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Erin Baker - Semantic Scholar
Elena Verdolini45
Marzio Galeotti9
Matthew Bunn9
Jessika E. Trancik8
44Olaitan Olaleye
24Nori Tarui
15Robert N. Stavins
6Serena Pontoglio
6Burkhard Drees
Firm Incentives to Promote Technological Change in Pollution Control : Comment
Erin Baker, Ekundayo Shittu
Technical Change and the Marginal Cost of Abatement ∗
We address one aspect of the treatment of technical change in the environmental economics literature: how technical change impacts the marginal cost of abatement. We review a selection of papers that… (More)
Optimal Technology R & D in the Face of Climate Uncertainty
This paper explores optimal near-term technology R&D in the face of uncertain damages caused by the buildup of greenhouse gases. The paper puts particular emphasis on understanding how optimal… (More)
Erin Baker, Meredith L. Fowlie, Derek Lemoine, Stanley S. Reynolds
The benefits and costs of increasing solar electricity generation depend on the scale of the increase and on the time frame over which it occurs. Short-run analyses focus on the cost-effectiveness of… (More)
Demand Subsidies Versus R & D : Comparing the Uncertain Impacts of Policy on a Pre-commercial Low-carbon Energy Technology
We combine an expert elicitation and a bottom-up manufacturing cost model to compare the effects of R&D and demand subsidies. We model their effects on the future costs of a low-carbon energy… (More)
Uncertainty and Learning in a Strategic Environment : Global Climate Change ∗
Global climate change is rife with uncertainties. Yet, we can expect to resolve much of this uncertainty in the next 100 years or so. Therefore, current actions should reflect the value of… (More)
Increasing Risk and Increasing Informativeness: Equivalence Theorems
When considering problems of sequential decision making under uncertainty, two of the most interesting questions are: How does the value of the optimal decision variable change with an increase in… (More)
Future Costs of Key Low-Carbon Energy Technologies : Harmonization and Aggregation of Energy Technology Expert Elicitation Data
Erin Baker, Valentina Bosetti, Laura Diaz Anadon, Max Henrion, Lara Reis
In this paper we standardize, compare, and aggregate results from thirteen surveys of technology experts, performed over a period of five years using a range of different methodologies, but all… (More)
Global climate change presents a classic problem of decision making under uncertainty with learning. We provide stochastic dominance theorems that provide new insights into when abatement and… (More)


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Prost! All Inclusive German Happy Hour Tickets, Mon, Jun 12, 2017 at 4:00 PM | Eventbrite
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Dangling Pointers: Pathology, Prevention and Cure - CodeProject 11,721,385 members (73,168 online)
Last Visit: 31-Dec-99 18:00 Last Update: 5-Sep-15 3:27Refresh12

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The Odyssey of Homer - Walmart.com
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Patent US5271389 - Ventilator control system that generates, measures, compares, and corrects ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThe present invention provides a system and method for providing an improved correction to an input flow control signal to a flow control valve in a ventilator system. The correction as derived from a sum of the error in the flow rate actually delivered as compared with the desired flow rate for each...http://www.google.com/patents/US5271389?utm_source=gb-gplus-sharePatent US5271389 - Ventilator control system that generates, measures, compares, and corrects flow ratesAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS5271389 APublication typeGrantApplication numberUS 07/836,773Publication dateDec 21, 1993Filing dateFeb 12, 1992Priority dateFeb 12, 1992Fee statusPaidAlso published asCA2089343A1, CA2089343C, DE69333719D1, DE69333719T2, EP0560490A1, EP0560490B1, US5319540Publication number07836773, 836773, US 5271389 A, US 5271389A, US-A-5271389, US5271389 A, US5271389AInventorsFernando J. Isaza, Stanley Y. WongOriginal AssigneePuritan-Bennett CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (7), Referenced by (148), Classifications (12), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetVentilator control system that generates, measures, compares, and corrects flow rates
US 5271389 AAbstract
The present invention provides a system and method for providing an improved correction to an input flow control signal to a flow control valve in a ventilator system. The correction as derived from a sum of the error in the flow rate actually delivered as compared with the desired flow rate for each control interval in a breath with the sum of past errors corresponding to control intervals in past breaths to generate a cumulative error signal for application in the control interval in a next breath. The cumulative error signal is stored as the sum of previous sustained errors arising periodically in the system for each control interval of previous breaths, and is integrated with the current error signal for each control interval to generate an integrated correction component signal. The input flow control signal is summed with the integrated correction component to generate a corrected command flow signal to the flow control valve.
1. A ventilator control system for controlling the rate of flow of a respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system, said ventilator control system comprising;means for generating an input flow control signal based upon a desired rate of flow for a control interval in a current breath; means for measuring an actual rate of flow in the ventilation system and generating a flow rate signal representing the actual rate of flow; means for comparing said actual rate of flow with said desired rate of flow, and generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each said control interval in each current breath; means for summing each current error signal for each said control interval in each current breath with a sum of previous error signals for each said control interval of previous breaths to generate a correction component signal for application in said control interval in a next breath; means for storing said correction component signal as the sum of previous error signals of each said control interval of previous breaths; means for integrating said current error signal and said correction component signal for each said control interval to generate an integrated correction component signal; and means for summing said input flow control signal and said integrated correction component to generate a command flow signal for said ventilation system. 2. The system of claim 1, further including means for modifying said input flow control signal to include a predetermined valve gain feedforward component for each said control interval of each breath, and means for summing said feedforward component with said input flow control signal to generate a corrected input flow control signal for each said control interval in each current breath.
