Journal of System Vol. 7, No. 2, 2013 Design and Dynamics 【Review Paper】 Reviews of Magnetic Bearing Development in Japan*
Naohiko TAKAHASHI** **Turbomachinery R&D Center, Infrastructure System Company, Hitachi, Ltd. 603 Kandatsu-machi, Tsuchiura-shi Ibaraki, Japan E-mail: [email protected]
Abstract In the 1980s, active magnetic bearings attracted attention because of their benefits that include contact-free support, no lubrication and low energy consumption, and their industrial applications were extensively studied. In the 1990s, the latest control theories were applied to magnetic bearings, and bearingless drive technologies were established. Magnetic bearings were increasingly applied to industrial machinery and started to find use in artificial hearts. The number of researchers engaged in research on magnetic bearings rapidly increased in Japan, and many achievements were reported. Currently, however, less research is being carried out. In this article, Japan’s contribution to the research and development of magnetic bearings is reviewed, particularly key works in the early days of magnetic bearings, from various aspects such as control, rotordynamics, self-sensing, bearingless drives, bearing loss, touchdown bearings, industrial applications, and standardization.
Key words: Magnetic Bearing, Control, Rotordynamics, Self-Sensing, Bearingless Drive, Bearing Loss, Touchdown Bearing, Turbo Molecular Pump, Spindle, Compressor, Blower, Pump, Turbine, Electric Motor, Flywheel
1. Introduction
The progress of magnetic bearings in Japan would be reviewed for publication in this issue entitled Reviews of Japan’s Rotordynamics Development. Currently, research on magnetic bearings is no longer popular in Japan. This is because magnetic bearing technologies are already mature, and the industries that require magnetic bearings have not significantly grown in Japan. However, Japan has greatly contributed to the establishment of basic technologies for magnetic bearings. This review should provide a good opportunity to recognize the achievements of Japanese researchers. Research on magnetic bearings is mainly reported in the Transactions of the Japan Society of Mechanical Engineers (in Japanese) and the International Symposium on Magnetic Bearings (ISMB) (in English). Therefore, most of the research on magnetic bearings in Japan can be found in these publications. Meanwhile, online services for searching for academic articles have recently become available. Anyone can easily search for academic articles on magnetic bearings using the Scholarly and Academic Information Navigator (CiNii) provided by the National Institute of Informatics (NII). In this article, the research activities on magnetic bearings in Japan are reviewed referring to the above-mentioned two publications and using the search system of CiNii. Through this approach, the postwar Japanese achievements in magnetic bearings will be clarified. Although Japan has significantly contributed to the *Received 23 Jan., 2013 (No. R-13-0023) [DOI: 10.1299/jsdd.7.111] international standardization of magnetic bearings, this is rarely indicated in the literature. Copyright © 2013 by JSME The Japanese activity for standardization is also reviewed. It is hoped that by recognizing
111 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics Japan’s contribution to magnetic bearings, the research and development of magnetic bearings will again become popular in Japan.
2. General Description
Magnetic bearings have two types of operation; one uses the repulsive force of magnets and the other uses the attraction force. Moreover, some use permanent magnets and others use electromagnets. Repulsive-type magnetic bearings using permanent magnets can essentially stabilize an object in the levitation direction; however, an object cannot be stably levitated solely by permanent magnets, as shown by Earnshaw’s theorem(1). Magnetic bearings using electromagnets are generally based on the attraction-type operation, which is essentially unstable and requires some control. To support a rotating shaft using electromagnets, a total of five axes, i.e., four axes in the radial direction and one axis in the axial direction, must be controlled. This review focuses on active magnetic bearings using electromagnets. In Japan, some societies have carried out extensive activities on magnetic bearings through their committees and have published related books as follows. The results of a four-year survey have been reported by the Magnetic Levitation Technical Committee of the Institute of Electrical Engineers of Japan (Chairperson, Fumio Matsumura)(2). An introduction to magnetic bearings has been published by the Technical Section for the Dynamics and Control of Magnetic Bearings of the Japan Society of Mechanical Engineers (Chairman, Yohji Okada)(3). A practical guide for designers of rotating machines has been published by the Technical Section for the Standardization of Active Magnetic Bearings of the Japan Society of Mechanical Engineers (Chairman, Osami Matsushita; Editor and Author, Yoichi Kanemitsu)(4). Several books on magnetic bearings written by Japanese researchers have also been published overseas; Chiba and his colleagues, who study bearingless drives, wrote a book on the basics of bearingless drives(5). Okada has outlined bearingless motors in a book on magnetic bearing technologies edited by Schweitzer and Maslen, which focuses on rotating machinery (6). Japan has also played a major role in running the ISMB. This symposium was established in 1988 and is held every two years, usually in Switzerland, Japan, and the USA in this order. Thus far, the symposium has been held four times in Japan: Tokyo in 1990 (Chairperson, Toshiro Higuchi), Kanazawa in 1996 (Chairperson, Matsumura), Mito in 2002 (Chairperson, Okada), and Nara in 2008 (Chairpersons, Kenzo Nonami and Takeshi Mizuno). As research on magnetic bearings has recently become popular in China, the 2010 symposium was held in China. Figure 1 shows the number of academic articles written by Japanese researchers on magnetic bearings for each year over approximately the last 60 years, obtained by entering “jiki jikuuke” (magnetic bearing in English) as a keyword in CiNii. In 1937, Holmes at Virginia University demonstrated, for the first time in the world, that magnetic levitation can be realized by automatically changing the strength of a magnetic field(7). Approximately 10 years later, the first study on magnetic bearings carried out in Japan was reported. The report concerned magnetic bearings used for high-speed rotation and was written by Arakatsu et al. at the Institute for Chemical Research, Kyoto University, and submitted to the Nihon Butsuri Gakkaishi (Butsuri), a Japanese journal published by the Physical Society of Japan, in 1948(8). In the 1950s, ultracentrifuges for biochemistry were intensively studied in Japan. Magnetic bearings were highly expected for them to have low friction. In 1952, Mimura and Taniguchi at Tokyo Institute of Technology reported their study on magnetic bearings(9). In 1960, the Central Research Laboratory, Hitachi, Ltd., developed a magnetically supported prototype free-running equilibrium type ultracentrifuge(10). In the 1960s and 1970s, a group led by Sasaki, Mori, Okino, and
112 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics Watanabe at Kyoto University and a group led by Taniguchi and Shimizu at Tokyo Institute of Technology intensively studied magnetic bearings(11)(12)(13). In France, the company Société Mécanique Magnétique (S2M), which specializes in the design and manufacture of magnetic bearings, was founded in 1976. In the 1980s, research on magnetic bearings became active and the number of related articles increased yearly. In particular, there were many reports from Higuchi and Mizuno at the University of Tokyo, Matsumura and Fujita at Kanazawa University, and Murakami and Nakajima at the National Aerospace Laboratory of Japan. During this period, magnetic bearings used for turbomolecular pumps, machine tool spindles, and flywheels of spacecraft(14)(15) were actively developed and commercialized. The commercialization of magnetic bearings was further expanded in the 1990s. An increasing number of researchers studied magnetic bearings and presented many reports; magnetic bearing research in Japan was led by the groups of Okada at Ibaraki University and Nonami at Chiba University in addition to the above-mentioned groups. In this period, robust control theories including H∞ control were intensively studied, and fast digital-signal processing systems became readily available. The use of magnetic bearings has become popular for demonstrating these new control theories. Basic bearingless drive technologies were also established in this period and were frequently reported by the groups of Fukao at Tokyo Institute of Technology and Chiba at Science University of Tokyo (currently at Tokyo Institute of Technology) as well as the above-mentioned group led by Okada. Moreover, magnetic levitation technologies started to be applied to blood pumps. In the 2000s, the demand for industrial machinery using magnetic bearings grew less than expected, with the exception of medical applications and some small applied products. In contrast, intensive activity was observed overseas towards the establishment of future industries using magnetic bearings. For example, compressor manufacturers competitively developed machines supported by magnetic bearings for use in subsea gas fields by integrating high-speed motors and centrifugal compressors. In the 2010s, the scale of research on magnetic bearings rapidly shrunk in Japan, although many reports on bearingless drives and applications to artificial hearts have been presented. If the keyword “bearingless motor” is also used in a search, the number of articles may appear to be increasing, although the general decrease in the amount of activity remains unchanged.
