WO2010089596A2

WO2010089596A2 - Improvements in and relating to lighting systems for train units

Info

Publication number: WO2010089596A2
Application number: PCT/GB2010/050171
Authority: WO
Inventors: Adrian Rawlinson
Original assignee: Marl International Limited
Priority date: 2009-02-05
Filing date: 2010-02-04
Publication date: 2010-08-12
Also published as: WO2010089596A3; GB0901810D0

Abstract

A lighting system for a train unit, the lighting system comprising a light source, a light level detector and a controller, the controller being configured to change the output of the light source for a period to a predetermined level, to receive from the light level detector a measure of the ambient light level and to adjust the illumination provided by the light source dependent on the measure of the ambient light level towards a target power level.

Description

Improvements in and Relating to Lighting Systems for Train Units

Field of the Invention

The present invention relates to lighting systems for train units and to methods of controlling the same.

Background to the Invention

A train unit usually comprises a number of connected vehicles such as carriages and an engine. Regardless of its source of motive power, it is desirable for the lighting system in a train unit to use as little power as possible while still providing sufficient illumination.

Summary of the Invention

According to the present invention in a first aspect, there is provided a lighting system for a train unit, the lighting system comprising a light source, a light level detector and a controller, the controller being configured to change the output of the light source for a period to a predetermined level, to receive from the light level detector a measure of the ambient light level and to adjust the illumination provided by the light source dependent on the measure of the ambient light level towards a target power level.

Suitably, the change of the illumination to a predetermined level is for a period of not more than 25 milliseconds and, more suitably, not more than 10 milliseconds.

Suitably, before the change of output of the light source for a predetermined period, the brightness level of the light source is increased beyond the present current level by a predetermined amount for a period of not more than 50 milliseconds. Suitably, after the change of output of the light source for a predetermined period, the brightness level of the light source is increased beyond the previous current level by a predetermined amount for a period of not more than 50 milliseconds. Suitably, the increase occurs before and after the change of output of the light source for a predetermined period.

Suitably, before being used to adjust the illumination, it is determined whether an ambient light level detected is a valid reading and only valid readings are used. Suitably, a reading is valid if the reading is non-zero and is within a predetermined tolerance of the brightest level detected.

Suitably, the system additionally comprises a look-up table for determining a target power level of a light source for a given measured ambient light level. Suitably, the light source comprises a light emitting diode (LED). Suitably, the LED is a white light LED. Suitably, the LED is driven on a constant current basis.

Suitably, when the light source output is changed to a predetermined level this is a first state and when the light source is driven to provide the desired level of illumination this is a second state, there being a power level being provided to the light source in the second state, and while the system is in the second state it is configured whereby a light level is detected, which light level is corrected for the ambient light level and if the actual light level provided in the second state is different from the predetermined light level that should be provided at that power level, the power to the light source is adjusted accordingly.

Suitably, there is a plurality of light sources. Suitably, the plurality of light sources is driven to the same illumination level. Suitably, each of the plurality of light sources comprises a light level detector and a master controller is configured to determine an average of the detected light levels to determine a measure of the ambient light level. Alternatively, each of the plurality of light sources comprises a light level detector and the light level detectors are split into a plurality of zones, and a master controller is configured to determine an average of the detected ambient light levels in each zone and to select the lowest of the determined averages as the measured ambient light level.

Suitably, if the target power level is above the current power level, the power level adjustment is carried out at a first speed and if the target power level is below the current power level, the power level adjustment is carried out at a second speed, in which the first speed is greater than the second speed. Suitably, the first speed is at least 10 times greater than the second speed. Suitably, the first speed is at least 100 times the greater than the second speed. Suitably, the first speed is at least 1000 times greater than the second speed. Suitably, the first speed targets to adjust the power level to the target power level within up to 25OmS, preferably within up to 10OmS. Suitably, the second speed targets to adjust the power level to the target power level in more than 10 seconds, more suitably in more than 20 seconds and preferably in 30 seconds or more.

Suitably, the first speed and the second speed are adjusted in time based on the derivative value of the required power adjustment.

