Design and implementation of a Mamdani fuzzy inference system on an FPGA

The growth in number of fuzzy logic applications led to the need of finding efficient ways to implement them. The advantage of using field programmable gate arrays (FPGA) is the ease with which controllers can be re-designed based on requirements without incurring major non recurring engineering (NRE) costs. In this paper, the implementation of a Mamdani fuzzy inference system has been demonstrated with the application of a home water sprinkler system. The design of the home water sprinkler system uses two inputs, temperature and soil humidity, to give a single output, watering duration. VHDL programming language is used for creating the design in which simulations are carried out to check the functional verification of individual blocks. The design created on VHDL platform was synthesized, verified and implemented using Xilinx integrated software environment (ISE) Version 6.1. The bit stream created is downloaded onto the Xilinx Virtex 2 FPGA which is mounted on a V2MB1000 board. For the verification of FIS, DIP switches and push buttons were used to simulate inputs. The outputs and inputs were displayed on the two seven segment LED displays. The accuracy of the model on FPGA was compared with simulation results obtained using MATLAB & fuzzy logic tool box. The results obtained from the two models differed with a root mean square (R.M.S.) error of 0.8%.