Indoor illuminance selection procedure using fuzzy techniques

Abstract

The current practice of selecting target illuminance based on the recommendations of the Illuminating Engineering Society has serious shortcomings. For example, the visual age of the observer has precise boundaries, the illuminance values are exact instead of an acceptable range, and the sudden increase of illuminance values with age is rather arbitrary. To come up with an exact output from an input that is, by its very nature, uncertain and imprecise is virtually impossible. The aim of this work is to develop an approach that overcomes the limitations of the current illuminance selection method. This work proposes an alternative method for illuminance selection based on Fuzzy techniques. Fuzzy techniques are approximations used to model phenomena or decisions for which mathematical precision is impractical. The vagueness and uncertainties of many lighting design variables suit Fuzzy logic modeling, whereby a crisp output can be obtained from a range of Fuzzy input variables. The new method involves visual age, task difficulty and task importance as input variables which lead to a target illuminance. The target illuminance is given the name “Fuzzy Illuminance” (FILL). A MATLAB digital application was developed and can be used by lighting designers. It is expected that the proposed technique and the digital application will not only resolve the limitations of the current illuminance selection procedure but will also simplify the process of the selection of illuminance design targets and on-site verification of such design targets.