This paper deals with a new control method for an atmospheric-pressure discharge plasma generator. The plasma generator consists of a voltage-source inverter, a step-up transformer, a resonant inductor and two parallel electrode plates. The high-frequency high voltage induced by series resonance between the equivalent capacitance of the plates and the resonant inductor generates glow plasma between the plates. However, a continuously-applied voltage may cause streamer or arc discharges instead of glow plasma, when the plates are under atmospheric pressure. This paper discusses an application of pulse density modulation (PDM) to the plasma generator, and proposes a new PDM method suitable for atmospheric-pressure plasma. A conventional PDM method repeats alternate run and stop to adjust the output power. The switching pattern is designed to minimize power variations. In contrast, the switching pattern of the proposed PDM method is designed to achieve a quick decrease in discharge current and electrode voltage during the inverter is stopped. As a result, the proposed method makes it possible to eliminate the streamer or arc discharges, leading to stable glow plasma. Experimental results are shown to verify the viability of the proposed PDM method.

View full abstract

A large number of spot-welding machines are at use in the automotive, home appliance and can-making industries. For example, two steel sheets several mm thick can be welded with a second or two of several kA of current, which supplies the requisite thermal energy. This paper outlines the development of a spot welder utilizing storage batteries as the power supply. Each time the transformer flux level reached a preset ± desired value the polarity of the primary current is switched. Welding current is output continuously until the energy required for welding is developed.

View full abstract

The impedance characteristics of the magnetic type angle sensor are analyzed by using the finite element method. The impedance characteristics were accurately calculated by taking into account high frequency characteristics of the cores and the end coils. The magnetic permeability of cores is estimated from the calculated results of impedance in high frequency region. The validity of the magnetic permeability in the analysis is confirmed by experiments.

View full abstract

Steel and copper are widely used as current collecting material for power supply in electric railways. In this field experimental studies on material wear and friction phenomena are important for improving stability and reliability of current collection in service operation. However few are reported to the effect of contact bridge formation, which is caused by separation of electrodes, in the material wear and friction phenomena, especially for different materials, such as, steel and copper.
In this paper, anode and cathode materials, which are made of same metal (either steel or copper), are separated with very low constant speed. to observe the bridge formation and contact surface after the bridge separation in detail.
As a result, melting bridge formation of 0.5mm height was observed while steel electrodes separating. In the similar test of the identical condition of the copper electrode, the observation of the bridge formation was difficult. However, the copper bridge that grew at 0.2mm height was observed, where test was conducted with separating speed slowed down to 1/10. The molten bridge was formed at the boundary on the anode side with high brightness, and this effect was seen for both steel and copper. Although this phenomena appears for both cases of steel and copper, the anode made of steel material is damaged more seriously.
Also in this paper, special strips of steel and copper, simulating the contact bridge, are studied for contact drop, contact resistance and temperature increase at contact point to melt down by increasing current slowly from zero ampere.
As the result, the resistance of the copper which is a diamagnetic material rose in a smooth quadratic curve for the increase in current (temperature), and the steel which is ferromagnetic showed the rapid increase above magnetic transformation and allotropic transformation temperature. The increase of heat quantity by decreasing of specific heat due to magnetic transformation and the consequent resistance increase are the cause of the formation of large melting bridge in the steel And Thomson effect is considered as the cause of damage of anode.

View full abstract

In this paper, a common mode equivalent circuit usable for calculating common mode current and bearing current of a 0.75kW induction motor driven by PWM inverter is proposed at first. Next, motor capacitance formulas are presented and those values are calculated for the motor, and these values are compared with experimental results. Calculated common mode impedance versus frequency based on proposed circuit is also compared with that of experimental results, and both characteristics are agree well. Finally, the validation of the proposed common mode equivalent circuit is demonstrated by the fact that the proposed circuit reproduce the experimental results of common mode current and bearing current.

View full abstract

Since the record density of hard disk drive (HDD) increased very rapidly, the required servo accuracy is getting dramatically severe. In this paper, novel feedforward (FF) control is proposed to reject the periodic disturbance based on switching scheme and open-loop observer. The advantage of proposed method is that periodic disturbance can be rejected without sacrifice of feedback performance. Several experiments are carried out to verify the control performance. First, the proposed FF method is compared with the conventional feedback (FB) control in the case of single-mode disturbance rejection. Second, multiple-mode disturbance is considered in high-frequency region which cannot be rejected by conventional technologies. The final experiments show that 20.4[%] tracking error is reduced by the proposed control algorithm.

View full abstract

In this paper we propose a technique to reduce cogging force in linear motors by decomposing it into harmonics, finding design criteria for each component of the cogging force, and applying these different criteria to the design of the motor. The hypothesis of this approach is that single actions for reducing the cogging harmonics can be added up to reduce the whole cogging force, hence, not considering cogging force as a whole. In order to validate this technique, we present the analysis of cogging force in a Permanent magnet linear motor. Through analytical and FEM analysis of the different harmonics we present some very simple single actions to minimize radically cogging force. All this actions and the proposed technique are then validated with real tests of static cogging force with different prototypes.

