Oshkosh JLG 1500SJ, Руководство по обслуживанию и ремонту

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SECTION 3 - CHASSIS & TURNTABLE
3121262 – JLG Lift – 3-3
3.4 DRIVE SYSTEM
The drive system utilizes 2 traction pumps so each side is pow-
ered 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 driving at full speed and maxi-
mum 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 auto-
matically 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 control
panel: conventional two wheel steering, crab and coordinated.
These are shown below.
Each wheel has its own steer cylinder, wheel angle sensor, 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 initi-
ated. The steering angles are limited to +/- 25 degrees anytime
the axles are not fully extended. If a wheel cannot achieve its
commanded 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 foot-
switch is cycled. If a wheel is jammed making 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 approxi-
mated 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 prohibitively out of position, the wheels can be re
synchronized by fully steering against the mechanical stops.
NOTE: For more detailed information concerning system adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
Figure 3-2. Conventional Two Wheel Steer Mode
Figure 3-3. Crab Steer Mode
Figure 3-4. Coordinated Steer Mode