PID Control for Radial Active Magnetic Bearings

The development of Active Magnetic Bearing (AMB) technology for gas turbines has made significant strides. Initiatives like the Versatile Affordable Advanced Turbine Engines (VAATE) program, in collaboration with DARPA and NASA, aim to enhance gas turbine engineering for efficiency, cleanliness, intelligence, versatility, and durability. AMBs have emerged as superior to rolling element and foil bearings due to their temperature, speed, shaft thickness limitations, and shorter lifespan under heavy loads. AMBs are more suitable for large machines operating under high loads and relatively lower speeds than foil bearings. The research introduces a two-degrees-of-freedom model for AMB systems. The modelling involves two identical electromagnets and simplified equations. The model also considers external forces, including sinusoidal forces from motor vibrations, centrifugal forces from shaft unbalanced assumptions and static forces. The system output is represented by eccentricity. The AMB design adheres to SKF standards for conventional bearings. The rotor model is simulated using MATLAB SIMULINKTM, and the Automatic PID Tuner App is used to find control values based on the created transfer function. System stability is analyzed using the Nyquist stability criteria, focusing on the input rotation speed range of 100 RPM–459 k RPM. Higher motor rotation rates contribute favorably to the rotor's ability to remain centred within the stator. Higher motor rotation rates contribute favorably to the rotor's ability to remain centred within the stator. Specifically, the PID controller exhibits excellent resistance to various external forces. Static tests assessed the system's ability to bear loads, where forces ranging from 100 to 400 N were applied to the rotor. However, adding a 400N load to the rotor has exceeded the value of \(\text{1,5}\times {10}^{-3}\) m as the maximum eccentricity threshold. As a result, the maximum load that can be applied to this design is 388 N, with the resulting eccentricity being \(\text{1,48}\times {10}^{-3}\) m.