Page 337 - Concise Encyclopedia of Robotics

Tri-Star Wheel Locomotion
Triangulation need not use laser beams. Instead of the reflecting targets,
beacons can be used. Instead of visible light, radio waves or sound waves
can be used. Beacons eliminate the need for the 360° scanning transmitter
in the robot.
See also BEACON, DIRECTION FINDING, DIRECTION RESOLUTION, LADAR, RADAR, and SONAR.
TRI-STAR WHEEL LOCOMOTION
A unique and versatile method of robot propulsion uses sets of wheels
arranged in triangles. The geometry of the wheel sets has given rise to the
term tri-star wheel locomotion. A robot can have three or more pairs of tri-
star wheel sets. The illustration shows a robot with two sets. (This drawing
shows only one side of the machine. An identical pair of tri-star wheels
exists on the other side, out of sight in this perspective.)
Robot
body
Wheel
Central
bearing

Surface

Tri-star wheel locomotion

Each tri-star set has three wheels. Normally, two of these are in contact
with the surface. If the robot encounters an irregularity in the terrain,
such as a big pothole or a field of rocks, the tri-star set rotates forward on
a central bearing. Then, for a moment, only one of the three wheels is in
contact with the surface. This might happen once or repeatedly, depending
on the nature of the terrain. The rotation of the central bearing is inde-
pendent of the rotation of the wheels.
Tri-star wheel locomotion works well for stair climbing. It can even
allow a robot to propel itself through water, although slowly. The scheme

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