WO2014097072A1

WO2014097072A1 - System and method for occupancy detection

Info

Publication number: WO2014097072A1
Application number: PCT/IB2013/060867
Authority: WO
Inventors: Ingrid Christina Maria Flinsenberg; Leszek Holenderski; Alexandre Georgievich SINITSYN
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2012-12-18
Filing date: 2013-12-12
Publication date: 2014-06-26
Anticipated expiration: 2015-06-18

Abstract

The present invention relates generally to the field of occupancy detection, and more particularly to an occupancy detection system and a corresponding method suitable for a presence controlled system, which provide a desired operation state of the presence controlled system while balancing a comfort level and energy consumption of the presence controlled system. A method for controlling an occupancy detection system 10 in a presence controlled system 20 is provided. The occupancy detection system 10 comprises a presence sensor 2 for providing presence sensor data, upon which a current state, a system property, of the presence controlled system is estimated. The system property may be energy consumption, comfort level, or a desired balance between the energy consumption and the comfort level. An operating parameter of the occupancy detection system, e.g. a delay, is then altered based on the estimated value and a target level of that system property.

Description

System and method for occupancy detection

FIELD OF THE INVENTION

The present invention relates generally to the field of occupancy detection, and more particularly to an occupancy detection system and a corresponding method suitable for a presence controlled system.

BACKGROUND OF THE INVENTION

Control systems for automatically control lighting and ventilation systems, or heating, ventilation, and air condition systems (HVAC), often rely on occupancy detectors to maximize correct, efficient and timely delivery of light and air in the environment. A main concern of occupancy detectors for lighting control is to ensure that lighting is promptly switched on when a person enters a given environment. In addition, current lighting solutions mostly rely on presence sensors to turn off the light when the room is unoccupied thereby saving energy. Cheap and efficient solutions to deliver on this goal consist of Passive Infrared Sensors (PIR), RADARs or SONARs. These are able of quickly detecting movements in the environment while respecting privacy (as opposed to cameras). Their limitation lies however in the lack of sensitivity to small movements. In office environments where workers can remain largely immobile for large periods or time, e.g. reading, typing, etc., these sensors may erroneously signal an empty room to the control system. This is due to the fact that such sensors signal an empty room after no movement has been recorded over the last period, the duration of that period which can usually be set by the user. This error is very disruptive and frustrating when lighting is mistakenly switched off and seriously lowers the experienced comfort level of the lighting system. To reduce the risk of turning off the lights too early when no motion is being detected but persons are still in the area, the typical presence sensing based lighting control solution has a delay built in of 15 minutes during which the lights remain on after the last movement was detected. To further reduce energy consumption, this delay can be reduced; but this also increases the risk of erroneously signaling an empty room to the control system.

US 7411489 Bl, discloses an occupancy sensor system comprising a self- adjusting dual technology occupancy sensor (infrared detection and ultrasonic detection), which includes a combination of real time adjustments and fault detection to optimize the sensitivity and time delay settings of the occupancy sensor system. The occupancy sensor is able to activate upon sensing the occupancy of an area, to maintain activation when sensing continuing occupancy of the area, and to deactivate when determining that there is no occupancy of the area. If the occupancy sensor system determines that it made a mistake in activating or deactivating, it adjusts the time delay and/or sensitivity. The step of determining occupancy of the area, is in addition to detecting movement in the room further based on detecting if a person leaves the room by issuing a signal when a door to the space is closed. SUMMARY OF THE INVENTION

It is an object of the present invention to at least provide an alternative and improved method and system for occupancy detection in a presence controlled system.

Further it would be advantageous to achieve occupancy detection that provides reliable occupancy detection, for which events of erroneously determining the room as 'empty' can be minimized. It would also be desirable to provide occupancy detection in a presence controlled system which is dynamical and which provides a desired operation state of the presence controlled system while balancing comfort level and energy consumption of the presence controlled system.

To better address one or more of these concerns, a method and system for occupancy detection of the present invention as defined in the appended independent claim is presented. Preferred embodiments are set forth in the dependent claims and in the following description and drawings.

