Gps Base Accident Identification

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  • Topic: Rail transport modelling, Unified Modeling Language, Digital Command Control
  • Pages : 6 (675 words )
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  • Published : February 19, 2013
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Introduction
Example: model train controller.

Dept. of CSE&IT, DBCET, Guwahati

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Purposes of example
Follow a design through several levels of abstraction. Gain experience with UML.

Dept. of CSE&IT, DBCET, Guwahati

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Model train setup
rcvr motor

power supply console

ECC

command

address

header
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Dept. of CSE&IT, DBCET, Guwahati

Requirements
Console can control 8 trains on 1 track. Throttle has at least 63 levels. Inertia control adjusts responsiveness with at least 8 levels. Emergency stop button. Error detection scheme on messages. Dept. of CSE&IT, DBCET, Guwahati

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Requirements form

Dept. of CSE&IT, DBCET, Guwahati

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Digital Command Control
DCC created by model railroad hobbyists, picked up by industry. Defines way in which model trains, controllers communicate. Defines packet format and semantics

Dept. of CSE&IT, DBCET, Guwahati

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DCC electrical standard
Voltage moves around the power supply voltage 1 is 58 µs, 0 is at least 100 µs. logic 1 logic 0

time 58 µs >= 100 µs

Dept. of CSE&IT, DBCET, Guwahati

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Conceptual specification
Before we create a detailed specification, we will make an initial, simplified specification. ִGives us practice in specification and UML. ִGood idea in general to identify potential problems before investing too much effort in detail.

Dept. of CSE&IT, DBCET, Guwahati

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Basic system commands
command name set-speed set-inertia estop parameters speed (positive/negative) inertia-value (nonnegative) none Dept. of CSE&IT, DBCET, Guwahati

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Message classes
command

set-speed value: integer

set-inertia value: unsignedinteger

estop

Dept. of CSE&IT, DBCET, Guwahati

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Subsystem collaboration diagram
Shows relationship between console and receiver (ignores role of track): 1..n: command :console :receiver

Dept. of CSE&IT, DBCET, Guwahati

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Typical control sequence
:console set-inertia set-speed set-speed estop set-speed :train_rcvr

Dept. of CSE&IT, DBCET, Guwahati

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Major subsystem roles
Console:
ִread state of front panel; ִformat messages; ִtransmit messages.

Train:
ִreceive message; ִinterpret message; ִcontrol the train. Dept. of CSE&IT, DBCET, Guwahati 13

Console system classes
1 1 panel 1 knobs* 1 console 1 1 formatter 1 1 transmitter 1 1 sender*

Dept. of CSE&IT, DBCET, Guwahati

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Console class roles
panel: describes analog knobs and interface hardware. formatter: turns knob settings into bit streams. transmitter: sends data on track.

Dept. of CSE&IT, DBCET, Guwahati

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Train system classes
train set 1 1..t train 1 1 controller 1 1 motor interface 1 1 pulser*

1 receiver 1 detector* 1 1

Dept. of CSE&IT, DBCET, Guwahati

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Transmitter and receiver classes
transmitter send-speed(adrs: integer, speed: integer) send-inertia(adrs: integer, val: integer) set-estop(adrs: integer) receiver current: command new: boolean read-cmd() new-cmd() : boolean rcv-type(msg-type: command) rcv-speed(val: integer) rcv-inertia(val:integer) 17

Dept. of CSE&IT, DBCET, Guwahati

Train class roles
receiver: digitizes signal from track. controller: interprets received commands and makes control decisions. motor interface: generates signals required by motor. detector* : detects analog signals on the track and converts them into digital form.

pulser* : turns digital commands into the analog signals required to control the Dept. of CSE&IT, DBCET, motor speed. Guwahati

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Console physical object classes
knobs* train-knob: integer speed-knob: integer inertia-knob: unsignedinteger emergency-stop: boolean pulser* pulse-width: unsignedinteger direction: boolean sender* send-bit() detector* read-bit() : integer

Dept. of CSE&IT, DBCET, Guwahati

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Control input sequence diagram
:knobs :panel :formatter :transmitter change in read panel panel-active control panel settings settings send-command read panel change in...
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