Jlg 1350SJP Service Manual User Manual Page 309

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SECTION 4 - BOOM & PLATFORM
3121142 – JLG Lift – 4-75
PLATFORM VALVES
The platform specific valves are located in a manifold at the
platform.
There are individual proportional control valves that control
each of the four platform functions; Platform Level, Platform
Rotate, Jib Lift, and Jib Swing.
There is also a Platform Dump Valve, located in the platform
valve manifold, which is used to hydraulically isolate the con-
trol valves and to improve hydraulic response.
The Ground Module controls this valve to provide manual
platform leveling in the event that the Platform Module is
inoperable.
In ground mode, the platform dump valve is turned on when-
ever any platform or jib valve output is turned on. Whenever
all platform and jib valves are turned off, the platform dump
valve is turned off.
In platform mode, the platform dump valve is turned on
whenever the footswitch is depressed.
Normal Operation
AUTOMATIC LEVELING
Two tilt sensors, mounted on either side of the platform sup-
port, are used to measure the incline of the platform with
respect to gravity and control the automatic leveling function,
one is used as the primary sensor and one as a secondary back
up sensor.
The level system shall assume a new fixed set point (fixed
incline of the platform with respect to gravity) each time the
control system is powered up (cycling of the EMS).
Automatic platform leveling only functions while operating
drive, telescope, lift or swing. It does not operate while operat-
ing any other function (e.g. rotate, jib, or steer).
The proportional control for these valves varies. This is depen-
dant on the tilt variance from target as well as on the impact
coil temperature is having on the current to the valves.
If a command from the Platform Level Up and Down toggle
switch on either the platform or the ground is received, auto-
matic platform leveling will cease and the appropriate output
will be commanded to turn on.
When the toggle switch is released, after ¼ second, the current
filtered value of tilt angle will be taken as the new set point.
In order to obtain acceptable performance while performing
all hydraulic functions, five sets of parameters are used. These
“zones” allow compensation for differences in how the basket
level changes when doing different functions. These zones are
as follows:
1. Lift up
2. Lift down
3. Other boom functions
4. Drive
5. Auxiliary
The other boom functions zone includes Swing, Telescope, Jib
swing (It is not necessary to level with jib lift, since the
mechanical linkage keeps the basket level).
These zones are prioritized when multiple functions are active.
The priorities are as follows.
1. Auxiliary power and any other function, zone = auxiliary
power
2. Drive and any other function, zone = Drive
3. Lift up and any other function, zone = Lift up
4. Lift down and any other function, zone = Lift down
5. Other boom functions, zone = Other boom functions
During the power-up procedure, function enable, in both Plat-
form and Ground Mode, is delayed during the 1.5 second
startup lamp test. During this 1.5 second startup period, the
basket level up valve will be energized at 100% duty cycle for
0.5 second, and then the basket level down valve energized at
100% duty cycle for 0.5 second. This will help to keep the
valves from sticking.
PLATFORM LEVEL MANUAL OVERRIDE
In addition to automatic leveling the operator is able to manu-
ally adjust the platform level position by means of the level
override switches located at the platform and ground control
positions (similar to a Master/Slave hydraulic system).
The level system assumes a new set point after a level over-
ride switch is operated. In other words the operator can chose
a platform level incline other than level with gravity and the
system will maintain this set point during automatic leveling.
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