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Time-Discretization of Time Delayed Non-Affine System via Taylor-Lie Series Using Scaling and Squaring Technique

Yuanliang Zhang and Kil To Chong*
International Journal of Control, Automation, and Systems, vol. 4, no. 3, pp.293-301, 2006

Abstract : A new discretization method for calculating a sampled-data representation of a nonlinear continuous-time system is proposed. The proposed method is based on the well-known Taylor series expansion and zero-order hold (ZOH) assumption. The mathematical structure of the new discretization method is analyzed. On the basis of this structure, a sampled-data representation of a nonlinear system with a time-delayed input is derived. This method is applied to obtain a sampled-data representation of a non-affine nonlinear system, with a constant input time delay. In particular, the effect of the time discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. ‘Hybrid’ discretization schemes that result from a combination of the ‘scaling and squaring’ technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. Practical issues associated with the selection of the method parameters to meet CPU time and accuracy requirements are examined as well. The performance of the proposed method is evaluated using a nonlinear system with a time-delayed non-affine input.

Keyword : Non-affine, nonlinear system, scaling and squaring technique, stability, Taylor series, time delay, time discretization.

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