Illumination system with distributed intelligence

FIELD OF THE INVENTION

The present invention relates in general to the field of lighting. More particularly, the present invention relates to an illumination system with a plurality of light source units, each unit comprising a dedicated controller with intelligence, and with a central controller giving command signals to the light source units, the system being capable of producing light with variable color.

BACKGROUND OF THE INVENTION

Illumination units for producing light with a variable color, such as to for instance illuminate a space, are generally known. Figure 1 schematically illustrates an illumination unit 100 of known design, comprising a light source 102, a driver 101 for driving the light source 102, and a local controller 110 for controlling the driver 101. The controller 110 and driver 101 may also be integrated. The light source 102 is capable of generating light with variable color within a color space. In a typical example, such light source comprises a plurality of monochromatic light units, each monochromatic light unit emitting light with a specific color, the respective colors of the different light units being mutually different. The overall light generated by the light source as a whole is then a mixture of the light emitted by the several monochromatic light units. By changing the relative intensities of the different monochromatic light units, the color of the overall light mixture can be changed. The monochromatic light units can be of different type, such as for instance TL lamp, halogen lamp, LED, etc.

Since systems for producing light with variable color are known per se, a more detailed description and explanation of its design and functioning is omitted here. However, the following is observed. In the case of a light source comprising a plurality of monochromatic light units, it is possible that there are light units producing the same color, in order to increase if necessary the intensity at this color. It is further possible that one driver may drive two or more light sources in parallel. It is further possible that each controller 110 may control two or more drivers.

Varying the color of illumination is for instance used in homes, restaurants, conference rooms, streets etc to create a comfortable colored atmosphere, or is for instance used in shops etc to create lighting adapted to the colors of displayed product. The chosen color may be stationary, but it is also possible that the colors are varied in order to achieve a certain pleasant, interesting and/or artistic impression with the observers.

In the case of illuminating a relatively large space, a relatively large number of light sources are needed. This may be implemented by having one controller for controlling a plurality of driver/light source combinations, but such solution has drawbacks. If the drivers would be coupled to the controller by control wires, these wires and their installation are quite costly. If the drivers would be coupled to the controller by a wireless communication network, problems are expected regarding reliability, the problems for instance being caused by signal interference, bad reception, data collision, etc, and the potential problem of neighboring systems interfering with each other. Further, if battery powered repeater nodes are used, intense data traffic may exhaust the batteries too quickly.

A system design which avoids or at least reduces these problems is illustrated in figure 1. The figure illustrates an illumination system 1 comprising a plurality of illumination units 100 coupled to a central controller 2 via a communication network 3. The communication network 3 may be wired but is preferably wireless, for instance RF, Zigbee, etc. Each illumination unit 100 has a design as described above, including its local controller 110; in view of the fact that each illumination unit 100 has its own intelligence embodied by its dedicated local controller 110, this feature is indicated as "distributed intelligence". Each controller 110 is provided with a scenario memory 111, for storing data defining a color scenario, which in general means color and intensity as a function of time.

As should be clear to a person skilled in the art, the color of light can be represented by coordinates of a color point in a color space. In such representation, changing a color corresponds to a displacement from one color point to another color point in the color space, or a displacement of the setting of the color point of the system. Further, a sequence of colors corresponds to a collection of color points in the color space, which collection will be indicated as a color path. Dynamically changing the colors can then be indicated as "travelling" such path. More in general, dynamically changing the colors of lighting will be indicated as "navigating" through the color space. The color scenario may be defined as a collection of consecutive color points, but may also be defined as a function describing the color path in combination with light output intensity and in combination with travel speed, which travel speed may be constant but may also depend on position along the path.

Preferably, but not essentially, the color space is defined in terms of hue H, saturation S, brightness B.

The system 1 is capable of operating in two operative modes. A first mode will be indicated as TEACH/LEARN mode. In the TEACH/LEARN mode the central controller 2 communicates to the individual local controllers 110 of the various illumination units 100 data defining the color scenarios, and the local controllers 110 store these data into their associated scenario memories 111. It is noted that it is possible that all color scenarios are identical, but it is also possible that different local controllers 110 receive different color scenarios. It is further noted that the central controller 2 may receive instructions relating to the color scenarios from a User Interface UI, which may be any suitable type of user interface.

