TWI811920B - Wearing detection method, wearable device, and computer readable storage medium - Google Patents

Abstract

The disclosure provides a wearing detection method, a wearable device, and a computer readable storage medium. The method includes: in response to determining that the wearable device is in a static state, emitting a plurality of first photoplethysmography (PPG) signals, and detecting a plurality of second PPG signals corresponding to the first PPG signals; obtaining a zero-crossing rate corresponding to the second PPG signals; and in response to determining that the zero-crossing rate of the second PPG signals is higher than a reference threshold, determining that the wearable device is in an unworn state

Description

Wearable detection method, wearable device and computer-readable storage medium

The present invention relates to a wear detection mechanism, and in particular, to a wear detection method, a wearable device and a computer-readable storage medium that can detect whether a wearable device is in a worn state or an unworn state.

Generally speaking, wearable devices are generally provided with detection components specifically designed to detect whether the wearable device is being worn by a user. For example, a smart watch may be provided with a proximity sensor (such as an infrared transceiver circuit) on the contact surface with the user that is specifically designed to detect whether the smart watch is being worn by the user. However, such a dedicated proximity sensor not only occupies a part of the space on the wearable device, but also increases the power consumption and implementation cost of the wearable device.

Therefore, for those skilled in the art, how to design a device that can accurately detect whether the wearable device is being used without the power consumption and implementation cost of a dedicated proximity sensor? The mechanism by which the wearer wears the device is indeed an important issue.

In view of this, the present invention provides a wear detection method, a wearable device and a computer-readable storage medium, which can be used to solve the above technical problems.

The present invention provides a wear detection method, suitable for a wearable device, including: responding to determining that the wearable device is in a stationary state, emitting a plurality of first light volume signals, and detecting signals corresponding to the plurality of first light volumes. a plurality of second light volume signals of the volume signal; obtaining a zero-crossing rate corresponding to the plurality of second light volume signals; and in response to determining that the zero-crossing rate of the plurality of second light volume signals is higher than a reference The threshold value determines that the wearable device is in an unworn state.

The invention provides a wearable device, which includes a light volume signal transceiver and a processor. The processor is coupled to the optical volumetric signal transceiver. In response to the processor determining that the wearable device is in a stationary state, the processor controls the light volume signal transceiver to emit a plurality of first light volume signals, and controls the light volume signal transceiver to detect signals corresponding to the plurality of first light volumes. A plurality of second light volume signals of the signal. The processor obtains a zero-crossing rate corresponding to the plurality of second light volume signals. In response to the processor determining that the zero-crossing rates of the plurality of second light volume signals are higher than a reference threshold, the processor determines that the wearable device is in an unworn state.

The invention provides a computer-readable storage medium. The computer-readable storage medium records an executable computer program. The executable computer program is loaded by a wearable device to perform the following steps: in response to determining that the wearable device is in a stationary state, emitting A plurality of first light volume signals, and detecting a plurality of second light volume signals corresponding to the plurality of first light volume signals; obtaining a zero-crossing rate corresponding to the plurality of second light volume signals; reacting In response to determining that the zero-crossing rates of the plurality of second light volume signals are higher than a reference threshold value, the wearable device is determined to be in an unworn state; in response to determining that the zero-crossing rates of the plurality of second light volume signals are not high. Based on the reference threshold value, it is determined that the wearable device is in a wearing state.

Please refer to FIG. 1 , which is a schematic diagram of a wearable device according to an embodiment of the present invention. In FIG. 1 , a wearable device 100 includes a photoplethysmography (PPG) signal transceiver 101 , an accelerometer 102 and a processor 104 , where the PPG signal transceiver 101 and the accelerometer 102 can be coupled to the processor 104 .

In some embodiments, the PPG signal transceiver 101 may be disposed stationary on the wearable device 100 on the contact surface with the user (or the wearer). In one embodiment, the PPG signal transceiver 101 may include, for example, a PPG signal transmitter 101a and a PPG signal receiver 101b, where the PPG signal transmitter 101a may be used to transmit PPG signals (which are generally green light), and these PPG signals It may be received by the PPG signal receiver 101b after being reflected by some objects.

