Whatever happened to fuzzy logic?

I remember back in the 1980s getting quite excited about the application of fuzzy logic to control applications. I think there was a startup company but I certainly remember speaking on the telephone with Lotfi Zadeh for an article I was writing.

Lotfali Zadeh, is the father of fuzzy logic having done most of the mathematical groundwork. He is also a classic example of western migration to Silicon Valley. He was born in Azerbaijan of Russian and Iranian parents in 1921 and went on to be an outstanding mathematician, electrical engineer, computer scientist, artificial intelligence researcher and professor emeritus of computer science at the University of California Berkeley.

I also remember how in the article I was writing I tried to explain how a double inverted pendulum could be kept upright by applying a relatively simple fuzzy logic control algorithm to the movement of the trolley on which it was balanced. Latency meant other more conventional DSP control solutions on the hardware of the day were not up to the job.

Fuzzy logic is described as many-valued logic or probabilistic logic and it deals with reasoning that is approximate rather than fixed and exact.

So rather than having an air-conditioning system that works with temperatures sensed and calibrated to the nearest degree with lots of detailed math, fuzzy logic would just work with terms such as "cold" chilly, warm and hot.

I remember that programming was usually based on IF-THEN-ELSE rules-based statements along the lines of "IF room hot THEN start fan."

But I also remember what I saw as a potential weakness of fuzzy logic, the use of membership functions to define the fuzzy variables for the given application. These were usually in the form of pseudo-Gaussian distributions, usually simplified to overlapping triangular or trapezoidal distributions.

Next: Fuzzy logic, probability both account for uncertainty