3. A method of controlling the rate of flow of a respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system, the method comprising the steps of:generating an input flow control signal based upon said desired rate of flow for each control interval in a current breath; measuring the actual rate of flow in the flow path and generating a flow rate signal representing the actual rate of flow in the ventilation system; comparing the actual rate of flow with the desired rate of flow, and generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each said control interval in each current breath; and summing each said current error signal for each said control interval in each current breath with a sum of previous error signals for each said control interval of previous breaths to generate a correction component signal for application in said control interval in a next breath; storing said correction component signal as the sum of previous error signals of each said control interval of previous breaths; integrating said current error signal and said correction component for each said control interval to generate an integrated correction component signal; and summing said flow control signal and said integrated correction component signal to generate a command flow signal for said ventilation system. 4. The method of claim 3, further comprising the step of modifying said input flow control signal by adding a predetermined valve gain feedforward component to said input flow control signal to generate a corrected flow control signal, for each said control interval in each current breath.
5. A method of controlling the rate of flow of a respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system, the method comprising the steps of:generating an input flow control signal based upon said desired rate of flow for each control interval in a current breath; measuring the actual rate of flow in the flow path and generating a flow rate signal representing the actual rate of flow in the ventilation system; comparing the actual rate of flow with the desired rate of flow, and generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each said control interval in each current breath; and summing each said current error signal for each said control interval in each current breath with a sum of previous error signals for each said control interval of previous breaths to generate a correction component signal for application in said control interval in a next breath. 6. A ventilator control system for controlling the rate of flow a respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system, comprising a source of respiratory gas, a flow path between said source of respiratory gas and in fluid communication with a patient, a flow control valve for controlling the rate of flow in said flow path, control means for generating a control signal for operating said flow control valve at least once in a predetermined control interval in a breath to deliver a desired rate of flow in said flow path for each said control interval in that breath, and a flow sensor in said flow path connected to said control means for measuring the actual rate of flow in said flow path, said ventilator control system further comprising;means for generating an input flow control signal based upon said desired rate of flow for each control interval in a current breath; means for measuring the actual rate of flow in the flow path and generating a flow rate signal representing the actual rate of flow in the flow path; means for comparing said rate of flow in said flow path with said desired rate of flow, and generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each said control interval in that breath; means for summing each said current error signal for each said control interval in said breath with a sum of previous error signals for each said control interval of the previous breaths to generate a correction component signal for application in said control interval in a next breath; means for storing said correction component signal as the sum of previous error signals of each said control interval of those previous breaths; means for integrating said current error signal and said correction component signal for each said control interval to generate an integrated correction component signal; and means for summing said input flow control signal and said integrated correction component signal to generate a command flow signal for said flow control valve. 7. The system of claim 6, further including means for modifying said input flow control signal to include a predetermined valve gain feedforward component for each said control interval of each breath, and means for summing said feedforward component with said input flow control signal to generate a corrected input flow control signal for each said control interval in that breath, said means for modifying overcoming initial flow resistances inherent in the ventilator system.
8. A method of controlling the rate of flow of respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system, comprising providing a ventilation system including a source of respiratory gas, a flow path for said respiratory gas in fluid communication with a patient, a flow control valve for controlling the rate of flow in said flow path, control means for generating a control signal for operating said flow control valve at least once in a predetermined control interval in a breath to deliver a desired rate of flow in said flow path for each said control interval in that breath, and means for measuring the rate of flow in said flow path connected to said control means for generating a flow rate signal representing the actual rate of flow in said flow path, and further comprising the steps of:generating an input flow control signal based upon said desired rate of flow for each control interval in a current breath; measuring the actual rate of flow in the flow path and generating a flow rate signal representing the actual rate of flow in the flow path; comparing the rate of flow in said flow path with the desired rate of flow in said flow path, and generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each said control interval in said breath; summing each said current error signal for each said control interval in said breath with a sum of previous error signals for each said control interval of previous breaths to generate a correction component signal for application in said control interval in a next breath; storing said correction component signal as the sum of previous error signals of each said control interval of the previous breaths; integrating said current error signal and said correction component for each said control interval to generate an integrated correction component signal; and summing said flow control signal and said integrated correction component signal to generate a command flow signal for said control valve. 9. The method of claim 8, further comprising the steps of modifying said input flow control signal by adding a predetermined valve gain feedforward component to said input flow control signal to generate a corrected flow control signal, for each said control interval in that breath and thereby correcting for initial flow resistances within said system.
This invention relates generally to controllers for systems having periodic output functions with measurable parameters such as pressure, flow, motion, and the like, and more particularly relates to an electronically controlled ventilator system for providing respiratory gas to a patient, and an improved system and method for discrete time control of ventilation flow during patient breaths.
Breathing ventilator systems conventionally provide breathing gas to a patient for pressure supported breath assistance at a pressure support level as high as 70 centimeters of water, or minimal pressure, usually no more than 2 centimeters of water above baseline.
Conventional ventilators typically provide breath inhalation support at regular intervals, or at intervals triggered by a patient's spontaneous inspiration effort. Errors in the delivery of gas flow as compared to the desired gas flow at the appropriate time can occur due to lag time between the onset of patient inspiratory effort and actual valve response time, regulator response, and valve gain variations. Although typical flow controllers may utilize a feedforward flow control gain component and various types of feedback error correction, such as proportional, integral, or derivative error feedback control, to compensate for real time disturbances that occur in the system, such systems frequently have difficulty in correcting for any sustained errors that occur periodically in the system.
Until recently, such inaccuracy in flow control of ventilators has hampered application of ventilators for infant and neonatal patients. It would therefore be desirable to provide a system for adaptive response to periodic disturbances in a ventilator flow system, based upon past system performance with the correction including an integration of flow rate errors during all of the previous breath control intervals for a patient. It would be desirable for every control interval of patient assisted breathing to be affected by a correction component, so that the output flow rate matches the actual demands on the system.
