We have proposed a current-observer-based speed-sensorless vector control system that is in a rotating reference frame and takes into account iron loss. By deriving a linear model and by computing the trajectories of poles and zeros, the system stability on various parameters such as operating points, observer gain, controller gain and stator resistance has been investigated. Furthermore, an exact analytical model including PWM control, dead time and non-ideal features of power devices is developed. The characteristic improvement and stability limit of the proposed system are discussed by simulation and experiment.
In this paper, force-sensorless bilateral control methods for a master-slave system with different configurations are proposed. Two types of bilateral control architectures are presented. One is based on joint space control, and the other is based on work space control. This paper discusses the difference between these control methods from the viewpoint of motion behavior in the singular configuration. Finally, actual experimental results that confirm the validity of the proposed methods are shown.
Recently, a number of methods have been proposed for estimating the rotor position of a salient pole PM motor, and methods using a high-frequency voltage can estimate the rotor position accurately, even at low speeds. In the conventional method, the rotor position is estimated indirectly by minimizing the position error signal associated with the difference between the estimated position and the real one. This paper proposes a novel direct rotor-position estimation method for salient pole PM motors. In this method, a rotating high-frequency voltage is supplied to the motor, and the rotor position is estimated directly from the high-frequency current in the motor.
Converters using active switches can improve the harmonic components of input current and the power factor. Moreover, the use of these converters can result in a reduction in the size of the footprint. However, the increase in switching losses and EMI due to high-frequency switching is a disadvantage of these converters. In this study, we propose a new active rectifier circuit topology that can reduce the switching losses and EMI by soft-switching operation. Almost unity fundamental power factor and practically good characteristics of input current harmonics can be achieved by employing a simple switching control method. The characteristics of the power and input current harmonics of the proposed converter are analyzed. Small-scale experiments were conducted and the operation principles and characteristics of the rectifier were determined.
This paper presents analysis and investigation of the skew effect on behavior and performance of a three-phase, 220/380V, 8.7/5.0A, Δ/Y connected, 4 poles, 2.2kW self-excited induction generator (SEIG) with different angles rotor skewing. A 2D finite element analysis (2D-FEA) is used to consider core loss, flux density and circuit parameters. Analysis of excitation capacitor values for the SEIG based on a steady-state equivalent circuit model including rotor skew effect is given. Skewed rotor slots with angle of 0° (non-skew), 5° and 10° for the SEIGs are employed. Testing and performance comparisons under steady-state operation with a pure resistive load have been conducted. Obtained results can be guidelines and recommendations for development of effective wind induction generators.
Conducted EMI noise flowing from the power converters to AC utility line is regulated by international commissions such as International Electrotechnical Commission (IEC). For adherence to the IEC regulations, EMI filters should be used in power electronics equipment. This paper proposes a method for analyzing the conducted EMI noise in multiple power converters connected to the same power line. In this method, the phase difference between sub-harmonic modulated carrier signals at each power converter is taken into account. The phase difference among the power converters determines the EMI noise level in a multiple-converter system, as is evident from the analysis of the waveform of the common-mode current. In addition, EMI noise suppression using a carrier-phase control is a proposed. In order to reduce volume of the EMI filter effectively, the phase difference θ should be set to 360/nN°; here, n is a high-order harmonic component at around 150kHz, and N is the number of power converters. Therefore, the conducted EMI noise can be reduced effectively with the help of the proposed phase control.
Recently, surveillance cameras have been set up everywhere, for example, in streets and public places, in order to detect irregular situations. In the existing surveillance systems, as only a handful of surveillance agents watch a large number of images acquired from surveillance cameras, there is a possibility that they may miss important scenes such as accidents or abnormal incidents. Therefore, we propose a method for sequential learning and the recognition of comprehensive behavioral patterns in crowded places. First, we comprehensively extract a flow of people from input images by using optical flow. Second, we extract behavioral patterns on the basis of change-point detection of the flow of people. Finally, in order to recognize an observed behavioral pattern, we draw a comparison between the behavioral pattern and previous behavioral patterns in the database. We verify the effectiveness of our approach by placing a surveillance camera on a campus.
