FAULT TOLERANCE TECHNIQUE USED IN SEAWOLF SUBMARINE

1
FAULT TOLERANCE TECHNIQUE USED IN SEAWOLF
SUBMARINE
FAULT TOLERANCE TECHNIQUE EMPLOYED BY SEAWOLF
SUBMARINE
VIDYADHAR R EE 585 FAULT TOLERANT COMPUTING
2
SEAWOLF SUBMARINE (SSN 21)

• Nuclear powered fast
• attacking submarine.

INSIDE VIEW OF SEAWOLF SUBMARINE
3
SEAWOLF SUBMARINE

• State of the art Control system.
• Fault tolerant computer.
• Flat panel operator displays.
• Automatic modes of control.
• combat, gyrocompass inertial sensors and data
  distribution system.

4
SEAWOLF SUBMARINE (CONT)

• Hardware PM software operate on failing of ship
  control electronics, sensors and actuation
  systems.
• FL performed on maintenance computer for repair
  and restoration of full redundancy.
• PM software runs on 4 channel FTC, uses sensor
  voting.
• Runs real time diagnostic tests.
• PM transfers SCS functions to back-up systems.

5
SEAWOLF SHIP CONTROL DESCRIPTION

• Interfaces with SCS sensors, actuators using A/D
  signals processed by I/O modules.
• Operator interfaced by flat panel displays in SCP
  BCP.
• Redundant MIL-STD-1553 data buses connect
  displays with SCPU.
• Interfaces with ship combat, data distribution
  sys, gyro separate maintenance computer by
  means of redundant serial data buses.

6
SEAWOLF SHIP CONTROL DESCRIPTION (CONT)

• Bow planes position control actuation hardware
  also interface with SCPU for control.
• Redundant pressure sensors allow SCPU to serve as
  master source of ships depth.
• Controls rudder, stern plane steering diving,
  drain pumps.
• Interfaces with many valves and sensors for depth
  and remote trim pump control.

7
PERFORMANCE MONITORING (PM) FUNCTIONS

• PM steering and diving support.
• PM depth control support.
• PM trim and Drain support.
• FTC OS detects reconfigures it when failure
  occurs.
• Detection automatic recovery for ship ctrl
  failures.
• Also detects mechanical and hydraulic failures.
• Allows sys repair without shutting down entire
  system.
• Real time notification status display to
  indicate what part of ship control has failed.
• Designed to detect 98 of all failures.

8
FAULT LOCALIZATION (FL) FUNCTIONS

• Runs on separate maintenance computer when
  requested by the crew to diagnose physical
  location on failure.
• Indicates which component has to replaced when it
  is activated by the crew on occurrence of failure.

9
PM/FL DEVELOPMENT PROCESS

• The Seawolf PM/FL development process followed
  steps
• System analysis and hardware specifications.
• Definition of the overall approach to PM/FL.
• Detailed specification and design of PM software.
• Full system simulated failure testing.
• Ship installation and sea trials experience.

10
1. System analysis and hardware specifications

• Analysis process Req.
• PM must compare expected sensed position of
  surface and detect hydraulic failures.
• Req. feedback sensors, sensed position of servo
  valve, output I command signal from I/O
  module to minimize upset.
• Details of diving position control system and how
  PM must interact with Emergency Control System.

11
2. Definition of the overall approach to PM/FL

• A mid-value selection filter was used for
  masking, detecting and isolating failures of
  redundant sensor inputs.
• A state machine algorithm was chosen to detect,
  isolate failures retractable bow planes.
• Analog input PM applied to synchro sensors, and
  measured voltages from ships speed log and tank
  level sensors.
• Discrete input was applied to valve position
  limit switches and operator control switches
  located on SCP.

12
3. Detailed specification Design of PM/FL
software

• Development process was an iterative one.
• The req. were tailored to follow an algorithm
  which reduced run time and complexity the most.
• Tests were conducted with software running on
  actual target hardware, but interfaced with
  simulated I/O signals.

13
4.Full system simulates failure testing

• With testing done, PM was integrated with actual
  ship
• control operating system.
• The ship control machinery and submarine were
  simulated.
• Over 1000 simulated failures were formally
  tested.
• The test discovered PM software problems and
  several SCPU hardware deficiencies.

14
5.Ship installation sea trials experience

• As simulates testing of the system
• proceeded, the SCS was being
• installed on the SSN 21.
• PM correctly located faulty wired sensors and
  installation and rigging problems with the ship
  control machinery.
• Tests of all rudder and diving planes worked
  correctly during both dockside and at-sea tests.
• Utility of PM surface prediction was also
  demonstrated.

15
BENEFITS OF PM/FL

• Enhances mission effectiveness of the submarine.
• Capable of reducing required crew members and
  training.
• Reduces required maintenance and operating costs.
• System can tolerate a second failure in the same
  area and still retain full functional capability.
• Out of stock, does not result in aborting a
  mission, the system is robust enough for repair
  at a later convenient time.
• Automatic retest of system after Maintenance
  computer accurately indicates which component
  must be replaced to restore full system
  redundancy.
• PM automatically halts further operation of
  machinery when it detects potential damage of
  equipment due to incorrect operation of some
  machine.

16
FUTURE SUBMARINE PM/FL

• The following trends may shape the design of
  future systems
• Seawolf SCS is an evolutionary design towards
  full fly-by-wire submarine control systems. This
  leads to elevation of PM functions to higher
  levels of criticality and making them integral to
  the safety of the system.
• Drive for fully automated completely fault
  tolerant systems that can operate with minimal
  crew involvement that require minimal sea
  maintenance.
• Applying fast developing technologies of Fuzzy
  logic and Adaptive fuzzy logic for performing FL
  in real time.

17
ADVANCED CLASS OF SUBMARINES
18
REFERENCES

• http//www.navsource.org/archives/08/080021.htm
• http//www.fas.org/man/dod-101/sys/ship/ssn-21.htm
  
• http//www.wikipedia.com

19
QUERIES???