Part 1Fuzzy logic controller

A water level control system uses fuzzy logic. The inputs are the water level, L, and the rate of change of water level, R, which indicates if the water level is going up or down. The level is controlled by a valve which can be opened or closed. The inputs have been made fuzzy using the membership functions shown in Figure6.

Water level:0 to 100% - low, ok, high (Ll, Lo, Lh).

Water level Rate of change:-100% to +100% - negative, zero, positive (Rn, Rz, Rp).

Valve:-100% to +100% - open quickly, open slowly, do nothing, close slowly, close quickly (Voq, Vos, Vdn, Vcs, Vcq).

membership Low membership, LI OK membership, Lo High membership, Lh 1 50 100 Level (%) (a)1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 0 10 20 30 40 50 0 20 40 60 80 100 (a) (b) Figure 7a and b Triangles to aid with the calculation of the membership functions