Recently, mobile carts have been used in the field of production and welfare. Accordingly, the usability of mobile carts has become more important than ever before, and a human-friendly control technique for users is needed. In this paper, we propose a novel acceleration control for the mobile cart and illustrate that the weight felt by users follows rapidly and precisely the command reference of weight set in the controller. The proposed method makes it possible to control the wheel-side acceleration with a torque sensor built in the driving shaft. The torque sensor measures the output torque of the reduction gear. Moreover, two modes of application using the proposed method are shown. One is the power-assisted mode, and the other is the rehabilitation mode. To confirm the effectiveness of these modes, evaluation values of the usability are defined, and effectiveness is verified by simulations and experiments.
In order to minimize torque ripple in a switched reluctance motor (SRM), various control methods have been proposed. One such method is current profiling control based on a mathematical motor model concerned with the relationship between torque position and current, which can be derived from measured magnetizing curves. However, current profiling control faces issues with an increase in torque ripple at the current overlapping region depending on the load condition. In this study, through magnetic analysis using 2D-FEA and mathematical analysis based on a test SRM (four-phase, 400W, and 8/6 pole configuration), the reason why the torque ripple increases is revealed, and a modified torque-position-current model considering mutual coupling is proposed for better control of torque ripple minimization. Experimental studies on torque ripple minimization using the test motor show that the proposed current profiling control offers better torque ripple control performance.
Realistic systems have received increasing attention auditory sense plays a significant role, sound-field reproduction that generates high-presence sound-field is important. Key factor affecting the presence of sound-field is the influence of echo. Therefore, this study focuses on the effect of echo for a more realistic sound-field reproduction. In this study, the sound wave from a sound source is exposed to the echo effect through an acoustic impedance control performed by constructing a virtual wall. The virtual acoustic impedance is controlled by the sound wave generated from a secondary sound source the virtual wall acoustic impedance varies at a certain distance from the sound source. Therefore, an echo effect is produced through the control of the acoustic impedance the listener feel as if direct sound was reflected at the position of the virtual wall.
To manufacture wireless power transfer (WPT) products, not only in-depth knowledge of WPT but also various factors, such as power supply, charging circuit, and battery, must be considered, and the complexity is a barrier to the spread of WPT technology. Therefore, if the voltage is easily stepped up/down by the WPT circuit section, a general-purpose power supply and charging circuit can be used, leading to simplification of the system. The S/SP method proposed in this study exhibits the same input/output (I/O) characteristic of an ideal transformer, and the I/O ratio of the WPT circuit is determined from the turn ratio of the coils, similar to a general transformer. In a power feeding experiment, the I/O voltage ratio of the WPT circuit matched the turn ratio of the coils. The power transfer efficiency of the S/SP system was lower than that of the S/P system, but the difference was only 1.0%. Through a secondary side misalignment experiment, we confirmed that the I/O relation was maintained to an extent. In addition, the S/SP method was clarified to have better displacement characteristics than those of the S/P method.
A DC-AC conversion efficiency of over 99.7% is experimentally measured using a two battery high efficiency energy conversion system (HEECS) inverter. The accuracy of the efficiency measurement is evaluated by two methods: the direct measurement method and the loss breakdown method. After several measurements, calculations and analyses it is concluded that the measurement error based on the loss breakdown method is 0.04%.
To increase efficiency and reduce weight of low frequency traction transformers (LFTs), many studies have been dedicated to the study and design of power electronic transformers (PETs). Most of these studies have focussed on 16.7Hz traction systems and a few on 50/60Hz systems. PETs offer several degrees of freedom to the designer such as configuration and modulation of power stages, switching frequency, magnetic material etc., which are evaluated based on given specifications to meet the objectives of maximum power density and efficiency. This paper presents a detailed analysis of efficiency and power density of each power stage in a PET with respect to its design parameters. A design methodology is outlined to replace an LFT with an optimally designed PET. To elucidate the design process, the considered case is a 4.16MW transformer supplied by a 25KV, 60Hz catenary for a Shinkansen series-700. The configuration of the PET considered is of the indirect type with a cascaded H-bridge as the AC/DC stage interfacing the catenary and a set of parallelly connected DC/DC converters at the output. The best obtained efficiency is 97.7% with a weight of 1.69 tonnes which is significantly higher than that of the LFT.
