Control fuzzy-logic

Fuzzifieation is the proeess of mapping inputs to the FLC into fuzzy set membership values in the various input universes of diseourse. Deeisions need to be made regarding 

A FLC that emulates a PD eontroller will be required to minimize the error e(t) and the rate of ehange of error de/dt, or ce. 

The size of the universes of diseourse will depend upon the expeeted range (usually up to the saturation level) of the input variables. Assume for the system about to be eonsidered that e has a range of 6 and ce a range of 1. 

The number and shape of fuzzy sets in a partieular universe of diseourse is a tradeoff between preeision of eontrol aetion and real-time eomputational eomplexity. In this example, seven triangular sets will be used. 

The fuzzy rulebase consists of a set of antecedent-consequent linguistic rules of the form 

In order to process the input to obtain the output reasoning, there are six steps involved in the creation of a rule based fuzzy system  

Identify the inputs and their ranges and name them. 

Create the degree of fuzzy membership function for each input and output. 

Construct the rule base that the system will operate under. 

---

While the single-loop PID controller is satisfactoiy in many process apphcations, it does not perform well for processes with slow dynamics, time delays, frequent disturbances, or multivariable interactions. We discuss several advanced control methods hereafter that can be implemented via computer control, namely feedforward control, cascade control, time-delay compensation, selective and override control, adaptive control, fuzzy logic control, and statistical process control. 

Fuzzy Logic Control The apphcation of fuzzy logic to process control requires the concepts of Fuzzy rules and fuzzy inference. A fuzzy rule, also known as a fuzzy IF-THEN statement, has the form ... 

Sometimes fuzzy logic controllers are combined with pattern recognition software such as artificial neural networks (Kosko, Neural Networks and Fuzzy Systems, Prentice Hall, Englewood Cliffs, New Jersey, 1992). 

Fuzzy logic control systems 10.2.1 Fuzzy set theory... 

MATLAB Fuzzy Inference System (FIS) editor can be found in Appendix 1. Figure 10.16 shows the control surface for the 11 set rulebase fuzzy logic controller. 

Self-Organizing Fuzzy Logic Control (SOFLC) is an optimization strategy to create and modify the control rulebase for a FLC as a result of observed system performance. The SOFLC is particularly useful when the plant is subject to time-varying parameter changes and unknown disturbances. 

Fig. 10.16 Control surface for 11 set rulebase fuzzy logic controller.

Fig. 10.17 Self-Organizing Fuzzy Logic Control system.

The angular positional control system shown by the block diagram in Figure 10.36 is to have the velocity feedback loop removed and controller K replaced by a fuzzy logic controller (FLC) as demonstrated by Barrett (1992). The inputs to the FLC... 

Fig. A1.8 Simulink implementation of inverted pendulum fuzzy logic control problem.

It may be useful to point out a few topics that go beyond a first course in control. With certain processes, we cannot take data continuously, but rather in certain selected slow intervals (c.f. titration in freshmen chemistry). These are called sampled-data systems. With computers, the analysis evolves into a new area of its own—discrete-time or digital control systems. Here, differential equations and Laplace transform do not work anymore. The mathematical techniques to handle discrete-time systems are difference equations and z-transform. Furthermore, there are multivariable and state space control, which we will encounter a brief introduction. Beyond the introductory level are optimal control, nonlinear control, adaptive control, stochastic control, and fuzzy logic control. Do not lose the perspective that control is an immense field. Classical control appears insignificant, but we have to start some where and onward we crawl. 

Fusion power, noble gases and, 17 375 Fusion process, 9 278 10 361-364, 365 Fusion reactors, vanadium in, 25 526 FutureGen Program (Department of Energy), 13 845 Fuzzy logic control, 20 698-699 Fuzzy rules, 20 699 F values, 13 252... 

Fuzzy logic control Longitudinal combustion instabili- 1. Only effective when many states can be sensored... 

Other advanced control structures have been studied, including nonlinear control, fuzzy logic control and MPC. A recent review of control studies is given by Uygun and coworkers.3... 

Uygun, H. Ta kin, C. Kubat, and S. Arslankaya, FUZZYFCC Fuzzy logic control of a fluid catalytic cracking unit (FCCU) to improve dynamic performance, Computers Chemical Engineering, 30(5), 850-863 (2006). 

The common characteristic of fuzzy logic and neural networks is that one does not need to know anything about the mathematical model of the process in order to utilize them. In a way it is like the tennis player who can hit the ball without the in-depth knowledge of Newton s laws of motion and how these laws apply to the tennis process. A fuzzy logic controller just mimics the operator (the tennis player) in its responses. 

---