JLG 1100S Service Manual - Manual (Page 276)

SECTION 6 - JLG CONTROL SYSTEM
6-2 – JLG Lift – 3121256
6.2 CANBUS COMMUNICATIONS
CANbus: CAN (Control Area Network) is a two wire differ-
ential serial link between the Platform Module, Ground
Module, Boom Length Angle Module and the Chassis
Module providing bi-directional communications.
Two-wire: One wire (red) is driven high (5v) and the other
low (black) (0v) to send a signal; both wires ”float” (2.5v)
when no signal is being sent.
Differential: Any electrical line noise can affect the high or
the low wires but never both, so communications is not
corrupted.
Serial Link: Messages are being sent bit by bit along the
wires; the high bus speed allow all modules to be con-
stantly updated around 20 times per second. Typical traf-
fic is 300 - 500 messages per second.
A complete CANbus circuit is approximately 60 ohms,
which can be verified at the ”T” fitting inside the ground
station or below the BLAM. Each individual circuit from the
modules is approximately 120 ohms.
The GROUND MODULE is the master system controller.
Most functions are dispatched and coordinated from this
module, all other system modules (PLATFORM, BLAM
L
CHASSIS) handle sub-tasks. All characterized information
(values) are stored into the ground module (i.e., Personal-
ities or Calibrations).
Interlocks: Any device that sends an electrical input. (For
an example a limit switch, proximity switch, etc;)
Platform Level: The GROUND MODULE stores the
default values and handles interlocks. The PLATFORM
MODULE reads the sensors mounted on the platform
assembly and controls the Level Up / Down valves to
maintain setpoint sent from the GROUND MODULE.
Steer: The GROUND MODULE stores crack points, sends
desired drive direction, sends steering mode and sends
axle extend / retract commands. The PLATFORM MOD-
ULE reports the steering switch position to the GROUND
MODULE. The CHASSIS MODULE modulates each steer
left / right valve to maintain commanded wheel position.
Drive: The GROUND MODULE stores crack points, sends
commands for each drive pump to the BLAM. (Command
is computed from drive joystick input, interlocks, wheel
angle, etc). BLAM maintains proper current for the drive
pumps by modulating PWM outputs.
Lift, Tele, & Swing: The GROUND MODULE stores
default values, handles interlocks and calibration informa-
tion. Lift, Telescope and Swing commands are dependent
upon interlocks through out the machine. Boom angle,
length and swing are controlled by the GROUND MOD-
ULE. The BLAM monitors and communicates (CANbus) to
the GROUND MODULE boom angle and boom length via
two angle sensors, a length sensor and a load moment
pin.