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Contribution: This article compares the effectiveness for online software engineering education of video-based learning and game-based learning using teacher-authored educational video games created by using authoring tools. Background: Although substantial research has evaluated the impact of video-based and game-based learning versus traditional teaching approaches, little research has been done comparing the effectiveness of video-based learning and video game-based learning. Furthermore, the few studies that performed this comparison did not compare the effectiveness for online education or examined teacher-authored video games. Research Questions: Is game-based learning using teacher-authored video games more effective than video-based learning in terms of knowledge acquisition for software engineering students in online settings? Is game-based learning using teacher-authored video games more effective than video-based learning in terms of motivation for software engineering students in online settings? Methodology: A quasi-experimental design with control and experimental groups and pre- and post-tests was employed. A total of 180 software engineering students participated in this study, 81 of which belonged to the control group while the other 99 were part of the experimental group. The students in the control group took an online lesson in which they learned exclusively by watching videos, whereas the students in the experimental group took the same lesson but learned exclusively by playing an educational video game created by a teacher through an authoring tool. Findings: The results show that game-based learning using teacher-authored educational video games was more effective than video-based learning in terms of both knowledge acquisition and motivation. [ABSTRACT FROM AUTHOR]

Online detection of rotor and load faults in permanent magnet synchronous motors (PMSM) based on spectrum analysis of current or vibration is not capable of identifying the root cause of the fault, since all faults produce identical fault signatures. The sensitivity of fault detection also depends on the motor and controller design making fault detection unreliable. In addition, operation under variable frequency and load limits the effectiveness of spectrum analysis based methods. In this article, airgap flux monitoring is investigated as an alternative for providing reliable identification of rotor and load faults in PMSMs. Based on the analysis of airgap flux under partial and uniform demagnetization, dynamic eccentricity, and load unbalance, an airgap search coil voltage based method for detection and classification of the faults is proposed. The claims made in the article are verified through experimental testing on an IPMSM under emulated fault conditions along with a comparison to vibration and current spectra-based detection. It is shown that the proposed method provides reliable online identification of the faults for cases where conventional spectrum analysis based methods fail. [ABSTRACT FROM AUTHOR]

There has been active research in fault diagnosis of permanent magnet synchronous motors (PMSMs) with the recent increase in reliability-critical PMSM applications. Most of the research efforts are focused on the motor current signature analysis (MCSA), as it allows remote online detection of the rotor and load defects using the current measurement available in the drive. A critical limitation of MCSA or vibration analysis is their inability to distinguish the type of rotor or load defect. It is crucial for the maintenance engineer to identify the type of defect since the course of action for continued operation differs depending on the fault. In this letter, a simple automated test method for identifying mass unbalance using vibration measurement commonly available in motor drive systems is proposed. The effectiveness of the proposed method is verified on a PMSM under emulated PM demagnetization, dynamic eccentricity, and mass unbalance conditions. [ABSTRACT FROM AUTHOR]

In this article, we investigate the potential of using single-pass InSAR model-based approaches to retrieve dry snow parameters. Two InSAR scattering models of dry snow are considered: the dense-medium random volume over ground (RVoG) model and the simple variant of the full penetration (FP) model. A quasi-crystalline approximation (QCA)-based extinction analysis confirms the negligible extinction dependence of the InSAR observables at L/C/X-band for fresh dry snow. The FP models the low-frequency (L/C/X-band) InSAR phase as a single constraint of snow depth and density, which can be supplemented by an extra observation (e.g., InSAR coherence or in situ depth/density). The single-pass InSAR models and inversion approaches were validated using X-band InSAR data collected from a tower-based three-frequency (X/Ku-low/Ku-high) fully polarimetric TomoSAR system, where a multi-frequency polarimetric InSAR analysis and ground-to-volume ratio-based snow condition analysis were conducted. We also analyzed the sensitivity and error propagation of the single-pass InSAR phase and coherence in measuring dry snow depth/density. It was found that the X-band HH-pol FP-modeled single-pass InSAR phase along with RVoG-modeled coherence or in situ depth is capable of measuring snow water equivalent (SWE) with a 23–26 mm uncertainty (13–15%) and a 20–26 mm bias (12–15%) for dry snow SWE of 0.2 m, and with an optimal perpendicular baseline on the order of a tenth of the snow depth (0.8 m) at our test site. This single-pass InSAR approach with the FP model is potentially useful and thus needs further investigation for large-scale dry snow retrieval with a wide range of snow conditions using ground-based/airborne/spaceborne low-frequency (L/C/X-band) InSAR observations. [ABSTRACT FROM AUTHOR]

