PROCESS OPTIMISATION

摘要

1487193 Process optimization computations IMPERIAL CHEMICAL INDUSTRIES Ltd 5 Aug 1975 [23 Aug 1974] 37115/74 Headings G4A and G4G A method for co-ordinating the interconnections between the units of a process in order to optimize it comprises: (1) choosing a co-ordination variable p associated with the interconnection constraint defining the connections, the constraint being G 1 +G 2 ... =0, (2) using p to obtain a modified objective L for each unit, as follows: where f and G in each operating unit are dependent only on the local independent control variable or variables u, (3) for each unit, minimizing L by choosing one or more controls u such as is (are) feasible (i.e. satisfy local constraints), the controls u defining the value of G, (4) calculating the value of the interconnection error dh/dp = G 1 + G 2 + ... from the values of G derived for each operating unit and testing whether the interconnection restraint is satisfied, (5) if not satisfied, calculating the curvature d2h/d2p of h, where h is the sum of the modified objectives, i.e. h=L 1 +L 2 +..., and where the R.H. terms represent the sensitivity of the interconnections (and may be scalar products of vectors); du/dp is the sensitivity of the control choice for each control, and dG/du is the gradient of the interconnection for each control, (6) using a second-order solution technique employing the curvature and the interconnection error to obtain, in succession, a series of new values, p 1 , p 2 ... of the co-ordination variables and testing whether the interconnection constraint is satisfied and h, the sum of the modified objectives, is a maximum, and, (7) if not satisfied for p(h max.), adding a small term which is a fraction of the square of the control u and which may be expressed as #u2, when # is a small member (or expressed as #uTu if there is more than one control u, the small term being a small fraction of the sum of the square of the controls), using a second-order solution technique employing the new curvature and interconnection error to obtain, in succession, further values of p, and testing whether the sum of the new modified objectives is a maximum and the interconnection constraint is satisfied. The Specification gives details of the mathematical procedures involved which are carried out using analogue or digital computer techniques.