Shrinking Horizon

Figure 9.2 Shrinking horizon model predictive control (SHMPC)...

Reaction to these trends is then governed by some sort of expert system. The Shrinking Horizon Process Model developed by Joseph and Thomas (Chap. 9) uses similar concepts, but recognizes that control options decrease as the run progresses. 

This paper presents an on-line model based level control of a batch reactor with reaction rate uncertainties. The analyzed chemical batch process is catalyzed by a catalyst which decomposes in the reactor therefore it is fed several times during the batch. The chemical reaction produces a vapour phase by-product which causes level change in the system. The on-line control method is based on the shrinking horizon optimal control methodology based on the detailed model of the process. The results demonstrate that the on-line optimization based control strategy provides good control performance despite the disturbances. 

This work presents the on-line level control of a batch reactor. The on-line strategy is required to accommodate the reaction rate disturbances which arise due to catalyst dosing uncertainties (catalyst mass and feeding time). It is concluded that the implemented shrinking horizon on-line optimization strategy is able to calculate the optimal temperature profile without causing swelling or sub-optimal operation. Additionally, it is concluded that, for this process, a closed-loop formulation of the model predictive controller is needed where an output feedback controller ensures the level is controlled within the discretization intervals. 

Such an extraordinary functionality coupled with the necessary speedy response are achieved by continuously shrinking the feature sizes over time, planned and driven by the International Technology Roadmap for Semiconductors (TTRS), a roadmap that is updated every 2 years or so (the latest is available at http //www.itrs.net/) and keeping up with the dictates of the so-called Moore s law. Now devices containing functioning elements with a nominal size of 14 nm are in high volume production with even smaller sizes on the horizon. 

Russell, E., Nanotechnologies and the Shrinking World of Textiles. Textile Horizons, 2002, 9(10), 7-9. 

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