WO2011151796A1

WO2011151796A1 - System and method for lighting control

Info

Publication number: WO2011151796A1
Application number: PCT/IB2011/052415
Authority: WO
Inventors: Ashish Vijay Pandharipande; David Ricardo Caicedo
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-06-03
Filing date: 2011-06-01
Publication date: 2011-12-08

Abstract

A lighting control system (1) and a method for controlling a lighting function from a light source (2) are provided. The lighting control system (1) comprises a transmitter (4) for transmitting a probing signal (5) within a transmitting range and a plurality of receivers (6) for receiving a return signal (7). The return signal (7) is a part of the probing signal (5) that is reflected against a target (8) present within the transmitting range. A processing unit (9) is in communication with the plurality of receivers (6), wherein the processing unit (9) is configured to predictively estimate the location of the target (8) based on the return signal (7). Moreover, the processing unit (9) is configured to control the lighting function of the light source (2) in accordance with the predictively estimated location of the target (8).

Description

System and method for lighting control

FIELD OF THE INVENTION

The present invention relates to a system and a method for lighting control.

BACKGROUND OF THE INVENTION

The use of artificial lighting to achieve practical or aesthetic effects is continuously increasing. Both for indoor and outdoor settings, there are numerous examples of lighting systems including e.g. light bulbs, LEDs, and spot lights for offices, restaurants, museums, advertising boards, homes, shops, shop windows, and so on.

Whatever the light source may be, however, there is a wish to save energy. The saving of energy may be improved by manual control of the light source, e.g. that a person in a room is more attentive to use the lighting only when needed, thereby switching on the light upon arrival and switching off the light when leaving the room.

However, manual control of the lighting may be undesired, inefficient and/or tedious. As an example, for the lighting in e.g. stores, it is advantageous that a lighting control unit is able to turn off or turn on light sources without the operation of the client. As another example, the avoidance of manual control of the lighting may especially be advantageous in some cases such as when there is a plurality of light sources, and the light sources are placed at different locations in a room. A manual operation to switch on or off each one of the plurality of lamps may in this case be inconvenient.

In the light of the above observations, there is an increasing need for automatic lighting systems which can lead to an energy-efficient lighting and, furthermore, which operation is convenient for the user.

In patent document WO-2005/069698, a lighting control related to the detection of occupants is disclosed. Light which is emitted in each local area is uniquely modulated to identify the respective area. The modulated light is detected by wearable occupancy detectors in the local areas, which in turn transmit detector-locator signals to lighting control units, thereby identifying which local areas are occupied. These signals may also uniquely identify the respective detectors, thereby enabling a lighting system controller to determine the number and identities of the detectors in each local area. However, alternative and/or complementary solutions for lighting may be of interest, such that a more energy efficient lighting is provided.

SUMMARY OF THE INVENTION

It is an object of the present invention to mitigate the above problems and to provide a system that provides an improved energy efficiency.

This and other objects are achieved by providing a system having the features defined in the independent claims. Preferred embodiments are defined in the dependent claims.

Hence, according to a first aspect of the present invention, there is provided a lighting control system for controlling a lighting function from at least one light source. The lighting control system comprises a transmitter for transmitting a probing signal within a transmitting range and a plurality of receivers for receiving a return signal. The return signal is a part of the probing signal that is reflected against a target present within the transmitting range. Furthermore, a processing unit is in communication with the plurality of receivers, wherein the processing unit is configured to predictively estimate the location of the target based on the return signal. Moreover, the processing unit is configured to control the lighting function of the light source in accordance with the predictively estimated location of the target.

According to a second aspect of the present invention, there is provided a method for controlling a lighting function from a light source. The method comprises the steps of transmitting a probing signal within a transmitting range, and receiving a return signal. The at least one return signal is a part of the at least one probing signal that is reflected against a target present within the transmitting range. The method further comprises the step of predictively estimating the location of the target based on the return signal.

Moreover, the method comprises the step of controlling the lighting function of the light source in accordance with the predictively estimated location of the target.

Thus, the present invention is based on the idea of providing a lighting control system comprising a processing unit being configured to predictively estimate the location of a target, i.e. that the processing unit is configured to predict the presence and the position of the target. Furthermore, based on the predictive estimation of the location of the target, the processing unit is configured to control the lighting function of the light source.

An advantage of the present invention is that the lighting control system provides a more energy efficient lighting function compared to other prior art systems. The present invention is advantageous compared to prior art techniques which e.g. are based merely on binary occupancy information, i.e. presence/absence detection of a target.

Techniques in which the setting of the lighting is solely based on presence detection of a target limit the lighting control possibilities and result in a lighting which is less effective. On the other hand, the lighting control system of the present invention can predict a location of a target, and the lighting function of a light source may be adapted such that more or less light is provided at the predicted location.

As an example, if a target, e.g. a person, is predictively estimated to be located at a location in a room, a light source may be turned on such that light is shed on that location of the room. This location may be close to e.g. a desk, a book shelf, or a chair, where the person is predicted to be located, and the control of the light source may improve the lighting for the person who e.g. will study at the desk, find a book in the shelf, or sit down in the chair to read.

