jul 8, 2018

Without eyes, MIT's Cheetah robot moves by feel

MIT's Cheetah 3 robot. GIF via MIT video

In a turn away from vision, a team at MIT has created a feline robot that attempts to better approximate how humans and animals actually move, navigating stairs and uneven surfaces guided only by sensors on its feet.

Why it matters: Many ambulatory robots rely on substantial recent improvements in computer-vision, like advanced cameras and lidar. But robots will be more nimble and more practically interact with humans with the addition of "blind" vision — a sixth sense of feeling that most living things have for their surroundings.

What's going on: Computer vision alone can result in a robot with slow and inaccurate movements, says MIT's Sangbae Kim, designer of the Cheetah 3.

  • "People start adding vision prematurely and they rely on it too much," Kim tells Axios, when it's best suited for big-picture planning, like registering where a stairway begins and knowing when to turn to avoid a wall. So his team built a "blind" version in order to focus on tactile sensing.

How the blind version works: Two algorithms help the Cheetah stay upright when it encounters unexpected obstacles.

  • One determines when the bot plants its feet, by calculating how far a leg has swung, how much force the leg is feeling, and where the ground is.
  • The other governs how much force the robot should apply to each leg to keep its balance, based on the angle of the robot's body relative to the ground.
  • The sensors can also adjust to external forces, like a researcher's friendly kick from the side.

The result is a quick, balanced robot: The researchers measure the force on each of the Cheetah's legs straight from the motors that control them, allowing it to move fast — at 3 meters per second, or 6.7 miles an hour — and jump up onto a table from a standstill. These tricks make the 90-pound bot look surprisingly nimble.

Cheetah's design emphasizes "sensors that you and I take for granted," said Noah Cowan, director of the LIMBS robotics lab at Johns Hopkins University.

  • Humans unconsciously keep track of where their arms and legs are — and the forces acting on them — to help stay balanced and move smoothly. MIT’s Cheetah “feels” its legs in a similar way.

The Cheetah's capabilities resemble some of the robots produced by the ever-secretive Boston Dynamics, which in May released a video of its four-legged SpotMini navigating autonomously through its lab with the help of cameras.

  • It's not clear whether Boston Dynamic robots use tactile technology like Kim's, and the company did not respond to an email.

Vision will probably always play a role in walking robots, even if tactile sensing becomes commonplace. Velodyne, the most prominent lidar manufacturer — and a supplier for Boston Dynamics — says its technology can see further than three football fields in day or night, collecting 8 million datapoints every second from all directions. "The sensor also scans in a full 360 degrees which is impossible for a human to do," Frank Bertini, Velodyne's UAV and robotics business manager, tells Axios.

  • Kim's team plans to add cameras back onto the Cheetah in order to help it get around complex environments.
  • They also want to add a grasping arm that a human can control from afar.
  • The resulting bot could be well-suited for rescue operations or doing dangerous inspections in human-unfriendly environments.

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