Yoichi Hori

Robust speed control of DC servomotors using modern two degrees-of-freedom controller design

The authors propose a robust speed control system for DC servomotors based on the parametrization of two-degree-of-freedom controllers. The servosystems can dramatically improve the characteristics of the closed loop systems, i.e. the disturbance torque suppression performance and the robustness to system parameter variations, without changing the command input response. The excellent control performances obtained during laboratory experiments by using a microprocessor-based controller are shown. >

Speed sensorless field orientation control of the induction machine

A speed estimation method is proposed for an induction machine and its application to the flux observer based field orientation (FOFO) control system is discussed. The motor speed is estimated based on the difference between two flux estimators. Its convergence performance is estimated and the authors propose an assignment method. The speed estimator is applied to the FOFO controller. Experiments show that the speed sensorless FOFO operates with enough stability and has a robustness to rotor resistance variation.<<ETX>>

Maximizing Air Gap and Efficiency of Magnetic Resonant Coupling for Wireless Power Transfer Using Equivalent Circuit and Neumann Formula

The progress in the field of wireless power transfer in the last few years is remarkable. With recent research, transferring power across large air gaps has been achieved. Both small and large electric equipment have been proposed, e.g., wireless power transfer for small equipment (mobile phones and laptops) and for large equipment (electric vehicles). Furthermore, replacing every cord with wireless power transfer is proposed. The coupled mode theory was proposed in 2006 and proven in 2007. Magnetic and electric resonant couplings allow power to traverse large air gaps with high efficiency. This technology is closely related to electromagnetic induction and has been applied to antennas and resonators used for filters in communication technology. We have studied these phenomena and technologies using equivalent circuits, which is a more familiar format for electrical engineers than the coupled mode theory. In this paper, we analyzed the relationship between maximum efficiency air gap using equivalent circuits and the Neumann formula and proposed equations for the conditions required to achieve maximum efficiency for a given air gap. The results of these equations match well with the results of electromagnetic field analysis and experiments.

Motion control in an electric vehicle with four independently driven in-wheel motors

We study methods of motion control for an electric vehicle (EV) with four independently driven in-wheel motors. First, we propose and simulate a novel robust dynamic yaw-moment control (DYC). DYC is a vehicle attitude control method that generates yaw from torque differences between the right and left wheels. The results of simulations, however, identify a problem with instability on slippery, low /spl mu/ roads. To solve this problem, a new skid detection method is proposed that will be a part of traction control system (TCS) for each drive wheel. The experimental results show that this method can detect a skidding wheel, without any information on chassis velocity. Therefore, this method will be of great help during cornering or braking in a TCS. These methods will be integrated and tested in our new experimental EV.

Basic experimental study on helical antennas of wireless power transfer for Electric Vehicles by using magnetic resonant couplings

Wireless power transfer is required for the diffusion of Electric Vehicles (EVs) because it makes possible the process of automatically charging EVs. The technology of wireless power transfer requires three main elements: large air gaps, high efficiency and a large amount of power. Though, there has been no such technology, recently, the technology of electromagnetic resonant couplings was proposed and named WiTricity. With this technology there are large air gaps, high efficiency and large amounts of power. In this paper, the feasibility of wireless power transfer for EVs by electromagnetic resonance coupling is studied. We studied small sized antennas that can be equipped on the bottom of a vehicle and we studied the electrical characteristics of the antenna with equivalent circuits, electromagnetic analysis and experimentation. The length of the air gaps between a transmitting antenna and a receiving antenna affect resonance frequencies. The resonance frequency changes from two to one depending on the length of the air gap. Until a certain distance, maximum efficiencies are not changed. Large air gaps are weak couplings. In a weak coupling at resonance, magnetic resonance couplings can transfer energy with high efficiency. The specification results at high power are proposed. In this paper, the feasibility of wireless power transfer with large air gaps and high efficiency by small sized antennas that can be equipped on the bottom of EVs is proposed.

