A comparison of shaper-based and shaper-free architectures for feedforward compensation of flexible modes

Abstract

Delay based reference shaping is a broadly used technique, very easy to implement and with good filtering properties. Guaranteeing the filtering property for input and output disturbances as well, motivated the developments of novel control architectures where delay based shapers appear in feedback loops as inverse shapers. Intuitively, one may ask to what extent the explicit inclusion of shapers is necessary, i.e., whether similar filtering properties could be induced by a suitable parameterization of the controller, which would have as additional advantage that the closed loop system would remain finite-dimensional. The aim of the chapter is to shed a light on this matter and provide answers. For this, a scheme with an inverse shaper is compared with a classical control scheme, where constraints on the location of the controller’s zeros are added in the design, in order to induce the filtering property. Both methods are presented with numerical examples, concluding with a discussion of the results. It is show, among others, that filtering is indeed possible by an appropriate controller design, but at the same time, major limitations appear, that further motivate the use of delay based shapers.nrpages: 15status: publishe