Service Manual Instruction Manual

SECTION 4 - BOOM & PLATFORM
3121171 – JLG Lift – 4-3
4.7 TOWER PATH CONTROL SYSTEM
(see Figure 4-1., Tower Path vs. Main Boom Angle)
The Tower Path Control System uses the envelope control sen-
sors to enhance the control of the tower boom for increased
user efficiency and is used as an integral part of the envelope
control system (see Section 4.6, Envelope Control System).
Both the ground and platform control panels use one function
switch to control the tower. User commands for tower lift up or
tower lift down causes the control system to automatically
introduce the correct combination of tower telescope and
tower lift for the tower boom to follow a pre-described path or
trajectory of the tower nose.
The tower path is a fixed relationship of tower length and
tower angle (relative to gravity) and is variable only by the
angle of the main boom. With main boom angles below +15°,
the tower boom will reach maximum angles of 68° (at full
tower boom extension) and with main boom angles above
+65° the tower boom will reach maximum angles of 72° (at full
tower boom extension).
Movement of the main boom will cause the control system to
adjust the tower path accordingly. A fully raised tower boom
will automatically vary in angle from 72° to 68° as the main
boom is lowered from its maximum angle to the ground and
conversely be raised from 68° to 72° as the main boom is
raised from the ground to maximum angle. The amount of
tower angle variation during main boom movements dimin-
ishes as the tower is lowered.
NOTE: For more detailed information concerning system adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.
4.8 AUTOMATIC MAIN BOOM CONTROL SYSTEM
The Automatic Main Boom Control System uses the envelope
control sensors to enhance the control of the main boom dur-
ing tower lift functions. Due to the mechanical joining of the
main and tower booms, changes in tower boom angle would
normally have an opposite effect on the main boom angle. To
compensate for this, when the tower is raised the control sys-
tem automatically introduces main lift up. Similarly, when the
tower is lowered the control system automatically introduces
main lift down. This is done to keep the platform moving in
the same direction as the user command and to increase user
efficiency during tower lift functions.
The interaction of the main boom and the tower boom is
slightly different when the main boom is above or below 60°
relative to gravity.
During tower lift up or tower lift down movements with the
main boom below 60°, the control system will maintain the
angle of the main boom (relative to gravity) read at the start of
the tower lift command or as read at the conclusion of main
lift during combined tower and main lift commands.
During tower lift down movements with the main boom ini-
tially above 60°, the control system will lower the main boom
to approximately 60° before initiating tower movement. The
control system will then control the main boom to 60° for the
remainder of the tower lift down command.
During tower lift up movements with the main boom initially
above 60°, the control system will delay automatic compensa-
tion of the main boom angle during the tower lift movement
until the main boom reaches approximately 60°. The control
system will then control the main boom to 60° until the tower
boom has reached its maximum height. Continuing to operate
the tower lift up function when the tower reaches its maxi-
mum height, will cause the control system to automatically
raise the main boom to its original angle.
NOTE: For more detailed information concerning system adjust-
ment and operation, refer to Section 6 - JLG Control Sys-
tem.