![Pathological Interaction
between RT and
synchronization protocols
Pathfinder caused repeated
resets, nearly doomed the
mission
Unexpected interactions
Incompatible Cross Domain
Protocols
[Sha]
• Landed on the Martian
surface on July 4th, 1997
• Unconventional landing –
boucing into the Martian
surface
• A few days later, not long
after Pathfinder started
gathering meteorological
data, the spacecraft
began experiencing total
system reset, each
resulting in losses of data](https://image.slidesharecdn.com/lecture2-intro-of-cps-230706071748-433822a8/85/lecture2-intro-of-CPS-pdf-27-320.jpg)
lecture2-intro-of-CPS.pdf
- 1. Lecture Note #2 EECS 571 Cyber-Physical Systems Kang G. Shin CSE/EECS The University of Michigan (drawn from many sources including lecture notes of Insup Lee at Upenn and Jack Stankovic at Uva)
- 2. What’s CPS?, H. Gill @NSF • Cyber – computation, communication, and control that are discrete, logical, and switched • Physical – natural and human-made systems governed by the laws of physics and operating in continuous time • Cyber-Physical Systems – systems in which the cyber and physical systems are tightly integrated at all scales and levels • Change from cyber merely appliquéd on physical • Change from physical with COTS “computing as parts” mindset • Change from ad hoc to grounded, assured development “CPS will transform how we interact with the physical world just like the Internet transformed how we interact with one another.”
- 3. What’s CPS? , cont’d • Integration of physical systems and processes with networked computing • Computations and communications are deeply embedded in, and interacting with physical processes to equip physical systems with new capabilities • Covers a wide range of scale (pacemakers to national power grid)
- 4. Computing in Physical Systems Body Networks Road and Street Networks Battlefield Networks Vehicle Networks Industrial Networks Building Networks Environmental Networks Open, Heterogeneous Wired & Wireless
- 5. CPS Characteristics • CPS are physical and engineered systems whose operations are monitored, coordinated, controlled, and integrated. • This intimate coupling between the cyber and physical is what differentiates CPS from other fields.
- 6. CPS Characteristics, H. Gill@NSF Some hallmark characteristics: • Cyber capability in every physical component • Networked at multiple and extreme scales • Complex at multiple temporal and spatial scales • Constituent elements are coupled logically and physically • Dynamically reorganizing/reconfiguring; “open systems” • High degrees of automation, control loops closed at many scales • Unconventional computational & physical substrates (such as bio, nano, chem, ...) • Operation must be dependable, certified in some cases.
- 7. Questions on CPS • Are CPS simply embedded systems on steroids? – Interact with the physical world – Constraints on cpu, power, cost, memory, bandwidth, … • Is the Internet just a LAN on steroids? • Confluence of the right technologies at the right time can result in – Fundamental paradigm shift – Totally new systems – Revolutionize business, science, entertainment, …
- 8. Confluence of Four Areas Real-Time Control Cost Form factor Severe constraints Small-scale Closed Scheduling Fault-tolerance Wired networks Noisy Sensing Large-scale Real-time/actuation Open Wireless Sensor Networks Embedded Systems Linear Adaptive Distributed Decentralized Closed Architecture Principles
- 9. Realistic (Integrated) Solutions • CPS must tolerate – Failures – Noise – Uncertainty – Imprecision – Security attacks – Lack of perfect synchrony – Scale – Openness – Increasing complexity – Heterogeneity – Disconnectedness
- 10. Challenges Arise • Assumptions underlying distributed systems technology has changed dramatically – New abstractions needed – Wired => wireless – Unlimited power => limited power – User interface (screen/mouse) => sensors/real world interface – Fixed set of resources => resources are dynamically added/deleted – Each node is important => aggregate behavior is important – Location unimportant => location is critical
- 11. New Theories • Compositional • Control Theory • Optimization • Real-Time • Integration Issues • Openness, Mobility, Uncertainty, Concurrency, Noise, Faults, Attacks, Self-Healing, etc.