A major factor in assisting patient breathing is the energy required by a patient to trigger and obtain an adequate flow of respiratory gas. It would therefore be desirable to improve the accuracy of flow control to reduce this energy requirement in the work of breathing.
The present invention provides a system and method for providing a correction to a signal controlling a flow control valve in a ventilator system. The correction component integrates the difference between the desired flow rate and the actual delivered flow rate for each control interval for each breath with the sum of past errors corresponding to the same control interval of the past breaths to generate a corrected command flow signal to be applied on the corresponding appropriate interval to the flow control valve.
Briefly and in general terms, the system of the present invention for controlling the rate of flow of a respiratory gas supplied by a ventilation system for supporting breaths of a patient intubated on the ventilation system comprises means for generating an input flow control signal based upon a desired rate of flow for each control interval in the current breath, means for measuring the actual rate of flow in the flow path of the ventilation system for each control interval in the current breath, means for generating a current error signal representing the difference between the actual rate of flow and the desired rate of flow for each control interval in the current breath, and means for summing each error signal for each control interval in the current breath with the sum of the previous error signals for each control interval of the previous breaths to generate a correction component signal to be used at the appropriate control intervals in the next breath. The system includes means for storing the correction component signal as the sum of previous error signals of each control interval of the previous breaths, and means for summing the error signal and the correction component control signal for each control interval to generate a signal to be applied to a conventional integrator element.
Means are also preferably provided for generating a predetermined valve gain feedforward component for each control interval of each breath and for summing the output signal resulting from the conventional integrator with the feedforward correction component, for each control interval, to generate a command flow signal for the flow control valve.
In the currently preferred method of the invention, controlling the rate of flow of the respiratory gas supplied by the ventilation system involves generating input flow control signals based upon the desired flows for all control intervals for each breath, measuring the actual rate of flow in the flow path for all control intervals, comparing the rate of flow in the flow path with the desired rate of flow to generate the current error signal for all control intervals representing the difference between the actual rate of flow and the desired rate of flow for each breath and summing each current error signal for each control interval with the sum of the previous error signals for each control interval for each past breath, to generate the correction component signals for use in the next breath. The correction component signal, for a given control interval in a breath, is preferably stored as the sum of the previous error signals for the corresponding control interval of the past breaths slimmed with the current error signal for the given control interval for the current breath to generate a correction component signal for the next breath.
A predetermined valve gain is preferably used in the feedforward component to generate the feedforward element of the command flow signal. The signal resulting from the summation of the error signal and the correction component signal is preferably processed by a conventional integrator, to generate a second element in the command flow signal. This element of the command flow signal is preferably added to the feedforward component to generate the command flow signal for operating the flow control valve. Controlling the flow control valve in this manner thus allows the ventilation system to deliver the desired rate of flow for each breath.
Other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings which illustrate by way of example the features of the invention.
FIG. 1 is a diagram of a conventional ventilation system;
FIG. 2 is a block diagram of a prior art flow controller;
FIG. 3 is a block diagram of the flow control correction system of the invention;
FIG. 4 is a graph showing a flow response of a prior art controller;
FIG. 5 is a graph of a flow response of a controller according to the present invention as illustrated in FIG. 3; and
FIG. 6 is a chart comparing the accuracy of flow delivery for a prior art controller and for a controller according to the invention.
As is shown in the drawings for purposes of illustration, the invention is embodied in a system for providing a corrected flow control of respiratory gas supplied by a ventilation system, to improve accuracy of the rate of flow delivered by the system, and to reduce the patient work of breathing. The flow control correction system may be used in an open or closed patient ventilation system, having a source of respiratory gas, a flow path for communicating a respiratory gas to a patient intubated in the ventilation system, a flow control valve for controlling the rate of flow in the flow path, control means for generating a control signal for operating the flow control valve at least once in a predetermined control interval in a breath to deliver a desired rate of flow in the flow path for each breath supported by the ventilation system, and a flow sensor in the flow path connected to the control means for measuring the actual rate of flow in the flow path. An input signal based upon the rate of flow of respiratory gas required to support a patient breath is modified by the flow control correction system of the invention to provide a command flow signal to the flow control valve.
The respiratory gas is preferably enriched with a higher concentration of oxygen than normal, so that the source of respiratory gas may include more than one individual gas source, and may also include a device for mixing various proportions of the individual gases.
Accordingly, with reference to FIGS. 1 and 2, an exemplary prior art ventilation system 10 to which the flow control correction system of the invention may be applied typically includes a source of oxygen gas 12, which is typically a pressurized tank of oxygen, and a source of air 14, which may also consist of a high pressure tank or air compressor, which can supply air as needed from the ambient atmosphere. Other conventional sources of pressurized oxygen and air in hospital settings would also be appropriate. The source of oxygen is connected by a duct 16 to a proportional solenoid valve 18 which is in turn connected by duct 19 to a mixing chamber 20. A flow sensor 21 is preferably mounted in or connected to the duct 19 for measuring the rate of flow of oxygen actually delivered to the mixing chamber. The source of air is similarly connected by an air supply duct 22 to a proportional solenoid 24 for supplying air as needed to the mixing chamber via the duct 23, which also preferably includes a flow sensor 25 for measuring the actual rate of air flow delivered to the mixing chamber. Valves other than proportional solenoid valves that function in a similar manner may also be appropriate. The mixed gases can then be delivered to the patient through the patient airway generally indicated as 26. The patient airway can include, in a prefered embodiment, conduit 27, patient wye 30 and associated conduits for inhalation and exhalation. The patient airway 26 can also include a patient airway flow control valve 28 which controls the rate of flow of respiratory gas through the patient wye 30. A flow rate and/or pressure sensor 32 is typically placed within the patient airway for measuring the rate of flow or pressure level from the flow control valve through the patient airway. In a presently preferred embodiment, the sensor 32 can be placed downstream of the wye 30.
