Effect of model, system and controller order on adaptive control

In adaptive control, 3 orders are relevant. These are the system order, model order and controller order. In much of control theory and identification, the system and model orders are assumed to be equal. However, in principle, it would be possible to independently assign the order of the system, model and controller. This paper discusses the rationale behind such an assignment and the resulting implications. A new result on adaptive control of non-mimimum phase systems will also be presented.