In one embodiment, when the wearable device 100 is in a wearing state being worn by the user, the PPG signal transmitted by the PPG signal transmitter 101a may be reflected by the user's skin/subcutaneous tissue, and the reflected The PPG signal can be received by the PPG signal receiver 101b.

In one embodiment, human blood vessels and blood flow may change with the beating of the heart, such as the expansion and contraction of blood vessels. In this case, after the PPG signal is illuminated by the user's blood vessel and reflected, the intensity of the reflected PPG signal received by the PPG signal receiver 101b will also show a corresponding change. Based on this, the processor 104 can estimate the user's heart rate based on the intensity change of the PPG signal received by the PPG signal receiver 101b.

Please refer to FIG. 2 , which is a schematic diagram of PPG signal changes based on FIG. 1 . In FIG. 2 , the PPG signal waveform 210 may include waveforms 210a, 210b, and 210c, where the waveform 210a is, for example, the PPG signal change when the wearable device 100 is in a wearing state (ie, the wearable device 100 is being worn on the user). , the waveform 210b is, for example, the PPG signal change when the user takes off the wearable device 100 , and the waveform 210c is, for example, when the wearable device 100 is in an unworn state (for example, the wearable device 100 is taken off and placed somewhere). PPG signal changes.

As shown in the waveform 210a of FIG. 2, when the wearable device 100 is in the wearing state, the PPG signal will show corresponding changes in response to the user's heart rate. At this time, since the signal received by the PPG signal receiver 101b is relatively low-frequency and has less noise, the waveform of the PPG signal is also relatively clean. In this case, the processor 104 can estimate the user's heart rate based on the waveform 210a.

When the wearable device 100 is being taken off, since the signal components received by the PPG signal receiver 101b are relatively complex (which may include PPG signals reflected by the user and other objects), the PPG signal will change more drastically. and unstable, as shown in waveform 210b.

When the wearable device 100 is in the unworn state, since the PPG signal received by the PPG signal receiver 101b will contain more noise, the change of the PPG signal will also be relatively high-frequency and unstable, as shown in the waveform 210c.

In some embodiments, the accelerometer 102 may be used, for example, to detect acceleration values of the wearable device 100 on multiple axes, and these acceleration values may change in response to the movement of the wearable device 100 . Therefore, the processor 104 can determine whether the wearable device 100 is in a stationary state or a moving state based on the acceleration value provided by the accelerometer 102 .

In one embodiment, the processor 104 can determine the movement energy parameter of the wearable device 100 after obtaining the acceleration value from the accelerometer 102, and determine whether the movement energy parameter is lower than an energy threshold. In one embodiment, the processor 104 may, for example, estimate the corresponding activity count (activity count) based on the above acceleration value as the movement energy parameter of the wearable device 100, but it may not be limited thereto.

In one embodiment, in response to determining that the movement energy parameter is not higher than the energy threshold, the processor 104 may determine that the wearable device 100 is in a stationary state. On the other hand, in response to determining that the movement energy parameter is higher than the energy threshold, the processor 104 may determine that the wearable device 100 is in a moving state.

Please refer to FIG. 3 , which is a graph of activity count changes according to an embodiment of the present invention. It can be seen from FIG. 3 that when the wearable device 100 is in a stationary state, its corresponding activity count will be in a state not higher than the energy threshold value (for example, 0) for a long time. Therefore, the processor 104 can accordingly determine that the wearable device 100 is in a stationary state, but may not be limited thereto.

In an embodiment of the present invention, the processor 104 can access specific modules and program codes to implement the wear detection method proposed by the present invention.

Please refer to FIG. 4 , which is a flow chart of a wear detection method according to an embodiment of the present invention. The method of this embodiment can be executed by the wearable device 100 in FIG. 1 . The details of each step in FIG. 4 will be described below with reference to the components shown in FIG. 1 .

