Design of a Visual Comfort Sensor for Daylighting Devices M. Leclercq*, C. Anthierens**, E. Bideaux*, L Flambard*** * Laboratoire AMPERE UMR 5005, Institut National des Sciences Appliquées, Lyon, France (m.leclercq@sherpa-eng.com; eric.bideaux@insa-lyon.fr) **Institut des Sciences du Mouvement UMR 6233, Luminy, Marseille, France (cedric.anthierens@supmeca.fr) *** Sherpa Engineering, La Valette du Var, France (l.flambard@sherpa-eng.com). Abstract: This paper reports one task of a global investigation based on a whole daylighting system designed to equip refurbished and new buildings. This study forms part of the research conducted by a French group that works on green energy. The authors aim to provide occupants with daylight for everyday tasks, hence reducing electricity consumption and increasing comfort level as well. This paper presents the conception and design of a new virtual sensor based on a fisheye video camera dedicated to the assessment of optic comfort. This device includes a fuzzy logic kernel to deal with the subjective aspect of the human perception related to sight. 1. INTRODUCTION Many companies financially encouraged by their government to meet the Kyoto treaty and to decrease their energy bill, have decided to invest in new premises or refurbishments (Barlow 2007) to achieve a long-term solution. In the tertiary companies lighting and heating represent the majority of the energy consumption, which is why many companies in this field are now tempted to rely more on natural solar energy as this can supply the light and heat required. Not including the benefits of solar heating in terms of energy savings, the use of daylight can significantly help to decrease energy consumption and is also interesting thanks to its light quality. The spectrum of sun light is very wide and provides a high power density over the whole range of visible frequencies. Therefore daylight allows us to see the true colours of our environment. Moreover when the sky is clear, the heat from sun light is high and can generate a natural comfort of sight. Humans are sensitive to surrounding light conditions and when comparing identical illumination conditions very much prefer daylight sources to artificial lights. Several criteria such as the amount of light, location of the source, heat of light etc can even affect workers’ productivity and stress levels (Vischer 2005). Despite all the advantages of daylight (energy savings or light comfort), this free source of light can also cause trouble in all buildings that do not have the equipment to deal with it. The main drawback of daylight compared to artificial light is its perpetual variation. It varies with the seasons (altitude of sun and daylight duration), time (trajectory of sun between sunrise and sunset), weather (overcast or clear sky) and environment (reflection on water or snow, presence of a building…). Several of these criteria cannot be predicted with good reliability. However, architects try to design new buildings by taking into account their orientation, the occurrence of shadows and some other basic criteria related to the local climate (Serra 1998). Section 2 of this paper will deal with visual comfort and discomfort criteria such as glare and backlighting. Our contribution on a fuzzy optic comfort sensor is presented in the third section, from sensor conception and design to implementation. Section 4 will locate and define the role of our sensor within a control loop, which would manage the visual comfort in the experimental room. The last section will draw conclusions from the current results and introduce the forthcoming advances for the control of the whole experimental room. 2. OPTIC COMFORT Many investigations have been conducted to model what we could call human optic comfort, which involves taking into account individual subjectivity to assess the comfort level. Because our behaviour tends to follow a daily biological rhythm, our comfort perception is supposed to evolve during the day. As it is described in work standards, the optic comfort level depends on the task being performed. This is why in a company the lighting in a corridor (walking hall) should be very different to the lighting of a workbench where a worker is concentrated on a microscopic task. In order to meet optic comfort criteria, we shall take into account the environment (material and people) and the task at hand in order to define the notion of optic atmosphere. Optic comfort does not depend only on the level of light because, as we have seen above, the light temperature has an influence on the way we visually perceive our environment. Instead of describing and controlling all the criteria that lead to optic comfort according to a desired atmosphere, we can note some criteria of discomfort that it is necessary to avoid in order to tend towards a good level of optic comfort in any case and thus for any task. Glare, backlighting, shadows, Proceedings of the 17th World Congress The International Federation of Automatic Control Seoul, Korea, July 6-11, 2008 978-1-1234-7890-2/08/$20.00 © 2008 IFAC 6873 10.3182/20080706-5-KR-1001.1025