Abstract:
A road illumination system having sensors detecting approaching vehicles and operating thereupon and via a controller switches associated with street lights is provided herein. The system turns street lights off when no vehicles are present and spares thereby electricity. The system activates the street lights groupwise, to supply enough illumination with a minimal amount and complexity of equipment. The system further has an extended ability to identify malfunctioning and exceptional situations, in which is activates the street lights continuously. The system is a distributed wireless one, and may be configured remotely.

Description:
BACKGROUND 
       [0001]    1. Technical Field The present invention relates to the field of energy saving, and more particularly, to saving illumination energy. 
         [0002]    2. Discussion of Related Art 
         [0003]    Many street lamps are activated at dark time all night long. Many roads are not lighted because of high price of electricity and too thin traffic that make it unworthy. 
         [0004]    Prior art documents, such as GB 2,444,734, GB 2,455,504, BE 1,009,084, EP 2,271,184, JP 6,096,865 and US 2010/148,696 disclose various systems that aim at saving illumination energy along streets, but these systems are elaborate, expensive and sensitive to failures which may result in considerable traffic hazards. 
       BRIEF SUMMARY 
       [0005]    One aspect of the present invention provides a road illumination system comprising: at least one sensor arranged to detect an approaching vehicle on a road, a plurality of switches, each associated with a street light and arranged to switch the street light on and off, a controller arranged to receive a vehicle detection from the at least one sensor and activate, via a communication link, switches associated with a specified group of street lights for a specified period, wherein an activation speed is higher than a maximal vehicle speed, wherein the specified group comprises at least the street lights within a shorter distance between one kilometer ahead of the vehicle, and a distance between the vehicle and the vehicle&#39;s horizon; and the specified period is at least an estimated travelling period across the specified group of street lights, wherein the switch is arranged to switch the associated street light off after a specified period in which no activation signal is received from the controller, and wherein each switch is further arranged to switch the associated street light constantly on upon detection of malfunctioning of the communication link. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout. 
           [0007]    In the accompanying drawings: 
           [0008]      FIGS. 1-3  are high level schematic illustrations of various configurations of a road illumination system according to some embodiments of the invention, and 
           [0009]      FIG. 4  is a high level flowchart illustrating a road illumination method, according to some embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
         [0011]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
         [0012]      FIGS. 1-3  are high level schematic illustrations of various configurations of a road illumination system  100  according to some embodiments of the invention. 
         [0013]    Road illumination system  100  comprises at least, one sensor  120  arranged to detect an approaching vehicle  80  on a road and a plurality of switches  110 , each associated with a street light  90  and arranged to switch the street light  90  on and off. 
         [0014]    Road illumination system  100  further comprises a controller  101  arranged to receive a vehicle detection from the at least one sensor  120  and activate, via a communication link  99 , switches  110  associated with a specified group  91  of street lights  90  for a specified period, wherein an activation speed is higher than a maximal vehicle speed, e.g. at a rate higher than 5 km per second or even higher than 30 m in 6 msec. Switches  110  may receive the activation signals via antennas  105  from communication link  99 . The configuration of communication link  99  may depend on the road and terrain conditions, as well as on the distribution of sensors  120  and controllers  101  (see  FIG. 3  for some examples). 
         [0015]    Sensors  120  may be associated with each street light  90  (see left part of  FIG. 3 ), with some of street lights  90  (see right part of  FIG. 3 ), may be independent of any specific street light  90  (see  FIG. 2B ), or may associated with controller  101  (see  FIG. 1 ). All street lights  90  may be associated with switch  110 , or some of street lights  90  may be . outside system  100  and illuminate constantly as a safety measure. 
         [0016]    Sensors  120  may be arranged to only detect passing vehicles  80  or may be arranged to gather information about vehicles  80  such as speed, number or density. Sensors  120  may be arranged to detect standing (or stuck) vehicles  80 . For example, a detection distance of sensor  120  may be ten meters. 
         [0017]    The specified group  91  comprises at least the street lights  90  within a shorter distance between one kilometer ahead of the vehicle  80 , and a distance between the vehicle  80  and the vehicle&#39;s horizon; and the specified period is at least an estimated travelling period across the specified group  91  of street lights  90 . Generally, the distance is configured to allow enough driving time to light up street light  90 . 
         [0018]    Switch  110  is arranged to switch the associated street light  90  off after a specified period in which no activation signal is received from the controller  101 . Controller  101  may be arranged to switch off street lights  90  singly or groupwise (groups  91 A,  91 B,  91 C in  FIGS. 2A and 2B ) after a period with no passing vehicles, or a certain estimated distance after the last vehicle  80  has passed (e.g. 300 m). Alternatively, switches  120  may be arranged to switch associated street light  90  after a certain period in which no further activation signal from controller  101  has been received. 
