Service Manual Instruction Manual

SECTION 4 - BOOM & PLATFORM
3121171 – JLG Lift – 4-95
4.29 ELECTRONIC PLATFORM LEVELING
NOTE: For more detailed information concerning system adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
Description
Electronic platform leveling replaces the conventional hydrau-
lic method of platform leveling.
To control electronic platform leveling the platform is
equipped with a pair of tilt sensors, one primary and one sec-
ondary, mounted to the non-rotating portion of the platform
rotator. The tilt sensors are monitored regularly and the plat-
form level up and down valves are automatically controlled to
maintain set point as the machine is operated.
PRIMARY AND SECONDARY TILT SENSOR INTERACTION
The secondary tilt sensor is used as a backup to the primary tilt
sensor. Any time a tilt set point is reset, a value from each sen-
sor shall be set.
If a fault occurs with the primary sensor, control will revert to
the secondary sensor. (This is discussed in more detail in the
error response section.)
Because of the mounting orientation of the tilt sensors, the
primary tilt sensor will output ascending voltage values with
increases in positive platform tilt angle. The backup or second-
ary tilt sensor will output descending voltage values with
increases in positive platform angle.
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.