First, in step S410, in response to determining that the wearable device 100 is in a stationary state, the processor 104 controls the PPG signal transceiver 101 to transmit a plurality of first PPG signals S1 and detect a plurality of first PPG signals S1 corresponding to the first PPG signal S1. 2. PPG signal S2. In one embodiment, the processor 104 can detect whether the wearable device 100 is in a stationary state based on the method mentioned in the description of FIG. 3 , for example, but it is not limited thereto.

In one embodiment, after determining that the wearable device 100 is in a stationary state, the processor 104 may, for example, control the PPG signal transmitter 101a to send the first PPG signal S1, and control the PPG signal receiver 101b to receive the second PPG signal S2, where The second PPG signal S2 is, for example, a PPG signal formed by reflecting the first PPG signal S1. Among them, if it is determined that the wearable device 100 is in a stationary state and the PPG signal transmitter 101a is in a state of continuously sending PPG signals, then part of the PPG signals in the PPG signals that continue to be sent will be used as the first PPG signal S1; if it is determined that the wearable device 100 is in a stationary state, When the device 100 is in a stationary state and the PPG signal transmitter 101a is in a state of not transmitting a PPG signal, the PPG signal transmitter 101a is controlled to transmit the first PPG signal S1.

In one embodiment, assuming that the processor 104 determines that the wearable device 100 is in a stationary state at the i-th time point, the processor 104 can control the PPG signal receiver 101b to detect a signal between the i+N-th time point and the i+-th time point. Multiple PPG signals between N+M time points are used as the above-mentioned second PPG signal S2, where i is an index value, and N and M are integers.

In different embodiments, the values of M and N can be determined according to the designer's needs. In one embodiment, when N is 0 and M is a positive integer, the processor 104 can be understood to control the PPG signal receiver 101b to detect the i-th time point immediately after determining that the wearable device 100 is in a stationary state. and a plurality of PPG signals between the i+Mth time point as the above-mentioned second PPG signal S2. In one embodiment, assuming that the value of M is selected to correspond to 2 seconds, the above operation can be understood as immediately controlling the PPG signal receiver 101b to detect multiple signals within 2 seconds after determining that the wearable device 100 is in a stationary state. The first PPG signal is used as the above-mentioned second PPG signal S2.

In some embodiments, limited by the hardware characteristics of the PPG signal transceiver 101 , if the PPG signal is detected immediately after determining that the wearable device 100 is in a stationary state (that is, the case where N is 0), all the problems may occur. The measured PPG signal is relatively unstable, which affects subsequent judgments.

Therefore, in some embodiments, N and M can both be set to positive integers. When N and M are both positive integers, the processor 104 can be understood to wait for N time points after determining that the wearable device 100 is in a stationary state. The PPG signal receiver 101b is then controlled to detect a plurality of PPG signals between the i+N-th time point and the i+N+M-th time point as the second PPG signal S2. In one embodiment, assuming that the values of N and M are selected to correspond to 3 seconds and 2 seconds respectively, the above operation can be understood as waiting for 3 seconds before controlling the PPG after determining that the wearable device 100 is in a stationary state. The signal receiver 101b detects multiple PPG signals within 2 seconds as the second PPG signal S2, but is not limited to this.

Afterwards, in step S420, the processor 104 obtains a zero cross rate corresponding to the plurality of second PPG signals S2.

Please refer to FIG. 5A and FIG. 5B , which are schematic diagrams of estimating the zero-crossing rate of a signal according to an embodiment of the present invention. In Figure 5A, assume that the length is 1 second and the frequency (in A certain signal A with a sampling frequency of 100Hz (represented by Represents) The waveform 511 appears after sampling. It can be seen from the waveform 511 that among the 100 sampled points, there are 3 zero-crossing points (ie, circled points). Therefore, in the scenario of Figure 5A, the zero-crossing rate of signal A can be estimated to be 3/100, that is .

Additionally, in Figure 5B, assume that the length is 1 second and the frequency (in A certain signal B whose expression) is 2 presents a waveform 512 after being sampled at a sampling frequency of 100Hz. It can be seen from the waveform 512 that among the 100 sampled points, there are a total of 5 zero-crossing points (ie, circled points). Therefore, in the scenario of Figure 5B, the zero-crossing rate of signal B can be estimated to be 5/100, that is .