Referring to FIG. 2, the flow rate sensor is connected to a controller 34 for controlling the flow control valve based upon an input signal 36 representing the desired flow rate, which can be based upon patient respiratory demand based upon the flow rate and/or pressure measured in the patient wye, or which can be a stored value representing a predetermined flow level. The patient wye typically also includes a flow path for exhalation (not shown) which can also be monitored as desired.
The prior art electronic controller 34 shown in greater detail in FIG. 2 preferably includes a microprocessor for controlling all of the functions of the ventilator control system, and is also preferably connected to the oxygen and air supply flow valves 18 and 24, the flow rate sensors 21 and 25, and any additional flow meters, such as an exhalation flow meter. The electronic controller 34 typically also compares the rate of flow in the patient wye with a predetermined flow threshold level to detect changes in the flow due to inhalation efforts by the patient, and exhalation efforts by the patient, for purposes of triggering initiation of the control for the desired operation of the patient airway flow control valve 28, and to determine necessary corrections of the input signal for a desired flow rate to generate a command signal to the patient airway flow control valve to produce an actual flow rate at the desired rate in the patient airflow path. The electronic controller also preferably controls the proportional mixing through the oxygen and air supply valves, and adjusts the patient airway flow control valve to the appropriate state when exhalation efforts of the patient are detected.
The energy expended by a patient while breathing on a mechanical ventilator is related to not only the energy required to trigger gas delivery by the ventilator, but is also directly related to the accuracy of the volume of gas delivered to the patient. The flow control correction system of the invention is designed to improve the accuracy of control of the flow rate of gas delivered to the patient to reduce the energy required to be expended by the patient in breathing. This is accomplished by the division of the period of time from one breath to the next into a number of control intervals, and the implementation of a correction component for every control interval in the breath in a way such that for each breath of the patient the accuracy of delivery and the system response are improved. The correction component allows the control system to provide an adaptive response to compensate for sustained errors inherent to the system being controlled as well as to periodic disturbances, in a manner which a conventional controller is not able to do.
As is illustrated in FIG. 2, the prior art flow controller 34 typically includes a proportional gain amplifier means 38 such as an adjustable amplifier circuit or the like, which is connected to receive the error signal 37 for adding a proportional gain component to the error signal 37 to generate the basic command flow rate signal 39 to the flow control valve 28. The flow rate sensor 32 generates a flow rate measurement signal 43 which is compared at the comparator summing element 40 with the desired flow signal to generate an error signal 37, which is typically amplified by an integral gain element 41a and integrated by a conventional integrator element 41b with previous error signals, and which is then summed by summing element 42 with the basic amplified command signal to provide an integrated proportional command signal 39 to the flow control valve 28.
As is illustrated in FIG. 3, the flow control correction system of the present invention preferably includes a means for integrating past flow rate delivery errors as a correction component for each control interval within each breath. This correction component is preferably added to the current error in delivery of flow rate for a patient breath to provide a signal input to a conventional integrator element which integrates the signals generated in previous control intervals within that breath. The correction component is further preferably added to feedforward flow control valve gain component to provide a corrected command signal for achieving the desired flow rate.
Thus, a controller 134 implementing the preferred embodiment of the invention is adapted to be used with a conventional ventilation system 10, in place of the prior art controller 34. A desired flow rate input signal 36 for a desired flow in a breath control interval number [n]for a particular breath number (k]is preferably received by valve feedforward gain means 138, such as an amplifier circuit, or the like for generation of a feedforward valve flow rate gain component to the desired flow rate input signal to overcome initial resistances and limitations of the system in delivering patient flow requirements before adequate feedback has been established. Alternatively, the feedforward gain element 138 may be omitted, although the control system would be less efficient in this configuration.
The flow rate measurement signal for each control interval in a breath generated by the flow meter 32, is received by the summing comparator element 140 which compares the input signal 36 with the actual flow rate measurement signal, to generate the current flow rate error signal [n][k] for the current control interval number [n] in the current individual breath number [k]. The current flow rate error signal is received by the summing element 142 which sums the instantaneous current error signals for each control interval in a breath with the sum of all previous corresponding error signals that occurred prior to the current breath number [k]. This sum of the current error signal (error [n][k]) for the current control interval and all previous error signals (sum [n][k-1]) for the current interval is stored in a storage or memory means 144 for use as a cumulative error signal for the corresponding control interval [n] of the next breath [k+1]. The cumulative error signal (sum [n][k-1]) represents sustained errors arising periodically in the system. The summing element 146 receives and sums the current error signal [n][k] for the control interval in a breath from summing element 140 with the cumulative error signals [n+1][k-1] from the storage means 144 to provide a signal which is preferably applied to a conventional integrator 148, with gain kI, for generation of an integrated signal (Int Cmd [n][k]). The integrated signal is then added at summing element 150 with the feedforward command signal component (FFCmd [n][k]) to form the flow command signal (Cmd [n][k]) for application to the flow control valve 152, which is preferably a proportional solenoid valve.
As can be seen from FIGS. 4, 5 and 6, for a typical set of desired values for patient airway flow rate providing a sharp onset of flow, a constant flow rate for the period of inspiration assistance, and a relatively sharp cessation of flow known generally as a SQUARE trajectory, the flow control correction system of the invention approaches the desired trajectory more rapidly than the prior art controller does. Thus, assuming that the programmed trajectory of flow control is correct for the patient, the energy required of the patient for breathing should thereby be reduced.
It should be understood that while the valve feedforward gain element and the conventional integrator make for a more efficient control system, they can optionally be omitted from the controller, and the correction component can in itself correct for sustained errors that occur periodically in the ventilation system.
