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PSC SOFTWARE FUNCTIONS
The operation of the AC Drive System is regulated by
a software program which resides in the Propulsion
System Control Panel's memory. The software pro-
gram also contains instructions to test and fault isolate
the system.
This section describes the PSC software program and
its functions without regard to hardware.
INPUT PROCESSING
This function reads in all external inputs for use by the
PSC. The Input Processing function performs any
signal conditioning required and computes the re-
quired derived inputs.
STATE MANAGEMENT
State Machine
As part of the total software package, a particular
group of regulatory software commands is included
called a "state machine". The state machine controls
the various functions of truck operation.
The software implements the state machine by keep-
ing track of which state the truck is in, and which state
the truck is allowed to move into if the operator re-
quests a different mode of operation. Each software
state is defined as follows:
Startup/Shutdown State:
The purpose of this state is to ensure the system is in
a desired known state upon startup or shutdown. This
is an unpowered state.
NOTE: Powered and unpowered refer to the state of
the DC link; 600 volts or more on the DC link equals
"powered". 50 volts or less on the DC link equals
"unpowered".
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Test State:
The purpose of this state is to provide an environment
for the verification of system functionality. Test state
will support a variety of activities, including:
NOTE: The Test state may be either powered or
unpowered at a given point in time, depending on
which activities are being performed.
Ready State:
Ready state is the default powered state. The system
will be in this state whenever the engine and control
system are ready to provide power, but none is re-
quested.
Ready state also is the state where the DC link is
discharged in preparation for Shutdown, Rest, or in
reaction to certain event conditions. Therefore, Ready
state should not be considered strictly a powered state
(as are Propel and Retard described below).
Rest State:
Rest is an unpowered state whose purpose is to
conserve fuel while the truck idles for an extended
period of time. Rest state also provides an environ-
ment where maintenance personnel can control the
engine without causing power to be applied to the DC
link.
Propel State:
The purpose of this state is to provide the power
system configuration and overall environment for en-
gine-powered propulsion. This is strictly a powered
state, i.e., the system will not be allowed to maintain
propel state without sufficient power on the DC link.
Electrical Propulsion System Components
1. Waiting for the engine to start (if needed).
2. Automatic testing on initial system startup or
following rest state.
3. Application of power to the DC link.
4. Externally initiated testing to clear a fault, set
temporary variables, or for maintenance pur-
poses.
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Troubleshooting
