Authors: Wu, J.¹; Chen, S.²; Li, G.³; Chu, J.¹

Source: International Journal of Control, Volume 79, Number 10, October 2006 , pp. 1297-1312(16)

Publisher: Taylor and Francis Ltd

Abstract:

A novel approach is proposed to design optimal finite word length (FWL) realizations of digital controllers implemented in fixed-point arithmetic. A minimax-based search procedure is first formulated to obtain an optimal controller realization that optimizes an FWL closed-loop stability measure. Since this FWL closed-loop stability measure is solely linked to the fractional part or precision of fixed-point format, the resulting realization may not have the smallest dynamic range. A measure is then derived to indicate the dynamic range of fixed-point implemented realization. By choosing an appropriate orthogonal transformation of this dynamic range measure of the optimal precision controller realization, a numerical optimization method is developed to make the controller realization having the smallest dynamic range without sacrificing FWL closed-loop stability robustness. The proposed approach is more efficient than a direct optimization of some combined FWL closed-loop stability and dynamic range measure via a numerical means. The proposed approach is established within a unified framework that includes both the shift and delta operator parameterizations, which makes it possible to compare the closed-loop stability characteristics of the optimal FWL controller realizations using shift and delta operators, respectively. Through analysing the simulation results of a design example, some useful insights and understandings are obtained regarding the FWL controller realizations based on shift and delta operators.

Document Type: Research article

DOI: http://dx.doi.org/10.1080/00207170600833257

Affiliations: 1: National Key Laboratory of Industrial Control Technology, Institute of Advanced Process Control, Zhejiang University, Hangzhou, 310027, P.R. China 2: School of Electronics and Computer Science, University of Southampton, Highfield, Southampton SO17 1BJ, U.K. 3: School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore

Publication date: 2006-10-01

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