As a further example, if a person is predictively estimated to be present at a location close to which is a position wherein products or other items are positioned, e.g. shelves in a store or paintings in a museum, the lighting control system may provide a control of the light source at this position based on the estimated location of the person. In this way, the lighting function makes the person attentive to the position lit up by the light source.

Alternatively, the lighting control system may be configured to decrease the lighting at the location wherein the person is predictively estimated to be present, and increase the lighting at a position to which it is desirable that the person is re-oriented.

As a further example, the lighting control system may be configured to achieve uniform lighting at locations wherein the person is predictively estimated to be present, whereas in areas the person is not predicted to be present, the lighting control may be configured to achieve a minimal, or at least reduced or relatively low, lighting. The terms "uniform lighting" should be construed as a lighting in which variations in illumination intensity is below a certain threshold.

The lighting control system comprises a transmitter for transmitting at least one probing signal within a transmitting range. In particular, the lighting system may comprise a plurality of transmitters. The term "transmitting range" may be construed as a region or zone in which the probing signal is able to propagate from the transmitter. In other words, a region or zone behind a target and/or an object may not be accessible for the probing signal, as the target and/or object may cast a "shadow" behind the target and/or object. In such a case, the probing signal does not propagate, or at least does not propagate properly, in this zone or region, and this specific region does not form part of the transmitting range.

Alternatively, the "transmitting range" may be interpreted as a region or zone which is scanned by the probing signal.

The lighting control system further comprises a plurality of receivers for receiving a return signal. Each of the receivers may receive a specific return signal with, e.g., a specific direction-of-arrival (Do A) because of different reflections of the probing signal at the target. Alternatively, the receivers may be considered to receive the same return signal, but, as the receivers are not located exactly at the same place, such a return signal may create different responses in each of the receivers.

Generally, the return signal is a part of the probing signal that is reflected against a target present within the transmitting range. Thus, if a target is present in the region in which a probing signal emitted from the transmitter propagates, the target may reflect the probing signal or at least part of it, thereby creating a return signal. Such a return signal is then received by the plurality of receivers.

The lighting control system further comprises a processing unit in communication with the plurality of receivers. By "communication" it is here meant that the plurality of receivers is able to send information in terms of signals or data to the processing unit.

Furthermore, the processing unit is further configured to predictively estimate the location of the target based on the return signal. By the terms "predictively estimate the location", it is meant that the processing unit may in advance anticipate a location, or at least an approximate location of a target. In other words, the processing unit may forecast the estimate of a location. Previous locations (p®,

may be stored in the processing unit, wherein p represents the location of the target in one, two or three coordinates, and t represents time. The processing unit may be configured to predictively estimate a future location of the target, e.g. based on the formula ρ^^+ί^=ρ^+ΐ(ρ^-ρ^), wherein f is a mathematical function (e.g. a linear filter function). In other words, a future location of a target may be predictively estimated on a current location and past locations of the target. As an example, the processing unit may estimate the location of a target predictively, wherein the target, estimated to be located e.g. at coordinates xi, yi, zi at time and xo, yo, z₀ at time t₀, is estimated to be located e.g. at coordinates x₂, y₂, z₂ at time t₂, wherein t₂ > ti> t₀, and the axes x, y, and z are orthogonal, Cartesian axes. Furthermore, the term "location" should here be construed as a position in e.g. a room, an office, or a store, wherein the target, e.g. a person, is estimated to be located.

Furthermore, the processing unit is further configured to control the lighting function of the at least one light source in accordance with the predictively estimated location of the target. Hence, based on the predictively estimated location of the target, the processing unit may control the lighting function of the light source such that the lighting is adapted with respect to the predictively estimated location of the target.

The terms "control the lighting" may in this context be construed as an "on" or "off switching of the lighting, i.e. that the lighting is turned on or turned off with respect to the predictively estimated location of the target. Alternatively, the terms "control the lighting" may be construed as a dimming of the lighting, i.e. that the intensity of the lighting is gradually increased or decreased with respect to the predictively estimated location of the target. For example, if the lighting control system predictively estimates that a person located in a region A, in which light sources are powered "on" at a maximum power, is on her/his way to another region B in which there is not yet any light source powered "on", the processing unit may be configured to decrease the power of the light source illuminating region A and increase the power of the light source adapted to illuminate region B.

According to an embodiment of the present invention, the processing unit may further be configured to predictively estimate the two-dimensional location of the target. As an example, the processing unit may predictively estimate the target to be located e.g. at coordinates xi, yi. This is advantageous when two-dimensional coordinates of a target are of interest, e.g. to locate a target in a room, wherein e.g. a three-dimensional estimate of the location of a target may be superfluous, and e.g. a one-dimensional estimate of the location of a target may not be enough for the desired accuracy of the estimated location of the target.

According to an embodiment of the present invention, the processing unit may be configured to control the lighting function of the light source as a function of the distance between the predictively estimated location of the target and the light source. Here, the word "distance" should be construed as the absolute distance between the predictively estimated location of the target and the light source in one, two, or three dimensions.

