JLG 1230ES Service Manual - Manual (Page 31)

SECTION 3 - THEORY OF OPERATION - 1230ES
3121222 – JLG Lift – 3-1
SECTION 3. THEORY OF OPERATION - 1230ES
3.1 OVERVIEW
The GROUND MODULE is the master system controller.
Most functions are dispatched and coordinated from this
module, all other system modules handle sub-tasks. All
characterized information (values) are stored into the
ground module (i.e., Personalities, Machine Setups or
Calibrations). If the ground module is reprogrammed, this
information is lost. The technician should record Personal-
ities and Machine Setups before programming so they
can be restored afterwards. Otherwise, default values can
be used as a starting point to restore previous configura-
tion.
The PLATFORM MODULE reads switch and joystick posi-
tions and relays that information to the GROUND MOD-
ULE. It uses information from the CAN bus for operator
display. It also reports faults pertaining to devices in the
Platform Control Station. In ground mode, the platform
control station may be removed from the vehicle without
affecting operation.
The POWER MODULE controls the main contactor, drive
motors and hydraulic pump motor via commands from
the CAN bus. It also measures current applied to these
loads and input voltage for fault protection and reporting.
For safe operation of the vehicle, the control system will
not allow certain functions under certain conditions. These
are called interlocks. Specific interlocks are discussed
below. The interlocks discussed assume that all control
system devices are functioning properly unless indicated.
Fault conditions will generate DTC’s and additional inter-
locks. Some faults only show up at power-up when the
control system performs a self-test. All controls should be
left alone during this test.
Note that the market and model of the machine affects
what personalities and setups are visible by the Analyzer.
The appropriate information is displayed for the given
model and market. The market and model must be set
properly for safe and lawful operation of the machine.
3.2 MODES OF OPERATION
Ground Mode
In Ground Mode, all visual indicators (LED) in the Platform
are off. In fact, the Platform Control Box may be entirely
disconnected as a normal measure (to secure the vehi-
cle), and this does not prevent Ground Mode operation.
When the machine is powered up in ground mode, only
the functions in the Ground control station are operational,
namely Lift Up and Down. Lift Up and Down is controlled
by a two-position, momentary toggle switch with a center
off position. The switch has the same effect as placing the
joystick in the full up or full down position.
Platform mode
In platform mode the Platform Control Box is enabled. It is
the primary control station for the vehicle. At power-up
indicators applicable to the vehicle configuration illumi-
nate for a lamp check: Battery Discharge Indicator, Sys-
tem Distress Indicator and Tilt Indicator.
3.3 CAN COMMUNICATIONS
CAN (Controller Area Network) is the type of two-wire dif-
ferential serial communication link used between the plat-
form board, ground board, and the power module for
control of the vehicle. This type of network has matured
since its invention in 1986 and is used extensively in many
kinds of machines.
Two-Wire Differential: The signal meaning is derived from
the difference in voltage between two wires, usually
twisted together in a common "jacket". This jacket can
also contain a shield surrounding the wires inside for
noise protection. Any noise that does penetrate the shield
will affect both wires the same. However, the difference in
voltage stays the same, therefore signal meaning is not
corrupted. This differs from one-wire signals in that one-
wire signals derive the signal meaning from the difference
between the signal wire and system ground wire. The sys-
tem ground is the ground for many signals, as well as
power. Any noise on either wire will change the signal and
may corrupt it.
Serial Communication Link: Modules on the link send
messages digitally, bit by bit along the wires where differ-
ent voltage levels represent a "1" or a "0". The 1’s and 0’s
are assembled by the receiver according to the protocol
used to determine the messages meaning. Using serial
communication allows two wires to replace many more. It
also allows use of sensor and switch information in multi-
ple places without duplicating those sensors and
switches.
CAN: On a bus, all modules on the bus are connected to
the same wires. A CAN bus could be represented on a
schematic by a long pair of straight lines with multiple
modules connected to them by short pairs of lines. It has
a termination resistor at both ends of the long lines placed
between the two wires, These resistors are approximately
120 Ohms. On a JLG aerial work platform, this is typically
in the platform and in the chassis. These resistors may be
in the harness or in the module. A complete CAN circuit
measures approximately 60 Ohms between the two wires
and these wires are open to the shield.
Each module on the CAN bus broadcasts its messages
according to a priority assigned to the message. All the
other modules will receive the message and determine if it
is important to them. Typical message traffic is 300 - 500
messages per second. The high bus speed allow all mod-
ules to be constantly updated around 20 times per sec-
ond. A CAN network also has error detection and handling
for robust communications.