Shakey

A robot that could work things out

Shakey was a mobile robot developed at SRI International between 1966 and 1972^[1]. SRI describes it as the first mobile robot with the ability to perceive and reason about its surroundings^[2], and as the first AI-based mobile robot to accomplish a task without step-by-step instructions^[1]. The two claims point at the same ambition: a machine that is told what result is wanted, and works out for itself how to get there.

Where it came from

Charles Rosen led the team that developed Shakey from 1966 to 1972^[3], and the project was funded by the U.S. Defense Department^[3]. The robot did not carry its own computing power. It used a two-way radio link to communicate with the large computers that controlled it^[3], so the machine that moved and the machine that thought were in different places. That split was a practical arrangement: the reasoning was done by room-sized computers of the kind available at the time, while the robot carried only what it needed to sense and move.

For sensing, Shakey was equipped with a TV camera, a radio antenna link, detectors and bumpers, which it used to visually interpret its environment^[1]. In other words, it looked at the world through a camera, kept track of what it bumped into, and used that information to build a picture of the room it was standing in.

What it could do

Shakey could perform tasks that required planning, route-finding and the rearranging of simple objects^[2]. A task of that kind combines several hard problems at once: recognising what is in the room, deciding which sequence of moves will lead to the goal, finding a path around obstacles, and then actually carrying the moves out. Solving them together, rather than scripting each motion in advance, is what made the robot a research platform rather than a demonstration.

The software that came out of the project proved more durable than the hardware. The project produced the A* search algorithm, used for planning waypoints around obstacles, and the STRIPS planning system^[3]. A* is a way of searching through possible routes: it keeps track of the best route found so far and uses an estimate of the distance still to go to decide which option to explore next, which usually finds a good route without examining every possibility. STRIPS approached planning differently, by describing each action in terms of what must be true before it can be taken and what becomes true afterwards, so that a planner can chain actions together toward a goal. Both ideas spread far beyond the Shakey project and became standard equipment in later robotics and AI work.

Public attention

Shakey reached a wider audience after a New York Times article of 10 April 1968^[2]. Following that coverage, Life magazine called Shakey the "first electronic person" in 1970^[2]. The phrase says a lot about how the robot was received: not as a laboratory apparatus but as an early character in a story about machines that act on their own.

Place in the history

Shakey matters less for what it could do than for what it established as a pattern. A robot that senses, reasons and acts, with the reasoning handled by general-purpose planning software rather than hard-wired routine, is the shape that later mobile robotics took. The project's two best-known outputs, A* and STRIPS, outlived the machine itself and are still taught as parts of the basic vocabulary of AI planning.

Shakey was elected to Carnegie Mellon University's Robot Hall of Fame in 2004, and it now resides at the Computer History Museum in Mountain View, California^[2].