A Review of Research on Unbalanced Vibration Control of Magnetic Suspension Rotors

Based on the relevant research on the unbalanced vibration control of the magnetic suspension rotor, the causes, control principles and treatment methods of the unbalanced vibration of the magnetic suspension rotor are expounded. The vibration control method is introduced, and the typical application cases of this technology in rotating machinery are introduced. Finally, the future direction of research on unbalanced vibration control of magnetically suspended rotors is prospected. Due to design and processing defects, uneven material, thermal deformation and other reasons, the rotor inevitably has mass imbalance, which will generate centrifugal force with the same frequency as the rotation speed, which is proportional to the square of the rotor rotation speed and causes the rotor to vibrate. When rotating machinery is running at high speed, a small residual unbalanced mass can also have a serious impact on the system. According to relevant statistics, about one-third of rotating machinery failures come from rotor unbalance. Therefore, rotor dynamic balance and unbalanced vibration control technology are of great significance to high-speed rotating machinery. The traditional structural bearing does not have active control characteristics when it is used as a support. The rotor supported by it can only be dynamically balanced off-line before the actual operation, and there is still a residual unbalance after the rotor is dynamically balanced. Dynamic balancing will fail when the resulting imbalance changes. Compared with the traditional structure bearing, the stiffness of the magnetic bearing is smaller and the suspension air gap is larger. When the unbalanced force of the rotor is larger, the rotor vibration will be more severe; however, the control parameters and control current of the magnetic bearing are adjustable, so that it has real-time active control ability to provide the possibility to control the unbalanced vibration of the rotor. Based on a large number of literature surveys, this paper discusses the development, research status, and algorithm classification of unbalanced vibration control of magnetic levitation rotors, and proposes possible future research directions. 1. Introduction to the magnetic suspension rotor system The magnetic suspension flexible rotor system is a typical mechatronics system, including a controller, a D/A conversion module, a power amplifier, a rotor, a stator, an eddy current displacement sensor and an A/D conversion module, a typical magnetic suspension rotor The system structure is shown in Figure 1. The principle of the closed-loop control system of the magnetic suspension rotor is shown in Figure 2: The eddy current displacement sensor detects the offset e of the rotor relative to the reference position r, and after A/D conversion, it is input to the controller as a digital quantity, and the controller passes through the corresponding control algorithm. The operation output control signal u is input to the power amplifier after D/A conversion, and the power amplifier generates the control current i and stabilizes the rotor in the equilibrium position. 1—non-driving end radial magnetic bearing; 2—exciting magnetic bearing; 3—disc; 4—rotating shaft; 5—driving end radial magnetic bearing; 6—motor; 7—displacement sensor. Fig.1 Typical magnetic suspension rotor system structureFig.1 Typical magnetic suspension rotor system structureFig.2 Schematic diagram of magnetic suspension rotor control systemFig.2 Principle of magnetic suspension rotor control system2, magnetic suspension rotor unbalance control method At present, the magnetic suspension rotor imbalance vibration control strategy There are two types of bearing electromagnetic force minimum control and rotor displacement minimum control. The minimum control of the bearing electromagnetic force is also called automatic balance, that is, the unbalanced amount in the feedback displacement signal is filtered out through a certain filtering algorithm, and the amplitude of the unbalanced and same-frequency component in the control current is reduced to weaken the active force of the magnetic bearing. control, so that the rotor rotates around its main axis of inertia as much as possible, and the unbalanced control force of the rotor is minimal at this time. By controlling the unbalanced force of the rotor, it can freely rotate around the main axis of inertia, reducing the unbalanced force and eliminating the same-frequency vibration force transmitted to the support foundation. Effective use of the unbalanced force control algorithm to reduce the co-frequency vibration force of the rotor is of great significance to improving the performance and reliability of the magnetic bearing system and reducing the power consumption of the magnetic bearing. The minimum control of rotor displacement is also called Unbalance Compensation, that is to increase the control current through certain measures or compensation algorithms, thereby enhancing the active control effect of the magnetic bearing, increasing the dynamic stiffness of the system, and making the rotor as much as possible around its magnetic bearing stator The geometric center of the rotor rotates to achieve the purpose of reducing the displacement and vibration of the rotor. At this time, the vibration displacement of the rotor is the smallest. Using the unbalanced displacement control algorithm to reduce the unbalanced displacement of the rotor is of great significance to increase the dynamic stiffness of the magnetic bearing and improve the output accuracy of the system. The purpose and effect achieved by the above two kinds of vibration compensation are opposite, that is to say, the minimum inertia force and the minimum displacement cannot be achieved at the same time in the active magnetic bearing system.