Transcript Slide 1
Eastern Mediterranean University
Faculty of Engineering Department of Mechanical Engineering
Presented By:
Reza ABRISHAMBAF Faezeh YEGANLI
Agenda
Introduction IEC 61499 Function Block Holonic Manufacturing System Real-time Distributed Control System Reconfiguration of Real-time Distributed Control Case Study Application of Virtual Reality
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Introduction
• Manufacturing control systems are required to be adaptive and responsive.
• One approach which is closely related to the Multi-agent systems is HMS.
• The motivation is the requirement for manufacturing systems that can automatically and intelligently adapt to changes in the manufacturing environment while still achieving overall system goals.
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Introduction
• At the low control level of a HMS, especially at the level of real-time control, reconfigurable holonic controllers are employed (HCs).
• The critical issue for holonic control at this level is how the resources of the HMS are to be organized dynamically during runtime and how the associated controller components are to be reconfigured dynamically at the same time.
• Solution: Real-time distributed control system that can benefits of holonic control system.
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Introduction
• The real-time holonic distributed control systems require: Stability in the face of disturbance (i,e., Sensor or Robot Failure.) Adaptability and flexibility in the face of change.
Efficient use of available resource.
To do so, IEC-1499 Function block (FB) standard is employed.
Let’s have a look at PLC first!!
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Introduction
• A programmable logic controller (PLC) or programmable controller is a
digital computer
used for
automation
of mechatronic processes, such as control of machinery on factory assembly lines.
• Designed for Multiple Input Multiple Output (MIMO).
• Fixed I/O or Modular I/O
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Introduction
• SIEMENS S7-200, CPU 222.
• 8 Inputs, 6 Outputs.
• 256 Counters & Timers.
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Introduction
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IEC-61499 Function Block
• • A standardization project of IEC Technical Committee 65 (TC65) to standardize the use of
function blocks
in
distributed
measurement and control systems (IPMCSs).
industrial-process Work item approved 1991; assigned to Working Group 6 (WG6) 1993 – Experts from USA, Germany, Japan, UK, Sweden, France, Italy – Also responsible for IEC 61131-3 (Programmable Controller Languages) and 61131-8 (Programmable Controller Language Guidelines)
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IEC-61499 Function Block
• Distributed applications • Event and data interfaces • Software encapsulation and reuse • Event-driven state machines • Service interfaces • Management services • Software portability
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IEC-61499 Function Block
Centralized Programmable Configurable PLC IEC 61131-3
Thesis
agility!
distributability
Synthesis
Function Blocks IEC 61499
Antithesis
DCS IEC 61804 Distributed Configurable agility!
programmability dynamically reconfigurable = agile !
Common Architecture Reference Model distributed configurable programmable Prepared By: Abrishambaf, Yeganli
IEC-61499 Function Block
• • • • IEC 61499 is composed of 2 IECs standards: IEC-61131-3 and IEC 61804.
IEC-61131-3 is Centralized Programming Configurable (PLC) with Distributablity property.
IEC-61804 is Distributed Configurable with Programmibility property.
The result is Distributed Configurable Programmable which is common architecture reference model.
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• • • • • • •
IEC 61499
Parent organization
: IEC
Working group
: TC65/WG6
Goal
: Standard model (function blocks) for control encapsulation & distribution
Started
: 10/90
Active development
: 3/92
Trial period
: 2001-03
Completion
: 2005 • • • • • •
Holonic Manufacturing Systems (HMS)
Parent organization Working group
Consortium : IMS : HMS
Goal
: Intelligent manufacturing through holonic (autonomous, cooperative) modules
Feasibility study First phase
: 3/93-6/94 : 2/96 - 6/00
Second phase
Requirements Controls architecture
Intelligent Automation architecture
: 6/00-6/03
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IEC-61499 Function Block
Event inputs Event outputs Execution Control Chart Type identifier Algorithms
(IEC 1131-3)
Internal variables Input variables Output variables Prepared By: Abrishambaf, Yeganli
IEC-61499 Function Block
• • • • • • • Function Block is consist of two main parts: Head and Body.
