Compensating for gravity for determining an operational state of a door

Abstract

It is provided a method for compensating for gravity affecting an accelerometer (18) used for determining an operational state of a door (15). The method is performed by a gravity compensator (1). The method comprises: obtaining (40) a plurality of acceleration measurements by the accelerometer for a measurement period; calculating (42) a gravity component in the acceleration measurement by averaging the acceleration measurements; obtaining (44) an operational acceleration measurement; compensating (46) the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and providing (48) the compensated acceleration measurement for determining the operational state of the door.

Description

COMPENSATING FOR GRAVITY FOR DETERMINING AN OPERATIONAL STATE OF A DOORTECHNICAL FIELD

[0001] The present disclosure relates to the field of using accelerometer measurements for determining an operational state of a door and in particular to compensating for gravity affecting such acceleration measurements.BACKGROUND

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

[0003] The direction and magnitude of velocity can then be used to determine the operational state of the door, e.g. open state, closing state, closed state, opening state, or stationary partly closed state.

[0004] When the accelerometer is not perfectly aligned with the door, gravity forms a component of acceleration. The gravity component can lead to reduced accuracy in determining the operational state of the door.SUMMARY

[0005] One object is to improve how a gravity component is compensated for in accelerometer measurements that are used for determining an operational state of a door.

[0006] According to a first aspect, it is provided a method for compensating for gravity affecting an accelerometer used for determining an operational state of a door, the method being performed by a gravity compensator. The method comprises: obtaining a plurality of acceleration measurements by the accelerometer for a measurement period; calculating a gravity component in the acceleration measurement by averaging the acceleration measurements; repeating both the obtaining the plurality of acceleration measurements and calculating the gravity component to arrive at anupdated gravity component; determining that the updated gravity component has changed more than a threshold amount; sending a signal to indicate that the accelerometer has been realigned; obtaining an operational acceleration measurement; compensating the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and providing the compensated acceleration measurement for determining the operational state of the door. The obtaining the plurality of acceleration measurements comprises obtaining the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value; and the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer is still.

[0007] The obtaining the plurality of acceleration measurements may comprise obtaining the acceleration measurements for an equal integer number of opening operations and closing operations of the door.

[0008] The calculating the gravity component may comprise separately calculating an average for each dimension of the acceleration measurements.

[0009] The obtaining the operational acceleration measurement, compensating the operational acceleration measurement, and providing the compensates acceleration measurement may be repeated a plurality of times for the same gravity component.

[0010] According to a second aspect, it is provided a gravity compensator for compensating for gravity affecting an accelerometer used for determining an operational state of a door. The gravity compensator comprises: processing circuitry; and memory circuitry storing instructions that, when executed by the processing circuitry, cause the gravity compensator to: obtain a plurality of acceleration measurements by the accelerometer for a measurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; repeat the instructions to obtain the plurality of acceleration measurements and to calculate the gravity component, to arrive at an updated gravity component; determine that the updated gravity component has changed more than athreshold amount; send a signal to indicate that the accelerometer has been realigned; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and provide the compensated acceleration measurement for determining the operational state of the door. The instructions to obtain the plurality of acceleration measurements comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to obtain the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value; and the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer is still.[oon] The instructions to obtain the plurality of acceleration measurements may comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to obtain the acceleration measurements for an equal integer number of opening operations and closing operations of the door.

[0012] The instructions to calculate the gravity component may comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to separately calculate an average for each dimension of the acceleration measurements.

[0013] The gravity compensator may further comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to repeat the instructions to obtain the operational acceleration measurement, to compensate the operational acceleration measurement, and to provide the compensates acceleration measurement, a plurality of times for the same gravity component.

[0014] According to a third aspect, it is provided a computer program for compensating for gravity affecting an accelerometer used for determining an operational state of a door. The computer program comprises computer program code which, when executed on a gravity compensator causes the gravity compensator to: obtain a plurality of acceleration measurements by the accelerometer for ameasurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; repeat the execution of the computer program code to obtain the plurality of acceleration measurements and to arrive at an updated gravity component; determine that the updated gravity component has changed more than a threshold amount; send a signal to indicate that the accelerometer has been realigned; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and provide the compensated acceleration measurement for determining the operational state of the door. The program code to obtain the plurality of acceleration measurements may comprise computer program code which, when executed on a gravity compensator causes the gravity compensator to obtain the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value, wherein the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer is still.