60 50 40 30 20 10 Number of publications of Number 0 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year Fig. 1 Number of publications on magnetic bearing
3. Control
Magnetic bearings generally require control systems. From the late 1980s to the early 1990s, power electronics and digital signal processing technologies rapidly progressed as hardware technologies used to realize such control systems, activating research on the application of magnetic bearings. In this period, software technologies for control systems
113 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics also made marked progress. Control theories required for magnetic bearings are roughly classified into two types: unbalanced vibration control used to suppress vibration and robust control with high stiffness used to realize stable levitation. S2M invented two key control methods that can suppress the unbalanced vibration of rotors supported by magnetic bearings(16)(17). One is unbalance force rejection control (UFRC), which S2M has long called the automatic balancing system (ABS). In UFRC, which eliminates the rotational speed component from the magnetic force of magnetic bearings, a rotor rotates around the principal axis of inertia. Hence, the vibration of the rotor is suppressed and the transmission of the unbalanced force to the bearing stator is blocked, resulting in silent operation. The other is “peak-of-gain” control (also known as unbalance force counteracting control). This enhances the rotational speed component of the magnetic force and increases the stiffness of bearings and thereby suppresses the vibration of the rotor. Peak-of-gain control is used when high-accuracy rotation, such as for machine tool spindles, is required. Related research has been reported by many Japanese researchers as listed below. Mizuno et al. constructed an observer to estimate the unbalanced force and proposed a method of canceling the unbalanced force using the output from the observer(18). Oshima et al. realized the rotation of a spindle used for vacuum equipment around the principal axis of inertia using a notch filter(19). Matsushita et al. proposed an N-cross control method that applies antisymmetric cross-feedback to the synchronous rotational speed components(20). Their method uses the idea that the antisymmetric cross-feedback is equivalent to a phase lead of 90°. Kanemitsu et al. reported the results obtained using the force generated by magnetic bearings for balancing(21), which is a type of feedforward control. Higuchi et al. presented results for the compensation of imbalance by periodic control(22). Miyaji et al. applied adaptive vibration control (AVC), which suppresses unbalanced vibration in a feedforward manner, to a prototype centrifugal compressor equivalent to an actual compressor(23). Rotating shafts supported by magnetic bearings are generally classified as flexible structure, which require the consideration of the elastic mode. The control of magnetic bearings has a common feature with that of the head of hard discs since both are flexible structure. Controlling the elastic mode is important to realize stable levitation. The control of levitation by magnetic bearings has frequently adopted classic control theories such as proportional-integral-derivative (PID) control and phase compensation control, and the stabilization of the elastic mode was a difficult challenge. Rather than adopting conventional approaches based on such classic control theories, a movement occurred towards improving control performance by applying the latest control theories to magnetic bearings. Japanese researchers played a significant role in this movement. In the 1980s, the application of modern control theories to rigid rotors was examined; for example, linear quadratic (LQ) control with integral action(24) and antisymmetric cross-feedback for the gyroscopic system(25) were proposed. In the 1990s, computer-aided design (CAD) for control theories became widespread and the capability of processing digital signals was improved, thus providing the environment for demonstrating cutting-edge control theories. The control systems for magnetic bearings were an attractive research topic for control researchers, and studies on the control of magnetic bearings, including the control of the elastic mode, spread into various fields. Fujita et al. promptly started tackling robust control, particularly H∞ theory and µ analysis and synthesis using structured singular values, and applied these control methods to magnetic levitation systems(26)(27). Nonami et al. energetically studied the application of various control theories to magnetic bearings, such as H∞ control(28) and µ synthesis(29)(30), as well as the linear matrix inequality (LMI)-based design of control systems(31) and nonlinear control including the backstepping control(32), sliding mode control(33), and nonlinear zero power control(34). While new control theories are being examined, conventional control methods, such as PID control and
114 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics phase compensation control, are still currently used in many commercial applications. The required performance can be obtained even using conventional control methods by combining several types of filter, which needs the most sophisticated integration. Such integration of filters was reported as early as 1985(19), in the initial days of magnetic bearings. Katayama et al. successfully stabilized the elastic mode using a stabilizing filter(35). The author’s group also stabilized the elastic mode and suppressed the unbalanced vibration by integrating a phase shifting filter and another filter to synchronize the rotational speed in a turbo compressor with magnetic bearings(36). Currently, even the trial-and-error design of control systems requires less effort than before because of the progress of CAD. Characteristic rotordynamic phenomena frequently occur in magnetic bearing systems because their control objects are rotors. The most characteristic phenomenon is considered to be the gyroscopic effect. Unstable whirls may occur in control systems designed without considering the gyroscopic effect. An approach to the gyroscopic effect based on modern control theories was reported in Ref. (25). In Ref. (20), the control structures required to control a system destabilized by the gyroscopic effect were discussed from the viewpoint of rotordynamics, and stabilization by antisymmetric cross-feedback for the backward whirl was proposed.
4. Rotordynamics
The design of control systems for magnetic bearings is closely related to rotordynamics, as described above, and some studies on magnetic bearings focusing on rotordynamics have been reported. For example, Ito et al. attempted to exceed higher-order critical speeds and exceeded the third bending critical speed(37). Kanemitsu et al. attempted to identify mass unbalance and sensor runout(38). The author’s group analyzed the thermal bending vibration occurring in systems supported by magnetic bearings(39). Well-known similar phenomena are the Newkirk effect caused by contact heat and the Morton effect caused by heat generated from the oil film in lubricated bearings. In magnetic bearing systems, iron loss generated in the rotation core causes thermal bending. Researchers have attempted to use magnetic bearings in the research and development of rotordynamics. Wagner et al. were the first to report such an attempt and proposed a device to measure the dynamic properties of gas seals using magnetic bearings in 1988(40). In 2000, Ebara Research Co., Ltd., (Japan) developed a system for measuring the fluid reaction force using magnetic bearings(41), and they measured the fluid reaction force for pump seals, bearings, and impellers. For centrifugal compressors, a test in which the stability of shaft-bearing systems is measured by attaching a magnetic bearing to the end of a shaft as an exciter has generally been carried out. Hitachi Plant Technologies, Ltd., (Japan) reported test results for a high-pressure centrifugal compressor(42).
