Katsubumi Tajima

A spice model of orthogonal-core transformers

This paper deals with a numerical model of orthogonal‐core transformers for use in spice. The model was devised on the basis of the magnetic circuit of the orthogonal‐core with the saturation and hysteresis effects. Using the numerical model, the behavior of the dc‐ac converter constructed with the orthogonal‐core transformers and square‐wave transistor choppers was analyzed. The calculated values and measured ones show a good agreement. The method presented here is suitable for the circuit analysis and design optimization of the dc‐ac converter taking account of nonlinear characteristics of the orthognal‐cores and semiconductor devices used in the converter.

Reluctance network analysis of an orthogonal-core type parametric induction motor

In this paper, an analytical method of an orthogonal-core type parametric induction motor is proposed, based on a reluctance network model of the stator. The model is derived by a similar technique applied to an orthogonal-core transformer. Using this model the parametric oscillation characteristic of the motor, without a rotor, is computed. The simulation results agree well with the experiments. It is obvious that the analytical model of the stator presented here is proper for analysis of the motor and that, by use of this model and a suitable analytical model of the rotor, the motor characteristics can be analyzed.

Adaptive Keypose Extraction from Motion Capture Data

In this paper, we present a novel method to extract keyposes from motion-capture data streams. It adaptively extracts keyposes in response to the motion characteristics of a given data stream. We adopt an approach to detect local minima in the temporal variation of motion speed. In the developed algorithm, the intensity of each local minimum is first evaluated by using a set of signals; it is obtained by applying a set of low-pass filters to a one-dimensional motion-speed data stream. The cut-off frequencies of the filters are distributed over a wide frequency range. By adding up the speed-descent values of each local minimum over all the signals, we exhaustively obtain the information on its intensity provided at all the time-scale levels covered by a given data stream. Then, the obtained intensity values are categorized by a clustering algorithm; the local minima categorized as those of little significance are deleted and the remaining ones are fixed as those giving keyposes. Experimental results showed that the present method provided results comparable to the best of those given by the methods previously proposed. This was achieved without readjusting the values of parameters used in the algorithm. Readjustment was indispensable for the other methods to obtain good results.

Effects of Power Loss Reduction with Ferrite Magnetic Wedge on Capacitor Motor.

The authors have inserted ferrite magnetic wedges into the stator slot openings of the capacitor motor to decrease the pulsation of flux density distribution in the air gap. As a result, the iron loss was reduced greatly to increase the motor efficiency and to improve other running characteristics.

A gain scheduling speed control of a small DC motor through IP network

When IP network-based control systems of small DC motors are controlled, varying time delays and packet losses through the network cause the performance degradation. A simple scheme for overcoming it is that, using jitter buffer, varying delays is treated as constant delays in the systems. That is, control designs are done as the systems with dead times. Here the issues are how much buffering time jitter buffer needs. In this paper, a scheme applying gain scheduling and jitter buffer is proposed. For confirming the effectiveness, speed control experiments of a small DC motor through IP networks are conducted, and it is shown that the scheme is effective.

Effect of ferrite magnetic wedge on capacitor motor characteristics under triac control

The running characteristics of the split-phase capacitor motor in which a triac is connected in series with the motor circuit to control the applied voltage in accordance with the load conditions are studied. Ferrite magnetic wedges are inserted into the slot openings on the motor stator. The wedging effect on the motor characteristics is studied. When the ferrite wedges are inserted into the slot openings, the flux density pulsation in the air gap is decreased greatly to decrease the inner power losses, resulting in the improvement of motor efficiency and characteristics. >

Effect of Ferrite Magnetic Wedge on Capacitor Motor Characteristics in Triac Control

Split-phase capacitor motors are commonly used to drive household electric appliances. The motor has some slots and teeth to embed electric conductors or coils. The presence of the slots and teeth induces the variation of magnetic reluctance through the magnetic circuit to introduce heavy pulsation of the air gap flux. Thus, the voltage, current and torque of the motor become oscillative to increase the electric power loss and finally to reduce the motor efficiency. First, the authors discuss the characteristics of a 3-phase cage-type induction motor in which the ferrite magnetic wedges have been installed into the stator slot openings of the motor to smooth the air gap flux pulsation and to decrease the electric power loss, resulting in improved motor efficiency. If the motor is driven by the voltage source in accordance with the loading condition, more economical operation will be achieved. In this study, a nonsinusoidal voltage controlled by the switching element of a triac has been applied to a capacitor motor with wedges of ferrite magnetic materials. This paper reports on the interesting results obtained.

A study of network emulation for IP network-based control system of a small motor

In networked control system (NCS) though IP networks, there are the issues such that time delays, its jitter and packet losses cause control performance degradation. Hence, many control schemes against the issues have been developed. For evaluating the effectiveness of the scheme, control experiments generally need to be done under actual IP networks. However, in actual networks, it is difficult to experiment under various conditions. Hence, the evaluation should be done under networks emulated by emulators because they can make the various realistic conditions. Therefore, it is important to confirm the validity of emulator in the case of using in NCS. In this paper, we discuss the validity of a popular network emulator built-in Linux, called netem, in terms of NCS. As a result, it has been found by experiment that netem in a recent Linux kernel can work well as emulator in NCS.

Development of a Visualization Method for Motion-characteristic Distribution of Japanese Folk Dances - A Case Study of the Bon Odori Dance

This study proposes a method to systematically visualize the motion-characteristic distribution of Japanese folk dances passed down in a certain area. This is accomplished by adopting an approach that involves analyzing motion-capture data collected from the dances. The visualization process in the proposed method consists of three stages. The first stage is the modeling of the relationship among motion-capture data, folk dances, and the settlements in which folk dances have been passed down. This relationship is modeled as a hierarchical-structure model. The second stage is the extraction of motion characteristics from motion-capture data streams. The motion characteristics of each data stream are summarized as a fourteen-dimensional feature vector. The third stage is the visualization of the motion-characteristic distribution of the dances investigated. Each of the dances is mapped on a two-dimensional scatter plot in accordance with the feature quantities obtained in the second stage. Information on the hierarchicalstructure model constructed in the first stage is also displayed. The analysis results for the distribution of Bon Odori dances showed that the proposed method could have almost completely visualized the motion-characteristic distribution of sample folk dances, while also demonstrating consistency with the knowledge of the dances acquired in the previous studies.

Low-dimensional Feature Vector Extraction from Motion Capture Data by Phase Plane Analysis

This paper proposes a method to obtain a low-dimensional feature vector appropriately representing the characteristics of a given motion-capture data stream. The feature vector is derived based on the concept of phase plane analysis. A set of phase plane trajectories are obtained from the temporal variation of the state variables representing the body-segment arrangement. The information on six motion-characteristic properties is extracted from the shapes of the trajectories, and used as the components of a six-dimensional feature vector. The experimental results showed the effectiveness and limitation of the proposed method.