Design of Controller for Repulsive Type Magnetic Bearing

Abstract

quotBearings play a crucial role in modern engineering by reducing friction, supporting rotating parts, and improving the durability and efficiency of machinery from medical tools to wind turbines. Conventional ball and roller bearings suffer from contact-related issues such as friction, wear, heat, and the need for constant lubrication, which limits performance under high speeds or heavy loads. newlineThis work examines a Vertical Shaft Repulsive Type Hybrid Magnetic Bearing (VSRHMB). The system provides strong radial control through repulsive permanent magnetic forces but faces challenges with axial stability. Experimental operation of the constructed VSRHMB confirms reliable radial performance while revealing difficulties in maintaining consistent axial positioning. To address this, a low-bias current integral optimal control method is applied for a single Degree of Freedom (1-DOF). Simulations using MATLAB and Ansys Maxwell show that higher bias currents enhance linearity and disturbance rejection but raise copper losses, emphasizing the importance of selecting an optimal bias level. Adjusting the rotor magnet s axial offset enables tuning of the bias current, improving axial vibration control with relatively low power consumption. newlineSince axial instability becomes more significant at elevated speeds, an Adaptive Sliding Mode Controller (ASMC) is introduced. While effective at low speeds, ASMC alone leads to steady-state errors and excessive control effort as speed increases. To overcome this, a Fuzzy Logic-based Gain Scheduling mechanism is integrated into the ASMC. Experimental results show that this hybrid controller maintains axial stability across a wide speed range, keeps steady-state errors under 10%, and limits control voltage below 450 V at speeds up to 25,000 rpm. The findings confirm the robustness and efficiency of the proposed control strategy for high-speed VSRHMB operation.quot newline newline