Active Magnetic Bearing Systems and Control Techniques

Active Magnetic Bearing (AMB) systems employ electromagnetic forces to levitate and stabilise rotating machinery without physical contact, thereby eliminating frictional losses and wear. These systems feature radial and axial actuators coupled with high-precision position sensors and power amplifiers, which together form a closed-loop control architecture. The principal challenge lies in the inherently nonlinear dynamics of the levitated rotor and the need to maintain stability across a wide range of speeds and loads. Control strategies span from classical proportional–integral–derivative schemes to advanced robust and adaptive algorithms, aiming to suppress unbalance, attenuate resonances, and optimise stiffness and damping characteristics. Recent breakthroughs in measurement techniques and model-based controllers have enhanced the dynamic performance and reliability of AMBs in applications such as high-speed turbines, vacuum pumps, and flywheel energy storage, underscoring their global significance in precision engineering.

Research from Nature Portfolio

Recent studies have revealed that the stiffness parameters of radial AMBs, traditionally treated as constants, vary significantly with operational speed. A novel analytical framework combined an equivalent magnetic circuit method with finite-element simulations to characterise dynamic stiffness under high-rotation conditions. Experimental measurements validated that both current-dependent and displacement-dependent stiffness coefficients exhibit frequency-sensitive behaviour. The proposed measurement method offers precise quantification of dynamic stiffness, thereby informing more accurate control models and improving stability margins for high-speed AMB applications.

Active Magnetic Bearing Systems and Control Techniques publication trend

The graph below shows the total number of articles in active magnetic bearing systems and control techniques across all publications each year (not limited to Nature Index journals).

Technical terms

Active Magnetic Bearing (AMB): A non-contact support system that uses controlled electromagnetic forces to suspend a rotating shaft within an air gap.

Dynamic stiffness: The frequency-dependent ratio of force to displacement in an AMB, reflecting variations in bearing support rigidity under different speeds.

Sliding Mode Control (SMC): A robust control strategy that forces system trajectories to follow a specified surface by switching control inputs, offering strong disturbance rejection.

Iterative Learning Control (ILC): A method for systems executing repetitive tasks, which refines control inputs from previous cycle errors to improve performance over successive iterations.

Notch filter: An electronic filter designed to attenuate narrow-band disturbances at specific resonant frequencies, preventing instability due to rotor natural modes.

References

1. Dynamic Stiffness Analysis and Measurement of Radial Active Magnetic Bearing in Magnetically Suspended Molecular Pump. Scientific Reports (2020).
2. Robust Control Design for an Active Magnetic Bearing System Using Advanced Adaptive SMC Technique. IEEE Access (2021).
3. Optimization Research on a Switching Power Amplifier and a Current Control Strategy of Active Magnetic Bearing. IEEE Access (2020).
4. Unbalance Compensation and Automatic Balance of Active Magnetic Bearing Rotor System by Using Iterative Learning Control. IEEE Access (2019).