In this paper, we propose a novel rotor structure of claw-pole motor (CPM) to reduce harmonic iron loss. In order to realize this low iron loss structure, a magnetomotive force-based a simulation method is presented to clarify the cause of harmonic iron loss. As the proposed method is based on mathematical theory, the rotor structure can be evaluated with a low computational cost. To validate its effectiveness, conventional and the proposed model are analyzed using the finite element method. The results indicate that the harmonic loss of the developed rotor is lower than that of the conventional rotor.
In the previously developed pure sinusoidal output single-phase current-source inverter (CSI), a conventional multilevel current-source inverter was successfully combined with a linear amplifier to realize a hybrid multilevel current-source inverter. Linear amplifier utilization was performed to reform a staircase multilevel current waveform into a pure sinusoidal current one by using a superimposition technique. To obtain very low harmonics by only using a small output filter capacitor, a class-A linear amplifier was utilized as the current compensator. However, this hybrid multilevel CSI must be applied in a high number of levels to achieve an acceptable power efficiency. Consequently, the system requires the use of many current modules that leads to a high semiconductor device count. Excessive semiconductor devices utilization, in turn, leads to performance deterioration due to switching and gate charge losses, and also decreases the power density of the system. Therefore, the recursive multilevel technique is proposed to handle the current module activation sequences, such that the high number of levels in the multilevel CSI can be constructed by only using a small number of current modules. The simulation and experimental results confirmed the applicability of the proposed technique with some advised discretions.
This paper proposes a circuit configuration of LLC converter a wide voltage range and high efficiency. The proposed LLC overcomes the narrow voltage gain range of conventional full-bridge (FB) LLC converters. Owing to the switching patterns of the primary side, two resonant tanks operate in half-bridge and FB modes. The two resonant tanks are designed with different parameters, and the proposed LLC has six operating modes. These modes enable a squeezed switching frequency span, which is close to the resonance frequency. The proposed control method achieves seamless transition between the operating modes and a wide voltage gain range. First, the operating principles and characteristics of the proposed converter are analyzed. The transitions between modes are determined based on the analyzed theory. In addition, the design guidelines for the two resonant tanks are describe. The parameters of the two resonant tanks are designed using the first harmonic approximation method, and each is determined to achieve a wide voltage range and high efficiency. A prototype rated to 1.0-kW is designed to convert the input of 360V to an output of 100-420V, and the proof of concept is validated. Experimental results confirm that the proposed circuit achieves a voltage gain of less than 0.5 to more than 2.0 under different load conditions. Furthermore, the proposed mode transition method achieves seamless transition between modes without complicated calculations. Experiments confirm a maximum efficiency of 96.5%.
This paper discusses a design method for a proposed integrated magnetic component for an isolated bidirectional three-port DC-DC converter (TPC). TPC comprises a dual active bridge converter (DAB) and a non-isolated bidirectional DC-DC converter (NBC); each converter is independently controlled with a transformer and a magnetically coupled inductor. To reduce the size of the magnetic components, an integrated magnetic component that can integrate a magnetically coupled inductor and a transformer is implemented. A 750-W magnetically integrated TPC prototype was constructed and tested to validate the operation. The experimental results show that the efficiency of the integrated TPC is above 90% for the entire output power range, which is nearly equal to that of the conventional magnetic component. As a result, the proposed component was 10% smaller than the conventional magnetic components, and the overall size of the integrated TPC was 33% smaller than that of the conventional one.
This paper presents a novel methodology of magnet temperature estimation using a magnet flux linkage observer for a Variable Leakage Flux Interior Permanent Magnet Synchronous Motor (VLF-IPMSM), whose parameters vary depending on load current conditions. The magnet temperature estimation algorithm consists of a Gopinath-Style flux observer, magnet flux linkage observer, and magnet temperature estimator based on the look-up table. The estimation accuracy is evaluated on d-q current plane by using both a behavior model of JMAG-RT and a control model of MATLAB Simulink. Then it is shown that the proposed methodology can be applied to a VLF-IPMSM for magnet temperature estimation.