This is an analog circuit implementation of discrete center of gravity defuzzifier in CMOS 0.35 μm process. Defuzzifiers are used as the last stage in a fuzzy system to translate the fuzzy logic data back to normal 'crisp' information. Center of gravity is one of the mostly used defuzzification methods.

The complete description of the design and implementation can be found in our paper (pdf or IEEE Xplore). Center of gravity defuzzification is essentially a weighted average of sample elements in the fuzzy system, weighted by their membership functions. The following structure ensures the output would be equal to discrete center of gravity of inputs:

To implement this structure, the following circuit is used, which instead of using the traditional multiplier-divider style, uses transconductance amplifiers (TCA) as a multiplier with voltage-input current-output by exploiting the voltage follower aggregation principle to increase speed and reduce chip area:

The circuit inside the frame is the TCA. Outside of that is shared among all the transconductance amplifies. As an illustration, the response of the defuzzifier to a repetition of two states of membership values for a set of seven sample elements is shown below:

The error for the same output is negligible compared to the scale of the output:

The Defuzzifier is implemented in HSPICE for simulation in the CMOS 0.35 μm process. In the time of the original simulations, a TSMC 0.35 μm technology file was used. You may use other technology files, probably with some minor alterations. There is one netlist file under the netlist directory that contains the code to the circuit and performs DC sweep, transient, and corner tests in simulation.

You may refer to this work by citing our published paper.

@inproceedings{hoseini2010circuit,
  title={Circuit design of voltage mode center of gravity defuzzifier in CMOS process},
  author={Hoseini, Pourya and Khoei, Abdollah and Hadidi, Khayrollah},
  booktitle={2010 International Conference on Electronic Devices, Systems and Applications},
  pages={169--173},
  year={2010},
  organization={IEEE}
}

Pourya Hoseini

I can be reached at [email protected].