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When Should I Use Fuzzy Logic Controllers?

Primary Software: LabVIEW Toolkits>>PID and Fuzzy Logic Toolkit
Primary Software Version: 6.0
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
I know that the LabVIEW PID Control Toolkit includes the Fuzzy Logic Controller Design VI. Are there any advantages of using a fuzzy logic controller in a feedback control system?

Solution:
Most traditional control algorithms such as PID (proportional, integral and derivative), lead/lag, and pole-placement require an accurate mathematical model. However, it is sometimes very difficult or even impossible to obtain the mathematical model for the plant that you wish to control because most real systems are very non-linear. In addition, it is extremely difficult to control non-linear or complex systems with traditional control algorithms.

If an expert can qualitatively describe a control strategy, you can use a fuzzy logic technique to design a controller that emulates the heuristic rule-of-thumb strategy based on series of "If-Then" statements. In this case, instead of a mathematical model, you need an expert who has good experience with the system to develop the linguistic control rules. Then, you can use the Fuzzy Logic Controller Design VI in LabVIEW to create a fuzzy controller based on these rules, refer to the diagram below for generic fuzzy logic flow chart.


Figure 1. Fuzzy Logic Control Method

Refer to Part II (Chapters 4 to 8) of the Product Manuals: LabVIEW PID Control Toolkit User Manual (June 2008) to learn more about Fuzzy Logic and using the Fuzzy Logic Controller Design VI to design a fuzzy logic controller.

Related Links:
Product Manuals: LabVIEW PID Control Toolkit User Manual (June 2008)
Product Manuals: LabVIEW Control Design and Simulation Module Manuals
Developer Zone Community: PID, Fuzzy Logic and Real-Time Control Seminar



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Report Date: 10/20/2003
Last Updated: 05/28/2009
Document ID: 32JE6AVS

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