A First Course in FUZZY and NEURAL CONTROL

156 CHAPTER 4. FUZZY CONTROL

Figure 4.16. Further tuning of membership function

The simulation results in Figure 4.17 clearly show the desired response, and
meet all the required specifications. We also notice that there is no overshoot.
The tuning of the membership functions has succeeded. This is a much improved
performance when compared to the PID controlled system.

Figure 4.17. Desired simulated results

In the above set of simulations, we used a prototype fuzzy control system
with three membership functions to describe each input variable. As such,
our control actions were rather coarse. We used ìlarge negativeî and ìlarge
positiveî values to describe the necessary control actions. While we were able
to achieve the desired simulation response, we did not consider some practical
issues such as power loss and the duty cycle of sensitive motor components. To
take into account these issues, it wouldbe wise to select intermediate ranges
of motor voltages such as ìmedium negativeî and ìmedium positiveî and use
these to gradually control the motor position. This would reduce the amount
offine tuning as we have seen in the example, and provide afiner granularity
in the control actions. Notice that if you increase the membership functions to