A second mode will be indicated as EXECUTE mode. In the EXECUTE mode, each local controller 110 operates autonomously, independently from all other local controllers, to control its associated driver 101 such as to execute the color scenario stored in its associated scenario memory 111, by reading the data from said memory 111.

Thus, the data traffic over the communications network 3 is basically confined to the TEACH/LEARN mode. In this case, the data speed will hardly be an issue, and the central controller may communicate to the local controllers at a relatively low data rate. If data errors occur, there may be protocols for detecting and correcting such errors. Loading the scenario data into the units 100 may be done well in advance. On the other hand, in the EXECUTE mode the execution of the desired scenarios does not depend on data traffic over the communications network 3.

US-2005/0.275.626 discloses an illumination system having a plurality of lighting units, each comprising a local controller and a memory, and further having one or more central controllers. On receiving a certain command signal, the local controller controls its associated light sources on the basis of information in its memory.

US-2006/0.132.065 discloses an illumination system having a plurality of lighting units, each comprising a local controller and a memory, and further having one master controller. The memory comprises at least one script, for instance defining a dimming from 100% to 0% in a predetermined time interval. On receiving one dimming command, the controller selects the corresponding script and autonomously dims the associated light source steadily during the predetermined time interval.

SUMMARY OF THE INVENTION

The systems disclosed in said documents may be suitable for controlling individual light sources among a large collection of light sources from one central location, which may be useful. However, problems arise when the light sources are supposed to cooperate in a harmonic and harmonious manner. Assume a street that is illuminated by a system of hundreds of light sources, each having the same scenario stored in its memory, defining a closed path in the color space being travelled continuously, thus for instance consecutively producing blue-green-yellow-orange-red-purple-blue. Each local controller will travel the defined color path using timing information based on its internal clock signal. These internal clocks are never perfectly mutually identical, thus, after some time, the light effects as produced are no longer in harmony any more. It may even be that one light source is producing red light while at the same another light source is producing green light, for instance, at a moment when they both are supposed to produce yellow. These problems will hardly be noticeable if the scripts or scenarios are only related to a relatively limited time interval, but may be unacceptable after prolonged time. US-2006/0.132.065 describes that each light source should have a real-time clock, but this adds to the costs.

An object of the present invention is to solve or at least reduce said problems.

According to the present invention, the central controller is designed, during the EXECUTE mode, to regularly transmit synchronization signals over the communications network, and the local controllers are designed, in response to receiving a synchronization signal, to adapt the timing of its control signals for the light source, if needed.

Further advantageous elaborations are mentioned in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which: figure 1 schematically illustrates an illumination system; figure 2 schematically shows a timing diagram.

DETAILED DESCRIPTION OF THE INVENTION

Figure 2 schematically shows a timing diagram for illustrating the operation of the system 1 according to the present invention. The diagram illustrates that in a first time

interval the system is in the TEACH/LEARN mode, during which there is data traffic 21 from central controller 2 to the local controllers 110 of the illumination units 100 for storing a color scenario into the respective memories 111.

After the first time interval, the system may be in a WAIT mode, during which the light sources 102 are inactive or stationary and the local controllers 110 are awaiting a start signal 22 from the central controller 2, which may be implemented by any suitable digital code.

The start signal 22 indicates the beginning of the EXECUTE MODE. On receipt of the start signal 22, the local controllers 110 of the illumination units 100 start executing the color scenario stored in their respective memories 111. Repeatedly, the central controller 2 transmits synchronization signals 23. These synchronization signals 23 may be simple pulses, transmitted at regular intervals, for instance once per second, although it is noted that the regularity of these intervals is not essential. Alternatively, the synchronization signals 23 may be more elaborate signals containing time information.

Each local controller 110 is provided with a local clock device 122, which operates on the basis of signals received from a local system clock 121 (see figure 1). The local controller 110 times the execution of the scenario on the basis of timing signals St from its local clock device 122. With time, a deviation may develop between the time represented by the local clock device 122 and the time represented by other local clock devices of other illumination units 100, caused by inaccuracies and tolerances of the different local system clocks, so that the different scenarios would run out of synchronization. This is prevented because each local controller 110, on receipt of the synchronization signals 23, sends a command signal Sc to its corresponding local clock device 122 for adapting the timing of this clock device 122.

Thus, during the EXECUTE mode, there is only very limited data traffic over the communications network, so that data collision and similar problems are not expected.

