This paper proposes a low vibration stopping method by switching between the free-run and short-circuit braking modes of a compressor. Vibrations are generated by the bouncing of the rotor caused by load torque fluctuations. The proposed method suppresses the bouncing by stopping the motor during the suction process, thereby preventing the generation of a large torque. In order to stop the motor during the suction process, the proposed method switches from the free-run to short-circuit braking mode at the top dead center, which is the starting point of the suction process. Furthermore, the inrush current during the short-circuit braking mode is suppressed using a hysteresis current controller. The vibrations are evaluated under four pressure conditions using the conventional and proposed methods. The results show that, the proposed method achieves more than 50% reduction in the amplitudes of the vibrations at all four pressure conditions. Notably, the proposed method reduces the amplitude of the vibration by 71% under the high-pressure condition.
In this industry-oriented research and development project, we studied the introduction and implementation of autonomous mobile robots (AMRs) for transporting equipment and parts in manufacturing facilities of aircraft equipment. In the relationship between the operator and AMR, it is crucial to implement an autonomous driving mode as well as enable the operator to control the operation by directly interacting with the AMR, such as when moving in complex locations. In such cases, a manual control mode is useful and often required. This study proposes a method of AMR motion that enables the operator to physically interact with the robot without the use of a force sensor and perform a power assist function according to longitudinal velocity-based impedance control. The power assist scheme can also be applied to other AMRs, particularly those with commercial motor-in-wheel drive systems, in which the design parameters, current, and torque of the motors cannot be measured or monitored in real time. For the control scheme, we designed a dynamic observer based on a mathematical model of the robot to estimate the force exerted when the operator contacts the body of the robot. Additionally, we developed a complementary algorithm that enables the movement of the robot on inclined surfaces. Comprehensive experimental analysis of the AMR under different operating cases demonstrates the feasibility and efficacy of the proposed power-assist control scheme.
This article presents an experimental confirmation of a constant DC-capacitor voltage-control (CDCVC)-based strategy for an active power-line conditioner (APLC) in three-phase four-wire distribution feeders (TPFWDFs). A calculation block of the fundamental-active current in the feeder currents is added to the previously proposed CDCVC-based strategy for the APLC in a laboratory-scale experimental model. The experimental results demonstrate that the DC component of the output value of a proportional-integral (PI) controller in the CDCVC block is reduced by the injected fundamental-active current in the feeder currents, which is calculated by the added fundamental-active current calculation block. The PI controller in the CDCVC block of the APLC calculates the fundamental-active current in the feeder currents.
Path-core type resonant inductance adjustable (PRIA) transformer usage in high-frequency LLC resonant converters is proposed herein to reduce transformer losses. The proposed magnetic structure is a type of transformer with adjustable resonant inductance combined with a path core for LLC resonant converters. In the proposed transformer, the flux density of the magnetizing inductance can be reduced with a path core. Therefore, fewer core losses are generated when using the proposed transformer. Moreover, the flux of leakage inductance that can be set with the path core has been previously proven by researchers at the Nagoya University laboratory. Consequently, the coil losses, which are one of the largest components of transformer losses, can be reduced effectively by controlling the path of the leakage flux. The proposed PRIA transformer has been reported to improve the efficiency of LLC converters. In this study, a conventional transformer with a magnetic structure is compared with a PRIA transformer through experiments. The core losses were obtained through finite-element simulations, and the coil losses not generated by the magnetic structures were estimated via calculations. The advantage of reducing transformer losses in high-frequency LLC resonant converters with PRIA-structure transformers is presented in this work.
This paper proposes an LLC type AC/DC converter to achieve high efficiency for wide input voltage range. The proposed converter has four operating modes with different voltage gain characteristics depending on the ON/OFF state of the six switches. The proposed system achieves a wide range of voltage gain by switching between different operating modes. Consequently, the proposed system reduces the magnetizing current by designing a narrow voltage gain in each operating mode. Moreover, the proposed control method achieves power factor correction control of the input current and smooth transition between different operating modes. This paper analyzes the operation and voltage gain characteristics of the proposed converter. A design method to reduce the magnetizing current and the mode transition method is also explained. Based on the experimental results on a 200 W prototype, the basic operation of the proposed system is confirmed in the input voltage range of 100 V to 240 V. Furthermore, the total harmonic distortion (THD) of the input current up to the 40th order of the fundamental frequency is less than 5 % across the entire input voltage range. The efficiency of the proposed system is more than 92.5 % across the entire input voltage range.
The authors propose an input/output coupling passive electromagnetic interference filter (PEF) for motor drive systems. The input/output coupling PEF uses magnetic coupling and integrates the common-mode inductors connected to the input and output sides of an inverter into a single magnetic component. Hence, this study investigates the attenuation characteristics of the input/output coupling PEF on conducted emission in motor drive systems. The measured results show that the input/output coupling PEF increases the attenuation of conducted emission compared to conventional PEFs over a broad range of frequencies.