TGB EST 1000, Service Manual

Page: 219 / 269

7-2. ELECTRIC POWER STEERING
7-2-3
The internal protection system decreases the
assistance level available to protect its
electronic board. The normal assistance level
will return when riding conditions are back to
normal and the internal temperature decrease
and/or when the ripples in the electric circuit
decrease.
NOTE: This reaction is a normal protective
behavior of the unit and it does not necessary
raise a fault in the cluster.
EPS SYSTEM DESCRIPTION
EPS Unit
The EPS unit is a self contained unit that
includes the steering gear, the EPS module, the
EPS motor and the torque sensor.
The EPS module provides DC power to the
motor. The amount and duration of that DC
power is determined by the inputs to the EPS
module. The direction in which the motor turns
is changed by reversing the polarity of the
circuit current.
The EPS motor does not
“
spin
”
, but rather turns
in very small increments based on the amount,
duration, and direction of DC power delivered
by the EPS module.
EPS Unit protection
When the EPS unit temperature is above 100
℃
, all the EPS function will stop but the steering
can operate without power assist, when the
EPS internal board temperature decrease
below 90
℃
, the power steering will back to
normal and steering assist should resume
normal operation.
Steering Torque Sensor
The steering column is connected to the shaft
on the EPS unit. A small area of the EPS shaft
is magnetized. Inside the EPS unit, a torque
sensor surrounds the magnetized area of the
EPS shaft.
When the handlebar is turned, torque is applied
to the shaft, which tends to twist the shaft
slightly, deforming the magnetic field in the
shaft. The sensor detects the torque by
measuring the deviation of the magnetic field.
The torque sensor is very sensitive and can
detect very small changes in the magnetic field.
The harder the handlebar is turned, the greater
the magnetic deviation, the greater the power
steering assist.
EPS Mode
The EPS system normally provides two rider
selectable modes of operation.
MAX provides maximum steering assist for
technical low speed riding in rough or
muddy terrain or for touring.
MIN provides less steering assist for increased
feedback and aggressive trail riding.