Suitably, the system comprises a plurality of light sources and a light source in the system is set to stay at a constant level. Suitably, the change of the light source output for a predetermined period is a reduction in the power level of the light source.

Suitably, the predetermined level is less than 10% of the maximum brightness level. Suitably, the predetermined level is less than 5% of the maximum brightness level. Suitably, the predetermined level is less than 1 % of the maximum brightness level. Suitably, the predetermined level is zero.

Suitably, the controller comprises an identifier to distinguish it from other controllers in the system.

Suitably, the controller comprises a zone identifier.

Suitably, the period for which the light source output is at a predetermined level is for a predetermined period.

According to the present invention in a second aspect, there is provided a method of controlling a lighting system for a train unit, the lighting system comprising a light source, a light level detector and a controller, in which the controller changes the output of the light source for a period to a predetermined level, receives from the light level detector a measure of the ambient light level and adjusts the illumination provided by the light source dependent on the measure of the ambient light level towards a target power level.

Brief Description of the Drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figure 1 is a schematic illustration of a train unit.

Figure 2 is a schematic illustration of a lighting system according to an embodiment of the present invention.

Figure 3 is a schematic illustration of a controller as shown in Figure 2.

Figure 4A is a schematic side elevation of a light source as shown schematically in Figure 2. Figure 4B is a schematic end elevation of the light source shown in Figure 4A.

Figure 5 is a functional flow diagram illustration a method of operation of the present invention.

Figure 6 is a graph showing illumination level over time.

Figure 7is a graph showing the representation between ambient light level and LED driver voltage.

Description of the Preferred Embodiments

Referring to Figure 1 of the accompanying drawings, there is shown a train unit 2 comprising three vehicles 4A, 4B and 4C. By way of example, vehicle 4A could be a combined driver/carriage while vehicles 4B and 4C carriages.

The train unit is divided into a plurality of zones. In this case three zones first 6A, second 6B and third 6C are used. The precise sizing of each zone 6A, 6B and 6C is not critical, but typically a zone (here 6A and 6C) at either end of the train unit 2 will be one-third of the length of the respective vehicle 4A and 4C, respectively.

Referring to Figure 2 of the accompanying drawings, there is shown a lighting system 8 according to the present invention.

In overview, the lighting system 8 seeks to adaptively control the lighting level in the vehicles 4A, 4B and 4C based on their ambient light levels so as to avoid unnecessary power usage. When the train unit 2 is in good ambient light, the lighting level is reduced within the vehicles 4A, 4B and 4C. In darker conditions, the lighting level is increased.

The lighting system 8 comprises a plurality of light emitting diode (LED) white light sources 1OA, 1OB, 1 OC, 10D, 10E, 10F, etc. Each light source 10 is controlled by a local controller 12A, 12 B, etc. Each controller 12 is capable of controlling a plurality of light sources 10. Typically, each controller 12 will control up to four light sources 10. Each controller 12 is connected to a common communication bus 14 and to a power supply line 16. Each controller also has attached to it a light level detector 18 the output of which is determined by the ambient light level. In practice, each light fitting will include a plurality of light sources 10 and one controller 12 will control the light sources 10 for a given light fitting. In use, the light level detector 18 is placed in a suitable position within the vehicle.

A master controller 19 receives information from each controller 12 to control the system. Referring to Figure 3 of the drawings that follow, each controller 12 comprises a power supply unit 20, a communications module 22, a microcontroller 24, an identification code setting unit 26, a zone coding unit 28 and an LED driver 30. Additionally there is a light sensor input 32, a communications line 34, a power input 36 and a light source output 38.

Power supply unit 20 converts the normal (nominal) 110V supply from power input 36 into the voltage needed by the driver electronics.

Communications module 22 handles communications via the communication bus 14 to enable controllers within the same carriage (and optionally between carriages) to transmit light level measurements to the master controller in order that the master controller can determine the correct average light level for the appropriate section of the train and hence the desired light output from the system.

Microcontroller 24 receives the light level signal from the light sensor output 32 to communicate this to the master controller via the communication bus 14 and controls the LED driver 30 to control the light source illumination level.

