case studies elevator control system elevator control system comet case studies from task...

Case Studies

Elevator control Elevator control systemsystem

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From task structuring to target From task structuring to target system configuration.system configuration.

Centralized solution

- Determine tasks for each subsystem

- Define task interfaces

- Design of data abstraction classes

Task structuring

Task structuring Centralized solution

-Elevator Control System is mapped to a single CPU or to a multiprocessor configuration with shared memory

-Elevator Status&Plan object is accessible to all elevators and to the scheduler

-We can use a centralized repository of data

Assumptions

Task structuring Centralized solution

- Analize all the objects on the collaboration diagrams

- Apply the task structuring criteria

Procedure

Elevator subsystemTask structuring

Elevator button Interface

- Asynchronous input device interface criterionAsynchronous input device interface criterion -> Separate task

- Task inversion criteria -> One task handles all the elevator buttons

Task structuring Elevator subsystem

Elevator Manager

-Structured as a Coordinator ObjectStructured as a Coordinator Object


Elevator Status&Plan

-Passive data abstraction object -> Passive data abstraction object -> doesn’t need a separate thread of controldoesn’t need a separate thread of control


«state dependent control»

:ElevatorControl

«entity»

:ElevatorStatus&Plan

«coordinator»

:Scheduler

«output device interface»

:DirectionLampInterface

«external output device»

:FloorLamp


:MotorInterface

«external output device»

:Motor

D10a: Departed (Floor#)

D10: Departed (Floor#)

D6a: Off Up Direction Lamp

D6: UpD9:

Elevator Started

D6a.1: Direction Lamp Output

D8: Motor Response

D7: Start Up Motor Command

Elevator Control

Task structuring

Each Elevator Control object is mapped to a separate Elevator Controller taskIt interacts with several output device interface objects such as:

-Motor Interface

-Door Interface

-Elevator Lamps Interface

Do we need separate tasks?

Elevator subsystem

Elevator Control

Task structuring

-Passive devices

-Output request executed on demand

-The calling task has to wait for the output request to complete

-Elevator Controller doesn’t execute concurrently with Motor Interface and Door interface

By the Control Clustering Criteria we combine these tasks with the Elevator Controller task

Elevator subsystem

Output devices

Elevator Controller doesn’t execute concurrently with Motor Interface and Door interface

Elevator Door

Opening

Elevator at Floor

Elevator Stopping

Elevator MovingEntry/Departed

Approaching Floor/Check This Floor

Approaching Requested Floor/Stop ,On Direction Lamp

Elevator Stopped/Open Door, Off Elevator Lamp, Arrived

Door opened/Start Timer


For the Elevator Control subsystem we have four tasks

Task structuring

-Elevator Buttons Interface

-Arrival Sensors Interface

-Elevator Controller

-Elevator Manager

Elevator subsystem

Summary

«external inputdevice»

: FloorButton

Floor Button

Request «subsystem»: Scheduler

Floor LampOutput

«external outputdevice»

: DirectionLamp

Direction Lamp

Output

«input device interface»

:FloorButtonInterface


:FloorLampInterface

«output device

interface»

:DirectionLampInterfac

e

«subsytem»:ElevatorSubsystem

ServiceRequest

Floor Lamp

Command«external output

device»: FloorLamp

Direction Lamp

Command

«data collection subsystem»

:FloorSubsystem

Task structuring Floor subsystem

We start from the floor subsystem structure.

Task structuring Floor subsystem

We determine the Floor Button Interface task

We consider Floor Lamp Interface and Direction Lamp Interface

-Are passive output devices

-Receive concurrent requests from the Elevator Controller instances

We use monitors tasks to serialize the requests

Centralized solutionTask structuring

Centralized solutionTask structuring

<<resourcemonitor>>

:FloorLampsMonitor

<<resourcemonitor>>:Direction

LampsMonitor

<<asynchronousinput deviceinterface>>

:FloorButtonsInterface

<<data collectionsubsystem>>

:FloorSubsystem

ServiceRequest

DirectionLampOutput

FloorButton

Request

FloorLampOutput

<<coordinator>>:ElevatorManager


:ElevatorButtonsInterface


:ArrivalSensorsInterface

<<subsystem>>:Scheduler

<<dataabstraction>>


Check NextDestination

Check ThisFloor(Floor#)

Arrived(Floor #)

departed(Floor #)

NextDestination

ApproachingRequested

Floor

Elevator #

SelectElevator

ArrivalSensorInput

ElevatorButton

Request

SchedulerRequest

ElevatorCommittment

ElevatorRequest

ElevatorLamp

Output

FloorLamp

Command

DirectionLamp

Command

ApproachingFloor(Floor #)