5. Self-Sensing
In general, active magnetic bearings require displacement sensors to detect the position of rotating shafts. If the position of rotating shafts can be detected without displacement sensors, cost-effective and compact systems can be realized. Self-sensing magnetic bearings do not require any independent displacement sensors because of the incorporation of a sensing function into their electromagnets used to generate a magnetic attractive force. There are two types of self-sensing magnetic bearing: one uses a back electromotive force induced in a bearing coil, and the other uses the superimposition of a high-frequency signal to a bearing coil. In the former method, proposed by Vischer and co-workers at Eidgenössische Technische Hochschule Zürich (ETH)(43)(44), the coil current is measured
115 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics using a voltage-output power amplifier. This method enables self-sensing because the observability of a system is ensured merely by observing the coil current instead of the shaft displacement. In Japan, Mizuno et al. studied the practical application of this method(45). The latter method(46) has been studied for much longer than the former method and uses the relationship between the inductance of electromagnets and the bearing gap. High-frequency signals are required to measure the inductance of electromagnets. Okada et al. developed a self-sensing method using the ripple components from a pulse width modulation (PWM) power amplifier without using any special high-frequency generator circuits(47). Self-sensing has also been reported in some review articles(48)(49).
6. Bearingless Drive (or Self-Bearing Motor)
Bearingless drives are used to give a magnetic bearing function to electric motors at the time of torque generation. Hermann, a German researcher, applied for patents for this idea in 1973-1975 and presented the theoretical basics of bearingless drives(50)(51). In 1985, Higuchi, a Japanese researcher, proposed a stepping motor with a magnetic bearing function(52). In 1989, Chiba and Fukao proposed an electric rotating machinery with radial position control windings and its controller for various types of electric motor and power generator on the basis of field-oriented theory(53). They applied their bearingless drive theory to a reluctance motor(54). Bichsel, a Swiss researcher, carried out similar research in his doctoral course at ETH and compiled his study results on bearingless permanent magnet synchronous motors in his doctoral thesis in 1990(55). Subsequently, Okada et al. clarified the relationship between the number of poles and the levitation force for permanent magnet synchronous motors(56). In the 1990s, theoretical systems for bearingless drives were established on the basis of vector control theories, to which Chiba et al. greatly contributed(57). According to a review article written by Chiba and Fukao in 2001, the number of articles on bearingless drives has markedly increased since 1995(58). As of 2001, the cumulative number of such articles produced in Japan was much higher than that in other countries. Currently, the research and development of bearingless drives is still mainly being carried out by groups at Tokyo Institute of Technology, Tokyo University of Science, Suwa, and Ibaraki University. Although there is still no business prospect of the industrial application of bearingless drives, Ebara Corporation in Japan has developed a bearingless canned pump using an interior permanent magnet (IPM) motor with an output of 3.2 kW and a rotational speed of 12000 rpm(59). Moreover, magnetically supported pumps used for artificial hearts are being studied, mainly by researchers at Ibaraki University, for which promising results are expected(60).
7. Bearing Loss
Magnetic bearings are known to have very low loss; however, even the low loss must be accurately evaluated when they are used in flywheels. The evaluation of loss is also important in cooling design, which is essential for high-speed rotating machinery. For magnetic bearings, iron loss (hysteresis and eddy current losses) and windage loss lead to rotational loss. Joule heat generated from coils and cables leads to power loss. Japanese researchers started studying the losses of magnetic bearings relatively early, although the number of reports they produced is limited. In 1985, Oshima et al. measured the rotational loss of magnetic bearings used in milling and derived empirical formulae(19). Higuchi et al., Matsumura et al., and Ueyama et al. also experimentally evaluated the losses of magnetic bearings(61)-(63). In 1992, Matsumura and Hatake applied a Fourier transform to an arrangement of magnetic poles and clarified the relationship between the magnetic pole
116 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics arrangement and magnetic loss(64). Regarding the reduction of loss, in 2003, Une et al. reported a low-loss magnetic bearing, obtained by applying zero power control to a homopolar magnetic bearing, for use in flywheels for power storage(65). In 2006, Maruyama et al. proposed a heteropolar magnetic bearing with markedly reduced eddy current loss for use in high-speed cutting devices(66).
8. Touchdown Bearing (, Backup Bearing or Auxiliary Bearing)
Auxiliary bearings are a key element of magnetic bearing systems; however, the number of studies on them in Japan is limited. Auxiliary bearings are mostly ball bearings, although bushings are sometimes used. For large machinery, Mitsubishi Heavy Industries, Ltd., reported the results of touchdown tests on a turbo heat pump that applied magnetic bearings(67). Similarly, the results of touchdown tests on centrifugal compressors equipped with magnetic bearings were reported by Hitachi, Ltd., Kobe Steel, Ltd., and Mitsubishi Heavy Industries, Ltd(68)-(70). Ohura et al. evaluated the load applied to the auxiliary bearings of turbomolecular pumps through tests and analysis and summarized the points to be examined to determine the specifications of auxiliary bearings(71). At universities, Ishida, Inoue et al. constructed a model considering the contact and friction of auxiliary bearings and experimentally examined the validity of the model(72)(73).
9. Industrial Applications
The industrial applications of magnetic bearings were fully examined in the 1980s, the background to which can be found in review articles written at that time(74)(75). The first industrial application of magnetic bearings was in turbomolecular pumps. A clean vacuum without oil contamination can be obtained using magnetic bearings, which require no lubrication. S2M, established in 1976, was among the first to develop a practical turbomolecular pump. In the 1980s, Japanese companies including Osaka Vacuum, Ltd.(76), NTN Toyo Bearing Co., Ltd.(19), Koyo Seiko Co., Ltd.(77), Shimadzu Corporation(78), Seiko Seiki Co., Ltd.(79), Ebara Corporation(80), and Mitsubishi Heavy Industries, Ltd.,(81) also developed turbomolecular pumps with magnetic bearings. The divisions of Seiko Seiki Co., Ltd., and Mitsubishi Heavy Industries, Ltd., responsible for turbomolecular pumps have now been transferred to Edwards Limited and Shimadzu Corporation, respectively, and the domestic manufacturers of turbomolecular pumps are currently Shimadzu Corporation, Osaka Vacuum, Ltd., and Ebara Corporation. In addition to turbomolecular pumps, various other industrial machines that applied magnetic bearings were developed in Japan; however, their commercialization was unsuccessful. Turbomolecular pumps are a rare successful application of magnetic bearings, which are still being used in them. S2M was also the first to start the manufacture and sale of machine tool spindles using magnetic bearings. Since the circumferential speed of machines using magnetic bearings is higher than that of machines using ball bearings, higher-output motors with larger-diameter shafts can be constructed. In 1984, S2M established Japan Magnetic Bearings Co., Ltd., as a joint venture with Seiko Instruments & Electronics, Ltd., to start manufacturing and selling machine tool spindles with magnetic bearings in Japan. The Japanese company NSK, Ltd., released prototype magnetic bearings with a rotational speed of 70000 rpm and an allowable radial load of 392 N for use in machine tools in 1979(82). In 1984, NTN Toyo Bearing Co., Ltd., released a high-speed milling spindle with a rotational speed of 40000 rpm and a maximum allowable load of 600 N (both radial and thrust)(19).
