Effective State Awareness Information is Enabling for System Prognosis Mark M. Derriso Advanced Structures Branch Air Vehicles Directorate Air Force Research Laboratory Workshop on Prognosis of Aircraft and Space Devices, Components, and Systems February 19-20, 2008 – Cincinnati, OH

2 Overview Workshop Topics:  “…In the future, the USAF would like to develop state awareness monitoring capabilities that could enable accurate prediction of the remaining service life and future performance capability of critical components as well as be used to take specific corrective actions to assure mission completion and minimize operating cost and risk.” This is Integrated Systems Health Management!

Determine Ability to Perform Mission Assess Damage Detect Damage

4 Critical Components Measurands Structural Health Management Controls Health Management Engine Health Management Electronics Health Management Sub-systems HM Data Multiple 0.02 inch Cracks in fuselage Flight Control Actuator Frozen at 20 degrees Bearing Spalling LRU is Malfunctioning Data Analysis Damage

5 System Performance Multiple 0.02 inch Cracks in fuselage Flight Control Actuator Frozen at 20 degrees Bearing Spalling LRU is Malfunctioning Data Analysis Vehicle-Level Health Status Altitude Mach CL max T max q max System Performance Bounds

6 Airframe Design MATERIAL STRUCTURE (Device, Component, or System) Materials Processing Manufacturing Materials Properties Loads, Boundary Conditions, Operational Environment UNCERTAINTY associated with each of these areas that propagates through to the system level Uncertainty_Total = U_material + U_manufacturing + U_operational

7 Design for Uncertainty Safe-life design The Safe-life design technique is employed in critical systems which are either very difficult to repair or may cause severe damage to life and property. These systems are designed to work for years without requirement of any repairs. Damage-tolerant design Damage-tolerant is the property that enables a system to continue operating properly in the event of the failure of (or one or more faults within) some of its components. If its operating quality decreases at all, the decrease is proportional to the severity of the failure F-4F-16

8 Failure Mode, Effects, & Criticality Analysis (FMECA)  FMECA  The objective of FMECA is to identify the components of products and systems most likely to cause failure, so that these potential failures can then be designed out.  FMECA allows the identification early in the product development process of potential problems or safety hazards which are inherent in a product design.

9 V&V of Airframe Design Structural Design Full- Scale Fatigue Testing Problem Areas Identified Front Spar Main Spar Rear Spar Closure Spar F-15 Wing Conduit Hole (hot spot) Inspection Schedule Constructed Airframe Prognosis: No Failures Throughout Design Life

10 Airframe Prognosis  However, requirements changes  Vehicles asked to perform different missions  Vehicles modified to fulfill new purposes  Vehicles asked to serve past original design life  What is the prognosis then?  Vehicle prognosis based on airframe prognosis

11 Operational Uncertainty External Loading External Loading maneuvers, gusts, taxi-loads maneuvers, gusts, taxi-loads Internal Loading Internal Loading bending, torsion, shear bending, torsion, shear Environmental Conditions Environmental Conditions temperature, humidity temperature, humidity All are Factors the Effects Fatigue Life

12 State Awareness  State awareness refers to knowledge regarding the current condition or capability  For airframe subsystems, state awareness is from the diagnostic portions of the structural health monitoring (SHM) system which detect, localize and assess any damage  State awareness allows subsystem prognosis which enables overall system prognosis

13 Definition of SHM  SHM refers to automated methods for determining adverse changes in the integrity of mechanical systems  SHM system capability is typically broken into the following levels of increasing difficulty:  damage detection  damage localization  damage assessment  life prediction diagnosis prognosis

14 SHM Development Process

15 SHM Development Framework Requirements and knowledge of structural behavior and loads Sensing technology and sensing system design + SHM System Design Ultrasonic wave propagation model Damage detection sensor Maintenance Benefit

16 State Awareness Architecture Measurands Data Analysis Reasonin g Process Experience & Knowledge Predictions (physics-based models, trending) Current State Information The Real World Based on Col Boyd’s OODA Loop Loads, damage, etc..

17 The ISHM Goal “I don't care about what anything was DESIGNED to do, I care about what it CAN do”.