WO2021043651A1

WO2021043651A1 - Calibrating a people counter

Info

Publication number: WO2021043651A1
Application number: PCT/EP2020/073898
Authority: WO
Inventors: Tomas Jonsson
Original assignee: Assa Abloy Ab
Priority date: 2019-09-02
Filing date: 2020-08-26
Publication date: 2021-03-11
Also published as: SE1950998A1

Abstract

It is provided a method for calibrating a people counter configured to count people in a physical space. The method is performed in a calibrator and comprises the steps of: obtaining a CO₂ measurement for the physical space from a CO₂ sensor; and calibrating the people counter based on the CO₂ measurement.

Description

CALIBRATING A PEOPLE COUNTER

TECHNICAL FIELD

[0001] The present disclosure relates to the field of calibrating and in particular to calibrating a people counter.

BACKGROUND

[0002] Ventilation in buildings is of great importance for well-being and health of its occupants. Controlled ventilation, where outgoing and/or incoming ventilation is dynamically controlled is known for decades. Such ventilation can be controlled by a ventilation controller.

[0003] However, when determining how much ventilation a physical space needs, there is a careful balance. On the one hand, ventilation is needed to keep the air fresh for people in the physical space. On the other hand, ventilation should not be excessive as this generates cost by running fans and sometimes increasing costs for heating or cooling since temperature-controlled air in the physical space needs to be replaced.

SUMMARY

[0004] One objective is to calibrate a people counter based on carbon dioxide (C0₂) measurements.

[0005] According to a first aspect, it is provided a method for calibrating a people counter configured to count people in a physical space. The method is performed in a calibrator and comprises the steps of: obtaining a C0₂ measurement for the physical space from a C0₂ sensor; and calibrating the people counter based on the C0₂ measurement.

[0006] The step of calibrating may comprise determining, based on the C0₂ measurement, that no person is in the physical space, and setting the people counter to no person. [0007] The step of calibrating may further comprise determining that no person is in the physical space only under the condition that ventilation for the physical space is in a low ventilation state.

[0008] The method may further comprise the step of: providing people count values for ventilation control purposes.

[0009] In the step of calibrating the people counter, the people counter can be provided by a doorway to detect when people enter or exit the physical space.

[0010] According to a second aspect, it is provided a calibrator for calibrating a people counter configured to count people in a physical space. The calibrator comprises: a processor; and a memory storing instructions that, when executed by the processor, cause the calibrator to: obtain a C0₂ measurement for the physical space from a C0₂ sensor; and calibrate the people counter based on the C0₂ measurement.

[0011] The instructions to calibrate may comprise instructions that, when executed by the processor, cause the calibrator to determine, based on the C0₂ measurement, that no person is in the physical space, and set the people counter to no person.

[0012] The instructions to calibrate may further comprise instructions that, when executed by the processor, cause the calibrator to determine that no person is in the physical space only under the condition that ventilation for the physical space is in a low ventilation state.

[0013] The calibrator may further comprise instructions that, when executed by the processor, cause the calibrator to: provide people count values for ventilation control purposes.

[0014] The calibrator may be configured to calibrate the people counter provided by a doorway to detect when people enter or exit the physical space.

[0015] According to a third aspect, it is provided a system comprising the calibrator according to any one of claims 6 to 10 and a people counter configured to be calibrated by the calibrator. [0016] According to a fourth aspect, it is provided a computer program for calibrating a people counter configured to count people in a physical space. The computer program comprises computer program code which, when run on a calibrator causes the calibrator to: obtain a C0₂ measurement for the physical space from a C0₂ sensor; and calibrate the people counter based on the C0₂ measurement.

[0017] According to a fifth aspect, it is provided a computer program product comprising a computer program according to the fourth aspect and a computer readable means on which the computer program is stored.