117 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics In the 1990s, magnetic bearings were applied to other industrial machines. Attempts to apply magnetic bearings to various industrial machines were also made in Japan as follows. Hitachi, Ltd., designed net gas booster compressors used in a continuous catalytic regeneration-platforming process using magnetic bearings and supplied them to Okinawa(68). Generally, process centrifugal compressors are designed so that the operational rotational speed does not exceed the second critical speed; however, the compressors supported by magnetic bearings achieved high-speed rotation exceeding the third critical speed. Mitsubishi Heavy Industries, Ltd., and Kobe Steel, Ltd., also developed centrifugal compressors with magnetic bearings(83)(69). In 2010, Mitsubishi Heavy Industries, Ltd., supplied booster compressors with magnetic bearings to Russia for use in pipelines(70). Recently, subsea compressors, which inevitably require magnetic bearings, have been intensively developed worldwide(84). However, Japanese manufacturers have not yet participated in their development. In 2004, Kawasaki Heavy Industries, Ltd., completed the development of an aeration blower with magnetic bearings comprising all its original components. At present, its sales are steadily increasing(85). Oil-free blowers using foil air bearings are also commercially available and have been intensively developed by Korean manufacturers. In the field of air conditioning and refrigeration systems, Mitsubishi Heavy Industries, Ltd., developed a turbo heat pump applying magnetic bearings in 1991(67), which is a completely oil-free machine operated with a gearless drive. In 2005, the company released a system in which magnetic bearings are applied to a one-shaft turbo machine comprising an expansion turbine, a compressor, and a built-in motor with the aim of developing an air-cycle ultralow-temperature refrigeration system(86). The use of magnetic bearings enables the realization of clean systems that can be safely used in the food industry. Magnetic bearings are also suitable for turbo machines in systems for cooling superconductors because these systems are required to be maintenance-free and reliable for a long term. In 1991, IHI Corporation developed a helium centrifugal compressor with magnetic bearings(87). In 1999, the company received an order of helium refrigerators to be used in accelerators made by Conseil Europeen pour la Recherche Nucleaire (CERN), and they supplied cold compressors with magnetic bearings(88)(89). Recently, Taiyo Nippon Sanso Corporation has developed a neon turbo-expander and centrifugal compressor, both with magnetic bearings(90)(91). Water turbines using magnetic bearings were first developed in 1985 by Nippon Koei Co., Ltd., and first applied to practical machines in 1993(92). Thanks to magnetic bearings, maintenance-free hydroelectric systems have been realized that do not contaminate rivers with oil. Flywheels must have low loss and high circumferential speed, and therefore require magnetic bearings. The ultimate goal is to realize superconducting power storage using flywheels. Various institutions including Shikoku Research Institute Inc., IHI Corporation, and International Superconductivity Technology Center (ISTEC) were commissioned by the New Energy and Industrial Technology Development Organization (NEDO) in 2000 and studied to achieve this goal. Since 2005, the research and development of such flywheels has mainly been carried out by Central Japan Railway Company(93). Normal-conduction flywheels used for uninterruptible power sources have been developed and commercialized by IHI Corporation(94). An application of magnetic bearings to high-temperature operations is a high-temperature blower for fuel cells, which was developed by Ebara Corporation in 1991(95). The blower treats cathode exhaust gas at 700 °C, and its magnetic bearings are heated to 350-400 °C. Hence, highly temperature-resistant electric materials were adopted. In 2004, a canned motor pump that can operate at a high temperature of 425 °C and a high pressure of 20.5 MPa was developed(96). In this pump, not only the motor but
118 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics also its magnetic bearings have a canned structure that can endure high temperatures and pressures. Other industrial machines with magnetic bearings developed in Japan include liquid natural gas (LNG) pumps, helium gas turbines of high-temperature gas-cooled reactors, and high-speed motors(97)-(99). As another application of magnetic bearings, Akamatsu et al. of Japan developed a magnetically suspended centrifugal blood pump in cooperation with NTN Corporation ahead of researchers in other countries(100). In the pump, the tilt of the impeller and the axial direction are actively controlled, and the remaining degrees of freedom are passively controlled using the restoring force induced by magnetic coupling. The pump was practically used by Terumo Corporation and set a record for the longest continuous operation of 864 days in an in vivo experiment started in 1996(101). A group led by Shinshi at Tokyo Institute of Technology and Takatani at Tokyo Medical and Dental University developed a magnetically levitated blood pump in which the radial direction of the impeller is actively controlled and the remaining degrees of freedom are passively controlled. In 2010, they reported the results of a two-month in vivo experiment obtained using a magnetically levitated disposable blood pump that was installed outside the body(102). A group led by Masuzawa at Ibaraki University has also developed a blood pump and examined the application of self-bearing motors to blood pumps(103).
10. Standardization
Japanese researchers have significantly contributed to the standardization of magnetic bearing technologies. In the mid 1990s, Matsushita (then National Defense Academy), Kanemitsu (then Ebara Research Co., Ltd.), and Azuma (then Ishikawajima Noise Control Co., Ltd.) initiated activities toward the international standardization of magnetic bearing technologies on the basis of the idea that technological standardization is required to increase the range of uses of magnetic bearings. In 1996, they encouraged the International Organization for Standardization (ISO) to establish a working group (TC108/SC2/WG7), in which Matsushita served as a convener. Japan played a leading role in WG7 and formulated four standards as follows. First, ISO 14839-1 concerns the vocabulary of active magnetic bearings(104)(105), which was later attempted to be formulated in Japanese Industrial Standards (JIS). ISO 14839-2 concerns the evaluation of vibration and was formulated on the basis of a conclusion that the American Petroleum Institute Standard API617(106) is inadequate for application to centrifugal compressors with magnetic bearings(107)(108). Table 1 summarizes the zone limits for vibrational displacement specified in ISO 14839-2. Zones A, B, C, and D represent the vibrations of newly commissioned machines, vibrations normally considered acceptable for unrestricted long-term operation, vibrations normally considered unsatisfactory for long-term continuous operation, and vibrations normally considered to be sufficiently severe to cause damage to the machine, respectively. ISO 14839-3 concerns the evaluation of the stability margin(109). Although sensitivity functions were proposed for use as stability indices, there was a long-lasting discussion before their formulation. Japan carried out open experiments with the support of NEDO to encourage a final decision on formulation(110)(111). Table 2 summarizes the finally determined zone limits for the sensitivity function. ISO 14839-4 concerns technical guidelines(112) and was formulated by a project team led by Saito (IHI Corporation). The guidelines include condition monitoring, system requirements, touchdown tests, and preventive maintenance. Currently, a fifth standard is being prepared by Keogh (University of Bath), the present convener of WG7.