In a practical example, for a system comprising 100 illumination units, a color scenario is defined having a duration of 3600 seconds (1 hour). Assume that this scenario is centrally dictated in real time. Assume that the time duration of the scenario is subdivided into consecutive time frames of 100 ms (or other suitable duration), and by defining three bytes of color information (RGB or HSB) per time frame. These three bytes, during each time frame, define the color, which remains constant during the time frame. For real time

signal transmission, 3000 bytes per second would have to be transmitted over the communications network by the central controller.

In accordance with the present invention, the scenario duration of 3600 seconds may be subdivided in 1000 intervals of 36 time frames each. In each time interval, three color functions are defined, one for Hue, one for Saturation, and one for Brightness. Each color function, which approximates the time development of the corresponding color index (H, S, B) during the corresponding interval, is defined by 6 bytes, one byte defining amplitude and five bytes defining coefficients of a polynome. Thus, 18 bytes per interval have to be sent. For 1000 intervals and 100 illumination units, 1.800.000 bytes have to be sent. Assuming a transmission rate of 3000 bytes per second, as above, the transmission would require 600 seconds (10 minutes), i.e. the TEACH/LEARN mode would require 10 minutes (and perhaps somewhat longer for error correction).

Assume that the local system clocks suffer from an error of 0.5%: without synchronization, the different scenarios may have a delay of 18 seconds with respect to each other after one hour. It is noted that more accurate clocks are available, yet at substantially higher costs. Assume that a maximum delay of 100 ms (corresponding to one time frame) would be acceptable: this corresponds to a playing time of 20 seconds. Thus, during the EXECUTE mode, the central controller only needs to send one synchronization byte every 20 seconds, which amounts to negligible data traffic.

Summarizing, the present invention provides an illumination system 1 with distributed intelligence comprising: a plurality of illumination units 100, each unit comprising a variable color light source 102, a light source driver 101, a local controller 110 controlling the driver, a local clock device 122 and a scenario memory 111; a central controller 2, communicating to the local controllers over a communications network 3.

When operating in a TEACH/LEARN mode, the central controller transmits data 21 defining color scenarios, and the local controllers store these data into their associated scenario memories. When operating in the EXECUTE mode: each local controller operates autonomously to execute the color scenario stored in its associated scenario memory under timing control by the local clock device;

the central controller transmits synchronization signals 23; the individual local controllers, in response to receiving a synchronization signal, adapt the timing of their control signals for the corresponding light source drivers.

While the invention has been illustrated and described in detail in the drawings and foregoing description, it should be clear to a person skilled in the art that such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments; rather, several variations and modifications are possible within the protective scope of the invention as defined in the appending claims.

For instance, it is noted that EXECUTE mode and TEACH/LEARN mode will typically be separated in time, as far as relating to the same scenario. However, while executing one scenario, it is possible to receive (TEACH/LEARN mode) data relating to a next scenario. It is further possible that during the TEACH/LEARN mode data will be transmitted defining a plurality of scenarios, and that during the EXECUTE mode the central controller is capable to transmit different starting signals for starting different scenarios.

Although color definitions in HSB space are most suitable, the present invention is not restricted to the use of HSB space. Also, the present invention can be implemented equally well with scenarios defined as look-up table or as functions of time. Further, a local controller may be designed to control its light source on the basis of RGB data, which it can calculate from the HSB values on the basis of predefined formulas or on the basis of predefined look-up tables.

Although the present invention is most useful when the communications network 3 is a wireless network, the present invention can also be implemented and is already useful in the case of communication over fixed physical media such as wires, optical fibres, etc.

The EXECUTE mode can be started by the central controller 2 in response to a user command received over the User Interface UI or on the basis of a fixed time being reached. It is also possible that the EXECUTE mode is started by the central controller 2 in response to a trigger signal from a sensor, such as a motion detector, a pressure sensor, a presence detector, a proximity sensor, a temperature sensor, a light sensor, an RFID sensor, etc.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings,

the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

In the above, the present invention has been explained with reference to block diagrams, which illustrate functional blocks of the device according to the present invention. It is to be understood that one or more of these functional blocks may be implemented in hardware, where the function of such functional block is performed by individual hardware components, but it is also possible that one or more of these functional blocks are implemented in software, so that the function of such functional block is performed by one or more program lines of a computer program or a programmable device such as a microprocessor, microcontroller, digital signal processor, etc.