Extensive research has been undertaken in recent years for the development of the next generation of power devices, such as silicon carbide (SiC) and gallium nitride (GaN) devices, and high-speed switching circuits have been implemented. In such cases, high-speed switching operations may generate electromagnetic noise and a surge voltage in the power electronics circuits. Stray inductance and capacitance in the circuits are critical parameters of the noise and surge voltage. Therefore, it is important to design and analyze the stray inductance and capacitance of the direct current (DC)-side circuit of an inverter.
This paper proposes a laminated bus bar design procedure in consideration of both the inductance and the capacitance of the bus bar. The effectiveness of the design procedure was tested using a buck converter circuit rated at 400V and 70A with an SiC MOSFET and SiC diode.
This paper proposes a new control system that facilitates two-degrees-of-freedom (2DOF) control to reduce the output voltage distortion in the self-sustained operation mode of a photovoltaic generation system. The proposed control system is configured by combining the disturbance observer using a notch filter (notch type disturbance observer) and a sinusoidal tracking controller. This configuration of the system facilitates high tracking performance and high disturbance suppression performance. This system is a new frequency-separation-type 2DOF control system that has the complete tracking performance of only the fundamental frequency, and has the desired recovery performance of the other harmonic frequency and the quick inserting load current. The numerical simulation results and experimental results confirm that the proposed control system reduces the output voltage distortion in an effective manner. Furthermore, the proposed control system is highly robust to the changes in the load.
Communication delay between a master and a slave robot destabilizes a bilateral control system. Recent researches showed that an adaptive controller that dynamically determines the master's controller gain according to the stiffness of the contact object is effective in improving stability. As the stability depends on the convergence speed of the estimated stiffness, this paper proposes an algorithm that quickly estimates the stiffness. A polynomial interpolation and a Schmitt trigger are utilized for the estimation. The validity of the algorithm is verified by simulations and experiments. The convergence speed of the position and the force is improved by the proposed algorithm.
We previously reported a 60Hz wireless power transmission (WPT) system, which is a system that uses the common utility frequency. In the study reported in paper, we solved several issues in order to install this system in a small electric vehicle. First, an accelerated finite difference time domain (FDTD) method using a graphics processing unit was developed to solve the issue of computation time. Next, theoretical equations for the transmission efficiency (η) and power (Pout) that include the stray load loss were derived from an equivalent circuit analysis. A new device was designed based on these theoretical equations, where by η =70% and Pout =451W were achieved for a transmission distance of 150mm. Finally, we attempted to wirelessly charge of a lead storage battery. The overall efficiency of the wireless charging system was maintained at 60% during battery charging.
This paper focuses on storage and reproduction systems of environmental haptic sensations. In the conventional reproduction system, the command values of the system are generated from the environmental haptic memories that correspond to the position of the actuator. Because the environmental information, which are stored in the memories depending on the position, become insufficient, the conventional method is difficult to treat the high-stiffness environment. To solve this problem, this paper newly proposes storage and reproduction systems of haptic sensations based on admittance control. The proposed system generates the position command corresponding to the force response of the actuator. Therefore, the proposed reproduction system is able to reproduce the haptic sensations of high-stiffness environments. The effectiveness of the proposed method is confirmed by the experiment.