A plant needs to be modeled with two inertia systems: to consider the spring element of the transmission due to the improved kinematic performance of a humanoid robot and to introduce a resonance suppression control. However, previous resonance suppression controls are not robust against modeling error and are difficult to apply to a humanoid robot. In this paper, we present a robust resonance suppression control for the modeling error of two inertia systems; we developed a self resonance cancellation control (SRC) and self resonance cancellation disturbance observer (SRCDOB) and applied them to a humanoid robot.
Conventional multi-degree-of-freedom drive systems need many single-degree-of-freedom actuators, but this makes the structure larger and heavier. The development of a spherical actuator should reduce the number of actuators, but the low torque and narrow rotation range are still problems. We developed a 2-degree-of-freedom spherical actuator with an outer rotor that can produce a higher torque and wider rotation angle. In this paper, we propose a control method; we confirmed its usefulness by performing dynamic analysis using the three-dimensional finite element method and by taking measurements with a prototype.
This paper proposes a low-inductance mounting technique for an inverter with large semiconductor packages. The following two measures are adopted to decrease the circuit inductance. One is the use of the low-inductance ground pattern of a printed wiring board. The ground pattern is connected in parallel to the main bus bar with lower resistance and higher inductance. The surge current with high di/dt flows selectively in the lower-inductance ground pattern, and the continuous normal current flows in the lower-resistance main bus bar. The other measure is the utilization of an eddy current induced in the heat sink. The eddy current, decreasing circuit inductance, increases in inverse proportion to the distance between the heat sink and a conductor connecting two semiconductor packages. Because of these measures, the circuit inductance decreases to 38% of that of a conventional circuit.
Practical evaluations of an efficiency-improved zero voltage soft-switching (ZVS) high-frequency resonant (HF-R) inverter for induction heating (IH) applications are presented in this paper. By adopting a dual-mode power regulation method that consists of the phase angle difference (θ) control and another effective control strategy such as pulse density modulation (PDM), pulse frequency modulation (PFM), and asymmetrical pulse width modulation (A-PWM), the IH load power can be widely regulated under the condition of ZVS while maintaining high efficiency even in a low-output power setting. The actual performances of the output power regulations and ZVS operations are obtained from an experiment based on the 1kW-60kHz laboratory prototype, after which the validity of each sub-mode power control scheme is evaluated from a practical point of view.
This paper discusses the voltage error caused by the dead time in voltage-source PWM converters. The theoretical analysis in this paper derives the nonlinear voltage error paying attention to the parasitic output capacitance in each switching device. The analytical result reveals that the turn-off current or the switching current ripple strongly affects the voltage error. In addition, it is also clarified that the conventional compensation methods based on linear and three-level approximations are suitable for small and large current ripple conditions, respectively. A simple calculation method of current ripples is also developed to estimate the turn-off currents in three-phase PWM converters. A compensation method based on the analysis is developed and compared with three different conventional methods in experiments using a 200-V, 5-kW three-phase grid-connection converter. The analysis-based method exhibits a good compensation performance, having a lower voltage THD than the conventional methods over a wide operating range.
The vertical axis wind turbine generator is mainly used for small size wind turbine applications, and is independent of wind direction. Its rotating part (shaft unit) should be rotated by an extremely small torque so as to increase the generation efficiency. However, commercially available bearings are not necessarily suitable for the shaft unit because their static and dynamic load ratings are frequently larger than those required for the vertical axis wind turbine. As a result, the frictional force and the rotating torque of commercially available bearings are too large for the shaft unit to rotate lightly. In this study, through an experiment with an actual vertical axis wind turbine, the bearings used for the shaft unit are reviewed in accordance with IEC61400-2. The design of the shaft unit with the bearings having the most suitable load rating and frictional force for the vertical axis wind turbine is attempted. The newly designed shaft unit will be applied to the vertical axis wind turbine and will be tested.
This paper first proposes an axial-type magnetic-geared motor that uses permanent magnets for only the high-speed rotor. The operational principle is described and the torque-speed characteristics were computed by using 3-D finite element method analysis. In order to increase the torque density, a novel axial-type magnetic-geared motor with permanent magnets on the high-speed rotor and stator is also proposed. The torque-speed characteristics were compared to the original model with permanent magnets only on the high-speed rotor. Finally, the computed torque-speed characteristics were verified by measurements taken on a prototype.
We designed a miniaturized permanent magnet synchronous motor with a magnetic gear by using an optimal design technique based on thermo magnetic field coupling analysis. To construct an even smaller motor, investigating the heat dissipation from the motor and increasing its rotating speed are necessary. We manufactured and tested the designed motor with a magnetic gear. The measured torque and motor efficiency demonstrated the high accuracy of the proposed design.
In order to improve the reliability of a power converter circuit, it is important to analyze the DC-side stray inductance between the DC capacitor and the power devices because this may affect the switching losses, lead to the occurrence of over-voltages in power devices, and increase the short-circuit current. As such, a number of studies have investigated these effects through calculations, experiments, and circuit simulations. However, thus far, no paper has discussed a design of the stray inductance. In this paper, the authors propose a design procedure for the stray inductance of the laminated bus bar for a high-speed switching circuit using SiC power devices. The relationship among the bus bar inductance, the over-voltage, and the short-circuit current is clarified using an analytical MOSFET model. In order to verify the analysis results, an experiment using SiC-MOSFET and SiC-SBD rated at 1,200V is conducted. From these results, the upper and lower limitations of the bus bar inductance for the buck chopper circuit are found, and the design procedure for the wiring structure considering the stray inductance is discussed using the inductance map.
A novel multi-resonant zero-voltage switching high-frequency inverter is developed; this inverter is capable of supplying a current of large amplitude to a load through suppression of the main switch current. The principle of the current ratio of the main switch current to the load current is theoretically proved using the capacitance ratio. The high-frequency operation with zero voltage switching is verified experimentally.
In recent years, to reduce switching loss, the switching speed has been dramatically increased. The increase in EMI y the high time gradient may cause improper operation of neighbor devices. For the above reason, it is necessary to reduce the EMI by using noise filter. In order to estimate the EMI in the design phase before trial production, highly precise EMI analysis technology is required. Estimating the EMI for power electronics has been attempted by highly precise analytical modeling and modeling including parasitic components with electromagnetic-field analysis in recent years. In this study, Tri-phase 400Vrms inverter for system interconnections with SiC-JFET is analyzed. The frequency range is from 150kHz to 30MHz, as specified by CISPR11 Class A. The study results showed that the noise terminal voltage is analyzable with an error of ±10dB by highly precise modeling.
In commuter trains, a large portion of the energy consumption is caused by losses from traction motors. Therefore, highly efficient traction motors are very effective at saving energy. We developed an induction motor with a high efficiency of 95.5%. This paper presents the design and efficiency evaluation of the prototype machine.
The motion of ferrite particles controlled by two electromagnets (EMs) with activated sludge in a container can help in reducing excess sludge. We applied this system on the laboratory scale to a miniature waste water treatment plant to evaluate the reduction of excess sludge. One plant was run without any reduction treatment of the sludge. The treated sludge was returned to the aeration tank for biological decomposition. The results showed that no excess sludge was produced in the treatment plant. Thus, a zero-emission waste water treatment plant was achieved by our experiments.
In this paper, a multiple-output high-frequency soft switching inverter is presented for home and business-use of IH cooking appliances. The proposed inverter is composed of parallel-connected single-switched multiresonant inverter cells. A detailed analysis indicates that the proposed inverter can control multiple-output power independently through a phase-shifted PWM scheme. The experimental results suggest that the prototype may be applied to multiple-output induction heating appliances.