how i have decided the values of gain connected before and after the fuzzy logic controller if the values of membership defines in the interwal of -1 to 1?

i have simulated a model of speed control of three phase induction motor using fuzzy logic controller but i am having the problem because it does not generate the correct values of output curves. i am unable to predict the values of gains connected before and after the fuzzy logic controller in the model. does anybody help me to figure out the these values??