High-frequency noise induced to a ground system causes disturbance to electronic devices. However, there have been only a few studies into the high-frequency impedance characteristics of ground systems from the viewpoint of safe and stable functioning of electronic devices. For the present study, the authors installed ground electrodes and measured the impedance characteristics of the ground system. This paper shows that the parallel resonance occurs at specific frequencies. The authors found that the frequency of parallel resonance depend more on the length of the ground conductor than the distance between ground electrodes or their length. This paper also shows the problems caused by the parallel resonance of ground conductors. And finally the authors propose a type of attenuator, composed of a coil and resistor connected in parallel, to suppress the impedance increase at the parallel resonance frequencies.
It is well known that frame vibration occurs in driving permanent magnet synchronous motors (PMSM). The authors have suggested a suppression method of the frame vibration by means of Fourier series and repetitive control. The method requires an acceleration sensor and a position sensor. However, the use of such a sensor is not desired from a point of view of cost of the system. Therefore, this paper proposes a sensorless suppression control method for the frame vibration. The effectiveness of the proposed method is illustrated through some experiments.
With an advancement of information technology, record and reproduction technologies of sound and image have been improved. On the other hand, record and reproduction technologies of haptic display are developing. This paper proposes a method for abstraction and reproduction of environmental stiffness based on frequency characteristic. In the proposed method, environmental position response from force input is measured. Then, Fourier transformed position response divided by Fourier transformed force input is calculated for abstracting environmental frequency characteristic. Control system for the reproduction of environment is designed based on the abstracted environmental frequency characteristic. Finite Impulse Response (FIR) filter is utilized for the reproduction of environmental frequency characteristic. Finally, the validity of the proposed method is shown by experimental results.
A new shift-by-wire system having a stand-by mechanical link with a backlash has been proposed. The link directly connects the select lever and the manual lever of the automatic transmission in case of emergency. Thus it is necessary to keep the backlash free during normal operations without generating a force. The angles of the manual lever driven by an actuator should follow the angles of the select lever exactly and quickly. A two-degrees-of-freedom model matching control is developed to meet this requirement. It is shown that the backlash is kept to be free during range select operation.
In inverter-converter driving systems for AC electric cars, the DC input voltage of an inverter contains a ripple component with a frequency that is twice as high as the line voltage frequency, because of a single-phase converter. The ripple component of the inverter input voltage causes pulsations on torques and currents of driving motors. To decrease the pulsations, a beat-less control method, which modifies a slip frequency depending on the ripple component, is applied to the inverter control. In the present paper, the beat-less control method was analyzed in the frequency domain. In the first step of the analysis, transfer functions, which revealed the relationship among the ripple component of the inverter input voltage, the slip frequency, the motor torque pulsation and the current pulsation, were derived with a synchronous rotating model of induction motors. An analysis model of the beat-less control method was then constructed using the transfer functions. The optimal setting of the control method was obtained according to the analysis model. The transfer functions and the analysis model were verified through simulations.
This paper presents a design method for a linear synchronous motor with half-wave-rectified self excitation; this method enables the construction of a motor with small thrust ripple. The mover of the motor is designed to be asymmetrical for reducing the thrust ripple. First, we design the structure of the asymmetrical mover and the field winding of the mover by using the finite element method and a characteristic equation. The asymmetrical mover is built, and the thrust ripple reduction is verified by performing experiments. Next, the linear synchronous motor is modeled using a circuit simulator in order to confirm its high-speed performance. The operation characteristics are clarified by performing a simulation.
DC microgrid is a novel power system using dc distribution in order to provide a super high quality electric power. The dc distribution system is suitable for dc output type distributed generations such as photovoltaic and fuel cells, and energy storages such as batteries and electric double layer capacitors. Power is distributed through dc distribution line and converted to required ac or dc voltage by converters placed near loads. Load-side single phase inverters are connected through transformers in order to share active and reactive power. In this paper, a power sharing control scheme was proposed, and the power sharing characteristics were demonstrated by experimental results.
Once the break-down of the train schedule occurs, the crew schedule as well as the train schedule has to be modified as quickly as possible to restore them. In this paper, we propose an algorithm for automatically modifying a crew schedule that takes all constraints into consideration, presenting a model of the combined problem of crews and trains. The proposed algorithm builds an initial solution by relaxing some of the constraint conditions, and then uses a Taboo-search method to revise this solution in order to minimize the degree of constraint violation resulting from these relaxed conditions. Then we show not only that the algorithm can generate a constraint satisfaction solution, but also that the solution will satisfy the experts. That is, we show the proposed algorithm is capable of producing a usable solution in a short time by applying to actual cases of train-schedule break-down, and that the solution is at least as good as those produced manually, by comparing the both solutions with several point of view.
In this paper, we propose a calculation method for iron loss in rotating machines; the method employs the finite element method considering eddy currents in electrical steel sheets. First, the electromagnetic field distribution and iron loss of several types of electrical steel sheets are calculated by the proposed method formulated by a 1-dimensional model. The results are compared with those of experiments and the conventional method in order to verify the validity of the proposed method. The influences of the skin effect and magnetic saturation of the electrical steel sheets on the iron loss characteristics are also investigated. Next, the proposed method formulated by a 3-dimentional model is applied to several types of rotating machines. It is clarified that the skin effect is remarkable in the case of high-frequency harmonic fields and that the direct consideration of the eddy currents by the finite element method is indispensable in such cases.
This paper presents a feedforward compensation approach for nonlinear disturbances in ball-screw-driven table positioning systems. The compensator design is focussed on minimizing the effects of nonlinear disturbances on positioning performance. This is achieved through the use of a mathematical model of precise micrometer disturbance characteristics produced by nonlinear spring behaviors during inching and reciprocating motions. Based on this model, a feedfoward disturbance compensation is applied to improve the disturbance suppression capability. The effectiveness of the proposed positioning control approach has been verified by experiments using a table drive system on a machine stand.