This paper presents a control design methodology for high-precision positioning; in particular, the compensation for the effects of vibration modes and nonlinear friction on the positioning performance is taken into account in this methodology. In the controller design, the servo bandwidth of the feedback control loop should be expanded to compensate for the nonlinear friction, while robust stability against frequency variations in the vibration modes should be ensured. In this study, therefore, a strain feedback for vibration modes is adopted to provide robustness against the frequency variations and to improve the disturbance suppression performance by expanding the bandwidth of a disturbance observer; this strain feedback is based on the use of a piezoelectric element. The efficacy of the proposed positioning control approach has been verified by conducting experiments using a prototype for industrial table drive systems.
Current collection performance is one of the most important factors affecting the high-speed operation of Shinkansen railways. The installation accuracy of the overhead contact line has a considerable influence on the contact force fluctuation between the overhead contact line and the pantograph. However, there are no concrete guidelines that specify the acceptable range of errors when installing an overhead contact line. This paper proposes a procedure for establishing the installation guidelines, which are derived from the results of the dynamic simulation of an actual installation state. The installation guidelines for Shinkansen operation at 300 or 320km/h established according to this procedure are presented. The installation error indicators are span slope, difference of span slope, sag ratio, support point slope, and support point curvature. Under actual installation conditions, the guidelines may be violated, and hence, the installation accuracy threshold must be increased so that the guidelines are adhered to even during high-speed operations. The proposed installation guidelines are expected to contribute to the improvement of the performance, reliability, safety, and maintenance efficiency of the overhead contact line.
The torsional vibration between metal rolling rolls and a rolling mill motor, may occur in recent days, as a result of higher speed response adjustment for variable speed rolling mill motor drive system. Issues in this paper are focused on excess acceleration value, in tangential direction of the mill motor rotor, which is caused by the motor shaft torsional resonance at the white noise signal superposition to the speed reference signal of the motor drive system for the online transfer function analysis. As a result of the acceleration analysis, the acceleration values in “G” (Relative acceleration value on the basis of Gravity) can be plotted on “Bode-Diagram”, which is namely frequency response for the speed signal amplitude transmission ratio. In addition, relation between the white noise amplitude reduction and the transfer function analysis accuracy deterioration is also examined, in this paper. As the amplitude of the white noise decreases, the analysis error increases because of the reduction in the resolution when the amplitude of the white noise signal is small.
Wireless electric power distribution is very attractive to provide for mobile equipments. Wireless power distribution with capacitive coupling was proposed to overcome disadvantages of wireless power distribution with magnetic-field coupling which is the most popular way. It is however difficult to transfer large power due to small capacitance of capacitive coupling. In this paper, a new power converter suitable for wireless power distribution using capacitive coupling is proposed. In the proposed circuit, a novel one-pulse switching active negative capacitor is used to increase transfer power.
In this paper, the author proposes a simple comprehensive mathematical formulation for considering energy-saving train scheduling. The formulation is to optimize running time for each section between stations with fixing total time between origin and destination of a train. The model was demonstrated numerically with a simple railway line model with four stations and three sections. The result showed that optimal condition and energy saving effect could be evaluated easily.
A novel 2 pulses switching method for the power factor correction (PFC) single-phase voltage-doubler converter with the partial switching circuit is presented. This method fixes equally the OFF time of the 1st pulse, and the ON time of the 2nd pulse, and is the easy switching method for changing the 1st pulse width (ON time). According to this method, compared with the conventional 1 pulse switching, a high power factor can be obtained in the wide load range. The validity is demonstrated by the simulation implementations.
Welfare system laboratory in Chiba Institute of Technology consists of twenty students. The research subjects include the driving control system of electric powered wheelchairs, myoelectric hand control based on EMG signal analysis and non-daily behavior detection monitoring system for elderly people.