As an example, the distance D between the predictively estimated location of the target e.g. at coordinates xi, yi, z_{l s} and the light source located e.g. at coordinates x₂, y₂,

2 2 2 1 /2

z₂, is D = [(xi- x₂) + (yi-y₂) + (zi-z₂) ] . The processing unit may control the lighting function of the light source based on this distance D, e.g. that the lighting is turned "on" if the target is predictively estimated to be located at a distance D from the target, wherein D is below or equal to a threshold value. In other words, if the target is predictively estimated to be located closer to the light source than this threshold value, the lighting may be turned on. Analogously, if D is above the threshold value, i.e. that the target is predictively estimated to be located further away from the light source than this threshold value, the lighting may be turned "off.

Furthermore, instead of the lighting of the light source being turned "on" or turned "off based on the distance between the predictively estimated location of the target and the light source, the intensity of the light from the light source may be continuously changed based on the distance. As an example, if the target is predictively estimated to be located at a relatively long distance from the light source, the light source may be "dimmed", i.e. have a reduced light intensity. Analogously, if the target is predictively estimated to be located at a relatively short distance from the light source, the light source may be controlled to have a relatively high intensity.

The embodiment is advantageous regarding e.g. the energy efficiency of the lighting control system. If the target is a person, he or she may need lighting from the light source when he or she is close to an area wherein the system has estimated him or her to be, but not in other areas. Examples of this may be a desk in an office, a book shelf in a room, or a showcase in a store. However, when the person is not close to the area which could be lit by the light source, lighting from the light source may not be needed, and energy may thus be saved.

As a numerical example in two dimensions, if the light source is located at coordinates x_ls, y_ls= 1 , 2 and the target is predictively estimated to be located at coordinates xi , y₂= 2, 3, the distance D between the light source and the target is [(l-2)²+ (2-3)²]^1/2 = -1.4 m. If the threshold is 1.5 m, the distance D is shorter than this threshold, and the light source is turned "on". Analogously, if the target instead is predictively estimated to be located at coordinates xi , y₂= 2, 4, the distance D between the light source and the target is [(l-2)²+ (2- 4)²]^1/2 = ~2.2 m, and the lighting may be turned "off. However, instead of a "on or "off control, as in this example, a "dimming" of the lighting may also be feasible, i.e. that the intensity of the lighting is gradually increased or decreased with respect to the location of the target.

In the case of a typical office room, having a length of 4.5 m, a width of 3 m, and a height of 2.5 m, if the predictively estimated location of the target is in a corner of the room and the light source is arranged in the opposite corner, diagonally across the room, the maximum distance between the light source and the predicted location is [(4.5)²+ (3)²+ (2.5)²]^1/2 = ~ 6 m. Even at this distance, the processing unit may control the lighting function of the light source as a function of the distance between the predictively estimated location of the target and the light source.

According to an embodiment of the present invention, the processing unit is further configured to determine a sub-range of the transmitting range, in which sub-range the target is located, for determining the predictively estimated location of the target. As an example, the processing unit may be configured to determine the range of the location of the target firstly by filtering out the return signals from the stationary objects in the background, such as e.g. furniture. Furthermore, the processing unit may be configured to determine the range of the location of the target by moving target indication (MTI). Details about MTI may be found e.g. in Jerry C. Whitaker (2005) The Electronics Handbook, ISBN 0849318890, and such details are incorporated herein by reference. From the results of the MTI, the processing unit may then perform a range processing after downmixing. As downmixing is a known algorithm to the person skilled in the art, the details of the method are omitted.

Furthermore, from the results of the range processing, the processing unit may be further configured to perform an iterative direction-of-arrival (DoA) procedure for the processing of DoAs coming from an unknown number of sources, i.e. targets, wherein DoA denotes the direction from the target to the plurality of receivers. Details about DoA may be found e.g. in E. Tuncer and B. Friedlander (2009) Classical and modern direction-of-arrival estimation, ISBN-13: 978-0-12-374524-8, and such details are incorporated herein by reference.

The advantage of determining a sub-range of the transmitting range, in which sub-range the target is located, is that the predictive estimation of the location of the target is improved, and consequently, the control of the lighting function in accordance with the predictive location of the target is improved.

In addition to performing MTI and DoA operations, the processing unit may be configured to further enhance the accuracy of the predictively estimated location of the target. As an example, such an enhancement may be needed in cases when there is an intermittent detection of a target, i.e. when the return signal reflected against the target is suppressed, or at least reduced. Particularly, if the target is still, the MTI may completely suppress, or at least significantly reduce, the return signal reflected from the target.

To overcome these intermittent detections, the processing unit may be configured to track the target. As it may be expected that the real location of the target is in the predicted location of the target, or in its vicinity, the possibility of the target being further away from the predicted location decreases with the distance between the estimated location and the real location.

In the operation of tracking the target, a movement state model may be used, such as a Markov state model. Moreover, from the movement state model, target velocities may be estimated by using a difference of position vectors at two time instants. According to an embodiment of the present invention, the processing unit may be further configured to predictively estimate the two-dimensional location and velocity of the target such that a trajectory of the target is predictively estimated as a function of time. Furthermore, the processing unit is configured to control the lighting function of the light source in accordance with the trajectory. Hence, in this embodiment, the processing unit is configured to predictively estimate both the location of the target e.g. in two dimensions, e.g. xi, yi, and the velocity of the target in two dimensions, e.g. v_x, v_y, and further predictively estimate a trajectory of the target as a function of time, and control the lighting function of the light source in accordance with the trajectory.

