JLG 1850SJ Service Manual - Manual (Page 88)

SECTION 4 - BOOM & PLATFORM
4-2 – JLG Lift – 3121619
envelope. The two main boom angle sensors measure the
angle of the main boom relative to gravity and are continu-
ously monitored for mutual agreement. The main boom
length sensor measures the length of the main boom and is
monitored for response to main telescope command and for
agreement with the fixed position length switch (Main boom
length transport switch). Violations of the main boom position
to allowable envelope positions will result in reduced function
speeds, BCS warning light illumination, and restriction of func-
tions. The platform alarm will sound and the BCS light will
flash with attempts to operate restricted functions. The
restricted functions due to envelope violations related to for-
ward reach are disallowing main lift down, main telescope out,
swing, drive and steer. The restricted functions due to enve-
lope violations related to backward reach are disallowing main
lift up, main telescope in, swing, drive, and steer. Recognized
failures within this system will result in control by the Moment
Control System, reduced function speeds, and BCS warning
light illumination. The unit will be restricted from leaving the
transport position until the failure is resolved.
Moment Control System
The Moment Control System is the secondary means of con-
trolling the stability of the machine. This system uses a load
cell pin to attach the lift cylinder of the main boom to the turn-
table. This pin is instrumented with gauges allowing the forces
in the pin to be monitored. These forces are used to compare
the actual boom moment (force at a distance) to a predeter-
mined allowable boom moment. In controlling the boom
moment, the position and load of the boom is controlled. The
moment control system will detect moments larger than
expected as well as those smaller than expected. This effec-
tively controls the forward and rearward positions of the
boom. The moment control system varies the maximum
allowable moment based on ground slope. On level ground
and with rated load in the platform, the allowable moments
establish a working envelope slightly larger than the Envelope
Control System's envelope to minimize interaction of the sys-
tems. With increasing ground slopes and rated load in the
platform, the allowable moments may establish a working
envelope smaller than the Envelope Control System's enve-
lope and may result in moment violations at the extreme plat-
form positions. Violations of the moment control systems
allowable moment will result in reduced function speeds, BCS
warning light illumination, and restriction of functions. The
platform alarm will sound and the BCS light will flash with
attempts to operate restricted functions. The restricted func-
tions due to moment system violations related to forward
reach are disallowing jib functions, lift down, telescope out,
swing, drive, and steer. The restricted functions due to
moment system violations related to backward reach are disal-
lowing jib functions, lift up, telescope in, swing, drive and
steer. Recognized failures within this system will result in con-
trol by the Envelope Control System, reduced function speeds,
and BCS warning light illumination. The boom will be
restricted from leaving the transport position (see item 14)
until the failure is resolved.
Boom Control System (BCS) Functional Check
(Push to Test) System
The machine is equipped with a system for the operator to
daily verify the proper functioning of the Boom Control Sys-
tem (Envelope Control System and the Moment Control Sys-
tem). The operator is instructed to position the boom in the
position described by the instruction decal and to then verify
the control system cut out the main telescope movement at
the correct length. When the operator pushes the button
mounted on the ground control panel, the control system
compares the current moment reading in the moment system
to the moment expected for this position. If the current
moment is within allowable tolerance for the test position, the
green BCS indicator will illuminate indicating the system is
working properly. If the current moment is not within the
allowable tolerance for the test position, the red BCS indicator
will illuminate indicating the machine requires service by JLG
authorized service personnel before the system is used. Failure
of this test will not restrict the functionality of the machine
and will not cause a system fault. It is the operators responsi-
bility to take proper action. The machine can be in either
capacity mode of the dual capacity system for this system
check.
Controlled Arc System
The Controlled Arc System uses the envelope control sensors
to enhance the control of the main boom within the working
envelope. The purpose of the controlled arc system is to mini-
mize the interaction of lift functions with envelope edges and
to increase user efficiency. This minimizes the effect of a long
boom working in a comparatively narrow envelope. Because
the boom is permitted to extend to longer lengths at high
angles than at it is low angles, lift commands would normally
cause the boom to violate the permitted envelope while lifting
down or conversely require the operator to frequently com-
mand telescope out while lifting to high heights. The con-
trolled arc system optimizes the envelope shape by
automatically introducing telescope in or out during “lift only”
commands. Telescope flow is regulated during lift commands
to maintain a constant percentage of available boom length
(0% is always fully retracted, 100% is variable as the permitted
length changes when the boom is raised). The target percent-
age will be maintained throughout the lift command whether
it is maintaining 0%, 100%, or any percentage in between. The
target percentage is established at the start of lift command or
end of manual telescope commands when using multiple
functions with lift. The telescope command can be used inde-
pendently or in combination with other functions. Manual
introduction of telescope will override the controlled arc sys-
tem and result in conventional control. Controlled arc will be
disabled with any sensor failure, any moment violation, any
envelope violation, or with auxiliary power functions. The con-
trolled arc functionality can be turned off using the manual
position of the boom control select switch. When selected, this
system is active at all boom angles and lengths.