In patients with implanted rotary pumps, the arterial pressure pulsatility is usually far lower than in normal individuals. Depending on the remaining degree of pulsatility, cuff-based systems such as the classical Riva-Rocci-determination of arterial blood pressure and correlated sounds or pressure measurements based on cuffpressure oscillations become inaccurate or even impossible. Therefore, a system was developed which evaluates the flow in the radial artery using an ultrasound wristwatch sensor, and this additional information is used for pressure determination. A computerized data acquisition and cuff-control system based on a PC using Matlab software, a wristwatch ultrasound device, and a compressor-driven pressure cuff was set up. The cuff was controlled for automatic inflation and deflation cycles. Cuff pressure and arterial flow was recorded. Several algorithm strategies were developed, which gave data for systolic blood pressure and heart rate together with a reliability index for data quality. Finally, the new algorithms were implemented in a microcontroller system. Comparisons with invasive measurements showed excellent correlation with systolic blood pressure (mean deltaP -0.3 mm Hg, n = 28). During exercise of rotary pump patients and therefore enhanced pulsatility the difference from manual evaluation was -2.1 mm Hg (n = 18). In conclusion, adaptation of the classical cuff-pressure method with ultrasound evaluation of peripheral flow allows reliable determination of blood pressure in patients with low pulsatility resulting from implanted rotary cardiac assist pumps. By development of a wristwatch sensor and an automatic control system a robust method for daily use could be developed.

In clinical application of rotary blood pumps, flow obstruction as a result of suction of the inflow cannula, kinking of tubing, or thrombus formation occurs quite frequently. Early detection of such problems is essential to avoid hemolysis, tissue degradation, or release of thrombi to the patient. A program was developed for automatic observation of pump performance, tubing resistance, and suction effects, which requires only the measurement of already available parameters (i.e., pump speed, pump flow, aortic pressure). The software is based on Visual-C and provides a user surface formatted in Windows. Pump flow, its time derivate, and the relationship between the pulsatile component and the mean graft flow are observed to detect suction in the left atrium. Furthermore, the generated pressure head is predicted from pump speed, graft flow, and the resistance of tubing/cannula and compared with the actually measured aortic pressure. An alarm sounds if a given limit between prediction and measurement is exceeded. In a mock circulation, suction events were detected in more than 95% with a mean deviation of actual aortic pressure from its predicted value of less than 5%. For in vivo application, even incomplete suction could be detected reliably in more than 90% of events. This system improves and standardizes monitoring of pump performance; it should therefore lead to greater safety during application of such devices.

Fuzzy-Regelungen stellen auf Grund der nichtlinearenEigenschaften des Fuzzy-Reglers stets nichtlineare Regelkreise dar. Die Analyse der Stabilität eines solchen Regelkreises mit Hilfe der Hyperstabilitätstheorie geht davon aus, daß dieser in einen nichtlinearen Standardregelkreis -bestehend aus einem linearen und einem nichtlinearen Teilsystem -umgeformt wird. Diese Teilsysteme sind dann unter Beibehaltung der dynamischen Eigenschaften des Gesamtregelkreises fiktiv so zu verän-dern, daß bestimmte -im Sinne der Hyperstabilitäts-theorie für Stabilität hinreichende -Bedingungen womöglich erfüllt sind. Im vorliegenden Beitrag wird gezeigt, wie bei diesen fiktiven Veränderungen neben notwendigen Parametern noch zusätzliche freie Parameter und Freiheitsgrade eingeführt werden können. Damit soll erreicht werden, daß die Stabilitätsanalyse für alle nichtlinearen Standardregelkreise erfolgen kann, deren nichtlineares Teilsystem eine beliebige eindeutige nichtlineare Funktion darstellt, und daß vor allem die Stabilitätsanalyse möglichst wenig konservativ wird, worunter zu verstehen ist, daß die hinreichenden Bedingungen für Stabilität der tatsächlichen Stabilitätsgrenze möglichst nahekommen sollen. On the stability analysis of fuzzy control systems using hyperstability theoryFuzzy control systems belong to the class of nonlinear control systems because of the nonlinear behaviour of the fuzzy controller. To analyse the stability properties of such a system using hyperstability theory, it is necessary to transform the system into a standard nonlinear control loop consisting of a linear and a nonlinear subsystem. Further loop transformations are applied to this control loop without affecting the dynamical properties of the closed loop system. By these transformations it is tried to make the mentioned subsystems satisfy the hyperstability conditions which are sufficient for stability.In this paper it is shown, how additional free parameters can be introduced into these transformations besides necessary parameters in order to make the stability analysis applicable to all nonlinear subsystems described by an arbitrary unique nonlinear mapping and to make the stability analysis less conservative. The latter means to strive for sufficient stability conditions nearer to the stability limit.

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Ausgehend von der mathematischen Modellierung einer sensorlos betriebenen Permanentmagnet-Synchronmaschine wird ein sensorloses Low-Cost-Positioniersystem vorgestellt und einem sensorbehafteten System gegenª Dabei werden die Vorteile und Grenzen des sensorlosen Systems dokumentiert. Untersuchungen und Messungen an einem praktisch aufgebauten Antrieb zeigen, dass fª viele Applikationen mittlerer Genauigkeit eine kostengª mechanisch robuste Positionsregelung mit Permanentmagnet-Synchronantrieben realisiert werden kann. SchlªPermanentmagnet-Synchronmaschine; lagegeregelter Antrieb; sensorlose Regelung; feldorientierte Regelung; Servoantrieb; Positionsregelung Dynamics of mechanically robust, position-controlled sensorless direct drives with permanent magnet synchronous machines.Starting from a mathematical description of the sensorless permanent magnet synchronous motor a sensorless low-cost positioning system is introduced and compared to a conventional one with position measurement. Extensive examinations and measurements on a realized sensorless positioning system verify the suitability of the presented method for a lot of applications with medium accuracy demand.