Identification code setting unit 26 provides a pin based input to enable each local controller 24 on the train unit to have a unique address, ID_CODE, from 128 available addresses (0-127).

Zone coding unit 28 is a binary coded pin based input enabling the microcontroller 24 to be set with a ZoneJD as one of Zone_1 , Zone_2, Zone_3, Zone_Cab or Zone_ toilet.

With reference to Figures 4A and 4B of the accompanying drawings, there is shown a light source 10. The power supply 20 provides regulated power for the local controller 12.

The light source 10 comprises a lighting unit assembly support frame 43 with fixings points 42 for fixing to an inner skin 45 of a train carriage, and housed within the outer skin 44 of the carriage.

Additionally the light source 10 comprises a LED lighting panel 48 consisting of an array of white light emitting LEDs mounted behind a suitable light diffuser.

Referring to Figure 5 of the accompanying drawings a method of operation of the lighting system described above will now be set out. The master controller 19 controls the actions of the system 8 sending instructions to each of the local controllers 12.

In a configuration step, as each controller 12 is set up in the respective vehicle, the ambient light level detector 18 is positioned somewhere suitable in the unit, to represent the ambient light in that part of the unit as likely to be experienced by users. Light sources 10 are located in each unit. Each controller 12 is allotted a unique ID_CODE using identification code setting unit 26. Each controller 12 has its respective zone location input as a ZoneJD using zone coding unit 28. Each controller is connected to the power supply line 16 and the communications bus 14.

In step 100, the system is turned on and, after booting up the, light source output is set to maximum.

In step 102, the light sources 10 are turned off for 5 milliseconds (mS) during which "off' time an ambient light level reading is taken using the light level detector 18 for each controller 12. This ambient light level information is sent by each local controller 12 to the master controller 19 together with the ID_CODE of the controller 12 and its Zone Code. The light illumination level is then returned to the previous setting from just before the light sources were turned off. The short time for which the light sources 10 are turned off make this "off' time mostly imperceptible to the human eye.

In practice, it has been found by the present inventors that occasionally even this very short "off" time can be noticed by some observers. However, it has been found that if the illumination level is raised before being turned to zero then even this low level of perceptibility is done away with. The effect appears to be present if the illumination level is raised to above the desired level after the "off" period or both before and after the "off" period. This is illustrated with reference to Figure 6 of the accompanying drawings. In Figure 6, the Y-axis represents the illumination level while the X-axis represents time. At point A the illumination level is increased from the desired level it was at previously for a short period such as 5 milliseconds and then the current is turned off to reduce the illumination level to zero from point B to point C and after point C the illumination level is increased to above the desired level preceding the "off" period, again for a short period such as 5 milliseconds before being returned at D to the previous desired level from which it will, if appropriate change to (or at least towards) the new desired level.

In step 104, the master controller 19 first determines, for each local controller 12, whether it is determined to be a valid signal. For a signal to be valid it must be greater than zero and within a predetermined tolerance of the brightest level detected for example when the LEDs are first illuminated at step 100 or subsequently at step 110. The brightest level must be at least four times the ambient level for the latter to be regarded as valid. Any invalid signals are ignored.

In step 106, for each of Zone_1 , Zone_2 and Zone_3 the mean average of the ambient light level is determined. The minimum of these averages is then determined and used to set the target LED current (i.e. power level) as shown in Figure 7 of the accompanying drawings.

In step 108, the actual LED current is adjusted towards the target LED current (i.e. power level). The adjustment is not immediate, but instead is ramped. The ramping is carried out differently depending on the direction of the change. If the light level needs to be increased, the ramping up is carried out relatively swiftly, within 10OmS. If the light level needs to be decreased, the ramping down is carried out significantly more slowly, over approximately 30 seconds. Within these target times for light level variance, the rate of ramp is proportional to the difference between the target LED current and the actual LED current (i.e. derivative control). This ensures a fast response, for example when entering a tunnel, but a slower change during small ambient light level changes, for example when passing through the shadow of trees.

The power output to the LEDs is on a constant current basis and not, for instance, on a pulse width modulation basis.

