Bridging the theory-practice gap through problem reformulation: a motion control case study

1. Bridging the theory-practice gap through problem reformulation: a motion control case study • Zhiqiang Gao, Ph.D. • Center for Advanced Control Technologies • Cleveland State University • June 24, 2004 www.cact.csuohio.edu

2. Outline • Introduction • The Theory-Practice Gap • An Experimental Science Approach to Control Research • Problem Reformulation • Conclusions 2

3. From Applied Research to Advanced Technologies Center for Advanced Control Technologies www.cact.csuohio.edu

4. CACT Mission • Define, Articulate, Formulate Fundamental Industrial Control Problems • Solutions and Cutting Edge Technologies • Performance and Applicability • Synergy in Research and Practice

5. Center for Advanced Control Technologies • FACULTY: • Dr. Zhiqiang Gao, Director of CACT, ACRL and AERL • Dr. Daniel Simon, Director of the Embedded Systems Laboratory in Electrical Engineering. • Dr. Paul Lin, Director of the 3D Optical Measurement Laboratory in Mechanical Engineering. • Dr. Yongjian Fu, Software Engineering • Dr. Sally Shao, Mathematics • Prof. Jack Zeller, Engineering Technology, 40 yrs+ experience, P.E.

6. Center for Advanced Control Technologies Doctoral Candidate Researchers: Frank Goforth Robert Miklosovic Zhan Ping Wankun Zhou Aaron Radke Chunming Yang Qing Zheng Sri Kiran Kosanam Masters Candidate Researchers: Eric Dittmar Bharath Endurthi Hrishikesh Godbole Sai Kiran Gumma Qing Guo Ivan Jurcic Srujan Kusumba Mike Gray Xiaolong Li Ramgopal Mushini Nuha Nuwash Tong Ren Bhavinkumar Shah Chirayu Shah Madhura Shaligram

7. Past Projects • Temperature Regulation • Intelligent CPAP/BiPAP • Motion Indexing • Truck Anti-lock Brake System • Web Tension Regulation • Turbine Engine Diagnostic • Computer Hard Disk Drive • Stepper Motor Field Control • 3D Vision Tire Measurement • Digitally Controlled Power Converter

8. Sponsors • NASA • AlliedSignal Automotive • Invacare Co. • Energizer • Rockwell Automation • Kollmorgan • ControlSoft • Black and Decker • Nordson Co. • CAMP

9. NASA Intelligent PMAD Project

10. Networked Power Converters

11. Case Study: Web Tension Regulation

12. Case Study: Truck Anti-lock Brake System

13. Case Study: Computer Hard Disk Drive

14. We build it, test it, and make it work.

15. We apply our research using our partner’s products.

16. We get results: Wavelet control for robust machines.

17. We get results: Advanced motor field control reduces cost.

18. We get results: Model Independent control design & tuning.

19. We write the software.

20. We have staff from the“School of Hard Knocks”.

21. It All Comes Down To Mathematics • Level of abstraction • Clarity in thinking • Theory and guidance

22. Theory vs. Practice A Historical Perspective

23. The Classical Control Era Control Practice Control Research Mathematics Control Theory

24. The Modern Control Era Control Practice Control Research Mathematics Control Theory

25. The transition did go quietly

26. 4/1964 IEEE Trans. Automatic Control Editorial “In recent years, there has been considerable discussion about the gap which appears to exist between control theory and its application…” “It appears that the problem of the gap is a control problem in itself; it must be properly identified and optimized through proper action…” AACC Theory and Applications Committee meeting, 3/24/1964 “Bridging the Gap Between Theory and Practice”

27. 4/1965 IEEE Trans. Automatic Control Guest Editorial by Harold Chestnut Proposed Solutions: • Company sponsored Education • Component Study by Universities • Promotion of Economic Incentives • Publication Policies • Definition of characteristics of systems and subsystems

28. 8/1967 IEEE Trans. Automatic Control Editorial by J.C. Lozier On panel discussions: “These panels, staffed with leading theoreticians, have automatically assumed that theory is ahead of practice, and they conclude that the solution lies in reeducating the designers. The establishment has spoken.” Suggestion in bridging the gap: stimulate • papers on general practice • papers on advanced engineering practice • a more hospital atmosphere where results are as important as methods

29. 2/1968 IEEE Trans. Automatic Control Announcement by John. B. Lewis • Special two day conference preceding JACC meeting • Responding to 65 and 67 editorials • Each session is “a complete case history necessarily brings together theory and practice” • “Demonstration of what can be achieved by applying control theory to major problems”

30. 12/1982 IEEE Trans. Automatic Control Editorial by Y.C. Ho • “Control” as experimental science (the 3rd dimension w.r.t. the gap) • Experiment vs. Application (detective vs. craftsman) • The “observation-conjecture-experiment-theory-validation” paradigm • Carried out by BOTH theorists and experimentalists

31. The debate continues • “On Control Theory and Practice”, G. John, AC, June 1970 • “Editorial: Some Thoughts on Research”, J. Mereditch, AC, Feb. 1980 • “Editorial: Theory and application: A common ground?” M. Sain, June 1980. • “An Industrial Point of View on Control Teaching and Theory”, E. H. Bristol, CSM, Feb. 1986 • Special Issue on Theory and Practice Gap, CSM December 1999. • Theory vs. Practice Forum, ACC 2004

32. The ISA Initiative • ISA (Instrument, systems, and automation) is the largest organization of instrument and control engineers in the world • ISA is organizing a Theory vs. Practice Forum at ACC2004 (by Z. Gao and R. Rhinehart)

33. Reflection on Control Research What and Why?

34. What is controls? Controls: An instrument or a set of instruments used to operate, regulate, or guide a machine or vehicle -the American Heritage Dictionary Is it a branch of engineering, science, or mathematics?

35. Control Engineering? Engineering: The application of scientific principles to practical ends as the design, construction, and operation of efficient and economical structures, equipment, and systems. -the American Heritage Dictionary If control is a branch of engineering, what are the scientific principles behind it?

36. Control Science? Science: The observation, identification, description, experimental investigation, and theoretical explanation of natural phenomena. -the American Heritage Dictionary Should we? Is Controls a natural phenomena? Was Controls learnt? Can we learn from birds?

37. The Theory-Practice Divide • Practitioners practice, improvise, experiment (experience counts in industry) • Theorists theorize Modern Control Theory is often viewed as a branch of Applied Mathematics • Why the divide?

38. Experimental Controls Research Discover vs. Apply

39. Experiment Discover Theorize

40. Observation: 95% of controllers used in Industry is PID • Conjectures: • Error based design must have merits; • Solution to robust control is outside the realm of modern control theory; • Better controllers can be found experimentally

41. Experiment #1: A design not strictly based on the math model

42. A unique disturbance estimator Augmented plant in state space: Extended State Observer

43. Active disturbance compensation

44. Active Disturbance Rejection Control

45. A Breakthrough in Motion Control

46. Hardware Test: torque disturbance

47. Performance of the disturbance observer f(t)

48. Model of F(.) in the state space→ in the time domain： How to reconstruct the extended state From U and Y ? Extension to Higher Order MIMO Plants

49. Extended state Dynamic linearization and decoupling Extended state observer (ESO)

50. Successful Applications • Motion Control (All manufacturing Industries) • Web Tension Regulation (paper, steel, printing..) • Machine Tools • Power Electronics (Motor, Converters …) • Aircraft Control (MIMO) • Process Control (with long transport delay) • Active Magnetic Bearing