Page 81 - Build Your Own Combat Robot

UILDING a robot requires that you make many decisions—from the
type of sensors you’ll use to the color you’ll paint it. Some of these decisions are
trivial, while others will make or break your robot. One decision in the
make-or-break category is motors—not just deciding which ones you’ll use, but
determining how you’ll optimize their performance.
Most robots use the same class of motor—the permanent magnet direct current
(PMDC) motor. These commonly used motors are fairly low in cost and relatively
easy to control. Other types of electric motors are available, such as series-wound
field DC motors, stepper motors, and alternating current (AC) motors, but this
book will discuss only PMDC -type motors. If you want to learn more about other
types of motors, consult your local library or the Internet for that information.
Some combat robots use internal combustion motors, but they are more com-
monly used to power weapons than to drive the robots, largely because the inter-
nal combustion engine rotates only in one direction. If you are using an internal
combustion engine to drive the robot, your robot will require a transmission that
can switch into reverse or use a hydraulic motor drive system. With electric mo-
tors, however, the direction of the robot can be reversed without a transmission.
Many combat robots combine the two, using electric motors for driving the robot
system and internal combustion motors for driving the weapons. Another use for
internal combustion engines is to drive a hydraulic pump that drives the robot
and/or operates the weapons.
Since most robots use PMDC motors, most of the discussion in this chapter
will be focused on electric motors. At the end of this chapter is a short discussion
of internal combustion engines.

E lectric Motor Basics

Because the robot’s speed, pushing capability, and power requirements are di-
rectly related to the motor performance, one of the most important things to un-
derstand as you design your new robot is how the motors will perform. In most
robot designs, the motors place the greatest constraints on the design.

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