Oshkosh JLG 1500SJ, Service And Maintenance Manual, Page: 54 / 706

SECTION 3 - CHASSIS & TURNTABLE
3-4 – JLG Lift – 3121262
3.6 DRIVE/STEERING SPEED CONTROL
The Drive/Steering Speed Control system uses the steering
sensors from the steering control system to increase operator
control and comfort by reducing the effect of turning the
chassis on the resulting lateral platform speed. The system
proportionally varies the drive speed based on the predicted
turning radius of the chassis for both coordinated and conven-
tional 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 adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
3.7 TRACTION CONTROL SYSTEM
The traction control system uses the steering sensors from the
steering control system to optimize the performance of the
drive system. This is especially important due to the disparity
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 adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
3.8 DRIVE ORIENTATION SYSTEM
The Drive Orientation System (DOS) is intended to indicate to
the operator conditions that could make the direction of
movement of the chassis different than the direction of move-
ment of the drive/steer control handle. The system indicates to
the operator the need to match the black and white direc-
tional 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 an override switch
on the platform display panel. The proximity switch trips when
the turntable is swung +/- 40 degrees off center of the normal
driving position. This occurs roughly when the boom is swung
past a rear tire. When the turntable is in the normal drive posi-
tion 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
operator 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 continuously
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.
Swing Envelope Service Mode
NOTE: If the axles are in the retracted position, boom swing is
restricted to between the rear wheels (40 degrees).
The Swing Envelope Service Mode is used if the boom is
swung past the rear tires with the axles retracted, there is a dis-
agreement fault between the DOS proximity switch and the
turntable angle sensors, or there is a failed turntable angle
sensor. (Drive and swing are disabled during these events.)
This allows swing and drive functions to enable turntable
swing in the correct direction to return the boom between the
rear wheels in the event the boom is beyond the swing enve-
lope when the axles are retracted.
Swing Envelope override is accessible in Access Level 1. Using
the Left and Right arrow keys until the screen
shown below is reached.