Coactive Neuro–Fuzzy Inference System
Last updated
Last updated
CANFIS belongs to a more general class of adaptive neuro-fuzzy inference systems (ANFIS) [19]. CANFIS may be used as a universal approximator of any nonlinear function. The characteristics of CANFIS are emphasized by the advantages of integrating NN with fuzzy inference systems (FIS) in the same topology. The powerful capability of CANFIS stems from pattern-dependent weights between the consequent layer and the fuzzy association layer. The architecture of CANFIS is illustrated in Figure 2-13.
The fundamental component for CANFIS is a fuzzy neuron that applies membership functions (MFs) to the inputs. Two membership functions are commonly used: general bell and Gaussian [21]. The network also contains a normalization axon to expand the output into a range of 0 to 1. The second major component in this type of CANFIS is a modular network that applies functional rules to the inputs. The number of modular networks matches the number of network outputs, and the number of processing elements in each network corresponds to the number of MFs. CANFIS also has a combiner axon that applies the MFs outputs to the modular network outputs. Finally, the combined outputs are channeled through a final output layer and the error is back propagated to both the MFs and the modular networks.
The function of each layer is described as follows. Each node in Layer 1 is the membership grade of a fuzzy set (A, B, C, or D) and specifies the degree to which the given input belongs to one of the fuzzy sets. The fuzzy sets are defined by three membership functions. Layer 2 receives input in the form of the product of all output pairs from the first layer. The third layer has two components. The upper component applies the membership functions to each of the inputs, while the lower component is a representation of the modular network that computes, for each output, the sum of all the firing strengths. The fourth layer calculates the weight normalization of the output of the two components from the third layer and produces the final output of the network.