This study aims to improve the backdrivability of a two-inertia system by developing a single-inertia system using an equivalent disturbance compensator. This method provides a torque equivalent to the disturbance torque and provides a motor-side acceleration equivalent to the load-side acceleration caused by disturbance. The proposed method also achieves smooth backdrivability by realizing the single inertialization of the load-side inertia alone. The efficiency of the proposed method is confirmed through a transfer function, two types of real machine experiments, and simulation results.

This study presents a novel circuit topology for a single-phase inverter using an active power decoupling circuit operated in discontinuous current mode (DCM). In a conventional single-phase grid-tied inverter, bulky capacitors are used in a DC-link to absorb a power ripple with twice the grid frequency. However, electrolytic capacitors limit a converter's lifetime. In contrast, ceramic capacitors are used in the proposed circuit since the required capacitance is reduced. Furthermore, the active power decoupling circuit in DCM has no inductor inside by utilizing the current zero cross featured in DCM for power ripple compensation modes. An experimental verification using a 1-kW prototype shows a 90.2% current ripple reduction caused by the power ripple with twice the grid frequency. The efficiency exceeds 94% in the 20% region of the rated power to 1-kW through 96.0% of the 650W maximum. According to a theoretical evaluation using a Pareto-front optimization assumed as a 3-kW system, the proposed circuit reaches the maximum power density at 20kHz which is 115% higher than that of the passive power decoupling method. The inductor volume in the proposed circuit is reduced by 30.4% compared to a conventional buck-type active power decoupling circuit.

Solar electric vehicles (EVs) can travel a long distance by generating electricity from panels mounted on them. The solar EV can generate a sufficient amount of electricity in fine weather. However, the amount of power generation decreases in cloudy weather. Therefore, to improve the cruising range of solar EVs, it is important to optimize a driving plan and to design a vehicle with good mechanical performance. By defining a evaluation function as time integration of the vehicle's energy balance, this study proposes an optimization theory that takes the variation of weather into account. Then, it proposes two types of solutions: the iterative calculation method and the sequential calculation method. The effectiveness of the theory is verified by simulating actual driving.

Vibration suppression control in vehicles is important for ride comfort. In vehicle electrification, the use of an in-wheel motor as an actuator for vibration suppression has attracted attention as an alternative to active suspension systems. However, a model-free conventional controller design method cannot sufficiently suppress vibration at the most significant frequencies (4Hz to 8Hz) because of mechanical resonance. In this study, we analyze the frequency response of an experimental vehicle. Using the identified frequency response of the vehicle, we design a pre-compensation filter based on the desired vibration suppression performance characteristics. The vibration suppression performance improved with the experimental vehicle at target frequencies from 4Hz to 8Hz.

It is more difficult for magnetic encoders to achieve a higher resolution than optical encoders. The resolution can be improved by multipolarizing the magnet, however the absolute angle cannot be calculated. Using the eccentric rotation of a 4-pole magnet, the authors simultaneously achieved high resolution and absolute angle calculation for a magnetic encoder. In this paper, we propose a high-resolution magnetic absolute encoder using an 8-pole magnet. The higher the eccentricity of the magnet, the easier it is to calculate the offset required to calculate the absolute angle. However, as the eccentricity increases, the angle error increases. The relationship between eccentricity and angle error is clarified, and an appropriate eccentricity is examined.

Sensing is essential in human cooperative robots to realize safe and powerful operations against contact with the surrounding environment. Contact sensing has been studied for manipulators to avoid accidents caused by collisions between humans and robots. Conventional research has demonstrated that contact sensing requires many sensors or has a limited measurable range. In the conventional research without sensors, modeling systems, such as frictional force and plant parameters, have been used to estimate the contact force. However, a high reduction ratio mechanism for achieving powerful operations hinders accurate force estimation. This study proposes a method to estimate the contact force and contact position on a manipulator with a high reduction ratio mechanism by installing only one force/torque sensor on the base frame of the manipulator. By using the proposed method, the contact force and contact position can be detected regardless of the location where the contact force is applied. Furthermore, when the contact force is applied in a location where the contact position cannot be accurately estimated, an estimated disturbance or a link motion is used to determine the contact position. The effectiveness of the proposed method is validated through experiments.

This presents a reactive power control strategy for the single delta bridge cell modular multilevel cascaded converter (SDBC-MMCC) for static synchronous compensator (STATCOM) under asymmetric voltage conditions. An average power balancing method is proposed to support continuous injection of reactive power under grid voltage fault conditions, considering sub-module capacitor voltage balancing and STATCOM maximum phase current protection. Analytical solutions of the STATCOM phase currents are presented. A maximum current limit control scheme is proposed to ensure continuous reactive power injection and STATCOM operation under unbalanced voltage condition. The fault-ride through capability of the SDBC STATCOM under asymmetrical condition is analyzed using the proposed method. A comparative analysis shows that the current requirement of the proposed strategy is superior to the zero-sequence current balancing technique.

This study analyzes and evaluates four transmission characteristics of the capacitive power transfer (CPT) with resonance coupling. A constant voltage source is used under all conditions. The target compensation topologies for the investigation are series-series (SS), series-parallel (SP), parallel-series (PS) and parallel-parallel (PP) topologies. The analysis results under the unified conditions describe the five transmission characteristics: (a) the equivalent maximum efficiency in four topologies, (b) the squared lower output power of the coupling coefficient of PS and PP topologies compared with those of SS and SP topologies, (c) the squared lower optimal loads of the coupling coefficient of SS and PS topologies compared with those of SP and PP topologies, (d) the constant unit power factor (CUPF) characteristics from the source in four topologies, (e) the constant current (CC) characteristics in SS and PP topologies, and the constant voltage (CV) characteristics in SP and PS topologies at the load variation around the optimal load. From these evaluations, both SS and SP topologies, which are superior in terms of the output power, are recommended when using the voltage source. Finally, the powering experiment in SS and SP topologies shows the effectiveness of these evaluations.