<<control subsystem>>:ElevatorSubsystem

<<controlclustering>>

:ElevatorController

AckUpdate

Up,Down

DoorCommand

DoorResponse

MotorCommand

MotorResponse

Define Task interfaces

Task structuring

-Consider message interfaces between concurrent tasks

-Map them to loosely or tightly coupled messages

-Add name and parameters of each message


Task structuring

For instance:

ElevatorElevator

RequestRequest<<asynchronous<<asynchronous

input device input device interface>>interface>>


<<coordinator>><<coordinator>>

:Elevator:Elevator

ManagerManager

ElevatorElevator

Request(Elevator#,floor#,direction)Request(Elevator#,floor#,direction)<<asynchronous<<asynchronous

input device input device interface>>interface>>


<<coordinator>><<coordinator>>

:Elevator:Elevator

ManagerManager


Task structuring

<<resourcemonitor>>

:FloorLampsMonitor

<<resourcemonitor>>:Direction

LampsMonitor


:FloorButtonsInterface

<<data collectionsubsystem>>

:FloorSubsystem

ServiceRequest

(floor#,direction)

DirectionLampOutput

FloorButton

Request

FloorLampOutput







<<dataabstraction>>


ArrivalSensorInput

ElevatorButton

Request

ElevatorLampOutput

OffFloor Lamp(floor#,direction)

On/OffDirection Lamp(elevator#,floor#,direction)

ApproachingFloor(Elevator#,Floor #)



:ElevatorController

Up,Down

Check NextDestination(inelevator out

direction)

Check This Floor(inElevator#,inFloor#,out

FloorStatus,outdirection)

Arrived(elevator#,Floor #,direction)

Departed(elevator#,Floor

#,direction)

MotorCommand(out

MotorResponse)

Door Command(outdoor response)

UpdatePlan(elevator#,Floor #,direction out

idleStatus)

SchedulerRequest

(elevator#,Floor#,direction)

SelectElevator(infloor#,in

direction,outelevator)

ElevatorCommittment

(elevator#,Floor #,direction)

Elevator Request(elevator#,Floor

#,direction)


Task structuring

Design of Data Abstraction Class

Task structuring

<<data abstraction>>Elevator Status&Plan

+ arrived(elevator#,floor#,direction)+ departed(elevator#,floor#,direction)+ checkThisFloor(in elevator#,in floor#,out floor status,out direction)+ checkNextDestination(in elevator,#out direction)+ updatePlan(elevator#, floor#, direction ,out idlestatus)+ selectElevator(in floor#, out elevator#,in direction)

Distributed Solution

-Subsystem Structuring-Subsystem Structuring -Design of Device Interface classes

-Design of information hiding Design of information hiding classesclasses

-Design of Device Interface classes-Design of State-Dependent classes

-Detailed software designDetailed software design-Design of Connector objects-Design of Composite Tasks

-Target system configurationTarget system configuration

Distributed solutionGeneral description

-Multiple nodes interconnected by a LAN

-No shared memory

Physical configuration:

-All communication is via loosely coupled messages

Task structuring Distributed Solution

<<coordinatorsubsystem>>

:Scheduler

<<controlsubsystem>>

:ElevatorSubsystem

<data collectionsubsystem>>

:FloorSubsystem

<<external outputdevice>>

:DirectionLamp

<<external inputdevice>>

:ArrivalSensor

<<controlsubsystem>>

:ElevatorSubsystem


:Door


:ElevatorLamp

<<external inputdevice>>

:FloorButton


:Motor


:FloorLamp

SchedulerRequest

Arrival(Floor #)

Departed(Floor #)

ElevatorCommitment

ArrivalSensorInput

ElevatorLampOutput

ElevatorButton

Request

Floor LampCommand

Direction LampCommand

DoorCommand

DoorResponse

Direction LampOutput

Floor LampOutput

FloorButton

Request

Motor Response

MotorCommand

ServiceRequest

<<system>>:Elevator

ControlSystem


-Now the Scheduler and the multiple instances of the ElevatorManager cannot directly access Elevator Status&Plan data object

An emerging issue

We may:

•Embed ElevatorStatus&Plan in a server object

•Use replicated data


Server solution

-Clients access the ElevatorStatus&Plan with a synchronous message with reply

Risk of Bottleneck!


Data replication solution-Each instance of the Elevator Subsystem maintains a Local ElevatorStatus&Plan -The Scheduler Subsystem maintains an Overall Status&Plan

Faster data access

Distributed solutionSubsystem Structuring

Structure of Elevator Subsystem

-Similar to the centralized solution

-Each Elevator subsystem contains a Local Elevator Status&Plan object

Distributed solutionTask structuring



:ElevatorController<<asynchronous

input device >>:ArrivalSensors

<<asynchronousinput device>>:ElevatorButton





<<passive outputdevice>>

:ElevatorLamp <<passive outputdevice>>

:Motor


:Door


<<entity>>:LocalElevatorStat

us&Plan

Check NextDestination

Check ThisFloor(Floor#)

Arrived(Floor #)

departed(Floor#)

