Closed Loop System Identification Using Virtual Control Approach

The identification of closed loop systems has played an important role in the current context, since it reduces the operational costs of the identification process in the testing stage, reducing, for instance, off-spec production. However, in order to obtain the models, special care for treating the data is required. In this work, is presented a study on identification of linear models from closed loops operational data, based on the application of a virtual closed loop in the real loop. It consists of the virtual addition and removal of a controller to the analyzed loop, so as to filter the input of the system in a completely off-line procedure. This paper also propose modifications on this methodology resulting in an simplification of the virtual filter and in the ways to recover the open loop model.