Reference Point Approaches and Objective Ranking

The paper presents a reflection on some of the basic assumptions and philosophy of reference point approaches, stressing their unique concentra-tion on the sovereignty of the subjective decision maker. As a new devel-opment in reference point approaches also the concept of objective ranking is stressed, defined as dependent only on a given set of data, relevant for the decision situation, and independent from any more detailed specifica-tion of personal preferences than that given by defining criteria and the partial order in criterion space. Rational objective ranking can be based on reference point approach, because reference levels needed in this approach can be established objectively statistically from the given data set. Exam-ples show that such objective ranking can be very useful in many man-agement situations

Model-Assisted Online Optimization of Gain-Scheduled PID Control Using NSGA-II Iterative Genetic Algorithm

In the practical control of nonlinear valve systems, PID control, as a model-free method, continues to play a crucial role thanks to its simple structure and performance-oriented tuning process. To improve the control performance, advanced gain-scheduling methods are used to schedule the PID control gains based on the operating conditions and/or tracking error. However, determining the scheduled gain is a major challenge, as PID control gains need to be determined at each operating condition. In this paper, a model-assisted online optimization method is proposed based on the modified Non-Dominated Sorting Genetic Algorithms-II (NSGA-II) to obtain the optimal gain-scheduled PID controller. Model-assisted offline optimization through computer-in-the-loop simulation provides the initial scheduled gains for an online algorithm, which then uses the iterative NSGA-II algorithm to automatically schedule and tune PID gains by online searching of the parameter space. As a summary, the proposed approach presents a PID controller optimized through both model-assisted learning based on prior model knowledge and model-free online learning. The proposed approach is demonstrated in the case of a nonlinear valve system able to obtain optimal PID control gains with a given scheduled gain structure. The performance improvement of the optimized gain-scheduled PID control is demonstrated by comparing it with fixed-gain controllers under multiple operating conditions

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The problem of objective ranking: foundations, approaches and applications, Journal of Telecommunications and Information Technology, 2008, nr 3

The paper starts with the discussion of the issue of objectivity versus subjectivity, stressing that while an absolute objectivity is not attainable, nevertheless trying to be as objective as possible constitutes a higher value, necessary for hard science and technology. Dangers and errors of the subjectivist reduction of objectivity to power and money attempted by the postmodern sociology of science are discussed. Then we turn to the problem of subjective versus objective decision analysis and ranking. It is shown that while all classical decision theory aims at a rational analysis and support of subjective decisions, there are important application cases, particularly in managerial problems, when the decision maker prefers to avoid specifying her/his preferences and needs decision analysis – e.g., ranking of decision options – that is as objective as possible. An approach to decision support that might be easily adapted for such objective ranking is the reference point methodology; its application is shown on examples. One of these examples is actually not an application of the methodology, but a real life problem that motivated the development of objective ranking. The examples illustrate that objective ranking might be important for management, including also management of telecommunication networks

Discrete Decision Problems with Large Number of Criteria

Discrete decision problems with a large number of criteria (as compared to the number of alternatives) present specific difficulties, for example, most of decision alternatives tend to be Pareto-nondominated, some criteria might have binary character, etc. For these reasons, classical methods such as weighted sum aggregation or full utility elicitation are barely applicable for such problems. Methods that might be applied include reference point approaches, particularly if appropriately modified, equitable aggregation approaches and special hierarchical aggregation schemes. The paper presents descriptions and necessary modifications of such methods, together with associated concepts of objective versus subjective decision selection, compensatory versus non-compensatory criteria, preservation of Pareto-nondominance in hierarchical aggregation, etc. Examples show that methods effective in most difficult cases are based on reference point approaches combined with equitable aggregation and objective decision selection

Journal of Telecommunications and Information Technology, 2008, nr 3

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