Modeling, Analysis and Testing of a Novel Spoke-Type Interior Permanent Magnet Motor with Improved Flux Weakening Capability

Spoke-type interior permanent magnet (IPM) machines are an attractive topology for high performance electric motors, especially designed for vehicle traction applications. In this paper, a special design for a spoke-type IPM motor is presented to enhance motor flux-weakening capability in the operation over a wide speed range. The proposed design consists of a simple and robust mechanical device that includes radially-displaceable rotor yokes, connected to the shaft by means of springs. At high speed, the centrifugal force prevails over the elastic one due to springs, causing the mobile yokes to displace radially and to establish a partial magnetic short circuit between permanent magnets. This increases permanent magnet leakage flux and consequently reduces the air-gap field. As a result, a mechanical flux weakening effect is achieved at high speed, which helps significantly reduce the demagnetizing d-axis current to be injected by the inverter, along with the related copper losses and demagnetization issues. The proposed design is investigated in the paper using an analytical model whose parameters are computed by finite-element analysis (FEA). The effectiveness of the solution being set forth is successfully proven by some testing on a laboratory prototype. Experimental results are compared to analytical predictions showing a satisfactory accordance

Optimal Selection of Rotor Bar Number in Multiphase Cage Induction Motors

Rules for the selection of rotor bar numbers which minimize current and torque ripples are derived in this paper for a general symmetrical multiphase cage induction machine with prime phase number and integral slot winding. Analytically obtained expressions for optimal rotor bar number selection are validated by means of totally independent simulations, one based on a parameterized winding function (PWF) model of the induction machine and the other employing time-stepping finite element analysis (TSFEA). As a case study, five-phase four-pole cage induction motors with forty stator slots and different number of rotor bars are comparatively analyzed. Results obtained from the PWF model are in excellent accordance with those independently obtained by TSFEA and both confirm the correctness of the proposed selection criteria. The practical motivation of the study is that an incorrect selection of rotor bar number can lead to parasitic torques of significant amplitude and, presently, there are no general rules available in the literature which may guide designers towards an optimal design choice for a general number of phases

Investigation into Multi-Layer Fractional-Slot Concentrated Windings with Unconventional Slot-Pole Combinations

Fractional-slot concentrated windings (FSCWs) are an attractive option for the design of synchronous permanent-magnet machines. It is commonly assumed in the existing literature that a symmetrical three-phase FSCW is feasible only on a condition that the number of slots Z is an integer multiple of three times the maximum common divisor between Z and the number of pole pairs p. Slot-pole combinations satisfying this rule can be defined conventionally, the others unconventionally. In contrast to the common belief, this paper shows that, using a multi-layer arrangement, it is possible to synthetize a symmetrical FSCW having unconventional slot-pole combinations. A general design methodology for this purpose is presented and validated by finite element analysis. The pros and contras of FSCWs with unconventional slot-pole combinations are examined. Finally, the application of an unconventional FSCW to a shipboard surface permanent-magnet machine prototype is presented to illustrate the possible practical convenience of this kind of winding and tests on the prototype are reported for experimental validation

The expected signature of Brownian motion stopped on the boundary of a circle has finite radius of convergence

The expected signature is an analogue of the Laplace transform for probability measures on rough paths. A key question in the area has been to identify a general condition to ensure that the expected signature uniquely determines the measures. A sufficient condition has recently been given by Chevyrev and Lyons and requires a strong upper bound on the expected signature. While the upper bound was verified for many well‐known processes up to a deterministic time, it was not known whether the required bound holds for random time. In fact, even the simplest case of Brownian motion up to the exit time of a planar disc was open. For this particular case we answer this question using a suitable hyperbolic projection of the expected signature. The projection satisfies a three‐dimensional system of linear PDEs, which (surprisingly) can be solved explicitly, and which allows us to show that the upper bound on the expected signature is not satisfied

Postural control deficit during Sit-To-Walk in patients with Parkinson\u2019s Disease and Freezing of Gait

Introduction The intricate linkage between Freezing of Gait (FoG) and postural control in Parkinson's disease (PD) is unclear. We analyzed the impact of FoG on dynamic postural control. Methods 24 PD patients, 12 with (PD\u202f+\u202fFoG), 12 without FoG (PD-FoG), and 12 healthy controls, were assessed in ON state. Mobility and postural control were measured with clinical scales (UPDRS III, BBS, MPAS) and with kinematic and kinetic analysis during three tasks, characterized by levels of increasing difficulty to plan sequential movement of postural control: walk (W), gait initiation (GI) and sit-to-walk (STW). Results The groups were balanced by age, disease duration, disease severity, mobility and balance. During STW, the spatial distribution of COP trajectories in PD\u202f+\u202fFoG patients are spread over medial-lateral space more than in the PD-FoG (p\u202f<\u202f.001). Moreover, the distribution of COP positions. in the transition between sit-to-stand and gait initiation, is not properly shifted toward the leading leg, as in PD-FoG and healthy controls, but it is more centrally dispersed (p\u202f<\u202f.01) with a delayed weight forward progression (p\u202f<\u202f.05). In GI task and walk task, COM and COP differences are less evident and even absent between PD patients. Conclusion PD\u202f+\u202fFoG show postural control differences in STW, compared with PD-FoG and healthy. Different spatial distribution of COP trajectories, between two PD groups are probably due to a deficit to plan postural control during a more demanding motor pattern, such as STW