Precise output torque control is often required in applications using synchronous reluctance machines. Direct measurement of torque has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of torque estimation methods has received significant research attention. Most of the exiting torque estimation methods require knowledge of machine parameters, suffering, therefore, from parameter sensitivity. Load and saturation are recognized as the primary source of parameter variation. This article proposes the use of a high-frequency signal injection for the online estimation of the machine parameters required for torque estimation. The improvement in the torque estimation will be especially relevant in deep-saturation regions. The method operates without interfering with the normal operation of the machine. [ABSTRACT FROM AUTHOR]

High-frequency (HF) signal injection-based has been widely investigated for sensorless position/speed control of permanent magnet synchronous machines (PMSMs). In PMSMs, the HF signal must be injected in the stator windings and an asymmetric (salient) rotor is required. The extension of HF injection-based sensorless methods with wound-rotor synchronous motors is studied in this article. The fact that rotor terminals are accessible opens interesting possibilities, as avoids the dependency on rotor asymmetries. [ABSTRACT FROM AUTHOR]

The rotor of self-bearing machines can be in an off-centered position as they lack of physical bearings. The air-gap length and effective area with respect to each phase become nonuniform, which results in inductance and back EMF non-linearities. Evaluation of self-bearing machines performance in time domain is inaccurate without a model that includes non-linear inductance and back EMF constants. To reflect non-linearities, finite element analysis (FEA) is often used. However, FEA requires large computational power to run in time-domain simulation. In this article, a 7-D lookup table (7-D LUT) model of inductance and back EMF constants, suspension forces, and torque is proposed for time-domain simulation, including non-linearity from the rotor translational and rotational displacement. Pre-evaluated FEA results are post-processed to construct the 7-D LUT model to enable fast and accurate time-domain simulation reflecting non-linearities from the input of rotary position (slotting effect), translational position in horizontal and vertical directions (unbalanced air-gap field effect), and magnetic saturation effect. A combined winding self-bearing machine is evaluated using the proposed method and verified with FEA and experimental results. [ABSTRACT FROM AUTHOR]

Contribution: This article provides evidence on the effectiveness of game-based learning (GBL) for computer science education when using educational video games created by teachers using authoring tools. Background: Although teacher-oriented authoring tools for creating educational video games can help overcome the main barriers hampering the use and uptake of GBL, there is a lack of studies examining the effectiveness of educational video games authored by teachers using these authoring tools by means of rigorous scientific methods. Research Questions: Is GBL using teacher-authored games more effective than traditional teaching in terms of motivation for computer science students? Is GBL using teacher-authored games more effective than traditional teaching in terms of knowledge acquisition for computer science students? Methodology: Two randomized control trials with pretest, post-test, and one questionnaire were conducted to compare the effectiveness of traditional teaching and GBL in two computer science courses. The sample of the two experiments was composed by 75 and 49 students, respectively. Half of the students attended a traditional lecture, while the other half learned solely by playing teacher-authored educational video games. Findings: The results show that GBL using teacher-authored games was practically as effective as traditional teaching in terms of knowledge acquisition, but that it was emphatically successful in increasing student motivation. Students who learned by playing educational video games found the experience more motivating and fun than their counterparts, and a vast majority of them preferred the GBL approach over traditional teaching. [ABSTRACT FROM AUTHOR]

