Satoshi Ueno

Modeling and Control of Salient-Pole Permanent Magnet Axial-Gap Self-Bearing Motor

This paper will introduce an inset-type axial-gap self-bearing motor (AGBM), which is an electrical combination of an axial thrust-bearing and an axial flux motor. A method for controlling the axial position and the rotating speed of the AGBM without the influence of reluctance torque is also discussed. First, the axial force and the motoring torque are analyzed theoretically, and then, the control method is derived. To demonstrate the proposed technique, an inset two-pole AGBM has been constructed and tested. The experimental results confirm that the motor works stably with the proposed vector control. Moreover, the rotating torque and the axial force can be controlled independently as well.

Analysis and Control of Nonsalient Permanent Magnet Axial Gap Self-Bearing Motor

This paper deals with a nonsalient permanent magnet axial gap self-bearing motor (AGBM), which is an electrical combination of an axial thrust bearing and an axial flux motor. A method for controlling the axial position and the rotating speed of the motor is also discussed. First, the development of the AGBM is briefly reviewed. The axial force and the rotating torque are then analyzed theoretically to establish an exact mathematical model for the motor. Finally, a modern control structure is derived to give the AGBM drive good dynamic behavior to make it suitable for practical application in industry. To demonstrate the proposed technique, a surface-mounted four-pole AGBM has been constructed and tested. The experimental results confirm that the motor works stably with the proposed vector control. Moreover, the AGBM can simultaneously provide noncontact levitation and rotation. This makes it an ideal replacement for conventional mechanical bearing motors in equipment used in harsh environments.

Improvement of sensorless speed control for nonsalient type axial gap self-bearing motor using sliding mode observer

This paper presents an improvement of sensorless speed vector control for a nonsalient type axial gap self bearing motor (AGBM), in which rotor speed and position are estimated by using sliding mode observer with full mathematical model. The approach is based on the estimation of the motor back-EMF (or induced voltage) through a sliding mode observer with help of reference voltages, measured stator currents and measured displacement. In order to achieve an accurate estimation of the rotor speed and position, an adaptive gain of the sliding mode controller is proposed. Experiment was implemented based on dSpace1104 with two three phase inverters. Results confirm that the sensorless drive for AGBM achieved at the average and high speed range, so further work is being continued to improve the experiment for this proposal at low speed range.

Sensorless speed control of inset type axial gap self-bearing motor using extended EMF

The goal of this paper is utilization of the state observer to research a new capability of controlling the axial gap self-bearing motor. Analytical and experimental evaluation for a sensorless speed vector control of a salient axial gap self-bearing motor is presented. The approach is based on the estimation of the extended electromotive force (EEMF) through a Luenberger Observer (LO) with help of reference voltages, measured stator currents and measured displacement. Experiment has been implemented based on dSpace1104 with two three phase inverters. The result is destined for introduction in this conference.

A novel design of a Lorentz-force-type small self-bearing motor

Although magnetic bearing motors suffer no friction loss and hence require no lubrication, they are not widely used because of their high cost and large size. To solve these problems, a self-bearing motor having a simple structure with distributed windings is proposed. The rotor consists of a permanent magnet and an iron yoke that rotates in the body. The stator consists of a six-phase distributed winding and is installed between the permanent magnet and the back yoke of the rotor. A Lorentz force, generated by the interaction between the stator current and permanent magnet field, controls the rotation speed and radial position of the rotor. In this paper, a novel design for a slotless self-bearing motor with two windings, and non-contact levitation capability, is introduced, and experimental results are shown.

Sensorless speed control of a permanent magnet type axial gap self-bearing motor using sliding mode observer

This paper presents an analytical and experimental evaluation of sensorless speed vector control of an axial gap self bearing motor, in which rotor speed and position are estimated by using Sliding mode observer. The approach is based on the estimation of the motor back-EMF (or induced voltage) through a sliding mode observer with help of measured stator currents and reference voltages. In order to achieve an accurate estimation of the rotor speed and position, an adaptive gain of sliding mode controller is proposed. In addition, during the operation of system, low pass filters are used to smooth the estimated variables. Experiment is implemented based on dSpace1104 with two three phase inverters. Results confirm that axial force and rotating torque can be controlled independently and motor can get the good performance in steady state at the average and high speed range, so further work is being continued to improve the experiment for this proposal.

Adaptive Bias Current Control in Active Magnetic Bearings for Energy Optimization

This paper introduces an adaptive bias current control method for an active magnetic bearing (AMB). The bearing force is analyzed theoretically, and the dynamic performance of the magnetic bearing for various bias currents is discussed. Then power consumption is analyzed and the optimum bias current that minimizes power consumption is derived. A novel optimization method using a steepest descent method is proposed. This requires less computing power than the former optimization method using a recursive Fourier transform algorithm. Experimental results show that the optimized bias current can be achieved by the proposed method. However, the dynamics of the rotor is affected by the bias current variation. In order to overcome this problem, the effects of parameter errors are investigated and correction methods are introduced. Experimental results show that the rotor dynamics are not affected by the variable bias current if the parameters are corrected. Results are also presented for machine run-up and run-down.

Analysis and control of radial force and tilt moment for an axial-gap self-bearing motor

This paper introduces an axial-gap self-bearing motor, which can actively control five-degrees of freedom of rotor posture. To control radial force and tilt moment, cylindrical flux paths are attached around the stator and the rotor. Three kinds of magnetic flux, namely two-pole rotating flux, four-pole rotating flux, and uniform flux for a two-pole rotor, are used. The two-pole rotating flux controls the axial force and motor torque. The radial force and tilt moment are generated by both the four-pole rotating flux and the uniform flux, and can be controlled by combining these fluxes. This paper introduces the structure, principle and analytical forces and moments of the proposed motor. Then the experimental results of radial force and tilt moment generation and levitation and rotation tests are shown.

Reducing Energy Consumption in Active Magnetic Bearings by a Nonlinear Variable Bias Controller

This paper presents a nonlinear variable bias controller for an active magnetic bearing (AMB). The nonlinear bearing force is analyzed theoretically and the control current for various bias current settings is derived from the nonlinear bearing equation. Then the power consumption is minimized to obtain the optimum bias current expression analytically. Results show that the optimum bias current can be calculated from the demand bearing force and the instantaneous rotor displacement. Moreover, the influences of magnetic bearing parameter errors are investigated and correction methods are introduced. Results of experimental rotational tests show that the rotor dynamics are not altered under variable bias currents if the proposed correction for parameter errors is implemented. The magnetic center of misalignment is also detected and compensated for. The proposed variable bias current controller provides not only significant energy savings, but also it is simple to implement and applicable to wide range of magnetic bearing systems without deterioration of the bearing dynamics.© 2012 ASME