[0015] 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.

[0016] 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

[0017] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0018] Fig 1 is a schematic diagram illustrating an environment in which embodiments presented herein can be applied;

[0019] Figs 2A-E are schematic diagrams illustrating embodiments of where the gravity compensator can be implemented;

[0020] Figs 3A-B are schematic graphs illustrating how a gravity component impacts measurements and how this can be compensated for;

[0021] Fig 4 is a flow chart illustrating embodiments for compensating for gravity affecting an accelerometer used for determining an operational state of a door;

[0022] Fig 5 is a schematic diagram illustrating components of the gravity compensator of Fig 1; and

[0023] Fig 6 shows one example of a computer program product comprising computer readable means.DETAILED DESCRIPTION

[0024] 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.

[0025] According to embodiments presented herein, a gravity component is identified and compensated for in accelerometer measurements. The gravity component is calculated based on taking several acceleration measurements, and averaging these. Once the gravity component is determined, operational measurements of acceleration are adjusted based on the gravity component. In this way, the operational state (closed, open, closing, opening, stationary partly closed) of the door can be determined more accurately. More details on the provided solution is provided below.

[0026] 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.

[0027] Optionally, in order to control access to the second physical space 16, an electronic lock 12 can be provided to selectively unlock and lock 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.

[0028] The operational state of the door can be under control of a door operator 13, where the operational state can e.g. be one of open, closed, opening, closing, stationary partly closed, etc. The door operator 13 can be a door opener, a door closer or both. The door operator 13 can be an active device that controls a motor for the door operations of opening and closing the door. Alternatively or additionally, the door operator comprises passive control elements, e.g. for providing a controlled door closing using mechanical elements such as springs and hydraulics.

[0029] An accelerometer 18 is provided fixed to the door 15, e.g. using adhesives, one or more screws, nails, Velcro, etc. The accelerometer 18 obtains acceleration measurements. The acceleration measurements can be in one dimension, e.g. a reflecting a linear horizontal movement of the door 15 when this is a sliding door. Alternatively, the acceleration measurement can be provided in three dimensions.

[0030] The acceleration measurements are provided to a state determiner 2. The state determiner 2 uses the acceleration measurements to determine velocity, direction of movement 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 15 itself. When there are multiple door leaves of the door 15, there can be oneaccelerometer fixed to each door leaf. Alternatively, when multiple door leaves move synchronously, the door leaves are considered to move in opposite but with velocities of equal magnitudes, whereby it is sufficient to fix a single accelerometer 18 to one of the door leaves.

[0031] According to embodiments presented herein, a gravity compensator 1 is provided. The gravity compensator 1 is used to determine a gravity component in the acceleration measurements from the accelerometer 18. Once determined, the gravity component is provided to the state determiner 2, so that the gravity component can be compensated for when determining the operational state of the door 15.

[0032] The gravity compensator 1 can be provided at the same site as the door 15 and the accelerometer 18 or the gravity compensator 1 can be provided remotely. When the gravity compensator 1 is provided remotely, the gravity compensator 1 can receive the acceleration measurements from the accelerometer 18 directly or via intermediate components, e.g. via a wireless network, cellular network and / or the Internet.

[0033] Figs 2A-D are schematic diagrams illustrating embodiments of where the gravity compensator 1 can be implemented.

[0034] In Fig 2A, the gravity compensator 1 shown implemented in the accelerometer 18. The accelerometer 18 is thus the host device for the gravity compensator 1 in this implementation. In this embodiment, the accelerometer 18 includes processing capability (see Fig 5 and corresponding text below) to perform a method in line with what is shown in Fig 4 and that is described below.

[0035] In Fig 2B, the gravity compensator 1 shown implemented in the state determiner 2. The state determiner 2 is thus the host device for the gravity compensator 1 in this implementation. In this embodiment, the gravity component and the operational state of the door is determined in the same physical device.

[0036] In Fig 2C, the gravity compensator 1 shown implemented in the electronic lock 12. The electronic lock 12 is thus the host device for the gravity compensator 1 in this implementation. It is to be noted that this embodiment can be combined with thatof Fig 2 A, i.e. both the gravity compensator 1 and the state determiner 2 can optionally be implemented in the electronic lock 12.