The head of Function Block is Execution Control Chart (ECC) which organizes the flow of events between the blocks as well as the body control.
The body of Function Block consists of algorithm and the internal data as well as the I/O data.
The algorithm inside the body operates in IEC-61131-3 standards.
The body will control the resource communication and process mapping.
capabilities, scheduling, Events inputs and outputs are used to synchronize function blocks within an application and to schedule the algorithms within the function block.
Data inputs and outputs are the interface with the external of the function block since internal data is hidden.
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IEC-61499 Function Block
Function Block Execution Model
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IEC-61499 Function Block
1. Relevant data input values are made available.
2. The event at the event input occurs.
3. The execution control function notifies the resource scheduling function to schedule and algorithm for execution.
4. Algorithm execution begins.
5. The algorithm completes the establishment of values for the output variables associated with the event output.
6. The resource scheduling function is notified that algorithm execution has ended.
7. The scheduling function invokes the execution control function.
8. The execution control function signals an event at the event output.
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Holonic Manufacturing System
• • • • • Holon is an autonomous and cooperative building block of a manufacturing system for transforming, transporting, storing, and/or validating information and physical objects.
Holon Autonomy is the capability of a holon to create and control the execution of its own plans and/or strategies.
Holon Cooperation is the process whereby a set of holons develops mutually acceptable plans and executes them.
Holon Self-organization is the ability of holons to collect and arrange themselves in order to achieve a production goal.
Holarchy is system of holons that can cooperate to achieve a goal or objective.
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Real-time Distributed Control
(Definitions)
•
System:
A collection of devices interconnected and communicating with each other by means of a communication network consisting of segments • and links.
Device:
An independent physical entity capable of performing one or more specified functions in a particular context and delimited by its • interfaces.
Resource:
A functional unit having independent control of its operation, and which provides various services to applications including scheduling • and execution of algorithms.
Application:
A software functional unit that is specific to the solution of a problem in industrial-process measurement and control. An application may be distributed among devices and may communicate with other applications.
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Real-time Distributed Control
• • • • • A holon is represented by one or more hardware devices and can interact via one or more communication networks.
Each device comprises of one or more resources (i.e. processor with memory) and one or more interface.
Interfaces enable the device to interact with either the controlled manufacturing process or with other devices through a communication interface.
Resources are logical entities with independent control over their operations including the scheduling of their tasks.
A resource can be created, configured via management model.
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Real-time Distributed Control
• • • • Applications are networks of function blocks (FB) and variables connected by data and event flows.
Such applications aid the modeling of cooperation between the autonomous holons.
Function blocks receive event/data from interfaces, process them by executing algorithms and produce outputs, all handled by an event control chart.
Function block algorithms can be written in high-level programming language or in the IEC-61131 language for PLCs.
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Reconfiguration of Real-time Distributed Control
• In conventional PLC systems, reconfiguration involves a process of first editing the control software offline while the system is running, then committing the change to the running control program.
• When the change is committed, severe disruptions and instability can occur as a result of high coupling between elements of the control software and inconsistent real-time synchronization.
• Three types of reconfiguration: Simple configuration utilizes the IEC 61499 model to avoid software coupling issues during reconfiguration.
Dynamic reconfiguration uses techniques to properly synchronize software during reconfiguration.
Intelligent reconfiguration exploits multi-agent techniques to allow the system to reconfigure automatically in response to change.
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Reconfiguration of Real-time Distributed Control
The Reconfiguration Model
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Reconfiguration of Real-time Distributed Control
• Function block ports (i.e., event and data connections) are objects that register with the Resource Manager (RM) associated with the function block.
The resource manager looks after the interconnection of function block ports (i.e., as is specified by the application) and maintains a record of all function block ports in a FB Port table.
