**7. Reference trajectory generator**

The reference trajectory generator encapsulates the required closed loop behavior as stated by the system specification-requirements. There can be two cases: the trajectory is either unknown or known in advance. The former case gives the well known pre-filter that creates the feed-forward as well. In the second case, for example, minimum time trajectories for limited acceleration or jerk, minimum acceleration or jerk energy trajectories, or any other profile can be required. Both cases are presented in (Leonhard, 1996, pp. 80, 347, 363-364, 367) and in many other publications.
