# FAQ: In Section 6.4 (integral action), doesn't the value of z e depend on K?

(Contributed by Richard Murray, 4 June 2009)

Q: Just before the example in Section 6.4, the text states

Note that the value of is not specified but rather will automatically settle to the value that makes , which implies that at equilibrium the output will equal the reference value. This holds independently of the specific values of , and as long as the system is stable (which can be done through appropriate choice of and ).

Doesn't this mean that the result depends on ?

A: The working here is a bit confusing. The value of will always converge to 0 (and hence as long as is chosen to be stabilizing. But it does not depend on the *specific* values of the state feedback, so perfect tracking is independent of the choice of gains (as long as the closed loop system is stable).