An improved sliding mode observer is presented to estimate the rotor position of the permanent magnet synchronous motors (PMSMs). In this observer, the discontinuous control is replaced by using the sigmoid function in order to reduce the chattering problem commonly found in the conventional sliding mode observer. When the chattering is reduced, the back emf can be obtained directly from the sw...

Most small wind turbines use permanent magnet (PM) generators. The generators are usually direct-drive (i.e., no gearbox is required). Direct-drive PM generators are characterized by low maintenance and high efficiency. Small wind turbines are usually self-starting and require very simple controls. Cogging torque is an inherent characteristic of PM generators and is caused by the geometry of th...

Sensorless control of Permanent-Magnet Synchronous Motors (PMSM) at low velocity remains a challenging task. A now well-established method consists in injecting a highfrequency signal and use the rotor saliency, both geometric and magnetic-saturation induced. This paper proposes a clear and original analysis based on second-order averaging of how to recover the position information from signal ...

This paper compares traditional averagesbased model with other various age estimation models in the range from the simplest to the advanced ones, and introduces novel Tabular Constrained Multiple-linear Regression (TCMLR) model. This TCMLR model has similar complexity as traditional averages-based model (it can by evaluated manually), but improves the mean absolute error in average about 0.30 y...

This paper presents the modelling of asymmetries of phase parameters (inductances) of permanent magnet (PM) synchronous motor and the analysis of the impact of these asymmetries on the instantaneous torque. The torque ripple created by phase asymmetries is simulated for three operating conditions – current-fed, voltage-fed and vector control operation, using specifically developed mathematical ...

The note describes measurement of NdFeB permanent magnet (PM) material demagnetization induced by high-energy electron radiation. In experiments we compared N40 and N40SH grades from Stanford Magnets Company, which have different intrinsic coercive forces. Dimensions of the tested PM blocks were close to those that will be used for ERL undulator construction. It was found that depending on dire...

The present paper refers to some examples that use the finite element method (FEM) in the process of analysis, design and optimization of the permanent magnet (PM) generators used in wind applications. The 2D-FEM program Opera 13 of Vector Fields is used in the analyzed examples. These examples refer to two types of radial flux low speed PM generators of 5 KW for wind applications. Some possibi...

The Permanent Scatterers (PS) technique, invented by Politechnico di Milano research team, is an approach that minimises the undesirable noise components in the classic InSAR technique, such as spatial and temporal decorrelations, signal delay due to tropospheric and ionospheric disturbances, orbital errors as well as topographical errors. This approach is suitable for the measurement of near v...

Detailed oro-maxillofacial studies using dental casts, pantomograms and cephalograms were performed in 28 patients with Turner's syndrome and compared statistically to the results from 23 normal short children. Small tooth crown size, short tooth roots and advanced dental age were characteristic of patients with Turner's syndrome. However, the incidence of peg shaped teeth, malocclusion, high a...