The contact wire breaking accident caused by the arc between the contact wire and the pantograph happens rarely in the DC electric railway system. The contact wire breaking phenomenon is discussed and investigated based on the experimental data performed 30 years ago. The material of the contact strip and the contact wire has changed, however, and the breaking characteristics of the contact wire caused by the arc should be different. In this paper, the contact wire breaking characteristics are carefully investigated using the recent materials. It is cleared that the breaking index of 750As is approximately appropriate in the limited condition and the other breaking condition is summarized based on the experimental data more than 400 times.
Energy saving control is desirable for magnetically levitated (MAGLEV) vehicles. Hybrid magnets controlled with zero power control system was able to reduce the exciting power. But such a conventional system needed to feed bipolar current and then the excitation system was complicated. To achieve a simple excitation system, a hybrid magnet with permanent magnets and divided cores was made. The magnet was a salient-pole type magnet and the poles were placed in two rows. Each pole of the iron cores was equipped with a coil to control both levitation force and lateral damping force. The coils of one side of the divided core were excited with a direct current driver so as to produce the same polarity as the permanent magnet and the others were excited the opposite polarity. The two sets of the coils were excited with direct current drivers each of which had one IGBT. The system needed only two IGBTs per magnet while the conventional zero power systems needed four IGBTs per magnet. According to our test results, the energy consumption was very small and the levitation part was able to start levitating from both upper and lower touch-down positions. In this paper, the characteristics of the proposed excitation system are shown.
This paper proposes the new realization method of error-prediction control system based on ZPET control and robust feedback control. The error-prediction control system based on ZPET control can reduce the tracking error caused by periodic disturbance compared with general repetition control. However, the proposed tracking servo system does not reduce the residual tracking error cased by the low-pass filter at the feedforward compensation and long sampling time. In order to overcome this problem, this paper proposes the new structure of the feedforward tracking control system. The modified ZPET control tracking servo system for optical disc recording system does not include the low-pass filter and its sampling time becomes faster. On the other hand, the sudden disturbance observer reduces the influence of non-periodic disturbance. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbance and the non-periodic disturbance.
This paper presents a new unified analysis of estimate errors by model-matching phase-estimation methods such as rotor-flux state-observers, back EMF state-observers, and back EMF disturbance-observers, for sensorless drive of permanent-magnet synchronous motors. Analytical solutions about estimate errors, whose validity is confirmed by numerical experiments, are rich in universality and applicability. As an example of universality and applicability, a new trajectory-oriented vector control method is proposed, which can realize directly quasi-optimal strategy minimizing total losses with no additional computational loads by simply orienting one of vector-control coordinates to the associated quasi-optimal trajectory. The coordinate orientation rule, which is analytically derived, is surprisingly simple. Consequently the trajectory-oriented vector control method can be applied to a number of conventional vector control systems using one of the model-matching phase-estimation methods.
This paper presents a new unified analysis of estimate errors by model-matching extended-back-EMF estimation methods for sensorless drive of permanent-magnet synchronous motors. Analytical solutions about estimate errors, whose validity is confirmed by numerical experiments, are rich in universality and applicability. As an example of universality and applicability, a new trajectory-oriented vector control method is proposed, which can realize directly quasi-optimal strategy minimizing total losses with no additional computational loads by simply orienting one of vector-control coordinates to the associated quasi-optimal trajectory. The coordinate orientation rule, which is analytically derived, is surprisingly simple. Consequently the trajectory-oriented vector control method can be applied to a number of conventional vector control systems using model-matching extended-back-EMF estimation methods.
This paper proposes a new generalized high-frequency voltage injection method for sensorless drive of salient-pole permanent-magnet synchronous motors. The injected high-frequency voltage has unique spatially-rotating ellipse-shape, whose both amplitudes of major and minor axes vary dependently of the motor speed, and can be designed through selecting a design parameter. The high-frequency current caused by the injected voltage, which has information of rotor phase to be estimated, is speed-independent, i.e. is not affected by the motor speed at all. Consequently, rotor phase can be estimated in wide speed range from zero to the rated speed. Through selection of the design parameter, property of the high-frequency current can be adjusted so that it fits for the associated motor-drive system consisting of a motor and an inverter. As a versatile phase estimation method for estimating rotor phase using the high-frequency current, the “mirror-phase estimation method" is re-constructed and re-proposed.
