Yeast produce acetic acid, it is just that it is usually not detectable in the flavor as such. The presence of acetic acid is the primary cause of chronological aging and cell death in long term yeast storage.
To clarify, even unhealthy yeast don't produce acetic acid at noticeable
levels, in the same way that an acetobacter infection would produce.
Unless you've got a lot of air contact with your beer and you're leaving your beer for long periods of time, I'm not sure that you've actually got an acetobacter infection.
"Cidery" notes can be produced by yeast. Ethyl acetate is one of the most common esters in beer and it smells like ripe apples, while acetaldehyde smells like unripe/green apples. Both are byproducts of fermentation. At low levels, "cidery" notes can be confused with apple cider "vinegary" notes.
The way to determine if you're got acetobacter infection (true "vinegary" notes) vs. just "cidery" notes is to bottle some of your beer and let it age. If the "vinegar" notes get stronger with aging, the beer's body goes down and the carbonation level goes up, you've actually got an infection. If the "vinegar" notes dissipate with age, it's probably just normal fermentation byproducts.
If you actually have an acetobacter infection, other folks have given you good advice on sanitation and excluding O2.
If you have acetaldehyde and/or estery notes, that's more likely to be a problem with "yeast management." Quick fixes are to pitch more yeast and to aerate your wort just after pitching your yeast (vigorously stirring or rocking your wort for about 10 minutes is the low-tech version of how to solve this problem).