[0018] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Aspects and embodiments are now described, by way of example, with refer ence to the accompanying drawings, in which:

[0020] Fig 1 is a schematic drawing illustrating an environment in which embodiments presented herein can be applied;

[0021] Figs 2A-D are schematic diagrams illustrating embodiments of where the calibrator can be implemented;

[0022] Fig 3 is a flow chart illustrating embodiments of methods for calibrating a people counter configured to count people in a physical space;

[0023] Fig 4 is a schematic diagram illustrating components of the calibrator of Figs 2A-D; and [0024] Fig 5 shows one example of a computer program product comprising computer readable means.

DETAILED DESCRIPTION

[0025] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0026] Fig 1 is a schematic diagram illustrating an environment in which embodiments presented herein can be applied. It is shown a physical space 5 in which there is ventilation. The physical space 5 is illustrated as a room, but the physical space can be larger (e.g. a building or a set of rooms in a building) or smaller (e.g. section of a room), as long as ventilation is at least partly controllable for the physical space 5.

[0027] In this example, there is controlled outgoing ventilation 4a and controlled incoming ventilation 4b. The ventilation can also be implemented using only one of the controlled outgoing ventilation 4a and controlled incoming ventilation 4B, in which case the other ventilation direction is implemented using passive air flow. A ventilation controller 11 controls the amount of ventilation by controlling outgoing ventilation 4a and/or incoming ventilation 4b. The amount of ventilation can be measured in terms of the amount of air that is passed per unit of time, e.g. m3 per hour.

[0028] When determining how much ventilation the physical space 5 needs, there is a careful balance. On the one hand, ventilation is needed to keep the air fresh for people in the physical space 5. On the other hand, ventilation should not be excessive as this generates cost by running fans and sometimes increasing costs for heating or cooling since temperature-controlled air in the physical space needs to be replaced. While the cost for replacement air can be reduced by using heat exchangers, the cost is not eliminated. [0029] Hence, there is a clear balance to be struck between air quality and cost for ventilation. Moreover, ventilation need is dependent on the number of people in the physical space. More people in the physical space decreases air quality by increasing CO₂ levels and raising air temperature. In the example of Fig 1, there is a first person 6a and a second person 6b in the physical space 5.

[0030] In order to monitor the air quality in the physical space 5, a C0₂ sensor 2 can be used. When people enter the physical space 5, the C0₂ measurements captured by the CO₂ sensor 2 will rise. This can be used by the ventilation controller 11 to increase ventilation to keep air quality high. When people leave, the CO ₂ measurements captured by the C0₂ sensor 2 will decrease. When the C0₂ level falls low enough, this can be used by the ventilation controller to decrease ventilation to keep operational costs for ventilation low.

[0031] In embodiments presented herein, a people counter 1 is also (or instead of the CO₂ sensor) used as an indicator of air quality. The people counter can determine the number of persons present in the physical space 5. The people counter 1 can be based on radar, image analysis from a camera image (infrared and/or visible light), lidar, etc. or any combination of these. The people counter 1 can be provided by a doorway 3 (e.g. above the doorway 3), where people enter and exit the physical space 5. If there are multiple doorways, corresponding co-operating people counters can be provided at each doorway, to thereby always be able to determine the number of persons in the physical space 5. For instance, the people counter 1 can be provided in a door opener/door closer or attached to the surrounding structure (e.g. wall). By providing the people counter 1 by the doorway, the people counter 1 can detect when people enter or exit the physical space.

[0032] The number of persons in the physical space 5 is provided to the ventilation controller 11. Compared to C0₂ based ventilation control, the people counter based ventilation control can react quicker. This is due to a person entering the physical space 5 is detected at that time, while it will take some time until the entry of the person affects the C0₂ level in the physical space. [0033] There is a risk that the people counter 1 can give an incorrect counter of people. For instance, if several persons enter the physical space 5 at the same time, the people counter could make a mistake, e.g. counting the number of persons to be three when four people enter in close proximity to each other. The people counter 1 can be used for other purposes, e.g. for knowing how many people are in a building in case of a fire. In this case, it is of great importance that the people counter 1 does not give incorrect values. Alternatively or additionally, the people counter 1 can be used to determine utilisation of the physical space 5, e.g. applied for when the physical space forms part of an office or other commercial property.