• The Device Manager (DM) looks after the interconnection of the RM’s function block ports and stores this information in an RM Port table.
• Application Manager (AM) looks after the interconnection of the DM’s function block ports and stores this information in a DM Port table.
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Reconfiguration of Real-time Distributed Control
• The advantage of this approach is that reconfiguration can be managed at various levels (i.e., function block, resource, device, application); all that is required is a “map” of the new configuration (i.e., based on the FB, RM, and DM Port tables).
• This approach allows for the “basic reconfiguration” discussed previously, but does not yet address how dynamic and intelligent reconfiguration are performed.
• The fundamental difference between basic and dynamic reconfiguration is the latter’s recognition of timeliness as a critical aspect of correctness.
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Reconfiguration of Real-time Distributed Control
• Intelligent reconfiguration builds .on dynamic reconfiguration (i.e., timeliness constraints) by focusing on multi-agent techniques to allow the system to reconfigure automatically in response to change.
•For example, as part of a fault recovery strategy, higher-level agents will manage the reconfiguration process using diverse or homogeneous redundancy.
•Two approaches to achieve these more advanced forms of reconfiguration: Preprogrammed or “contingencies” approach.
Softwiring approach.
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Reconfiguration of Real-time Distributed Control
Contingencies Approach
• Contingencies are made for all possible changes that may occur.
• Alternate configurations are pre-programmed based on the system designer’s understanding of the current configuration, possible faults that may occur as well as possible means of recovery.
Disadvantages:
• Inflexibility particularly with respect to the handling of unanticipated changes.
• This approach would require constant maintenance in order to keep the reconfiguration tables up to date.
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Reconfiguration of Real-time Distributed Control
Soft-wiring Approach
• FB, RM, DM port tables are connected to the Configuration Agent (CA).
• This agent has information of how two FB, RM or DM can be connected.
• CA will use this information, for example, to connect a new function block with an existing function block or to replace an existing one with a new while ensuring that the real-time requirement are met.
Advantages:
• It’s potential to overcome the inflexibility • It’s potential to realize intelligent reconfiguration.
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Case Study
System 1 Conveyor 5-joints Robot Barcode Reader Infrared Sensor
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Case Study
• System 1 contains Conveyor, Robot, Barcode Reader and Sensor.
• At the beginning of the conveyor, there is a switch. When a part touch the switch, the conveyor will start.
• When a part comes to the system, it will be moved by conveyor. There is a barcode reader will read the code of the part.
• Depending on the code of the part, the Robot will put it in either Machine 1 or Machine 2 or to the Conveyor 2 of the system 2.
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Case Study
System 2 Conveyor Color Sensor 5-joints Robot Pneumatic Robot Infrared Sensor
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Case Study
• System 2 contains Conveyor, Robot, Pneumatic Robot, Color Sensor and Infrared Sensor.
• The system waits until a part from system 1 arrives.
• When infrared sensor detects a part, the conveyor will start.
• Part will be moved till the color sensor, beside the color sensor, we have pneumatic robot that will take the part or it will be moved until the infrared sensor detects it.
• By detecting with infrared sensor, the robot will take and put the part in another machine.
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Case Study (Reconfiguration)
Adding a Robot
Cell 2 Configuration Agent CA Cell 1 Robot
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Methods of Adding a Robot
• To use the common method (Offline Mode).
• To use the predicted table.
• To use the IEC 61499 FB Standard.
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Adding a Robot
• The aim is to add one Robot the system.
• Cell 1 & Cell 2 have their own Function Blocks (FB1, FB2,….).
Function blocks will have information on how they can be connected (i.e., their interfaces) that is stored by CAS. The CAS will use this information
,
for example, to connect a new function block with an existing function block or to replace an existing function block with a new one while ensuring that the application’s real-time requirements are met during the reconfiguration process. The primary advantage of this approach is its potential to overcome the inflexibility of the contingencies approach as well as its potential to realize intelligent reconfiguration.
