In current bearing dynamic models, the displacement coordinate relations are usually utilized to approximately obtain the contact deformations between the rolling element and raceways, and then the nonlinear restoring forces of the rolling bearing could be calculated accordingly. Although the calculation efficiency is relatively higher, the accuracy is lower as the contact deformations should be solved through iterative analysis. Thus, an improved nonlinear dynamic model is presented in this paper. Considering the preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication, load distribution analysis is solved iteratively to more accurately obtain the contact deformations and angles between the rolling balls and raceways. The bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. Dynamic tests upon a typical rotor system supported by two angular contact ball bearings are conducted to verify the model. Through comparisons, the differences between the nonlinear dynamic model and current models are also pointed out. The effects of axial preload, rotor eccentricity and inner/outer waviness amplitudes on the dynamic response are discussed in detail.

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A prototype IGBT-based matrix converter supplying an induction motor was constructed in the lab. When the indirect space vector modulation on the matrix converter is implemented, it is found that the real voltage transfer ratio is lower than the expected one. In order to enhance the voltage transfer ratio, an adaptive modulation rate regulation method is proposed. The voltage transfer ratio can be enhanced by 9.75% using the proposed method. The disadvantage of the proposed method is also analyzed. The applicable load types are also given. Simulation results verify the theoretical analysis. More experiments results will be presented in the near future.

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