1,400 research outputs found
LA CORTE INTER-AMERICANA E LA CORTE EUROPEA DEI DIRITTI DELL’UOMO: DA UN TRANS-REGIONAL JUDICIAL DIALOGUE AD UNA CROSS-FERTILIZATION?
No full textLong-Term Outcome of Otherwise Healthy Individuals with Incidentally Discovered Borderline Thrombocytopenia.
No full textBACKGROUND: The long-term outcome of individuals with mild degrees of thrombocytopenia is unknown. METHODS AND FINDINGS: In a prospective study conducted between August 1992 and December 2002, 260 apparently healthy individuals with incidentally discovered platelet counts between 100 x 10(9)/l and 150 x 10(9)/l were monitored for 6 mo to determine whether their condition persisted. The monitoring period was completed in 217 cases, of whom 191 (88%) maintained stable platelet counts. These 191 individuals were included in a long-term follow-up study to gain knowledge of their natural history. With a median time of observation of 64 mo, the thrombocytopenia resolved spontaneously or persisted with no other disorders becoming apparent in 64% of cases. The most frequent event during the study period was the subsequent development of an autoimmune disease. The 10-y probability of developing idiopathic thrombocytopenic purpura (ITP), as defined by platelet counts persistently below 100 x 10(9)/l, was 6.9% (95% confidence interval [CI]: 4.0%-12.0%). The 10-y probability of developing autoimmune disorders other than ITP was 12.0% (95% CI: 6.9%-20.8%). Most of the cases (85%) of autoimmune disease occurred in women. CONCLUSIONS: Healthy individuals with a sustained platelet count between 100 x 10(9)/l and 150 x 10(9)/l have a 10-y probability of developing autoimmune disorders of 12%. Further investigation is required to establish whether this risk is higher than in the general population and whether an intensive follow-up results in an improvement of prognosis
Application of EKF to parameter and state estimation of PMSM drive
No full textThe authors describe the application of the extended Kalman filter theory to the parameter and state estimation of a permanent-magnet synchronous motor drive for a microprocessor based adaptive speed control in the presence of a variable load. The electronically commutated permanent magnet synchronous motor is controlled according to the principle of field orientation. An adaptive torque/speed cascade control is used to improve the performance of the system which has constrained armature current and unknown load inertia. The parameters of the controllers of the two feedback loops and that of the smoothing filter are adjusted when the changes in the load parameters have been tracked down by the estimation algorithm. The proposed estimator and the adaptive control scheme have been simulated, the results show that they perform well
Design of Four Fuzzy Controllers for Induction Motor Drives
No full textThis paper presents a simple method to design four fuzzy controllers of a fully digital vector-controlled induction motor drive. The outer controllers realise the usual rotor speed and flux control, while the inner controllers are used to control the d- and q-axis stator current components. The design method is based on physical relationships, because accurate model structures of electrical machines are available. The use of fuzzy controllers increases the robustness of the drive to external disturbances and load. The inherent nonlinear characteristics of the fuzzy controllers make it possible to obtain fast and accurate tracking of rotor flux and speed references, and to control the d- and q-axis current components in presence of varying load conditions, changes of mechanical parameters, process nonlinearities, and inaccuracy in the process modelling
Adaptive position control of a PMSM drive
No full textThis paper proposes a self-tuning control system for the positioning of a PM synchronous motor. The auto-tuning control system is realized with a conventional position P-regulator, a derivative position feedback with adjustable gain, and a new online estimator, based on the extended Kalman filter theory, which provides the estimates to update the gains and the feedforward load compensation term. Simulation results demonstrate that the adaptive control system maintains the desired control over position in the presence of varying mechanical parameter
Design Method of Fuzzy Controllers for Speed and Current Control Loops of DC Motor Drives
No full textMonitoring of Inverter Drives in Time-Frequency Domain
No full textThis paper proposes to apply the Wigner-Ville distribution
(WVD) or, alternatively, a "new" time-frequency
representation (TFR) to voltage and current signals of
inverter drives to monitor instantaneous complex power,
voltage and current space-vectors in the time-frequency
domain. The WVD and TFR satisfy the following
properties: the frequency integral is the instantaneous
power and the time integral is the spectral energy
distribution. Therefore, both techniques are powerful
mathematical tools to describe the behaviour of inverter drives and that of unbalanced and non-sinusoidal three-phase systems. The new TFR is preferable because
shows correct information about the frequency locations of the spectral components, while the WVD does not. We
show the results of applying the new time frequency
representation
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