- 12. CPS - Enabler for Dramatic Innovation • New global-scale, personal medical service delivery systems • New paradigms for scientific discovery • Smart (micro) agriculture • Towards the end of terrorism • Smart, networked vehicles • New generation Internet
- 13. Example: Automotive Telematics • In 2005, 30-90 processors per car – Engine control, break system, airbag deployment system – Windshield wiper, door locks, entertainment systems – Example: BMW 745i • 2,000,000 LOCs • Window CE OS • Over 60 microprocessors – 53 8-bit, 11 32-bit, 7 16-bit • Multiple networks • Buggy? • Cars are sensors and actuators in V2V networks – Active networked safety alerts – Autonomous navigation – …
- 14. Example: Health Care and Medicine • National Health Information Network, Electronic Patient Record initiative – Medical records at any point of service – Hospital, OR, ICU, …, EMT? • Home care: monitoring and control – Pulse oximeters (oxygen saturation), blood glucose monitors, infusion pumps (insulin), accelerometers (falling, immobility), wearable networks (gait analysis), … • Operating Room of the Future – Closed-loop monitoring and control; multiple treatment stations, plug and play devices; robotic microsurgery (remotely guided?) – System coordination challenge • Progress in bioinformatics: gene, protein expression; systems biology; disease dynamics, control mechanisms Images thanks to Dr. Julian Goldman, Dr. Fred Pearce
- 15. Example: Electric Power Grid • Current picture: – Equipment protection devices trip locally, reactively – Cascading failure: August (US/Canada) and October (Europe), 2003 • Better future? – Real-time cooperative control of protection devices – Or -- self-healing -- (re-)aggregate islands of stable bulk power (protection, market motives) – Ubiquitous green technologies – Issue: standard operational control concerns exhibit wide-area characteristics (bulk power stability and quality, flow control, fault isolation) – Technology vectors: FACTS, PMUs – Context: market (timing?) behavior, power routing transactions, regulation IT Layer Images thanks to William H. Sanders, Bruce Krogh, and Marija Ilic
- 16. Application Domains of Cyber-Physical Systems • Healthcare – Medical devices – Health management networks • Transportation – Automotive electronics – Vehicular networks and smart highways – Aviation and airspace management – Avionics – Railroad systems • Process control • Large-scale Infrastructure – Physical infrastructure monitoring and control – Electricity generation and distribution – Building and environmental controls • Defense systems • Tele-physical operations – Telemedicine – Tele-manipulation In general, any “X by wire(less)” where X is anything that is physical in nature. CPS Healthcare Finance … Transportation
- 17. Grand Visions and Societal Impact • Near-zero automotive traffic fatalities, injuries minimized, and significantly reduced traffic congestion and delays • Blackout-free electricity generation and distribution • Perpetual life assistants for busy, older or disabled people • Extreme-yield agriculture • Energy-aware buildings • Location-independent access to world-class medicine • Physical critical infrastructure that calls for preventive maintenance • Self-correcting and self-certifying cyber-physical systems for “one-off” applications • Reduce testing and integration time and costs of complex CPS systems (e.g., avionics) by one to two orders of magnitude
- 18. Key Trends in Systems • System complexity – Increasing functionality – Increasing integration and networking interoperability – Growing importance and reliance on software – Increasing number of non-functional constraints • Nature of tomorrow’s systems – Dynamic, ever-changing, dependable, high-confidence – Self-*(aware, adapting, repairing, sustaining) • Cyber-Physical Systems everywhere, used by everyone, for everything – Expectations: 24/7 availability, 100% reliability, 100% connectivity, instantaneous response, remember everything forever, … – Classes: young to old, able and disabled, rich and poor, literate and illiterate, … – Numbers: individuals, special groups, social networks, cultures, populations, …
- 19. Societal Challenge • How can we provide people and society with cyber-physical systems that they can trust their lives on? • Partial list of complex system failures – Denver baggage handling system ($300M) – Power blackout in NY (2003) – Ariane 5 (1996) – Mars Pathfinder (1997) – Mars Climate Orbiter ($125M, 1999) – The Patriot Missile (1991) – USS Yorktown (1998) – Therac-25 (1985-1988) – London Ambulance System (£9M, 1992) – Pacemakers (500K recalls during 1990-2000) – Numerous computer-related Incidents wth commer aircraft (http://www.rvs.uni-bielefeld.de/ publications/compendium/ incidents_and_accidents/ index.html) Trustworthy: reliable, secure, privacy-preserving, usable, etc.