According to a first aspect of the invention, there is provided a method of controlling an occupancy detection system, the occupancy detection system being suitable for a presence controlled system, the method comprising: receiving presence sensor data, and for a first system property of said presence controlled system: providing an estimated value of the first system property based on the presence sensor data, and obtaining a target value of the first system property. The method further comprises varying an operating parameter of the occupancy detection system in response to determining that the estimated value of the first system property is not in close proximity to the target value of the first system property.

Thus, there is provided a method of controlling an occupancy detection system which advantageously provides a variable operating parameter of the occupancy detection system, being for instance a delay parameter for setting an occupancy state of the occupancy detection system to 'empty' after a last presence event is detected, or a sampling frequency of the occupancy detection system. The operating parameter is altered in response to the current operation state of a selected system property of the presence controlled system. Since the current system property of the presence controlled system is estimated based on presence sensor data, advantageously a measure of the operation state can be associated with a current comfort level of the presence controlled system, and the operating parameter is thus adjusted to find a balance between this estimated operation state associated with a comfort level and a target value of the same. That is, rather than adapting system settings in order to, say, minimize or eliminate occurrences of 'false offs' (switching off lights in an area due to detecting no occupancy there, when the area is in fact occupied), e.g. as described in US 7411489 B l, embodiments described herein may treat reducing 'false offs' as one objective in a multi-objective optimization. For instance, in an embodiment a comfort level (which may be assumed to be inversely proportional to the number of 'false offs') may be balanced against energy consumption to arrive at a solution wherein some 'false offs' will be allowed to occur in order to achieve improved energy savings.

The estimated value of the first system property, being for instance the comfort level in a presence controlled lighting system, may be determined statistically using the presence sensor data by identifying occurrences where the user reacts to light switching off while the user is still in the area/office, or by determining the likelihood of turning the lights off when there are still people in the office. Also the energy consumption of the presence controlled system may be estimated based on presence sensor data by utilizing the likelihood of wrongly turning light off when there are still people present in the office (which is associated with the comfort level of the presence controlled system). This will be described in greater detail in the detailed description. When a higher comfort level is desired in the presence controlled system, the operating parameter of the occupancy system is adjusted so as to provide presence sensor data indicating such higher comfort level, e.g. by increasing the delay as defined above, and thereby decreasing the number of incidents of wrongly turning the lights off while there is still people in the office. This is done at the cost of energy saving, since the higher comfort level will also increase the energy consumption in the presence controlled system.

Estimating the current operation state of the presence controlled system, i.e. providing an estimated value of the first system property based on the presence sensor data is further advantageous since there is no need for directly measuring the first system property. The presence data is originating from the occupancy detection system, and may be received directly from the presence sensor or may be retrieved from a buffer or other storage unit. The presence controlled system is preferably a lighting system or a HVAC system or a combination thereof. However, in practice the method is applicable in any system which benefit from being controlled based on the presence in the room or building where it is installed.

According to an embodiment of the method, the first system property is a comfort level, energy consumption, or a desired balance between the comfort level and the energy consumption. Thereby, the presence controlled system may be optimized with respect to energy consumption, comfort level or a balance between the two. The method may be implemented to continuously objectively monitor both the comfort level as well as the energy consumption of for instance a presence controlled lighting system using presence sensing data of that lighting system, and may adapt the lighting control based on the desired balance between comfort and energy. This optimization may be done per area/office with a plurality of sensors or a single sensor and per time frame (morning, lunch break, base working time, evening etc.).

According to an embodiment of the method, the target value of the first system property is derived based on at least one a target value of a second system property of the presence controlled system, or is obtained as external data. For instance, if the target value of the first system property is a target comfort level, then the second target property may be the target energy consumption, or vice versa. The target value of the second system property may be estimated based on a requested balance between the estimated comfort level and the energy consumption of the presence controlled system, or may be selected based on for instance a room type. According to an embodiment of the method, the first system property is energy consumption, and the target level of the energy consumption is based on a target level of the comfort level of the presence controlled system.

According to an embodiment of the method, the operating parameter is a delay parameter for setting an occupancy state of the occupancy detection system to 'empty' after a last presence event is detected.

According to an embodiment of the method, the presence sensor data comprises a set of presence data collected during a predetermined time period, from which a presence pattern is derived, wherein the estimated first system property is based on the presence pattern.