119 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics Table 1 Recommended criteria of zone limits
Zone limit Displacement Dmin
A/B <0.3 Cmin
B/C <0.4 Cmin
C/D <0.5 Cmin
NOTE Cmin is the minimum value of radial axial clearance between rotor and stator.
Table 2 Peak sensitivity at zone limits Zone Peak sensitivity Level Factor A/B 9.5 dB 3 B/C 12 dB 4 C/D 14 dB 5
11. Conclusion
Although previous works on magnetic bearings have been reviewed, fields outside the specialty of the author may have been insufficiently covered. Through this work, it has been rediscovered that almost all the basic technologies of magnetic bearings required for their practical application had been established by the 1980s or early 1990s, to which Japan significantly contributed. However, magnetic bearings have only been successfully applied to industry in limited fields, as described in some previous review articles. Although their high manufacturing cost has long been considered to hinder the spread of magnetic bearings, the expansion of the market as a result of cost reduction is thought to be limited. Magnetic bearings will only be used in industry for applications whose systems cannot be constructed without magnetic bearings or for applications whose performance will be markedly improved using them. Looking overseas, MECOS AG and Synchrony Inc., both of which were engaged exclusively in the manufacture of magnetic bearings, were acquired by MAN Diesel & Turbo and Dresser Rand, respectively. They are likely to monopolize the market for products using magnetic bearings in the oil-, gas-, and environment-related fields. Currently, Japan is facing a crisis in which the knowledge and expertise on magnetic bearings accumulated in the 1980s and 1990s is not being disseminated but is being lost. To preserve the assets built up by the time and effort of earlier researchers, it is necessary to form industry-academic consortia and construct an industrial system with a global viewpoint.
References
(1) Earnshaw, S., On the Nature of the Molecular Forces Which Regulate the Constitution of the Luminiferous Ether, Transactions Cambridge. Philosophical Society, Vol.7, Part I (1842), pp.97–112. (2) The Magnetic Levitation Technical Committee of the Institute of Electrical Engineers of Japan, Magnetic Suspension Technology – Magnetic Levitation Systems and Magnetic Bearings –, (1993), Corona Publishing, Japan. (3) The Japan Society of Mechanical Engineers, Basic and Application of Magnetic Bearings, (1995), Yokendo, Japan (in Japanese). (4) Azuma, T., Kanemitsu, Y., Takahashi, N., Fukushima, Y., Matsushita, O., Magnetic Bearing Guidebook for Rotating Machine Designers, (2004), Japan Industrial Publishing, Japan (in Japanese), (2006), Toukashobo, Japan. (5) Chiba, A., Fukao, T., Ichikawa, O., Oshima, M.,Takemono, M., Dorrell, D., Magnetic Bearings and Bearingless Drives, (2004), Newnes, Burlington.
120 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics (6) Bleuler, H., Cole, M., Keogh, P., Larsonneur, R., Maslen, E., Nordmann, R., Okada, Y., Schweitzer, G., Traxler, A., Magnetic Bearings Theory, Design, and Application to Rotating Machinery, (2009), Springer-Verlag. (7) Holmes, F. T., Axial Magnetic Suspensions, Review of Scientific Instruments, Vol.8, (1937), pp.444–447. (8) Arakatsu, B., Sakamoto, H., Katase, A., Kokame, J., Yano, S., On the Magnetic Suspension Mechanism for Research of High Speed Rotation, Nihon Butsuri Gakkaishi, Vol.3, No.1–2 (1948), pp.55–56 (in Japanese). (9) Mimura, S., Taniguchi, O., The Principle and Experiments of Magnetic Bearings, Science of Machine, Vol.4, No.6 (1952), pp.349–352 (in Japanese). (10) Goto, Y., Miyazawa, Y., Sudo T., The Free-Running Type Equilibrium Ultracentrifuge, Journal of the Japan Society of Mechanical Engineers, Vol.63, No.502 (1960), pp.1452–1460. (11) Mori, H., Kaneko, R., Takagi, A., A Study on a Controlled Magnetic Bearing (1st Report), Journal of Japan Society of Lubrication Engineers, Vol.10, No.6 (1965), pp.509–515. (12) Sasaki, T., Okino, N., Koakutsu, Y., Watanabe, T., A Study on the Electro-Magnetically Controlled Bearing, Transactions of the Japan Society of Mechanical Engineers, Vol.33, No.247 (1967), pp.484–493. (13) Shimizu, H., Taniguchi, O., Magnetic Bearing, Journal of Japan Society of Lubrication Engineers, Vol.14, No.4 (1969), pp.189–194. (14) Murakami, C., Magnetic Bearing Flywheel for Attitude Control of Spacecraft, Journal of Society of Instrument and Control Engineers, Vol.23, No.1 (1984), pp.129–134 (in Japanese). (15) Nakajima, A., Research and Development of Magnetic Bearing Flywheel for Attitude Control of Spacecraft, Proceedings of the 1st International Symposium on Magnetic Bearings, Zürich, (1988), pp.3–12. (16) Habermann, H., Brunet, M., “Device for Compensation Synchronous Disturbances in the Magnetic Suspension of Rotor”, United States Patent 4121143 (1978). (17) Habermann, H., Brunet, M., “Device for Damping the Critical Frequencies of a Rotor Suspended by a Radial Electromagnetic Bearing”, United States Patent 4128795 (1978). (18) Mizuno, T., Higuchi, T., Compensation for Unbalance in Magnetic Bearing Systems, Transactions of the Society of Instrument and Control Engineers, Vol.20, No.12 (1984), pp.1095–1101. (19) Oshima, S., Nakazeki, T., Nanami, S., Ozaki, T., Magnetic