[0034] Hence, according to embodiments presented herein, the C0₂ sensor 2 is used to calibrate the people counter. This calibration is performed in a calibrator 10.

Together, the calibrator 10 and the people counter 1 can make up a system 7. The system 7 can comprise separate physical devices for the calibrator 10 and the people counter 1. Alternatively, the calibrator 10 and the people counter are provided in a single physical device.

[0035] Figs 2A-D are schematic diagrams illustrating embodiments of where the calibrator 10 can be implemented.

[0036] In Fig 2 A, the calibrator 10 is shown as implemented in the CO₂ sensor 2. The

CO₂ sensor is thus the host device for the calibrator 10 in this implementation.

[0037] In Fig 2B, the calibrator 10 is shown as implemented in the people counter 1. The people counter 1 is thus the host device for the calibrator 10 in this implementation.

[0038] In Fig 2C, the calibrator 10 is shown as implemented in the ventilation controller 11. The ventilation controller 11 is thus the host device for the calibrator 10 in this implementation.

[0039] In Fig 2D, the calibrator 10 is shown as implemented as a stand-alone device. The calibrator 10 thus does not have a host device in this implementation. [0040] Fig 3 is a flow chart illustrating embodiments of methods for calibrating a people counter configured to count people in a physical space. The method is performed in a calibrator.

[0041] In an obtain C0₂ measurement step 40, the calibrator obtains a C0₂ measurement for the physical space from a C0₂ sensor.

[0042] In a calibrate people counter step 42, the calibrator calibrates the people counter based on the C0₂ measurement.

[0043] The people counter can be provided by a doorway to detect when people enter or exit the physical space. When people enter and exit the physical space, there is a risk that the people counter counts people erroneously, counting an extra person entering or exiting or missing counting a person entering or exiting, e.g. when several people enter or exit at once.

[0044] The calibrating can comprise determining, based on the C0₂ measurement, that no person is in the physical space, and setting the people counter to no person. This can be determined when the CO2 measurement is within a range which has been pre configured to indicate a state where there is no person in the physical space. The case of no person in the physical space can be determined with great certainty, since, at least after some time of ventilation, the C0₂ measurement approaches a baseline atmospheric CO2 level. The baseline atmospheric C0₂ level can be preconfigured for a particular installation or the baseline atmospheric C0₂ level can be the same for any installation. There can be other ranges of C0₂ measurements which each corresponds to a particular number of persons in the physical space.

[0045] In one embodiment, the calibrator determines that no person is in the physical space only under the condition that ventilation for the physical space is in a low ventilation state. The low ventilation is a state which is used when there are no people in the physical space. In one embodiment, the low ventilation state implies no ventilation at all. By requiring that a low ventilation state is needed to determine no person is in the physical space, a situation is avoided where there are people in the physical space, but the resulting C0₂ is ventilated out. When the calibrator has determined the number of persons (e.g. zero according to the above) in the physical space, the people counter is set to that number of persons, thereby calibrating the people counter.

[0046] In an optional provide people count value step 44, the calibrator provides count values for ventilation control purposes. When the calibrator is implemented in the ventilation controller, this step can also comprise controlling ventilation for the physical space based on the people count value.

[0047] This method can be repeated often, and it is often the case that at least part of each day results in the physical space being empty of people. In this way, the people counter can be automatically calibrated once or several times per day, which greatly reduces the risk of any people counter mistakes resulting in long term erroneous people count values. This is of great value also, e.g. when the people counter is used to know the number of people in a physical space in case of a fire or other emergency.

[0048] Fig 4 is a schematic diagram illustrating components of the calibrator 10 of Figs 2A-D. It is to be noted that one or more of the mentioned components can be shared with the host device, when applicable. A processor 60 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions 67 stored in a memory 64, which can thus be a computer program product. The processor 60 could alternatively be implemented using an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The processor 60 can be configured to execute the method described with reference to Fig 3 above.