Estimation, identification, and sensorless control in motion control system

The paper presents the state of the art of motion systems particularly emphasizing both estimation and identification of parameters and control variables of an electric-motor-driven motion system. In a modern electrical drive system, it is required to take not only the electrical aspect but also the mechanical phase into total system consideration. Improvement in electrical aspect needs a variety of information pertaining to electrical machines and power electronic circuits for improving AC variable-speed drives. Important techniques of identification or estimation of parameters and control variables in AC drives are explained. Such information includes machine parameters, flux, speed, position, and so on. Also, the paper shows that there is some theoretical limit of performance. For improvement of the mechanical phase, the disturbance torque is the most important variable to be identified. It is used in motion control systems, for example, in the feedback loop. Various applications are possible by modification of such a basic approach. As a conclusion, the paper shows that the total robustness is attained by integrating advances of control technique on the electrical aspect and the mechanical aspect. There are numerous variations of controller by possible combinations of these two aspects according to applications. >

Perfect tracking control based on multirate feedforward control with generalized sampling periods

In this paper, a novel perfect tracking control method based on multirate feedforward control is proposed. The advantages of the proposed method are that: (1) the proposed multirate feedforward controller eliminates the notorious unstable zero problem in designing the discrete-time inverse system; (2) the states of the plant match the desired trajectories at every sampling point of reference input; and (3) the proposed controller is completely independent of the feedback characteristics. Thus, highly robust performance is assured by the robust feedback controller. Moreover, by generalizing the relationship between the sampling period of plant output and the control period of plant input, the proposed method can be applied to various systems with hardware restrictions of these periods, which leads to higher performance. Next, it is shown that the structure of the proposed perfect tracking controller is very simple and clear. Illustrative examples of position control using a DC servomotor are presented, and simulations and experiments demonstrate the advantages of this approach.

Model Reference Adaptive Controller-Based Rotor Resistance and Speed Estimation Techniques for Vector Controlled Induction Motor Drive Utilizing Reactive Power

In this paper, a detailed study on the model reference adaptive controller (MRAC) utilizing the reactive power is presented for the online estimation of rotor resistance to maintain proper flux orientation in an indirect vector controlled induction motor drive. Selection of reactive power as the functional candidate in the MRAC automatically makes the system immune to the variation of stator resistance. Moreover, the unique formation of the MRAC with the instantaneous and steady-state reactive power completely eliminates the requirement of any flux estimation in the process of computation. Thus, the method is less sensitive to integrator-related problems like drift and saturation (requiring no integration). This also makes the estimation at or near zero speed quite accurate. Adding flux estimators to the MRAC, a speed sensorless scheme is developed. Simulation and experimental results have been presented to confirm the effectiveness of the technique.

Direct Yaw-Moment Control of an In-Wheel-Motored Electric Vehicle Based on Body Slip Angle Fuzzy Observer

A stabilizing observer-based control algorithm for an in-wheel-motored vehicle is proposed, which generates direct yaw moment to compensate for the state deviations. The control scheme is based on a fuzzy rule-based body slip angle (beta) observer. In the design strategy of the fuzzy observer, the vehicle dynamics is represented by Takagi-Sugeno-like fuzzy models. Initially, local equivalent vehicle models are built using the linear approximations of vehicle dynamics for low and high lateral acceleration operating regimes, respectively. The optimal beta observer is then designed for each local model using Kalman filter theory. Finally, local observers are combined to form the overall control system by using fuzzy rules. These fuzzy rules represent the qualitative relationships among the variables associated with the nonlinear and uncertain nature of vehicle dynamics, such as tire force saturation and the influence of road adherence. An adaptation mechanism for the fuzzy membership functions has been incorporated to improve the accuracy and performance of the system. The effectiveness of this design approach has been demonstrated in simulations and in a real-time experimental setting.

Automated Impedance Matching System for Robust Wireless Power Transfer via Magnetic Resonance Coupling

Recently, a highly efficient midrange wireless transfer technology using electromagnetic resonance coupling has been proposed and has received much attention due to its practical range and efficiency. The resonance frequency of the resonators changes as the gap between the resonators changes. However, when this technology is applied in the megahertz range, the usable frequency is bounded by the industrial, scientific, and medical (ISM) band. Therefore, to achieve maximum power transmission efficiency, the resonance frequency has to be fixed within the ISM band. In this paper, an automated impedance matching (IM) system is proposed to increase the efficiency by matching the resonance frequency of the resonator pair to that of the power source. The simulations and experiments verify that the IM circuits can change the resonance frequency to 13.56 MHz (in the ISM band) for different air gaps, improving the power transfer efficiency. Experiments also verified that automated IM can be easily achieved just by observing and minimizing the reflected wave at the transmitting side of the system.