Design of a Multi-Threaded Distributed Telerobotic Framework

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Design of a Multi-Threaded Distributed
Telerobotic Framework

• Mayez Al-Mouhamed, Onur Toker, and Asif Iqbal
• College of Computer Science and Engineering
• King Fahd University of petroleum and Minerals
• Dhahran 31261
• Kingdom of Saudi Arabia

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OUTLINE

• Background on Telerobotics
• A multi-threaded distributed framework
• Telerobotic server components
• PUMA component
• Force component
• Component hierarchy
• Integrated scheme
• Telerobotic client components
• Integrated scheme
• Multi-threaded distributed telerobotic system
• Conclusion

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Background on telerobotics

• Telerobotics is an approach that extends a human
  operators sensing and manipulating capabilities
  to a remote environment.
• Telerobotics has numerous applications in
  hazardous or hostile environments.
• The purpose of this work is to design a reliable
  and efficient man-machine interface between a
  slave arm (robot) and a master arm over a network
  which preserves a large degree of operator
  dexterity.
• Computer vision and force feed techniques are
  implemented to enhance the maneuverability of the
  operator by providing him force feeling.
• To avoid communication delays in frequently
  interacting telerobotic systems, the operator
  will have a library of local automation tasks.
  Only coarse operator supervision is required.
  For example, picking up a tool, moving tool to a
  certain location, returning tool to initial
  position, etc.
• Telerobotics is a multidisciplinary area
  integrating knowledge from robotics, real-time
  operating systems and programming, network
  programming, 3D stereo vision, mechanical linkage
  engineering, ergonomics, etc.

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A Multi-Threaded Distributed Framework

• Client-Server distributed component telerobotic
  system.
• A telrobotic server has components (PUMA, Force
  Sensor, and Decision Server) and interfaces
  (Proxy Robot, Sensor, and DecisionServer).
• One or more telerobotic client components
• An integrated scheme of client-server components
• A multi-threaded distributed telerobotic system

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Telerobotic server components

• PUMA Component
• Acts as a software proxy (thread) of the slave
  robot arm diagram.
• Public methods
• ConnectRobot,
• InitializeRobot,
• incremental joint and Cartesian motion commands,
• tool and world frame motion coordination, etc.
• Public properties
• Booleans that represent robot state.
• Public Events
• motion commands
• communication and synchronization mechanisms.

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PUMA component
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Telerobotic server components

• Force Sensor Component
• A service thread for a wrist force sensor
  attached to slave robot arm (3 force3 moments)
• Provides reflected force feedback from slave arm
  (server) to operator (client)
• Public properties
• start and stop reading
• TimerValue, etc.
• SensorThreadPriority,
• Real-time streaming of force data from server to
  client

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Component hierarchy
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Integrated scheme - server
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Telerobotic Client Components

• Client GUI (Graphic User Interface) for remote
  testing and maintenance operations
• IDecisionServerto interface to server through
  .NET Remoting
• All the definitions to execute methods on PUMA
  and ForceSensor components
• After initialization, the client carries an
  empty un-referenced copy of IDecisionServer
• Following the network connection, the client can
  reference any instance of DecisionServer

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Integrated scheme - client
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Integrated Scheme of Client-Server Components

• Inherits DecisionServer from IDecisionServer,
  IProxyRobot, IForceSensor interfaces
• To invoke DecisionServer events, Shim Classes are
  used as agents to forward DecisionServer events
  to client.

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A Multi-threaded distributed Telerobotic System

• Simultaneous activation of many threads like
• Two digital cameras generate stereo pictures
  which are sent to the client
• Grabbing and transfer of stereo video data
• Reading and transferring force sensor data
• Sending and receiving robot control signals over
  the LAN to one or more clients
• Both the stereo data and the distributed
  component calls share the same LAN using
  different ports for data transfer

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Integrated system

• DecisionServer component provides slave
  supervisory control.
• Server Side Interfaces and .NET Remoting
• A set of definitions of public methods and
  properties.
• Servers as a contract for any component that
  implements this interface.
• Allows hiding the actual component to increase
  security.
• Uses IProxyRobot and IForceSensor to communicate
  with PUMA and Force Sensor components
• IDecisionServer inherits both of the above
  interfaces.
• Allows defining a unified set of methods,
  properties, and events within DecisionServer
  component.
• .NET Remoting publishes an instance of
  DecisionServer component on the LAN.
• .NET Remoting enables access to remote objects
  using SOAP.

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Events forwarding using Shim classes
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Server system of distributed framework
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Client system of distributed framework
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Conclusion

• A reliable and efficient man-machine interface
  between a slave robot (server) and a master arm
  (client) over a network while preserving some
  degree of operator dexterity
• A reliable distributed components (.NET
  Remoting) is implemented
• Software reusability, ease of extensibility,
  debugging, and data Encapsulation
• Advanced software tools like .NET Framework
  (comp. to DCOM)
• The components communicate using .NET Remoting
  and SOAP
• Automatic handling of network resources and data
  transfer
• Isolation of components from network protocol
  issues
• Enhances data security as well as facilitates
  deployment
• Multi-threaded execution for multi-streaming of
  force, command and stereo data.