Synthesis of Hybrid Fuzzy Logic Law for Stable Control of Magnetic Levitation System

In this paper, we present a method to design a hybrid fuzzy logic controller (FLC) for a magnetic levitation system (MLS) based on the linear feedforward control method combined with FLC. MLS has many applications in industry, transportation, but the system is strongly nonlinear and unstable at equilibrium. The fast response linear control law ensures that the ball is kept at the desired point, but does not remain stable at that point in the presence of noise or deviation from the desired position. The controller that combines linear feedforward control and FLC is designed to ensure ball stability and increase the system's fast-response when deviating from equilibrium and improve control quality. Simulation results in the presence of noise show that the proposed control law has a fast and stable effect on external noise. The advantages of the proposed controller are shown through the comparison results with conventional PID and FLC control laws

Backstepping-based Super-Twisting Sliding Mode Control for a Quadrotor Manipulator with Tiltable Rotors

Designing a robust controller is very important in the control of outdoor unmanned aerial vehicles. This paper presents the design procedures and implementation of super-twisting sliding mode controller, which is a robust nonlinear controller. The robust controller is applied to an over-actuated quadrotor manipulator with four tiltable rotors. A serial manipulator with two links is mounted on the bottom of the quadrotor. The quadrotor possesses the property of decoupling its position and orientation. The main contribute of this paper is that a super-twisting sliding mode controller in vector form is designed and applied to the control of an over-actuated quadrotor manipulator. Another contribution of this paper is that the stability of the closed-loop system is proved by utilizing the Lyapunov stability theory. It is confirmed that the performance of the super-twisting sliding mode controller is superior to that of the conventional backstepping controller in terms of convergence rate and accuracy by simulations

Implementation of Nonlinear Controller to Improve DC Microgrid Stability: A Comparative Analysis of Sliding Mode Control Variants

Electricity generation from sustainable renewable energy sources is constantly accelerating due to a rapid increase in demand from consumers. This requires an effective energy management and control system to fulfil the power demand without compromising the system’s performance. For this application, a nonlinear barrier sliding mode controller (BSMC) for a microgrid formed with PV, a fuel cell and an energy storage system comprising a battery and supercapacitor working in grid-connected mode is implemented. The advantages of the BSMC are twofold: The sliding surface oscillates in the close vicinity of zero by adapting an optimal gain value to ensure the smooth tracking of power to its references without overestimating the gains. Secondly, it exhibits a noticeable robustness to variations and disturbance, which is the bottleneck of the problem in a grid-connected mode. The stability of the presented controllers was analyzed with the Lyapunov stability criterion. Moreover, a comparison of the BSMC with sliding mode and supertwisting sliding mode controllers was carried out in MATLAB/Simulink (2020b) with real PV experimental data. The results and the numerical analysis verify the effectiveness of the BSMC in regulating the DC bus voltage in the presence of an external disturbance under varying conventional load and environmental conditions

Discrete-time sliding mode control based on disturbance observer applied to current control of permanent magnet synchronous motor

This paper proposes a robust current control technique based on a discrete-time sliding mode controller and a disturbance observer for high-performance permanent magnet synchronous motor (PMSM) drives. This scheme is applied in the PMSM current control loops to enable the decoupling between the dq current axes, rejection of disturbances caused by mechanical load changes and robustness under parametric uncertainties. In order to ensure the discrete-time sliding mode properties, which make the system cross the sliding surface at each sampling period, the PMSM model is extended, including the digital implementation delay resulting from the discrete-time algorithm execution. The development of this method allows direct implementation in microcontrollers and digital signal processors. Stability and convergence analysis are developed in the discrete-time domain. Simulation and experimental results demonstrate the effectiveness and good performance of the proposed current control approach