mas and soa: a c ase s tudy e xploring p rinciples and t echnologies to s upport s elf -p roperties...
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MAS AND SOA: A CASE STUDY EXPLORING PRINCIPLES AND TECHNOLOGIES TO SUPPORTSELF-PROPERTIES IN ASSEMBLY SYSTEMS
Luís Ribeiro ([email protected])
José Barata ([email protected])
Armando Comlombo([email protected])
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UNINOVAInstituto de Desenvolvimento de Novas Tecnologias
PRESENTATION OUTLINE Motivation
Systems, Paradigms and IT MAS and SOA System Componentization
Building Blocks NOVAFLEX Cell
Architecture A skill based approach Generic Services Device Level System Level
Implementation A generic communication Interface Interaction Patterns Test Scenario
Conclusions and Outlook2
MOTIVATION
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Market Turbulence
Profitable but volatile opportunities
Mass Customization
Safety and Environment
Sustainable Development
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Flexible, Bionic, Holonic and Reconfigurable Manufacturing Systems; Evolvable Assembly Systems, Evolvable Production Systems...
MAS
SOA Internet
Web Services
Agent Platforms
Web Standards
Neural Networks
Prospective Reasoning
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SYSTEMS, PARADIGMS AND IT (1) Current approaches will soon be insufficient The Systems advocated by modern production
paradigms are increasingly powerful, full featured and COMPLEX
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SYSTEMS, PARADIGMS AND IT (2)
Existing IT/AI are no adequate in the present Software Hardware
There is a lack of support tools Development Analysis
Is a new paradigm required? Understand existing paradigms and technologies Attempt to integrate/adequate them to fulfill emerging
requirements
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MAS AND SOA: BRIEF COMPARATIVE ANALYSIS
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Characteristics SOA MAS
Basic Unit Service Agent
Autonomy Both entities denote autonomy as the functionality provided is self-contained
Behaviour description
In SOA the focus is on detailing the public interface rather than describing execution details.
There are well established methods to describe the behaviour of an agent.
Social ability Social ability is not defined for SOA nevertheless the use of a service implies the acceptance of the rules defined in the interface description
The agents denote social ability regulated by internal or environmental rules
Complexity encapsulation
Again, the self-contained nature of the functionalities provided allows hiding the details. In SOA this encapsulation is explicit.
Communication infrastructure
SOA are supported by Web related technologies and can seamlessly run on the internet.
Most implementations are optimized for LAN use.
Support for dynamically reconfigurable run-time architectures
Reconfiguration often requires reprogramming
The adaptable nature of agents makes them reactive to changes in the environment.
Interoperability Assured by the use of general purpose web technologies.
Heavily dependent on compliance with FIPA-like standards.
Computational requirements
Lightweight implementations like the DPWS guarantee high performance without interoperability constraints
Most implementations have heavy computational requirements
COMPONENTIZATION - CONCEPT
Each device is provided an IT frontend
Harmonizes the devices with the infrastructure
Improves Flexibility and Scalability
Enables (re)composition of the system using building
blocks
Encapsulates complexity
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Each type of service (CLS, MDS and SMI) is generic for
a given family of hardware.
Each service provides generic processing and
information flow
Each service has a typical interaction pattern
COMPONENTIZATION - CONCEPT
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•Service to Machine Interface (SMI): wraps legacy devices harmonizing them with the remaining infrastructure
•Manufacturing Device Service (MDS): abstracts a manufacturing component: gripper, robot, conveyor, …
•Coalition Leader Service (CLS): aggregates and orchestrates MDSs
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COMPONENTIZATION – BUILDING BLOCKS
COMPONENTIZATION – NOVAFLEX CELL
Type of Service
Hardware
CLS Pallets, Station “Orchestrators”, Node “Orchestrators”
MDS Robots, Grippers, Tool warehouses, Conveyors, Conveyors, Routing Devices, Fixing Devices
SMI Bosch Controller SMI
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ARCHITECTURE – A SKILL BASED APPROACH
A skill is a action a that a given service knows how
to execute and therefore is able to offer to the
remaining system.
MDS offers simple skills – atomic skills
CLS offers complex skills – skills that are composed
of other skills
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ARCHITECTURE – SKILLS AVAILABLE IN NOVAFLEX’S GENERIC SERVICES
Type of Service
Device Skills
SMI Bosch Station “Interop” service
MDS Gripper grip, ungrip, get_lcp_list, get_lcp_item
Robot move, move linear, change speed, lockgripper, unlockgripper
Tool Warehouse store part, unstore part, get position to store part, get part position, confirm store, confirm unstore
Conveyor input part, output part
Fixing Device Fix pallet, unfix pallet
Routing Device Output part
CLS Coalition dependent
RobotMDS + gripperMDS -> Pick and PlaceRobotMDS + gripperMDS + Tool Warehouse -> Switch GripperConveyorMDS + RobotMDS + gripperMDS + Tool Warehouse -> produce watch…
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ARCHITECTURE – A PLUG AND PLAY RECONFIGURABLE ENVIRONMENT
To accomodate changing requirements the building blocks (SMI, MDS and CLS) can be (re)combined.
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IMPLEMENTATION - A GENERIC COMMUNICATION INTERFACE FOR WEB SERVICES (1)
Harmonizes the IT infrastructure
Supports Generic Ochestration
Supports Structured Interaction
Supports Runtime Changes
Minimizes Code Explosion and Complexity
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It is essential as services take diferent roles during functionning
IMPLEMENTATION - A GENERIC COMMUNICATION INTERFACE FOR WEB SERVICES (2)
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• Implements:▫Generic message structure▫Generic types of interaction
IMPLEMENTATION - A GENERIC COMMUNICATION INTERFACE FOR WEB SERVICES (3)
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IMPLEMENTATION – SERVICE TO MACHINE INTERFACE (SMI)
Interaction Pattern NOVAFLEX
Interoperates the Bosch SCARA controller privding acess to the robot, grippers and tool warehous
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IMPLEMENTATION – MANUFACTURING DEVICE SERVICE (MDS)
Interaction Patterns with/out SMI NOVAFLEX
Abstracts each device harmonizing them with the infrastructure
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IMPLEMENTATION – COALITION LEADER SERVICE
NOVAFLEX
•The pallet is the main Coalition Leader and ochestrates its way around the system•Each station has its own ochestrator (CLS) that according to the devices under the coalition offers diferent complex skils. For instance Stattion 2 provides pick and place and swicth gripper operations under the presence of the following MDS: robot, gripper and toolwarehouse
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TEST SCENARIO – RE-ORCHESTRATION AS A RECOVERY ACTION
Failure Scenario:
The pallet orchestrates its way until Station 2 where it requests the CLS a
pick and place operation.
When attempting to open the active gripper detects that is unable to perform
the operation. Upon diagnosing the fault and acknowledging that there is no
possible recovery within its scope, the gripper MDS reports it to the CLS.
The CLS checks in its diagnosis and recovery knowledge base if there a
specific handler for that fault and eventually identifies one.
For that specific gripper, a fault in step 2 of a pick and place operation can be
recovered by switching gripper. A conversation is initiated with the tool
warehouse.
The Gripper is replaced
The Pick and Place Restarts 23
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Despite the theoretical prospects and expectations, in practice technology requires further improvements to meet the IT requirements of modern production systems
Computational power is still a constraint in embedded tiny devices
SOA and MAS paradigms individually provide an incomplete solution
Experience shows that there are benefits in merging both concepts and technologies
CONCLUSIONS
OUTLOOKCurrently
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
NOVAFLEX
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
DPWS Service
Future
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