3.4 模糊控制器与多值继电控制器的关系
Kickert和Mamdani揭示了模糊控制器与多值继电控制器的关系。一类简单的模糊控制器,其输入-输出特性具有多值继电特性,故可看作多值继电控制器[31]。Ying[3]证明了采用两个输入变量、多个三角形输入模糊集、线性控制规则、均匀分布的独点输出模糊集、不同推理方法和重心解模糊器的Mamdani模糊控制器,是一个全局的两维多值继电控制器和一个局部的非线性PI控制器之和[3]。这些结果被一般化到采用非均匀分布的多个三角形输入模糊集的SISO、采用非线性控制规则的SISO和MIMOMamdani模糊控制器[4-6]。根据模糊控制器与多值继电控制器的关系,可用经典控制理论中描述函数的方法来分析和设计模糊控制系统,并确保其稳定性。


Typical and complex TS fuzzy controllers have been structurally proved to be nonlinear gain planners [20, 21]. These TS fuzzy controllers are composed of multiple trapezoidal (or triangular) input fuzzy sets, TS fuzzy rules with linear afterterms, Zadeh fuzzy logic and operation and barycentric defuzzifier. Different from the linear controller with different constant gains at different operating points of the conventional gain planner, the gain of the nonlinear gain planner changes continuously with the output of the controlled system. These proofs not only make up for the simple explanation of the relationship between fuzzy controller and gain controller, but also explain the effectiveness of fuzzy controller in dealing with nonlinear problems.3.4 relationship between fuzzy controller and multivalued relay controller
Kickert and Mamdani revealed the relationship between fuzzy controller and multivalued relay controller. A kind of simple fuzzy controller, whose input-output characteristics have multivalued relay characteristics, can be regarded as multivalued relay controller [31]. Ying [3] proved that the Mamdani fuzzy controller using two input variables, multiple triangular input fuzzy sets, linear control rules, uniformly distributed single point output fuzzy sets, different reasoning methods and center of gravity defuzzifier is the sum of a global two-dimensional multivalued relay controller and a local nonlinear PI controller [3]. These results are generalized to SISO with non uniformly distributed triangular input fuzzy sets, SISO with nonlinear control rules and mimomamdani fuzzy controller [4-6]. According to the relationship between fuzzy controller and multivalued relay controller, the method of describing function in classical control theory can be used to analyze and design fuzzy control system and ensure its stability.







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