Switched reluctance (SR) motors are motors that utilize the reluctance torque originating in the magnetic saliency between the stator and the rotor, which are made up of an electromagnetic steel sheet and windings without a permanent magnet. Because of their robustness and simple structure, SR motors are suited for use as the in-wheel motor for traction motors of vehicles. In a flat space such as is present in in-wheel motors, the axial-gap structure has an advantage compared with the conventional radial-gap structure for the space factor of a motor. An axial-gap in-wheel SR motor was tested in a microbus, and the bus could be successfully driven. The test results regarding the motor performance were satisfactory. However, the motor emits a loud sound. The acoustic noise of the axial-gap SR motor is mainly caused by the axial electromagnetic force. This paper presents a method of reducing acoustic noise that is based on a model of the electromagnetic force on the axial-gap SR motor.
This paper describes an estimation method for the physical parameters of human arms. The parameters are used in the medical and kinematic analysis fields. Personal differences are important, but some of the conventional methods do not consider personal differences pertaining to inertia in viscoelasticity muscular strength measurements. The remaining conventional methods that consider personal differences require precise measurement devices. The proposed method realizes kinetics modeling and identification of the friction and inertia including the off-diagonal parameters of human arms by using wearable robots. First, wearable robots are multi-input devices. In addition, the actuators of wearable robots can be located near human joints and can input M-sequence torque. Therefore, wearable robots can input signals having a high signal-to-noise ratio and ensuring persistently exciting characteristics in each human joint. By employing multi-input characteristics, the proposed method can reduce patients' burden by shortening the amount of time for estimation. In addition, we verify the accuracy of the estimated parameters by comparing the responses of the actual machine with those obtained by simulation.
We have developed novel mathematical models of d-axis and q-axis magnetic fluxes ϕd and ϕq for permanent magnet synchronous motors (PMSMs). The models can be used to approximate magnetic characteristics using simple fractional equations with id and iq as variables. They include eight constants, and some of them represent the degree of magnetic saturation and cross-coupling. However, the magnetic characteristics are varied with the temperature rise in PMSMs, which are dependent on the load torque and motor speed. In this paper, the characteristics of the eight constants that vary with the motor temperature and the residual flux density Br are shown. Further, we propose to extend the mathematical models by considering the temperature and Br variation.
The conventional auxiliary power supply (APS) of a railway vehicle is directly connected to the catenary through the LC filter. Hence, the switching devices of the APS must have a high breakdown voltage to account for catenary voltage fluctuation. On the other hand, low-voltage switching devices have better characteristics that are desirable for low-loss and high-frequency operation. Therefore, a step-down converter is incorporated between the LC filter and inverter to adapt to catenary voltage fluctuations when using low-voltage switching devices. This paper proposes the series-parallel continuously regulated chopper as a novel step-down converter. First, the fundamental operation characteristics and output voltage control method of the proposed chopper are introduced. The simulation and experimental results for the fundamental characteristics are then described; the simulation and experimental values were almost the same as the theoretical values. The proposed chopper controls the output voltage at the expected value without dramatic fluctuation regardless of the input voltage fluctuation. In addition, a resonance damping control for a constant power load is proposed. The operational characteristics were considered under different potential distributions or load conditions.
This study investigates power flow control methods for next-generation DC power networks. It has been anticipated that numerous distributed generators and energy storage devices will be introduced in next-generation power systems. Therefore, arbitrary and flexible power flow control methods for such power systems are required. In this work, we study a power flow control method that combines node voltage control and additional voltage insertion control on links (link voltage control) for controlling next-generation DC power networks. The effectiveness of the proposed power flow control method is demonstrated by experimental results. It is shown that the proposed power flow control method can be expected to be one of the promising approaches for the realization of next-generation power systems.
We propose a linear oscillatory actuator that converts rotational motion into linear motion using brushed DC motors. In this study, we verify the operating principle and characteristics of this actuator through FEM analysis and dynamic simulation. Additionally, we verify the validity of the analysis results through experiments on a prototype.
The general solution for resonant inductive coupling circuits has not been obtained because the roots of the characteristic equation of the circuits are too complicated. In order to overcome the difficulty of solving the circuit equation, we have introduced a new method that is converting the second-order differential equation for the charges to the first-order differential equation for the vector whose elements are currents and charges, and incorporating the characteristic equation into the structure of the eigenvectors of the differential coefficient matrix. We thus obtained the general solution for the circuits. In addition, we derived formulas for power transmission and power reception. Results of numerical calculation in the time and frequency domains always satisfy the low of conservation of energy. We thus obtain a number of interesting results. For example, 1/4 cycle delay between power transmission and power reception is very interesting because it shows that the power transition from the primary coil to the secondary coil resembles the peristaltic motion of the magnetic field energy.
A method for designing the time response profile of the output of a discrete closed loop system caused by a sudden disturbance that takes the robustness of the system into consideration is proposed. The design is based on Youla parameterization. We express the parameter function Q by the finite series of z-1. As the sensitivity function has no pole other than z=0 when this controller is applied, we obtain finite time settling. We select the coefficients of z-i by taking the robustness into consideration. We applied the proposed finite time settling control to the HDD benchmark.
This paper proposes an FRT (fault ride through) control method for a multi-modular matrix converter operating under short voltage sag to prevent the unexpected acceleration of the generator. The proposed method uses an external braking circuit and feedback controls to obtain a generator torque same as that before the voltage sag. From experimental results, the proposed method maintains the generator torque to -1.07p.u. and injects a grid reactive current of 0.60p.u. during the voltage sag.
This paper proposes a MLPT (Minimum Power Loss Tracking) control method to minimize the power loss of a three-phase DAB (Dual-Active-Bridge) galvantically isolated bidirectional dc/dc converter by employing phase-shift control together with PWM control strategy. The effectiveness of the proposed MLPT method is verified via experiments.
The Signal Processing Research Group is focusing on signal processing, image processing, motion control and mechatronics. First topic is signal processing algorithms that are being implemented on Field Programmable Gate Array (FPGA) devices. For instance, estimations of motion control variables as motor position and velocity. Second topic is Mobile Augmented Reality (MAR) for industrial applications like training equipment.