25 Pages

 t =   

By(8.22) (8.23)

The interaction bounds (the optimal bounds for a pure regulator control system), representing the cross-coupling and the external disturbance effects, are calculated at a given frequency to satisfy

i k and 2 1, = i where 1

+ ) (1

= )B( i

+ ≥

p Lq


t (8.33)


and 2 1, = where + ) (1


1 1

≠ +

≥+ p Lq

qpL qg (8.34)

The improved QFT method uses these equations to reduce the over-design inherent in the original design process. The order in which loops are designed is important as pointed out in Chapter 7. Any order can be used, but some orders produce less over-design (less bandwidth) than others. The last loop designed has the least amount of over-design, therefore the most constrained loop is done first by Method 1. Then the design is continued through the remaining loop by use of Method 2. As a second iteration, the first loop is then redesigned using Method 2.