In recent years, linear oscillatory actuators (LOAs) employing mechanical resonance have been researched aiming at highly efficient actuators. This paper considers a cylindrical moving magnet type LOA having spring characteristics for resonant oscillation in the actuator itself An equation to express the thrust of the proposed LOA is derived using a permeance model, and calculation results by the permeance analysis and magnetic field analysis are compared with actual measured results. The thrust constants by the permeance analysis and magnetic field analysis agree with the measurement, and the permeance analysis with a short calculation time is effective in calculation of the thrust constant. The magnetic field analysis is effective in the calculation of the spring characteristics of static thrusts. In addition, the optimization of the size of the proposed LOA based on the motor constant is investigated A relational equation of the size of the LOA and the motor constant is derived. From calculation results on the motor constant using the permeance analysis and magnetic field analysis, the effectiveness of the permeance analysis with a short calculation time is confirmed. Moreover, by focusing on the motor constant below the same thrust constant, it is found that the coil resistance is effective as optimization indices identical to the motor constant.
We have developed a calculation method for the strand current distributions in the turbine generator armature windings. These distributions are calculated by using a circuit equation and a 3D finite element method. In the circuit equation, the strand current is solved by introducing a circulating current at each strand of the armature windings. The induced voltage in the circuit equation is produced by leakage flux of the coil end region. The leakage flux is obtained by the 3D finite element method. The calculated strand current distributions had good agreement with the measurements of 360-degree, 450-degree and 540-degree transposed model coils.
For the end effect of linear induction motor (LIM), the authors propose a new concept that the end effect can be compensated only by the supply of secondary current synchronized with the current of LIM in front of the entry end of LIM, without considering with the flux density distribution in the LIM primary region. As a concrete method to supply the secondary current in front of LIM, the authors propose the rotator with rare-earth type permanent magnets which has strong flux density without ohmic loss, and does not cause the power factor problem even for the influence of end effect. The results of analytical study on the numerical example of LIM designed for subway are as follows. This method can make the flux density and thrust density distribution in the LIM primary region almost agree with those of the case without end effect. This method can compensate the thrust, power factor, efficiency of LIM at the rated speed to coincide with the characteristics without end effect. There is no problem in the slip characteristic curves of LIM with the compensator, although the compensator only rotates synchronizing with the frequency of LIM. The effect of compensation becomes large in the lower slip. The force to rotate the compensator is very small in the suitable design.
This paper studies properties and reducing techniques of cogging torque in brushless motors with surface permanent magnets and winding slots. Desirable combination between stator slots and magnet poles, and relation between the slots and added notches are shown. in order to minimize cogging torque, from the standpoint that cogging is mainly generated by fluctuation of 6th and 12th harmonic components in airgap magnetic energy lost by the stator slot openings. Next, the proposed techniques are verified in the combination of poles and slots at typical 12 slots motors by using FEM simulation of two-dimensional model, and it is shown that bevelling of stator pole-tips reduces the cogging torque, especially in the motor with 12 slots and 10 poles. Last, 6 slots and 4 poles motors with the added notches is calculated on the same 2D-FEM and it is shown that type B delivers better result in airgap magnetic flux distribution with rising part of quasi-sinusoidal waveform.
Linear oscillatory actuator can produce high-speed rectilinear vibration efficiently, without motion converting mechanisms. However, we need to reduce the reaction force and moment caused by main vibration for its application. So far, the method for vibration reduction that two moving elements of magnetic circuit are counter driven is reported, but it needs complicated construction for cylindrical models. In order to solve this problem, we propose linear oscillatory actuator with dynamic vibration control as a new construction and describe its principle of operation. Furthermore, we evaluate the performances of the actuator by computer simulation and confirm them by a prototype.
This paper presents the analytical results of output voltage ripple for a buck converter with synchronous rectifier. The conventional analysis of the output voltage ripple is assumed that the inductor current ripple is equal to the ripple current of the smoothing capacitor and that the equivalent series resistance (ESR) of the smoothing capacitor is sufficiently small or sufficiently large. However, if the load impedance is not so much larger than the impedance of the smoothing capacitor including ESR, this assumption is not correct. In this paper, we consider the cases that the inductor current ripple is not always equal to the ripple current of the smoothing capacitor and that there are no restriction on ESR. From the analytical results, it is shown that the output voltage ripple has four modes which are determined by the relation of load resistance, the capacitance, the ESR, the switching cycle, and the duty ratio. As a result of analysis, we show the lower limit of the ripple rate of the output voltage. The analytical results are confirmed by simulations and experiments.