It can be seen from FIG. 5A and FIG. 5B that after obtaining a certain signal, the processor 104 can estimate the zero-crossing rate of the signal based on the corresponding sampling frequency and the frequency of the signal. For example, the zero-crossing rate of a signal can be estimated as ,in the frequency of this signal, and is the sampling frequency used to sample this signal.

Based on this, in step S420, after the processor 104 obtains the second PPG signal S2, the zero-crossing rate of the second PPG signal S2 can be estimated according to the above principle. In an embodiment, it is assumed that the first frequency of the second PPG signal S2 is And the corresponding sampling frequency is , then the zero-crossing rate (expressed in CR) of the second PPG signal S2 can be characterized as " ”, but it is not limited to this.

Thereafter, in step S430, the processor 104 determines whether the zero-crossing rates (CR) of the plurality of second PPG signals S2 are higher than the reference threshold value TH.

In one embodiment, the processor 104 may first execute a certain mechanism to determine the reference threshold TH. For example, the processor 104 may obtain a reference zero-crossing rate (as represents), and correct this reference zero-crossing rate to the above-mentioned reference threshold value TH based on the correction factor.

In one embodiment, during the process of obtaining the reference zero-crossing rate, the processor 104 may first obtain a plurality of historical PPG signals, and obtain the reference zero-crossing rate based on the sampling frequency (i.e., ) and the second frequency of these historical PPG signals (with represents) estimating the above-mentioned reference zero-crossing rate, wherein the above-mentioned historical PPG signal is obtained when the wearable device 100 is in the wearing state. In one embodiment, the reference zero crossing rate For example, it can be represented as " ”.

In addition, as mentioned previously, when the wearable device 100 is in the wearing state, the PPG signal (ie, the historical PPG signal) received by the PPG signal receiver 101b will correspond to the user's heart rate. Therefore, in one embodiment, the second frequency of the historical PPG signal ( ) can also be expressed as HR/60, where HR is, for example, the user's heart rate, and the unit is, for example, beats per minute (BPM). In this case, the reference zero-crossing rate For example, it can be represented as " ”. In some embodiments, the HR can be the average heart rate of the user within a certain period of time, such as the average heart rate in n seconds before the wearable device 100 becomes stationary, but it is not limited to this.

In some embodiments, after obtaining the reference zero-crossing rate Afterwards, the processor 104 may correct the reference zero-crossing rate to the above-mentioned reference threshold value TH based on certain correction factors. In one embodiment, the correction factor may be selected to be a value greater than 1, for example, but it is not limited to this. In other words, the processor 104 may use a value higher than the reference zero-crossing rate as the reference threshold value TH. Because individual heart rhythms have a wide distribution range, for example, the resting heart rate can be as low as about 50BPM, while the heart rate during exercise can be as high as about 200BPM. In addition, different users will have different heart rate zones, and their resting heart rate and maximum heart rate will also be different. Therefore, if the reference threshold value TH is designed to be a certain value, misjudgments may occur between different users. The parameter HR in the reference threshold value TH in this embodiment is the user's heart rate, which means that the reference threshold value TH will be adjusted according to the user's heart rate. Therefore, different users will have different reference threshold values TH, which can reduce the risk of misjudgment. happen. In another embodiment of the present case, the parameter HR in the reference threshold value TH can be the user's real-time personal heart rate before taking off the watch, for example, the average heart rate in n seconds before the wearable device 100 becomes stationary. Therefore, it will change accordingly. The user's current heart rate changes and there are different reference thresholds TH. It can more accurately determine whether the zero-crossing rate exceeds the real-time reference threshold TH, further determine whether the user is indeed off the watch, and greatly reduce the occurrence of misjudgments.

In one embodiment, if the processor 104 determines in step S430 that the zero-crossing rate of the second PPG signal S2 is higher than the reference threshold TH, the processor 104 may continue to execute step S440 to determine that the wearable device 100 is in the unworn state. .

