Tham khảo tài liệu 'recent advances in robust control theory and applications in robotics and electromechanics part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | LMI Robust Control of PWM Converters An Output-Feedback Approach 319 a Buck converter with stray resistances. b t rL iL t ị rc vc c L b Buck-boost converter with stray resistances. Fig. 3. Schematic of the buck and the buck-boost converter. following strategies. First the classic dynamic output-feedback control problem is treated. This approach can be carried out with a change of variables as in Scherer et al. 1997 . However with such an approach the uncertainty must be modeled with elaborated models as for example weighting functions Wallis Tymerski 2000 . Therefore the chapter also proposes the synthesis of output-feedback controllers based on the static case. Both the static output-feedback and a parametrization Peaucelle Arzelier 2001b to deal with dynamic output-feedback are considered. The advantages and drawbacks of the three approaches shown in the chapter will be discussed and the results will be compared. Notation For symmetric matrices A and B A B means that A B is positive definite. A denotes that the matrix A is an unknown variable. A denotes the transpose of A. Co IVj j 1 . NI denotes the convex hull defined by N vertices Vj 6 R . The identity matrix of order n is noted as 1 and the null n X m matrix is noted as 0 n m. The symbol denotes symmetric blocks in partitioned matrices. 2. Modeling of uncertain dc-dc converters This subsection shows the state-space averaged models of the buck and the buck-boost converters of Figures 3 a and 3 b . The models are assumed to operate in Continuous Conduction Mode CCM . the inductor current is always larger than zero. Besides of the averaged models this section also introduces a model of the sampling effect caused by the PWM. Finally at the end of the section the uncertainty modeling of dc-dc converters is discussed and a simple example is shown. Model of the buck converter The first model that is introduced considers a buck converter which is characterized by linear averaged control-to-output dynamics. As