[0037] In Fig 2D, the gravity compensator 1 shown implemented in the door operator 13. The door operator 13 is thus the host device for the gravity compensator 1 in this implementation.

[0038] In Fig 2E, as illustrated in Fig 1, the gravity compensator 1 is shown implemented as a stand-alone device. The gravity compensator 1 thus does not have a host device in this implementation.

[0039] Figs 3A-B are schematic graphs illustrating how a gravity component impacts measurements and how this can be compensated for. The horizontal axis in Figs 3A-V represents time t and the vertical axis represents velocity v. The velocity 28 of the door 15 can be derived by integrating the accelerometer measurements of from the accelerometer 18. Figs 3A-B illustrate the effect of gravity in one dimension, but the same principle is applicable to all (i.e. the other two) dimensions.

[0040] Looking first to Fig 3A, the effect of gravity is shown. Since gravity is a constant acceleration, its effect, when integrated, is a linear offset to non-gravitational acceleration. In other words, when the accelerometer is not placed at a perfect angle, gravity is a constant offset to the acceleration measurements. When acceleration is integrated to obtain velocity (as illustrated here), there is a linear gravity component in the velocity that is applied in addition to the non-gravity acceleration. While the effect is exaggerated in Fig 3A for illustrative purposes, the linear effect of gravity can be seen as a line with an angle a. The tilt can be positive or negative.

[0041] Looking now to Fig 3B, the same signal as in Fig 1 is illustrated, but where compensation for the gravity component has been applied. It can be seen how the velocity here returns to zero, e.g. after an opening (or closing) operation has been performed and the door is stationary, i.e. no velocity. It is clear that the velocity curve of Fig 3B is much more suited for determining the operational state of the door.

[0042] Fig 4 is a flow chart illustrating embodiments for compensating for gravity affecting an accelerometer 18 used for determining an operational state of a door 15. The method is performed by the gravity compensator 1.

[0043] In an obtain acceleration measurements step 40, the gravity compensator 1 obtains a plurality of acceleration measurements by the accelerometer for a measurement period. The acceleration measurements can e.g. be obtained over a wireless interface with the accelerometer 18. The measurement period can be a fixed period of time or the measurement period can be dynamically determined as described below.

[0044] In one embodiment, the acceleration measurements are obtained for a continuous period (of a set duration) in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value. By high-pass filtering the magnitudes, the (hitherto possibly unknown) gravity component (which is blocked by the high-pass filtering) is not interpreted as a movement, when the accelerometer 18 is still. The threshold value can be set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer 18 is still. The period can be reset whenever the acceleration measurements exceed the threshold value. Eventually, there is a continuous period of time where the accelerometer 18 is still (determined by the acceleration measurements being smaller in magnitude than the threshold value). When the measurements are averaged for that period, as detailed below, the average should be zero, and any deviation from zero can be considered to be the gravity component.

[0045] Alternatively, the acceleration measurements are obtained for an equal integer number of opening operations and closing operations of the door 15. The opening operations and the closing operations can be determined by state determiner 2. Since each pair of door operations consisting of an opening operation and a closing operation results in the accelerometer being back in the same place, an equal integer number of opening operations and closing operations also results in the accelerometer being back in the same place. When the measurements are averaged for the pairs of openings and closings, as detailed below, the average should be zero, and any deviation from zero can be considered to be the gravity component.

[0046] In one embodiment, the acceleration measurements are obtained for a sliding window function of an equal integer number of opening operations and closing operations (door cycles) of the door 15, i.e. the last n number of door cycles. This could compensate for small changes of the sensor placement or mechanical wear over time, which could impact the acceleration measurements. Furthermore, the calculation of the gravity component (in the next step) occurs continuously, whereby no determination is needed for when the gravity component is to be updated.

[0047] In a calculate gravity component step 42, the gravity compensator 1 calculates a gravity component in the acceleration measurement by averaging the acceleration measurements.

