CLOSED-LOOP IDENTIFICATION - A 2-STEP APPROACH

The accuracy aspects of identification (with respect to both variance and bias of estimates) and the role of filtering in closed-loop identi fication is discussed in this paper. It is shown that the key differen ce between closed-loop and open-loop identification is the existence o f the sensitivity function. A closed-loop identification algorithm whi ch asymptotically yields the same expressions as open-loop identificat ion, in both variance and bias errors, is proposed. The proposed algor ithm is evaluated by simulated examples as well as experiments perform ed on a computer-interfaced pilot-scale process. (C) 1997 Elsevier Sci ence Ltd.