Binocular Bilateral Controller: A Hardware Fault Tolerant Implementation

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Binocular Bilateral Controller A Hardware Fault
Tolerant Implementation
VLSI Testing

• Marylène Audet
• March 2001

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Agenda

• Goals
• The Binocular Controller
• Fault-Tolerant Designs
• Conclusion

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Goals

• Implement a binocular controller using eye
  movements model
• Design a fault-tolerant system
• Simulate and test the controller

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The Binocular Controller

• Conjugate Component (EC) average direction in
  which eyes are pointed
• Vergence Component (EV) angle subtended by two
  lines of sight
• EC 1/2 (ER - EL)
• EV (ER EL)

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The Binocular Controller (2)
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The Binocular Controller (3)
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The Binocular Controller (5)

• Digital Implementation requires delay insertion
• Slow Clock (order of KHz)
• 12-bit digitized Inputs
• All parameters shall be programmable via a CPU or
  switches
• Target technology is FPGA (Xilinx)

FOR MORE INFO...

• Ref Binocular Coordination Providing Stable
  Tracking and Rapid Reorientation Using A
  Bilateral Controller Inspired By Nature, Ross
  Wagner,PHD Thesis, McGill University, 1997

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Fault-Tolerant Designs

• Introduction
• MTBF
• Triple Modular Redundancy
• Self Purging Techniques
• Sift-Out Modular Redundancy
• Rollback Implementation or Time Redundancy
• Berger and Weight-Based Codes

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Fault-Tolerant Designs (2)

• Fault-tolerant Design are used in the Military
  and Aerospace, Medical, Banking, etc. industries
• Deep-submicron technology compensates low
  yields.
• Goal Very High Reliability measured using MTBF
  evaluations.
• Uses Concurrent Built-In Self-Test and
  Redundancy Techniques.

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MTBF

• MTBF Mean-Time Between Failures
• For example
• Processor of 100 Million Instruction Per Seconds
  (100 MIPS)
• Reliabiltiy Factor R(t) (0.9)12 -gt 1
  Failure/1012 Events
• MTBF (1012) (10-8) 10 000 Seconds 2.7
  Hours

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Triple Modular Redundancy

• As good as its Voter
• Voter must be Totally Self-Checking
• Redundancy cannot be tested off line -gt must have
  a way of disabling the redundant circuit
• High Area Cost
• Module Partitioning

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Self-Purging and Sift-Out

• Self-Purging Remove Faulty Path by Comparing
• Problem may require an exterrnal arbiter if
  there is a tie
• Requires feedback from Voter
• Sift-Out all decision done by controller but
  Voter is free from controller.

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Rollback Implementation

• Basics Checkpoints exists to fall-back
• Must have a state diagram detecting permanent
  faults
• Checker can be any encoder

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Error Coding Techniques

• Concurrent Checking / on-line.
• Checker detects 1-gt0 and 0-gt 1 Transitions
  Errors.
• Checkbits can be positional (Hamming) /
  non-positional (Berger) within the output vector
• Can assign a weight to each output.

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Conclusion

• Design Partitioning for Modular Redundancy
  Adders and Multipliers
• Checking Algorithm for Sift-Out Implementation
• Verify against analog counterpart.