EP4731860A1

EP4731860A1 - Determining a state of a door

Info

Publication number: EP4731860A1
Application number: EP24728937.4A
Authority: EP
Inventors: Annea BARKEFORS; Liam NERIC
Original assignee: Assa Abloy AB
Current assignee: Assa Abloy AB
Priority date: 2023-06-20
Filing date: 2024-05-21
Publication date: 2026-04-29
Also published as: WO2024260666A1; SE2350751A1; SE547422C2

Abstract

It is provided a method for determining a state of a door (15). The method is performed in a status determiner (1) based on accelerometer data of an accelerometer (18) that is fixed to the door (15). The method comprises: determining (40) that the door has transitioned from an open state (20) to a closing (21) state, based on a magnitude of a velocity of the door (15) in a first direction being greater than a closing velocity threshold (30); and determining (42) that the door has transitioned from a closing state (21) to an opening (23) state, based on a magnitude of a velocity of the door (15) in a second direction being greater than an opening velocity threshold (32), wherein the second direction is opposite from the first direction, wherein the opening velocity threshold (32) is based on an indication of position (29) of the door (15).

Description

DETERMINING A STATE OF A DOOR

TECHNICAL FIELD

[0001] The present disclosure relates to the field of determining a state of a door, and in particular to determining such a state based on accelerometer data of an accelerometer that is fixed to the door.

BACKGROUND

[0002] In door systems, accelerometer data from an accelerometer fixed to the door can be used to determine door closing operations. Such a system can be used without any coupling to operational components (motors, control, etc.) of the door itself. The accelerometer data can be integrated to derive velocity.

[0003] The direction and magnitude of velocity can then be used to determine whether the door is in an open state, closing state, closed state, or opening state.

[0004] A problem occurs when a closing operation is aborted, e.g. by a person blocking the closing door, causing the door to open again. When the door closure is aborted, e.g. due to a person blocking, and the doors open again, the velocity for opening can vary depending on how far or close the door is to the open position. How can the change in the door from closing state to opening state occur reliably and robustly?

SUMMARY

[0005] One object is to improve reliability of determining when a door enters an opening state after a closing state, indicating that a closing operation of a door is aborted.

[0006] According to a first aspect, it is provided a method for determining a state of a door, the method being performed in a status determiner based on accelerometer data of an accelerometer that is fixed to the door. The method comprises: determining that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determining that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0007] The velocity may be determined by integrating an accelerometer signal of the accelerometer data.

[0008] The velocity may be determined using a low-pass filter.

[0009] The indication of position of the door may be determined by integrating the velocity.

[0010] The indication of position of the door may be determined based on a duration of the door being in the closing state.

[0011] The opening velocity threshold may be determined to be relatively low based on the indication of position indicating that the door is relatively near a fully open position.

[0012] When the indication of position indicates that the door is nearer the fully open position than a position threshold, the opening velocity threshold may be lower than when the indication of position indicates that the door is further away from the fully open position than the position threshold.

[0013] The door may be a sliding door.

[0014] The door may be a swing door.

[0015] According to a second aspect, it is provided a status determiner for determining a state of a door based on accelerometer data of an accelerometer that is fixed to the door. The status determiner comprises: processing circuitry; and a memory circuitry storing instructions that, when executed by the processing circuitry, cause the status determiner to: determine that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determine that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0016] According to a third aspect, it is provided a computer program for determining a state of a door based on accelerometer data of an accelerometer that is fixed to the door. The computer program comprises computer program code which, when executed on a status determiner causes the status determiner to: determine that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determine that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0017] According to a fourth aspect, it is provided a computer program product comprising a computer program according to the third aspect and a computer readable means comprising non-transitory memory in 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 reference to the accompanying drawings, in which: [0020] Fig 1 is a schematic diagram illustrating an environment in which embodiments presented herein can be applied;

[0021] Fig 2 is a state diagram illustrating states of the door of Fig 1;

[0022] Figs 3A-C are schematic graphs of velocity of the door of Fig 1 in a normal closing operation and an aborted closing operation;

[0023] Fig 4 is a schematic graph of position of the door of Fig 1 over time in the normal closing operation illustrated by Fig 3A;

[0024] Fig 5 is a flow chart illustrating embodiments of methods for determining a state of a door, such as the door of Fig 1;

[0025] Fig 6 is a schematic diagram illustrating components of the status determiner of Fig 1 according to one embodiment; and

[0026] Fig 7 shows one example of a computer program product comprising computer readable means.

DETAILED DESCRIPTION

[0027] 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.

