Quantisation Errors in Digital Implementations of Fuzzy Controllers
Fuzzy Logic Controllers (FLCs) have proven useful in the control of complex and nonlinear processes. Unlike conventional control, which is based on a precise model of a process, fuzzy control is able to handle linguistic information in the form of IF-THEN rules. These rules usually encapsulate the experience of human operators and engineers. At present, most FLCs are implemented digitally. Microprocessors, digital signal processors (DSPs), and application specific integrated circuits (ASICs) are used to cope with real time fuzzy control. Therefore, the quantisation noise due to the finite length of digital words is to be taken into account in designing fuzzy systems. Digital implementations of FLCs involve three main types of quantisation errors: the analogue-to-digital (A/D) errors, the membership function errors, and the arithmetic errors. The consequences of these errors on the behaviour of a typical FLC are analysed and the problem of the selection of a digital format for fuzzy information is addressed.
KeywordsMembership Function Fuzzy System Fuzzy Control Fuzzy Controller Quantisation Error
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