Fuzzy logic is useful for appliances. Let's say your dryer knows the humidity and temperature of incoming and outgoing air and approximately how dry you want your clothing, and how long it's been running. At what point should it turn off? Now, let's add it has various sensors that have some level of accuracy which you can extrapolate by how effective the device is at drying clothing at a given temperature and humidity.
Now you could setup a wide range to test cases with various loads, temperatures faulty sensors etc. Or you can figure out a reasonable approximation by hand based on Fuzzy logic and ship it.
Note: your solution must run on a 4bit 32khz cpu with 400 bytes of ram.
Fuzzy logic can be useful when combined with a frequentist distribution for doing natural language processing (e.g. how many people would refer to someone at height X as "tall"?).
It's really just a special case of Bayesian inference: p(A calls B "tall" | B is a 6'1 man) is a combination of what you know about who is called tall in general and what you know specifically about who A thinks is tall. Unfortunately, for some reason many linguists don't like thinking in these terms, so it is easier to communicate with them using fuzzy logic vocabulary than Bayesian inference.
It's really just a special case of Bayesian inference: p(A calls B "tall" | B is a 6'1 man) is a combination of what you know about who is called tall in general and what you know specifically about who A thinks is tall.
As far as I know, thats not true. Fuzzy logic is meant to encapsulate the idea that someone is "sort of" tall.
I believe fuzzy logic, or something similar, is used in some handwriting recognition software. E.g. as you are looking at a letter, you start with "This letter is an A" as having value 1/26, etc... and start to change them as you look at it. In this case its very similar to probability. I'm not sure of any other uses.
However, I remember reading studies that seemed to indicate that apes/chimps use fuzzy logic. I don't remember who wrote it or how they tested it, but it seemed fairly convincing at the time.
So, I guess I'd say its not so useful now (at least not as an independent concept) but if its true that humans use it, it might become useful in the future.
In the end though, fuzzy logic isn't going to solve your problems for you, at least not alone. The way you use the fuzzy logic is going to be much more important.
Or, as jey said, you can actually use probabilities to control your appliance, and then have a lot of theory behind your inference process. i.e. not something ad hoc, like fuzzy logic, which can ultimately be transformed into probabilities regardless.
Fuzzy logic is not about creating actual intelegence just a quick and dirty aproach that happens to be useful. When selling bread makers you are vary limited in your development budget and the HW you send to people. So yea it's overly simple add hock solution but it's also cheap.
There is a lot of theory behind fuzzy logic as well and you get the bonus of it being very simple to implement. Thus it's use in appliances where cheap/tiny processors are the norm.
Now you could setup a wide range to test cases with various loads, temperatures faulty sensors etc. Or you can figure out a reasonable approximation by hand based on Fuzzy logic and ship it.
Note: your solution must run on a 4bit 32khz cpu with 400 bytes of ram.