An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

The Self-Organizing Map

Fuzzy logic control was originally introduced and developed as a model free control design approach. However, it unfortunately suffers from criticism of lacking of systematic stability analysis and controller design though it has a great success in industry applications. In the past ten years or so, prevailing research efforts on fuzzy logic control have been devoted to model-based fuzzy control systems that guarantee not only stability but also performance of closed-loop fuzzy control systems. This paper presents a survey on recent developments (or state of the art) of analysis and design of model based fuzzy control systems. Attention will be focused on stability analysis and controller design based on the so-called Takagi-Sugeno fuzzy models or fuzzy dynamic models. Perspectives of model based fuzzy control in future are also discussed

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A Survey on Analysis and Design of Model-Based Fuzzy Control Systems

In this paper, a novel design method for determining the optimal proportional-integral-derivative (PID) controller parameters of an AVR system using the particle swarm optimization (PSO) algorithm is presented. This paper demonstrated in detail how to employ the PSO method to search efficiently the optimal PID controller parameters of an AVR system. The proposed approach had superior features, including easy implementation, stable convergence characteristic, and good computational efficiency. Fast tuning of optimum PID controller parameters yields high-quality solution. In order to assist estimating the performance of the proposed PSO-PID controller, a new time-domain performance criterion function was also defined. Compared with the genetic algorithm (GA), the proposed method was indeed more efficient and robust in improving the step response of an AVR system.

A particle swarm optimization approach for optimum design of PID controller in AVR system

Fuzzy Rule-Based Systems Evolutionary Computation Introduction to Genetic Fuzzy Systems Genetic Tuning Processes Learning with Genetic Algorithms Genetic Fuzzy Rule-Based Systems Based on the Michigan Approach Genetic Fuzzy Rule-Based Systems Based on the Pittsburgh Approach Genetic Fuzzy Rule-Based Systems Based on the lterative Rule Learning Approach Other Genetic Fuzzy Rule-Based System Other Kinds of Evolutionary Fuzzy Systems Applications.

Genetic Fuzzy Systems: Evolutionary Tuning And Learning Of Fuzzy Knowledge Bases

In this paper, a 2 DOF planar robot was controlled by Fuzzy Logic Controller tuned with a particle swarm optimization. For a given trajectory, the parameters of Mamdani-type-Fuzzy Logic Controller (the centers and the widths of the Gaussian membership functions in inputs and output) were optimized by the particle swarm optimization with three different cost functions. In order to compare the optimized Fuzzy Logic Controller with different controller, the PID controller was also tuned with particle swarm optimization. In order to test the robustness of the tuned controllers, the model parameters and the given trajectory were changed and the white noise was added to the system. The simulation results show that Fuzzy Logic Controller tuned by particle swarm optimization is better and more robust than the PID tuned by particle swarm optimization for robot trajectory control.

A Fuzzy Logic Controller tuned with PSO for 2 DOF robot trajectory control

Due to their powerful optimization property, genetic algorithms (GAs) are currently being investigated for the development of adaptive or self-tuning fuzzy logic control systems. This paper presents a neuro-fuzzy logic controller (NFLC) where all of its parameters can be tuned simultaneously by GA. The structure of the controller is based on the radial basis function neural network (RBF) with Gaussian membership functions. The NFLC tuned by GA can somewhat eliminate laborious design steps such as manual tuning of the membership functions and selection of the fuzzy rules. The GA implementation incorporates dynamic crossover and mutation probabilistic rates for faster convergence. A flexible position coding strategy of the NFLC parameters is also implemented to obtain near optimal solutions. The performance of the proposed controller is compared with a conventional fuzzy controller and a PID controller tuned by GA. Simulation results show that the proposed controller offers encouraging advantages and has better performance.

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Tuning of a neuro-fuzzy controller by genetic algorithm

An integrated General Regression Neural Network (GRNN) adaptation scheme for dynamic plant modelling is proposed in this paper. It possesses several improved features compared to the original GRNN proposed by Specht (1991), such as flexible pattern nodes add-in and delete-off mechanism, dynamic initial sigma assignment using a nonstatistical method, automatic target adjustment and sigma tuning. These adaptation strategies are formulated based on the inherent advantageous features found in GRNN, such as highly localised pattern nodes, good interpolation capability, instantaneous learning. Good modelling performance is obtained when the GRNN is tested on a linear plant in a noisy environment. It performs better than the well-known extended recursive least squares identification algorithm. Analysis on the effects of some of the adaptation parameters involving a nonlinear plant is also investigated. The results show that the proposed methodology is computationally efficient and exhibits several attractive features such as fast learning, flexible network sizing and good robustness, which are suitable for the construction of estimators or predictors for many model-based adaptive control strategies.

Adaptive GRNN for the modelling of dynamic plants

Recently, adaptive control systems utilizing artificial intelligent techniques are being actively investigated in many applications. Neural networks with their powerful learning capability are being sought as the basis for many adaptive control systems where on-line adaptation can be implemented. Fuzzy logic, on the other hand, has proved to be rather popular in many control system applications due to providing a rule-base like structure. In this paper, an adaptive neuro-fuzzy control system is proposed in which the Radial Basis Function neural network (RBF) is implemented as a neuro-fuzzy controller (NFC) and the General Regression neural network (GRNN) as a predictor. The adaptation of the system involves the following three procedures: (1) tuning of the control actions or rules, (2) trimming of the control actions, and (3) adjustment of the controller output gain. The tuning method is a non-gradient descent method based on the predicted system response which is able to self-organize the control actions from the initial stage. The trimming scheme can help to reduce the aggressiveness of the particular control rules such that the response is stabilized to the set-points more effectively, while the controller gain adjustment scheme can be applied in the cases where the appropriate controller output gain is difficult to determine heuristically. To show the effectiveness of this methodology, its performance is compared with the well known Generalized Predictive Control (GPC) technique which is a combination of both adaptive and predictive control schemes. Comparisons are made with respect to the transient response, disturbance rejection and changes in plant dynamics. The proposed control system is also applied in controlling a single link manipulator. The results show that it exhibits robustness and good adaptation capability which can be practically implemented.

Adaptive Neuro-fuzzy Control System by RBF and GRNN Neural Networks

This paper proposes an integrated general regression neural network (GRNN) adaptation scheme for dynamic plant modelling. The scheme can be used in a noisy and dynamic environment for on-line process control. It possesses several distinguished features compared with the original GRNN proposed by Specht, such as a flexible pattern nodes add-in and delete-off mechanism, a dynamic initial sigma assignment using a non-statistical method, automatic target adjustment and sigma tuning. These adaptation strategies are formulated on the basis of the inherent advantageous features found in GRNN, such as highly localized pattern nodes, good interpolation capability and instantaneous learning. Good modelling performance was obtained when the GRNN is tested on a linear plant in a noisy environment. It performs better than the well-known extended recursive least-squares identification algorithm. In this paper, analysis of the effects of some of the adaptation parameters involving a non-linear plant is also investigated. The results show that the proposed methodology is computationally efficient and exhibits several attractive features such as fast learning, flexible network sizing and good robustness, which are suitable for the construction of estimators or predictors for many model-based adaptive control strategies.

Teo Lian Seng

Papers

Tuning of a neuro-fuzzy controller by genetic algorithm

Adaptive GRNN for the modelling of dynamic plants

Adaptive Neuro-fuzzy Control System by RBF and GRNN Neural Networks

Adaptive general regression neural network for modelling of dynamic plants