Thus, in the foregoing description, it has been demonstrated that the system and method of the invention allow for increased accuracy of flow rate delivery for reduction of patient work of breathing, by determining an error correction component which allows for adaptive response to real time disturbances which occur periodically in the ventilator system. It should be understood that the invention is also broadly applicable to controllers for systems having periodic output functions with measurable parameters such as pressure, flow, motion, and the like, so that the invention is not limited to use in controllers for ventilator systems.
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Inc.Multi-mode control loop with improved performance for mass flow controller* Cited by examinerClassifications U.S. Classification128/204.21, 128/204.24, 128/204.22International ClassificationG05D7/06, A61M16/00, A61M16/20Cooperative ClassificationA61M2016/0036, G05D7/0635, A61M16/00, A61M16/204European ClassificationG05D7/06F4B, A61M16/00Legal EventsDateCodeEventDescriptionFeb 12, 1992ASAssignmentOwner name: PURITAN-BENNETT CORPORATION, CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:ISAZA, FERNANDO J.;WONG, STANLEY Y.;REEL/FRAME:006018/0186Effective date: 19920131Oct 25, 1994CCCertificate of correctionJun 9, 1997FPAYFee paymentYear of fee payment: 4Jun 20, 2001FPAYFee paymentYear of fee payment: 8Jul 17, 2001REMIMaintenance fee reminder mailedJun 21, 2005FPAYFee paymentYear of fee payment: 12RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS 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Through the Years: History of Cabri and District by Cabri History Book Committee: Cabri History Book Committee, Steinbach, Manitoba 9780919673786 Turquois Cloth, Assume 1st. - ProPen
Home Cabri History Book Committee Through the Years: History of Cabri and District
Through the Years: History of Cabri and District
Cabri History Book Committee
ISBN 10: 0919673783 / ISBN 13: 9780919673786
Published by Cabri History Book Committee, Steinbach, Manitoba, 1984
Lovely copy, neat and clean, has appreciative gift inscription inside front board. Large, heavy book will need special arrangements for shipping, please inquire prior to ordering. Size: 4to - over 9¾" - 12" tall. Bookseller Inventory # 013095
Title: Through the Years: History of Cabri and ...
Publisher: Cabri History Book Committee, Steinbach, Manitoba

value: This website is an e-commerce global online marketplace with seven websites that offer books, fine art, and collectables from sellers in over 50 countries. Launched in 1996, it specialises in used, rare and out-of-print books.


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Painting and Drawing Boats by Moira Huntly (Paperback, 1985) | eBay
Painting and Drawing Boats by Moira Huntly (Paperback, 1985)
RRP £10.95 Save 67%
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RFID Wormholes The Case of Contactless Smartcards Tomáš Rosa crypto.hyperlink.czSmartCard Forum 2011, Prague 2.
Abstract This presentation is a summary of research activity aimed to prove the following hypothesis:  Using generally available computing devices and program codes, it is practically easy to mount a wormhole (or relay) attack in a typical system accepting ISO 14443 contactless smartcards. We emphasize, that a negation of this hypothesis is still very often used as an argument supporting security of many contactless smartcard applications. This research is, besides the others, directly linked to physical access control systems, electronic passports, and contactless identity cards. SmartCard Forum 2011, Prague 3.
Part ONEContactless Smartcard RecalledSmartCard Forum 2011, Prague 4.
Contact(less) SmartcardApplication layer ISO 7816-4 and higherTransport layer ISO 14443-4 ISO ISOData link layer 14443A-3 14443B-3 ISO 7816-3 ISO ISOPhysical layer 14443A-2 14443B-2Electromechanical ISO 7816-1, 2 ISO 14443-1properties contact interface contactless interface SmartCard Forum 2011, Prague 5.
ISO 14443 Physical Layer Employs inductive coupling in so-called near field of the transmitter at 13.56 MHz (HF band).  Field equations are reduced considerably, especially wave effects can be omitted [7], [11], [31], [41].  This is true for an ordinary operation. An attacker trying to expose limits of this communication may be facing a “different” physics.  Threshold is approx. /2,   300/f [m, -, MHz]  Arrangement „PCD antenna – PICC antenna“ can be viewed as a high frequency transformer.  Comprehensive description is given in [11].  Such a setup differs from UHF RFID [7], [11] significantly, so care must be taken when interpreting distance ranges experiments, etc. SmartCard Forum 2011, Prague 6.
PCD – PICC Coupling(Data Communication) PICC terminal PCD internal network transponder field terminal field PCD: direct amplitude modulation of the basic carrier PICC: load modulation resulting in indirect amplitude/phase modulation of the basic carrier SmartCard Forum 2011, Prague 7.
Communication Oscillograph Yellow trace: PCD to PICC PICC to PCD basic carrier ISO 14443-A Green trace: AM detector with 847.5 kHz filter SmartCard Forum 2011, Prague 8.
When the Distance MattersMethod DistanceActive communication with PICC dozens of cmPassive reception – PICC and PCD units of mPassive reception – PCD only dozens of mActive communication with PCD dozens of m Table summarizes attacker’s objectives and ranges for ISO 14443 (HF band). Note that in wormhole attacks, we are usually not challenging these distances, expect possible extension of active communication with the original PICC. SmartCard Forum 2011, Prague 9.
Part TWOWormhole Attack -Cryptography ViewpointSmartCard Forum 2011, Prague 10.
Wormhole (Relay Channel) Let the wormhole be any method enabling communication in between an out-of-range application transponder and the terminal.  The term wormhole is getting used in place of relay channel to mimic the parallel with (yet hypothetical) 4D-spacetime “shortcuts”.  However, no 4D-spacetime shortcut (even hypothetical) actually occurs here, this just a fancy name. SmartCard Forum 2011, Prague 11.