As an example, from the estimated location and the velocity of the target, the processing unit may predictively estimate the location at a later time t₂ by integration. As an example, the processing unit may predictively estimate the location x₂, y₂ of the target at a later time t₂ by integration, e.g. x₂, y₂ = xi, yi + (v_x, v_y)(t₂ - ti).

By the term "trajectory", it is here meant e.g. a path, a route or a way.

Furthermore, as the trajectory of the target is predictively estimated as a function of time, it is meant that the target, predictively estimated at e.g. xi, yi at time t_{l s} is estimated to be at e.g. x₂, y₂ at time t₂, and further at e.g. x₃, y₃ at time t₃, etc.

As an example, the trajectory of the target may be predictively estimated to start e.g. close to the door of the room, continue to e.g. a desk at one end of the room, and further continue back to the door.

Thus, based on the predictively estimated trajectory of the target, the processing unit may adapt the lighting of the light source such that a desired lighting is provided along the trajectory.

The embodiment is advantageous regarding e.g. the energy efficiency of the lighting control system. The lighting function of the light source may be controlled such that if the target is predictively estimated to be present at e.g. xi, yi at time ti and at e.g. x₂, y₂ at time t₂, wherein the positions are comprised in the estimated trajectory of the target, the processing unit may control the lighting function such that a light source relatively close to the coordinates xi, yi may be turned "on" at time t_ls or at a time close to t_ls and that a light source relatively close to the coordinates x₂, y₂ may be turned "on" at time t₂, or at a time close to t₂. Analogously, the processing unit may be configured to turn "off the lighting of the respective light sources when the target is relatively distant from the predictively estimated locations xi, yi at time ti and at e.g. x₂, y₂ at time t₂.

Furthermore, a light source relatively close to the coordinates x₂, y₂ may be turned "on" at time t_ls a time between and t₂, or t₂. Thus, as the target is predictively estimated to be located at x₂, y₂ at time t₂, the processing unit may control the lighting function such that the light source may be turned "on" even before the target is estimated to reach this location.

This has the further advantage that, if the target is a person, the control of the lighting function of the light source may in advance "light up" the estimated trajectory of the person. Another advantage of the embodiment is that the person may turn his attention to areas lit up by the light source based on the predictively estimated trajectory of the target. As an example, a light source in a store may emit light to an area wherein a product is placed, such that a person, whose estimated location is predicted to be in a vicinity of the area, turns his attention to the product on which the light source emits light. In other words, the control may attract customers to specific areas. Alternatively, the control of the lighting function may be set such that light is emitted within the interior of a container of products, wherein the container is located in an area in e.g. a store. An example of such a container of products may be a refrigerating system such as e.g. a freezer containing frozen food.

Furthermore, the control of the lighting function may be applied indoor as well as outdoor. As an example of an outdoor lighting function, dimming of neighboring lighting sources may be controlled depending on the predictively estimated trajectories of the target.

According to an embodiment of the present invention, the processing unit is further configured to predictively estimate the two-dimensional location and/or the velocity of the target based on a previous predictively estimated location of the target. The

predictively estimated location may be estimated from a location or locations estimated at one or several earlier time steps. As an example, the predictively estimated location may in this way be modeled by a Markov chain, and the model may further comprise a Gaussian noise vector.

Additionally, the predictively estimated location of the target may be further improved by combining it with a current estimate of location of the target.

Furthermore, the velocity of the target may be estimated based on previous predictively estimated locations of the target. As an example, the velocity may be estimated by subtracting two in time adjacent, estimated locations of the target, and divide this distance with the time to yield the estimated velocity.

According to an embodiment of the present invention, the processing unit may be further configured to estimate boundaries of the trajectory of the target, wherein the boundaries delimit. By "boundaries", it is meant that the trajectory of the target have boundaries beyond which a trajectory is infeasible. The boundaries may be obtained during installation or under quiet-period measurements, i.e. when there are no moving targets within the space under observation, e.g. a room. The quiet period may also be used to set detection thresholds for range processing by measuring the received power levels which correspond to noise. In particular, different thresholds may be set depending on the range and the angle of the return signals.

As an example, boundaries of the trajectory of the target may delimit locations that fall outside dimensions of the room. In the case of a typical office room, wherein an example of the length x of the room may be 4.5 m and the width y of the room may be 3 m, the unit is configured to predictively estimate boundaries of the trajectory of the target within the room, such as |x| <= (4.5 m / 2) and |y| <= (3 m / 2), with centered coordinates.

An advantage with this embodiment is that if a target is predictively estimated to be located beyond an estimated boundary, e.g. outside a room, this estimate of target location becomes infeasible. Hence, this improves the predictive estimate of the location of the target, and consequently, improves the control of the lighting function of the light source.

As another example, the processing unit may be further configured to estimate boundaries of the trajectory of the target based on measurements of stationary objects within the room, such that e.g. a desk, a drawer, or a cupboard delimit the feasible trajectory of the target within the room.

Here, an advantage of this is that if a target is predictively estimated to be located where a stationary object is provided, this estimate of target location becomes infeasible. Furthermore, the estimated boundaries of the trajectory of the target provide the advantage of delimiting the broadness of the transmitting range. By this, it is meant that no probing signals are needed towards locations wherein a stationary object is provided, as a target cannot be located in the same location as the stationary object.

