**8. Discussion**

In this chapter the generalized PID controllers for 1st and 2nd order system that are able to drive the tracking error to zero for up to second order polynomials inputs and disturbances have been derived. This presented in detail a methodology to derive additional members of the family of generalized PID controllers for high order system (Rusnak, 1999) and high order polynomial inputs and disturbances. These are the PImDn-1 controllers.

Following the theory and the author's experience the full state feedback, especially the cascade architecture, Figure 2, is preferable over the one block controller, Figure 3. This may come at the expense of higher cost. However in modern digital control loop that are using absolute or incremental encoders the position and velocity information is derived at the same cost.

The motion control engineers prefer the cascade controller because of implementation and tuning easiness. The most important feature is that in the cascade architecture the feedback loop can be tuned sequentially. That is, start with the velocity-inner loop, that is usually high bandwidth, and then to proceed to the position-outer loop. The same apply to higher order generalized PID controllers.
