MAGnetic LEVitation (Maglev) is a multi-variable, non-linear and unstable system that is used to levitate a ferromagnetic object in free space. This paper presents the stability control of a levitating object in a magnetic levitation plant using Fractional order PID (FOPID) controller. Fractional calculus, which is used to design the FOPID controller, has been a subject of great interest over the last few decades. FOPID controller has five tunning parameters including two fractional-order parameters (λ and µ). The mathematical model of the Maglev plant is obtained by using first principle modeling and the laboratory model (CE152). Maglev plant and FOPID controller both have been designed in MATLAB-Simulink. The designed model of the Maglev system can be further used in the process of controller design for other applications. The stability of the proposed system is determined via the Routh Hurwitz stability criterion. Ant Colony Optimization (ACO) algorithm and Ziegler Nichols method has been used to finetune the parameters of FOPID controller. FOPID controller output results are compared with the traditional IOPID controller for comparative analysis. FOPID controller, due to its extra tuned parameters, has shown extremely efficient results in comparison to the traditional IOPID controller.

The radiofrequency (RF) field used in magnetic resonance imaging is scattered by medical implants. The scattered field of a deep brain stimulation lead can be very intense near the electrodes stimulating the brain. The effect is more pronounced if the lead behaves as a resonant antenna. In this paper, we examine the resonant length effect. We also use the finite element method to compute the near field for (i) the lead immersed in inhomogeneous tissue (fat, muscle, and brain tissues) and (ii) the lead connected to an implantable pulse generator. Electric field, specific absorption rate and induced temperature rise distributions have been obtained in the brain tissue surrounding the electrodes. The worst-case scenario has been evaluated by neglecting the effect of blood perfusion. The computed values are in good agreement with in vitro measurements made in the laboratory.

Abstract-We have investigated the scattering of the MagneticResonance Imaging (MRI) radiofrequency (RF) field by implants for Deep Brain Stimulation (DBS) and the resultant heating of the tissue surrounding the DBS electrodes. The finite element method has been used to perform full 3-D realistic simulations. The near field has been computed for varying distances of the connecting portion of the lead from the air-tissue interface. Dissipated powers and induced temperature rise distributions have been obtained in the region surrounding the electrodes. It is shown that the near proximity of the air-tissue interface results in a reduction in the induced temperature rise.

No abstract

Abstract-During Magnetic Resonance Imaging (MRI), the presence of an implant such as a Deep Brain Stimulation (DBS) lead in a patient's body can pose a significant risk. This is due to the fact that the MR radiofrequency (RF) field can achieve a very high strength around the DBS electrodes. Thus the specific absorption rate (SAR), which is proportional to the square of the magnitude of the RF electric field, can have a very high concentration in the near-field region of the electrodes. The resulting tissue heating can reach dangerous levels. The degree of heating depends on the level of SAR concentration. The effects can be severe, leading to tissue ablation and brain damage, and significant safety concerns arise whenever a patient with an implanted DBS lead is exposed to MR scanning. In this paper, SAR, electric field, and temperature rise distributions have been found around actual DBS electrodes. The magnitude and spatial distribution of the induced temperature rises are found to be a function of the length and structure of the lead device, tissue properties and the MR stimulation parameters.