Design and simulation of a vehicle-To-grid system

Batteries of electric vehicles have to be charged by power electronic converters connected to the electric grid. If these power converters are bidirectional they can be exploited to act in support to the grid operation, thus realizing the so called vehicle-To-grid (V2G) systems. At the University of Trieste an experimental V2G apparatus is under construction. Its control system has been developed and the first simulation tests has been performed. The paper describes the V2G experimental apparatus with its control system and reports the results of the preliminary simulation tests

Optimal Selection of Rotor Bar Number for Minimizing Torque and Current Pulsations due to Rotor Slot Harmonics in Three-Phase Cage Induction Motors

The paper develops a method to choose the number of rotor bars in order to eliminate rotor slot harmonics in stator current spectrum and pulsation torques that are their consequence. Mains-fed, three-phase cage induction motors with the most common number of pole pairs and number of stator slots, that result in integer slot winding, are analyzed. The analysis is based on the recently derived general rule for optimal selection of rotor bars, valid for symmetrical multiphase machine with prime number of phases and integer slot stator winding. As a tool for validation of analytically predicted results, parameterized winding function (PWF) model is used. Electromagnetic torque ripple factor is used as a measure of goodness of the number of rotor bar selection. The practical motivation of the study is an attempt to supersede the many existing rules for rotor bar number selection that, depending on the source, may be different, and provide a unified general approach to the problem. One of the main findings derived in the paper is ascertainment that increasing the number of pole pairs increases the degree of freedom in choosing the proper number of rotor bars. The same applies when the number of motor phases increases

Correlation between Quality of Life and severity of Parkinson's Disease by assessing an optimal cut-off point on the Parkinson's Disease questionnaire (PDQ-39) as related to the Hoehn & Yahr (H&Y) scale

Purpose: Strong evidence shows that symptoms in individuals with Parkinson's Disease (PD) restrict both their independence and social participation, leading to a low Quality of Life (QoL). Conversely, a reduced QoL has a negative impact on symptoms. The aim is to evaluate the correlation between QoL and severity of PD by assessing the presence of an optimal cut-off point on the Parkinson's disease questionnaire (PDQ-39) as related to the Hoehn &amp;Yahr (H&amp;Y) scale in a cohort of Italian adults with PD. Methods: A multicenter, cross-sectional study was performed. This study was conducted on a cohort of consecutive individuals. All participants were evaluated with the PDQ-39, and the severity of PD was recorded according to the H&amp;Y scale by a neurologist. Receiver op-erating characteristic (ROC) curves and coordinates, visually inspected, were used to find cut-off points with optimal sensitivity and specificity. These were in turn used to determine the optimal PDQ-39 cut-off score for identifying disease severity according to H&amp;Y stages. Results: 513 individuals were included in the study. The ROC curve analysis showed that QoL worsened with an increase in disease severity and age. Moreover, QoL was worse in females. Conclusions: The results of this study allowed for the correlation of QoL and disease severity in a cohort of individuals with PD. With this cut-off point, it is now possible to make a determination of QoL of an individual with PD at a certain stage of the disease, in a specific age range, and of a particular gender

The effect of music-induced emotion on visual-spatial learning in people with Parkinson's disease: A pilot study

Introduction: Emotional states have been shown to influence cognitive processes including visual-spatial learning. Parkinson's Disease (PD), besides manifesting with the cardinal motor symptoms, presents cognitive and affective disturbances. Here we aimed at investigating whether manipulation of the emotional state by means of music was able to influence the performance of a visual-spatial learning task in a group of PD participants. Methods: Ten PD patients and 11 healthy elderly (ELD) were asked to perform a visual-spatial learning task while listening two musical pieces evoking a neutral emotion or fear. Targets were presented on a screen in a preset order over four blocks and subjects were asked to learn the sequence order by attending to the display. At the end of each block, participants were asked to verbally recall the sequence and a score was assigned (Verbal Score, VS). Results: Analysis of variance-type statistic test on the VS disclosed a significant effect of Music and sequence Blocks (p = 0.01 and p &lt; 0.001, respectively) and a significant interaction between Group and sequence Blocks. Sequence learning occurred across the training period in both groups, but PD patients were slower than ELD and at the end of the training period learning performance was worse in PD with respect to ELD. In PD patients, like in ELD, fear-inducing music has a detrimental effect on visual-spatial learning performances, which are slower and decreased. Conclusion: These findings confirm an impairment in visual-spatial learning in PD and indicates that the emotional state influences this learning ability similarly to healthy controls

Robots, computer algebra and eight connected components

Answering connectivity queries in semi-algebraic sets is a long-standing and challenging computational issue with applications in robotics, in particular for the analysis of kinematic singularities. One task there is to compute the number of connected components of the complementary of the singularities of the kinematic map. Another task is to design a continuous path joining two given points lying in the same connected component of such a set. In this paper, we push forward the current capabilities of computer algebra to obtain computer-aided proofs of the analysis of the kinematic singularities of various robots used in industry. We first show how to combine mathematical reasoning with easy symbolic computations to study the kinematic singularities of an infinite family (depending on paramaters) modelled by the UR-series produced by the company ``Universal Robots''. Next, we compute roadmaps (which are curves used to answer connectivity queries) for this family of robots. We design an algorithm for ``solving'' positive dimensional polynomial system depending on parameters. The meaning of solving here means partitioning the parameter's space into semi-algebraic components over which the number of connected components of the semi-algebraic set defined by the input system is invariant. Practical experiments confirm our computer-aided proof and show that such an algorithm can already be used to analyze the kinematic singularities of the UR-series family. The number of connected components of the complementary of the kinematic singularities of generic robots in this family is $8$