Thus after an imperceptibly short "off' period, to avoid the appearance of the lighting flickering, the lights are turned on again initially at their previous brightness, but (assuming some change is required) moving towards the desired current level. The target current is the same for all light sources in each of the zones Zone_1 , Zone_2 and Zone_3.

In step 110, while the light sources are "on", a reading is taken from each light level detector. For each detector (i.e. each local controller) the light level measured in the last "off" period (see step 108 above) is subtracted from the signal measured during the "on" period. This value is cross referenced with the actual LED current and compared with a notional "correct" illumination level in a look-up table. The look-up table is predetermined based on empirical evidence of actual lighting levels for a fully functioning light source. If the light level is incorrect in comparison with the look-up table then a corrective additional or reduced current is applied as appropriate. This correction is maintained for future use. That is, if during an "off' period an ambient light level of x is measured which according to Figure 6 should give a target LED current of I then the target LED current is varied to I + δ, where δ is 5% of I and can be positive or negative. Thus, if there is degradation in performance of the respective light source 10, this can be compensated for by increasing the current from a notional level to an increased level to accommodate this.

In step 112 there is an in built delay of 25mS during which the light sources 10 remain on before the next ambient light level determination.

The method then returns to step 102 and keeps repeating the processes until switched off.

It is noted that the cab and toilets (as indicated by the Zone_ID) are kept at 100% illumination at all times. Also, in the event of a loss of communication data or a fault state, the system defaults to full intensity lighting.

Some of the lighting units can be designated as emergency lighting units. These contain their own battery pack (not shown) so that in the event of a power outage (or other specified conditions) they provide emergency illumination giving >15 Lux 750mm above floor level for 180 minutes (5 Lux after 90 minutes to save on power). The batteries charge from the power line 16 within 100 minutes.

As an additional feature the system may use the master controller for data logging, capturing data such as: total hours run (HH:MM:SS), time at different lighting levels, monitoring the corrections applied to the LED current (as in step 110). This data, together with the running hours can be used statistically to predict the life of the lighting unit during routine maintenance checks and allow the early replacement of potential failures as a preventative measure.. The data logging feature includes an interface for transferring the data to, for instance, a personal computer or portable digital assistant. The data transfer may be by cable or wirelessly.

It will be appreciated, therefore, that the illumination provided by the light sources is continually varied adaptively depending on the detected ambient light level.

Although a 5mS "off" time is referred to above, this can be varied. Currently it is believed that an "off' time in the range 1-1OmS would be suitable. Similarly other timings can be varied within the scope of the present invention.

Although the system is described with a separate master controller, it will be appreciated that this may be incorporated into one of the local controllers. In an alternative embodiment, a unit with a controller may have a plurality of connected slave units it controls. In that case, the slave units do not have controllers and need not have light sensors.

In some variants of the system described above, not all of the light sources will have an ambient light level detector, for instance because two light sources are in very close proximity or because a sensor has malfunctioned.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A lighting system for a train unit, the lighting system comprising a light source, a light level detector and a controller, the controller being configured to change the output of the light source for a period to a predetermined level, to receive from the light level detector a measure of the ambient light level and to adjust the illumination provided by the light source dependent on the measure of the ambient light level towards a target power level.

2. The lighting system of claim 1 , in which the change of the illumination to a predetermined level is for a period of not more than 25 milliseconds.

3. The lighting system of claim 2, in which the change of the illumination to a predetermined level is for a period of not more than 10 milliseconds.

4. The lighting system of any preceding claim, wherein before the change of output of the light source for a predetermined period, the brightness level of the light source is increased beyond the present current level by a predetermined amount for a period of not more than 50 milliseconds.

5. The lighting system of claim 4, wherein after the change of output of the light source for a predetermined period, the brightness level of the light source is increased beyond the previous current level by a predetermined amount for a period of not more than 50 milliseconds.

6. The lighting system of claim 4 or claim 5, wherein the increase occurs before and after the change of output of the light source for a predetermined period.

7. The lighting system of any preceding claim, wherein before being used to adjust the illumination, it is determined whether an ambient light level detected is a valid reading and only valid readings are used.

