JLG 1100SB Service Manual - Manual (Page 45)

SECTION 3 - CHASSIS & TURNTABLE
3121265 – JLG Lift – 3-3
3.4 DRIVE SYSTEM
The drive system utilizes 2 traction pumps so each side is
powered individually. This produces maximum tractive
effort to wheels by minimizing flow divider losses. The
maximum drive speed is modulated with the steered
angle of the wheels to eliminate the whiplash effect of driv-
ing at full speed and maximum steering lock.
3.5 STEERING CONTROL SYSTEM
Each wheel is individually steered by means of a closed
circuit control system utilizing a steer sensor on each
wheel, 4 steer cylinders, and proportional valves.
The control system senses the wheel position in relation
to the steering command (direction and steering mode)
and automatically synchronizes the movement of all 4
wheels to the desired position.
There are three different modes of steering selectable by
the position of the steer select switch on the platform con-
trol panel: conventional two wheel steering, crab and
coordinated. These are shown below.
Each wheel has its own steer cylinder, wheel angle sen-
sor, and proportional valve, allowing the control system to
position each wheel to the ideal angle for all steering
modes and all steering commands. Changes in steering
modes while the footswitch is depressed causes the
wheels to automatically adjust to the appropriate angle for
the selected steering mode based on the position of the
inside front wheel. If the steer select switch is changed
without the footswitch depressed or the EMS is off, the
wheels will not move until the footswitch is depressed and
a steering or drive command has been initiated. The steer-
ing angles are limited to +/- 25 degrees anytime the axles
are not fully extended. If a wheel cannot achieve its com-
manded angle within a specified time, it is considered
jammed. When a wheel is considered jammed during
steering, a fault is reported and the remaining wheels will
continue to their commanded position. The fault is cleared
when the footswitch is cycled. If a wheel is jammed mak-
ing it significantly out of position, with regard to the other
wheels, the drive motors are restricted to their maximum
displacement (slow speed). 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 available from the other sensors.
This wheel will not track perfectly and will become farther
out of position over time. When the wheel becomes pro-
hibitively out of position, the wheels can be re synchro-
nized by fully steering against the mechanical stops.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
Figure 3-2. Conventional Two Wheel Steer Mode
Figure 3-3. Crab Steer Mode
Figure 3-4. Coordinated Steer Mode