Patent Application
20080104871
None.
The present invention relates generally to the field of variable message signs and more particularly to a variable message sign control system.
Variable message signs are used on roadways to inform motorists of hazards and traffic conditions. Each variable message sign has a controller that has a direct communication link to a central office or central controller. Often the direct communication link is a fiber optic link, which is expensive to install and requires an expensive fiber modem. In addition, the direct communication link requires an overhead intensive communication protocol such as NTCIP (National Transportation Communication for ITS [Intelligent Transportation Systems] Protocol). In addition, each of these direct communication links and its associated hardware are potential failure points as is each of the controllers.
Thus, there exists a need for a sign controller system that is less expensive to install and operate and increases the reliability for variable message signs.
A variable message sign control system that overcomes these and other problems includes a plurality of variable message signs. The plurality of variable messages signs are coupled by local communication links to a sign controller. This single sign controller takes the place of multiple sign controllers in previous designs. The local communication links use low cost, overhead efficient protocols and physical layers such as wireless Ethernet protocols. The single sign controller has a single communication link to the central office. This reduces the cost and overhead compared to the multiple sign controllers and further reduces the cost compared to multiple separate ground or pole mounted control cabinets.
The invention is a variable message sign control system that includes a plurality of variable message signs. The plurality of variable messages signs are coupled by local communication links to a sign controller. This single sign controller takes the place of multiple sign controllers in previous designs. The local communication links use low cost, overhead efficient protocols and physical layers such as wireless Ethernet protocols. The single sign controller has a single communication link to the central office. This reduces the cost and overhead compared to the multiple sign controllers. The communication link to the central office may also have two communication links. One of these links may be a backup link.
The variable message signs 56, 58, 60 all have a communication interface (WI) 70. A display driver 72 of the variable message signs 56, 58, 60 controls the display 74. Each variable message signs 56, 58, 60 also has an environmental driver 76. Note that a sign driver includes a display driver 72 and an environmental driver 76.
In operation the central office 46 determines the message each variable message sign 56, 58, 60 should display. This information is transmitted over the central office communication link 44 to the sign controller 42. The sign controller 42 schedules each message for display on the appropriate variable message sign 56, 5860. The message to be displayed is transmitted from the sign controller 42 to the appropriate variable message sign 56, 5860 over a local communication link 50, 52, 54. The display driver 72 then drives the display 74. The display driver 72 determines a brightness of each display element based on a number factors including the ambient light. The display driver 72 reads the display output, by determining an amount of power each display element is consuming. A picture or representation of the displayed message is transmitted to the sign controller 42. This information is forwarded to the central office 46. The environmental drivers 76 monitor a number of environmental conditions including: internal temperature of the sign; external temperature; humidity; ventilation air flow amounts; power supply status, etc. These measurements are used to construct an environmental status message that is transmitted to the sign controller 42. The sign controller 42 forwards the environmental message to the central office. In addition, the environmental driver 76 may turn on or off a fan, or advance a filter material based on these measurements.
This system 40 eliminates the need for multiple sign controllers, multiple expensive communication links to the central office and reduces the number of potential failure points. It also eliminates multiple ground or pole mounted cabinets if the sign controller is not located in the sign. Thus there has been described a variable message sign control system that is less expensive to install and operate and increases the reliability for variable message signs.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alterations, modifications, and variations in the appended claims.
