Abstract
Recently, magnetic bearings have been applied to many rotating machines such as turbo-molecular pumps, cooling gas compressor, flywheel energy storage systems. And high-power density is the future development trend of these machines, which demands that the rotor characterizes slender and high rotating speed and operates above the critical speeds. However, it is a big challenge for a flexible rotor to pass the bending critical speeds and operate above the critical speeds steadily and reliably. Based on above reasons, this article presented the design, modeling, and analysis framework of a flexible rotor test rig with active magnetic bearing (AMB). Special attention was paid to the flexible rotor dynamic model development, dynamic analysis, and model-based robust control design. First, the main structure features were illustrated in detail, including the key dimensions and parameters of the AMB components and rotor. Then models of components including power amplifier and displacement sensor were developed. The finite element method based on Timoshenko beam theory was applied to the rotor dynamics model. The dynamic analysis of the rotor is the foundation of the controller design. Hence, modal analysis had been done, obtaining rotor dynamic properties via synthesis of natural frequency, mode shapes, and Campbell plots. Reduced order model was obtained for controller design convenience. A robust H∞ controller was designed based on the system model and controller performance was validated with numerical simulation. The results indicate that the controller has good vibration suppression performance and makes the flexible rotor pass the first bending critical speed.
Highlights
Traditional mechanical bearings exhibit an inherent frictional loss due to the direct contact between stator and rotor, the situation worsens during high-speed rotation resulting extreme mechanical wear and tear, generation of heat, and structural failure
Rotor critical speeds under different supporting stiffness are obtained as shown in Figure 9 since the supporting stiffness is dependent on active control parameters for some degree
It is quite obvious that the designed HN controller has good vibration suppression performance for the flexible mode guaranteeing the rotor pass the first bending critical speed smoothly and stably operate
Summary
Traditional mechanical bearings exhibit an inherent frictional loss due to the direct contact between stator and rotor, the situation worsens during high-speed rotation resulting extreme mechanical wear and tear, generation of heat, and structural failure. The dampers need to occupy extra space that will add extra mass and volume of the machine Another solution to suppressing the resonance of the rotor is to design a controller with better performance making the rotor smoothly cross the bending critical speed. Mode separation method is proposed to establish the rotor mathematical model and PID controller is introduced with phase lead compensator and notch filter to successfully make the rotor pass the first bending critical speed in a magnetically suspended motor.[12] In Fang et al.[13] and Tang et al.,[14] the optimal damping and optimal phase angle are derived in detail based on the order reduced rotor model with modal truncation, and the design process of the optimal phase compensator is introduced in detail. Section ‘‘Conclusion’’ provides a summary of the work and outlines future investigations
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