Wormhole Attack (WA) Let the wormhole attack be any attack strategy based on using a wormhole to make the terminal to accept and process the out-of-band application transponder.  The main risk of this attack is coming from the fact, that, in many contactless applications, the presence of a transponder at the terminal is directly linked to somebody’s intension to e.g. open door, pay a bill, undergo electronic passport check, etc.SmartCard Forum 2011, Prague 12.
Wormhole vs. MITM Attacks The key difference in between the wormhole attack and the more widely known man-in-the-middle approach is in the primary objective:  MITM is a-priori aimed at data interception and/or manipulation.  Wormhole attack is a-priori aimed at enabling certain unwanted communication to occur.  The communication itself, however, is not necessarily being modified or even understood by the attacker.  Therefore, conventional cryptographic techniques aimed at a pure data protection [30] are totally useless against WA. SmartCard Forum 2011, Prague 13.
Old Problem’s New Face Wormhole attack is definitely not such a new threat as RFID sellers (sometimes even researchers) try to pretend.  In cryptology, it is known at least since 1987 [5].  The reference [5] also gives an interesting story on how the mafia fraud term originated.  It is rather long-time overlooked than a brand new problem. On the other hand, thanks to RFID, its importance is becoming adequately recognized.  We note, however, that the viewpoint stated in [5] foresees certain issues that are somehow out of scope basing on the distance bounding paradigm accelerated by RFID. SmartCard Forum 2011, Prague 14.
Distance Bounding Protocols These are special kind of cryptographic protocols, that can in theory protect against wormhole attacks [3].  They are, however, seldom known and even more rarely used in practice. Their cornerstone principle is really nicely illustrated by the excellent, two-sentence-long conclusion of Beth and Desmedt [2] (1990).  “Because the speed of light is finite and constant we have provided a practical solution to the mafia and terrorist fraud. Its applications go beyond identification.” SmartCard Forum 2011, Prague 15.
RF Considerations of DBP Using elementary signal theory, the time-delay resolution achievable at the terminal side can be estimated as: t = 2 / B, where B is the RF channel bandwidth. Here, we assume the transponder is using the load modulation of the terminal basic carrier signal [11]. The distance measurement then has an accuracy no better than: d = c*t / 2 = c / B, where c is the speed of light (celeritas). This simple formula agrees with the one presented in [18]. SmartCard Forum 2011, Prague 16.
DBP and ISO 14443 I There is no DBP which would be an implicit part of ISO 14443.  Actually, this standard rather enhances the wormhole attacks [19].  Unfortunately, there are also physical limits imposed by the relatively narrow bandwidth of at most 2 MHz. d  150 m SmartCard Forum 2011, Prague 17.
DBP and ISO 14443 II There are claims saying the natural range limitations of the inductive coupling interface employed in ISO 14443 is an implicit countermeasure against wormhole attacks.  Well, this can be considered as a kind of protection – against spontaneous accidents.  It was shown (cf. here and references) that such a measure fails to provide adequate protection against intentional attacks. SmartCard Forum 2011, Prague 18.
Part THREEPractical Approaches To Wormhole AttackSmartCard Forum 2011, Prague 19.
Wormhole Attack Illustrated interconnection network far field radiative couplingVictim (wifi, bluetooth, GSM, etc.) Attacker A near field inductive coupling in between the leech and V’s card (passport) Attacker B distance < 0,5 m (cf. following discussion) near field inductive coupling in between the ghost and the inspection terminal SmartCard Forum 2011, Prague 20.
Wormhole Attack SchemePICC L2H link Leech Leechorig. host H2H link (using e.g. radiative coupling) inductive coupling Ghost G2H link PCD Ghost host orig.Leech Fake PCD inductive couplingLeech host Computing device driving the leechGhost Fake PICCGhost host Computing device driving the ghost SmartCard Forum 2011, Prague 21.
Do-It-Yourself Wormhole LA: 4 turns of plain LA LA = L B LBCUL wire, coil  75 mm same as LA coax. RG 58 length  ’/2 (tested  2m) SmartCard Forum 2011, Prague 22.
Wormhole In Access Control Picture shows a real successful experiment with the DIY wormhole.SmartCard Forum 2011, Prague 23.
Range Extension Limits The very principal limit is given by near/far field threshold, which is approximately  / 2  3.52 m In [25], practically achievable limit is estimated to be 0.5 m (at cost < $100 in year 2005).  This is the distance we shall assume in risk assessments. Using of-the-shelf devices modification, communication at around 15-25 cm shall be achievable using home- grown development [13], [15], [26].  Basing on our own practical experiments, we agree with [13] results and conclusion stating that: “That said, 15 cm or 20 cm is enough to execute an attack in a crowded area and easily allows reading of a token in somebody’s pocket or bag.”  See also skimming attack presentations [21], [22]. SmartCard Forum 2011, Prague 24.
Part FOURHacking Into & With NFCSmartCard Forum 2011, Prague 25.
NFC at Glance NFC stands for Near Field Communication Device equipped with an NFC controller can work in the following modes:  Passive-mode initiator (or just a “PCD”)  Passive-mode target (or just a “PICC”)  Active-mode initiator/target (or just “PCD-to-PCD”) SmartCard Forum 2011, Prague 26.
NFC and ISO 14443 NFC-equipped device can address contactless smartcards world in two ways:  As a PCD  ISO 14443 A – passive-mode initiator  As a PICC  ISO 14443 A – passive-mode targetSmartCard Forum 2011, Prague 27.
NFC and Mobile Phones At this moment, several incompatible architectures exist.  We can call them “generation zero” devices.  Interesting survey is given in [40]. Approaching version of “generation one” devices shall:  Include special HW module called CLF (Contactless Front- end).  Interconnect CLF directly with SIM card, so the SIM will serve the role of a secure element.  Also provide certain monitor connection in between CLF and phone’s main processor. SmartCard Forum 2011, Prague 28.