For the estimate of boundaries of the trajectory of the target, the processing unit may be in communication with the transmitter such that the processing unit may delimit the broadness of the transmitting range. Furthermore, the processing unit may be further configured to distinguish between a moving object and a stationary object. As an example, a sequence of probing signals may be transmitted from the transmitter, and an elapsed time from transmission of the probing signal to reception of the "echo" of the return signal may be estimated.

The word "echo" should here be construed as the response of the probing signal after being reflected on the object. The echoes generated from stationary objects do not vary in their elapsed time, nor in the phase, from pulse to pulse, and hence, the processing unit may distinguish between a moving object and a stationary object. As a further example, two probing signals may be transmitted, and the elapsed time between the return signals received by the plurality of receivers may be used by the processing unit to distinguish between a moving object and a stationary object.

By distinguishing between a moving object and a stationary object, the predictively estimated trajectory of the target may be even further improved. The processing unit may control the lighting function in accordance with the predictively estimated location of the object which moves, such as e.g. a person, compared to a stationary object, e.g. a desk.

According to an embodiment of the present invention, the processing unit may be further configured to estimate the number of targets present within the transmitting range based on directional reception of the return signal. As an example, this may be performed by "beamforming" and "DoA" processing. Details about beamforming may be found e.g. in H. L. Van Trees (2002) Optimum Array Processing, ISBN 0471093904, and such details are incorporated herein by reference.

An advantage with the processing unit being further configured to estimate the number of targets present within the transmitting range is that the control of the lighting function may be even further improved. As an example, the lighting function may be adapted to be controlled for the presence of several targets in a room, instead of a single target.

Furthermore, systems such as e.g. heating, ventilation and air-condition (HVAC) may be controlled based on the estimation of the number of targets. As an example, the heating may be turned down if there is a large number of people, i.e. targets, present and increased if there is a small number of targets present. The control of a heating, ventilation and/or air-condition system may be combined with the control of a lighting function of at least one light source such as described in any one of the herein described embodiments. However, it may also be envisaged that the control of the heating, ventilation and/or air- condition system may be performed independently of the control of any lighting function. Hence, although the control system of the present invention is described in connection with the control of a lighting function of at least one light source, it is also envisaged that the control system described herein may be employed for controlling a heating, ventilation and/or air-condition function.

Thus, according to a third aspect of the present invention, a control system for controlling a heating, ventilation and/or air-condition function of a heating, ventilation and/or air-condition system is provided. The control system may comprise at least one transmitter, a plurality of receivers and a processing unit in communication with the plurality of receivers. The transmitter is configured to transmit at least one probing signal within a transmitting range and the plurality of receivers is configured to receive at least one return signal. The return signal is a part of the probing signal that is reflected against a target present within the transmitting range. The processing unit is configured to estimate a number of targets based on the return signal(s) and is also configured to control the heating, ventilation and/or air- condition function of the heating, ventilation and/or air-condition system in accordance with the estimated number of targets.

As mentioned above, the processing unit may be further configured to estimate the number of targets present within the transmitting range based on directional reception of the return signal (see above examples with "beamforming" and "DoA" processing, wherein details about beamforming may be found e.g. in H. L. Van Trees (2002) Optimum Array Processing, ISBN 0471093904, herein incorporated by reference).

Any embodiments described with reference to the lighting control system may be combined with the control system according to the third aspect of the present invention, in particular any embodiments related to the estimation of the number of targets.

Turning back to the lighting control system of the present invention, according to an embodiment, the processing unit may be further configured to predictively estimate the two dimensional-location of the target from a plurality of return signals from the same target, the return signal being received by the receivers. Thus, in the case that a target reflects several return signals which the receivers receive, the processing unit is configured to predictively estimate the location in two dimensions of the target based on this plurality of return signals.

As an example, the predictively estimate of the location in two dimensions of the target from a plurality of return signals from the same target may be performed by a "track-before-detect" algorithm (TBD). Details about TBD may be found e.g. in David L. Hall and James Llinas (2001) Handbook of Multisensor Data Fusion, ISBN 0849323797. and such details are incorporated herein by reference.

As a further example, the processing unit may be further configured to predictively estimate the location of the target based on a past history of locations of the target at past instants of time, and combining these using a predictive movement model of the target. Further, this estimate can be improved by combining it with a current estimate of the location of the target.

The embodiment of target location estimation from a plurality of return signals is beneficial as the processing unit may control the lighting function based on only one estimated location for each target, instead of several.

As an example, the transmitter may be omni-directional and the plurality of receivers may be omni-directional. By "omni-directional", it is here meant that the transmitter is able to transmit probing signals in every direction, and/or that the plurality of receivers are able to receive return signals from every direction. This is advantageous as it increases the possibility to estimate the location of a target compared to systems comprising transmitters/receivers which are only operational in specific directions. Hence, the control of the lighting function may be even further improved.

According to an embodiment of the present invention, the transmitter may be arranged to transmit a probing signal at an ultrasonic frequency, and the plurality of receivers may be arranged to receive a return signal at an ultrasonic frequency.

