The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
And Alexander Angerhofer - One of the best experts on this subject based on the ideXlab platform.
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Radial Position controlled doping of cds zns core shell nanocrystals surface effects and Position dependent properties
Chemistry: A European Journal, 2009Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the Radial Position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals. This paper reports a study of the surface effects and Position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (ΦET) and the efficiency of the emission from the Mn ion (ΦMn). Third, ΦMn strongly depends on the Radial Position of Mn ions in the doped core/shell nanocrystals. The Position-dependent changes of ΦMn nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the ΦMn, the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that ΦET depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Forster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.
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Radial-Position-Controlled Doping in CdS/ZnS Core/Shell Nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
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Radial Position controlled doping in cds zns core shell nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
Yongan Yang - One of the best experts on this subject based on the ideXlab platform.
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Radial Position controlled doping of cds zns core shell nanocrystals surface effects and Position dependent properties
Chemistry: A European Journal, 2009Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the Radial Position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals. This paper reports a study of the surface effects and Position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (ΦET) and the efficiency of the emission from the Mn ion (ΦMn). Third, ΦMn strongly depends on the Radial Position of Mn ions in the doped core/shell nanocrystals. The Position-dependent changes of ΦMn nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the ΦMn, the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that ΦET depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Forster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.
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Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties
Chemistry: A European Journal, 2009Co-Authors: Yongan Yang, Ou Chen, Alexander AngerhoferAbstract:Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the Radial Position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals. This paper reports a study of the surface effects and Position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (ΦET) and the efficiency of the emission from the Mn ion (ΦMn). Third, ΦMn strongly depends on the Radial Position of Mn ions in the doped core/shell nanocrystals. The Position-dependent changes of ΦMn nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the ΦMn, the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that ΦET depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Forster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.
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Radial-Position-Controlled Doping in CdS/ZnS Core/Shell Nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
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Radial Position controlled doping in cds zns core shell nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
Ou Chen - One of the best experts on this subject based on the ideXlab platform.
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Radial Position controlled doping of cds zns core shell nanocrystals surface effects and Position dependent properties
Chemistry: A European Journal, 2009Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the Radial Position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals. This paper reports a study of the surface effects and Position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (ΦET) and the efficiency of the emission from the Mn ion (ΦMn). Third, ΦMn strongly depends on the Radial Position of Mn ions in the doped core/shell nanocrystals. The Position-dependent changes of ΦMn nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the ΦMn, the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that ΦET depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Forster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.
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Radial‐Position‐Controlled Doping of CdS/ZnS Core/Shell Nanocrystals: Surface Effects and Position‐Dependent Properties
Chemistry: A European Journal, 2009Co-Authors: Yongan Yang, Ou Chen, Alexander AngerhoferAbstract:Energy transfer in doped semiconductor nanocrystals: Mn-doped CdS/ZnS nanocrystals show interesting photoluminescence and EPR properties that are strongly dependent on the Radial Position of Mn dopants inside nanocrystals (see graphic). Furthermore, the results suggest a two-step mechanism for the energy transfer inside the doped nanocrystals. This paper reports a study of the surface effects and Position-dependent properties of Mn-doped CdS/ZnS core/shell nanocrystals, which were prepared by using a three-step synthesis method. The Mn-doping level of these nanocrystals was determined by a combination of electron paramagnetic resonance spectroscopy and inductively coupled plasma atomic emission spectroscopy. These nanocrystals were further characterized by using transmission electron microscopy and fluorescence spectroscopy. First, we found that injecting a large excess of zinc stearate at the end of nanocrystal synthesis can sufficiently eliminate the surface-trap states from the doped CdS/ZnS core/shell nanocrystals and enhance their photoluminescence (PL) quantum yield (QY). Second, our results demonstrate that the Mn-PL QY is determined by the product of the efficiency of energy transfer from an exciton inside the CdS core to a Mn ion (ΦET) and the efficiency of the emission from the Mn ion (ΦMn). Third, ΦMn strongly depends on the Radial Position of Mn ions in the doped core/shell nanocrystals. The Position-dependent changes of ΦMn nearly perfectly correlate to those of the linewidth of Mn EPR peaks: the higher the ΦMn, the narrower the linewidth of the Mn EPR peak. Fourth, the results demonstrate that ΦET depends on the Mn-doping level as well as the inverse sixth power of the distance between a Mn ion and the center of its host nanocrystal. Accordingly, we propose a two-step mechanism for the energy transfer: 1) the energy transfer from an exciton inside the CdS core to a bound exciton around a Mn center, which is the rate-determining step and follows the Forster mechanism, and 2) the energy transfer from the bound exciton to the Mn center, which might follow a mechanism such as dark exciton (triplet exciton) or Auger transfer.
