This paper presents an initial rotor position estimation of the position-sensorless salient-pole brushless dc motor. To estimate the initial rotor position, the rectangular pulsewise voltages are applied from the inverter to the motor. Since the three-phase winding inductances are a function of the rotor position, the different line current responses are obtained according to the rotor position. The current peaks are used to estimate the initial rotor position. The estimation is very practical because the estimation is not influenced by the motor parameter variation and the estimation process time is as short as 1 msec. The proposed estimation algorithm of the initial rotor position is verified by experiment with 6-pole 200W test motor. The experiment shows the successful position estimation within 12.9-degree error.
This paper proposes a new framework for automating sensory inspections in which contents are described by limit samples alone. A bottom-up approach is presently attempting to cope with such complex inspections. Identification of the psychological structure of a human inspector is studied by analyzing the data of evaluation experiments, and the relation between human impressions and image features is examined in order to automate the sensory inspection. In this paper, the appearance inspection of an automobile windshield by a projected checker pattern is treated as an example. Sensory scores are calculated by the comparative evaluation of defective CG images generated by a defect simulator. The relation between the sensory scores of inspectors and image features by image processing is learned by neural networks. The image features that contribute to the human judgment of the inspection are specified by a sensitivity analysis of the neural networks.
Induction motor drive with inverter control, which can reduce the total weight of the system, has been introduced to the Shinkansen trains in order to achieve high speed transportation. The individual-motor-control type 953 train, which is a part of the STAR21 prototype Shinkansen for high speed experimental run, was used for measurement running, in which we observed wheel slip and adjusted re-adhesion control parameters at the speed of 200 to 300km/h. It was found that the slip detection within one percent speed difference from the reference, was possible by adopting sensitive detecting method. Quick torque reduction by sudden reduction of motor current was necessary for re-adhesion control, and one-second waiting time before re-applying current was also inevitable. For re-applying the current, an exponential curve with four-second time constant was proved to be effective. By these tests, high speed performance and re-adhesion characteristics improvement by adjusting control parameters were obtained. To the next step, for example creep control, which utilizes fine continuous slip, should be investigated in order to keep enough torque minimizing current reduction during re-adhesion control.
Recently, Electro-Magnetic Interference (EMI) and high frequency leakage current are grave concern for power supply authorities. Due to rapid switching of high current and high voltage, interference emission is a serious problem in many switching power circuit. However, high frequency switching is neccesary for the reduction of size and the improvement of performance of the products. Usually, EMI noise reduction is tried to accomplish by using EMI filters and shielding products. But, in many cases, those trial resulted in unsatisfactory because the analytical investigation was not performed. Recently, the analysis of high-frequency leakage currnt caused by the step change of common mode voltage produced by the PWM inverter was reported. But the other cause of high-frequency leakage current did not being made clear. In this paper, it is clarified theoretically that the parasitic capacitor between the heat-sink and the switching semiconductor devices cause high-frequency leakage current. Furthermore, this paper shows that equalization of the parasitic capacitors and increase of the impedance for grounding the heat-sink at high-frequency range makes high-frequency leakage current reduce. Finaly, those results are verified from simulation and bread board set-up.
In this paper a novel three phase power conversion system with four units of voltage type single phase inverters, a cycloconverter and Scott connected transformers is proposed for harmonic reduction. The basic operation is described for the conversion system. Turn ratios of the transformers that minimize the total distortion factor of line-to-line voltages, capacity of the transformers and current capacity required for the switching devices are discussed in detail. The total distortion factor of the line-to-line voltages is greatly reduced. The effectiveness of the proposed conversion system is confirmed by experimental results of inverting, rectifying and reactive power compensating operation.
The authors have developed a new looper control system for hot strip mill finisher using H∞ control method, and have obtained good results. Looper control is one of the most important control items in hot strip mills. Loopers are placed between each rolling stands. Strip tension is controlled by raising and lowering the looper, and by changing rolling speed. The tension severely affects the quality of steel products such as thickness and width, so it is very important to control stably both looper angle and strip tension as their target values. This paper presents the design way of the looper H∞ controller, and shows some on-line results. Two types of H∞ controller, i.e. output feedback type and state feedback type, are discussed. And a new way of reducing strip tension fluctuation using looper angle is proposed. Also performances of previous looper control such as conventional PI control and non-interactive control, and that of the looper H∞ control are compared. Actually controlled data show that the performance of H∞ control is better than the others.
Camcoders would be more compact, lighter and lower-cost, if driving motors are built in lens barrels. The motors built in lens barrels have been proposed in the previous paper. A stator(lens barrel) and a rotor(variator lens) function as a female screw and a male screw, respectively. To reduce the power consumption of this motor, armature windings ampere turns have to be reduced by reducing a friction torque between the female screw and male screw. An new unique mechanism for supporting a rotor of a direct drive motor built in a lens barrel, in which balls are inserted between a outer ring raceway and inner ring raceway, is proposed in this paper. Two type of rotor, (l) the cascaded rotor which has a magnet with the lens and the inner raceway in cascade, and (2) raceway-magnet rotor which has the lens fixed in a grooved magnet are invented. Evaluations for three type of rotors, cascaded, raceway-magnet and separate-screw in the previous paper are presented. Armature winding ampere turns of cascaded and raceway-magnet rotor are 33% and 28%, respectively, whrere ampere turns of separate-screw rotor is 100%.
An electrical and thermal mathematical dynamic model for a three-phase squirrel-cage induction motor is described to evaluate, via microcomputer, stator winding, rotor winding, stator core and rotor core instantaneous temperature rises for motors operating fed from sinusoidal and nonsinusoidal (inverter) voltage power supplies and driving continuous and intermittent load duties, including startings and brakings. It is required regular manufacturer bulletin data and also stator core, stator winding, rotor core and rotor winding masses. The model takes into account the skin effect on rotor parameters and the changings of the winding electrical resistances with the respective machine part temperatures.