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fracred

, the next command examined, has four options—

"right 

stab"

, 

"left stab"

, 

"right perf"

, and 

"left perf"

.

The options 

"left stab"

, 

"right perf"

, and 

"left perf"

 all 

produce instability. Given the relative magnitudes of the Hankel singular 
values, this is perhaps not surprising. Figures 6-16, 6-17, and 6-18 
illustrate the results using 

"right stab"

.

Generate Figure 6-16:

svalsrol = svplot(sys*syscr,w,{radians})

plot(svalsol, {keep})

f16=plot(wc,constr,{keep,!grid,

legend=["reduced","original","constrained"],

title="Open-Loop Gain Using fracred()"})

Figure 6-16.  Open-Loop Gain Using fracred