Thus, the at least one transmitter may be arranged to transmit at least one probing signal at an ultrasonic frequency, i.e. at a frequency above 20 kHz which is inaudible for human beings, whereas the plurality of receivers are arranged to receive a return signal at an ultrasonic frequency.

An advantage of this embodiment is that the receiver is arranged to receive a return signal within the same frequency range as the transmitted probing signal. Furthermore, as the frequency range for the probing signal and return signal, respectively, is above 20 kHz, there is no disturbing sound for humans. As a numerical example, if an ultrasonic frequency of f_c= 40 kHz is used for the probing signal, the wavelength of the probing signal is λ = vJf_c = 8.6 mm, wherein the speed of sound is v_s = 344 m/s.

According to an embodiment of the present invention, the plurality of receivers may be arranged in a linear, rectangular, or circular array. As an example, the plurality of receivers may be spaced equally in a linear array, in a line along the x-axis, e.g. on a wall of a room. The separation dm between two adjacent receivers or sensors may e.g. be such that no grating lobes are observed in the transmitting range. With the same numerical example as that described above, dm = 4.3 mm.

Furthermore, a linear array may be arranged at a height which is typically above various stationary objects present in a room, such as e.g. furniture and equipment, which is advantageous in that the average of the transmitting range of the transmitter is increased, thereby improving the estimate of the location of the target

According to an embodiment of the present invention, the processing unit may be further configured to determine an elapsed time and/or a phase shift based on one probing signal and/or the return signal.

By "elapsed time", it is meant the time elapsed from the time when a probing signal is transmitted from the transmitter to the time when a return signal is received by the plurality of receivers. As a numerical example, for a target provided at 5 m from both the transmitter and the plurality of receivers, the elapsed time T is 2*5 / v_s= ~30 ms.

Furthermore, by "phase shift" it is here meant the phase shift of the return signal, i.e. phase difference between the return signal for the plurality of receivers. As an example, for a "far field" assumption, i.e. an approximation that a target is assumed to be located at a distance D far away from the array of receivers, wherein dm « D, the phase shift depends only on the angle of arrival, or, analogously, on the direction of arrival, of the return signal and the configuration of the receivers or sensors.

Hence, with a linear array of receivers, the location of a target may be estimated even more accurately, further improving the control of the lighting function of the light source. According to an embodiment of the present invention, the processing unit may be further configured to determine a change in frequency based on the probing signal and the return signal. As an example, the velocity of the target may be estimated by means of the shift in frequency on a received return signal from a probing signal known as the Doppler effect.

As the lighting control system of the present invention is advantageous in that it improves energy efficiency, the present invention may therefore advantageously be implemented for a lighting arrangement comprising a light source and a lighting control system for controlling a lighting function of the light source in accordance with any one of the preceding embodiments.

According to the second aspect of the present invention, the method may comprise range processing, iterative DoA for processing DoAs at ranges obtained by the range processing, distinguishing between moving objects and stationary objects, tracking based on models comprising estimation of predicted locations based on past position vectors, and limit processing based on measurements of stationary objects and room dimensions.

It will be appreciated that the specific embodiments and any additional features described above with reference to the lighting control system are likewise applicable and combinable with the method according to the second aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing a currently preferred embodiment of the invention, wherein:

Fig. 1 is a schematic illustration of a lighting control system for controlling a lighting function,

Fig. 2 is a view of a transmitter and a plurality of receivers,

Fig. 3 is a view of a trajectory of a target, and

Fig. 4 is a schematic block diagram of the lighting control system.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, the present invention is described with reference to a lighting control system for controlling a lighting function from a light source, the control system comprising a transmitter, a plurality of receivers and a processing unit.

Fig. 1 is a schematic illustration of a lighting control system 1 for controlling a lighting function from a light source 2. The light source 2 is positioned in a room 3 with length 1, width w and height h.

On a wall of the room 3 is positioned a transmitter 4 for transmitting a probing signal 5 within a transmitting range (or a plurality of transmitters transmitting separate probing signals). The transmitter 4 is positioned approximately half way up on the wall. Close to the transmitter 4 on the wall of the room 3 is positioned a plurality of receivers 6. The transmitter 4 and the plurality of receivers 6 may be separated. Alternatively, the transmitter 4 and the plurality of receivers 6 may be integrated in one single

transmitter/receiver arrangement.

The probing signal 5 may be reflected against a target 8 present within the transmitting range, thereby resulting in a return signal 7. Here, the probing signal 5 is reflected on a target 8, schematically depicted as a person, who is positioned approximately in the middle of the room 3. The probing signal 5, transmitted by the transmitter 4, may be a series of pulsed sinusoids.

A processing unit 9 is in communication with the plurality of receivers 6 and is further connected to the light source 2. The processing unit 9 is configured to predictively estimate the location of the target 8 based on the return signal 7. Furthermore, the processing unit 9 is configured to control the lighting function of the light source 2 in accordance with the predictively estimated location of the target 8.

Thus, the lighting control system 1 comprises a processing unit 9 being configured to predictively estimate the location of a target 8 in the room 3 and to control the lighting function of the light source 2 consequently. The processing unit may comprise a digital signal processor (DSP) and/or a microcontroller wherein data from the plurality of receivers 6 may be stored and/or processed.

