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The Fault-Tolerant Insulin Pump Therapy. Alfredo Capozucca, Nicolas Guelfi, Patrizio Pelliccione. alfredo.capozucca@uni.lu nicolas.guelfi@uni.lu patrizio.pelliccione@uni.lu. University of Luxembourg Faculty of Sciences, Technologies and Communication
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The Fault-Tolerant Insulin Pump Therapy Alfredo Capozucca, Nicolas Guelfi, Patrizio Pelliccione alfredo.capozucca@uni.lu nicolas.guelfi@uni.lu patrizio.pelliccione@uni.lu University of Luxembourg Faculty of Sciences, Technologies and Communication Software Engineering Competence Center 6 , rue Richard Coudenhove-Kalergi L-1359 Luxembourg-Kirchberg LUXEMBOURG
Coordinated Atomic ActionsBasics facts • conceptual framework • coordinating complex concurrent activities • distributed system • achieving fault tolerance by integrating and extending two complementary concepts • Conversations • cooperative concurrency • implement coordinated error recovery • Transactions • consistency of shared resources in the presence of failures • competitive concurrency • http://homepages.cs.ncl.ac.uk/alexander.romanovsky/home.formal/caa.html
Coordinated Atomic Actions Why use CAA? • CAA, as a design structuring concept, provides support for the following aspects of reliability and safety: • Damage confinement • Complexity control • Fault tolerance • Critical condition validation • Nesting • A. Zorzo, A. Romanovsky, J. Xu, B. Randell, R. Stroud, I. Welch, "Using Coordinated Atomic Actions to Design Complex Safety-Critical Systems: The Production Cell Case Study", Software: Practice & Experience, 29, 7, 1999, 1-21
Case studyRequirement (1/2) • Implementing the technique Continuous Subcutaneous Insulin Injection: • Sensors to check the patient’s status • Pumps to administrate insulin • Delivering (over 24 hours per day) the right combined amount of two different kinds of insulin • Keeping the patient’s blood glucose
Case studyDomain knowledge • The doctor must set the parameters according to the specific treatment that the patient should receive. • This information will be stored in a patient’s personal record and will be consulted for the application. • The emergency room (ER) people are continually monitoring the patient’s vital signs. • Network connection: • The dotted arrows represent wireless connection (this allows the patient to move within the access point range). • The doctor and the ER have the classic connection. • The values of sensors and of the actuator are always transmitted correctly, without any loss or error. • All failure on any sensor or actuator is indicated by a specific value, which shows which kind of failure happened. • The alarm signal mechanism is free of faults and does not fail.
Case studyFault hypothesis (1/3) • Sensor stops (E1 or E2): A wearable sensor could not send valid values (special value of the wearable sensor) • (1) try again getting the value to continue the cycle • (2) delivery stops and the danger alarm will be turned on. • Delivery Limit (E3): amount of insulin dropping out of the safe range • the delivery is stopped and the danger alarm is turned on. • Actuator stops (E4, E6): an actuator’s sensor has detected a problembefore trying to inject the insulin • stop the delivery of insulin and start to ring the danger alarm.
Case studyFault hypothesis (2/3) • Delivery stops (E5, E7): an actuator’s sensor has detected a problem after the insulin injection • try again to deliver the insulin • the delivery of insulin will be stopped and the danger alarm will be turned on. • Cartridge very low (E4, E5, E6 or E7): the quantity of insulin in a cartridge is less than the low limit set in the cartridge • the delivery continues but the warning alarm is turned on. • Cartridge empty (E4, E5, E6 or E7): a cartridge of a pump does not have any more insulin • stopping the delivery and starting the danger alarm.
Case studyFault hypothesis (3/3) • Communication lost (E8, E9, E10 or E11): • the whole application is distributed by (at least) three different devices => if the communication between some of these devices is dropped • (1) the cycle will be completed using the values collected in the previous step of the cycle. • (2) the delivery of insulin is stopped and the danger alarm is turned on. • Patient’s record unreachable (E12): impossible to have access to the patient’s information set by the doctor • (1) try one more time to get this information • (2) the treatment will be stopped and the danger alarm must be turned on. • Logging problem (E13 or E14): the control system is not able to register on the data base the information about the step of the cycle that has been done • the information is kept in a local file. When the data base works again, the information saved on the local file is automatically sent to the data base.
Thank you for your attention! Questions?