[0048] The gravity component can be calculated by separately as an average for each dimension of the acceleration measurements. In other words, the x dimension of the gravity component can be calculated based only on acceleration determined in the x dimension, the y dimension of the gravity component can be calculated based only on acceleration determined in the y dimension, and the z dimension of the gravity component can be calculated based only on acceleration determined in the z dimension,

[0049] Please note that steps 54 and 56 will be described below, as these relate to when the gravity components has changed compared to previous iterations.

[0050] In an obtain operational acceleration measurement step 44, the gravity compensator 1 obtains an operational acceleration measurement, i.e. for determining the operational state of the door 15.

[0051] In a compensate step 46, the gravity compensator 1 compensates the operational acceleration measurement based on the gravity component. This yields a gravity compensated acceleration measurement. The compensation can be performed directly on acceleration measurements. Specifically, in one embodiment, the compensation occurs by removing the offset of the gravity component. This is a simple way to remove the impact of the gravity.

[0052] In one embodiment, the compensation occurs, when applied in three dimensions, by performing a matrix rotation. In this way, the accelerometermeasurements are rotated. The determined gravity component is then used as calibration data to estimate the orientation of the sensor, e.g. given by Euler angles. When the rotation matrix determined by Euler angles is applied to the operational acceleration measurement, the result is as if the sensor was perfectly aligned.

[0053] In a provide compensated acceleration measurement step 48, the gravity compensator 1 provides the compensated acceleration measurement for determining the operational state of the door.

[0054] In an optional conditional repeat operational measurements step 50, the gravity compensator 1 determines whether to repeat obtaining measurements for determining the operational state. For instance, the operational measurements can be repeated indefinitely as long as the gravity compensator 1 and the accelerometer 18 are powered and are operational. Alternatively, the operational measurements can be repeated for a certain time after a certain magnitude of acceleration is detected. If the obtaining measurements for determining the operational state is to be repeated, the method returns to the obtain operational acceleration step 44.

[0055] In the optional conditional repeat gravity determination step 52, the gravity compensator 1 determines whether to repeat determining the gravity component.

[0056] If the determining the gravity component is to be repeated, the method returns to the obtain acceleration measurements step 40 to arrive at an updated gravity component. Otherwise, the method ends.

[0057] When the gravity component is redetermined in a subsequent iteration of determining the gravity component, the method optionally comprises, after the calculate gravity component step 42 an additional two steps.

[0058] In an optional conditional significant change step 54, the gravity compensator 1 determining whether the updated gravity component has changed more than a threshold amount from the most recent preceding value. If this is the case, the method proceeds to send signal step 56. Otherwise, the method proceeds to the obtain operational acceleration measurement step 44.

[0059] In the send signal step 56, the gravity compensator 1 sends a signal to indicate that the accelerometer has been realigned. The realignment can e.g. be due to external impact and / or sabotage on the door or on the accelerometer. Hence, the gravity component determination can be exploited to detect events that can affect the operation of the door 15. The signal can e.g. be used to trigger maintenance personnel to evaluate and possibly repair the state of the door 15 and the accelerometer 18.

[0060] Using the solutions presented herein, the effect of gravity on acceleration measurements is compensated for, which increases tolerance for mounting the sensor and increases accuracy of determining the operational state of the door using the acceleration measurements.

[0061] Fig 5 is a schematic diagram illustrating components of the gravity compensator 1 of Fig 1. It is to be noted that when the gravity compensator 1 is implemented in a host device, one or more of the mentioned components can be shared with the host device. 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 4 above.

[0062] 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.

[0063] 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.

[0064] The gravity compensator 1 further comprises an 1 / O interface 62 for communicating with external and / or internal entities, e.g. for obtaining acceleration measurements. The I / O interface 62 can employ wired communication, e.g. based on Ethernet, and / or wireless communication, e.g. Wi-Fi, Bluetooth, Bluetooth Low Energy, and / or a cellular network, complying with any one or a combination of sixth generation (6G) mobile networks, next generation mobile networks (fifth generation, 5G), LTE (Long Term Evolution), UMTS (Universal Mobile Telecommunications System) utilising W-CDMA (Wideband Code Division Multiplex), or any other current or future wireless network, as long as the principles described hereinafter are applicable.

[0065] Other components of the gravity compensator 1 are omitted in order not to obscure the concepts presented herein.

[0066] Fig 6 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 5. 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.

[0067] Here now follows a list of enumerated embodiments from another perspective.