By utilizing historic presence sensor data of the presence sensing system, at least a day or preferably some weeks, a typical presence pattern of for instance an office is derived. In particular the pattern may be derived to mirror a typical presence pattern of the office during different workdays, the weekend etc. Based on this typical pattern, an estimate of the comfort level (or other system property) for a set of occupancy detector parameters is derived. This way the presence detector parameters of the occupancy detection system can be set to match the corresponding presence pattern. As an example a presence detector parameter corresponding to a delay, e.g. a definite time period which should pass after a last detected movement before determining a room to be empty, is set to a low value during times of typically low presence, and higher during times the office is typically fully occupied. By continuously updating the typical presence pattern, the delay values can also adapt to changing habits of the occupants, or change of occupants over time.

Utilizing historic presence sensor data is further advantageous for instance in internet protocol (IP) controlled lighting systems, which technique facilitates storage and analysis of presence data of the lighting system. This stored data is here used to further optimize the lighting control and to reduce the delay based on the recorded occupancy patterns.

According to an embodiment of the method, the presence pattern is derived with respect to a number of time instances, and the step of varying the operating parameter of the occupancy detection system comprises determining a set of operating parameters of the occupancy detection system corresponding to a preselected set of the time instances t.

According to an embodiment of the method, the external data is received from a user interface or an external database. External data may comprise for instance timing protocols for different target comfort levels for different rooms, and for different hours etc.

According to an embodiment of the method, the step of providing the estimated system property is based on determining a likelihood of the occupancy detection system wrongly setting the occupancy state to 'empty' after a last presence event is detected.

According to an embodiment of the method, the first target system property is estimated based on the presence sensor data and the operating parameter.

According to a second aspect of the invention, there is provided an occupancy detection system suitable for a presence controlled system. The occupancy detection system comprises a presence sensor for providing presence sensor data, a control unit configured for receiving presence sensor data. The processing unit is configured for providing an estimated value of a first system property based on the presence sensor data, obtaining a target value of the first system property, and for varying an operating parameter of the occupancy detection system in response to determining that the estimated value of first system property is not close in proximity to the target value of the first system property. The occupancy detection system generally has the same advantages as describe above for the method of controlling an occupancy detection system.

According to an embodiment of the occupancy detection system, the target value of the first system property is based on target parameters of the presence controlled system, or obtained as external data. The external data may be received from a user interface or an external database.

Further, there is provided a control system for a presence controlled system, the control system comprising: at least one occupancy detection system according to the invention. The presence controlled system is controlled based on a predetermined ratio between the comfort level and the energy consumption level of the presence controlled system. This advantageously provides a presence controlled system which meets the increasing need for energy saving and increased need to objectively measure and quantify the comfort level delivered to the user in order to make sure that the right balance between the two is obtained.

According to an embodiment, the control system comprises a user interface comprising a display for monitoring the target value of the first system property, and at least one second system property of the system, and an input receiver. The input receiver is arranged to receive a user input of external data, the external data being a user selected target value of a system property.

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

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings in which:

Fig. 1 is a schematic view of a room comprising an embodiment of an occupancy detection system according to the present invention;

Fig. 2 is a schematic illustration of an embodiment of an occupancy detection system according to the present invention;

Fig. 3 is a schematic flow-chart illustrating an embodiment of a method of controlling a presence controlled system according to the present invention;

Fig. 4 is a schematic illustration of a user interface in an embodiment of a control system for a presence controlled system according to the present invention; and Figs. 5 - 8 are schematic flow-charts illustrating embodiments of a method of controlling an occupancy detection system according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings. The below embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

The current inventive concept is applicable for any presence controlled system of a room or building, e.g. lighting systems, or heating ventilation and air condition systems (HVAC). For sake of simplicity only a lighting system will be described in the detailed description. Throughout this document the term 'close proximity' means the value in some probable range Δ =+- X %, where X is selected for the specific application.