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For example, if the request for a new configuration requires upgrading an application to include more sophisticated functionality, and the device does not have sufficient processing resources for this upgrade, the new functionality may have to be out-sourced.
Moreover, even if the execution of the function with the blocks’ tasks are consistent device’s schedule and equipment, the device actor might still decide to out-source some or all of the new configuration’s tasks. For example, this redistribution may be done to save some of the available resources for executing tasks associated with a configuration that is currently under negotiation with the user.
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Application of Virtual Reality
In this section three simulation softwares will be presented.
Virtual Reality Rockwell Simulation Model MAST (Manufacturing Agent Simulation Tool)
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Application of Virtual Reality
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Application of Virtual Reality
• The Design Environment includes the Multi Agent System Model.
• The agents are AGVs, Robots, Conveyor,… • The messaging system is based on JAVA/JADE.
• What if each agent is defined based on IEC 61499 Function Block?
FB Conveyor FB AGV FB Robot
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Application of Virtual Reality
Proposed Multi Agent System Based on IEC 61499 Configuration Agent Header Body AGV Header Header Body Robot Body Conveyor
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Application of Virtual Reality
• The agents are defined based on IEC 61499 FB.
• The headers of Function Blocks are connected to the Configuration Agent.
• The Configuration Agent (CA) contains the status of each Function Block and the connection among them.
• This configuration system can be based on JAVA/JADE or other high level languages.
• In case of device failure, since CA has the status of the FBs, it can substitute another device instead.
• The whole system is in the Design Environment.
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Application of Virtual Reality
A holon is represented by one or more hardware devices, and can interact via one or more communication networks. Each device comprises of one or more resources (i.e., processor with memory) and one or more interfaces.
Interfaces enable the device to interact with either the controlled manufacturing process (via a process interface) or with other devices through a communication interface.
Resources are logical entities with independent control over their operations including the scheduling of their tasks. A resource can be created, configured etc (as part of the system ’s life-cycle) via a management model.
Prepared By: Abrishambaf, Yeganli
Application of Virtual Reality
Applications (software functional units spanning one or more resources and over one or more devices) are networks of function blocks (FB) and variables connected by data and event flows. Such applications aid the modeling of cooperation between the autonomous holons. Function blocks receive event data from interfaces, process them by executing algorithms and produce outputs, all handled by an event control chart.
Function blocks’ algorithms can be written in either high-level programming languages (e.g., C++) or in the IEC 61 131 languages for programmable controllers (e.g., Ladder Diagrams, Structured Text). A distribution model controls how applications are decomposed while ensuring that every function block is an atomic unit of distribution.
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Application of Virtual Reality
Another Simulation proposed by Rockwell Co.
Model It represents a new approach to the manufacturing oriented agent based control and simulations that enables the integration of agents with the currently used industrial control hardware architecture and simplifies the transfer of the agent-control developed initially for simulation purposes to the actual physical control.
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Application of Virtual Reality
•
Physical Process:
is the physical entity like AGV, Robot.
•
PLC:
contains Data Table which has the status of each physical entity in the Tags(A1_tagA, A1_tagB).
•
Agent Control:
contains the corresponded Physical Component Agent.
•
Emulation:
used to simulate the system , like Matlab, Arena.
•
Visualization:
providing graphical view of the system.
• By the combinations of the mentioned blocks, an Agent Based Simulation System will be obtained.
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Advantage of Virtual Reality
• One of the important advantages of such a real time system is that the system can be reconfigured online.
For instance, when a new sensor is added at runtime to the conveyor based transportation system, a set of new elements are dynamically created and added to corresponding subsystems sharing the data-table: the sensor agent is added to the agent control part, the sensor emulation unit is added to the emulation subsystem and the sensor visualization element is added to the visualization module. Concurrently, the tag values corresponding to the state of the sensor are added to the data-table to be shared by these new elements.
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Advantage of Virtual Reality
Another Advantage: The important feature of the proposed interface is smooth shift of the control functionalities from the agent based simulation towards the real-life control.
