Radial force control for triple three-phase sectored SPM machines. Part II: Open winding fault tolerant control

A new advanced fault tolerant control technique for a triple three-phase Surface Permanent Magnet (SPM) machine is investigated in this paper. The machine has a nine-phase winding arranged in three sectors and supplied by three different Voltage Source Inverters (VSIs). The proposed current control technique is firstly exploited to avoid the radial force appearance in case of open winding of one machine sector. Then, the radial force fault tolerant control is improved to compensate for a bearing fault or another source of radial force in this open winding condition. Finite element simulations are used to validate the two proposed control techniques. Finally, advantages and drawbacks of the solution are highlighted

A metrological characterization of the Kinect V2 time-of-flight camera

A metrological characterization process for time-of-flight (TOF) cameras is proposed in this paper and applied to the Microsoft Kinect V2. Based on the Guide to the Expression of Uncertainty in Measurement (GUM), the uncertainty of a three-dimensional (3D) scene reconstruction is analysed. In particular, the random and the systematic components of the uncertainty are evaluated for the single sensor pixel and for the complete depth camera. The manufacturer declares an uncertainty in the measurement of the central pixel of the sensor of about few millimetres (Kinect for Windows Features, 2015), which is considerably better than the first version of the Microsoft Kinect (Chow et al., 2012 [1]). This work points out that performances are highly influenced by measuring conditions and environmental parameters of the scene; actually the 3D point reconstruction uncertainty can vary from 1.5 to tens of millimetres

Multiphase electric drives for "More Electric Aircraft" applications

Advances in power electronic and machine control techniques are making the inverter-fed drives an always more attractive solution. Because of the number of inverter legs is arbitrary, also the number of phases results as a further degree of freedom for the machine design. Therefore, the multiphase winding is often a possible solution. Due to the increasing demand for high performance and high power variable speed drives, the research on multiphase machines has experienced a significant growth in the last two decades. Indeed, one of the main advantages of the multiphase technology is the possibility of splitting the power of the system across a higher number of power electronic devices with a reduced rating. A similar result can be obtained by using multi-level converters. However, the redundancy of the phases leads to an increased reliability of the machine and to the introduction of additional degrees of freedom in the current control and the machine design. This work aims to study and analyze the highly reliable and fault tolerant machines. It proposes innovative solutions for multiphase machine design and control to meet the safety-critical requirements in “More-Electric Aircraft” (MEA) and “More Electric Engine” (MEE) in which thermal, pneumatic or hydraulic drives in aerospace applications are replaced with electric ones. Open phase, high resistance and short circuit faults are investigated. Fault tolerant controls and fault detection algorithms are presented. Radial force control techniques and bearingless operation are verified and improved for various working scenarios. Fault tolerant designs of multiphase machines are also proposed

Radial force control for triple three-phase sectored SPM machines. Part I: Machine model

The radial force control technique for a triple three-phase Surface Permanent Magnet (SPM) machine is investigated in this paper. The machine has a nine-phase winding arranged in three sectors and supplied by three different Voltage Source Inverters (VSI). A machine model is developed, based on the multi space vector approach. The multi space vector current control technique is exploited to control the torque and the radial force. The radial force control can be useful to compensate for a bearing fault or for a rotor eccentricity. Finite element simulations are used to validate the model and the control technique. Finally, criticalities of the control and modelling aspects are discussed

Orbital Hanle Magnetoresistance in a 3d Transition Metal

The Hanle magnetoresistance is a telltale signature of spin precession in nonmagnetic conductors, in which strong spin-orbit coupling generates edge spin accumulation via the spin Hall effect. Here, we report the existence of a large Hanle magnetoresistance in single layers of Mn with weak spin-orbit coupling, which we attribute to the orbital Hall effect. The simultaneous observation of a sizable Hanle magnetoresistance and vanishing small spin Hall magnetoresistance in BiYIG/Mn bilayers corroborates the orbital origin of both effects. We estimate an orbital Hall angle of 0.016, an orbital relaxation time of 2 ps and diffusion length of the order of 2 nm in disordered Mn. Our findings indicate that current-induced orbital moments are responsible for magnetoresistance effects comparable to or even larger than those determined by spin moments, and provide a tool to investigate nonequilibrium orbital transport phenomena

Deterministic and stochastic aspects of current-induced magnetization reversal in perpendicular nanomagnets

We study the incubation and transition times that characterize the magnetization switching induced by spin-orbit torques in nanomagnets with perpendicular anisotropy. We present a phenomenological model to interpret the dependence of the incubation time on the amplitude of the voltage pulse and assisting magnetic field and estimate the volume of the seed domain that triggers the switching. Our measurements evidence a correlation between the incubation and transition times that is mediated by the temperature variation during the electric pulse. In addition, we discuss the stochastic distributions of the two times in terms of the energy barriers opposing the nucleation and expansion of the seed domain. We propose two models based on the log-normal and gamma functions to account for the different origin of the variability of the incubation and transition times, which are associated with a single nucleation barrier and multiple pinning sites, respectively

Charge response function probed by resonant inelastic x-ray scattering: the signature of electronic gaps of YBa2_2Cu3_3O7−δ_{7-\delta}

In strongly correlated systems the complete determination of the dynamical susceptibility $\chi(\textbf{q}, \omega)$ is of special relevance because of the entwinement of the spin and charge components. Although Resonant Inelastic X-Ray Scattering (RIXS) spectra are directly related to both the charge ($\chi''_c(\textbf{q}, \omega)$) and the spin ($\chi''_s(\textbf{q}, \omega)$) contributions, only the latter has been extensively studied with RIXS so far. Here we show how to extract from RIXS spectra of high-$T_c$ superconducting cuprates relevant properties of $\chi''_c$, such as the presence of the superconducting gap and of the pseudogap. In particular, we exploit the temperature dependence of the Cu L$_3$ edge RIXS spectra of underdoped YBa$_2$Cu$_3$O$_{7-\delta}$ at specific wave-vectors q. The signature of the two gaps is in the departure of the low energy Bosonic excitation continuum from the statistical temperature-dependence. This approach can be immediately used to investigate systematically the nature of the pseudogap in cuprates, thereby taking advantage of the RIXS technique that does not suffer the limitations of surface-sensitive electron spectroscopies. Its extension to other interesting materials is foreseen.Comment: 11 pages, 9 figure

Charge response function probed by resonant inelastic x-ray scattering: Signature of electronic gaps of YBa2Cu3O7−δ

In strongly correlated systems, the complete determination of the dynamical susceptibility chi(q, omega) is of special relevance because of the entwinement of the spin and charge components. Although resonant inelastic x-ray scattering (RIXS) spectra are directly related to both the charge [chi ''(c)(q, omega)] and the spin [chi ''(s)(q, omega)] contributions, only the latter has been extensively studied with RIXS so far. Here we show how to extract from RIXS spectra of high-T-c superconducting cuprates relevant properties of chi ''(c), such as the presence of the superconducting gap and of the pseudogap. In particular, we exploit the temperature dependence of the Cu L-3 edge RIXS spectra of underdoped YBa2Cu3O7-delta at specific wave vectors q. The signature of the two gaps is given by the departure of the low-energy excitation continuum from the Bosonic thermal evolution. This approach can be immediately used to investigate systematically the nature of the pseudogap in cuprates, thereby taking advantage of the RIXS technique that does not suffer the limitations of surface-sensitive electron spectroscopies. Its extension to other interesting materials is foreseen