76Service Manual – CS7010™
20 - Wheel System, Traction
Functional Description
A single rear wheel provides both traction
drive and steering. The major components of
the drive wheel system are the drive pedal,
drive controller, drive wheel motor, gearbox
and drive wheel. The drive wheel is mounted
to a gearbox which carries the vehicle load,
provides gear reduction and converts the
plane of rotation from horizontal to vertical.
The gearbox is driven by a brush-less, three
phase, remotely commutated motor. A drive
controller directly operates the drive motor
based on input requests from a drive pedal
sensor (potentiometer) which is mounted on the
side of the drive pedal. If you push the pedal
forward, the machine will move forward. If
you push it farther forward, the machine will
increase speed. If you push the pedal backward,
the machine will move in reverse. The drive
pedal is spring loaded in the center or “neutral”
position.
Drive Motor
The drive motor is a 3-phase, remotely commutated, AC induction motor; which is commonly referred to as
a brushless DC motor. Even though it is an AC motor, it is powered from a controlled DC power source that
simulates AC power. Each of the 3 motor windings is sequentially energized with either zero-volts, positive
battery voltage, or inverted battery voltage. This creates a rotating magnetic eld in the windings just like a
normal 3-phase AC motor.
Unlike a normal AC motor that just receives blind
AC power at a given frequency, the drive motor
functions as a servo-motor, in that the motor
provides positional feedback back to the motor driver
for the actual rotor position. This is referred to as
remotely commutated. Two encoders inside the motor
report the actual rotational position of the rotor back
to the controller. This permits the driver to know
which of the 3 windings needs to be energized to
rotate the motor in the desired direction, and even
position. This type of motor can literally be rotated a
fraction of a turn and stopped, if desired.
The motor also reports its operational temperature
back to the motor driver. This is a protection feature
to prevent motor damage due to excessive heat. The drive controller can either reduce power to the motor, or
if severe enough, shut down the motor.
Drive Pedal
InMotion Drive Controller
Drive Wheel Motor
Gearbox and Drive Wheel
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