In order to improve control performance in various control fields, it is important to model the controlled object accurately. In this case, the quality of the model is considerably influenced by the structure of the model determined by the engineer. An element description method is a method that can optimize not only parameters but also the structure of the model. Therefore, it is possible to search over a wide range without being restricted by human design. However, this considerably increases the search space, and it is easy to fall into a local solution. In this study, the artificial bee colony algorithm is combined with the element description method to improve its search ability. The artificial bee colony algorithm is known to be effective for high-dimensional and multimodal problems. The performance of the proposed method is validated using a heat sealing system in packaging machinery. The proposed method is evaluated in comparison with the genetic algorithm, which is a conventional method. Experiments confirm that the local solution avoidance performance of the artificial bee colony algorithm is significantly better than that of the genetic algorithm.

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.

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 torsion torque control (TTC) for a two-inertia system with environmental stiffness. The proposed TTC is robust to environmental stiffness as it compensates the measured load-side torque with the current reference through a single inertialization compensator (SIC). The SIC is independent of the TTC design, and a simple load-side plant model is constructed using the TTC and SIC. A load-side torque control based on a model error compensator (MEC) is adopted for one of the applications of the proposed TTC. In addition, plant nominal models are simplified using the proposed TTC. The proposed TTC system is effective even in the presence of environmental stiffness in simulations and experiments with geared motors for torsion torque and acceleration sensors.

The wheel slip speed feedback control method is a slip control method used in locomotives. The control method maintains a high operating motor torque, when the wheel slip speed feedback gain of torque reduction is high. However, a delay in the detection of the wheel velocity makes the system unstable. Persistent fluctuation of the slip velocity causes subpar acceleration performance and reduced tangential force. Accordingly, design method for a wheel slip speed feedback controller that maintains a high tangential force and prevents fluctuations in the slip velocity is presented in this study. Moreover, a method for designing a phase leed compensator to prevent fluctuations is also presented. These design methods are expected to enhance tangential coefficients.

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 200W prototype, the basic operation of the proposed system is confirmed in the input voltage range of 100V to 240V. 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.

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.

The rotor oscillation of a stepping motor occurs during rotor positioning. A novel tuning method can systematically determine the proper exciting times of back-phasing damping to suppress the oscillation without trial and error. The exciting times are automatically determined such that the transfer function zeros of the damping cancel the poles of the motor model. The motor drives sufficiently suppress the oscillation using the exciting times tuned for attached loads.

Application of large synchronous motors started in the early 90; currently the synchronous motors (SMs) are being phased out and replaced with getting old, and they are being replaced with larger capacity motors which are installed on the existing motor-mount basement. These larger capacity motors require higher magnetic flux than the conventional motors, which leads to the problem of magnetic saturation in the SMs. It is time consuming to find suitable parameters related to flux for each motor using the conventional SM control method. In this paper, a method to improve the adjustment of flux parameters using a simplified matrix table is introduced.

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.

We have been studying the application of amorphous metal with low loss to axial gap motors. However, because radial gap motors are used extensively, we are also considering a motor structure involving the application of amorphous metal to radial gap motors. In this study, we analyzed and evaluated an IPM motor to evaluate the improvement in efficiency caused by the use of amorphous metal for the entire stator cores. Creating an efficiency map of the prototype and comparing the efficiencies confirmed a significant improvement in efficiency in the low torque and high frequency bands.