8. The lighting system of claim 7, wherein a reading is valid if the reading is non-zero and is within a predetermined tolerance of the brightest level detected.

9. The lighting system of any preceding claim, wherein the system additionally comprises a look-up table for determining a target power level of a light source for a given measured ambient light level.

10. The lighting system of any preceding claim, wherein the light source comprises a light emitting diode (LED).

11. The lighting system of any preceding claim, wherein the LED is a white light LED.

12. The lighting system of claim 10 or claim 11 , wherein the LED is driven on a constant current basis.

13. The lighting system of any preceding claim, wherein when the light source output is changed to a predetermined level this is a first state and when the light source is driven to provide the desired level of illumination this is a second state, there being a power level being provided to the light source in the second state, and while the system is in the second state it is configured whereby a light level is detected, which light level is corrected for the ambient light level and if the actual light level provided in the second state is different from the predetermined light level that should be provided at that power level, the power to the light source is adjusted accordingly.

14. The lighting system of any preceding claim, wherein there is a plurality of light sources.

15. The lighting system of claim 14, wherein the plurality of light sources is driven to the same illumination level.

16. The lighting system of claim 14 or claim 15, wherein each of the plurality of light sources comprises a light level detector and a master controller is configured to determine an average of the detected light levels to determine a measure of the ambient light level.

17. The lighting system of claim 17, wherein each of the plurality of light sources comprises a light level detector and the light level detectors are split into a plurality of zones, and a master controller is configured to determine an average of the detected ambient light levels in each zone and to select the lowest of the determined averages as the measured ambient light level.

18. The lighting system of any preceding claim, wherein if the target power level is above the current power level, the power level adjustment is carried out at a first speed and if the target power level is below the current power level, the power level adjustment is carried out at a second speed, in which the first speed is greater than the second speed.

19. The lighting system of claim 18, wherein the first speed is at least 10 times greater than the second speed.

20. The lighting system of claim 18, wherein the first speed is at least 100 times the greater than the second speed.

21. The lighting system of claim 18, wherein the first speed is at least 1000 times greater than the second speed.

22. The lighting system of claim 18, wherein the first speed targets to adjust the power level to the target power level within up to 25OmS.

23. The lighting system of claim 18, wherein the first speed targets to adjust the power level to the target power level within up to 10OmS.

24. The lighting system of claim 18, wherein the second speed targets to adjust the power level to the target power level in more than 10 seconds.

25. The lighting system of claim 18, wherein the second speed targets to adjust the power level to the target power level in more than 20 seconds.

26. The lighting system of claim 18, wherein the second speed targets to adjust the power level to the target power level in 30 seconds or more.

27. The lighting system of claim 18, wherein the first speed and the second speed are adjusted in time based on the derivative value of the required power adjustment.

28. The lighting system of claim 1 , wherein the system comprises a plurality of light sources and a light source in the system is set to stay at a constant level.

29. The lighting system of any preceding claim, wherein the change of the light source output for a predetermined period is a reduction in the power level of the light source.

30. The lighting system of any preceding claim, wherein the predetermined level is less than 10% of the maximum brightness level.

31. The lighting system of claim 30, wherein the predetermined level is less than 5% of the maximum brightness level.

32. The lighting system of claim 30, wherein the predetermined level is less than 1 % of the maximum brightness level.

33. The lighting system of claim 31 , wherein the predetermined level is zero.

34. The lighting system of any preceding claim, wherein the controller comprises an identifier to distinguish it from other controllers in the system.

35. The lighting system of any preceding claim, wherein the controller comprises a zone identifier.

36. The lighting system of any preceding claim, wherein the period for which the light source output is at a predetermined level is for a predetermined period.

37. A method of controlling a lighting system for a train unit, the lighting system comprising a light source, a light level detector and a controller, in which the controller changes the output of the light source for a period to a predetermined level, receives from the light level detector a measure of the ambient light level and adjusts the illumination provided by the light source dependent on the measure of the ambient light level towards a target power level.

38. A lighting system for a train unit substantially as described herein with reference to the accompanying drawings.

39. A method of controlling a lighting system for a train, the method being substantially as described herein with reference to the accompanying drawings.