Overview

The hug primitive makes the robot move forward while staying a desired distance from objects off to the side, such as walls.  The robot uses a closed-loop proportional control loop to "hug" or stay close to the wall.  The nominal hug distance is between 15cm and 35cm (6 to 14 inches).  Prior to calling this primitive, the robot must be lined up with its wheels nearly parallel to a wall and close to the desired hug distance.  If the robot is too far from the wall, it may turn sharply towards the wall and stop with a front ranger detection.  If the robot tries to hug a wall and none is within range, it may go in circles.  The monitor keeps track of obstructions, edges, stalls, and other boundary conditions.  The current speed setting for the robot is used for the motion and velocity damping is used to create a fluid movement.

The robot always checks for front obstacles when wall-hugging.  Depending on the wall-hug mode, the robot may also check for sudden changes from the side ranger being used for the hug.  Thresholds for front and rear obstacle detection may be adjusted by modifying the front-ranger-threshold and side-ranger-threshold properties of the Garcia object.  These properties may also be set within an XML script by using a global primitive.

Defined values that may be used as hug parameters can be found in the aGarciaDefs.tea file in the aSystem subfolder of the brainstem directory tree.

Return Status

This primitive returns the condition that terminated the motion.

Property Inheritance

hug inherits Behavior inherits Object properties.