Towards a Safe & Reliable Operation of Cyber Physical Systems · Towards a Safe & Reliable...

1Approved For Public Release. Case Number: 88ABW-2011-0408

Towards a Safe & Reliable Operation of

Cyber Physical Systems

02 Feb 11

Ken Eizenga

Air Vehicles Directorate

Air Force Research Laboratory

22

Overview

CHALLENGE: An autonomous air vehicle / system (UAS)

MUST maintain a high level of Safety

Cyber Physical Systems

HealthFault

Tolerance

Certification

UAS

33

An Integrated Approach to CPS

MISSION FLIGHT CONTROL

ADAPTION

VEHICLE CONTROL

SENSING

HEALTH

Certifying a CPS that includes:• Integrated System Health Management (ISHM)• Adaptive Guidance & Control (AG&C)

Integrity

Integrity

4

ISHM Architecture Approach

Orient, Decide

Centralized VehicleHealth Processing

Health Capability Reasoner

Information Management System

ISHM: Detect Damage, Assess Damage, Determine Ability to Perform Mission

Act

Ground Support

Vehicle Management System

Adaptive Guidance & Control

On-board data

Off-board data

OODA Loop

Observe

S

Events

&

Health Data

Flight Controls

Structures

Propulsion

Avionics

DACUDACU

55

ISHM Technical Challenges

• Determine the current health capability of the vehicle through the onboard, real-time analysis of sensor information

• Implement performance constraints for real-time mission management

• Integration of mixed criticality systems

• Specifying ISHM requirements for early design cycle and systems engineering involvement to ensure system integrity and design for integration

6

ISHM

Adaptive Guidance

System

Trajectory Command Generation

Reconfigurable Control System

Adaptive Guidance & Control (AG&C)

AG&C Approach

AG&C Definition

• A flight control algorithm that stabilizes and controls the flight vehicle in real time in accordance to its updated health capabilities

• Uses ISHM real-time outputs

• Modifies actuator commands and flight trajectory according to its health capabilities to enhance safe operation in the event of failures

77

Technical Challenges

• Real-time modeling of vehicle dynamics under failures and degradation

• Real-time computation of vehicle constraints and flyable envelope

• Full envelope, integrated adaptive guidance and control law for all flight segments

• Verification, validation, certification of an adaptive, reconfigurable guidance and control algorithms

AG&C Technical Challenges

8

ISHM-AG&C Application

VMS/AG&C/IMSHealth Reasoner

Monitors Components

Detects Failures & Projects Remaining Life

Triggers Flight Control Adaptation

AG&C

adapts

surfaces

Take-off

& climb

Return

Landing Approach

Actuator

holds load

Actuator

maneuver

loads

Change

maneuvers

Load

Rate

Cruise

Objective: Utilize Health Diagnosis for Real-Time Fault Tolerance to Enable Continued Mission Op’s

Motor

capability

decrease

Motor

shortMotor

heats up

ISHM

determines Act

RUL &

capability

9

Designing for Certification…

Focus Areas…as applied to ISHM•Composable Architecture

•Modular, pre-certified building blocks to increase reuse and speed up design

•System Partitioning•Time and space separated software and data with explicit and well-defined communication between partitions

•Advanced Analysis Techniques•Formalize design requirements to facilitate the use of formal methods and code analyzers

•Integrity Management•Analytical redundancy to determine soundness of data from sensors and subsystems

10

Challenges in Certification

Non-deterministism drives Complexity Explosion

As applied to ISHM•Proving the reliability/correctness of data from sensors and subsystems•Trusting the decision on performance capabilities of system by algorithms•Proving the system latency will not impact vehicle safety

As applied to AG&C•Proving stability margins for attitude after control change•Proving convergence time to allow for real-time, safe adaptation

V1 V2 V3 V4 V5 V6 V7

System Complexity

1111

Summary

An autonomous Cyber Physical System

MUST

maintain a high level of Safety

Health

• ISHM allows us to know the currenthealth status of the system andpredict future health status

Fault Tolerance

• Subsystems can utilize ISHM data to adapt in real-time to failures and changing conditions

Certification

• Certification enables trust in safe, adaptable systems

HealthFault

Tolerance

Certification

UAS

1212

Upcoming Events

• Safe & Secure Systems & Software Symposium (S5)

– Dates: 14-16 June 2011

– Place: Dayton, OH

– Save the date email sent in Jan

• ISHM Conference

– Dates: 19-21 Jul 11

– Place: TBD (likely Boston)

1313

Contacts

• ISHM

– Ken Eizenga, 937-255-6290

Kenneth.Eizenga@wpafb.af.mil

– J.B. Schroeder (ISHM Conf), 937-255-8431

John.Schroeder@wpafb.af.mil

• AG&C

– Dr. Anhtuan Ngo, 937-255-8439

– Anhtuan.Ngo@wpafb.af.mil

• Design for Certification

– Russ Urzi (S5 Symposium), 937-255-8294

– Russell.Urzi@wpafb.af.mil