Fig. 1 is a schematic illustration of an area, such as a room 50, in which an occupancy detection system 10 according to the present invention is installed. The occupancy detection system 10 comprises a presence detector 1 having a presence sensor 2 for providing a signal corresponding to movements of an occupant P of the room. In a typical setting, when the occupant P moves, the movement sensor 2 registers the movement and provides a signal upon which signal, in combination with an operating parameter δ here being a delay D of the occupancy detection system, an occupancy state of the room is determined. The delay D is here a definite time period after a last detected movement, after which the occupancy state of the room is determined to be 'empty' . The operating parameter δ may in embodiments of the invention refer to some other parameter, e.g. some other delay setting which is associated with determining the occupancy state of the room, or a sampling frequency of the occupancy detection system.

The presence detector 1 is here arranged on a wall of the room 50. Further, a user interface/control panel 14 (optional) of the occupancy detection system 10 is arranged on the wall of the room 50, such that a user can alter the settings of the occupancy detection system 10.

In this exemplifying embodiment, the occupancy detection system 10 is arranged in communication with a presence controlled lighting system 20. The presence controlled lighting system 20 comprises a control unit (not shown) arranged for controlling at least light sources of the room, here a luminaire 21, based on the occupancy state provided by the occupancy detection system 10. In a simple example, when the occupancy state is set to 'empty' the luminaire 21 should be turned off, and when the occupancy state is set to Occupied' the luminaire 21 should be turned on. Other types of operations of the light sources which is controlled by the presence controlled lighting system may include adapting the light intensity or color temperature, altering (the number) of active light sources etc.

The movement sensor 2 is here a pyro-electric infrared (PIR) sensor, but other movements sensors based on like for instance radio direction and ranging (RADAR), sound navigation and ranging (SONAR) etc. are applicable in the present inventive concept.

Multiple movement sensors may be included in the occupancy detection system, but this is not required.

Referring now to Fig. 2, which is a schematic illustration of an embodiment of the occupancy detection system according to the present invention, the occupancy detection system 10 comprises the presence sensor 2 for providing presence sensor data d_pres, a control unit 3 which is arranged to receive presence sensor data d_pres originating from the presence sensor 1, either directly from the presence sensor 2 or from a storage unit 5 in which presence sensor data is registered over time. The control unit 3 is further configured for estimating a first system property P_est, in this example an estimated energy consumption level E_est, of the lighting system 20 based on the presence sensor data d_pres. The first system property P may be selected to be the comfort level, the energy consumption, or a desired balance between the comfort level and the energy consumption. Further, a corresponding target value of the first system property P_set, i.e. here the target energy consumption of the lighting system, is obtained. The target value of the first system property P_set may be based on other target parameters of the presence controlled system, e.g. a current setting of a desired comfort level Cse_t- Alternatively, the target value of the first system property P_set is obtained as external data Xi received from a data base or by a user feeding in a desired value in via the control panel 14. Other target parameters of the presence controlled system may refer to specific requirements as defined in guide lines- or regulations, e.g. requirements on a maximum energy consumption per office/building, energy consumption/m², or energy consumption /lamp. The control unit 3 is configured for comparing the estimated value of the first system property and the target value of the first system property, here the estimated energy consumption level E_est and the target energy consumption level E_set, and to vary an operating parameter δ, e.g. the delay parameter D, of the occupancy detection system 10 in response to determining that the estimated value of the first system property P_est is not close in proximity to the target value of the first system property P_set- Since the current delay parameter D is known in the occupancy detector system, and the delay parameter D in turn influences the control of the lights of the lighting system, the operation state of the lighting and the energy consumption of the lighting can be deduced based on the presence sensor data d_pres and the delay parameter D, without any actual need to directly monitor the light status and the energy consumption. This is done by tracking if after a last detected movement the required delay has passed. As soon as the delay has passed the lighting system will turn off the lights, and the energy consumption will stop (or return to a minimum level). As soon as motion is detected again the lighting system will turn the lights back on, thereby increasing the energy consumption to a high level again. According to an embodiment of the method, the energy consumption for different values of the delay parameter D is performed by applying the same strategy as described above.

As used herein, a comfort level of a presence controlled lighting system is determined deriving the likelihood L of turning the lights off when there are still people in the office, as this reduces the comfort level. In order to determine this likelihood L several methods are possible.

According to an embodiment of the method, the likelihood L is estimated to be equal to 1 if a movement is detected within a time T from the moment the lights (would) turn off, and 0 otherwise. Parameter T typically is a small interval, e.g. 1 minute.