Travel time is one of the most important traffic data. Although it has been studied to estimate it for a long time, there are still many problems about accuracy and measuring delay. So, we have developed an algorithm to match vehicles based on their characteristics, which are measurable by popular vehicle detectors and to estimate accurate travel time with short delay. As a result of evaluation, we demonstrate that this algorithm can estimate accurate travel time to be practical. Moreover, we improve this algorithm to be appropriate for practical use and evaluate it.
This paper presents a method for a magnetic pole shape optimization using a neural network. An IIR type neural network is proposed for this optimization. This neural network is characterized of delay elements, which exist at inputs and outputs of each neuron. At outputs, the signal is connected to input via delay elements in feedback form. These delay elements have a roll of memory action and stabilization due to feedback connection during BP learning process calculation. Hence, the computation for learning process based on back propagation algorithm converges faster than that of the ordinary feed forward type neural network, and is less in time. Finally, the conclusions were obtained that the proposed neural network could reduce the iteration process comparing with that of the ordinary feed forward type neural network, and useful for a magnetic pole shape optimization.
Synchronous machine generates the sinusoidal voltage on the balanced load operation. In case of the line-to-line short circuit, it generates the harmonic voltage on the open-phase of synchronous machine, if the direct and quadrature subtransient reactance are not equal as the machine without conection of the damper windings between poles. The harmonic orders of the voltage waveform on the open-phase winding consist of not only odd numbers, but also even numbers. When this harmonic voltage is resonant with network with capacitor, the overvoltage arise on the network. This paper shows the voltage waveform and the harmonic contents of the open-phase voltage by the analytical voltage equation without decay of the magnetic flux.
This paper proposes a new simple maximum power point tracking (MPPT) control scheme for a PV system without using conventional “mountain climbing” optimum operating point searching technique. Although no information is needed on PV array, the generated output power is maximized by utilizing limit cycle phenomena occurring on equilibrium/non-equilibrium boundary of system power flow. A parameter design procedure to determine operating period based on a theoretical model is presented. It has turned out that the operating period of limit cycle is kept constant depending on the circuit and control parameters irrespective of the insolation conditions of PV array, Availability of the proposed new MPPT control scheme has been shown by simulation and experimental results.
In analyzing electrical apparatus excited from a constant voltage source such as rotating machines by the time-stepping Finite Element method, undesirable initial values often cause a large number of iterations and thus result in a long computing time. In this paper, with this background, we propose a novel acceleration method that improves the convergence characteristics of the time-stepping FE analysis for a motor excited from a constant voltage source. The proposed method enables us to sufficiently reduce the computing time by providing appropriate initial values to unknowns. In the method, the primary and secondary currents of an induction motor in steady-state operation are precisely estimated by means of both the equivalent circuit of a motor and the initial transient waveform of the currents obtained by the FE analysis, Finally, some numerical results, which demonstrate the validity of the proposed method, are also presented.
In this paper a dynamic circuit system model of active three-phase current-source PWM converter for Power Factor Correction is described on the basis of instantaneous space vector modulation scheme. The formulation of the discretized system and control algorithm to achieve the deadbeat responses of state variables in the utility AC power side low pass filter of this converter are evaluated and discussed from an experimental point of view. The system response of this converter is much faster and transient oscillations of both source current and capacitor voltage are suppressed effectively, though the state variable in the state feedback is only the current obtained from the precise current sensor interface circuit.
This paper presents a visual servoing method using the stereo camera to control the manipulator pose (position and orientation) with respect to an object pose (position and orientation). To represent the object pose with respect to cameras mounted at the end of manipulator, we use the virtual object points. Based on the translation and the rotation operation applied to a predefined template points, the virtual object points are generated. The translation operation is determined from the single feature point that represents the estimation of the object position. The rotation operation is determined from the virtual angle calculated from the difference of the object area and the reference model area. The control signal to move the manipulator is derived from the error signal between the virtual object points and its desired values. Experiments conducted on a 3-links serial planar manipulator demonstrated the performance of the proposed method.
This paper presents a single inductor snubber-assisted full bridge type high frequency series resonant inverter using MOSFETs for the silent discharge type excimer lamp drive, which can achieve ZCS commutation. Its operating principle is presented, together with its output power regulation characteristicsbased on pulse density modulation.