Tham khảo tài liệu 'challenges and paradigms in applied robust control part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Robust Multivariable Control of Ill-Conditioned Plants - A Case Study for High-Purity Distillation 259 The objective in this chapter is to show that acceptable closed-loop performance can be achieved for an ill-conditioned high-purity distillation column by use of the structured singular value ụ. The distillation column model used in this case study is a high-purity column referred to as column at operating point A by Skogestad and Morari 1988 . Table 1 summarizes the steady-state data of the model in detail. The following simplifying assumptions are also made for the column 1 binary separation 2 constant relative volatility and 3 constant molar flows. To include the effect of neglected flow dynamics we will add uncertainty when designing and analysing controller. Column data Relative volatility a Number of theoretical trays Nt 40 Feed tray 1 reboiler Nf 21 Feed composition ZF Operating data Distillate composition yD Bottom composition xB Distillate to feed ratio D F Reflux to feed ratio L F Table 1. Steady-state data for distillation column. 2. Process description A simple two time-constant dynamic model presented by Skogestad and Morari 1988 is chosen as the basis for the controller design. The model is derived assuming the flow and composition dynamics to be decoupled and then the two separate models for the composition and flow dynamics are simply combined. The nominal model of the column is given by V D - dL 1 _ I dV D 1 194s 1 15s 1 194s . V R --7 gĩ s dL 1--- -------- IdV. B 1 194 s 1 15 s 1 194 s gL s expresses the liquid flow dynamics gL s 1 n s n 1 2 where n is the number of trays in the column Nt - 1 . Fig. 1 shows a schematic of a binary distillation column that uses reflux and vapor boilup as manipulated inputs for the control of top and bottom compositions respectively. This is denoted as the LV-configuration structure . This structure is commonly used in industry for one-point .
