The present invention relates to a system and method for controlling the light intensity in a tunnel according to the appended claims.

The state of the art on road tunnels and underpass illumination systems is bound to open-loop control of the illumination level based on a single parameter (time of day or external illumination level or veil luminance). Ambient characteristics are taken into account only statically based in the project and dimensioning of the plant. Samples of these systems are: Reverberi SDL TC veil luminance sensor, Techno Team Video Photometer, Thorn North Star Lighting, US 2004160199, GB2345998 and FR 2490363.

International and national regulations for the illumination of road, tunnels, underpasses, and other similar infrastructures impose strict limits in terms of the luminance and contrast perception for drivers and users. Applicability goes beyond tunnels and roads and can be extended to any situation where the security, safety, or simply comfort of use, require well-defined luminance levels. Energy consumption may or may not be a primary concern, but the strict adherence to rules (in contrast to over-dimensioning) of the proposed system guarantees energy consumption minimization.

The present illumination system is composed of six main functional blocks as illustrated in Fig. 1. The core and innovation of the system are in Internal Measures, Controller, and in part in External Measures.

The External Measures block includes a set, possibly with a single component, of measurements performed outside the area of controlled illumination, which are related to the specific ambient and scope of the illumination. Such measures can include luminance measurement, traffic measures (for roads), weather and physical environment conditions, etc. Based on these measurements the Reference Definition block computes a reference set point (which is indeed a complex curve function of time and space) for the illumination.

The Lamps block is a set of illumination devices. It is possibly heterogeneous and can include natural illumination sources (such as light wells collecting and regulating the flow of sunlight) and artificial illumination sources such as incandescence lamps, LEDs, and in general any light-emitting device. The Actuators block includes means for regulating the light flow of the devices in the Lamps block. Actuation techniques may operate on single illumination devices or groups thereof. Regulation techniques include, but are not limited to: 1) switching on and off illumination devices; 2) changing the driving voltage or current; 3) changing the duty-cycle of current; 4) screening the light source.

The Internal Measures block is a complex ensemble of functions which include: 1) measuring one or more of the following quantities: luminance, illumination, temperature, infrared radiation, ultraviolet radiation, reflectivity of walls, floor and ceiling; 2) collecting and transmitting the above measures to one or more collection points called gateways; 3) elaborating and normalizing such information and measures; 4) communicating periodically or asynchronously the measures and information to the Controller.

The Controller block is a hardware device with computational capabilities that, based on a suitable algorithm, can regulate the actuators such that the actual illumination parameters as measured by the Internal Measures block do not differ from the said reference set point by more than a predefined quantity. The algorithms used by the Controller may include robust and optimal control theory techniques, heuristic adaptations and neural networks or other artificial intelligence techniques suitable to minimize the residual error between the reference set point and the actual measures.

1. 1) The concept of gathering external measures of different kinds, as discussed above with respect to the External Measures block, is an improvement on the state of the art, which typically relies on a single kind of measurement. Present day systems for road tunnels use a camera-based sensor to identify the screen luminance; in other applications the illumination in some other key point is measured. Other systems simply use the time of day without any measurement. Our system can use single as well as multiple measures, enabling a computation of the reference set point based upon multiple parameters. Additional measures can be, but are not limited to:
   1. a) presence of traffic;
   2. b) traffic speed and/or density;
   3. c) hazardous conditions like stalling traffic into a tunnel or ongoing security activities in other environments;
   4. d) modified ambient conditions that alters the reaction of drivers (e.g., snow, rain, fog).
2. 2) The dynamic setting of the reference set point, either done with a continuous algorithm or with a tabular function. In state-of-the-art systems the set point is not a reference, rather a working consequence of the actuators settings, which are computed off-line at design time.
3. 3) The fine-grained control of illumination devices both in light level and in space, with the ability of compensating illumination in one point by properly regulating adjacent lamps.
4. 4) The closed loop control of illumination based on a dense set of measures internal to the controlled system, which can control the entire and can drive it to the reference set point with a controllable error.