[0028] Embodiments presented herein are concerned with determining a door velocity based on accelerometer data from an accelerometer that is fixed to the door. When a closing velocity exceeds a closing velocity threshold, the door is considered to be in a closing state. If the door closing is aborted and the door opens again, the door is considered to be in an opening state when the velocity in an opening direction is greater than an opening velocity threshold. However, the opening velocity threshold is dynamically determined and depends on an indicator of door position. Specifically, when the door has only closed a small distance, the opening velocity threshold is low, while when the door has opened significantly, the opening velocity threshold is high. In this way, the opening state of the door can more reliably be detected for doors that have only opened a small amount before the closing was blocked, in which case the opening velocity of the door is small. At the same time a robust determination of the opening state is achieved for situations when the door has opened more.

[0029] Fig 1 is a schematic diagram illustrating an environment in which embodiments presented herein can be applied. Access to a physical space 16 is controlled by a door 15, which is optionally selectively unlockable. The door 15 can be a sliding door, a swing door, a rolling door, etc. The door 15 stands between a first physical space 14 and a second physical space 16. The door 15 comprises one or more door leaves.

[0030] Optionally, in order to control access to the second physical space 16, an electronic lock 12 can be provided to selectively unlock the door 15. In this case, the electronic lock 12 is controllable to be in a locked state or in an unlocked state. The electronic lock 12 can evaluate access of a person e.g. by communicating with an electronic key of the person, using biometrics or personal identification number (PIN). Alternatively or additionally, access through the door 15 can be provided using a traditional, mechanical, lock.

[0031] The operation of opening and closing of the door can be under control of a door controller (not shown), that controls a motor for the door operations of opening and closing the door.

[0032] According to embodiments presented herein, it is provided an accelerometer 18 that is fixed to the door, e.g. using adhesives, one or more screws, nails, Velcro, etc. The accelerometer communicates accelerometer data with a status determiner 1. The status determiner 1 uses an accelerometer signal in the accelerometer data to determine velocity, direction and optionally position of the door 15. This determination is performed without the need for any coupling to operational components (motors, control, etc.) of the door itself. When there are multiple door leaves of the door 15, there can be one accelerometer fixed to each door leaf. Alternatively, when the door leaves move synchronously, the door leaves are considered to move in opposite but equal velocities, whereby it is sufficient to fix a single accelerometer 18 to one of the door leaves.

[0033] The status determiner 1 can be provided as a stand-alone device, or the status determiner 1 can be integrated with the electronic lock 12, when provided. The status determiner 1 can be provided at the same site as the door 15 and the accelerometer, or the status determiner 1 can be provided remotely. When the status determiner 1 is provided remotely, the status determiner 1 can receive accelerometer data from the accelerometer 18 directly or via intermediate components, e.g. via a wireless network, cellular network and/ or the Internet.

[0034] Fig 2 is a state diagram illustrating states of the door of Fig 1. The states are determined by the status determiner 1 based, at least partly, on accelerometer data of the accelerometer 18 that is fixed to the door 15.

[0035] In an open state 20, the door 15 is open, i.e. the door is considered to be in a fully open position. In a closed state 22, the door 15 is closed, i.e. the door is considered to be in a fully closed position. In a stationary partly closed state 24, the door is considered to be stationary in a partially closed state. In a closing state 21 the door 15 is closing, i.e. the door is in a moving state transitioning towards the closed state 22 but is not fully closed yet. In an opening state 23, the door is opening, i.e. the door is in a moving state transitioning towards the open state 20 but is not fully open yet.

[0036] The door 15 can transition from the open state 20 to the closing state, and further to the closed state 22. Analogously, the door 15 can transition from the closed state 22 to the opening state 23, and further to the open state 20. If the door 21 is in the closing state 21, the door 15 can transition, optionally via the stationary partly closed state 24, to the opening state 23, e.g. if there is an object or person blocking the closing door movement, at which point the door 15 should open again. If the door 15 is in the opening state 23, the door 15 can transition, optionally via the stationary partly closed state 24, to the closing state e.g. if a person commands the door 15 to close, e.g. by pushing a close button. [0037] The states 20-23 and transitions of Fig 2 will now be described with further reference to Figs 3A-C, that are schematic graphs of velocity of the door of Fig 1 in a normal closing operation and an aborted closing operation. The horizontal axis in Figs 3A-C represents time t and the vertical axis represents velocity v. The velocity 28 of the door 15 can be derived by integrating the accelerometer signal of the accelerometer data from the accelerometer 18. The accelerometer signal, and thus the velocity 28, can be quite noisy, in which a low-pass filter can be applied on the accelerometer signal/and or the derived velocity. In Figs 3A-C, a positive velocity indicates a first direction being a closing direction, and a negative velocity indicates a second direction being an opening direction.

