2,464 research outputs found

    Terminal sliding mode control strategy design for second-order nonlinear system

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    This study mainly focuses on the terminal sliding mode control (TSMC) strategy design, including an adaptive terminal sliding mode control (ATSMC) and an exact-estimator-based terminal sliding mode control (ETSMC) for second-order nonlinear dynamical systems. In the ATSMC system, an adaptive bound estimation for the lump uncertainty is proposed to ensure the system stability. On the other hand, an exact estimator is designed for exact estimating system uncertainties to solve the trouble of chattering phenomena caused by a sign function in ATSMC law in despite of the utilization of a fixed value or an adaptive tuning algorithm for the lumped uncertainty bound. The effectiveness of the proposed control schemes can be verified in numerical simulations.<br /

    Theoretical analysis and experimental validation of a simplified fractional order controller for a magnetic levitation system

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    Fractional order (FO) controllers are among the emerging solutions for increasing closed-loop performance and robustness. However, they have been applied mostly to stable processes. When applied to unstable systems, the tuning technique uses the well-known frequency-domain procedures or complex genetic algorithms. This brief proposes a special type of an FO controller, as well as a novel tuning procedure, which is simple and does not involve any optimization routines. The controller parameters may be determined directly using overshoot requirements and the study of the stability of FO systems. The tuning procedure is given for the general case of a class of unstable systems with pole multiplicity. The advantage of the proposed FO controller consists in the simplicity of the tuning approach. The case study considered in this brief consists in a magnetic levitation system. The experimental results provided show that the designed controller can indeed stabilize the magnetic levitation system, as well as provide robustness to modeling uncertainties and supplementary loading conditions. For comparison purposes, a simple PID controller is also designed to point out the advantages of using the proposed FO controller

    Model predictive control of magnetic levitation system

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    In this work, we suggest a technique of controller design that applied to systems based on nonlinear. We inform the sufficient conditions for the stability of closed loop system. The asymptotic stability of equilibrium and the nonlinear controller can be applied to improvement the stability of Magnetic Levitation system(MagLev). The MagLev nonlinear nodel can be obtained by state equation based on Lagrange function and Model Predictive Control has been used for MagLev system

    Index to 1984 NASA Tech Briefs, volume 9, numbers 1-4

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    Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1984 Tech B Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

    A Hybrid Controller for Stability Robustness, Performance Robustness, and Disturbance Attenuation of a Maglev System

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    Devices using magnetic levitation (maglev) offer the potential for friction-free, high-speed, and high-precision operation. Applications include frictionless bearings, high-speed ground transportation systems, wafer distribution systems, high-precision positioning stages, and vibration isolation tables. Maglev systems rely on feedback controllers to maintain stable levitation. Designing such feedback controllers is challenging since mathematically the electromagnetic force is nonlinear and there is no local minimum point on the levitating force function. As a result, maglev systems are open-loop unstable. Additionally, maglev systems experience disturbances and system parameter variations (uncertainties) during operation. A successful controller design for maglev system guarantees stability during levitating despite system nonlinearity, and desirable system performance despite disturbances and system uncertainties. This research investigates five controllers that can achieve stable levitation: PD, PID, lead, model reference control, and LQR/LQG. It proposes an acceleration feedback controller (AFC) design that attenuates disturbance on a maglev system with a PD controller. This research proposes three robust controllers, QFT, Hinf , and QFT/Hinf , followed by a novel AFC-enhanced QFT/Hinf (AQH) controller. The AQH controller allows system robustness and disturbance attenuation to be achieved in one controller design. The controller designs are validated through simulations and experiments. In this research, the disturbances are represented by force disturbances on the levitated object, and the system uncertainties are represented by parameter variations. The experiments are conducted on a 1 DOF maglev testbed, with system performance including stability, disturbance rejection, and robustness being evaluated. Experiments show that the tested controllers can maintain stable levitation. Disturbance attenuation is achieved with the AFC. The robust controllers, QFT, Hinf , QFT/ Hinf, and AQH successfully guarantee system robustness. In addition, AQH controller provides the maglev system with a disturbance attenuation feature. The contributions of this research are the design and implementation of the acceleration feedback controller, the QFT/ Hinf , and the AQH controller. Disturbance attenuation and system robustness are achieved with these controllers. The controllers developed in this research are applicable to similar maglev systems

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

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    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

    Development of Internet-Based Instrumentation System for the Study of Superconducting Magnetic Levitation

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    Computers can be utilized to control instruments, machines, motors, devices etc. to automate tasks. Presently, an automation system had been constructed and successfully used to conduct the physics experiments to study the levitation force in the Bi-Sr-Ca-Cu-O (BSCCO) high Tc superconductor series. This research project aims to improve the automation system. Two major improvements were made; first, converting the existing automation system into a Web based automation system and replacing the DOS based QBasic program with Windows based user interface . The Web based automation system can be remotely controlled and monitored by users in remote locations by using only their web browsers; as if they (the users) are sitting right in front of the automation system! This is achieved by programming the server computer (which was interfaced to the automation system) to load Java Applets containing the user interface required to control the automation system, into the remote user's web browser The Web based automation system is also capable of remote data acquisition or DAQ, whereby experimental data can be remotely acquired by the user through File Transfer Protocol (FTP). Three major types of test essential for the study of superconducting levitation forces were also integrated into the user interface. The tests are: detection of magnetic hysteresis, detection of stiffness loops for increasing distance and detection of magnetic stiffness for decreasing distance. Each test requires varying degrees of control over a stepper motor's movement. The stepper motor is the key component of the automation system and is used to vary the distance between the magnetic materials in small, controlled, steps of 0.05 mm per movement. Both the user interface and the Web based features were developed using a graphical programming language called LabVIEW. The Web based automation system was used to conduct a series of experiments to study the levitation forces of Cadium (Cd) doped Bi-Sr-Ca-Cu-O (BSCCO) high Tc superconductor series. Users are successful in logging into the automation system to control, monitor and acquire data remotely from the automation system in real time. The Web based automation system was successful in detecting magnetic hysteresis for all the superconductor samples measured. Further, magnetic stiffness loops were also detected over all samples. Analysis of the magnetic hysteresis and stiffness loops showed agreement with work done by Chang and Moon, two prominent researchers in the field of superconductor research
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