Architecture and Mechanisms of Etherware for Cyber...

Architecture and Mechanisms of Etherware for Cyber-Physical Systems

Kyoung-Dae Kim and P. R. Kumar

Electrical and Computer Engineering and Coordinated Science Laboratory

University of Illinois at Urbana-Champaign

April 11, 2011

Outline

●  Networked Control Systems

●  Etherware : A Middleware for Networked Control Systems

●  Real-Time Enhancement of the Etherware

●  A Networked Inverted Pendulum Control System

2

Cyber-Physical System

●  Cyber-Physical Systems ○  Systems with computing, communication, and physical entities ○  Networked Control System (NCS)

●  Characteristics of NCS ○  Large scale ○  Openness ○  Time-critical ○  Safety-critical

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Challenges for NCS Development

●  Challenges for NCS Development ○  Platform heterogeneity ○  Clock offset and skew difference ○  Communication delay and packet loss ○  Support for continuous system evolution ○  ...

●  It is hard to develop a NCS application

●  Need for a well-designed Middleware for rapid, reliable, and evolvable NCS application development

4

Abstraction: Virtual Collocation

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Network

Supervisor

VisionServer

Controller

ProfileRegistry

VisionSensor VisionSensor Actuator


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Network

Supervisor

VisionServer

Controller

ProfileRegistry


Addressing Clock

Difference

Platform Heterogeniety

Network Programming

Unpredictable Communication


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Supervisor

VisionServer

Controller

ProfileRegistry


Middleware Supervisor

VisionServer

Controller

ProfileRegistry


Outline





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Etherware Architecture

●  Etherware ○  A Middleware for NCS developed at the University of Illinois

[Baliga’05, Kim’10] ○  For rapid implementation of a reliable and evolvable NCS application

●  Microkernel Architecture ○  Etherware Kernel ○  Components

●  Component-based Application Development

●  Message oriented Communication

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Message Delivery

●  Message Class ○  An XML document ○  Profile: Name of the Message Receiver

•  E.g., controller for car 1 ○  Content: Interaction semantics ○  Time Stamp: Time when Message is created

●  Etherware Kernel ○  Deliverable address lookup from Profile ○  Receiver Component gets executed when it receives a Message

Event-driven system

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KERNEL

Scheduler

Dispatcher

Sender Component Receiver

Component

Component Model

●  Software Design Patterns ○  Façade, Strategy, Memento

●  Provide Flexibility ○  Runtime replacement of Component Logic ○  Runtime externalization of Component State

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COMPONENT SHELL (FAÇADE)

COMPONENT LOGIC (STRATEGY)

Incoming Message

COMPONENT STATE (MEMENTO)

Outgoing Message

Etherware Services

●  ProfileRegistry ○  Map a profile (semantic name) to a deliverable address

●  NetworkMessenger ○  Maintain network connection between Etherware processes ○  Send/receive Message over network

●  NetworkTime ○  Estimate time differences between computing nodes ○  Translate timestamp in each remote message from remote time to local time

●  Notifier ○  Provide time-driven message, called Notification

13

MessageStream and Filter Mechanisms

●  MessageStream ○  1-to-1 communication channel between components ○  Ordered and unreliable communication

•  Useful for control applications

●  Filter ○  A mechanism for easy data collection ○  A Tap is created in a MessageStream to intercept messages

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Component 1 Component 2

Component 3

MessageStream and Filter Mechanisms

●  MessageStream ○  1-to-1 communication channel between components ○  Ordered and unreliable communication

•  Useful for control applications

●  Filter ○  A mechanism for easy data collection ○  A Tap is created in a MessageStream to intercept messages

15

Controller 2 Actuator 2

Controller 1 Actuator 1

CA Component

Outline



●  Real-Time Enhancement of Etherware


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Design for Temporal Guarantees

●  Message Delivery in Etherware ○  Non-concurrent ○  First In First Out (FIFO) order

●  Design Goal ○  Temporal Predictability ○  Flexibility

●  Hierarchical Scheduling Mechanism ○  Static classification at first stage ○  Dynamic ordering at second stage

17

Quality of Service (QoS) of Message Delivery

●  Quality of Service (QoS) ○  A collection of attribute that is used in scheduling for Message delivery ○  Period, relative deadline, absolute deadline, criticality of a Message

●  QoS Specification ○  QoS XML element in Message class ○  Message is scheduled based on the QoS specification and a scheduling policy

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Preemptive Concurrent Message Delivery

●  Concurrency ○  Dispatching Module: A set of Dispatchers

●  Preemption ○  Assign a fixed priority to each Dispatcher ○  Each Dispatcher has a prioritized job queue

●  Thread Scheduling Rule (TSR) ○  A policy for Dispatching Module configuration

DISPATCHING MODULE

Dispatcher 1

Dispatcher 2

Dispatcher 3

SCHEDULER COMPONENT

Message w/ QoS ?

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Preemptive Concurrent Message Delivery (continued)

●  Job Placement Rule (JPR) ○  A pair of attribute for linear ordering within Dispatching Module

●  Scheduling Policy ○  Map from a QoS specification to a JPR ○  JPR Implementation: An implementation of a specific scheduling policy

●  Interface for JPR Implementation ○  Independent of a specific scheduling policy

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Message w/ JPR

DISPATCHING MODULE

Dispatcher 1

Dispatcher 2

Dispatcher 3

SCHEDULER COMPONENT

Message w/ QoS

Hierarchical Scheduling Mechanism

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Message w/ JPR

DISPATCHING MODULE

Dispatcher 1

Dispatcher 2

Dispatcher 3

SCHEDULER COMPONENT

Message w/ QoS

JPR IMPLEMENTATION

If criticality = high, DISPATCHER 1 If criticality = middle, DISPATCHER 2 If criticality = low, DISPATCHER 3 … JPR = (DISPATCHER ID, current time + Period)

JPR Interface

QoS JPR

Outline





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An Inverted Pendulum Control System

●  Implementation Platform ○  Sun Java Real-Time System 2.0 with Solaris 10

●  System Configuration ○  DSP Program

•  Return encoder values upon request from Controller •  Deliver control command upon receive it from Controller

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Periodic Control under Stress

●  Periodic Controller Component ○  Period: 15ms ○  Execution priority: High

●  Stressing Component ○  Period: 1s ○  Avg. Execution time: 100ms ○  Execution priority: Low

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A Networked Inverted Pendulum Control System

●  Periodic Controller Component ○  Period: 15ms

●  DSPProxy Component ○  Intermediate interaction between Controller and DSP program

●  Request Component ○  Request runtime system reconfiguration ○  Controller upgrade ○  Controller migration

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Controller Upgrade

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Controller Migration

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Thank You !

Architecture and Mechanisms of Etherware for Cyber...

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