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

2012 ◽  
Author(s):  
Satoshi Ueno ◽  
M. Necip Sahinkaya
Keyword(s):  
Energy Savings ◽  
Magnetic Bearing ◽  
Bias Current ◽  
Active Magnetic Bearing ◽  
Current Controller ◽  
Wide Range ◽  
Bearing Force ◽  
Variable Bias ◽  
Bearing Dynamics ◽  
Magnetic Center

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.

Improvement of Low Frequency Vibration Isolation Capability of AMB Using a Cascade PID Controller

2018 ◽  
Author(s):  
Yixin Su ◽  
Yanhui Ma ◽  
Yongpeng Gu ◽  
Suyuan Yu ◽  
Gexue Ren
Keyword(s):  
Pid Controller ◽  
Vibration Isolation ◽  
Dynamic Performance ◽  
Low Frequency ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Control Parameters ◽  
Control Loops ◽  
Low Frequency Vibration ◽  
Wide Range

In contrast with traditional mechanical bearing, Active magnetic bearing (AMB) has no friction and lubrication, and its dynamic performance can be adjusted by active control. To isolate low frequency vibration of the rotating machinery under 50Hz, a novel design of cascade PID controller (CPC) with two control loops for AMB is proposed. The main loop is a position loop and the secondary loop is a transmission force loop. According to the theoretical derivations in this study, the CPC controls both the rotor position and the transmission force. Even when the control parameters maintain constant, the dynamic characteristic parameters, equivalent stiffness and equivalent damping, vary with frequency continuously and smoothly. Therefore, they can be adjusted in a wide range to achieve isolation of low frequency vibration when using proper control parameters. A simulation example shows that the transmission force with a CPC is lower in the 8–50Hz when the rotor displacement is almost same as with a single stage PID controller (SSPC). Experimental verification was carried out in an experimental bench of AMB under unbalanced rotor condition. Results show that a CPC can reduce the vibration acceleration at 15–50Hz especially near the peaks. Simulation and experimental results well demonstrate the effectiveness and guaranteed stability of the CPC in the present study.

scholarly journals An Appraisal of Power-Minimizing Control Algorithms for Active Magnetic Bearings

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Seong-yeol Yoo ◽  
Myounggyu D. Noh
Keyword(s):  
Power Consumption ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Active Magnetic Bearing ◽  
Control Algorithms ◽  
Active Magnetic Bearings ◽  
Consistent Model ◽  
Complex Power ◽  
Derivative Type ◽  
Variable Bias

Active magnetic bearings consume much less power than conventional passive bearings, especially when power-minimizing controllers are employed. Several power-minimizing controllers have been proposed, such as variable bias controllers and switching controllers. In this paper, we present an appraisal of the power-minimizing control algorithms for active magnetic bearings in an attempt to provide an objective guideline on the merits of the control algorithms. In order for the appraisal, we develop an unified and consistent model of active magnetic bearing systems. The performances of the power-minimizing controllers are assessed through this model. The results show that the power-minimizing controllers indeed save considerable power when the machine state is relatively steady. However, a simple proportional-derivative type controller is on a par with the much more complex power-minimizing controllers in terms of power consumption when the machine is experiencing transient loads.

Adaptive Bias Current Control in Active Magnetic Bearings for Energy Optimization

2011 ◽  
Author(s):  
Satoshi Ueno ◽  
M. Necip Sahinkaya
Keyword(s):  
Power Consumption ◽  
Control Method ◽  
Optimization Method ◽  
Magnetic Bearing ◽  
Descent Method ◽  
Bias Current ◽  
Current Control ◽  
Experimental Results ◽  
Active Magnetic Bearing ◽  
Steepest Descent Method

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.

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