According to an embodiment of the invention, the estimated comfort level C_est is determined statistically by identifying occurrences where the user reacts to light switching off, i.e. the state of the lighting system, while the user is still in the area/office, i.e. the state of the occupancy detection system.

In an embodiment of the method, in a sampling based system (i.e. a presence status is determined every x (milli)seconds), one can use the estimated probability that the sensor does not record movement when there is a person in the room, which is denoted by a parameter p. Furthermore, let N be the number of consecutive presence samples indicating no presence. Then given value p, the likelihood L of a wrong decision is estimated as:

L = P^N/(1-P)^N (1) In case of a wrong decision, this will lead to turning off the lights N*(sampling

interval)/delay times. Hence the discomfort Q can be estimated by:

Q = N*(sampling interval)/(delay) * (p^N/(l-p ) (2) Further, in case of continuous, time- stamped presence data, the likelihood L of turning the lights off when there are still people in the office can be estimated using the expected time of not detecting presence when there is a person in the room, which is denoted by q. Assuming now that this time is exponentially distributed with mean q, and M is the length of the interval for which no presence has been detected, then the likelihood of a wrong decision can be estimated as:

L = e^"qM (3) In case of a wrong decision, this will lead to turning off the lights M/delay times. Hence the discomfort Q can be estimated by:

Q = M/(delay) * e^"qM (4) Alternative methods can be used to estimate the expected likelihood of wrongly turning off the lights. Once this likelihood has been estimated, the discomfort level can then be determined by summing all likelihood values (i.e. counting all expected times the lights are expected to be turned off wrongly). Discomfort can then be inversed and scaled to arrive at a comfort level.

Note that the energy consumption estimation E_est for different values of the delay parameter D can also be done using the likelihood L of wrongly turning off the lights. If the lights are wrongly turned off, the energy consumption is expected to continue after a small interruption at the same level. If the decision was correct, the energy consumption drops to zero.

Fig. 3 is a schematic flow-chart illustrating an embodiment of a control system

300 for a presence controlled system. The control system 300 comprises an occupancy detection system 100, which provides current setting of its delay parameters 170 and presence data 120 to two parallel steps of estimations: an estimation of the energy

consumption 130 and a comfort level estimation 140. The results of the estimations, i.e. the estimated energy consumption E_est and the estimated comfort level C_est, are provided to a balancing system 150 which is arranged to control the presence controlled system based on a predetermined ratio between the comfort level and the energy consumption level. A continuous monitoring of the estimated comfort level as well as the estimated energy consumption of the presence controlled lighting system is thus performed, such that the control of the lighting system is based on a predetermined balance between the estimated comfort and energy consumption. The values from the estimations 130 and 140 are optionally presented via a user interface, like for instance a dashboard 160, which is shown in more detail in Fig. 4. The dashboard 160 comprises a display 161 and a user input receiver, e.g. buttons or active areas of the display 161 for input of external data, like for instance selection of a desired target energy consumption level in the presence controlled system, or a desired balance between the energy consumption and the comfort level.

Exemplifying embodiments of a method of controlling an occupancy detection system is described in more detail herein under.

Referring now to Fig. 5, which is a flow chart illustrating an embodiment of the method of controlling an occupancy detection system according to the present invention, initially a desired target system property value, here a desired target comfort level C_set of the presence controlled system is obtained, step 101, and operating parameters δ of the occupancy detection system, here current delay values D, are received from the occupancy detection system or a data base, step 102. The delay values are current delay settings D(t) for a number of time instances, e.g. one delay value for each 5 minutes in a day, or one delay value for each 15 minutes of a working day and another set for weekend days. A current value Cest(D) of the comfort level of the presence controlled system is then estimated based on the current delay settings D and presence data, as previously described, for the selected time instances, step 103. The target comfort level C_set and the current comfort level C_est are compared, step 104. If the current comfort level is too low, the delay values should be increased and if the current comfort level C_est is too high, the delay values should be decreased. The change of the delay values may be done stepwise as illustrated in this example. A step size S is selected based on the comparison above, step 105a or step 105b, and a time instance (or set of time instances) is selected, step 106, for which time instance the delay value D(t) is decreased/increased by a step S: D(t) = D(t) + S, step 107. The selection of one or more time instances t for the altering of the operating parameters δ of the occupancy detection system may be based on the estimated and/or target comfort level, a current value of an occupancy detection system operating parameter δ, i.e. here on a current delay value D, or on a typical occupancy level at a specific time instance. However, the one or more time instances may alternatively be selected randomly.

