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Summary of Research on Unbalanced Vibration Control of Magnetic Levitation Rotors (1)

Release time:

2023-01-13

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On the basis of relevant research on the control of unbalanced vibration of magnetic levitation rotors, this paper elaborates on the causes, control principles, and treatment methods of unbalanced vibration of magnetic levitation rotors, discusses the control methods of unbalanced vibration based on two control strategies: small bearing electromagnetic force and small rotor vibration displacement, and introduces typical application cases of this technology in rotating machinery, The future direction of research on unbalanced vibration control of magnetic levitation rotors is prospected.

Due to design and processing defects, uneven materials, thermal deformation, and other reasons, the rotor inevitably experiences mass imbalance, resulting in centrifugal force of the same frequency as the rotor speed. This centrifugal force is proportional to the square of the rotor speed and causes the rotor to vibrate. When rotating machinery operates at high speed, small residual unbalanced masses can also have a serious impact on the system. According to relevant statistics, about one-third of the faults in rotating machinery come from rotor imbalance. Therefore, the dynamic balance and unbalanced vibration control technology of rotors are of great significance for high-speed rotating machinery.

Traditional structural bearings, when used as supports, do not have active control characteristics. The rotor supported by them can only undergo offline dynamic balancing before actual operation, and there is still residual imbalance after dynamic balancing. When the imbalance situation of the rotor changes due to load changes or rust, dynamic balancing will fail. The stiffness of magnetic bearings is relatively small compared to traditional structural bearings and the suspension air gap is large. When the rotor imbalance force is large, the rotor vibration will be more severe; However, the control parameters and current of the magnetic bearing are adjustable, making it capable of real-time active control, providing the possibility for controlling the unbalanced vibration of the rotor.

Based on extensive literature research, this article discusses the development, research status, algorithm classification, and other aspects of unbalanced vibration control for magnetic levitation rotors, and proposes possible future research directions.

1. Introduction to Magnetic Suspension Rotor System

The magnetic levitation flexible rotor system is a typical electromechanical integration system, including a controller, D/A conversion module, power amplifier, rotor, stator, eddy current displacement sensor, and A/D conversion module. The typical structure of the magnetic levitation rotor system is shown in Figure 1. The principle of the closed-loop control system of the magnetic levitation rotor is shown in Figure 2: the eddy current displacement sensor detects the deviation e of the rotor relative to the reference position r, and after A/D conversion, it is input as a digital quantity to the controller. The controller outputs the control signal u through corresponding control algorithm operation, and after D/A conversion, it is input to the power amplifier. The power amplifier generates the control current i and stabilizes the rotor in the balanced position.

2. Unbalance control method for magnetic levitation rotor

At present, there are two control strategies for unbalanced vibration of magnetic levitation rotors: small bearing electromagnetic force control and small rotor displacement control.

Low electromagnetic force control of bearings, also known as Auto Balance, involves filtering out the imbalance in the feedback displacement signal through a certain filtering algorithm, reducing the amplitude of the same frequency component of the imbalance in the control current to weaken the active control effect of the magnetic bearing, thereby making the rotor rotate as much as possible around its inertia axis. At this time, the imbalance control force of the rotor is small. By controlling the unbalanced force of the rotor, it can freely rotate around the inertia axis, reducing the unbalanced force while eliminating it