196,109 research outputs found
A numerical design platform for induction motor efficiency enhancement under cost and performance optimization constraints
No full textTherapeutic protocol for Parkinson’s patient with freezing based on action observation plus sonification : preliminary results
No full textObjective: To evaluate the effects of a novel experimental protocol to treat patients with Parkinson’s disease (PwP) and freezing of gait (FoG), using functional, and clinical scales, and gait analysis.
Background: FoG is a disabling symptom strictly associated to falls. The little or no pharmacological responsiveness of FoG has led to an increasing interest in rehabilitation interventions aimed at functional recovery and autonomy. Currently, standard protocols employed for rehabilitation are based on the use of external sensory cues. However, cued strategies generate an important dependence on the environment. Teaching motor strategies without cues (i.e.action observation) can be an alternative/innovative approach to rehabilitation that matters most on appropriate allocation of attention and lightening cognitive load.
Methods: We compared the effects of two different therapeutic pro- tocols on three gait movements: walk, step initiation, and sit-to-step. The experimental protocol was based on action observation plus sonifi- cation; patients re-learned 8 motor gestures watching video-clips showing an actor performing the same gestures, and then tried to repeat the gesture. Each video-clip was composed by images and sounds of the gestures. The sounds of gestures were obtained with the sonification technique, by transforming kinematic data (velocity) recorded during the execution of gesture, into pitch variations (for an example see: bit.ly/ sonif_example). The same 8 motor gestures were re-learned in the stand- ard protocol, with a common sensory stimulation method. We evaluated patients with functional and clinical scales before, immediately after, at 1 month, and 3 months after the treatment. We also compared gait indi- ces with those of a normative sample of PwP and FoG (Mezzarobba et al. 2015). Preliminary data are based on two patients.
Results: Overall, data showed that both protocols have positive effects on functional and clinical tests. Larger performance improve- ments were seen with the experimental protocol. In the after treatment evaluations, the number of indices that differed from those of the norma- tive sample, were larger in the experimental protocol than the baseline protocol.
Conclusions: These preliminary data suggest that a multisensory approach could help PwP with FoG to re-learn gait movements, to reduce freezing episodes, and that these effects could be prolonged over time
A simple approach to air-gap armature reaction field computation in fractional-slot SPM multiphase machines for different air-gap topologies
No full textStudy of innovative electric machines for high efficiency vehicular traction applications
No full textThis thesis collects some of the work accomplished during the PhD research activity focused on the study of special electric machines for vehicle traction applications. The work is divided into due parts. The rst part is mainly technological and covers some studies and experimental activities concerning new technical solutions to solve some common issues in operation of electric motors for automotive use, namely ux weakening and cogging torque. The second part has a more theoretical nature and focuses on some methods for electric machine modeling and analysis which has been developed to facilitate the study and design optimizations carried out during the PhD research work.
The chapters in the rst part address the following topics:
1. Development and testing of an interior-permanent-magnet motor prototype fully conceived, designed and manufactured at the University of Trieste to implement a new concept of flux weakening system at high speeds. The concept has been also protected through a pending patent.
2. Multi-objective design optimization of an interior permanent magnet reluctance-assisted synchronous motor for the automotive industry.
The design optimization was meant to support an industrial development project which is still in progress so no prototype has been built yet.
3. Study of a new optimized magnetic wedge design capable of reducing cogging torque in automotive propulsion motors having open stator slots.
The second part proposes some analytical and numerical results that have been worked out to approach the modeling and optimization of various kinds of permanent magnet synchronous motors. The main problem to which these chapters try to answer is to nd suciently fast but accurate methods for permanent magnet analysis without time-consuming finite-element transient analysis. The proposed methods have been successfully integrated into design optimization programs used in the industrial environment in the development of innovative electric machines not only for the automotive industry
Optimal Selection of Rotor Bar Number in Multiphase Cage Induction Motors
No full textRules 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
No full textFractional-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
Postural control deficit during Sit-To-Walk in patients with Parkinson’s Disease and Freezing of Gait
No full textIntroduction
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 + FoG), 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 + FoG patients are spread over medial-lateral space more than in the PD-FoG (p < .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 < .01) with a delayed weight forward progression (p < .05). In GI task and walk task, COM and COP differences are less evident and even absent between PD patients.
Conclusion
PD + FoG 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
Optimal Rotor Bars Number in Four Pole Cage Induction Motor with 36 Stator Slots - Part I: Numerical Modeling
No full textThe identification of the optimal number of rotor bars in grid-fed, four-poles, three-phase cage induction motor is addressed in this two-part work for the frequent case of 36 stator slots. The optimization criterion being adopted is the minimization of the electromagnetic torque pulsations in full-load steady-state conditions. In Part I of the work results from the parameterized winding function (PWF) model are presented and successfully validated against time-stepping finite element simulations. In Part II the electromagnetic torque pulsations obtained from the PWF model are evaluated for different numbers of rotor bars. During this process motor rated power, stator winding design and main machine geometry are maintained invariant. The evaluation is applied to both possible practical cases of unskewed rotor bars and rotor bars that are skewed by one stator slot pitch
A motor design with self-adjusting flux capability for wide-speed-range auto motive applications
No full textOne of the most common issues in permanent magnet motors for automotive applications is to improve their capability of operating over very wide speed ranges. For this purposes, various motor design techniques have been proposed in the literature. After a brief review of these techniques, the paper presents an idea for improving the flux weakening capability of permanent-magnet reluctance-assisted motors. The idea is based on using an auxiliary field circuit embedded in flux barriers and used to partly demagnetize the motor above the base speed. The field circuit is fed by a brushless permanent-magnet exciter and a diode rectifier. While at low speed the field is not energized, it automatically activates above the base speed by means of a centrifugal switch. As discussed in the paper, the auxiliary field current increases linearly with the speed so as to progressively reduce motor flux with a consequent beneficial reduction in the current to be fed by the inverter for flux regulation
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