Piece-wise Linear Fuzzy Sliding Mode Controller for Deep Submergence Rescue Vehicle (DSRV)

The paper aims to present the design and performance of a single input fuzzy sliding mode controller (SIFSMC) to control the motion of deep submergence rescue vehicle (DSRV). The proposed controller uses the linear single dimension rule base where as the conventional fuzzy sliding mode controllers (CFSMC) uses the two-dimensional rule base. Moreover, the proposed controller does not merely depend on the DSRV exact mathematical model unlike that of the linear controllers. Using SIFSMC, the number of rules governs are also greatly reduced in comparison with the CFSMC, without compromising the overall performance. The robustness, equivalency and efficacy of proposed idea is illustrated through the simulation results using a marine system simulator in MATLAB/Simulink® environment. The main objective of the paper is to compare CFSMC and SIFSMC for UUV’s. Consequently, a comparative analysis of proposed SIFSMC is shown with the CFSMC for the same system of DSRV.

An optimized double-integral-sliding-mode-controller for a PV microgrid

Purpose The dynamics of the PV microgrid (PVMG) system are highly nonlinear and uncertain in nature. It is encountered with parametric uncertainties and disturbances. This system cannot be controlled properly by conventional linear controllers. H− controller and sliding mode controller (SMC) may capable of controlling it with ease. Due to its inherent dynamics, SMC introduces unwanted chattering into the system output waveforms. This paper aims to propose a controller to reduce this chattering. Design/methodology/approach This paper presents redesign of the SMC by modifying its sliding surface and tuning its parameters by employing water-evaporation-optimization (WEO) based metaheuristic algorithm. Findings By using this proposed water-evaporation-optimization algorithm-double integral sliding mode controller (WEOA-DISMC), the chattering magnitude is diminished greatly. Further, to examine which controller between H8 controller and proposed WEOA-DISMC performs better in both normal and uncertain situations, a comparative analysis has been made in this paper. The considered comparison parameters are reference tracking, disturbance rejection and robust stability. Originality/value WEO tuned DISMC for PVMG system is the contribution.

New design and comparative study via two techniques for wind energy conversion system

Introduction. With the advancements in the variable speed direct drive design and control of wind energy systems, the efficiency and energy capture of these systems is also increasing. As such, numerous linear controllers have also been developed, in literature, for MPPT which use the linear characteristics of the wind turbine system. The major limitation in all of those linear controllers is that they use the linearized model and they cannot deal with the nonlinear dynamics of a system. However, real systems exhibit nonlinear dynamics and a nonlinear controller is required to handle such nonlinearities in real-world systems. The novelty of the proposed work consists in the development of a robust nonlinear controller to ensure maximum power point tracking by handling nonlinearities of a system and making it robust against changing environmental conditions. Purpose. In the beginning, sliding mode control has been considered as one of the most powerful control techniques, this is due to the simplicity of its implementation and robustness compared to uncertainties of the system and external disturbances. Unfortunately, this type of controller suffers from a major disadvantage, that is, the phenomenon of chattering. Methods. So in this paper and in order to eliminate this phenomenon, a novel non-linear control algorithm based on a synergetic controller is proposed. The objective of this control is to maximize the power extraction of a variable speed wind energy conversion system compared to sliding mode control by eliminating the phenomenon of chattering and have a good power quality by fixing the power coefficient at its maximum value and the Tip Speed Ratio maintained at its optimum value. Results. The performance of the proposed nonlinear controllers has been validated in MATLAB/Simulink environment. The simulation results show the effectiveness of the proposed scheme, suppression of the chattering phenomenon and robustness of the proposed controller compared to the sliding mode control law.

Analysis of Footprint of Uncertainty of the IT2 Mamdani Controllers Using Different Type-Reducers

Appropriate Footprint of Uncertainties (FOUs) are beneficial to the performance of Interval Type-2 (IT2) fuzzy controller, revealing the effect of FOUs is a key problem. In our published work, as the FOUs increase, the IT2 Mamdani and TS fuzzy controllers, using KM or EKM type-reducer (TR), approach the constant and piecewise linear controllers, respectively, while they finally become constant and piecewise linear controllers. To verify the validation of the above results, when a different TR is used, in this study, the effects of other popular TRs (i.e., Nie-Tan, Wu-Mendel, Iterative Algorithm with Stop Condition) on output of IT2 Mamdani fuzzy controller, are explored. We proven that, (1) as the FOUs increase, irrespectively of the TRs used, the IT2 Mamdani fuzzy controllers approach constant controllers, (2) when all the FOUs are equal to 1 (i.e., at their maximum ), the fuzzy controllers using Nie-Tan and Iterative Algorithm with Stop Condition TR become constant controllers. The FOUs of the controllers using Wu-Mendel TR can be infinitely approaching 1 and cannot be equal to 1 (otherwise, the denominator of the TR output expression are equal to 0), hence when FOUs are infinitely approaching 1, the controller will approach the constant controller infinitely. These results imply regardless of which popular TR is used, the IT2 Mamdani fuzzy controller, when using larger FOUs, the fluctuation of the input variables have a limited impact on the output, the ability to deal with system uncertainties will deteriorate. Laboratory control experiments are provided to demonstrate these findings.

Advanced exponential sliding mode control for microgrid at autonomous and grid-connected modes

This paper introduces a novel control scheme for the operation of multilevel inverters forming a microgrid. The core of the suggested control scheme is an advanced (power-rate) exponential sliding mode controller. This developed controller is robust toward any variation of the system’s parameters and loads in addition to its fast and accurate performance. The presented control scheme provides advantageous characteristics to the microgrid operation in an autonomous mode (microgrid mode) and grid-connected mode. In the microgrid mode, the voltages and frequency are stable at any variable balanced and unbalanced load. In the grid-connected mode, an effective procedure for connecting the microgrid to the main grid is proposed to guarantee a seamless and fast transition to the grid-connected mode. The performance of the presented control scheme along with its proposed controller is validated by comparing its results to another linear and non-linear controllers for the same microgrid loading conditions.

A study of Comparative analysis of fuzzy logic controller and neural network for dc–dc buck converter

This paper presents the comparative analysis between fuzzy logic controller and neural network for DC-DC Buck converter. The major drawback in the conventional buck converter is when the input voltage or load change, the output voltage also changes which reduces the overall efficiency of the buck converter. So here we are using non linear controllers for buck converter which respond quickly for perturbations and maintains the fixed load voltage even when there are non-linearity’s occurs compared to a linear controllers like P,PI,PID controllers which can’t withstand when perturbations occur. Simplicity, low cost and adaptability to the complex systems without mathematical modeling are the best features of Fuzzy Logic controller and neural networks. The Two implementations are analyzed in detail and simulated in MATLAB/SIMULINK environment and results presented. Proposed approach is implemented on DC to DC step down converter for an input of 230V and performance characteristics like maximum overshoot, settling time and efficiency of the converter are studied.