To continue, a new value for the current comfort level value C_est is then estimated based on the new delay values D, step 108, and is compared with the desired target comfort level C_set , step 109. If it is determined that the new current comfort level C_est is not in the close proximity of the target comfort level C_set, the process of altering the delay value D is repeated, step 106. If the new current comfort level C_est is in close proximity of the target comfort level, |C_est -C_3et| < Δ, where Δ is a small value, e.g. 1%, the new delay value settings achieves the target comfort level value C_set and is used in the presence detector system, step 1 10.

In Fig. 6, a flow chart illustrating an embodiment of the method of controlling an occupancy detection system according to the present invention. The method described with reference to Fig. 5 is here utilized to alter delay value settings D(t) based on a target energy consumption E_set of the presence controlled system obtained in step 201, received operating parameters δ of the occupancy detection system, here current delay values D(t), step 202, and an estimated current value E_est(D) of the energy consumption of the presence controlled system based on the current delay settings D, step 203. The desired target energy consumption E_set and the current energy consumption E_est are compared, step 204, and if the current energy consumption is too low, the delay values should be increased and if the current energy consumption E_est is too high, the delay values should be decreased. The change of the delay values may be done stepwise as illustrated in this example. A step size s is selected based on the comparison above, step 205a or step 205b, and a time instance (or set of time instances) is selected, step 206, for which time instance the delay value D(t) is decreased/increased by a step S, D(t) = D(t) + s, step 207. A new value for the current energy consumption value E_est is then estimated based on the new delay values D, step 208, and is compared with the desired target energy consumption E_set, step 209. If it is determined that the new current energy consumption E_est is not in the close proximity of the target energy consumption E_set, the process of altering the delay value D is repeated for a selected time instance, step 206. If the new current energy consumption E_est is in close proximity of the target energy consumption, |E_est -E_set| < Δ, where Δ a small value, e.g. 1%, the new delay value settings achieves the target energy consumption value E_set and is used in the presence detector system, step 210.

Referring now to Fig. 8, this is a flowchart illustrating an embodiment of the method of controlling an occupancy detection system and/or a presence controlled system according to the present invention. Here the system property P of the presence controlled system is selected to be the balance B(E,C) between the energy consumption E and the comfort level C. See also the corresponding system described with reference to Figs. 3 and 4. A similar method as described for instance with reference to Fig. 5 is utilized to alter delay value settings D(t) of the occupancy detection system based on the desired balance B_set. Because increasing the delay of the presence controlled system causes increase in both the energy consumption and the comfort level. Thus, it is not clear if an increase in delay increases or decreases the balance criterion. Therefore, initially, current delay values D of the occupancy detection system is received, step 301, and utilized to estimate the current energy consumption level E_est and the current comfort level C_est of the presence controlled system.

In Fig. 8, a target balance B_set between the energy consumption of the presence controlled system and the comfort level of the system is obtained, step 401. Operating parameters δ of the occupancy detection system, here current delay values D(t), step 402 are received, and an estimated current value B_est of the balance of the presence controlled system is provided based on the current delay settings D, step 203. A stepwise altering of the delay values is now performed for both an increase of the delay values D(t), steps 415-416, and a decrease of the delay values D(t), steps 405 - 406. For both branches of altering of the delay values, a time instance t (or set of time instances) is selected, step 404, for which time instance the delay value D(t) is decreased/increased by a step S: D(t) = D(t) + s, steps 416, 406. New values for the current energy consumption value Bl_est, and B2_est are then estimated based on the new delay values Dl, and D2, respectively, steps 417 and 407, respectively, and are subsequently compared with the desired target balance B_set, steps 418 and 408, respectively. If it is determined that at least one of the new current balances, Bl_est and B2_est, is not in the close proximity of the target balance B_set, the process of altering the delay value D is repeated for a selected time instance, step 404, and so on, until at steps 418 and 408, if the estimated balance B_est is in close proximity of the target energy consumption, |B_est -B_set| < Δ, where Δ is small, e.g. 1%, for either one of Dl and D2 or for both, the new delay value settings D that achieves the target energy consumption value B_set is used in the presence detector step 451 or 443. The selection of the best suited delay values is based on which delay value first or alternatively best matches the desired balance B_set.