This paper describes a position sensorless control technique on AC servo motor based position control systems. Shimada et al. had previously presented a paper on a DC servo motor based position sensorless control technique using mechanical springs. It was based on a point of view that mechanical springs form the key components for the observability. On the basis of the result obtained from the successful experiment, we assumed that the AC servo motor position sensorless control system would be identical. Using vector control, the controller needs the data of the magnetic pole position on the rotor of the AC servo motor. It is not perfect sensorless control, since it use a rotary encoder. However, we introduce it and demonstrate the expreimental results as an initial step in the new control technology.
The kinetic thrust of a linear motor (LM) is measured with a load cell connected between the LM and a load motor. The case of linear oscillatory actuator (LOA), the kinetic thrust obtained using this method is not accurate, because the inertial force affects the load cell under the high-speed reciprocating motion of the LOA. In this paper, we propose a novel method of measuring kinetic thrust using an observer-inputted output of the load cell and the displacement of the load motor, and examine the proposed method. The estimated kinetic thrust Fe obtained by the observer agrees with the kinetic thrust obtained by simulation. In the measurement, the ratio of Fe to √2KfI1 (Kf is the thrust constant of the LOA, I1 is the exciting current) is 0.93 at frequency f = 37.3Hz. Fe decreases with increasing frequency because of the eddy currents in the yokes of the LOA. Therefore, it is considered that the proposed method is appropriate, as ascertained by simulation and measurement. In addition, it is necessary for the leaf spring of the LOA to be light and to have a fixed spring constant for the high-precision measurement of kinetic thrust.
This paper describes a controller design method for robots supporting human in real environment. Such robots have to cope with various interactions between robots and human environment. Furthermore, they also have to autonomously classify the interaction from sensor information and select their action according to tasks and situations. This study introduces an idea of spatial filter, a filter in space domain, to construct such a control system. The method decomposes sensor information into function modes, spatial information essential for control. The force filtering process based on function modes makes the controller design simple and explicit. Some experimental results are shown to verify the validity of the proposed method.
This paper presents the useful technique to save the computation time in the optimization process of the genetic algorithm (GA). In this technique, genes are encoded for elements as their material information to avoid re-meshing caused by the movement of nodes. Furthermore, the process of the GA is divided into two steps because it requires much computation time to apply the GA for the whole region to be analyzed at once. The usefulness and the flexibility of this technique are verified through the comparison with the usual one when it is applied to an electromagnetic clutch and a solenoid to obtain the maximum attractive force.
This paper deals with a 50-MW self-commutated BTB (Back-To-Back) system intended for power-flow control between transmission networks. It focuses on the dynamic behavior of the BTB system during single-line-to-ground (SLG) faults. During an SLG fault, a dc magnetic deviation appears in the converter-transformers used for the BTB system just after the occurrence and restoration of the fault. It is indispensable to understand an amount of deviation because it may bring magnetic saturation as well as a large amount of magnetizing current to the transformers. This paper derives theoretical equations related to the deviation during the SLG fault. The theoretical analysis developed in this paper would make significant contributions to designing the transformers.
Switched reluctance motor (SRM) drives are suitable for variable speed industrial applications because of the simple structure and high-speed capability. However, it is necessary to detect the rotor position with a position sensor attached to the motor shaft. The use of the sensor increases the cost of the drive system and machine size, and furthermore the reliability of the system is reduced. Therefore, several approaches to eliminate the position sensor have already been reported. In this paper, a position sensorless control method based on the variation of the phase inductance is described. The phase inductance regularly varies with the rotor position. The SRM is controlled without the position sensor using the de-fluxing period and the phase inductance. The turn-off timing is determined by computing the difference of angle between the sampling point and the aligned point and the variation of angle during the de-fluxing period. In the magnetic saturation region, the phase inductance at the current when the effect of the saturation starts is computed and the sensorless control can be carried out using this inductance. Experimental results show that the SRM is well controlled without the position sensor using the proposed method.
This paper proposes a simulator of EDLC, which realizes the performance equivalent to electric double-layer capacitors (EDLCs). The proposed simulator consists of an electrolytic capacitor and a two-quadrant chopper working as a current source. Its operation principle is described in the first place. The voltage dependence of capacitance of EDLCs is taken into account. The performance of the proposed EDLC simulator is verified by computer simulations.