NXP’s Controllers OverviewChip Interface PCD PICC Level 4 Mode Mode FramingPN531 I2C, SPI, USB ISO 14443-A ISO 14443-A PCD onlyPN532 I2C, SPI ISO 14443-A/B ISO 14443-A PCD & PICCPN533 USB ISO 14443-A/B ISO 14443-A PCD & PICC Table presents summary of NFC controllers of PN53x family made by NXP [32].  Simplified viewpoint based on wormhole attacks on ISO 14443.  Further details can be also found in [28].  Although variant-A-only support in PICC mode seems to be a limiting condition, it is actually not the case (cf. elaboration given in part V). SmartCard Forum 2011, Prague 29.
Hacking Into & With NFC When successfully mastered, an NFC-capable device is a vital tool for any security analyst.  Mainly the passive-mode target promises, obviously, many interesting applications. The whole approach has, however, two steps:  Hacking into NFC. While it is relatively easy to buy a device with an NFC controller, it is much harder to get full documentation for it.  Even the NFC controllers themselves try to somehow limit their usage for an attacking purpose – by e.g. UID setting obstacles.  Very important and useful project is www.libnfc.org [28].  Hacking with NFC. The NFC devices can be used to implement e.g. wormhole or MITM attack, etc. SmartCard Forum 2011, Prague 30.
Part FIVEExperiments With libnfcSmartCard Forum 2011, Prague 31.
libnfc at Glance According to the libnfc authors: “…libnfc is the first free NFC SDK and Programmers API released under the GNU Lesser General Public License. It provides complete transparency and royalty-free use for everyone…” [28]. As far, as we can confirm, the aforementioned statement is true.  It is quite easy to (even unintentionally) buy an NFC- equipped device, while, on the other hand, it is considerably harder to get full programmer’s documentation and support for it.  libnfc commendably dares to remove this barrier. SmartCard Forum 2011, Prague 32.
libnfc Internals NFCIP-1 API Provide connection initialization an communication with an RF inductively coupled counterpart (ISO 18092). NFC controller drivers Provide monitor (firmware) commands wrappers for a particular NFC controller chipset. device drivers Provide monitor mode communication with an NFC controller embedded inside a particular peripheral device. bus drivers Provide data communication with an NFC-capable device (also cover L2H and G2H links).Table illustrates libnfc internal structure in a layered model form.Despite not being an official picture provided by libnfc core team, we assume it is quiteaccurate – with respect to source code structure at least. SmartCard Forum 2011, Prague 33.
Principal Obstacles There are two obvious obstacles regarding usage of PN53x controllers. 1. UID of the ghost device cannot be set to an arbitrary value. 2. The ghost device cannot work under ISO 14443 – variant B standard. The following discussion shows how to overcome these potential issues. SmartCard Forum 2011, Prague 34.
Experimental Achievements Using libnfc, we have successfully realized wormhole attack on the electronic passport application.  In place of an inspection terminal, we have used a demo application reading a BAC-equipped passport on PC with a popular dual smartcard reader CardMan 5321.  The passport was chosen as a typical contactless smartcard application. For a robust and fault-tolerant practical attack, we, however, suggest mounting the wormhole on the transport or application layer.  Nevertheless, this is still easily achievable, especially by using PN532 or PN533 which have built-in firmware support for transport layer framing.  libnfc v. 1.4.2. already provides certain sample application support for this approach. SmartCard Forum 2011, Prague 35.
Experimental Setup HOST inc. H2H linkL2Hlink G2H link original PCDleech SmartCard Forum 2011, Prague original PICC ghost 36.
Timing Constraints II We can summarize the results as follows:  For the H2H link: Even the internet connection is sufficient, provided there is a roundtrip delay (ghost to leech and back) less than several seconds.  For the L2H and G2H links: Local roundtrip must be less than approx. 20 ms. Otherwise, the PCD may reject late responses to RATS.  Nevertheless, this allows using short range bluetooth or wifi links, which may be enough to perform the attack demonstration in e.g. airport lobby. SmartCard Forum 2011, Prague 37.
Antenna Geometry I Sometimes, the PCD requires the card to be inserted inside an aperture similar to a contact card reader. There is a question on whether an of- the-shelf ghost device can be used to emulate the original card under such conditions.SmartCard Forum 2011, Prague 38.
Antenna Geometry II Inspiration can be found in the DIY wormhole presented above.  We simply use a suitable antenna transformer.  Its secondary coil is shaped to fit inside the PCD’s aperture while the primary one is fastened at the ghost device.  We suggest considering PCB layout and 1:1 ratio for the transformer coils, although particular situation may require slightly different approach. Anyway, it is an easy and funny experimentation, not a rigid obstacle. So, using such apertures cannot be regarded as a countermeasure against wormhole attacks. SmartCard Forum 2011, Prague 39.
Conclusion Because of the wide availability of NFC controllers and libraries, the following is true:  Using generally available computing devices and program codes, it is practically easy to mount a wormhole attack in a typical system accepting ISO 14443 contactless smartcards.SmartCard Forum 2011, Prague 40.