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Radial-Position-Controlled Doping in CdS/ZnS Core/Shell Nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
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Radial Position controlled doping in cds zns core shell nanocrystals
Journal of the American Chemical Society, 2006Co-Authors: Yongan Yang, Ou Chen, And Alexander AngerhoferAbstract:In this paper, we report a new doping approach using a three-step synthesis to make high-quality Mn-doped CdS/ZnS core/shell nanocrystals. This approach allows precise control of the Mn Radial Position and doping level in the core/shell nanocrystals. On the basis of this synthetic advance, we have demonstrated the first example in which optical properties of Mn-doped nanocrystals strongly depend on Mn Radial Positions inside the nanocrystals. In addition, we have synthesized nanocrystals with a room-temperature Mn-emission quantum yield of 56%, which is nearly twice as high as that of the best Mn-doped nanocrystals reported previously. Nanocrystals with such a high-emission quantum yield are very important to applications such as nanocrystal-based biomedical diagnosis.
Wensheng Yang - One of the best experts on this subject based on the ideXlab platform.
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bandgap and Radial Position dependent mn doped zn cu in s zns core shell nanocrystals
ChemPhysChem, 2016Co-Authors: Lucheng Peng, Keke Huang, Zhuolei Zhang, Ying Zhang, Wensheng YangAbstract:This paper presents a mechanistic study on the doping of Zn–Cu–In–S/ZnS core/shell quantum dots (QDs) with Mn by changing the Zn–Cu–In–S QD bandgap and dopant Position inside the samples (Zn–Cu–In–S core and ZnS shell). Results show that for the Mn:Zn–Cu–In–S/ZnS system, a Mn-doped emission can be obtained when the bandgap value of the QDs is larger than the energy of Mn-doped emission. Conversely, a bandgap emission is only observed for the doped system when the bandgap value of QDs is smaller than the energy gap of the Mn-doped emission. In the Zn–Cu–In–S/Mn:ZnS systems, doped QDs show dual emissions, consisting of bandgap and Mn dopant emissions, instead of one emission band when the value of the host bandgap is larger than the energy of the Mn-doped emission. These findings indicate that the emission from Mn-doped Zn–Cu–In–S/ZnS core/shell QDs depends on the bandgap of the QDs and the dopant Position inside the core/shell material. The critical bandgap of the host materials is estimated to have the same value as the energy of the Mn d–d transition. Subsequently, the mechanism of photoluminescence properties of the Mn:Zn–Cu–In–S/ZnS and Zn–Cu–In–S/Mn:ZnS core/shell QD systems is proposed. Control experiments are then carried out by preparing Mn-doped Zn(Cu)–In–S QDs with various bandgaps, and the results confirm the reliability of the suggested mechanism. Therefore, the proposed mechanism can aid the design and synthesis of novel host materials in fabricating doped QDs.
Shunsuke Kobayashi - One of the best experts on this subject based on the ideXlab platform.
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A Radial Position Control Method of Bearingless Motor Based on $d$ – $q$ -Axis Current Control
IEEE Transactions on Industry Applications, 2013Co-Authors: Shunsuke Kobayashi, M. Ooshima, M. Nasir UddinAbstract:This paper presents a Radial Position control method of bearingless motor (BELM) based on a d-q-axis current control and an integrated winding arrangement. The BELM performs the functions of a motor as well as magnetic bearing. Rotor is suspended with noncontact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the windings, the structure of BELM becomes simple, and also, the torque and force productions are increased. The d-axis stator current controls the suspension force, and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force follow the command, a compensation method is also proposed in this paper. A simulation study is done for the proposed Radial Position control based integrated winding BELM using finite-element analysis software. Furthermore, a prototype machine of the proposed BELM based on d-q-axis current control is built to confirm the performance of the motor and the magnetic suspension in real time. Rotor stabilization with magnetic levitation is confirmed using the prototype machine.
