Allen was a

robot A robot is a machine—especially one Computer program, programmable by a computer—capable of carrying out a complex series of actions Automation, automatically. A robot can be guided by an external control device, or the robot control, co ...

introduced by

Rodney Brooks Rodney Allen Brooks (born 30 December 1954) is an Australian robotics, roboticist, Fellow of the Australian Academy of Science, author, and robotics entrepreneur, most known for popularizing the behavior based robotics, actionist approach to ro ...

and his team in the late 1980s, and was their first robot based on

subsumption architecture Subsumption architecture is a reactive robotic architecture heavily associated with behavior-based robotics which was very popular in the 1980s and 90s. The term was introduced by Rodney Brooks and colleagues in 1986.Brooks, R. A., "A Robust Pro ...

. It had

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects o ...

distance and

odometry Odometry is the use of data from motion sensors to estimate change in position over time. It is used in robotics by some legged or wheeled robots to estimate their position relative to a starting location. This method is sensitive to errors due ...

on board, and used an offboard lisp machine to simulate subsumption architecture. It resembled a footstool on wheels. Allen used three layers of control which are implemented in subsumption architecture. "The lowest layer of control makes sure that the robot does not come into contact with other objects." Due to this layer it could avoid static and dynamic obstacles, but it could not move. It sat in the middle of the room, waiting for obstruction. When the obstruction came, Allen ran away, avoiding collisions as it went. It used following internal representation, and every sonar return represented a repulsive force with, and inverse square drop off in strength. Direction of its move was obtained by sum of the repulsive forces (suitably thresholded). It possessed an additional reflex which halted it whenever it was moving forward, and something was directly in its path. "The first level layer of control (second layer), when combined with zeroth, imbues the robot with the ability to wander around aimlessly without hitting obstacles." Owing to the second layer, Allen could randomly wander about every 10 seconds. It used simple

heuristic A heuristic or heuristic technique (''problem solving'', '' mental shortcut'', ''rule of thumb'') is any approach to problem solving that employs a pragmatic method that is not fully optimized, perfected, or rationalized, but is nevertheless ...

, which was coupled with the instinct to shun barriers by

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

addition. "The summed vector suppressed the more primitive obstacle avoidance vector, but the obstacle avoidance behaviour still operated, having been subsumed by the new layer, in its account of the lower level's repulsive force. Additionally, the halt reflex of the lower level operated autonomously and unchanged." The third layer made the robot try to explore. Allen could look for distant places (with its sonars), then tried to reach them. "This layer monitored progress through odometry, generating a desired heading which suppressed the direction desired by the wander layer. The desired heading was then fed into a vector addition with the instinctive obstacle avoidance layer. The physical robot did not therefore remain true to the desires of the upper layer. The upper layer had to watch what happened in the world, through odometry, in order to understand what was really happening in the lower control layers, and send down correction signals."

References

{{reflist Historical robots Robots of the United States 1980s robots

See also

References