[0038] Looking first to Fig 3A, it is illustrated a normal closing operation. At time o, the door 15 is in an open state 20 . The door 15 is triggered to close, e.g. based on user input or a timer of inactivity around the door. The velocity then increases (in the first, closing, direction) and when the velocity reaches a closing velocity threshold 30 at time ti, the status determiner 1 considers the closing velocity to be sufficiently stable to determine that the door 15 has transitioned to the closing state 21. When the door 15 approaches its closed position, the velocity 28 decreases, and at a time t₂, the velocity 28 falls below a closed threshold 33, at which point the status determiner 1 determines that the door 15 has transitioned to the closed state 22.

[0039] Looking now to Fig 3B, it is illustrated an aborted closing operation. The operation starts in the same way as for the scenario illustrated by Fig 3A. Specifically, the door is open at time o, and the status determiner 1 determines that the door 15 has transitioned to the closing state 21 when the velocity 28 of the door reaches the closing velocity threshold at time ti. Here, however, the closing operation is aborted, e.g. due to a blocking object, and the velocity quickly drops all the way to the other (opening) direction, which is illustrated as a negative velocity in Fig 3B. When the magnitude of the velocity 28 exceeds an opening velocity threshold 32 (in the opening direction), the status determiner 1 determines that the door 15 has transitioned to the opening state 23.

[0040] The speed of (re)opening depends on how much the door 15 has had time to close, i.e. the position of the door 15. When the door 15 has closed significantly, the opening velocity is relatively large to open the door 15 efficiently. On the other hand, when the door has only closed a slight amount, the opening occurs at a lower speed since the door is at the final stage of opening.

[0041] In the scenario of Fig 3B, the door has only closed slightly, and the status determiner 1 then sets the opening velocity threshold to a relatively low magnitude (in the opening direction).

[0042] In the scenario of Fig 3C, the door has closed more, and the status determiner 1 then sets the opening velocity to a relatively high magnitude (in the opening direction).

[0043] In the scenarios of both Figs 3B and Fig 3C, when the velocity 28 reaches the opening velocity threshold (in the opening direction) of the opening velocity threshold 32, the status determiner 1 determines that the door 15 has transitioned to the opening state.

[0044] Fig 4 is a schematic graph of position 29 of the door of Fig 1 over time in the normal closing operation illustrated by Fig 3A. The horizontal axis represents time t and the vertical axis represents position p of the door 15, where an increased position indicates that the door is more closed. Referring back to Figs 3B-C, one way to determine the opening velocity threshold 32 is to compare the position 29 of the door with a position threshold 25. When the position is less than the position threshold 25, the opening velocity threshold 32 is set to a relatively low magnitude (in the opening direction) to catch the case illustrated by Fig 3B. On the other hand, when the position is greater than the position threshold 25, the opening velocity threshold is set to a relatively high magnitude (in the opening direction) to be more robust, and still catch the case illustrated by Fig 3C.

[0045] The position threshold 25 corresponds to time t₄ which is a certain duration after the closing of the door started at time t₀. Hence, the duration can also be an indicator of position. As long as the start time t₀ is consistent across closing operations, the start time to can be any consistent start time, e.g. the start time can be determined as the time when the status determiner 1 determines that the door has transitioned from the open state to the closing state, i.e. time ti in Figs 3A-C. [0046] Fig 5 is a flow chart illustrating embodiments of methods for determining a state of a door, such as the door of Fig 1. The embodiments of the methods are performed in the status determiner 1 based on accelerometer data of an accelerometer 18 that is fixed to the door 15. As explained above, the door 15 can be a sliding door or a swing door, or any other suitable type of door.

[0047] In a determine closing state step 40, the status determiner 1 determines that the door has transitioned from an open state 20 to a closing 21 state, based on a magnitude of a velocity of the door 15 in a first (closing) direction being greater than a closing velocity threshold 30. This corresponds to time ti in Figs 3A-C.

[0048] In a determine opening state step 42, the status determiner 1 determines that the door has transitioned from a closing state 21 to an opening 23 state, based on a magnitude of a velocity of the door 15 in a second (opening) direction being greater than an opening velocity threshold 32. This corresponds to time t₃ in Figs 3B-C. The second direction is opposite from the first direction. According to embodiments presented herein, the opening velocity threshold 32 is based on an indication of position 25 of the door 15.