Specifically, as mentioned previously, when the wearable device 100 is in the unworn state, the PPG signal receiver 101b will receive a PPG signal with a higher frequency, and the PPG signal with a higher frequency will have a corresponding Higher zero-crossing rate. Therefore, when the processor 104 determines that the zero-crossing rate of the second PPG signal S2 is higher than the set reference threshold value TH, the processor 104 can accordingly determine that the wearable device 100 should be in the unworn state.

Please refer to FIG. 6 , which is a change diagram of the zero-crossing rate of the PPG signal according to an embodiment of the present invention. In FIG. 6 , it is assumed that the wearable device 100 is in a worn state (eg, worn on the user) before time point T, and the wearable device 100 changes to an unworn state (eg, taken off and placed on the user's body) after time point T. somewhere). It can be seen from Figure 6 that the zero-crossing rate of the PPG signal between time points T is low, while the zero-crossing rate of the PPG signal after time point T is high.

In one embodiment, the processor 104 may determine that the wearable device 100 before time point T is in the wearing state based on the previously taught mechanism. In this case, the processor 104 can obtain the partial PPG number when the wearable device 100 is in the wearing state (for example, the partial PPG signal before time point T) as the historical PPG signal to estimate the reference zero-crossing rate CR' and the corresponding reference Threshold value TH.

In one embodiment, when the processor 104 detects that the wearable device 100 is in a stationary state at time point T, the processor 104 may detect the required second PPG signal S2 based on the previous teaching. In the scenario of FIG. 6 , the processor 104 may use a portion of the PPG signal measured after the time point T as the second PPG signal S2 to be considered, and estimate its zero-crossing rate accordingly.

In FIG. 6 , the processor 104 may determine that the wearable device 100 should be in the unworn state at this time after determining that the zero-crossing rate of the considered second PPG signal S2 is higher than the reference threshold value TH. In this way, the wearable device 100 can achieve the technical effect of detecting whether the wearable device 100 is being worn without being provided with a proximity sensor dedicated to detecting the human body.

Please refer to FIG. 7 , which illustrates various waveform diagrams according to an embodiment of the present invention. In FIG. 7 , waveform 711 corresponds to, for example, a change in the movement energy parameter of the wearable device 100 , waveform 712 , for example, corresponds to a change in the enable signal of the PPG signal receiver 101 b , waveform 713 , for example, corresponds to a change in the zero-crossing rate of the PPG signal, and waveform 711 corresponds to, for example, a change in the movement energy parameter of the wearable device 100 . 714 corresponds to whether the wearable device 100 is in a wearing state, for example.

It can be seen from the waveform 711 that before time point T1, the movement energy parameters of the wearable device 100 are all greater than 0, that is, the wearable device 100 is in a non-stationary state before time point T1. In this case, the waveform 714 may be, for example, corresponding to a high level to indicate that the wearable device 100 is in a wearing state.

In addition, it can also be seen from the waveform 711 that the movement energy parameter of the wearable device 100 becomes 0 at time point T1, so the processor 104 can determine that the wearable device 100 is in a stationary state at time point T1. Afterwards, the processor 104 may receive the PPG signal through the PPG signal receiver 101b at time point T3 after waiting for the time D1 corresponding to the N value.

In one embodiment, the PPG signal receiver 101b can detect the PPG signal within the time D2 (the length of which may correspond to the M value) after the time point T3 as the second PPG signal S2. In another embodiment, if the PPG signal transmitter 101a and the receiver 101b are in a non-enabled state at the time point T1, the processor 104 may wait for the time D1 corresponding to the N value, and then at the time point T3 By sending enable signals to the PPG signal transmitter 101a and the receiver 101b, the PPG signal transmitter 101a is enabled to transmit the PPG signal and the receiver 101b is enabled to receive the PPG signal, and after the time point T3, the detection time D2 (the length of which may correspond to M value) within the PPG signal as the second PPG signal S2.

In FIG. 7 , assuming that the zero-crossing rate of the considered second PPG signal S2 is determined to be higher than the reference threshold value, the processor 104 may determine that the wearable device 100 is in the unworn state at time point T4 , and may accordingly The waveform 714 switches to a low level to indicate that the wearable device 100 is in an unworn state, but is not limited to this.