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a Radial Position control method of bearingless motor based on d q axis current control
IEEE Transactions on Industry Applications, 2013Co-Authors: Shunsuke Kobayashi, M. Ooshima, Nasir M UddinAbstract:This paper presents a Radial Position control method of bearingless motor (BELM) based on a d-q-axis current control and an integrated winding arrangement. The BELM performs the functions of a motor as well as magnetic bearing. Rotor is suspended with noncontact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the windings, the structure of BELM becomes simple, and also, the torque and force productions are increased. The d-axis stator current controls the suspension force, and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force follow the command, a compensation method is also proposed in this paper. A simulation study is done for the proposed Radial Position control based integrated winding BELM using finite-element analysis software. Furthermore, a prototype machine of the proposed BELM based on d-q-axis current control is built to confirm the performance of the motor and the magnetic suspension in real time. Rotor stabilization with magnetic levitation is confirmed using the prototype machine.
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A Radial Position control method of bearingless motor based on d-q-axis current control
IEEE Transactions on Industry Applications, 2013Co-Authors: Shunsuke Kobayashi, M. Ooshima, Md Nasir UddinAbstract:—This paper presents a Radial Position control method of bearingless motor (BELM) based on a d–q-axis current control and an integrated winding arrangement. The BELM performs the functions of a motor as well as magnetic bearing. Rotor is suspended with noncontact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the wind-ings, the structure of BELM becomes simple, and also, the torque and force productions are increased. The d-axis stator current controls the suspension force, and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force follow the command, a compensation method is also proposed in this paper. A simulation study is done for the proposed Radial Position control based integrated winding BELM using finite-element analysis software. Furthermore, a prototype machine of the proposed BELM based on d–q-axis current control is built to confirm the performance of the motor and the magnetic suspen-sion in real time. Rotor stabilization with magnetic levitation is confirmed using the prototype machine. Index Terms—Bearingless motor (BELM), d–q-axis current control, integrated winding, magnetic levitation, magnetic suspen-sion force, Radial Position control.
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a Radial Position control method of bearingless motor based on d q axis current control
IEEE Industry Applications Society Annual Meeting, 2011Co-Authors: Shunsuke Kobayashi, M. Ooshima, Nasir M UddinAbstract:This paper presents a Radial Position control method of bearingless motor (BELM) based on d-q axis current control and an integrated winding arrangement. The BELM performs the functions of motor as well as magnetic bearing. Rotor is suspended with non-contact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the windings, the structure of BELM becomes simple and also the torque and force productions are increased. The daxis stator current controls suspension force and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force to follow the command a compensation method in also proposed in this paper. A simulation study is done for the proposed Radial Position control based integrated winding BELM using finite element analysis software.
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IAS Annual Meeting - A Radial Position control method of bearingless motor based on d-q axis current control
2011 IEEE Industry Applications Society Annual Meeting, 2011Co-Authors: Shunsuke Kobayashi, M. Ooshima, M. Nasir UddinAbstract:This paper presents a Radial Position control method of bearingless motor (BELM) based on d-q axis current control and an integrated winding arrangement. The BELM performs the functions of motor as well as magnetic bearing. Rotor is suspended with non-contact by suspension force. In a conventional BELM, there are two kinds of stator windings such as motor and suspension windings. The motor winding outputs the rotational torque, and the suspension winding outputs the suspension force. To simplify the structure of conventional BELM, integration of two windings is proposed in this paper. By integrating the windings, the structure of BELM becomes simple and also the torque and force productions are increased. The daxis stator current controls suspension force and the q-axis current controls the developed torque of the motor. In the case when there is less number of slots in the machine, the actual suspension force cannot follow the command. In order to make the actual suspension force to follow the command a compensation method in also proposed in this paper. A simulation study is done for the proposed Radial Position control based integrated winding BELM using finite element analysis software.