[0049] The velocity can be determined by integrating an accelerometer signal of the accelerometer data. Optionally, the velocity is determined using a low-pass filter (applied to the accelerometer signal and/or velocity), to reduce the effect of noise in the accelerometer signal.

[0050] The indication of position of the door can be determined by integrating the velocity. Since the velocity is based on the accelerometer data, also the indication of position is determined based on the accelerometer data, and thus does not require any additional measurements. While the indication of position derived in this way can be quite noisy due to the double integration, for the purposes presented herein, the indication of position has proven to be usable and valuable for the purposes presented herein. [0051] Alternatively, the indication of position of the door is determined based on a duration of the door being in the closing state. Also this indication of position does not require any additional measurements.

[0052] The opening velocity threshold 32 can be determined to be relatively low based on the indication of position 25 indicating that the door 15 is relatively near a fully open position. For instance, when the indication of position 25 indicates that the door 15 is nearer the fully open position than a position threshold 25 (corresponding to the scenario illustrated by Fig 3B), the opening velocity threshold 32 is lower than when the indication of position 29 indicates that the door 15 is further away from the fully open position than the position threshold 25 (corresponding to the scenario illustrated by Fig 3B).

[0053] It is to be noted that Fig 5 focuses on a particular part of tasks the status determiner 1 corresponding to the scenarios illustrated in Figs 3B-C and described above. The status determiner, more generally, can be used to determine direction of movement of the door, and to determine with confidence (above a threshold) that the door is fully closed or fully open.

[0054] Embodiments presented herein provide more robust determination of the transition of the door from a closing state to an opening state. Not only is the situation with only a slightly closed door determined reliably, but also the case with a door that is significantly more closed is more robust in addressing potential noisy measurements from the accelerometer.

[0055] Hence, the risk of missing the state change of the door from closing to opening is significantly reduced. This can have great impact, e.g. for monitoring buildings and/ or collecting statistics on door operations for climate control, etc. Furthermore the cancelled door closing can cause greater stress on mechanical components of the door, whereby knowledge of such events can be used for appropriate scheduling of maintenance.

[0056] Fig 6 is a schematic diagram illustrating components of the status determiner

1 of Fig 1. Processing circuitry 60 is provided using any combination of one or more of a suitable central processing unit (CPU), graphics processing unit (GPU), multiprocessor, neural processing unit (NPU), microcontroller, digital signal processor (DSP), etc., capable of executing software instructions 67 stored in memory circuitry 64, which can thus be a computer program product. The processing circuitry 60 could alternatively be implemented using an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The processing circuitry 60 can be configured to execute the method described with reference to Fig 5 above.

[0057] The memory circuitry 64 can be any combination of random-access memory (RAM) and/or read-only memory (ROM). The memory circuitry 64 also comprises non- transitory 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.

[0058] A data memory 66 is also provided for reading and/ or storing data during execution of software instructions in the processing circuitry 60. The data memory 66 can be any combination of RAM and/or ROM.

[0059] The status determiner 1 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.

[0060] Other components of the status determiner 1 are omitted in order not to obscure the concepts presented herein.

[0061] Fig 7 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 in a non-transitory memory. The computer program can cause processing circuitry to execute a method according to embodiments described herein. In this example, the computer program product 90 is in the form of a removable solid-state memory, e.g. a Universal Serial Bus (USB) drive. 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 6. While the computer program 91 is here schematically shown as a section of the removable solid-state memory, the computer program can be stored in any way which is suitable for the computer program product, such as another type of removable solid-state memory, or an optical disc, such as a CD (compact disc), a DVD (digital versatile disc) or a Blu-Ray disc.

[0062] Here now follows a list of enumerated embodiments from another perspective.

[0063] 1. A method for determining a state of a door, the method being performed in a status determiner based on accelerometer data of an accelerometer that is fixed to the door, the method comprising: determining that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determining that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0064] 2. The method according to embodiment 1, wherein the velocity is determined by integrating an accelerometer signal of the accelerometer data.

[0065] 3. The method according to embodiment 2, wherein the velocity is determined using a low-pass filter.

[0066] 4. The method according to embodiment 2 or 3, wherein the indication of position of the door is determined by integrating the velocity.

[0067] 5. The method according to any one of embodiments 1 to 3, wherein the indication of position of the door is determined based on a duration of the door being in the closing state.

