Teaching robots lateral thinking: New algorithms could help household robots work around their physical shortcomings

February 25, 2013 by Larry Hardesty

Many commercial robotic arms perform what roboticists call "pick and place" tasks: The arm picks up an object in one location and places it in another. Usually, the objects—say, automobile components along an assembly line—are positioned so that the arm can easily grasp them; the appendage that does the grasping may even be tailored to the objects' shape.

General-purpose household robots, however, would have to be able to manipulate objects of any shape, left in any location. And today, commercially available robots don't have anything like the of the human hand.

At this year's IEEE International Conference on Robotics and Automation, students in the Learning and Intelligent Systems Group at MIT's Computer Science and Artificial Intelligence Laboratory will present a pair of papers showing how household robots could use a little lateral thinking to compensate for their physical shortcomings.

One of the papers concentrates on picking, the other on placing. Jennifer Barry, a in the group, describes an algorithm that enables a to push an object across a table so that part of it hangs off the edge, where it can be grasped. Annie Holladay, an MIT senior majoring in electrical engineering and computer science, shows how a two-armed robot can use one of its graspers to steady an object set in place by the other.

Colliding approaches

Most experimental general-purpose robots use a motion-planning algorithm called the rapidly exploring random tree, which maps out a limited number of -free through the robot's environment—rather like a subway map overlaid on the map of a city. A sophisticated-enough robot might have arms with seven different joints; if the robot is also mounted on a mobile base—as was the Willow Garage that the MIT researchers used—then checking for collisions could mean searching a 10-.

Add in a three-dimensional object with three different axes of orientation, which the robot has to push across a table, and the size of the search space swells to 16 dimensions, which is too large to search efficiently. Barry's first step was to find a concise way to represent the physical properties of the object to be pushed—how it would respond to different forces applied from different directions. Armed with that description, she could characterize a much smaller space of motions that would propel the object in useful directions. "This allows us to focus the search on interesting parts of the space rather than simply flailing around in 16 dimensions," she says. Finally, after her modification of the motion-planning algorithm, she had to "make sure that the theoretical guarantees of the planner still hold," she says.

The video will load shortly

By contrast, Holladay's algorithm in some sense inverts the ordinary motion-planning task. Rather than identifying paths that avoid collisions and adhering to them, it identifies paths that introduce collisions and seals them off. If the robot is using one hand to set down an object that's prone to tipping over, for instance, "I might look for a place for the other hand that will block bad paths and kind of funnel the object into the path that I want," Holladay says.

Like Barry, Holladay had to find a simple method of representing the physical properties of the object the robot is manipulating. In addition to the placement of tall, tippy objects, her algorithm can also handle cases in which the robot is setting an object on a table, but the object sticks to the rubber sheath of the robot's gripper. With Holladay's algorithm, the robot can use its free gripper to prevent the object from sliding as it withdraws the other gripper.

Independent learning

Both Barry and Holladay allow modification of their algorithms, through application programming interfaces that would allow other researchers to plug in parameters describing the physical behavior of new types of objects. But the ultimate goal is for the robot itself to infer the relevant properties of objects by lifting, shoving, or otherwise manipulating them.

Nor are the researchers concerned that hardware improvements will render their algorithmic research obsolete. "The thought is that we're unlikely to get hands that are as flexible and dexterous as human hands, and even if we did, it would be hard to figure out the AI and planning for those," Barry says. "So we'll always have to think about interesting ways to grasp things."

"You see a lot of demos where a robot might do something like slide plates, but it's usually hard-coded for the demo: The robot knows that at this point, it needs to do this action for this particular thing," says Kaijen Hsiao, a research scientist and manager at Willow Garage, the company that manufactures the PR2. Barry and Holladay's research, by contrast, is "a framework for incorporating behaviors like that as a more general motion-planning problem," she says. "Which is a very difficult thing, because it's very high-dimensional. I think it's really important research, and it's very novel."

Explore further: Robots learn to pick up oddly shaped objects

Related Stories

Robots learn to pick up oddly shaped objects

May 9, 2012

(Phys.org) -- When Cornell engineers developed a new type of robot hand that could pick up oddly shaped objects it presented a challenge: It was easy for a human operator to choose the best place to take hold of an object, ...

Smarter robot arms (w/ video)

September 22, 2011

(PhysOrg.com) -- A combination of two algorithms developed at MIT allows autonomous robots to execute tasks much more efficiently — and move more predictably.

Robots could improve everyday life, do chores

September 21, 2010

(PhysOrg.com) -- They're mundane, yet daunting tasks: Tidying a messy room. Assembling a bookshelf from a kit of parts. Fetching a hairbrush for someone who can't do it herself. What if a robot could do it for you?

Harvard researchers develop new kind of soft robotic gripper

September 11, 2012

(Phys.org)—Because traditional robot hands or grippers were first created to assist in production type enterprises, e.g. to help build cars, etc., they have not been very good at working with soft materials. For that reason, ...

Robot Rebuilt gets a grip on wine-serving robot (w/ video)

December 5, 2012

(Phys.org)—Robot research has its own unique show of hands as scientists focus on improving human-like abilities of grasping, pushing, and manipulating objects. Grabbing current attention is an assistant professor at Worcester ...

Recommended for you

Samsung to disable Note 7 phones in recall effort

December 9, 2016

Samsung announced Friday it would disable its Galaxy Note 7 smartphones in the US market to force remaining owners to stop using the devices, which were recalled for safety reasons.

Swiss unveil stratospheric solar plane

December 7, 2016

Just months after two Swiss pilots completed a historic round-the-world trip in a Sun-powered plane, another Swiss adventurer on Wednesday unveiled a solar plane aimed at reaching the stratosphere.

Solar panels repay their energy 'debt': study

December 6, 2016

The climate-friendly electricity generated by solar panels in the past 40 years has all but cancelled out the polluting energy used to produce them, a study said Tuesday.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

rwinners
not rated yet Feb 26, 2013
It's a start. But I can not guess how long it will be before a human being leaves an anderoid alone in a room with a small child.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.