Gps Base Accident Identification

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

Dept. of CSE&IT, DBCET, Guwahati


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

Dept. of CSE&IT, DBCET, Guwahati


Model train setup
rcvr motor

power supply console





Dept. of CSE&IT, DBCET, Guwahati

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


Requirements form

Dept. of CSE&IT, DBCET, Guwahati


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


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


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


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


Message classes

set-speed value: integer

set-inertia value: unsignedinteger


Dept. of CSE&IT, DBCET, Guwahati


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

Dept. of CSE&IT, DBCET, Guwahati


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

Dept. of CSE&IT, DBCET, Guwahati


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

ִ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


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


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


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


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


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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