It allows replacing of the emulation subsystem with the real physical manufacturing equipment by preserving the same tag names referring to the sensor and actuator values. Thus it is not necessary to do any modifications in the agents or in the visualization subsystem.
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Application of Virtual Reality
MAST (Manufacturing Agent Simulation Tool)
As result of the research effort under the Intelligent Manufacturing Systems (IMS) framework Rockwell Automation in cooperation with different partners has designed and developed MAST (Manufacturing Agent Simulation Tool) a graphical visualization tool for multi agent systems. The main target is the materials handling domain and it is built on the JADE standard FIPA platform. In MAST, the user is provided with the agents for basic material handling components as for instance manufacturing-cell, conveyor belt, diverter and AGVs. The agents cooperate together via message sending using common knowledge ontology developed for material handling domain.
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Application of Virtual Reality
MAST (Manufacturing Agent Simulation Tool)
MAST represents the state of the art in graphical simulation tools for modeling and simulation of multi agent systems in manufacturing control, however and due to the fact that only material handling systems are targeted the tool does not cover complex application from a 3-D geometric viewpoint such as the robotic manipulation.
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Advantage of Virtual Reality
Virtual Reality in Real-time system:
1. Solving problems before being employed in practical manufacturing.
2. Preventing costly mistakes.
3. Online analysis of reconfiguration before being engaged to the reality.
4. De-centralized manufacturing control architecture.
5. MAST & Rockwell Model are simulation models, it means that there is no re-configurability control, performed.
however in VR reconfiguration can be
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Advantage of Virtual Reality
One of the most important advantage of VR in real time is online analysis.
For instance, in a system, one robot needs to be reconfigured. With the help of function block, the reconfiguration can be performed in real time, however what if this reconfiguration is inconsistent with the system. By using virtual reality, the reconfiguration in virtual environment can be performed to observe any inconsistency.
Another example can be the addition of a sensor. Recall that adding a physical entity would require a new function block. This new function block will be added using Configuration Agent. In VR this sensor will be added to the system to see how the other parts will adapt their selves to this new configuration. If a resource is not be able to adapt itself to new configuration, there will be failure in whole system.
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References
Brennan, R.W.
Holonic
Fletcher, M.
Manufacturing
Norrie, D.H.
Systems
”, ”
Reconfiguring Real-Time
Proceedings of the 12th International Workshop on Database and Expert Systems Applications, Page 611, 2001
.
Vrba, P.
Marik, V.
control systems
”, , “
Simulation in agent-based manufacturing
2005 IEEE International Conference on Systems, Man and Cybernetics, page(s): 1718- 1723 Vol. 2, Oct. 2005.
Xiaokun Zhang Norrie, D.H. Brennan, R.W. Yuefei Xu,
“A multi-level reconfiguration control for holonic
PLC” , 2000 IEEE International
Conference on Systems, Man, and Cybernetics, page(s): 1762-1767 vol.3, 2000.
Xiaokun Zhang Sivaram Balasubramanian Robert W. Brennan Douglas H. Norrie,
“Design and implementation of a real-time holonic control system for
manufacturing”, Information Sciences—Applications: An
International Journal, Volume 127 , Issue 1-2 (Aug. I 2000).
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References
M.Bal, M. Hashemipour,
“Applications of Virtual Reality in Design and Simulation of Holonic Demonstration in Die-Casting Manufacturing Industry”
,
Systems: A
Proceedings of the 3rd international conference on Industrial Applications of Holonic and Multi Agent Systems: Holonic and Multi-Agent Systems for Manufacturing, Pages: 421 – 432, 2007.
Rockwell Automation Company,
Application Note
”, “
IEC 61499 Function Block Model:
www.isagraf.com
, April 2008.
James
Concepts
H.
Christensen,
and R&D “The IEC Resources”, 61499 Standard:
http://www.rockwell.com
http://www.holobloc.com
.
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