This paper proposes a control method to reduce the capacitance of an inverter driven motor system comprising two inverters and an open-end winding machine. In the proposed method, the inverter connected to the DC power supply switches based on the fundamental electric angular frequency of the motor. The other inverter is a pulse-width modulator controlled to generate a compensation voltage to supply a sinusoidal voltage waveform to the motor. Therefore, the carrier-frequency-order component of the input current harmonic can be reduced greatly, which helps reduce the current ripple of the filter capacitor across the DC-bus. Furthermore, this paper proposes a new control method to suppress the voltage fluctuation of the floating capacitor of the secondary-side inverter. The voltage fluctuation of the floating capacitor and hence its capacitance are reduced. The effectiveness of the proposed system is verified through experiments. The proposed control method suppresses the voltage fluctuations of the floating capacitor by 35.0% compared to the conventional driving method.

In this study, an LLC converter that can achieve a wide range of voltage gain and high efficiency for two loads is proposed. The efficiency of the proposed LLC converter is found to be greater than that of the conventional full-bridge LLC converter. Depending on the ON/OFF state of the five primary switches, the proposed converter offers five modes of operation. These modes enable a squeezed switching frequency span that is close to the resonance frequency. In all operation modes, one load is controlled by the switching frequency, while the other is controlled by the switching frequency and phase-shift angle. The proposed control method provides a wide operating range and seamless transition between different modes. Furthermore, the mode transitions are performed based on the relationship between the switching frequency and phase-shift angle. First, the theoretical characteristics of the proposed converter are analyzed. Next, the gain characteristics of each operation mode and the mode transition method are described. The prototype is designed to convert a constant input voltage of 360V to output voltages ranging from 80-420V and 36-48V. The experimental results confirmed that steady-state waveforms can be achieved in the multiple proposed modes of operation and voltage gains ranging from less than 0.5 to more than 1.0. Moreover, seamless mode transitions can be achieved without large deviations between the outputs. Finally, the efficiency of the proposed converter is evaluated in comparison to that of a conventional converter. The proposed converter achieved high-efficiency operations in the CC2 region of the battery compared to the conventional converter.

This paper proposes a 2.5MHz high-frequency output inverter based on a frequency multiplying technique with a multi-core transformer using Mn-Zn ferrite materials. The upper limit of the operation frequency for these materials is lower than the output frequency of 2.5MHz. First, the operation principle of the proposed circuit is explained. Second, a difficulty of using Mn-Zn for transformers at the frequency of 2.5MHz is discussed. Third, a numerical analysis shows that the proposed circuit can output the frequency over the upper limit of the operation frequency of Mn-Zn ferrite. Finally, through continuous operation, where the proposed circuit outputs approximately 650W, it is experimentally confirmed that Mn-Zn ferrite can be used without large iron loss at the output frequency of 2.5MHz. Thus, the proposed circuit can overcome the difficulty of using Mn-Zn for transformers at the frequency of 2.5MHz.

This paper proposes a bi-directional isolated DC/DC converter for the battery charger and discharger of Electric Vehicle to reduce the power loss under light loads. The proposed DC/DC converter consists of two full-bridge inverters, an isolated transformer, and a boost reactor, and provides bi-directional transmission, buck-boost conversion, zero-voltage-switching and reactive power suppression. Two power semiconductors of the inverter in the rectification side are turned off to block a reactive current, which increases the power loss under light loads. The phase shift amount in the two full bridge inverters are controlled continuously and simultaneously seamless power transmission. The 400V-3.5kW experimental system exhibits stable bi-directional buck-boost conversion and seamless transition between the charging and discharging modes, while suppressing the reactive power. Moreover, the proposed DC/DC converter reduces power loss by 67.5W under light loads (240W), compared with the conventional control.

This paper describes an operating method for a PWM rectifier suitable for air-cooled heat pump chillers. The efficiency of chillers have to be improved in the light to middle load ranges, and the harmonic suppression should be reduced in heavy load ranges. To satisfy this requirement, sinusoidal modulation is adopted in the PWM rectifier by applying over-modulation and two-step boost voltage control. Although over-modulation can reduce switching loss, current distortion remains. In this study, the input current distortion characteristic is derived in the over-modulation, and it is clearly shown that the distortion has a local minimum around a voltage boost ratio of 1.0. Using this characteristic, the efficiency is improved by the operating voltage boost ratio of 1.0 from light to mid-range load. At heavy loads, harmonic restraint and compressor motor high-speed rotation are made compatible by boosting the DC bus voltage to the second level. It is confirmed that ac to dc power conversion efficiency is equivalent at the voltage boost ratio of 1.0, and the input current harmonic is reduced by 40% at the boost ratio of 1.14, compared with the test results of 120^° discontinuous pulse width modulation.

This paper describes a high-frequency-isolation circuit that uses a three-phase transformer with a zero-phase current. The proposed circuit contains a bidirectional chopper circuit and a three-phase high-frequency isolation circuit. The bidirectional chopper circuit controls the DC bus voltage of the first circuit independent from the input voltage source. Thus, the ratio of the DC bus voltage of the first circuit to that of the second circuit can be controlled, which is important in controlling the high-frequency isolation circuit. This study theoretically analyzes the proposed circuit and obtains typical circuit waveforms by simulation. In addition, experimental results using the proposed circuit are discussed. The efficiency of the proposed circuit is measured and compared for each DC bus voltage value. As a result, the proposed circuit can be effectively used for demand control such as in energy storage systems including battery PCS because of its high efficiency using a full-ranged soft-switching technique by controlling the DC bus voltage.