Variable frequency induction heating has great potential for industrial heating applications due to the possibility of achieving heating distribution control; however, large-scale induction heating with variable frequency has not yet been introduced for practical use. This paper proposes a high frequency soft-switching inverter for induction heating that can achieve variable frequency operation. One challenge of variable frequency induction heating is increasing power electronics ratings. This paper indicates that its current source type dc-link configuration and soft-switching characteristics can make it possible to build a large-scale system with variable frequency capability. A 90-kVA 150-1000Hz variable frequency experimental power supply for steel strip induction heating was developed. Experiments confirmed the feasibility of variable frequency induction heating with proposed converter and the advantages of variable frequency operation.
Induction heating technologies have been the standard technologies employed in steel making processes because they are clean, they have a high energy density, they are highly the controllable, etc. However, there is a problem in using them; in general, frequencies of the electric circuits have to be kept fixed to improve their power factors, and this constraint makes the processes inflexible. In order to overcome this problem, we have developed a new heating technique-variable frequency power supply with magnetic energy recovery switching. This technique helps us in improving the quality of steel products as well as the productivity. We have also performed numerical calculations and experiments to evaluate its effect on temperature distributions on heated steel plates. The obtained results indicate that the application of the technique in steel making processes would be advantageous.
It is well known that a good method for improving the fuel economy is to engage the lock-up clutch of a torque converter. In the lock-up clutch, it is necessary to control the slip speed from low vehicle speeds in order to improve the fuel-consumption performance. However, the plant parameters change with turbine speed, and the control of the slip speed is difficult. In this study, we apply the gain-scheduled H∞ control method to the slip-speed-control system of the lock-up clutch. The implementation of gain-scheduled controllers is discussed in this paper. The effectiveness of the proposed method was verified by performing simulations and experiments in which the performance of the gain-scheduled controller was compared with that of a controller designed by using the µ-synthesis.
An extension of a special analytical commutation method for long-stroke magnetically levitated moving magnet type planar actuators is presented. It enables the use of coils that are influenced by the end-effect of the Halbach magnet array. They are located near the edge of the magnet array and are referred to as edge coils. The method adds those coils to the commutation correcting for the end-effect by modeling it as a multiplicative error in the commutation. As a result thermal losses are decreased while the error in the commutation is kept in the same order of magnitude. Experiments support the results.
Interior permanent magnet motors (IPMSMs) are employed for the drive motors of electric and hybrid vehicles. Therefore, control method to be used in the overmodulation range of the inverter is important to achieve fast torque response and expand the operating range of the IPMSMs. In this paper, a control method based on perfect tracking control and the PWM (Pulse Width Modulation) hold model in the overmodulation range is proposed. Finally, simulations and experiments are performed to show the advantages of the proposed method.
This paper describes a control scheme for the stable operation of a two-wheel driven mobile manipulator. The manipulator has excellent mobility and manipulability, and is capable of many functions. Therefore, it is very effective for use in human environments. However, since the mobile manipulator is unstable, it is difficult to perform specific tasks such as tasks requiring the precise movement of the manipulator and those that need large power, even if its attitude is controlled. Hence, in this paper, landing motion control is proposed to enable the stable operation of the manipulator. In addition, in order to switch from the landing mode to the moving mode, rising motion control is proposed. The validity of the proposed method was confirmed by experimental results.
Recently, there has been considerable progress in wireless power transfer technology. The use of magnetic resonant coupling has resulted in a large air gap and high efficiency. So far, this technology has been studied by considering an equivalent circuit. However, the limits on the air gap and efficiency are not specified by the equivalent circuit. This paper proposes equations that specify the limits on the air gap and efficiency for wireless power transfer via magnetic resonant coupling. Moreover, circuit conditions that are required to achieve a large air gap and high efficiency are proposed.
In manufacturing processes, inappropriate thermal distribution, which is observed in both steady and transient states of the thermal plant, leads to inferior quality. For a plant with strong thermal interaction, decoupling control is effective in precisely tuning the control system. We proposed the decoupling controller based on the temperature-difference feedback model. However, no parameter-identification method of thermal interaction has been presented so far. Traditionally, iterative tuning by trial and error has been used to tune the controller parameters. In the case of an industrial plant, the tuning time would be long because of the large time constants of the plant. Recently, the virtual reference feedback tuning (VRFT) method, which can be used for off-line tuning of the controller parameters using a set of I/O data, has been studied to examine the possibility of shortening the tuning time. In this paper, a VRFT method for the feedback decoupling controller is proposed for a two-dimensional heat plate by taking consideration the thermal interaction property. The effectiveness of this VRFT method is evaluated by performing an experimental simulation.
The assist effects of the permanent magnets in salient-pole synchronous generators are investigated by the electromagnetic field analysis. The flux and voltage are separated by the finite element analyses due to their origins. The measured and calculated results are compared in order to verify the calculation. It is revealed that there are two assist effects of the magnets on the improvement of the generator characteristics. One effect is the reduction in the size of the saturated region at the rotor core. The other effect is the direct flux linkage with the armature windings. The former effect is dominant at the rated load condition. The latter effect increases when the rotor core is oversaturated and compensates for the decrease in the former effect.
This paper proposes a new control method for the previously proposed large-capacity capacitor simulator, which can perform an inner series resistor of the EDLCs. In the proposed large-capacity capacitor simulator, one of three legs performs a bi-directional dc-dc converter. The others are used for a single-phase PWM rectifier. In the charging operation of the proposed large-capacity simulator, one-leg is used as a boost converter. Most power, which is stored in the proposed simulator, is injected to the utility through the PWM rectifier. In the discharging operation, the one-leg performs a buck converter. Most power, which is supplied to the load, is from the utility through the PWM rectifier. Thus the proposed simulator performs a large-capacity capacitor with an inner resistor in both charging and discharging operations. The basic principle of the proposed simulator is discussed in detail. The validity and excellent practicability of the proposed control method for the large-capacity capacitor simulator are confirmed using PSIM software.
Conventional voltage equalizers or equalization chargers, which are used for series-connected energy storage cells to eliminate cell voltage imbalance, consisting of a number of switches or transformers tend to be complex with the number of series connection of the energy storage cells. A novel voltage equalization charger consisting only of capacitors, diodes, and an ac power source is proposed, and its dc equivalent circuit expressed by resistors and a dc power source is derived in this paper. Experimental charge tests demonstrated that series-connected EDLCs could be charged up to the uniform voltage by the proposed equalization charger.
Novel marine diesel particulate filter (DPF) using high frequency induction heating is developed. Particulate matter exhausted from diesel engine is trapped by the DPF and is successfully burned by induction heating. The effectiveness of the DPF system is verified by experiments.
This paper proposes a new analysis about sensorless drive of permanent-magnet synchronous motors. The analytical result shows that phase and speed estimates obtained in quasi-synchronous reference frame are equivalent to those in stationary reference frame.
Power electronics laboratory in Tokyo Metropolitan University carries out research on power conversion circuit. Two faculty members, two technical staffs and 22 students belong to the laboratory. The laboratory plans seven research projects, two education projects and one social event in this year.