NextDestination

ApproachingRequested

Floor

DoorCommand

DoorResponse

Arrived(Floor #)

Departed(Floor #)

ArrivalSensorInput

ElevatorButton

Request

MotorCommand

MotorResponse

SchedulerRequest

ElevatorCommittment

ElevatorRequest

ElevatorLampOutput

Floor LampCommand

Direction Lamp Command

ApproachingFloor(Floor #)


<<subsystem>>:FloorSubsystem

Distributed solutionTask structuring



:ElevatorController<<asynchronous

input device >>:ArrivalSensors

<<asynchronousinput device>>:ElevatorButton






:ElevatorLamp <<passive outputdevice>>

:Motor


:Door


<<entity>>:LocalElevatorStatus

&Plan

Check NextDestination(inelevator out

direction)

Check This Floor(inElevator#,inFloor#,out

FloorStatus,outdirection)

Arrived(elevator#,Floor #,direction)

Departed(elevator#,Floor

#,direction)

DoorCommand(out

doorresponse)

Arrived(elevator#,Floor

#,direction)

Departed(elevator#,Floor #,direction)

ArrivalSensorInput

ElevatorButton

Request

MotorCommand(out MotorResponse)

SchedulerRequest

(elevator#,Floor#,direction)

ElevatorCommittment

(elevator#,Floor

#,direction)

Elevator Request(elevator#,Floor

#,direction)

ElevatorLampOutput

offFloorLamp (Floor#,direction)

onDirection Lamp( Floor #,Elevator#,direction)

ApproachingFloor(elevator

#,Floor #)


UpdatePlan(elevator#,Floor

#,direction outidleStatus)

Up(elevator #)

Down(elevator #)

<<subsystem>>:FloorSubsystem


Structure of Scheduler Subsystem

-Elevator Status&Plan Server Task

-Elevator scheduler

-Receives Status and commitment messages -Updates Overall Elevator Status&Plan

-Receives Service Requests messages

Design of information hiding classes

-Device Interface classes

-Data abstraction class(distributed)

-State Dependent class

We design the operations of

<<Output Device interface>>Floor Lamp Interface

+ initialize()+off()

<<Output Device interface>>Arrival Sensor Interface

+ initialize()+ read(out sensorInput)

Design of device interface classes


Design of device interface classes

<<Output Device interface>>Motor Interface

+ initialize()+ stop(out stopped)+ up(out started)+ down(out started)

<<Output Device interface>>Door Interface

+ initialize()+ open(out opened)+ close(out closed)



<<data abstraction>>LocalElevator Status&Plan

+ arrived(elevator#,floor#,direction)+ departed(elevator#,floor#,direction)+ checkThisFloor(in elevator#,in floor#,out floor status,out direction)+ checkNextDestination(in elevator,#out direction)+ updatePlan(elevator#, floor#, direction ,out idlestatus)



<<data abstraction>>OverallElevator Status&Plan

+ arrived(elevator#,floor#,direction)+ departed(elevator#,floor#,direction)+ updatePlan(elevator#, floor#, direction ,out idlestatus)+ selectElevator(in floor#, out elevator#,in direction)


Design of State Dependent Class

<<state dependent control>>Elevator Control

+ processEvent(in event,out action)+ currentStatus():Status


Detailed Software Design

Two main phases:

-Design of the connector objects

-Design of the composite tasks

Detailed Software DesignDesign of connector objects

We introduce connectors to hide the details of message communication.

The sender tasks should be unaware of the location of the receiver tasks

Location transparency


Elevator subsystem

Design of connector objects


Messages from Arrival Sensor Interface and Elevator Manager to Elevator controller never overlap-> We can use one message buffer instead of two

We introduce three message queue connectors to hide the details of asynchronous(and possibly remote) communication

Elevator subsystem

Design of connector objects

Detailed Software DesignDesign of connector objects


Elevator Controller Task embeds

-Three output device interfaces

-One state dependent control object

-Two objects that provide synchronization

Design of composite tasks


-Each device interface object for an asynchronous I/O device is placed inside the task supporting that device

-Resource monitor tasks embed the passive I/O interfaces for the devices they operate

Design of composite tasks

Detailed Software DesignDesign of composite tasks

Distributed solutionSystem Configuration

Target system configuration

-Instances of the component types are defined

-Component instances are interconnected

-Component instances are mapped to physical nodes


A possible physical configuration

-One Elevator Subsystem for each elevator node

-One Floor Subsystem for each floor node

DefinitionControl Clustering criteria

Another possible physical configuration

-All instances of the floor subsystem mapped to one node

-One Elevator Subsystem for each elevator node

case studies elevator control system elevator control system comet case studies from task...

Documents

floor elevator

elevator buttons interface

elevator lamps interface

elevator control subsystem

checkthisfloorin elevator

floor button interface

door interface elevator

tasks task structuring