         [0019]    Each switch  110  is further arranged to switch the associated street light  90  constantly on upon detection of malfunctioning of communication link  99 . For example, controller  101  may send a control signal every predefined period, and switch  110  not receiving this signal may switch the associated street light  90  constantly on. 
         [0020]    Sensors  120  may be arranged in pairs, each having a first sensor  120 A and a consecutive second sensor  120 B ( FIG. 2A and 2B ). Sensors pairs may be sequential, i.e. a next sensor pair may comprise sensor  120 B as the first sensor and sensor  120  C as the second sensor. 
         [0021]    Controller  101  is arranged to identify a detection error of first sensor  120 A by receiving a detection from second sensor  120 B without prior detection by the first sensor  120 A, and further arranged to activate street lights  90  positioned between first and second sensors  120 A,  120 B respectively, via the respective switches  110 , continuously. 
         [0022]    System  100  may comprise a single controller  101  communicating with several street light groups (groups  91 A,  91 B,  91 C) as illustrated in  FIG. 2B , or system  100  may comprise several controllers  101 A,  101 B,  101 C, each associated with group  91 A,  91 B,  91 C respectively, and optionally also with sensor  120 A,  120 B,  120 C respectively, as illustrated in  FIG. 2A . 
         [0023]    System  100  may support the further exceptional conditions: (i) Override—constant activation of street lights  90 , (ii) failure of sensor  120 —constant activation of street lights  90  in the respective segment (e.g. group  91 A in case of failure of sensor  120 A), (iii) combination of groups in case of failure of an intermediate sensor  120  (e.g. uniting groups  91 A and  91 B in case of failure of sensor  120 B, with adaptation of the specified activation period), and (iv) a stuck vehicle  80 , identified directly by sensor  120  or by a comparison of the number of vehicles passing between sensors  120  (e.g. between sensors  120 B and  120 C). In this case corresponding street lights  80  may be activated continuously. 
         [0024]    Advantageously, system  100  is designed to enable switching off street lights  90  whenever there is enough separation between road traffic to efficiency save energy. For example, in a road segment of 10 km with 300 street lights  90  positioned 30 m apart, carrying lean traffic, system  100  may allow switching off lights averaging at 4 hours a night, saving ca. 300 kWh per night. The savings can be especially high in case of street lights  90  using LED arrays for illumination. 
         [0025]    Regarding street lights  90  in proximity of sensors  120 , these would preferably be LED lamps, as they have a short period for turning on. For example, a specified number of street lights  90  after sensor  120  may be LED lamps. The specified number may be 1, 3, 5 or 10, depending on expected vehicle velocity, road conditions and illumination intensity. Specific types of lamps may be selected according to the respective position of respective street light  90  and gathered statistics. 
         [0026]    System  100 &#39;s activation of street light groups  91  is more effective as a passing vehicle requires long range illumination and is more cost effective in sparing sensors and controllers  101 . 
         [0027]    Systems  100  may further comprise a user interface  102  ( FIG. 3 ), either embedded in controller  101  or connecting to controller  101  via the Internet, that allows configuring the parameters of the usage scenario, from sensing sensitivity to partial lighting (switch off some of the street lights). 
         [0028]      FIG. 4  is a high level flowchart illustrating a road illumination method  200  according to some embodiments of the invention. 
         [0029]    Road illumination method  200  comprises the following stages: detecting approaching vehicles (stage  210 ), calculating an illumination distance (stage  220 ), activating street lights to illuminate the calculated distance (stage  230 ), controlling street lights groupwise (stage  235 ), turning off street lights behind last vehicles (stage  240 ), identifying loss of communication (stage  256 ), and operating the street light continuously upon malfunction identification (stage  260 ). 
         [0030]    Activating street lights (stage  230 ) may be carried out by communicating with the street lights via a wireless communication link (stage  237 ). 
         [0031]    Road illumination method  200  may further comprise identifying malfunctioning sensors (stage  250 ) and identifying malfunctioning switches (stage  252 ), and operating the street light continuously upon malfunction identification (stage  260 ). 
         [0032]    Malfunction identification (stage  260 ) may comprise a loss of communication, a malfunctioning of detection stage  210 , identification of a standing vehicle etc. 
         [0033]    Road illumination method  200  may further comprise configuring parameters in association with a usage scenario of method  200 . 
         [0034]    Advantageously, the communication between one or more of the sensors and the switched may be carried out by a hop-by-hop transport thereby implementing a distributed communication system that enjoys unlimited range and more robustness. 
         [0035]    In the above description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment”, “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. 
         [0036]    Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. 
         [0037]    Embodiments of the invention may include features from different embodiments disclosed above, and embodiments may incorporate elements from other embodiments disclosed above. The disclosure of elements of the invention in the context of a specific embodiment is not to be taken as limiting their used in the specific embodiment alone. 
         [0038]    Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above. 
         [0039]    The invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described. 
         [0040]    Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined.