WO2014108771A2

WO2014108771A2 - Controlling a lighting system based on detecting motion

Info

Publication number: WO2014108771A2
Application number: PCT/IB2013/060762
Authority: WO
Inventors: Jurgen Mario Vangeel; Wijnand Johannes Rietman; Roger Peter Anna Delnoij
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-01-08
Filing date: 2013-12-10
Publication date: 2014-07-17
Also published as: WO2014108771A3

Abstract

Method and system (100) for automatically controlling at least one lighting system (11),based on sensing an amount of light in an area (12) and based on detecting motion in a field of view that overlaps said area (12), said system having at least one light sensor (16) arranged for sensing an amount of light in an area(12); at least one motion sensor (18) arranged for detecting motion in a field of view; and a control unit (20) adapted to control at least one lighting system (11) in response to an amount of light sensed by the at least one light sensor (16), the control unit (20) being adapted to control the at least one lighting system (11),taking into account feedback from light of the at least one lighting system (11) illuminating said area (12) and being sensed by the at least one light sensor (16), wherein the control unit (20) is adapted to at least temporarily at least partially inhibit a control response to a variation of an amount of light, when a detected motion and said variation of an amount of light occur within a predetermined time interval (T1).

Description

Controlling a lighting system based on detecting motion

FIELD OF THE INVENTION

The invention relates to a system for automatically controlling at least one lighting system, based on sensing an amount of light in an area. Such a system may find application in a daylight harvesting system for controlling at least one artificial light source, based on sensing an amount of light in an area.

BACKGROUND OF THE INVENTION

Daylight harvesting systems switch off or dim artificial light if sufficient daylight is available. By virtue thereof, significant amounts of energy may be saved. Such systems typically comprise at least one light sensor arranged for sensing an ambient light level, i.e. the amount of ambient light present, which may include both natural and artificial light.

US 5,834,765 describes an integral ambient light and occupancy sensor that is based on a single light sensing device and capable of concurrent ambient light and object motion detection.

US 5,406, 173 A describes an apparatus and a method for adjusting light according to a level of ambient light entering a room. For example, a comparator compares a detected light level to N predetermined light levels of increasing intensity, and a lighting unit is set to one of N+l different intensity levels, dependent on the comparisons. A controlling circuitry increases the light level in a room when the room is occupied and the light meter senses that the ambient light level is not above a particular level. In order to avoid annoyance, the device decreases the light level of the room only when the room is unoccupied for a brief period of time. In this case, the device increases or decreases the light level of the room by controlling lights accordingly in response to the level of light sensed by the light meter.

When the room is unoccupied for an extended period of time, the device turns the power off to all the lights in the room. In this manner, when the room has been unoccupied for a substantial time period, energy costs can be saved.

Other known daylight harvesting systems have a light sensor for indirect light measurement, which measures the light reflected from the surroundings. For example, a system controls an artificial light such that, ideally, a constant light level is maintained. For example, a light sensor for indirect light measurement may be mounted above a sensing area, e.g. at a ceiling of a room.

SUMMARY OF THE INVENTION

Known daylight harvesting systems are easily influenced by external influences other than the daylight level. The inventors have found that one of the most important external influences is a change in the reflection coefficient of the surroundings in the sensing area of the light sensor, which change may be linked to persons in the proximity of the light sensor. For example, the variation of the sensed amount of light may be caused by the shadow of a person passing through the sensor's detection area. Moreover, the amount of light that falls on and is reflected by people's clothing may have a significant influence on the detected amount of light when people change their position or posture in the sensing area of the light sensor. It is perceived as unacceptable if lights are switched off or dimmed only due to an action performed by a person in the room.

It is an object of the invention to provide a novel system for controlling at least one lighting system or light source, based on sensing an amount of light in an area, which novel system allows to automatically control, with improved accuracy, at least one lighting system or light source in response to a variation of a sensed amount of light.

This object is achieved by means of a system for automatically controlling at least one lighting system, based on sensing an amount of light in an area and based on detecting motion in a field of view that overlaps said area, comprising:

at least one light sensor arranged for sensing an amount of light in said area; at least one motion sensor arranged for detecting motion in said field of view; a control unit, adapted to control at least one lighting system in response to an amount of light sensed by the at least one light sensor, taking into account feedback from light of the at least one lighting system illuminating said area and being sensed by the at least one light sensor,

wherein the control unit is adapted to at least temporarily at least partially inhibit a control response to a variation of an amount of light, when a detected motion and said variation of an amount of light occur within a predetermined time interval.

For example, the system may be a daylight harvesting system. For example, the lighting system is an indoor lighting system. For example, the control unit estimates the relevance of the detected motion for the sensed light level variation. When a detected motion and a variation of an amount of light occur within a predetermined time interval, i.e. there is sufficient temporal correlation between the detected motion and the variation of an amount of light, it can be assumed that the variation of an amount of light is caused by the motion of one or more persons in the field of view of the motion sensor. In this case, the control response to the variation of an amount of light, which would be the control response of the control unit in case no motion was detected, is at least temporarily at least partially inhibited. In other words, the variation of an amount of light is at least partly disregarded for the purpose of controlling the at least one lighting system for a certain period of time or permanently. That is, a control response is provided, or controlling is performed, as if the variation of an amount of light was smaller than it actually is, or as if there was no variation of an amount of light. Thus, unwanted changes of artificial light caused by motion of people may be eliminated or at least reduced.

Inhibiting a control response at least temporarily may comprise inhibiting the control response for an indefinite time or only during a limited time interval. For example, the control unit may be further adapted to finish inhibiting said control response when a second time interval has been completed during which said control response has been at least partially inhibited.

Inhibiting a control response at least partially may comprise fully inhibiting the control response or partially inhibiting the control response.

For example, said at least temporarily at least partially inhibiting a control response to a variation of an amount of light may comprise correcting the measured light level based on said variation of the amount of light. For example, a correction value may be at least temporarily added to the sensed light level. That is, said at least temporarily at least partially inhibiting of a control response to a variation of an amount of light may comprise at least temporarily adding a correction value to the control input, wherein said correction value at least partially compensates said variation of the light level. In an analogous manner, for example, said at least temporarily at least partially inhibiting a control response to a variation of an amount of light may comprise at least temporarily adapting at least one control set point, e.g. a lower set point and/or a higher set point of a set point range.

For example, said at least partially inhibiting a control response to a variation of an amount of light comprises at least partially inhibiting the control response for at least a second time interval, wherein said second time interval is longer than said predetermined time interval, which predetermined time interval will also be referred to as a first time interval in the following.

Nevertheless, the system may be able to react to a variation of a daylight level which normally does not temporarily correlate with motion within the field of view of the motion sensor. Preferably, during said certain time period, while the control response to said variation of an amount of light is at least partially inhibited, a further variation of an amount of light may still lead to a control response when no motion is detected within the

predetermined time interval from the further variation of an amount of light.

Preferably, said at least one lighting system comprises at least one light source, in particular at least one artificial light source, e.g. one or more ceiling-mounted light sources. For example, the at least one lighting system may be at least one light source.

The at least one light sensor is arranged for sensing an amount of light in an area, which will also be referred to as the sensing area. Preferably, the at least one light sensor is arranged for sensing an amount of light by indirect light sensing. In other words, the light sensor is adapted for sensing an amount of light reflected by said area. In particular, for example, a light sensor may be adapted to sense an amount of diffusely scattered light, e.g. diffusely scattered light from at least one surface in said area. Since diffusely scattered light constitutes the major part of the light normally perceived by human eyes inside a building, the amount of diffusely scattered light e.g. at the desk of an office worker, will be a deciding factor in whether the light is perceived as being convenient, too dark, or, in some situations, too intense. For example, tasks such as reading, writing or typing may require a certain light level on the work surface in order to be performed efficiently without fatigue. For example, the light sensor of the system may be adapted to be mounted at a ceiling of a room, facing downward for sensing an amount of light from a sensing area below the light sensor. For example, at least one light sensor may be integrated in a luminaire adapted to be controlled by the control unit.

For example, the at least one light sensor is arranged, relative to the lighting system or relative to at least one light source of the lighting system, so as to let light from the lighting system illuminate said area. For example, a light sensor is integrated in a luminaire.

The control unit is adapted to control the at least one lighting system in response to an amount of light sensed by the at least one light sensor, taking into account feedback from light of the at least one lighting system illuminating said area and being sensed by the at least one light sensor. For example, said at least one light sensor may be arranged to sense light from at least one light source of said at least one lighting system. For example, a light sensor may be arranged to sense an amount of ambient light from a sensing area, wherein said ambient light from the sensing area comprises reflected light from the at least one lighting system, more preferably, diffusely scattered light from said at least one lighting system, and, more preferably, from at least one light source of the at least one lighting system. Thus, if daylight is available from a daylight source, such as a window or a skylight, the ambient light sensed by the light sensor may comprise daylight and artificial light from the at least one light source. For example, the control unit is adapted to control the at least one lighting system, based on an amount of light sensed by the at least one light sensor, said amount of light including light of the at least one lighting system, which light illuminates said area.

Preferably, said controlling is a negative feedback controlling. For example, the control unit is adapted to control the at least one lighting system such that more light is provided when a reduction of an amount of light is detected, and/or such that less light is provided when an increase of an amount of light is detected. That is, the direction of control is opposite to the detected variation of the amount of light. For example, the control unit may be adapted to control the at least one lighting system in order to limit or minimize a deviation of the sensed amount of light from a target range. For example, the target range may comprise a lower set point and an upper set point determining the range, or the target range may be an open range determined by a lower set point. For example, the control unit may be adapted to control the at least one lighting system in order to maintain at least a minimum amount of light corresponding to the lower set point, and the control unit may be adapted to increase light output of the at least one lighting system when the sensed amount of light is above the lower set point. The control unit may further be adapted to reduce light output when the sensed amount of light is above the upper set point.

For example, the at least one light sensor may comprise at least one of a photo diode, a photo resistor, a photo transistor, etc. In particular, the at least one light sensor may be adapted to provide an output signal that is indicative of an amount of light reaching the light sensor from a field of view of the light sensor within a frequency range and/or dependent on a frequency-dependent light sensitivity of the light sensor. Below, an amount of light will also be referred to as a light level.

The at least one motion sensor is arranged for detecting motion in a field of view. For example, a motion sensor may comprise a presence sensor for sensing the presence of an object, such as a person, in a field of view. For example, motion may be detected based on a variation of presence information. For example, the at least one motion sensor may comprise at least one of an ultrasonic sensor, an optical sensor, e.g. an infrared sensor, a microwave sensor, etc. For example, the extent of inhibiting said control response is based on at least one of positional information about the detected motion, and a magnitude of the detected motion. For example, an output signal of the motion sensor may comprise positional information. For example, positional information may be obtained from output signals of two or more motion sensors.

For example, the at least one light sensor and the at least one motion sensor are mounted such that the field of view of the at least one motion sensor overlaps the sensing area of the at least one light sensor or, for example, substantially comprises the sensing area. For example, a light sensor and a motion sensor may be integrated into a luminaire. For example, a light sensor and a motion sensor may be mounted at a ceiling of a room, facing downward.

For example, a motion sensor may be adapted to provide information about a magnitude of a motion and/or information about a localization of a motion. For example, a size or magnitude of a detected motion within the field of view of a motion sensor may be classified according to the size of the motion. For example, when a person is walking within the field of view or sensing area, the detected motion will be classified as a large motion. For example, typical movements of a person sitting in a chair doing deskwork will be classified as a minor motion. Further, for example, when a person is working, very concentrated, e.g. reading or only moving a computer mouse, the resulting typical motions will be classified as a tiny motion.

Partially inhibiting said control response may comprise limiting, e.g. reducing, said control response. For example, the extent to which said control response is inhibited may depend on at least one of information about the magnitude of the detected motion and information about the localization of the detected motion. For example, a light variation that coincides with a large motion detected close to the center of the field of view of the motion sensor may be fully disregarded for the purpose of said controlling, i.e. the corresponding control response may be inhibited, whereas a light variation that coincides with a medium size motion detected at some distance from the center of the field of view of the motion sensor may be partly disregarded for the purpose of said controlling, i.e. the corresponding control response may be partially inhibited.

The object is also achieved by means of a method of automatically controlling at least one lighting system, based on sensing an amount of light in an area and taking into account feedback from light of the at least one lighting system illuminating said area, and based on detecting motion in a field of view that overlaps said area, wherein the method comprises:

sensing a variation of an amount of light in the area, using at least one light sensor;

- evaluating an output of a motion sensor arranged for detecting motion in said field of a view;

and, based on a result of the evaluating step, determining whether a detected motion and said variation of an amount of light occur at a predetermined time interval, and, in this case, at least temporarily at least partially inhibiting a control response to the variation of an amount of light.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 schematically illustrates a system according to an embodiment of the present invention;

Fig. 2 schematically illustrates an example of a motion sensor;

Fig. 3 illustrates a field of view of a motion sensor;

Fig. 4 illustrates the function of the system in a situation with daylight variation;

Fig. 5 schematically illustrates a motion signal and a detected amount of light in the situation of Fig. 4;

Fig. 6 illustrates the function of the system in a situation with movement of a user, causing a variation of a sensed amount of light;

Fig. 7 illustrates a motion signal and a detected amount of light in the situation of Fig. 6;

Fig. 8 illustrates the function of the system in a situation in which a user purposefully changes the amount of available daylight;

Fig. 9 illustrates a motion signal and a detected amount of light in the situation of Fig. 8; and

Fig. 10 schematically illustrates an operation chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 schematically illustrates a system 100 for automatically controlling light sources 10, based on light level sensing, as well as a room, in which the system is installed. The light sources 10 are part of a lighting system 11. For example, the room comprises an area 12 comprising a work space, which is illustrated in Fig. 1 in the form of a desk. Daylight is available at the area 12 e.g. through a window 14.

The system 100 comprises a light sensor 16. The system 100 is a daylight harvesting system adapted to maintain a minimum light level in the area 12 by controlling the light sources 10 in response to a variation of a light level sensed by the light sensor 16. The light sensor 16 is mounted at the ceiling above the area 12 and has a field of view that corresponds to the area 12, i.e. the area 12 is a sensing area of the light sensor 16. The light sensor 16 provides a light level signal that is indicative of the total amount of ambient light sensed by the light sensor 16. The light sources 10 are mounted at the ceiling, facing downwards for illuminating the area 12. In particular, the light sensor 16 and the light sources 10 are arranged such that the light sensor 16 senses light from the light sources 10 only when it is reflected at a surface in the area 12. In other words, direct light of the light sources 10 does not reach the light sensor 16. Furthermore, the light sensor 16 is arranged such that the light sensor 16 may sense reflected daylight, in particular daylight diffusely reflected at a surface in the area 12. Thus, the light level signal of the light sensor 16 is indicative of an amount of light available at the working space within the field of view of the light sensor 16, including artificial light from the light sources 10 and, if available, natural daylight.

The system 100 further includes a motion sensor 18 that is arranged above the area 12 and is mounted at the ceiling, facing downwards. A field of view of the motion sensor 18 substantially comprises the area 12. The motion sensor 18 provides an output signal which is indicative of motion detected within the field of view. Details of the motion sensor 18 will be discussed further below with reference to Fig. 2 and Fig. 3. In particular, the motion sensor 18 is adapted to detect motion of a person in the area 12, in particular in the surroundings of the workspace, which potentially may influence the amount of light reflected to the light sensor 16, including light reflected from said person.

The system 100 further comprises a control unit 20 adapted to receive output signals from the light sensor 16 and the motion sensor 18, and further adapted to control the light sources 10, based on the output signals of the light sensor 16 and the motion sensor 18. For example, the control unit 20 provides a control response and accordingly outputs a control signal to a light source driver 22 connected to the light sources 10 in order to drive the light sources 10 in accordance with the control signal. The light source driver 22 may be adapted to control one or more light sources 10, and the control unit 20 may be adapted to control one or more light source drivers. In the example shown, the light source driver 22 outputs drive signals for the individual light sources 10, based on corresponding control signals of the control unit 20. The light sources 10, the light sensor 16, the motion sensor 18, and the light source driver 22 are integrated in a luminaire 23 of the lighting system 11.

The control unit 20 comprises a memory 24 for logging light level information, based on light level signals received from the light sensor 16. For example, the light level information may comprise light level values associated with respective points in time.

Further, the control unit 20 comprises a memory 26 for logging motion information based on motion signals from the motion sensor 18. For example, the motion information may comprise values indicating a magnitude of motion and, optionally, values indicating a localization of motion, associated with respective points in time.

Further, the control unit 20 comprises a processing unit 28 adapted to calculate a temporal correlation between a variation of the light level sensed by the light sensor 16 and a motion detected by the motion sensor 18, as will be described in detail further below.

Fig. 2 schematically shows the motion sensor in a situation in which an object 30 is present within a field of view of the motion sensor 18. For example, the object 30 is a user of the workspace.

The motion sensor 18 is an ultrasound sensor comprising an ultrasound transmitter 32 and an array of ultrasound receivers 34 in the form of microphones.

Ultrasound signals are transmitted by the transmitter 32, reflected by the object 30, and received by the receivers 34. For example, the ultrasound transmitter 32 transmits ultrasound bursts in intermittent time intervals. The motion sensor 18 analyses the received echoes and generates an output signal, based on the received ultrasound signals. The motion sensor 18 determines an angular direction from where the ultrasound echoes are received, based on phase differences between the receivers 34. Moreover, a distance to the object 30 is determined from the time interval between sending the ultrasound signal and receiving the echo. A motion of the object 30 may be detected based on a variation of distance and/or angular direction between different measurements, for example. Thus, motion of the object 30 may be detected, and a motion signal may be generated. The motion signal may comprise information about the magnitude or size of the detected motion, based on a signal level of the received echoes corresponding to the size of the object 30 and based on a detected velocity of the motion. Further, the motion signal may comprise positional information about the detected motion, in particular distance information and information about the angular direction.

Fig. 3 schematically illustrates angles and ranges within a two-dimensional plane intersecting a field of view below the motion sensor 18. For example, the array of ultrasound receivers 34 is a one-dimensional array. Then, the motion sensor 18 may be adapted to determine the origin of the detected motion in a two-dimensional plane intersecting the field of view of the motion sensor 18. For example, the positional information corresponding to a detected motion may comprise an angular position representing an angular range. For example, the angular position may take values of 0° (directly beneath the sensor 18), +30°, -30° (relative to the vertical), +60°, or -60° (relative to the vertical). For example, the distance information corresponding to a detected motion may represent a distance range. For example, distance information may be classified as "close", "medium" and "far". In Fig. 3, corresponding distance ranges are indicated as "I", "Π", and "III".

When the motion sensor 18 comprises a two-dimensional array of ultrasound receivers 34, positional information about a detected motion may comprise two-dimensional directional information. Thus, the origin of a detected motion may be determined in a three dimensional space.

Returning to Fig. 1, the control unit 20 is adapted to control the light sources 10 in response to a variation of a light level sensed by the light sensor 16. In the following, this will illustrated with reference to Figs. 4 to 9.

Fig. 4 illustrates a situation where the amount of available daylight at the workspace 12 varies due to a variation of the incident solar radiation. For example, a variation of the incident solar radiation may be caused by weather activity, e.g. a changing cloud density.

The upper part of Fig. 5 schematically illustrates a magnitude of motion over time. During the illustrated time span, substantially no motion is detected. The magnitude of motion does not exceed a threshold value M.

For example, the light level measured by the light sensor 16 may vary as illustrated in the bottom part of Fig. 5 over a certain time span. A dashed line indicates the fraction of sensed light that is attributed to the incoming daylight. At a time A, there is a significant variation of the daylight level that exceeds a threshold L, and the total light level decreases, at first. At a time B, there is again a significant variation of the daylight level and, at first, of the total light level.

Over the illustrated time span, substantially no motion is detected. The motion signal, e.g. the magnitude of motion, is substantially zero. In particular, at the time points A, B of the detected light level variations, no concurrent motion is detected. Therefore, it can be assumed that the detected variation of light levels at the time points A, B is not due to movement of people in the area 12.

Therefore, the control unit 20, on detecting the variations of the light level, controls the light sources 10 in order to counteract the detected light level variations. For example, when the decrease of the light level is detected at time point A, the control unit 20 controls the light sources 10 in order to adjust the light and to counteract the decrease of the light level if the total light level would otherwise fall below a minimum light level to be maintained.

Correspondingly, when the daylight level increases at time B, the control unit 20 controls the light sources 10 such that less light is provided, if the minimum light level to be maintained can still be upheld. For example, if there is sufficient daylight after the daylight increase at time B, the control unit 20 may dim or switch off one or more of the light sources 10.

Thus, in a situation without detection of motion, the function of the system is similar to that of a known daylight harvesting system, in that the light sources 10 are controlled in response to a variation of a sensed amount of light.

As shown in Fig. 5, the amount of artificial light provided by the light sources 10 increases to counteract the decrease of the daylight level at time A, and the amount of artificial light decreases to counteract the increase of the daylight level at time B.

With reference to Fig. 6 and Fig. 7, the function of the system 100 will be explained in a situation where a motion of a person correlates with a variation of the sensed amount of light. As illustrated in Fig. 6, a person moves in the area 12, i.e. in the field of view of the light sensor 16, and in the field of view of the motion sensor 18. The amount of light reflected into the light sensor 16 varies due to the motion of the person.

The upper part of Fig. 7 illustrates a motion signal, in particular a magnitude of detected motion, over time. The lower part of Fig. 7 illustrates the sensed amount of light of the light sensor 16 over time. At a time A, a motion is detected which correlates with a decrease of the light level. Because of this correlation, it may be assumed that the variation of the light level is caused by a movement of a person and not by variation of the available daylight. In this example, the variation of the light level is above the predetermined threshold L of e.g. 5%, and a motion is detected, since the magnitude of motion is above the predetermined threshold M. Furthermore, the variation of the light level and the detected motion substantially coincide, i.e. they occur within a predetermined first time interval Tl . The length of the first time interval Tl should be chosen to be long enough to allow a correlation to be detected, and short enough to reduce unwanted latencies in light level adaption. Preferably, the time interval is less than 1 minute. For example, the time interval may be chosen to be 10 seconds or less. Thus, e.g. a variation of a light level is detected if the measured light level changes by more than 5% in a period of 10 seconds, and a motion is detected if the magnitude of motion is above the threshold M in the same period. The threshold values L, M may be absolute values or relative values, i.e. relative to the previous amount of light or magnitude of motion, respectively.

In the example, there is sufficient correlation between the variation of the light level and the sensed motion. Therefore, the control unit fully disregards the variation of the light level for the purpose of controlling the light sources 10. In other words, at the time A, the amount of artificial light from the light sources 10 is not changed. For example, the control unit 20 may adapt the set point, which originally corresponds to the minimum light level to be maintained, to the current light level after the variation has been detected. Thus, the variation of the light level is compensated by adapting at least one set point, thereby inhibiting a control response to the variation of the light level.

At a later time B, a motion is detected which correlates with an increase of the sensed amount of light. Again, due to a sufficient correlation, the variation of the light level is ignored, and the control unit does not change the amount of artificial light from the light sources 10. Thus, throughout the indicated time span, the level of artificial light emitted from the light sources 10 is constant.

When a variation of the light level correlates with a motion of a person, the actual light level at the area 12 may fall below the minimum light level to be maintained. In the example of Fig. 7, the minimum required light level is then reached again at time B.

This is different in the example of Fig. 8 and Fig. 9, where a longer time span is illustrated. In the illustrated situation, at time A, a motion of a person is detected which correlates with a decrease of the available daylight. As illustrated in Fig. 8, the decrease in available daylight is due to the person controlling the blinds 36 at the window 14.

Similar to Fig. 7, Fig. 9 illustrates a motion signal and a sensed amount of light over time. At time A, because the correlation between the decrease of the light level and the detected motion is sufficient, the control unit 20 disregards the variation of the light level for the purpose of controlling the light sources 10, as explained above. However, it should be noted that the control unit 20 optionally only temporarily inhibits a control response to that variation of the light level. At time B, there is again detected a motion which does correlate with a change of the light level. Unlike the situation of Fig. 7, the light level remains below the minimum light level to be maintained. Thus, after time B, the set point is below the minimum light level to be maintained.

At a time C, the time period C-A during which the available light level is below the minimum light level exceeds a predetermined second time interval T2 of e.g. 10 minutes. Then, in this example, the control unit 20 no longer inhibits the control response to the previous decrease of the light level at time A. For example, the control unit 20 gradually adapts the set point to the original set point, i.e. the minimum required light level. Thus, the light from the light sources 10 is increased in response to the sensed amount of light. A dashed line indicates the fraction of sensed light that is attributed to the incoming daylight. Thus, the control unit 20 reacts to long-term deviations from the light level range to be maintained. For example, the second time interval T2 is at least 3 minutes, preferably at least 10 minutes.

In the example of Figs. 2 and 3, the motion sensor 18 provides a motion signal that not only indicates a magnitude of a detected motion, but also comprises positional information, in particular, directional information about the detected motion.

If positional information is available from the motion sensor 18, the control unit 20 may be adapted to partly inhibit a control response to a variation of a light level, dependent on the positional information. Again, partly ignoring the variation of the light level may be limited to a time span corresponding to a predetermined second time interval.

For example, an amount of compensation of the set point, i.e. an extent to which the control response to the variation of a light level is inhibited, provided that it correlates with a detected motion, may be determined by the control unit 20 in accordance with table 1. The extent of inhibiting the control response is dependent on a distance of the detected motion and an angular direction of the detected motion. TABLE 1

When a motion is detected at a short distance, i.e. close to the motion sensor 18, the variation of the light level is fully ignored if the motion is at 0°, i.e. directly beneath the motion sensor 18. Thus, the control response is fully inhibited (100%). When the motion is detected at a far distance and at an angle of 60°, there is no compensation, and the control response is not inhibited (0%). The motion is assumed to be not associated with the observed light variation. At intermediate distances and/or intermediate angles, the control response is partly inhibited; the variation of the light level is partly compensated by adapting the set point only partly to the then current light level. For example, when a motion is detected at a close distance and at an angle of 30°, 75% of the light variation is ignored. That is, 75% of the difference between the then current light level and the set point is added to the set point for compensation. Note that the above mentioned values of angular directions each represent an angular range.

The values in table 1 are only given for the purpose of illustration, and, in practice, should be adapted to the field of view of the motion sensor 18, the distance of the motion sensor 18 from the area 12, e.g. the height of the ceiling, and, optionally, the reflection properties of the interior within the field of view.

Whereas, in the above example, the extent to which the control response to a variation of a light level is inhibited is dependent on two positional parameters of a detected motion, i.e. a range and a direction, partly inhibiting the control response may also be based on only one positional parameter, e.g. only on distance information, or only on directional information such as information about an angular direction. It may also be based on a magnitude of motion, with a larger magnitude resulting in a larger extent of compensation, or on magnitude and one or more positional parameters of a motion.

The function of the control unit 20 of the system can be described by means of the method illustrated in Fig. 10.

In step 40, "Log light levels", the control unit 20 receives light level signals from the light sensor 16 and motion signals from the motion sensor 18 and logs corresponding light level information and motion information in memories 24, 26. In step 42, "Light levels changed?", the control unit 20 determines whether the light level has changed to such an extent that it exceeds a certain threshold. If this is not the case, the control unit checks whether a previous light level variation has been ignored for a time exceeding a predetermined second time interval or time delay in step 50. If this is not the case, the method returns to step 40.

If, in step 42, it is determined that the light level shows a significant change, similar to the time points A of Fig. 5, Fig. 7 and Fig. 9, the processing unit 28 of the control unit 20 determines whether there is a sufficient correlation in time between a detected motion and the light level variation in step 44, "Correlation with motion?". If the correlation is not sufficient, as in time points A and B of the example of Fig. 5, the method continues with step 46, "Adapt artificial light", and the control unit 20 sets a new artificial light level in order to compensate for the varied amount of sensed light. For example, at time B of Fig. 5, the light output of light sources 10 is reduced. The method returns to step 40.

If, however, in step 44, a sufficient correlation has been determined, e.g. at time A or B of Fig. 7 or Fig. 9, the method continues with step 48, "Adapt set point". The control unit 20 adapts the control set point to the current light level, such that a control response is inhibited. That is, the change of the light level is temporarily ignored. The method continues with step 40 and 42 as described above.

If, in step 50, "Delay completed?", the delay from ignoring a light level variation is exceeded, e.g. at time C of Fig. 9, the original set point is restored in step 52, "Reset set point", and the method continues with step 46. A new artificial light level is set in order to adapt to the amount of sensed light. As illustrated in Fig. 9, the light sources 10 may be controlled to gradually reach the target artificial light level. The method continues with step 40.

If the control unit 20 is adapted to partly inhibit the control response to the variation of the light level, and if, in step 44, a sufficient correlation has been determined, the method continues with step 54, "High relevance of motion?", instead of step 48. The control unit 20 decides whether the control response will be fully or partly inhibited, dependent on positional information about the detected motion. That is, the relevance of the detected motion for the light level variation is estimated. If the control response will be fully inhibited, the method continues with step 48 as described above. If the control response will only be partly inhibited, the set point is partly adapted in step 56, "Adapt set point", and the method continues with step 46. In this case, the new target level for the light sources 10 is calculated as if a smaller variation of the light level was detected. Nevertheless, when the time delay has been reached in step 50, the set point will be reset to the original value, and a new target artificial light level will be set, again, in step 46, based on the current sensed amount of light. Thus, the variation of the light level is only temporarily partly ignored.

