JLG 1250AJP Service Manual - Manual (Page 243)

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
sensors 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 com-
bination 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 diminishes as the tower is lowered.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.
4.8 AUTOMATIC MAIN BOOM CONTROL
SYSTEM
The Automatic Main Boom Control System uses the enve-
lope control sensors to enhance the control of the main
boom during 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 system automatically intro-
duces 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 effi-
ciency 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 conclu-
sion of main lift during combined tower and main lift com-
mands.
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 move-
ment. 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 ini-
tially above 60°, the control system will delay automatic
compensation 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 maximum height, will cause the control
system to automatically raise the main boom to its original
angle.
NOTE: For more detailed information concerning system
adjustment and operation, refer to Section 6 - JLG
Control System.