JLG 1100S Service Manual - Manual (Page 151)

SECTION 4 - BOOM & PLATFORM
3121256 – JLG Lift – 4-3
Moment Control System
The Moment Control System is the secondary means of
controlling the stability of the machine. This system uses a
load moment pin to attach the lift cylinder of the boom to
the turntable. This pin is instrumented with gauges allow-
ing the forces in the pin to be monitored. These forces are
used to compare the actual boom moment (force at a dis-
tance) to a predetermined 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 effectively controls the for-
ward 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 Con-
trol 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
envelope and may result in moment violations at the
extreme platform positions. Violations of the moment con-
trol systems allowable moment will result in reduced func-
tion speeds, BCS warning light illumination, restriction of
functions, and sounding of the platform alarm and the
flashing of the BCS light with attempts to operate
restricted functions. The restricted functions 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 disallow-
ing jib functions, lift up, telescope in, swing, drive, and
steer. Recognized failures within this system will result in
control by the Envelope Control System, reduced function
speeds, BCS warning light illumination. The boom will be
restricted from leaving the transport position until the fail-
ure is resolved.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
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
System (Envelope Control System and the Moment Con-
trol System). 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 telescope
movement at the correct length. When the operator
pushes the push button mounted on the ground control
panel, the control system compares the current moment
reading in the moment system and compares it 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 indi-
cator will illuminate indicating the machine requires ser-
vice by JLG authorized service personnel before the
system is used. Failure of this test will not restrict the func-
tionality of the machine and will not cause a system fault.
It is the operators responsibility to take proper action. The
machine can be in either capacity mode of the dual
capacity system for this system check.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
Controlled Arc System
The Controlled Arc System uses the envelope control sen-
sors to enhance the control of the boom within the work-
ing envelope. The purpose of the controlled arc system is
to minimize 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 command telescope out
while lifting to high heights. The controlled arc system
optimizes the envelope shape by automatically introduc-
ing telescope in or out during "lift only" commands. Tele-
scope 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 per-
centage 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 com-
mand can be used independently or in combination with
other functions. Manual introduction of telescope will
override the controlled arc system and result in conven-
tional control. Controlled arc will be disabled with any sen-