The flowchart in Fig. 7, illustrates how delay values are received and used to determine the new estimates (for E,C, or B), step 301 to 303, in the embodiments illustrated with reference to Figs. 5,6, and 8.

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 an embodiment, for example, there is a computer-implemented method for use in a HVAC control system or a building management system, said method comprising: receiving presence sensor data; estimating, from the presence sensor data, a comfort level corresponding to one or more current settings of the system; obtaining a value indicative of system energy consumption corresponding to said one or more current settings of the system; and varying at least one of said one or more current settings of the system so as to achieve a predefined balance between system energy consumption and estimated comfort level.

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

Claims

CLAIMS:

1. A method of controlling an occupancy detection system (100), the occupancy detection system being suitable for a presence controlled system (200), said method comprising:

receiving presence sensor data d_pres;

- for a first system property P of said presence controlled system:

providing an estimated value P_est of said first system property P based on said presence sensor data d_pre_S;

obtaining a target value P_set of said first system property P; and varying an operating parameter δ of said occupancy detection system in response to determining that said estimated value P_est is not in close proximity to said target value P_set-

2. A method according to claim 1, wherein said first system property P is a comfort level, energy consumption, or a desired balance between the comfort level and the energy consumption.

3. A method according to claim 1 or 2, wherein said target level P_set is derived based on at least a target level of a second system property of the presence controlled system, or is obtained as external data.

4. A method according to claim 2, when said first system property P is energy consumption, wherein said target level P_set is based on a target level of the comfort level of the presence controlled system.

5. A method according to any preceding claim, wherein said operating parameter δ is a delay parameter D for setting a occupancy state of the occupancy detection system to 'empty' after a last presence event is detected.

6. A method according to any preceding claim, wherein said presence sensor data d comprises a set of presence data collected during a predetermined time period T, from which a presence pattern is derived, and wherein said estimated first system property P_est is based on said presence pattern.

7. A method according to claim 6, wherein said presence pattern is derived with respect to a number of time instances t= ti,t₂, ..tN, and wherein said step of varying said operating parameter δ of the occupancy detection system comprises determining a set of operating parameters δ( ti,t₂, ..tN ) of said occupancy detection system corresponding to a preselected set of said time instances t.

8. A method according to claim 3, wherein said external data is received from a user interface or an external database.

9. A method according to any preceding claim, wherein said step of providing said estimated value of the first system property P_est is based on determining a likelihood of the occupancy detection system wrongly setting said occupancy state to 'empty' after a last presence event is detected.

10. A method according to any preceding claim, wherein said target value of the first system property is estimated based on said presence sensor data and said operating parameter δ.

11. An occupancy detection system suitable for a presence controlled system, and comprising:

a presence sensor for providing presence sensor data;

a control unit arranged for receiving presence sensor data d_pres; wherein said control unit is configured for

for a first system property P:

obtaining a target value P_set of said first property P; and for

varying an operating parameter δ of the occupancy detection system in response to determining that the estimated value P_est is not close in proximity to the target value

Pset

12. A system according to claim 11, wherein said target value P_set of the first system property is based on target parameters of the presence controlled system, or obtained as external data.

13. A system according to claim 12, wherein said external data is received from a user interface or an external database.

14. A control system for a presence controlled system, said control system comprising:

at least one occupancy detection system according to claim 11, 12 or 13, wherein said presence controlled system is controlled based on a predetermined ratio between said target value P_set of said first system property and said energy consumption level of said presence controlled system.

15. A control system according to claim 14, further comprising:

a user interface comprising

a display for monitoring said target value P_set of said first system property, and at least one second system property of said system; and

an input receiver, wherein

said input receiver is arranged to receive a user input of external data, said external data being a user selected target value of a system property.