[0049] The memory 64 can be any combination of random-access memory (RAM) and/or read-only memory (ROM). The memory 64 also comprises persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid-state memory or even remotely mounted memory.

[0050] A data memory 66 is also provided for reading and/ or storing data during execution of software instructions in the processor 60. The data memory 66 can be any combination of RAM and/or ROM. [0051] The calibrator 10 further comprises an I/O interface 62 for communicating with external and/or internal entities. Optionally, the I/O interface 62 also includes a user interface.

[0052] Other components of the calibrator 10 are omitted in order not to obscure the concepts presented herein.

[0053] Fig 5 shows one example of a computer program product 90 comprising computer readable means. On this computer readable means, a computer program 91 can be stored, which computer program can cause a processor to execute a method according to embodiments described herein. In this example, the computer program product is an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. As explained above, the computer program product could also be embodied in a memory of a device, such as the computer program product 64 of Fig 4. While the computer program 91 is here schematically shown as a track on the depicted optical disk, the computer program can be stored in any way which is suitable for the computer program product, such as a removable solid-state memory, e.g. a Universal Serial Bus (USB) drive.

[0054] The aspects of the present disclosure have mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

1. A method for calibrating a people counter (l) configured to count people in a physical space (5), the method being performed in a calibrator (10) and comprising the steps of: obtaining (40) a carbon dioxide, C0₂, measurement for the physical space (5) from a CO sensor (2); and calibrating (42) the people counter (1) based on the C0₂ measurement.

2. The method according to claim 1, wherein the step of calibrating (42) comprises determining, based on the C0₂ measurement, that no person is in the physical space (5), and setting the people counter (1) to no person.

3. The method according to claim 2, wherein the step of calibrating (42) further comprises determining that no person is in the physical space (5) only under the condition that ventilation for the physical space (5) is in a low ventilation state.

4. The method according to any one of the preceding claims, further comprising the step of: providing (44) people count values for ventilation control purposes.

5. The method according to any one of the preceding claims, wherein in the step of calibrating (42) the people counter, the people counter (1) is provided by a doorway to detect when people enter or exit the physical space (5).

6. A calibrator (10) for calibrating a people counter (1) configured to count people in a physical space (5), the calibrator (10) comprising: a processor (60); and a memory (64) storing instructions (67) that, when executed by the processor, cause the calibrator to: obtain a carbon dioxide, C0₂, measurement for the physical space (5) from a C0₂ sensor (2); and calibrate the people counter (1) based on the C0₂ measurement.

7. The calibrator (10) according to claim 6, wherein the instructions to calibrate comprise instructions (67) that, when executed by the processor, cause the calibrator to determine, based on the C0₂ measurement, that no person is in the physical space (5), and set the people counter (1) to no person.

8. The calibrator (10) according to claim 7, wherein the instructions to calibrate further comprise instructions (67) that, when executed by the processor, cause the calibrator to determine that no person is in the physical space (5) only under the condition that ventilation for the physical space (5) is in a low ventilation state.

9. The calibrator (10) according to any one of claims 6 to 8, further comprising instructions (67) that, when executed by the processor, cause the calibrator to: provide people count values for ventilation control purposes.

10. The calibrator (10) according to any one of claims 6 to 9, wherein the calibrator is configured to calibrate the people counter (1) provided by a doorway to detect when people enter or exit the physical space (5).

11. A system (7) comprising the calibrator (10) according to any one of claims 6 to 10 and a people counter (1) configured to be calibrated by the calibrator (10).

12. A computer program (67, 91) for calibrating a people counter (1) configured to count people in a physical space (5), the computer program comprising computer program code which, when run on a calibrator (10) causes the calibrator (10) to: obtain a carbon dioxide, C0₂, measurement for the physical space (5) from a C0₂ sensor (2); and calibrate the people counter (1) based on the C0₂ measurement.

13. A computer program product (64, 90) comprising a computer program according to claim 12 and a computer readable means on which the computer program is stored.