[0068] 1. A method for compensating for gravity affecting an accelerometer used for determining an operational state of a door, the method being performed by a gravity compensator, the method comprising: obtaining a plurality of acceleration measurements by the accelerometer for a measurement period;calculating a gravity component in the acceleration measurement by averaging the acceleration measurements; obtaining an operational acceleration measurement; compensating the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and providing the compensated acceleration measurement for determining the operational state of the door.

[0069] 2. The method according to embodiment 1, wherein the obtaining the plurality of acceleration measurements comprises obtaining the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value.

[0070] 3. The method according to embodiment 2, wherein the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer is still.

[0071] 4. The method according to embodiment 1, wherein the obtaining the plurality of acceleration measurements comprises obtaining the acceleration measurements for an equal integer number of opening operations and closing operations of the door.

[0072] 5. The method according to any one of the preceding embodiments, wherein the calculating the gravity component comprises separately calculating an average for each dimension of the acceleration measurements.

[0073] 6. The method according to any one of the preceding embodiments, wherein the obtaining the operational acceleration measurement, compensating the operational acceleration measurement, and providing the compensates acceleration measurement are repeated a plurality of times for the same gravity component.

[0074] 7. The method according to any one of the preceding embodiments, wherein the obtaining the plurality of acceleration measurements and calculating the gravity component are repeated to arrive at an updated gravity component.

[0075] 8. The method according to embodiment 7, further comprising: determining that the updated gravity component has changed more than a threshold amount; and sending a signal to indicate that the accelerometer has been realigned.

[0076] 9. A gravity compensator for compensating for gravity affecting an accelerometer used for determining an operational state of a door, the gravity compensator comprising: processing circuitry; and memory circuitry storing instructions that, when executed by the processing circuitry, cause the gravity compensator to: obtain a plurality of acceleration measurements by the accelerometer for a measurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and provide the compensated acceleration measurement for determining the operational state of the door.

[0077] 10. The gravity compensator according to embodiment 9, wherein the instructions to obtain the plurality of acceleration measurements comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to obtain the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value.

[0078] 11. The gravity compensator according to embodiment 10, wherein the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer is still.

[0079] 12. The gravity compensator according to embodiment 9, wherein the instructions to obtain the plurality of acceleration measurements comprise instructionsthat, when executed by the processing circuitry, cause the gravity compensator to obtain the acceleration measurements for an equal integer number of opening operations and closing operations of the door.

[0080] 13. The gravity compensator according to any one of embodiments 9 to 12, wherein the instructions to calculate the gravity component comprise instructions that, when executed by the processing circuitry, cause the gravity compensator to separately calculate an average for each dimension of the acceleration measurements.

[0081] 14. The gravity compensator according to any one of embodiments 9 to 13, further comprising instructions that, when executed by the processing circuitry, cause the gravity compensator to repeat the instructions to obtain the operational acceleration measurement, to compensate the operational acceleration measurement, and to provide the compensates acceleration measurement, a plurality of times for the same gravity component.

[0082] 15. The gravity compensator according to any one of embodiments 9 to 14, further comprising instructions that, when executed by the processing circuitry, cause the gravity compensator to repeat the instructions to obtain the plurality of acceleration measurements and to calculate the gravity component, to arrive at an updated gravity component.

[0083] 16. The gravity compensator according to embodiment 15, further comprising instructions that, when executed by the processing circuitry, cause the gravity compensator to: determine that the updated gravity component has changed more than a threshold amount; and send a signal to indicate that the accelerometer has been realigned.

[0084] 17. A computer program for compensating for gravity affecting an accelerometer used for determining an operational state of a door, the computer program comprising computer program code which, when executed on a gravity compensator causes the gravity compensator to: obtain a plurality of acceleration measurements by the accelerometer for ameasurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and provide the compensated acceleration measurement for determining the operational state of the door.

[0085] 18. A computer program product comprising a computer program according to embodiment 17 and a computer readable means comprising non-transitory memory in which the computer program is stored.