Torque measurement/estimation in permanent magnet synchronous machines (PMSMs) is required in a large variety of applications. Direct torque measurement by means of torque transducers is typically limited to laboratory applications due to cost, reliability, and room concerns. Alternatively, torque can be estimated. Torque estimation methods require accurate knowledge of machine parameters. Injection of a high frequency (HF) signal in the stator via inverter has been shown to be a viable option for online machine parameters identification in PMSMs. However, this introduces concerns on the performance of the machine due to the noise, vibration, and additional losses produced by the HF signal. This article proposes a torque estimation method for PMSMs using low cost Hall-effect sensors. The method is based on the dependency of the leakage flux complex vector due to interaction between permanent magnet flux and stator coil flux and does not interfere with the drive operation of the machine. [ABSTRACT FROM AUTHOR]

There is concern within the cultural community about the decreasing number of people, especially young people, visiting museums and cultural institutions. To fight this trend, new ways of accessing art are needed. We believe that technologies like virtual reality can greatly foster the relationship between users and works of art. In this article, we present an elaborated virtual reality experience, ImmersArt, whose aim is to take users literally inside a work of art and the creative universe of its creator. The motivational impact of this tool was empirically analyzed and compared with other formats for experiencing art such as illustrated books and audiovisual presentations. The study suggests that young people are more motivated to study artwork when using virtual reality. [ABSTRACT FROM AUTHOR]

Torque pulsations are one of the major concerns in permanent magnet synchronous machines (PMSMs). Torque pulsations can be mitigated by proper machine design and/or by control. Independently of the means being used, precise measurement of torque pulsation is highly desirable for the validation and improvement of machine designs and control strategies. This article proposes a non-invasive, wireless vibration measurement system aimed to provide precise estimates of torque pulsations. The system is mounted on the rotor shaft of the PMSM, i.e., there is no mechanical coupling, and allows on-line measurement without interfering with the normal operation of the machine. [ABSTRACT FROM AUTHOR]

Control of permanent magnet synchronous machines (PMSMs) requires absolute rotor position measurement/estimation, as well as the magnet polarity detection for the machine start-up, encoders/resolvers being normally used for this purpose. However, these sensors can account for a large portion of the overall drive cost, and require additional room and cabling, therefore penalizing the size and reliability of the drive. This article proposes a method to emulate a resolver in machines using low cost Hall-effect sensors. The proposed Hall-effect resolver system is a new type of angular position sensor for PMSMs. This allows to control machines which do not include a resolver from inverters which require a resolver signal to operate. [ABSTRACT FROM AUTHOR]

Battery management systems (BMSs) are key components in battery storage systems in order to guarantee their safe operation and improve their performance, reliability, and efficiency. BMSs monitor critical parameters in the battery as state of charge (SOC), state of health (SOH), or temperature. Direct measure of SOC or SOH is not possible, while temperature, on the other hand, can be measured with different types of sensors. These sensors, although cost-effective, raise concerns regarding cabling, signal conditioning and acquisition systems, increasing cost, complexity, and decreasing reliability. The internal resistor of the battery has already been successfully used to estimate these parameters. BMS can also include the function of balancing (equalizing) cells of a battery pack. Among all available equalizing systems, those based on switched capacitors are interesting due to their simplicity and easy scalability. This article proposes an internal resistance (IR) estimation method for LiFePO4 batteries using signals naturally produced by a switched-capacitor equalizer (SCE). The IR will be used to estimate the battery temperature. It will be shown that the method can operate online and without interfering with the regular operation of the SCE. [ABSTRACT FROM AUTHOR]

Thermal monitoring is of high relevance for safe operation and degradation management of batteries. Direct measurement of battery temperature has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of temperature estimation methods has received significant research attention. Most of the existing estimation methods are based on the injection of an additional signal, which can produce additional losses. This article proposes a temperature estimation method for LiFePO4 batteries using the switching harmonics of the converter feeding the battery. Temperature changes are estimated from the variation of the battery impedance at the switching frequency. The method operates online and without interfering with the normal operation of battery and power converter, and does not therefore introduce additional losses or any other adverse effect in the batteries. [ABSTRACT FROM AUTHOR]

