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Al~trKt-The paper presents results on frequency-dependent tools for analysis, structure selection and design of control systems. This includes relationships between the relative gain array (RGA) and right half plane zeros, and the use of the RGA as a sensitivity measure with respect to individual element uncertainty and diagonal input uncertainty. It is(More)
This paper deals with the optimal selection of linear measurement combinations as controlled variables, c 1⁄4 Hy. The objective is to achieve ‘‘self-optimizing control”, which is when fixing the controlled variables c indirectly gives near-optimal steady-state operation with a small loss. The nullspace method of Alstad and Skogestad [V. Alstad, S.(More)
Control structure design deals with the structural decisions of the control system, including what to control and how to pair the variables to form control loops. Although these are very important issues, these decisions are in most cases made in an ad hoc fashion, based on experience and engineering insight, without considering the details of each problem.(More)
Real-time steady-state optimization (RTO) has become increasing popular in recent years. But how should this optimal policy be implemented in the control system? It is argued that the goal is to find a set of controlled variables which, when kept at constant setpoints, indirectly lead to near-optimal operation with acceptable loss. This is denoted(More)
The purpose of this paper is to stress the importance of selecting the right plantwide control structure and the need for a formalized approach that can encompass the many issues that arise in plantwide control design. Since the concept of process control design based on a holistic view of the process came about, the variety of procedures and approaches to(More)
This paper considers the selection of controlled variables for the unconstrained degrees of freedom, such that near-optimal operation is achieved with constant setpoints (“self-optimizing control”). From a second-order Taylor approximation around the optimal point, we derive an exact local method. This may be used to find the optimal linear combination of(More)
Decentralized control systems have fewer tuning parameters, are easier to understand and retune, and are more easily made failure tolerant than general multivariable control systems. In this paper the decentralized control problem is formulated as a series of independent designs. Simple bounds on these individual designs are derived, which when satisfied,(More)