View full abstract

High temperature superconductor (HTS) synchronous machines are expected to have higher efficiency and smaller size than normal conductor synchronous machines, and are being developed mainly in USA and Germany. This paper describes a computation method of heat loads in cryogenic parts of HTS synchronous machines, and the evaluation study results of heat loads in HTS synchronous motors for blowers, in which Bi-2223 are used at 30K, using the computation method. From the evaluated heat loads, the required capacity of the refrigerator for HTS synchronous machines may be determined.

View full abstract

Electric Vehicles (EVs) are inherently suitable for 2-Dimension vehicle motion control. To utilize EV's advantages, body slip angle β and yaw rate γ play an important role. However, as sensors to measure β are very expensive, we need to estimate β from only variables to be measurable. In this paper, an improved estimation method for body slip angle β for EVs is proposed. This method is based on a linear observer using side acceleration a_y as well as γ information. We especially considered the design of gain matrix and succeeded in exact and robust estimation. We performed experiments by UOT MarchII. This experimental vehicle driven by four in-wheel motors was made for research on advanced control of EVs. Some experimental results are shown to verify the effectiveness of the proposed method.

View full abstract

The Field Programmable Gate Array (FPGA)-based control system for the Switched Reluctance Motor (SRM) drive with a rotor position sensor are designed and constructed. The control algorithm of the SRM requires the information of rotor position. Conventional estimation algorithms of the rotor position are deteriorated by the switching noise of the inverter. Therefore, this paper proposes the new estimation algorithm of the rotor position with suppression mode of noise. The estimation algorithm is based on the state machine which is one of the popular description methods of Very high speed integrated circuit Hardware Description Language (VHDL). The SRM drive using the proposed algorithm is tested with experimental system to confirm the operation.

View full abstract

This paper proposes a new modulation scheme providing unbalanced output terminal voltages of a standard three-leg voltage source inverter (VSI) for unsymmetrical type two-phase induction motors. This strategy allows a control method of the output voltages with typically constant V/Hz for a main winding and with voltage boost to compensate magnitude of current for an auxiliary winding. Harmonic voltage characteristics and the motor performance are investigated under a wide range of operating conditions. Practical verification is presented to confirm correctness and capabilities of the proposed technique. All results are compared to those of a conventional two-leg half bridge topology. The results show that the simulation results well agree with the experimental ones, and also the proposed scheme is superior to the conventional drive.

View full abstract

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearingless motor, both 4-pole and 2-pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three-phase windings, thus 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and then, simulation model of suspension force is constructed. It is shown that the response and the phase of suspension force are delayed in a case of cage rotors.

View full abstract

This paper proposes a method to recognize a target image area that has free location and free inclination in an objective image. This method uses curvatures that are measured in two sizes of area as the matching key to improve the reliability of matching. Besides, if the only effective edge pixels can be used for matching, it is expected that the reliability and the computational cost may be improved because the number of registered template data decreases. To realize this function, the proposed method uses the genetic algorithm (GA) to determine the best combination of effective edge pixels for matching from the huge combinations of selected edge pixels. The experimental results show that the target image areas were searched successfully in spite of reducing the number of edge pixels. The averaged matching time was about only 0.1 second by using the proposed method.

View full abstract

This paper presents an analytical estimation approach for PWM carrier loss on the rotor in the design stage of slotless permanent magnet motors. The experimental studies using 400W, 3000r/min test motor show that the eddy current on the rotor surfaced by rare-earth magnets decreases the winding inductance and increases the winding resistance as the supplied frequency rises. The resultant lower inductance for high frequency over 10kHz produces a large amount of current harmonics caused by voltage PWM as well as the carrier loss combined with the resistance increment.
At first, the frequency dependent winding inductance and resistance of test motor are estimated by 3D-finite element method considering the eddy current on the rotor. The current spectrum is subsequently calculated from the obtained frequency dependent winding impedance and the simulated voltage spectrum. The carrier loss is finally derived from the current spectrum and the calculated resistance increment. The effectiveness of the proposed estimation approach for PWM carrier loss on the rotor is experimentally verified using test motor.

View full abstract

In this paper, a 2-degree of freedom electromagnetic actuator capable of linear and rotational motion is proposed. The structure and operating principles are described and the thrust and torque characteristics are obtained using the 3D finite element method. A prototype of this model was constructed and measurements were obtained to confirm the dynamic characteristics of the actuator.

View full abstract

This paper proposes a new design method of track-seeking trajectory for hard disk drives by using final-state control method. The proposed method can obtain a feedforward control input whose frequency components are minimum at the desired frequency points. In our approach, the control input is evaluated in continuous-time domain, and the frequency components higher than the Nyquist frequency can be also optimized. Simulation and experimental results are shown to evaluate the effectiveness of the proposed method.

View full abstract

This paper proposes a new field-weakening control considering voltage saturation for vector controlled induction motor. The proposed method improves the output torque characteristics in the field-weakening region. The effectiveness of proposed method is verified by the experimental results.

View full abstract