[0086] 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

CLAIMS1. A method for compensating for gravity affecting an accelerometer (18) used for determining an operational state of a door (15), the method being performed by a gravity compensator (1), the method comprising: obtaining (40) a plurality of acceleration measurements by the accelerometer for a measurement period; calculating (42) a gravity component in the acceleration measurement by averaging the acceleration measurements; repeating both the obtaining (40) the plurality of acceleration measurements and calculating (42) the gravity component to arrive at an updated gravity component; determining (54) that the updated gravity component has changed more than a threshold amount; sending (56) a signal to indicate that the accelerometer has been realigned; obtaining (44) an operational acceleration measurement; compensating (46) the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and providing (48) the compensated acceleration measurement for determining the operational state of the door; wherein the obtaining (40) the plurality of acceleration measurements comprises obtaining the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value; and the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer (18) is still.

2. The method according to claim 1, wherein the obtaining (40) the plurality of acceleration measurements comprises obtaining the acceleration measurements for an equal integer number of opening operations and closing operations of the door (15).

3. The method according to claim 1 or 2, wherein the calculating (42) the gravity component comprises separately calculating an average for each dimension of the acceleration measurements.

4. The method according to any one of the preceding claims, wherein the obtaining (44) the operational acceleration measurement, compensating (46) the operational acceleration measurement, and providing (48) the compensates acceleration measurement are repeated a plurality of times for the same gravity component.

5. A gravity compensator (1) for compensating for gravity affecting an accelerometer (18) used for determining an operational state of a door (15), the gravity compensator (1) comprising: processing circuitry (60); and memory circuitry (64) storing instructions (67) that, when executed by the processing circuitry, cause the gravity compensator (1) to: obtain a plurality of acceleration measurements by the accelerometer for a measurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; repeat the instructions to obtain the plurality of acceleration measurements and to calculate the gravity component, to arrive at an updated gravity component; determine that the updated gravity component has changed more than a threshold amount; send a signal to indicate that the accelerometer has been realigned; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; and provide the compensated acceleration measurement for determining the operational state of the door; wherein the instructions to obtain the plurality of acceleration measurements comprise instructions (67) that, when executed by the processing circuitry, cause the gravity compensator (1) to obtain the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value; and the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer (18) is still.

6. The gravity compensator (1) according to claim 5, wherein the instructions to obtain the plurality of acceleration measurements comprise instructions (67) that, when executed by the processing circuitry, cause the gravity compensator (1) to obtain the acceleration measurements for an equal integer number of opening operations and closing operations of the door (15).

7. The gravity compensator (1) according to claim 5 or 6, wherein the instructions to calculate the gravity component comprise instructions (67) that, when executed by the processing circuitry, cause the gravity compensator (1) to separately calculate an average for each dimension of the acceleration measurements.

8. The gravity compensator (1) according to any one of claims 5 to 7, further comprising instructions (67) that, when executed by the processing circuitry, cause the gravity compensator (1) to repeat the instructions to obtain the operational acceleration measurement, to compensate the operational acceleration measurement, and to provide the compensates acceleration measurement, a plurality of times for the same gravity component.

9. A computer program (67, 91) for compensating for gravity affecting an accelerometer (18) used for determining an operational state of a door (15), the computer program comprising computer program code which, when executed on a gravity compensator (1) causes the gravity compensator (1) to: obtain a plurality of acceleration measurements by the accelerometer for a measurement period; calculate a gravity component in the acceleration measurement by averaging the acceleration measurements; repeat the execution of the computer program code to obtain the plurality of acceleration measurements and to arrive at an updated gravity component; determine that the updated gravity component has changed more than a threshold amount; send a signal to indicate that the accelerometer has been realigned; obtain an operational acceleration measurement; compensate the operational acceleration measurement based on the gravity component, yielding a gravity compensated acceleration measurement; andprovide the compensated acceleration measurement for determining the operational state of the door; wherein the program code to obtain the plurality of acceleration measurements comprise computer program code which, when executed on a gravity compensator (1) causes the gravity compensator (i) to obtain the acceleration measurements for a continuous period in which high-pass filtered magnitudes of all acceleration measurements are less than a threshold value, wherein the threshold value is set to a value such that the high-pass filtered magnitudes of the acceleration measurements being lower than the threshold value indicate that the accelerometer (18) is still.

10. A computer program product (64, 90) comprising a computer program according to claim 9 and a computer readable means comprising non-transitory memory in which the computer program is stored.

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