The processing unit 9 may further be configured to control the lighting function of the light source 2 based on a distance 10 between the predictively estimated location of the target 8 and the light source 2. As an example, the lighting may be turned "on" if the target 8 is predictively estimated to be located at a distance 10 from the target 8, wherein 10 is below or within a threshold value. In other words, if the target 8 is predictively estimated to be located closer to the light source 2 than this threshold value, the light source 2 may be turned on. Analogously, if the distance 10 is above the threshold value, i.e. that the target 8 is predictively estimated to be located further away from the light source 2 than this threshold value, the lighting may be turned "off. In other words, if the target 8 is

predictively estimated to be far from the light source 2 in the room 3, the light source 2 is turned "off. However, if the target 8 is close to the light source 2, it is turned "on".

Alternatively, instead of the lighting function of the light source 2 being turned "on" or turned "off based on the distance 10 between the predictively estimated location of the target 8 and the light source 2, the intensity of the light from the light source 2 may be continuously changed based on the distance 10. As an example, if the target 8 is predictively estimated to be located at a relatively long distance 10 from the light source 2, the light source 2 may be "dimmed", i.e. have a reduced light intensity. Analogously, if the target 8 is predictively estimated to be located at a relatively short distance 10 from the light source 2, the light source 2 may be controlled to have a relatively high intensity, i.e. an increase in intensity.

Fig. 2 is a view of a transmitter 4 which is positioned above a plurality of receivers 6. However, the transmitter 4 and the plurality of receivers 6 could alternatively be closely positioned, or positioned at a longer distance from each other. Furthermore, the transmitter 4 and the plurality of receivers 6 may be a single integrated transceiver which acts both as a transmitter and as a receiver.

The transmitter 4 for transmitting the probing signal may be provided on the side wall of the room 3, preferably on a height substantially above furniture or the like, present in the room 3. However, the transmitter/receiver could be provided on any wall of the room 3, e.g., in the ceiling. If the transmitter/receiver is placed in the ceiling, 3-D localization may be possible.

The plurality of receivers 6 for receiving return signals are provided in a linear array of eight receivers, the array being horizontally elongated.

Fig. 3 is a view of a trajectory 11 of a target 8 in a room 3 which is

approximately 4.5 m long and 3 m wide. The transmitter 4 and the plurality of receivers 6 are located on the middle of the wall at the left hand side of the room 3. Close to the plurality of receivers 6 is provided a light source 2.

As shown by the trajectory 11 marked by a number of stars, the target 8, depicted as a person, enters the room 3 from approximately the middle of the long side of the room 3, or, expressed in coordinates of Fig. 3, from x=2.8, y= -1.4. The person then turns left and walks to the left side of the room 3 towards the short end of the room 3, at x=0.5, y=0.

From there, the target 8 turns right and walks along the long side of the room 3 opposite the long side from which the person entered the room 3. The target 8 then exits the room 3 at x=4.5, y=0.5, at the right side of the room 3.

As the processing unit 9 is configured to predictively estimate the location and the velocity in two dimensions of the target 8 in the room 3, a trajectory 12 of the target is predictively estimated as a function of time. The result of an experiment is shown in Fig. 3, wherein the estimated trajectory 12, shown as a number of asterisks, closely follows the real trajectory 11 of the target 8 in the room 3. Thus, the processing unit 9 may accurately predict the trajectory of the target 8, and control the lighting function of the light source 2 such that a convenient light is generated for the target 8.

When the target 8 enters the room 3, the light source 2 may be turned "on". Alternatively, the light source 2 may be turned "on" as the target 8 moves in the direction of the light source 2, as depicted. Analogously, the light source 2 may be turned "off when the target 8 leaves the room 3.

Furthermore, corridor lighting (not shown) may be predictively activated when the target 8 leaves the room 3. If the target 8 occupies a certain location in the room 3 for a certain duration of time, the light source 2 and/or other focused/task-based lighting may be activated.

Along approximately half of the long side of the room 3, to the left of the location where the target 8 enters the room, is shown a rectangular boundary 13 which is about 2.2 m long and 0.3 m wide. Two similar rectangular boundaries 13 of 2 m x 0.3 m and 2.2 m x 0.5 m, respectively, are depicted along the opposite wall of the room 3. These boundaries 13 may be interpreted as being stationary objects within the room, such as e.g. a desk, a drawer, or a cupboard, which delimit the feasible trajectory 11 of the target 8 within the room. The processing unit 9 may estimate these boundaries 13 during installation or under quiet-period measurements, i.e. when there are no moving targets 8 within the room 3 under observation.

Furthermore, the processing unit 9 may delimit locations 14 that fall outside the dimensions of the room 3. These locations 14 are shown as crosses in Fig. 3 outside the long ends and one short end of the room 3.

Fig. 4 is a schematic block diagram of the lighting control system 1. A block representing the transmitter 4 and the plurality of receivers 6 is attached to a block representing the processing unit 9, i.e. that the processing unit 9 is in communication with the transmitter 4 and the plurality of receivers 6.

