Oshkosh JLG 1500SJ, Service And Maintenance Manual

Page: 535 / 706

SECTION 6 - JLG CONTROL SYSTEM
3121262 – JLG Lift – 6-19
6.4 CANBUS COMMUNICATIONS
CANbus: CAN (Control Area Network) is a two wire differential
serial link between the Platform Module, Jib 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 constantly
updated around 20 times per second. Typical traffic 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 (UGM) is the master system controller.
Most functions are dispatched and coordinated from this
module, all other system modules (PLATFORM, JIB, BLAM,
CHASSIS) handle sub-tasks. All characterized information (val-
ues) are stored into the ground module (i.e., Personalities 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 val-
ues 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 MODULE 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 com-
mands for each drive pump to the BLAM. (Command is com-
puted from drive joystick input, interlocks, wheel angle, etc).
BLAM maintains proper current for the drive pumps by modu-
lating PWM outputs.
Lift, Tele, & Swing: The GROUND MODULE stores default val-
ues, handles interlocks and calibration information. Lift, Tele-
scope and Swing commands are dependent upon interlocks
through out the machine. Boom angle, length and swing are
controlled by the GROUND MODULE. 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.