Linguistic hedges and fuzzy rule base systems

A novel fuzzy logic controller called linguistic-hedge fuzzy logic controller and its hardware implementation in a mixed-signal approach is presented in this paper. Several major characteristics of this controller are: 1) only three simple-shape membership functions are required for characterizing each variable; 2) nine rules are enough for inference; 3) both architecture and hardware design complexity are small. For the implementation, a current-mode approach is adopted in designing the signal processing portions to simplify the circuit complexity; digital circuits are adopted to implement the programmable units. This design was fabricated with a TSMC 0.35 mum single-polysilicon-quadruple-metal CMOS process. In this chip, the LHFLC processes two input variables and one output variable. Under a supply voltage of 3.3 V. The speed of inference operation goes up to 0.5M FLIPS that is fast enough for the control application of the cart-pole balance system.