In this paper, the robust control method is proposed for air-gap positioning of magnetic levitation systems considering levitation disturbance forces caused by propulsion systems. Even though the disturbance effect occurs inevitably by propulsion systems, it is very difficult or impossible to be measured by sensors in real time. In order to maintain the constant air-gap position according to the reference command in propulsion state of the vehicle, robust control for electromagnetic suspension against levitation disturbance force is highly required. The disturbance force caused by propulsion systems is predicted by the finite element method analysis of the magnetic flux distribution. Based on the analyzed result, the robust and optimal levitation controller is designed by convex optimization method for the proposed proportional integral derivative controller with the inner feedback compensator stabilizing the nonlinear plant. The proposed controller has the formulation of the conventional full-state feedback optimal controller based on state-output matching for the unmeasured state. The effectiveness of the proposed controller is verified by simulation and finite element method analysis.

In this paper, a novel control method is proposed for superconducting-hybrid magnetic levitation systems applied in conveyor manufacturing facilities. Recently, magnetic levitation systems are variously researched not only for high-speed transportation but also manufacturing process requiring the dust-free condition. The proposed controller consists of the inner feedback compensator and set-point error controller. The structure of the controller with convex set between conventional proportional-derivative-integral controllers guarantees the performances and robustness of the conventional controller and makes it possible to consider the additional properties that can be converted into linear matrix inequality constraints. The control factors are determined by solving the optimization problem with linear matrix inequalities to be expressed for time-domain specifications such as overshoot, rise time, and settling time and control input bound. The effectiveness of the proposed controller is verified by the simulation and finite-element analysis.

This paper proposes a new $H_{\infty }$ static output feedback control method to address the congestion control problem in transmission control protocol networks using active queue management routers. Based on linear matrix inequality optimization, this method determines a static output feedback control law to minimize the $H_{\infty }$ norm of the transfer function between the controlled queue length of the buffer and the exogenous disturbance affecting the available link bandwidth. A linear matrix inequality formulation is presented as a sufficient condition to guarantee the closed-loop system’s asymptotic stability while maintaining disturbance rejection within a specified level, regardless of round-trip time delays. The proposed robust static output feedback control eliminates the need to measure or estimate all system states, thus simplifying practical implementation. The effectiveness of the proposed design method is demonstrated by applying it in a practical process, as illustrated through a numerical example.

Recently, magnetic levitation systems have been applied and studied in various industrial fields. In particular, in-tracktype magnetic levitation conveyor systems are actively studied since they can effectively minimize electromagnetic effects in processes that require a highly clean environment. In this type of system, diverse and multiple sensors are structurally required so that the control performance of an integrated system is primarily governed by the slowest measuring sensor. This paper proposes a multisensor fusion compensator to integrate the outputs obtained from various sensors into one output with the single fastest time rate. Since the state of the system is estimated at a fast time rate, the optimal controller also guarantees fast performance and stability. The computation of electromagnetic fields and the control performance of the considered superconducting hybrid system were analyzed using a computer simulation based on finite element methods.

This study proposes an electromagnetic balance-based structural design and shim plate application to improve the response characteristics of an electromagnetic brake. Electromagnetic brakes typically experience response delay due to inductive effects and residual magnetic flux after power-off. To address this issue, the inner and outer thicknesses of the stator were parameterized to achieve balanced magnetic flux distribution, and a non-magnetic shim plate (SUS 304) was applied to reduce residual flux within the electromagnet. Finite element analysis (FEA) was conducted to evaluate the influence of structural parameters on the magnetic flux balance and attractive force. The optimized stator geometry provided a stable electromagnetic balance, and the shim plate effectively reduced the response delay and improved the overall response performance compared with the conventional design. These findings demonstrate that the proposed electromagnetic balance design combined with shim plate application is an effective approach to enhance the reliability and control responsiveness of electromagnetic brakes, with potential applicability to robotic and industrial actuator systems.