There are few self-gap-detecting electromagnetic suspension (EMS) systems robust enough against variation of coil resistance. The authors succeeded in providing much robustness against the variation of coil resistance with a self-gap-detecting EMS system. An adaptive control for coil resistance and an exciting voltage compensator for differences between the coil resistances were applied to the self-gap-detecting EMS system. The adaptive control was applied to the feedback controller and the state observer which evaluates gap length and its change rate with respect to time. As a result, it made clear that this self-gap-detecting controller yields more robustness against mass variation to EMS systems than conventional controllers with gap detectors. This paper proposes this new self-gap-detecting technique. The adaptive control and the exciting voltage compensator will be explained. Moreover, the robustness against mass variation will be discussed. The experimental results will show a validity of the proposed technique and a possibility to apply the self-gap-detecting EMS system to practical apparatuses in industrial fields.

抄録全体を表示

Many software tools for magnetic field analysis give us distribution of magnetic flux density between Halbach arrays of permanent magnets. However, we need easier calculation tools in an early stage of development. This paper proposes an equivalent magnetic circuit method with high accuracy for field magnets provided with dual Halbach arrays.

抄録全体を表示

ドローン用の同期モータでは，集中巻多極多スロット構造と SPMSM（表面磁石同期モータ）構造が一般的である。ドライブ装置も 120 度通電方式が採用されている。一方，一般産業用モータでは，小型化・高効率化が重要課題であることから，極数╱スロット比が 2 対 3 や 4 対 3 のものが多く，ドライブ装置も 180 度通電方式で，特にハイブリッド自動車や電気自動車ではベクトル制御が適用される。本稿では，ドローン用モータが一般産業用モータと異なる構造・駆動方式を採用している必然性を明らかにするとともに，ハルバッハ配列界磁をドローン用モータに適用するとこれらの必然性が消滅し，ドローン用モータ╱ジェネレータの小型化・高効率化が実現できる可能性を論じる。

抄録全体を表示

This paper deals with a new magnetic bearing in order to decrease a rotor eccentricity. The proposed bearing system consists of moving frames, suspensions, permanent magnets, electromagnets and Zero Power controller. The system enables to avoid rotor touchdowns. A clearance between a rotor and our proposed bearing may be increased compared to conventional electromagnetic bearings, since permanent magnets are used in new bearings. However, if Zero Power controller is applied to magnetic bearings, a severe problem emerges. When a levitating rotor is subjected to external steady force, to keep equilibrium between external force and magnetic force, a position of levitating rotor may be changed. To overcome this difficulty, this paper proposes a new magnetic bearing structure with moving frames and suspensions. The structure enables to decrease a rotor eccentricity, and a risk of contacting touchdown bearings with fixed frames is reduced. The paper shows the experimental results to verify the system.

抄録全体を表示

A linear motor that uses a finite length Halbach array as its magnetic field causes a thrust force ripple owing to end effects. In this paper, the theoretical and numerical analysis methods of the Halbach array are investigated. The results of the electromagnetic field analysis are compared to confirm the validity of the theoretical and numerical solutions. Moreover, we focus on the magnetic pole period and coil arrangement of the finite length Halbach field type linear motor to eliminate the influence of the end effects, and report the relationship with the end effects.

抄録全体を表示

Motor torque ripples generally produce a problem of noise and vibration. The torque ripple could be caused by an offset in the current sensor output. This paper presents that a current sensor offset leads to the 1^st order harmonic component of the torque ripple to the electric angle. Moreover, the current sensor offset canceller is proposed as a countermeasure against the 1^st order harmonic component. In the offset canceller, the offset value is evaluated from the 1^st order harmonic components of the ripples of d, q axes currents through Fourier series integration. Then, the remote monitoring system for the current sensors can use the proposed offset canceller. The experimental and simulational results prove the efficiency of the offset canceller.

抄録全体を表示

This paper deals with the acoustic power minimization problem from the viewpoint of an active noise and vibration control. This paper places a particular emphasis on the phenomenon in which the acoustic power output of the control source under optimal conditions always becomes zero. It is found that the acoustic radiation impedance at and around the control point source becomes reactive under the optimal condition, and hence power output of the control source results in null. It is also shown that the reactive acoustic intensity dominates even in the vicinity of the primary source in order to impede the sound radiation from its source. In active vibration control, the power flow in terms of a control force, applied directly to a vibrating structure in an effort to attenuate the radiated sound is found to be zero. Under the optimal condition for minimizing the total acoustic radiation power, the effect of the reactive sound field outweighs that of the active sound field significantly over the vibrating plate.

抄録全体を表示

Electromagnetic suspension (EMS) has been widely used in many industrial fields because of various advantages in practical use. The U-type magnets are often used to generate the levitation force in the EMS system. This conventional electromagnet, however, can only control one degree-offreedom. It cannot construct a levitation system solely by itself.
A 4-pole type yoke hybrid electromagnet is proposed instead of the usual U-type magnet and its magnetic levitation control is studied in this paper. The basic structure and characteristics of the proposed magnet are described first. Next the control system is designed. Luenberger observer, only using gap sensors, is applied to realize zero-power control. The semi-zero-power control with a disturbance observer is proposed to improve the performance, as well as the robustness, of the control system. Finally, the simulation results and corresponding experiments have been presented.

抄録全体を表示

Energy saving control is desirable for magnetically levitated (MAGLEV) vehicles. Hybrid magnets controlled with a zero power control system can reduce the exciting power. However, this conventional system requires a feed bipolar current, and the excitation system becomes complicated. To achieve a simple excitation system, a hybrid magnet with permanent magnets and divided cores was developed. The magnet was a salient-pole type magnet, and the poles were placed in two rows. Each iron core pole was equipped with a coil to control both the levitation force and lateral damping force. The coils of one side of the divided core were excited with a direct current driver to produce the same polarity as the permanent magnet 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, whereas 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 could start levitating from both upper and lower touch-down positions. In this paper, the characteristics of the proposed excitation system are presented.

抄録全体を表示

EMS has the problem that if sufficiently controlled, the unintentional vibration occurs by disturbance. And it has been known the vibration changes with the value of the feedback gain. This study focuses on this phenomenon. The conventional method moved the targeted value of the gap and moved the mover. This method, however, does not fluctuate the target value of the gap and can produce variable vibration including frequency and the amplitude directly. The experimental result shows that gap gain can change the vibration frequency of the target.

抄録全体を表示

This paper presents results of magnet characteristic analysis of a concentration type hybrid surface magnetic motor by using the finite element method. This motor has a structure combined neodymium magnets and ferrite magnets. We investigated optimal thickness of the magnets and their effectiveness.

抄録全体を表示

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.

抄録全体を表示