Pololu 0J5840, Руководство пользователя

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A typical small brushed DC
motor, with no gearbox.
A motor is a machine that converts electrical energy to motion.
There are many different kinds of motors, but the most important
for low-cost robotics is the
brushed DC motor , which is the type
used on the 3pi. A brushed DC motor typically has permanent
magnets on the outside and several electromagnetic coils
mounted on the motor shaft (armature). The “brushes” are sliding
pieces of metal that switch the power from one coil to the next as
the shaft turns so that magnetic attraction between the coil and
the magnets continuously pulls the motor in the same direction.
The primary values that describe a running motor are its speed,
measured in rpm, and its torque, measured in kg·cm or oz·in
(pronounced “ounce-inches”). The units for torque show the dependence on both force and distance;
for example, a motor that produces 6 oz·in of torque can product a force of 6 oz. with a 1-inch lever
arm, 3 oz. with a 2-inch lever, and so on. Multiplying the torque and speed (measured at the same
time) give us the power delivered by a motor. We see, therefore, that a motor with twice the speed and
half the torque as another has the same power output.
Every motor has a maximum speed (when no force is applied) and a maximum torque (when the motor
is completely stopped). We call these the
free-running speed and the stall torque . Naturally, a motor
uses the least current when no force is applied to it, and the current drawn from the batteries goes up
until it stalls, so the
free-running current and stall current are also important parameters characterizing
the motor. The stall current is usually much higher than the free-running current, as shown in the graph
below:
Motor operation: current and speed vs. torque.
Pololu 3pi Robot User’s Guide © 2001–2019 Pololu Corporation
5. How Your 3pi Works Page 16 of 85