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A Robotics Task Coordination Case Study

Davide Brugali, Luca Gherardi,Patrizia Scandurra

May 9, 2011 - Shanghai, China

lunedì 9 maggio 2011

Davide Brugali, Luca Gherardi, Patrizia ScandurraMay 9, 2011 - Shanghai, China

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Introduction

Separation of concerns: computation and coordination

The case study

High level solution

Coordination FSM

Implementation

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Outline



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Goal: separate of concerns in the development of component based systems (in our case particular attention on Computation and Coordination).

Solution: model and implement Computation and the Coordination through 2 different frameworks (SCA and ASM).

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Introduction



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Computation: concerned with data processing algorithms required by an application.

Configuration: determines which system components should exist, and how they are inter-connected.

Communication: deals with the exchange of data.

Coordination: concerned with the interaction of the various system components.

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Separation of concerns



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Computation: how the functionalities are realized.

Algorithms: data structures and operations.

Coordination: when the functionalities are used.

Interaction among components: cooperation and competition.

They have to be modeled and implemented in a separate way.

We chose two different frameworks.

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Computation Vs. Coordination



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We adopted the Service Component Architecture.

Set of specifications which describe a model for building applications.

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Computation and SCA



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We adopted the Abstract State Machines

Evolution of the FSM

Formal Method

Automatic validation and verification of correctness.

Runtime monitoring and self-adaptation.

Provides rigor without mathematical overkill.

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Coordination and ASM



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Developed by P. Scandurra and F. Albani at University of Bergamo.

Extension of the SCA Eclipse plugin (front-end).

Extension of the Tuscany runtime (back-end).

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SCA - ASM



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Three participants:

Laser scanner: executes scans (n measures) on demand and writes results on a data buffer: scan( from, nSteps ).

3D Perception and Obstacle Avoidance applications.

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LaserScanner

Client 1 3D Perception

Client 2Obstacle Avoidance

The case study scenario



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A scan operation requires an amount of time that is not fixed.

A client could request single and multiple scans.

A scan request could be received while the scanner is already scanning.

Policy 1: discard requests.

Policy 2: queue requests.

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The case study requirements

COORDINATION ISSUE



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Situation A: synchronous request

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Client 1 Laser Scanner

Three possible situations



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Situation B: asynchronous request

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Client 1 Laser Scanner




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Situation C: two or more asynchronous request

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Client 2 Laser ScannerClient 1




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Laser Scanner

Measures Buffer

Client 1

Sensor Component

Applicable for situations A and B - Direct interaction

High level solution A



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Laser Scanner

Measures Buffer

Client 2 Sensor Coordinator

Client 1

Sensor Component

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Applicable for situation C - Direct interaction

High level solution B



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SCANNING

IDLEBUSY

scan(from, nSteps, nScans)

"Ack"

"Done" &&

remScans > 0

"Done" &&

remScans = 0

Sensor Coordinator FSMPolicy 1



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SCANNING

IDLEBUSY

scan(from, nSteps, nScans)

"Ack"

("Done" AND remScans > 0)OR

("Done" AND remScans = 0AND pendingReq > 0)

"Done" ANDremScans = 0 AND

pendingReq = 0

scan(from, nSteps , nScans)

scan(from, nSteps , nScans)

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Sensor Coordinator FSMPolicy 2



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The implementation

scan(from, nSteps)

update(eventName)

request(from, nSteps, nScans)MeasuresBufferWriting



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The Sensor Coordinator ASMPolicy 1



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The use of two different frameworks for modeling and implementing computation and coordination:

Improves flexibility and reusability: we can modify the implementation without having to change the coordination and vice-versa.

We can reuse a simple composite into a bigger composite (hierarchical containment).

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Conclusions



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The use of two different frameworks for modeling and implementing computation and coordination:

Improves flexibility and reusability: we can modify the implementation without having to change the coordination and vice-versa.

We can reuse a simple composite into a bigger composite (hierarchical containment).

SCA and ASM promise good results also in robotics domain !!!

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Conclusions



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The research leading to the results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. FP7-ICT-231940-BRICS (Best Practice in Robotics).

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Thank you for your attention !!


a robotics task coordination case study€ degli studi di bergamo a robotics task coordination case...

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