| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
We have developed a series of software analyzing stability and steady forced response of a rotor levitated by active magnetic bearings. According to the numerical analysis, we recognize that the system stability changes suddenly at a threshold when changing control gains of the magnetic bearings. In parallel to the software development, we have completed a small magnetic bearing-rotor testing device. The control parameter of this experimental device is changed so that the rotor is gradually brought close to an unstable region from a stable area, and then stability margin indexes (a maximum gain of sensitivity function, a maximum singular value of sensitivity function, a gain margin, a phase margin, a damping ratio, stability margin distance ) are measured to classify the control system in 4 zones; zone A in which the system is sufficiently stable, zone B which is a long-term continuous-running feasible region, zone C in which machines normally considered unsatisfactory for long term co
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ntinuous operation, and zone D in which machines are normally considered to cause damage. Moreover, also in the experiment, when controller gain is changed, it becomes clear that a stability margin becomes small and approaches occurrence zone of unstable vibration generating rapidly from a certain gain value. When the analytical result is compared with the experimental result, the difference between two results is observed in the stability limit. The cause of the difference is considered from both sides of the analyzing method and the experiment.
In the analysis, it is corrected so that internal damping of the rotating shaft which will govern system stability can be evaluated correctly. Moreover, in respect of the experiment, the sensitivity function matrix of 4×4 dimensions is measured, and the maximum singular value of the sensitivity function matrix is calculated. As a result, we confirm that calculation process of the maximum singular value of sensitivity function matrix is complicated and the maximum gain of sensitivity function maximum, the phase margin, and the gain margin change in same manner according to change of the system stability. Therefore we confirmed that the AMB system stability can be estimated by using easy estimation methods such as the maximum gain of sensitivity function matrix, the phase margin, and the gain margin instead of usage of the complicated maximum singular value of the sensitivity function matrix.
"The magnetic bearing guidebook for rotating machine designers (in Japanese)" was translated into English and published (Touka Syobou/Japan Publications Trading Co., Ltd.). Furthermore, a part of the guidebook were adopted as the Japanese proposal of ISO/TC108 (vibration and impact)/SC2 (vibration of a machine)/WG7(magnetic bearing) Part 4 (magnetic bearing design guideline). Less
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