The processing unit 9 is configured to predictively estimate the location of a target based on the return signal from the plurality of receivers 6 and is furthermore configured for a lighting control 15. The lighting control 15 may be a separate unit, or be integrated with the processing unit 9. The lighting control 15 may control a light source or lighting system 16, in accordance with the predictively estimated location of the target. The lighting control 15 may be any kind of control related to the control of the light source, such as e.g. a gradual increase/decrease of the light source intensity, or "on/off modes.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. The described embodiments are therefore not intended to limit the scope of the invention, as defined by the appended claims.

For example, the array and number of receivers 6 may be different from that shown in Fig. 2. As an example, the numbers and the sizes of the plurality of receivers 6, as well as the distances between them, may vary. The same holds for the transmitter 4, which position and/or size may be different from that depicted. Furthermore, the trajectory 11, and the respective estimated trajectory 12 of the target 8 are shown in Fig. 3 as an example, and any other trajectories within the room 3 may be feasible such that the lighting function of the light source may be controlled in accordance with the predictively estimated location of the target. The boundaries 12 in terms of furniture and size of the room 3 may also be different, e.g. different shaped furniture in a larger/smaller room 3 with other dimensions than the rectangular shape depicted.

Claims

CLAIMS:

1. A lighting control system (1) for controlling a lighting function of a light source (2), comprising:

at least one transmitter (4) for transmitting a probing signal (5) within a transmitting range,

- a plurality of receivers (6) for receiving a return signal (7) that is created by reflection of the probing signal (5) against a target (8) present within the transmitting range, and

a processing unit (9) in communication with the plurality of receivers (6), wherein the processing unit (9) is configured to predictively estimate the location of the target (8) based on the return signal (7), and to control the lighting function of the light source (2) in accordance with the predictively estimated location of the target (8).

2. The lighting control system (1) as claimed in claim 1, wherein the processing unit (9) is further configured to predictively estimate the two-dimensional location of the target (8).

3. The lighting control system (1) as claimed in claim 1 or 2, wherein the processing unit (9) is further configured to control the lighting function of the light source (2) as a function of the distance (10) between the predictively estimated location of the target (8) and the light source (2).

4. The lighting control system (1) as claimed in any one of the preceding claims, wherein the processing unit (9) is further configured to determine a sub-range of the transmitting range, in which sub-range the target (8) is located, for determining the predictively estimated location of the target (8).

5. The lighting control system (1) as claimed in claim 2, wherein the processing unit (9) is further configured to predictively estimate the velocity of the target (8) such that a trajectory (12) of the target (8) is predictively estimated as a function of time, and wherein the processing unit (9) is further configured to control the lighting function of the light source (2) in accordance with the trajectory (12).

6. The lighting control system (1) as claimed in claim 5, wherein the processing unit (9) is configured to predictively estimate the two-dimensional location and/or velocity of the target (8) based on a previous predictively estimated location of the target (8).

7. The lighting control system (1) as claimed in claim 5, wherein the processing unit (9) is further configured to estimate boundaries (13) of the trajectory (12) of the target (8), wherein the boundaries (13) delimit the trajectory (12).

8. The lighting control system (1) as claimed in any of the preceding claims, wherein said processing unit (9) is further configured to estimate the number of targets (8) present within the transmitting range based on directional reception of the return signal (7).

9. The lighting control system (1) as claimed in claim 2, wherein the processing unit (9) is configured to predictively estimate the two-dimensional location of the target (8) from a plurality of return signals (7) from the same target (8), the plurality of return signals (7) being received by the plurality of receivers (6).

10. The lighting control system (1) as claimed in any one of the preceding claims, wherein the transmitter (4) is arranged to transmit a probing signal (5) at an ultrasonic frequency, and wherein the plurality of receivers (6) are arranged to receive a return signal (7) at the ultrasonic frequency.

11. The lighting control system (1) as claimed in any one of the preceding claims, wherein the plurality of receivers (6) are arranged in a linear, rectangular or circular array.

12. The lighting control system (1) as claimed in any one of the preceding claims, wherein the processing unit (9) is further configured to determine an elapsed time and a phase shift based on the probing signal (5) and/or the return signal (7).

13. The lighting control system (1) as claimed in any one of the preceding claims, wherein the processing unit (9) is further configured to determine a change in frequency based on the probing signal (5) and the return signal (7).

14. A method for controlling a lighting function of a light source (2), comprising the steps of:

transmitting a probing signal (5) within a transmitting range;

receiving a return signal (7) that is created by reflection of the probing signal (5) against a target (8) present within the transmitting range,

- predictively estimating the location of the target (8) based on the return signal

(7) , and

controlling the lighting function of the light source (2) in accordance with the predictively estimated location of the target (8).

15. A control system for controlling a heating, ventilation and/or air-condition function of a heating, ventilation and/or air-condition system, comprising:

a transmitter (4) for transmitting a probing signal (5) within a transmitting range,

a plurality of receivers (6) for receiving a return signal (7) that is created by reflection of the probing signal (5) against a target (8) present within the transmitting range, and

a processing unit (9) in communication with the plurality of receivers (6), wherein the processing unit (9) is configured to estimate a number of targets

(8) based on the return signal (7), and to control the heating, ventilation and/or air-condition function of the heating, ventilation and/or air-condition system in accordance with the estimated number of targets (8).