Permanent magnet synchronous machines (PMSMs) operation above base speed is typically achieved by injecting negative d-axis current to produce flux weakening. However, this mode of operation increases copper, stator/rotor core, and permanent magnet (PM) losses, penalizing the efficiency and increasing the risk of demagnetization. Variable flux PMSMs in which PMs are magnetized/demagnetized during normal operation of the machine have been proposed to avoid the use of flux weakening current. However, PM aging due to magnetization/demagnetization cycles has not been thoroughly studied yet. This article analyzes the variation of NdFeB, SmCo, and AlNiCo PMs properties, including magnetic, electric, and thermal, resulting from magnetization/demagnetization cycles. [ABSTRACT FROM AUTHOR]

Torque measurement/estimation in surface permanent magnet synchronous machines (SPMSMs) is needed in many applications. Torque measurement systems are expensive, require extra room, add weight, can introduce resonances into the system, and their performance can be compromised due to electromagnetic interference. Alternatively, torque can be estimated, accurate knowledge of machine parameters being critical in this case. Injection of a high-frequency (HF) signal in the stator via an inverter has been shown to be a viable option for online identification of machine parameters identification required by torque estimation methods for interior PMSMs. However, the reported methods require the use of two pulsating HF currents, which introduces concerns both on the adverse effects on machine's performance (additional noise, vibration, losses, etc.) as well as to the additional computational burden, as HF current controllers are required. This article proposes a torque estimation method for SPMSMs using a single HF signal; furthermore, a HF voltage signal can be used, avoiding the use of HF current controllers, and therefore simplifying the implementation. [ABSTRACT FROM AUTHOR]

Thermal and magnetization state monitoring of permanent magnet synchronous machines (PMSMs) is important for reliability purposes. Use of magnet high-frequency (HF) resistance has been proposed both for thermal and magnetization state monitoring, as it directly depends on PM temperature and magnetization state. Machine d-axis HF inductance has been recently proposed for thermal state monitoring, though its use for magnetization state estimation remains to be explored yet. This article reviews the use of HF-signal-injection-based methods for thermal and magnetization state monitoring on PMSMs, including the use of the HF inductance for magnetization state monitoring. [ABSTRACT FROM AUTHOR]

Small grid-tied wind turbines based on permanent magnet generators often use a cost-effective power converter topology consisting of a passive rectifier, a boost converter, and an H-bridge inverter. Speed or position sensors are rarely used due to cost issues. Model-based estimators relying on electrical magnitudes are used instead. However, such estimators are parameter sensitive, which limit their accuracy. Further concerns arise if these parameters change with the operating condition of the machine, mainly due to temperature. Speed sensorless control using the rectifier voltage ripple is analyzed in this paper. This technique provides good dynamic response and does not depend on machine parameters. Simulations are provided for speed and power tracking comparison with an accurate model-based speed estimation method operating at non-rated parameters. They show the speed accuracy and power tracking capability of the proposed method are similar to that provided by a speed sensor. This is translated into a 0.9% power increase when the model-based speed estimator shows 9% of error. Experimental results are carried out to test the effect of current and temperature in the estimation, showing temperature insensitivity and some distortion due to fast current transients. A speed estimation accuracy of zero mean error and 1.7% standard error is experimentally obtained in the regular operation of the wind turbine. [ABSTRACT FROM AUTHOR]

Torque estimation in permanent-magnet synchronous machines is highly desirable in many applications. Torque produced by a permanent-magnet synchronous machine depends on the permanent-magnets’ flux and dq-axes inductances. Consequently, precise knowledge of these parameters is required for proper torque estimation. This article proposes the use of a high-frequency signal for both PM flux and dq-axes inductances estimation. The high-frequency signals will be injected in the stator via an inverter superposed on top of the fundamental excitation. The proposed method can be used without interfering with the normal operation of the machine, the results being highly insensitive from machine's working condition. [ABSTRACT FROM AUTHOR]