JLG 1250AJP Service Manual - Manual (Page 53)

SECTION 3 - 1CHASSIS & TURNTABLE
3121171 – JLG Lift – 3-5
Wheel angle sensor failures will result in an approximated
steering control logic that will allow the operator to move
the machine until it can be repaired. The wheel at the
failed sensor will be driven based on the information avail-
able from the other sensors. This wheel will not track per-
fectly and will become farther out of position over time.
When the wheel becomes prohibitively out of position, the
wheels can be resynchronized by fully steering against
the mechanical stops.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
3.6 DRIVE/STEERING SPEED CONTROL
The Drive/Steering Speed Control system uses the steer-
ing sensors from the steering control system (see Section
3.5, Steering Control System) to increase operator control
and comfort by reducing the effect of turning the chassis
and the resulting lateral platform speed. The system pro-
portionally varies the drive speed based on the predicted
turning radius of the chassis for both coordinated and
conventional two wheel steer modes. The tighter the turn
the slower the allowable drive speed. As crab steer does
not steer on a radius, full drive speed is maintained
regardless of steer angle.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
3.7 TRACTION CONTROL SYSTEM
The Traction Control System uses the steering sensors
from the steering control system (see Section 3.5, Steer-
ing Control System) to optimize the performance of the
drive system. This is especially important due to the dis-
parity of wheel speeds generated between the inside and
outside wheels of the extended axle chassis with large
steering angle capability.
The steering sensors are used to predict the rolling path
and therefore the required wheel speed of each wheel as
the steering angles change and steering modes change.
The control system can then command the ideal flow from
each of the two drive pumps, one for the right side of the
machine and one for he left side. Two flow dividers, one
for the right side front to back and one for the left side
front to back absorb the variation in wheel speed front to
back.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
3.8 DRIVE ORIENTATION SYSTEM
The Drive Orientation System (DOS) is intended to indi-
cate to the operator conditions that could make the direc-
tion of movement of the chassis different than the
direction of movement of the drive/steer control handle.
The system indicates to the operator the need to match
the black and white directional arrows on the platform
control panel to the arrows on the chassis. The system
uses a proximity switch mounted on the hydraulic swivel,
an indicator light, and a spring return override switch on
the platform display panel. The proximity switch trips
when the turntable is swung ± 45 degrees off center of
the normal driving position. This occurs roughly when the
main boom is swung past a rear tire. When the turntable is
in the normal drive position with the boom between the
rear tires, no indications or interlocks are made. When the
machine is actively driving when the turntable is swung
past the switch point, the system is ignored until drive/
steer is released. When drive is initiated with the boom
swung past the switch point, the DOS indicator will flash
and the drive/steer functions will be disabled. The opera-
tor must engage the DOS override switch to enable Drive/
steer (high drive will remain disabled). When the DOS is
enabled, the DOS indicator will be illuminated continu-
ously and a 3-second enable timer will be started and will
continue for 3 seconds after the end the last drive/steer
command. If the timer expires, the DOS override switch
must be re-engaged to enable drive/steer.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
3.9 GROUND CONTROL ENABLE SYSTEM
The ground controls include the use of a function enable
system for the operation of directional functions from the
ground control panel. To operate any directional function,
the function enable switch must be held in combination
with the directional function switch. This switch doubles as
the auxiliary power switch. When the engine is not run-
ning, activating this switch will operate auxiliary power.
When the engine in running, activating this switch will
enable directional functions. Releasing this switch during
function commands will stop the function movement.
Unlike the platform enable, no timer or sequence logic is
imposed on the use of the function enable.