- 20. R&D Needs Development of high-confidence CPS requires – Engineering design techniques and tools • Modeling and analysis, requirements capture, hybrid systems, testing … • Capture and optimization of inter-dependencies of different requirements • Domain-specific model-based tools – Systems Software and Network Supports • Virtualization, RTOS, Middleware, … • Predictable (not best-effort) communication with QoS, predictable delay & jitter bounds, … • Trusted embedded software components – To help structured system design and system development – To reduce the cost of overall system development and maintenance efforts – To support the reuse of components within product families – Validation and Certification • Metrics for certification/validation • Evidence-based certification, Incremental certification
- 21. Scientific Challenges • Computations and Abstractions – Computational abstractions – Novel Real-time embedded systems abstractions for CPS – Model-based development of CPS • Compositionality – Composition and interoperation of cyber physical systems – Compositional frameworks for both functional, temporal, and non-functional properties – Robustness, safety, and security of cyber physical systems • Systems & Network Supports – CPS Architecture, virtualization – Wireless and smart sensor networks – Predictable real-time and QoS guranattees at multiple scales • New foundations – Control (distributed, multi-level in space and time) and hybrid systems - cognition of environment and system state, and closing the loop – Dealing with uncertainties and adaptability - graceful adaptation to applications, environments, and resource availability – Scalability, reliability, robustness, stability of system of systems – Science of certification - evidence-based certification, measures of verfication, validation, and testing
- 22. Software, the Great Enabler • Good news: anything is possible in software! • Bad news: anything is possible in software! • It is the software that affects system complexity and also cost. – Software development stands for 70-80 % of the overall development cost for some embedded systems.
- 23. Embedded Software - Goals • Trustworthy: should not fail (or at least gracefully degrade), and safe to use. The existence of embedded software becomes apparent only when an embedded system fails. • Context- and Situation-Aware: should be able to sense people, environment, and threats and to plan/notify/actuate responses to provide real-time interaction with the dynamically changing physical environment with limited resources. • Seamless Integration: should be invisible at multiple levels of a hierarchy: home systems, metropolitan systems, regional systems, and national systems. • Validation and Certification: should be able to assure that embedded systems work correctly with respect to functional and nonfunctional requirements with high degree of certainty.
- 24. Software Research Challenges • Need new notions of “correctness” and “compositionality” – Factor in context of use, unpredictable environment, emergent properties, dynamism, interoperability – What are desired properties of and metrics for both software and systems (e.g., resource use) • Need new formal models and logics for reasoning about CPS – Uncertainty, physical world, mental model of human user – Hybrid automata, probabilistic logic • Need new verification/analysis tools usable by domain engineers – Push-button, lightweight – Integrated with rest of system development process
- 25. Interaction Complexity • We know how to design and build components. • Systems are about the interactions of components. – Some interactions are unintended and unanticipated • Interoperability • Emerging behaviors • “Normal Accidents”, an influential book by Charles Perrow (1984) – One of the Three Mile Island investigators – And a member of recent NRC Study “Software for Dependable Systems: Sufficient Evidence?” – A sociologist, not a computer scientist • Posits that sufficiently complex systems can produce accidents without a simple cause due to – interactive complexity and tight coupling
- 26. Potential Accidental Systems • Many systems created without conscious design by interconnecting separately-designed components or separate systems. – Unsound composition: the interconnects produce desired behaviors most of the time – Feature interactions: promote unanticipated interactions, which could lead to system failures or accidents • Modes of interactions – Among computation components – Through share resources – Through the controlled plant (e.g., the patient) – Through human operators – Through the larger environment • E.g., Medical Device PnP could facilitate the construction of accidental systems – blood pressure sensor connected to bed height, resulting in the criticality inversion problem
- 27. Pathological Interaction between RT and synchronization protocols Pathfinder caused repeated resets, nearly doomed the mission Unexpected interactions Incompatible Cross Domain Protocols [Sha] • Landed on the Martian surface on July 4th, 1997 • Unconventional landing – boucing into the Martian surface • A few days later, not long after Pathfinder started gathering meteorological data, the spacecraft began experiencing total system reset, each resulting in losses of data
- 28. Final Thoughts • Real-time issues, WSN issues, control issues should not be addressed alone • Connection to the physical world will be so pervasive that systems will be open even if you think they are not =>New abstractions and composition techniques needed.