From: NOSPAM_b.postlethwaite@strath.ac.uk   
      
   My interest is mainly in model-based control, but I've played with   
   rule-based controllers too.   
      
   1. Fuzzy logic is only really worth thinking about if you have significant   
   non-linearity in the control problem. If the system you are controlling is   
   pretty much linear, then you will get to an acceptable controlled response   
   quicker and easier using standard linear controllers (like PID). Note that   
   even some very non-linear systems, like pH control, can be successfully   
   handled using standard PID controllers if the range of variation in the   
   system isn't too large (the gains stay pretty much the same in the region of   
   interest). Where fuzzy logic is really useful, and this is the area I'm   
   interested in, is when you have a multivariable non-linear system to   
   control.   
      
   2. In a non-linear application fuzzy control can give good performance   
   across the whole range of operation. A PID controller will give good   
   performance in the region it is tuned for, but will break down as the system   
   moves away from this point. This can, of course, be dealt with in many cases   
   by gain scheduling, and this is often easier to do than setting up a fuzzy   
   controller.   
      
   Bruce   
      
    wrote in message   
   news:1138876028.502813.187010@z14g2000cwz.googlegroups.com...   
   > Hi All.   
   > I've recently developed two fuzzy logic controllers for my workplace.   
   > They work well, but some people are still not convinced it's for us.   
   > Since I'm new to FL (and controls in general) I don't have answers for   
   > the skeptical.  The company I work for has applications used in   
   > irrigation, that control electroconductivity and pH levels, and we are   
   > considering using FL to control temperature/cooling.  Here are the   
   > questions:   
   > 1. Which kind of applications are especially suited to fuzzy logic, and   
   > which are not?   
   > 2. How does FL compare with PID, as far as obtaining the target value   
   > quickly with a minimum of overshoot and minimal steady state error?   
   > Thanks,   
   > Sally   
   >   
      
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