Trimble FM-1000 - Page 179

8 Vehicle guidance setup Autopilot system
Proportional steering gaincalibration
WARNING – The wheels can move abruptly during the Proportional Steering Gain procedure while the Autopilot
system tests the hydraulic response to the steering commands. These sudden movements can cause collisions
with nearby obstacles or cause injury to occupants of the vehicle. Be prepared for sudden wheel movements.
Note – Complete the steering sensor calibration before you perform the proportional gain calibration.
Perform the proportional steering gain calibration only when the Autopilot system performance is less than
satisfactory.
The Proportional Steering Gain (PGain) setting enables a balance between rapid steering response
and stability. When you modify the PGain setting, two steering characteristics are affected:
l Slew Time: The amount of time that the front wheels take to move from the far left to the far
right position and vice versa.
l Overshoot: The percentage by which the front wheels exceed the commanded angle before
they settle on the correct value.
To correct slight variations caused by valve current response, friction, and hydraulic fluid viscosity,
alter the PGain value:
l High PGain value: Decreases the slew time and increase the overshoot. This provides rapid
responses, but can cause the steering to exhibit signs of instability (for example, a tendency to
excessively overshoot).
l LowPGain value: Increases the slew time and decrease the overshoot. This improves the
stability but can introduce significant delays in the steering response and can cause the vehicle
to oscillate from side to side.
Perform the calibration:
l Immediately before you run the PGain calibration, even if the Automatic Deadzone calibration
has been performed in the past.
l On a hard, level surface that is free of obstructions.
l While maintaining a vehicle speed above 1.6 kph (1 mph)
Increase the proportional gain up to the point just before any one of the following occurs:
l Slew times no longer decrease (a low value is required)
l Overshoot exceeds 5 – 8% (depending on the vehicle)
l Wheels noticeably shake near end stops
Version 9.25, Revision B FM-1000 Integrated Display User Guide 179