[0068] 6. The method according to any one of the preceding embodiments, wherein the opening velocity threshold is determined to be relatively low based on the indication of position indicating that the door is relatively near a fully open position. [0069] 7- The method according to embodiment 6, wherein when the indication of position indicates that the door is nearer the fully open position than a position threshold, the opening velocity threshold is lower than when the indication of position indicates that the door is further away from the fully open position than the position threshold.

[0070] 8. The method according to any one of the preceding embodiments, wherein the door is a sliding door.

[0071] 9. The method according to any one of embodiments 1 to 7, wherein the door is a swing door.

[0072] 10. A status determiner for determining a state of a door based on accelerometer data of an accelerometer that is fixed to the door, the status determiner comprising: processing circuitry; and a memory circuitry storing instructions that, when executed by the processing circuitry, cause the status determiner to: determine that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determine that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0073] 11. A computer program for determining a state of a door based on accelerometer data of an accelerometer that is fixed to the door, the computer program comprising computer program code which, when executed on a status determiner causes the status determiner to: determine that the door has transitioned from an open state to a closing state, based on a magnitude of a velocity of the door in a first direction being greater than a closing velocity threshold; and determine that the door has transitioned from a closing state to an opening state, based on a magnitude of a velocity of the door in a second direction being greater than an opening velocity threshold, wherein the second direction is opposite from the first direction, wherein the opening velocity threshold is based on an indication of position of the door.

[0074] 12. A computer program product comprising a computer program according to embodiment 11 and a computer readable means comprising non-transitory memory in which the computer program is stored.

[0075] 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 being indicated by the following claims.

Claims

1. A method for determining a state of a door (15), the method being performed in a status determiner (1) based on accelerometer data of an accelerometer (18) that is fixed to the door (15), the method comprising: determining (40) that the door has transitioned from an open state (20) to a closing (21) state, based on a magnitude of a velocity of the door (15) in a first direction being greater than a closing velocity threshold (30); and determining (42) that the door has transitioned from a closing state (21) to an opening (23) state, based on a magnitude of a velocity of the door (15) in a second direction being greater than an opening velocity threshold (32), wherein the second direction is opposite from the first direction, wherein the opening velocity threshold (32) is based on an indication of position (29) of the door (15).

2. The method according to claim 1, wherein the velocity is determined by integrating an accelerometer signal of the accelerometer data.

3. The method according to claim 2, wherein the velocity is determined using a low- pass filter.

4. The method according to claim 2 or 3, wherein the indication of position of the door is determined by integrating the velocity.

5. The method according to any one of claims 1 to 3, wherein the indication of position of the door is determined based on a duration (37) of the door being in the closing state (21).

6. The method according to claim any one of the preceding claims, wherein when the indication of position (29) indicates that the door (15) is nearer the fully open position than a position threshold (25), the opening velocity threshold (32) is lower than when the indication of position (29) indicates that the door (15) is further away from the fully open position than the position threshold (25).

7. The method according to any one of the preceding claims, wherein the door (15) is a sliding door.

8. The method according to any one of claims 1 to 6, wherein the door (15) is a swing door.

9. A status determiner (i) for determining a state of a door (15) based on accelerometer data of an accelerometer (18) that is fixed to the door (15), the status determiner comprising: processing circuitry (60); and a memory circuitry (64) storing instructions (67) that, when executed by the processing circuitry, cause the status determiner (1) to: determine that the door has transitioned from an open state (20) to a closing (21) state, based on a magnitude of a velocity of the door (15) in a first direction being greater than a closing velocity threshold (30); and determine that the door has transitioned from a closing state (21) to an opening (23) state, based on a magnitude of a velocity of the door (15) in a second direction being greater than an opening velocity threshold (32), wherein the second direction is opposite from the first direction, wherein the opening velocity threshold (32) is based on an indication of position (29) of the door (15).

10. A computer program (67, 91) for determining a state of a door (15) based on accelerometer data of an accelerometer (18) that is fixed to the door (15), the computer program comprising computer program code which, when executed on a status determiner (1) causes the status determiner (1) to: determine that the door has transitioned from an open state (20) to a closing (21) state, based on a magnitude of a velocity of the door (15) in a first direction being greater than a closing velocity threshold (30); and determine that the door has transitioned from a closing state (21) to an opening (23) state, based on a magnitude of a velocity of the door (15) in a second direction being greater than an opening velocity threshold (32), wherein the second direction is opposite from the first direction, wherein the opening velocity threshold (32) is based on an indication of position (29) of the door (15).

11. A computer program product (64, 90) comprising a computer program according to claim 10 and a computer readable means comprising non-transitory memory in which the computer program is stored.