1. Failure diagnosis for cardiac pacemakers using Petri nets Professor National Chin Yi University of Technology Samuel Yang Lecture Course ( 楊善國 ) ( 勤益科技大學機械工程系教授 )

2. Contents  Introduction  Definition of Reliability  Frequently Used Methods for Failure Analysis  Failure Analysis for pacemakers by Petri Nets  References

3. Introduction  A failure is defined as any change in the shape, size,or material properties of a structure, machine, or component that renders it unfit to carry out its specified function adequately.  For the purpose of reliability assurance, failures of a system need to be traced and analyzed, especially for safety devices such as cardiac pacemakers.

4. Reliability  Specified conditions  Required performance  Stated time period  Probability Definition: The probability that an item (a part, a device, a subsystem, or a system) will carry out its required performance under specified conditions for a stated time period. Key factors: Therefore, Reliability and failure are closely related.

5. Frequently Used Methods for Failure Analysis  Fault Tree Analysis (FTA)  Failure Modes and Effects Analysis (FMEA)  Failure Modes, Effects and Criticality Analysis (FMECA)  Petri Net Method

6. The principal pathologic conditions in which cardiac pacemakers are applied are known collectively as heart block (Arrhythmia), i.e. the heart of an arrhythmic patient is not stimulated at a proper rate on its own. Pacemaker

7. A cardiac pacemaker is an electric stimulator that produces periodic pulses that are conducted to electrodes located in the heart so as to cause it to contract.  Constant-voltage amplitude pulses are typically in the range of 5.0 to 5.5V with duration of 500 to 600 μs.  Constant-current amplitude pulses are typically in the range of 8 to 10 mA with pulse durations ranging from 1.0 to 1.2 ms.  Rates for a synchronous pacemaker range from 70 to 90 beats per minute (bpm). Pacemaker

8. Asynchronous: Fixed pulse-rate regardless of the body condition According to the control algorithms, pacemakers can be classified to: Pacemaker Synchronous: Functioning intermittently as required 1.Demand 2.Atrial 3.Combined Rate-responsive: Triggered according to the actual demand

12. Asynchronous Pacemakers

13. Synchronous Pacemakers － Demand Demand: Providing function when it is needed

14. Synchronous Pacemakers － Atrial

15. Synchronous Pacemakers － Combined

16. Synchronous Pacemakers － Rate-responsive

17. Physiological variables and the corresponding sensors for rate-responsive pacemakers

18. ○ : Place ( 位置 ), drawn as a circle, denotes an event : Immediate transition ( 立即變遷 ), drawn as a thin bar, denotes event transfer with no delay time : Timed transition ( 時延變遷 ), drawn as a thick bar, denotes event transfer with a period of delay time : Arc ( 弧 ), drawn as an arrow, between places and transitions : Token ( 標記 ), drawn as a dot, contained in places, denotes the data : Inhibitor arc ( 禁制弧 ), drawn as a line with a circle end, between places and transitions Basic Symbols of Petri Nets

19. Basic Structures of Logic Relations for Petri Nets for Petri Nets

20. Petri net for describing the operation of a combined synchronous pacemaker

21. Marking of a Petri net A marking ( 標幟 ) of a Petri net is defined as: the number of tokens at each place, denoted by a column vector M. Thus vector M k = (n 1, n 2,... n m ) T represents that token numbers of places P 1, P 2,... P m at state k are n 1, n 2,... n m, respectively.

22. CP1: Checkpoint 1, M(CP1)=1 (0) represents that the power-supply is functioning (not functioning). CP2: Checkpoint 2, M(CP2)=1 (0) represents that the atrial-electrode is functioning (not functioning). CP3: Checkpoint 3, M(CP3)=1 (0) represents that the amplifier#2 is functioning (not functioning). CP4: Checkpoint 4, M(CP4)=1 (0) represents that the reset-circuit is functioning (not functioning). CP5: Checkpoint 5, M(CP5)=1 (0) represents that the oscillator is functioning (not functioning). CP6: Checkpoint 6, M(CP6)=1 (0) represents that the 500ms-delay-vibrator is functioning (not functioning). CP7: Checkpoint 7, M(CP7)=1 (0) represents that the gate is at a closed state (an open state). CP8: Checkpoint 8, M(CP8)=1 (0) represents that the 120ms-delay-vibrator is functioning (not functioning). CP9: Checkpoint 9, M(CP9)=1 (0) represents that the 2ms-delay-vibrator is functioning (not functioning). CP10: Checkpoint 10, M(CP10)=1 (0) represents that the output-circuit is functioning (not functioning). CP11: Checkpoint 11, M(CP11)=1 (0) represents that the ventricular electrode is functioning (not functioning). CP12: Checkpoint 12, M(CP12)=1 (0) represents that the amplifier#1 is functioning (not functioning). Twelve Checkpoints

23. Petri net for failure diagnosis of a combined synchronous pacemaker

24. Checking Code of the Pacemaker Checking Code of the Petri net is the marking that is composed of the token number of the12 check points. i.e. Checking Code = (CP1, CP2,... CP12) T

25. Petri net for the remote mode of a combined synchronous pacemaker The transmitter can be triggered manually or automatically.

26. Actualization 1.Convert Petri nets to a logic circuit 2.Design the resultant circuit by a software 3.Download the designed circuit to an FPGA (Field Programmable Gate Array) 4.Integrate the logic circuit to a pacemaker Steps:

27. Corresponding Circuits for Basic Petri Net Symbols

29. Truth table for the relations among CP2, CP4, and B99 Truth table for the relations among CP2, CP5, and B99  XOR  XNOR

31. Petri net for the remote mode of a combined synchronous pacemaker The transmitter can be triggered manually or automatically.

32. The Downloaded FPGA

33. 1.The Petri net is a powerful graphical tool for modeling a dynamic system such as a combined synchronous pacemaker, which helps the design, failure diagnosis, and research of control algorithms of a cardiac pacemaker. 2.This study demonstrates the modeling and failure diagnosis for the normal mode and remote mode, that operates manually or automatically, of a combined synchronous pacemaker by a Petri net approach. 3.The operational status of the pacemaker is clearly visible from the Petri net model and the health condition is clear at a glance by the checking code of the pacemaker. Conclusions

34. References 1. S. K. Yang, ‘A Petri-net approach to remote diagnosis for failures of cardiac pacemakers’, Quality and Reliability Engineering International, 20(8), pp. 761-776, December 2004. 2. Patrick D. T. O’Connor, Practical Reliability Engineering, 4 th Ed., John Wiley, Chichester, England, 2002. 3. E. A. Elsayed, Reliability Engineering, Addison Wesley Longman, Taipei, 1996. 4. Joseph J. Carr and John M. Brown, Introduction to Biomedical Equipment Technology, 4 th Ed., Prentice Hall, New Jersey, 2001. 5. S. K. Yang, Introduction to Reliabilty Engineering, 2 nd ed., Quan Hua, Taipei, September 2008, ISBN 957-21-4996-2. (In Chinese and English)

35. Thank You!

36. 蘇州大學

37. 蘇州大學

38. 蘇州大學

39. 蘇州大學

40. 上海華東理工大學

41. 上海華東理工大學

42. 上海華東理工大學

43. 上海華東理工大學