Bearing Spindles, Bearing Engineer, No.51 (1985), pp.55–63 (in Japanese) (20) Matsushita, O., Takagi, M., Tsumaki, N., Yoneyama, M., Sugaya, T., Bleuler, H., Flexible Rotor Analysis Combined with Active Magnetic Bearing Control, Proceedings of the IFToMM 2nd International Conference on Rotordynamics, Tokyo, (1986), pp.421–427. (21) Kanemitsu, Y., Ohsawa, M., Watanabe, K., Real Time Balancing of a Flexible Rotor Supported by Magnetic Bearing, Proceedings of the 2nd International Symposium on Magnetic Bearings, Tokyo, (1990), pp.265–272. (22) Higuchi, T., Mizuno, T., Otsuka, M., Compensation for Mass Imbalance Using Periodic Learning Control Method, Transactions of the Institute of Systems, Control and Information Engineers, Vol.3, No.5 (1990), pp.147–153. (23) Miyaji, T., Sanari, H., Baba, Y., Hope, R.W., Tessier, L.P., Knospe, C.R., Vibration Control by Magnetic Bearing System (The Application of Adaptive Vibration Control to Industrial Turbomachinery), Turbomachinery, Vol.28, No.3 (2000), pp.149–155 (24) Matsumura, F., Kobayashi, H., Akiyama, Y., Fundamental Equation of Horizontal Shaft Magnetic Bearing and its Control System Design, The Institute of Electrical Engineers of Japan Transactions on Electronics, Information and Systems, Vol.101, No.6 (1981), pp.137–144. (25) Higuchi, T., Mizuno, T., Control Systems Design for Totally Active DC-Type Magnetic Bearings – Structure of the Optimal Regulator for Systems with Gyroscopic Couplings, Transactions of the Society of Instrument and Control Engineers, Vol.18, No.5 (1982),
121 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics pp.507–513. (26) Matsumura, F., Fujita, M., Shimizu, M., Robust Stabilization of Magnetic Suspension System Using H∞ Control Theory, The Institute of Electrical Engineers of Japan Transactions on Industry Applications, Vol.110, No.10 (1990), pp.1051–1057. (27) Fujita, M., Matsumura, F., Namerikawa, T., µ Analysis and Synthesis of a Flexible Beam Magnetic Suspension System, Proceedings of the 3rd International Symposium on Magnetic Bearings, Virginia, (1992), pp.495–504. (28) Cui, W., Nonami, K., H∞ Control of Flexible Rotor-Magnetic Bearing Systems, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.58, No.553 (1992), pp.2650–2656. (29) Ito, T., Nonami, K., µ Synthesis of Flexible Rotor-Magnetic Bearing System, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.61, No.584 (1995), pp.1437–1442. (30) Nonami, K., Ide, N., Ueyama, H., Robust Control of Magnetic Bearing Systems Using µ Synthesis with Descriptor Form, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.63, No.606 (1997), pp.457–463. (31) Nonami, K., Sivrioglu, S., Ueyama, H., Active Magnetic Bearing System by means of
LMI-Based H∞ Control and Mixed H2/H∞ Control, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.62, No.600 (1996), pp.3159–3167. (32) Sakai, K, Nonami, K., Ariga, Y., Low Consumption Nonlinear Control of Magnetic Bearing System by Means of Backstepping Procedure, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.67, No.664 (2001), pp.3744–3749. (33) Nonami, K., Yamaguchi, H., Y., Robust Control of Magnetic Bearing Systems by Means of Sliding Mode Control, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.58, No.545 (1992), pp.106–111. (34) Ariga, Y., Nonami, K., Sakai, K., Experimental Consideration of Zero Power Magnetic Bearing Supported by Nonlinear Controller, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.67, No.664 (2001), pp.3750–3757. (35) Katayama, K., Kawada, N., Morii, S., Tokiyasu, K., Ikeda, Y., Itai, K., Development of Totally Active Magnetic Bearings, Mitsubishi Heavy Industry Review, Vol.25, No.3 (1988), pp.274–279. (36) Takahashi, N., Miura, H., Fukushima, H., Design and Test Results of Active Magnetic Bearing Control System for High-Speed Turbo Compressor, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.72, No.721 (2006), pp.2912–2920. (37) Ito, M., Fujiwara, HJ., Matsushita, O., Q-value Evaluation and Rotational Test of Flexible Rotor Supported by AMBs, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.74, No.745 (2008), pp.2190–2197. (38) Kanemitsu, Y., Kijimoto, S., Matsuda, K., Park, T., Identification of Mass Unbalance and Sensor Runout on a Rigid Rotor Equipped with Magnetic Bearings, Proceedings of the 7th International Symposium on Magnetic Bearings, Zürich, (2000), pp.543–548. (39) Takahashi, N., Kaneko, S., Thermal Instability in a Magnetically Levitated Doubly Overhung Rotor, Journal of Sound and Vibration, Vol.332, No.5 (2013), pp.1188–1203. (40) Wagner, N. G., Pietruszka, W. D., Identification of Rotordynamic Parameters on a Test Stand with Active Magnetic Bearings, Proceedings of the 1st International Symposium on Magnetic Bearings, Zürich, (1988), pp.289–299. (41) Eguchi, M., Maruta, Y., Kaneko, T., Development of Seal Dynamics Measurement System for Active Magnetic Bearings, Ebara Engineering Review, No.189 (2000), pp.3–12. (42) Takahashi, N., Magara, Y., Narita, M., Miura, H., Rotordynamic Evaluation of Centrifugal Compressor Using Magnetic Exciter, Transaction of the ASME Journal of Engineering for Gas Turbines Power, Vol.134, No.3 (2012), pp.032505.1–032505.7. (43) Vischer, D., Sensorlose und Spannungsgesteuerte Magnetlager, Doctor Thesis ETH Zürich, Nr. 8665 (1988).
