In the design and implementation of drive trains and propulsion systems,
a team must consider the appropriate speed for the output shaft of
the gear box or transmission. Many teams advocate for a robot that
travels between three and five miles per hour.
FIRST teams have also designed and implemented a number of drive train
and propulsion systems that include a linear or tank drive, crab drive,
and the holonomic drive system.
Determining
Drive Trains
Linear Drive Systems
Linear drive is the most common propulsion system seen in the FIRST
community, although the driven wheels or tracks vary considerably.
Tank drives are the easiest to build, assembly, maintain, and test
among the current drive systems. With the addition of a shifting
transmission a form of a linear drive proves to be a fearsome competitor.
Shifting transmissions:
Team
716 Dual Speed Gearbox
Team
33 Shifting Gearbox
Team
900 Shifting Transmission
Andy Mark's Shifting
Transmissions
Holonomic Drive
There are several forms of holonomic drive systems currently being
implemented and devised. Holonomic drives serve to minimize all counteracting
forces by creating a near frictionless object. The most popular are
the omni, ball driven designs. Omni-drive system utilizes a series
of wheels placed into a single rotating wheel perpendicular to the
main axis or rotation. Similarly the ball design uses a series of
small motors to drive a ball at which the robot is positioned on.
These systems maximize mobility; however in doing maximizing mobility
they minimize the traction that the robot has to push an opponent.
Crab Drive
Crab Drives are one of the more common holonomic drive systems currently
in use with FIRST teams although not as popular as the linear drive
system. Team 79 white paper concerning crab
drives best explains the advantages and disadvantages of
this propulsion system.