References I1. Axelson, J.: USB Complete: Everything You Need to Develop USB Peripherals, 3rd Ed., Lakeview Research LLC, 20052. Beth, T. and Desmedt, Y.: Identification Tokens – Or: Solving the Chess Grandmaster Problem, In Proc. of CRYPTO ’90, pp. 169-176, Springer-Verlag, 19913. Brands, S. and Chaum, D.: Distance-Bounding Protocols, In Proc. of EUROCRYPT ’93, pp. 344–359, Springer-Verlag, 19944. Desmedt, Y.: Major Security Problems with the ‘Unforgeable’ (Feige)-Fiat- Shamir Proofs of Identity and How to Overcome Them, SecuriCom ’88, SEDEP Paris, pp. 15-17, 19885. Desmedt, Y., Goutier, C., and Bengio, S.: Special Uses and Abuses of the Fiat- Shamir Passport Protocol, In Proc. of CRYPTO ’87, pp. 16-20, Springer- Verlag, 19886. Development of a Logical Data Structure – LDS for Optional Capacity Expansion Technologies, ICAO, ver. 1.7, 20047. Dobkin, D.: The RF in RFID: Passive UHF RFID in Practice, Elsevier Inc., 20088. Drimer, S. and Murdoch, S.-J.: Relay Attack on Card Payment – Vulnerabilities and Defences, Conference 24C3, December 2007 SmartCard Forum 2011, Prague 41.
References II9. EMV Contactless Specifications for Payment Systems, EMV Contactless Communication Protocol Specification, v. 2.0.1, July 200910. Finke, T. and Kelter, H.: Abhörmöglichkeiten der Kommunikation zwischen Lesegerät und Transponder am Beispiel eines ISO14443-Systems, BSI - German Federal Office for Information Security, 200511. Finkenzeller, K.: RFID Handbook – Fundamentals and Applications in Contactless Smart Cards and Identification, John Willey and Sons Ltd., 200312. Francillon, A., Danev, B., and Čapkun, S.: Relay Attacks on Passive Keyless Entry and Start Systems in Modern Cars, IACR ePrint Report 2010/332, 201013. Hancke, G.: Practical Eavesdropping and Skimming Attacks on High-Frequency RFID Tokens, Journal of Computer Security, accepted to be published 201014. Hancke, G.: Eavesdropping Attacks on High-Frequency RFID Tokens, 4th Workshop on RFID Security (RFIDSec), July 200815. Hancke, G.: Practical Attacks on Proximity Identification Systems (Short Paper), In Proc. of IEEE Symposium on Security and Privacy, pp. 328-333, 200616. Hancke, G.-P.: A Practical Relay Attack on ISO 14443 Proximity Cards, Tech. Report, 2005 SmartCard Forum 2011, Prague 42.
References III17. Hancke, G.: Research Homepage, http://www.rfidblog.org.uk/research.html18. Hancke, G.-P. and Kuhn, M.-G.: An RFID Distance Bounding Protocol, In SecureComm ’05, pp. 67-73, IEEE Computer Society, 200519. Hlaváč, M. and Rosa, T.: A Note on the Relay Attacks on e-passports: The Case of Czech e-passports, IACR ePrint Report 2007/244, 200720. ICAO - International Civil Aviation Organization, http://www.icao.int/21. Identity Theft - MIFARE Campus Card Skimming Attack (EN titles), http://www.youtube.com/watch?v=NW3RGbQTLhE22. Identity Theft - Prague Citizen Card Skimming Attack (CZ titles), http://www.youtube.com/watch?v=Yxvy_eGK5r423. Jelínek, L.: Jádro systému Linux - Kompletní průvodce programátora, Computer Press, a.s., Brno 200824. Kasper, T.: Embedded Security Analysis of RFID Devices, Diploma Thesis, Ruhr-University Bochum, July 2006 SmartCard Forum 2011, Prague 43.
References IV25. Kfir, Z. and Wool, A.: Picking Virtual Pockets using Relay Attacks on Contactless Smartcard Systems, IACR ePrint Report 2005/052, 200526. Kirschenbaum, I. and Wool, A.: How to Build a Low-Cost, Extended-Range RFID Skimmer, USENIX 200627. Lee, Y.: Antenna Circuit Design for RFID Applications, Application Note 710, Microchip Tech. Inc., 200328. libnfc.org - Public platform independent Near Field Communication (NFC) library, www.libnfc.org29. Long range HF RFID demonstrator – DEMO90121LR, Melexis, http://www.melexis.com/General/General/DEMO90121LR_662.aspx30. Menezes, A.-J., van Oorschot, P.-C., and Vanstone, S.-A.: Handbook of Applied Cryptography, CRC Press, 199631. Myslík, J.: Elektromagnetické pole - základy teorie, BEN - technická literatura, Praha 199832. Overview of Technical NFC Documents, includes PN53x documentation catalogue, NXP, March 2009, http://www.nxp.com/documents/other/nfc_documentation_overview.pdf SmartCard Forum 2011, Prague 44.
References V33. PKI for Machine Readable Travel Documents offering ICC Read-Only Access, IACO, ver. 1.1, 200434. S2C Interface for NFC, Survey VI.0, Philips, 200535. PC/SC Workgroup Specifications, http://www.pcscworkgroup.com/specifications/overview.php36. Rosa, T.: PicNic - Yet Another Emulator/Spyware for HF RFID, technical project 2008 – 2010, http://crypto.hyperlink.cz/picnic.htm37. Rosa, T.: SCL3710 USB Dongle Config-based SHORT-CIRCUIT Found, libnfc developers forum, 2010, http://www.libnfc.org/community/topic/194/scl3710-usb-dongle- configbased-shortcircuit-found/38. Rosa, T.: Passive Target Mode Initialization *Without* Secondary Reader, libnfc developers forum, 2010, http://www.libnfc.org/community/topic/200/passive-target-mode- initialization-without-secondary-reader/39. Vinculum-I device datasheet, application notes, drivers, and prototyping boards, http://www.ftdichip.com40. Weiss, M.: Performing Relay Attacks on ISO 14443 Contactless Smart Cards using NFC Mobile Equipment, Master’s Thesis in Computer Science, Fakultät Für Informatik, Der Technischen Universität München, May 201041. Fleisch, D.: A Student’s Guide to Maxwell’s Equations, Cambridge University Press, New York 2008. SmartCard Forum 2011, Prague Recommended

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