122 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics (44) Vischer, D., Bleuler, H., Self-Sensing Active Magnetic Levitation, IEEE Transaction on Magnetics, Vol.29, No.2 (1993), pp.1276-1281. (45) Mizuno, T., Bleuler, H., Tanaka, H., Hashimoto, H., Harashima, F., Ueyama, H., An Industrial Application of Position Sensorless Active Magnetic Bearings, The Institute of Electrical Engineers of Japan Transactions on Industry Applications, Vol.116, No.1 (1996), pp.35-41. (46) Frazier, R. H., Gilinson, P. J., Oberbeck, G. A., Magnetic and Electric Suspensions, (1974), pp.265-284, The MIT Press. (47) Okada, Y., Matsuda, K., Nagai, B., Sensorless Magnetic Levitation Control by Measuring PWM Carrier Frequency Component, Proceedings of the 3rd International Symposium on Magnetic Bearings, Virginia, (1992), pp.176-183. (48) Mizuno, T., Sensorless Magnetic Suspension, Journal of Society of Instrument and Control Engineers, Vol.38, No.2 (1999), pp.92–96. (49) Investigating R&D Committee on State-of-the-Art Technologies of High-Speed Drives and Bearingless Drives, State-of-the-Art Technologies of High-Speed Drives and Bearingless Drives, the Institute of Electrical Engineers of Japan Technical Report, No.1058 (2006), pp.30–33. (50) Hermann, P. K., A Radial Active Magnetic Bearing, London Patent No. 1478868, 20 November (1973). (51) Hermann, P. K., A Radial Active Magnetic Bearing Having a Rotating Drive”, London Patent No. 1500809, 9 February (1974). (52) Higuchi, T., Magnetically Floating Actuator Having Angular Positioning Function, United States Patent No. 4683391, 12 March (1985). (53) Chiba, A, Fukao, T., Electric Rotating Machinery with Radial Position Control Windings and its Rotor Radial Position Controller, Japan Patent No. 2835522, 18 January (1989). (54) Chiba, A., Rahman, M. A., Fukao, T., Radial Force in a Bearingless Reluctance Motor, IEEE Transaction on Magnetics, Vol.27, No.2 (1991), pp.786-792. (55) J. Bichsel, Beiträge zum lagerlosen Elektromotor, ETH Thesis, No. 9303 (1990). (56) Okada, Y.,Ohishi, T., Dejima, K., Levitation Control of Permanent Magnet (PM) Type Rotating Motor, Proceedings of the Magnetic Bearings, Magnetic Drives and Dry Gas Seals Conference & Exhibitions, Alexandria, (1992), pp.157–165. (57) Chiba, A., Deido, T., Fukao, T., Rahman, M. A., An Analysis of Bearingless AC Motors, IEEE Transaction on Energy Conversion, Vol.9, No.1 (1994), pp.61–68. (58) Chiba, A., Fukao, T., The State of the Art in Development of Bearingless Drives, The Institute of Electrical Engineers of Japan Transactions on Industry Applications, Vol.121, No.7 (2001), pp.724–729. (59) Sato, T., Kato, H., Development of Canned Pump having Efficiency Self-levitation Motors, Turbomachinery, Vol.34, No.7 (2006), pp.389-394. (60) Masuzawa, T., Kita, T., Okada, Y., An Ultradurable and Compact Rotary Blood Pump with a Magnetically Suspended Impeller in the Radial Direction, Artificial Organs, Vol.25, No.5 (2001), pp.395–399. (61) Higuchi, T., Mizuno, T., Miyake, S., Experimental Study of Rotational Loss in Magnetic Bearings, Proceedings of the 1986 Spring Annual Meeting of the Japan Society for Precision Engineering, (1986), pp.53–54. (62) Matsumura, F., Fujita, M., Ozaki, Y., Characteristics of Friction on Magnetic Bearings, The Institute of Electrical Engineers of Japan Transactions on Industry Applications, Vol.108, No.5 (1988), pp.462–468. (63) Ueyama, H., Fujimoto, Y., Iron Losses and Windy Losses of High Speed Rotation Speed Rotor Suspended by Magnetic Bearings, Proceedings of the 2nd International Symposium on Magnetic Bearings, Tokyo, (1990), pp.237–242. (64) Matsumura, F., Hatake, K., Relation Between Magnetic Pole Arrangement and Magnetic Loss in Magnetic Bearings, Proceedings of the 3rd International Symposium on Magnetic
123 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics Bearings, Virginia, (1992), pp.274–283. (65) Une, S., Saito, O., Kurihara, K, Ariga, Y., Development of Active Magnetic Bearing of Low Energy Loss, Turbomachinery, Vol.31, No.12 (2003), pp.734–738. (66) Maruyama, T., Nakagawa, T., Tashiro, I., A Study on Magnetic Bearing Spindle for Achieving a High DN Value: A Proposal of Bearing Structure for High Stiffness and Low Eddy Current Loss, Journal of the Japan Society for Precision Engineering, Vol.72, No.8 (2006), pp.994–1000. (67) Kanki, H., Yamashita, K., Kishimoto, A., Seki, W., Miyazawa, K., Kusunoki, T., Matsumura, F., Development of High Efficiency Centrifugal Heat Pump Applying Active Magnetic Bearings, Mitsubishi Heavy Industry Review, Vol.28, No.4 (1991), pp.415–419. (68) Fukushima, Y., Hiroshima, M., Takahashi, N., Yoneyama, M., The Centrifugal Compressor Equipped with Magnetic Bearing, Turbomachinery, Vol.24, No.3 (1996), pp.157–162. (69) Sanari, H., Miyachi, T.,Baba, Y., Kurohashi, M., The Application of Digital Control Magnetic Bearing to a Centrifugal Compressor, Turbomachinery, Vol.26, No.10 (1998), pp.624–631. (70) Tokuyama, S., Akiyama, M., Yamamoto, M., Kita, M., Reliable Design Approach of Magnetic Bearing Application for Compressor, Proceedings of the 15th International Symposium “Compressor Users-Manufacturers,” St Petersburg State Polytechnic University, (2010). (71) Ohura, Y., Ueda, K., Sugita, S., Performance of Touchdown Bearings for Turbo Molecular Pumps, Proceedings of the 8th International Symposium on Magnetic Bearing, Mito, (1998), pp.515–520. (72) Ishida, Y., Inoue, T., Masaki, K., Vibration Analysis of an Active Magnetic Bearing Backup Bearing-Rotor System: Vibration Characteristics for the Various Fault Patterns of an Active Magnetic Bearing, Transactions of the Japan Society of Mechanical Engineers, Series C, Vol.69, No.683 (2003), pp.1741–1748. (73) Inoue, T., Mizuho, I., Inoue, J., Hayakawa, M., Ishida, Vibration Analysis of the Magnetic Bearing-Backup Bearing-Rotor System: Effect of the Backup Bearing on the Dynamical Characteristics of the Rotor System During Deceleration Through the Major Critical Speed, Proceedings of the Japan Society of Mechanical Engineers Dynamics & Design Conference, (2002), pp.648.1–648.6. (74) Shimizu, H., The Principle of Magnetic Bearings and Their Applications, Journal of the Vacuum Society of Japan, Vol.26, No.9 (1983), pp.705–710. (75) Matsumura, F., Current Status and Applications of Magnetic Bearing, Science of Machine, Vol.39, No.1 (1987), pp.31–36 (in Japanese) (76) Kaneto, S., Nagakubo, M., Iguchi, M., Ikegami, T., Oikawa, H., Development of New Molecular Pump (II), Journal of the Vacuum Society of Japan, Vol.27, No.5 (1984), pp.425–428. (77) Fujimoto, Y., Matsushima, T., Nakaura, S., Kyotani, H., Development of Totally Active Magnetic Bearings, KOYO Engineering Journal, No.128 (1985), pp.7–12. (78) Narita, K., Kawaguchi, J., Ashida, O., Fujimoto, Y., Development of Wide Pressure Range Turbo-Molecular Pump with Active Magnetic Bearing, Shimadzu Review, Vol.43, No.4 (1986), pp.297–306. (79) Ishizawa T., Miki, M, Urano, C., Kawashima, T., Yamamoto, M., Masubuchi, N, Characteristic of a Magnetic Suspension Type Turbo Molecular Pump of High Flow Rate, Journal of the Vacuum Society of Japan, Vol.30, No.5 (1987), pp.230–232. (80) Yoshioka, J., Murai, Y., Shimizu, N., Turbo-Molecular Pump, Eabara Engineering Review, No.138 (1987), pp.2–6. (81) Itai, K., Yamada, J., Katayama, K., Morii,S., Kawada, N., Development of Active Magnetic Bearing Type Turbomolecular Pump for Wide Vacuum Range, Mitsubishi Heavy Industry Review, Vol.26, No.5 (1989), pp.430–433. (82) Magnetic Bearings Close to Industrial Applications, Nikkei Mechanical, Vol.72, No.721 (1979), pp.32–37 (in Japanese).
