Small Probabilities but Big Problems in Reliability and Safety Engineering: Past, Present, and Future Perspectives

1. Keynote Address at theInternational Conference on Reliability and Safety 2008INCRESE 2008, Udaypur, India SOME FLASH-BACKS AND FLASH-FORWARDS Or Small Probabilities but Big Problems Chanan Singh, Fellow IEEE Regents Professor & Irma Runyon Chair Professor Department of Electrical & Computer Engineering Texas A&M University College Station, TX 77843

2. Some Flash-backs

3. SMALL PROBABILITIES BUT BIG PROBLEMS – My First Encounter My first encounter with small probabilities but big problems in mid 70s: Reliability assurance of an automated, driverless, magnetically levitated ,linear induction motor driven transit/transportation system. Lesson learnt : reliability modeling and calculations are a serious business – not a contractual formality to be fulfilled.

4. Areas of Emphasis During 70s • Non-repairable systems – mission oriented • In general reliability, Sandler’s book was perhaps the only one dealing with repairable systems. • Work was also going on in power systems and computer systems reliability – also repairable systems. • These developments were mostly disconnected from each other.

5. Some Portals of Development • General reliability theory – IEEE Transactions on Reliability & RAMS • Defense and Aerospace • Power systems • Computer systems • Nuclear systems safety • Software reliability

6. Phases in Reliability Program • Reliability Assurance Program Plan • Design • Reliability modeling and prediction • Design evaluation and modifications • Implementation • Testing/Demonstration

7. Contributions to the State of Art • Reliability program plans – defense and aerospace industry. • Testing, demonstration etc – defense and aerospace industry. • Modeling – major contributions from power systems, computer systems and nuclear systems safety. • The reason is complexity and perhaps non-testability of such systems.

8. Present • Reliability and safety engineering have reached a certain level of maturity and are now part of the mainstream commercial product development rather than confined to defense and aerospace arenas. • Many organizations like IIT Kharagpur have been actively promoting this field. • Some of the terminology like MTBF, MTTR are now widely used by engineers. • Some engineers still have a hard time accepting probabilistic analysis. • The reason perhaps is that very few undergraduate programs teach anything about reliability and probabilistic methods in general. So they do not have the mental models to appreciate these concepts. • Calibration of indices is an issue – acceptable values of indices? • In some areas like power systems and nuclear systems, regulatory agencies are asking for probabilistic analysis. • With the increased complexity of systems, more people are turning to probabilistic analysis. • So I believe there is much future for the reliability and safety fields.

9. Flash-forwards: Some Opportunities and Challenges

10. Innovation and Reliability • This is the age of innovation. • Fast development and rapid implementation. • Little time for “Time Tested & True” or incremental reliability improvements. • Consumers are accustomed to high levels of reliability and expect high levels of reliability from future products and services • Innovation provides challenges and opportunities for reliability technology • Have not the reliability specialists always claimed the relevance of reliability technology to first time or one time developments. • Complexity poses special challenges for models and their validation

11. Multi-disciplinary & Inter-disciplinary • Future opportunities lie at the interfaces and major developments are expected to come from multi-disciplinary teams. • Reliability and safety engineering have always highlighted the importance of dealing with interfaces of hardware and hardware and software for potential problems. • These multi-disciplinary developments will provide far greater challenges and opportunities for reliability and safety engineering disciplines.

12. An Example • Consider safety analysis of a driverless train. • Mechanical and electrical technologies for friction and regenerative braking. • Communication between onboard computers and central computer. • Simple approach of fail-safe designs may be hard to apply in these complex systems. • Probabilistic modeling and analysis may be the only viable solution. • Reliability engineering needs to work with several disciplines to model the over all system.

13. Systems and Networks • Increased emphasis on systems and networks. • Reliability and safety issues with networks is assuming special importance. • One set of networks that have been extensively studied are perhaps the electric power networks. • This is perhaps because of their complexity and non-linearity. • Other examples of networks are computer and communication networks. • Inter-acting and interdependent networks pose difficult problems – for example interfaced power and communication networks.

14. Can a General Theory for Network Reliability be Developed • Various network models – in the order of difficulty of modeling and analysis: • simple connectivity models • capacitated network models • capacitated network models with additional driving characteristics • Most work reported in simple connectivity models of type 1. • Electric power systems use type 2 and 3 models. • Now computer communications networks may need to be modeled as 2 &3. • There is a need to develop a general theory for reliability type 2 and 3 models.

15. Models & Validations • Models of complex systems can be difficult to develop. • We need to examine all assumptions carefully as these models may have to be relied upon for making predictions without validation from physical observations (as opposed to simulation data). • How do we validate models of networks which are continuously changing? Examples- power systems.

16. Educational Aspects • US Model – broad education at the undergraduate level and specialization at the graduate level. • Asian Model – more specialized undergraduate education. • Education is a product that is supposed to last throughout the professional career. • Should provide maximum opportunities and ability to adopt to the changing environment.

17. Need for development of self reliance and self learning to adopt. • Needs of the individual and industry could be sometimes in conflict. • For the individual breadth of education and flexibility are important for access to maximum opportunities and potential. • For industry well trained individual to meet the present needs is important. Some industries do appreciate that that a well rounded education triumphs in the long run. • Educational institutions have responsibility to meet the needs of both, individual and the industry. • How should we educate for reliability engineering but at the same time providing maximum mobility and upward potential

18. In the past education has been a response to the needs of new technologies. • Technology is now changing so fast that this idea of education is being reexamined. • The engineers we produce now need to have the capacity for sustaining and even thriving through change. • Otherwise as the technology changes, employers will find new engineers to suit new technologies.

19. Our engineers need to be able to contribute to productivity as well as innovation. • How we translate this to curriculum needs to be examined for each discipline. • So the reliability engineering needs to examine this issue. By virtue of its systems approach, it should be able to provide many opportunities for advancement. • We do not want an engineer to be pigeon-holed or circumscribed by his education. • Instead we need to provide him with tools to be expansive and mobile.