For example, if there is a further coincidence of a light level variation and a detected motion while a previous control response is still inhibited, the second time interval will continue to be measured from the previous time of inhibiting the control response.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. 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. 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. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. System for automatically controlling at least one lighting system (11), based on sensing an amount of light in an area (12) and based on detecting motion in a field of view that overlaps said area (12), comprising:

at least one light sensor (16) arranged for sensing an amount of light in said area (12);

at least one motion sensor (18) arranged for detecting motion in said field of view;

a control unit (20) adapted to control the at least one lighting system (11) in response to an amount of light sensed by the at least one light sensor (16),

wherein the control unit (20) is adapted to control the at least one lighting system (1 1), taking into account feedback from light of the at least one lighting system (11) illuminating said area (12) and being sensed by the at least one light sensor (16), and

wherein the control unit (20) is adapted to at least temporarily at least partially inhibit a control response to a variation of an amount of light, when a detected motion and said variation of an amount of light occur within a predetermined time interval (Tl).

2. System according to claim 1, wherein the at least one lighting system (11) comprises at least one light source (10), and

wherein the control unit (20) is adapted to control the at least one light source in response to an amount of light sensed by the at least one light sensor (16), taking into account feedback from light of the at least one lighting source illuminating said area (12) and being sensed by the at least one light sensor (16), and

3. System according to claim 1 or claim 2, wherein the at least one lighting system (11) comprises at least one luminaire (23), which comprises at least one light source (10), and wherein the at least one light sensor (16) and the at least one motion sensor (18) are integrated into the at least one luminaire (23).

4. System according to any one of claims 1 to 3, wherein said field of view substantially comprises said area (12).

5. System according to any one of claims 1 to 4, wherein the at least one light sensor (16) is arranged, relative to said lighting system (11), for letting light from the lighting system (11) illuminate said area (12).

6. System according to any one of claims 1 to 5, wherein said at least partially inhibiting of a control response to a variation of an amount of light comprises at least partially inhibiting the control response for at least a second time interval (T2), wherein said second time interval (T2) is longer than said predetermined time interval (Tl).

7. System according to any one of claims 1 to 6, wherein said at least temporarily at least partially inhibiting of a control response to a variation of an amount of light comprises at least temporarily adapting a control set point and/or at least temporarily setting a correction value for correcting a control input of the control unit (20).

8. System according to any one of claims 1 to 7, wherein the control unit (20) is adapted to at least temporarily at least partially inhibit a control response to a variation of an amount of light, when a detected motion and said variation of an amount of light occur within a predetermined time interval (Tl), and under the further pre-condition that a magnitude of said variation of an amount of light reaches a light level threshold value (L) and/or a magnitude of the detected motion reaches a motion level threshold value (M).

9. System according to any one of claims 1 to 8, wherein the extent of inhibiting said control response is based on at least one of positional information about the detected motion and a magnitude of the detected motion.

10. System according to any one of claims 1 to 9, wherein the control unit (20) is adapted to at least temporarily partially inhibit a control response to a variation of an amount of light, when a detected motion and said variation of an amount of light occur within a predetermined time interval (Tl), and optionally further dependent on at least one of positional information about the detected motion and a magnitude of the detected motion.

11. System according to claim 10, wherein said at least temporarily partially inhibiting of a control response to a variation of an amount of light comprises at least temporarily controlling said at least one lighting system (11) as if the variation of the amount of light was smaller than actually sensed.

12. System according to any one of claims 9 to 11, wherein said positional information comprises at least one of distance information and directional information.

13. Method of automatically controlling at least one lighting system, based on sensing an amount of light in an area (12) and taking into account feedback from light of the at least one lighting system (11) illuminating said area (12), and based on detecting motion in a field of view that overlaps said area (12), wherein the method comprises:

sensing a variation of an amount of light in the area (12), using at least one light sensor (16);

evaluating an output of a motion sensor (18) arranged for detecting motion in said field of a view;

- and, based on a result of the evaluating step, determining whether a detected motion and said variation of an amount of light occur at a predetermined time interval (Tl), and, in this case, at least temporarily at least partially inhibiting of a control response to the variation of an amount of light.