124 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics (83) Morii,S., Kawada, N., Tokiyasu, K., Fujimura, M, Kawashima, Y., Development of Oilless Centrifugal Compressor, Mitsubishi Heavy Industry Review, Vol.28, No.6 (1991), pp.614–617. (84) Ryu, K., Arita, Y., Coudray, Y., Improving Reliability Through Non-Contact Bearing: Magnetic Bearing, Turbomachinery, Vol.37, No.10 (2009), pp.612–616. (85) Nishimura, T., Kinoshita, Y., Kujime, Y., Shindo, Y., Matsuo, K., Kuroda, M., Hashimoto, K., Nakashima, K., Sawada, M., Pursuit of Energy-Savings in “Kawasaki MAG-Turbo” Aeration Blower, K. H. I. Technical Review, No.167 (2008), pp.16–21. (86) Kikuchi, S., Okuda, S., Igawa, H., Morii, S., Mitsuhashi M., Higashimori, H., Development of Air Cycle System for Refrigeration, Mitsubishi Heavy Industry Review, Vol.42, No.4 (2005). (87) Asakura, H., Kato, D., Saji, N., Ohya, H., 80 K Centrifugal Compressor for Helium Refrigeration System, Proceedings of the 1991 Cryogenic Engineering Conference, Huntsville, AL, (1991). (88) Saji, N., Yoshinaga, S., Asakura, T., Shinba T., H., Honda, Mori, M., Technologies of 1.8 K / 2.4 kW Helium Refrigerators and Cold Compressors for LHC, Journal of the Cryogenic Society of Japan, Vol.40, No.9 (2005), pp.372–376. (89) Ueyama, H., Helium Cold Compressor with Active Magnetic Bearing, Proceedings of the 7th International Symposium on Magnetic Bearings, Zürich, (2000). (90) Hirai, H., Hirokawa, M., Takaike, A., Development of a Neon Turbo-Expander with Active Magnetic Bearings, Taiyo Nippon Sanso Technical Report, No.28 (2009). (91) Hirai, H., Hirokawa, M., Takaike, A., Ozaki, S., Development of a Small Turbo-Compressor with Active Magnetic Bearings, Taiyo Nippon Sanso Technical Report, No.29 (2010). (92) Hayashi, H., Application of Magnetic Bearing for Water Turbine and Generator, Journal of the Japan Society of Mechanical Engineers, 38(2), 112–114, 1999 (in Japanese) (93) Kiyono, H, Yonezu, T., , Superconducting Magnetic Energy Storage, Railway Research Review, Vol.66, No.3 (2009), pp.26–29. (94) Saitou, O., Kuwata, G., Nukumi, H., Iwasaki I., Majima, T., Development of Mechanical Secondary Battery (Flywheel Rechargeable Battery), Journal of IHI Technologies, Vol.49, No.1 (2009), pp.54–59. (95) Sakai, J., Tsuchiya, N., Miyasaka, M., Ishikawa, K., Yoshida, K., Osawa, M., Furuya, T., Ninomiya, H., Development of High-Temperature Blower for Molten Carbonate Fuel Cell, Ebara Engineering Review, No.153 (1991), pp.8–17. (96) Honda, S., Kato, H., Sato, T., Ohtake, K., High Speed Canned Motor Pump for High Temperature and High Pressure Liquid Using Magnet Bearings, Turbomachinery, Vol.32, No.1 (2004), pp.45–50. (97) Kobayashi, F., Osawa, M., Yoshida, K., High-Speed Submerged Motor Pump with Magnetic Bearings for Liquefied Gas Transportation, Ebara Engineering Review, No.153 (1991), pp.32–39. (98) Takada, S., Takatsuka, T., Xing, Y., Kunitomi, K., Helium Gas Turbine of High Temperature Gas Cooled Reactor, Journal of the Gas Turbine Society of Japan, Vol.34, No.2 (2006), pp.12–17. (99) TMEIC North America Site Library “Brochures: TMEIC Industrial Motors Overview” (online), available from
125 Journal of System Vol. 7, No. 2, 2013 Design and Dynamics Vivo Evaluation of Biocompatibility in LVAD Condition, Proceedings of the 18th Congress of the International Society for Rotary Blood Pumps, Berlin, Germany, (2010), pp.67 (103) Masuzawa, T., Onuma, J., Kim, S., Okada, Y., Magnetically Suspended Centrifugal Blood Pump with a Self-Bearing Motor, Journal of the American Society of Artificial Internal Organs, Vol.48, No.4 (2002), pp.437–442. (104) Kanemitsu, Y., Matsushita, O., Azuma, T., Ishida, S., Iwatsubo, T., Ueyama, H., Ohsawa, M., Ota, M., Okada, Y., Kazao, Y., Kadoya, Y., Kanki, H., Kozaki, J., Singu, S., Takahashi, N., Tanaka, M., Hara, S., Hatano, K., Higuchi, T., Fukushima, Y., Matsumura, F., Japanese Proposal for International Standardization for Active Magnetic Bearing, Proceedings of the 5th International Symposium on Magnetic Bearings, Kanazawa, (1996), pp.265–270. (105) International Organization for Standardization, Mechanical Vibration – Vibration of Rotating Machinery Equipped with Active Magnetic Bearings - Part 1: Vocabulary, (2002), International Standard ISO14839-1. (106) American Petroleum Institute, Centrifugal Compressors for Petroleum, Chemical and Gas Service Industries, (1995), API Standard 617, 6th Edition. (107) Matsushita, O., Kanemitsu, Y., Azuma, T., and Fukushima, Y., Vibration Criteria Considered from Case Studies of Active Magnetic Bearing Equipped Rotating Machines, International Journal of Rotating Machinery, Vol.6, No.1 (2000), pp.67–78. (108) International Organization for Standardization, Mechanical Vibration – Vibration of Rotating Machinery Equipped with Active Magnetic Bearings - Part 2: Evaluation of Vibration, (2004), International Standard ISO14839-2. (109) International Organization for Standardization, Mechanical Vibration – Vibration of Rotating Machinery Equipped with Active Magnetic Bearings - Part 3: Evaluation of Stability Margin, (2006), International Standard ISO 14839-3. (110) Matsushita, O., Kanemitsu, Y., Ito, M., Takahashi, N., Maslen, E.H., Markert, R., Hawkins, L.A., Bornstein, K.R., ISO International Standardization Project on Magnetic Bearing Technology, FY2005 Proceedings of the International Joint Research Grant Program (NEDO Grant) Conference, (2005), pp.7–17. (111) Takahashi, N., Fujiwara, H., Matsushita, O., Ito, M., Fukushima, Y., An evaluation of stability indices using sensitivity functions for active magnetic bearing supported high-speed rotor, Transaction of the ASME Journal of Vibration and Acoustics, Vol.129, No.2 (2007), pp.230–238 (112) International Organization for Standardization, Mechanical Vibration – Vibration of Rotating Machinery Equipped with Active Magnetic Bearings - Part 4: Technical Guidelines, (2012), International Standard ISO 14839-4.
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