In one embodiment, after determining that the wearable device 100 is in the unworn state, the processor 104 may also control the PPG signal transceiver 101 to stop transmitting or receiving other PPG signals. In this way, the effect of power saving can be further achieved. In another embodiment, the processor 104 can control the PPG signal transceiver 101 to transmit or receive other PPG signals only when the wearable device 100 changes to a moving state to detect the wearable device 100 Whether to change to wearing state.

On the other hand, if the processor 104 determines in step S430 that the zero-crossing rate of the second PPG signal S2 is not higher than the reference threshold value TH, the processor 104 may continue to execute step S450 to determine that the wearable device 100 is in the wearing state. In other words, at this time, the wearable device 100 may be in a static state because the user is in a relatively static posture (such as watching TV, reading a book, sleeping or other wearing hands are still), rather than being taken off. stationary state. In this case, the wearable device 100 can reduce the behavior of detecting whether it is in an unworn state by transmitting/receiving PPG signals, thereby achieving the effect of power saving. In short, if the processor 104 has previously determined that the wearable device 100 is in the stationary state and the wearing state at the same time, and the wearable device 100 continues to be in the stationary state, the processor 104 may determine next time that the wearable device 100 is in the stationary state and When it is necessary to further determine whether it is in the wearing state, wait for a long time before controlling the PPG signal transmitter 101a and receiver 101b to transmit and detect the PPG signal, so as to achieve the effect of power saving. In another embodiment, the waiting time can be increased gradually, for example, the first waiting time is 3 seconds, the second waiting time is 30 seconds, and the third waiting time is 1 minute, in order to achieve the effect of saving power. . In another embodiment, in this case, the wearable device 100 can further determine what state the user is in at this time, such as a sleep state, and can adjust the transmission/reception of PPG signals according to the detected state. Measuring whether the device is in a non-wearing state can also save power.

In summary, in one embodiment, the processor 104 can achieve the above power saving effect by increasing N. For ease of understanding, the increased N will be expressed as N’ below. In detail, assuming that the processor 104 determines that the wearable device 100 is in a stationary state at the j-th (j is greater than i+N+M) time point, the processor 104 can control the PPG signal receiver 101b to detect a signal between the j-th and i+N+M time points. A plurality of PPG signals between the 'th time point and the j+N'+M time point are used as PPG signals for determining whether the wearable device 100 is in an unworn state.

That is, after determining that the wearable device 100 is in a stationary state at the j-th time point, the processor 104 can wait for N' time points and then control the PPG signal receiver 101b to detect the signal between the j+N'-th time point and A plurality of PPG signals between the j+N′+Mth time point are used as PPG signals for determining whether the wearable device 100 is in an unworn state.

On the contrary, if the processor 104 has previously determined that the wearable device 100 is in a moving state and an unworn state at the same time, and the wearable device 100 continues to be in a moving state, for example, the wearable device 100 is in a moving bag or a vehicle, then The processor 104 can wait for a longer time before controlling the PPG signal transmitter 101a and the receiver 101b to transmit and detect the PPG signal the next time it is determined that the wearable device 100 is in a moving state and it needs to be further determined whether the wearable device 100 is in a wearing state. , to achieve the effect of power saving. The waiting time can be extended by increasing N as described in the previous embodiment to achieve the above power saving effect. Similarly, the waiting time can also be increased gradually to achieve the effect of power saving.

The present invention also provides a computer-readable storage medium for executing the wear detection method. This computer-readable storage medium is composed of a plurality of program instructions (such as setup and deployment program instructions). These program instructions can be loaded into the wearable device 100 and executed to perform the above-mentioned wear detection method and the functions of the wearable device 100 .

In summary, embodiments of the present invention can detect the PPG signal after determining that the wearable device is in a stationary state, and determine whether the wearable device is in the wearing state or the non-wearing state based on the zero-crossing rate of the received PPG signal. In this way, embodiments of the present invention can achieve the technical effect of detecting whether the wearable device is being worn without being equipped with a proximity sensor dedicated to detecting the human body. In this way, the space of the wearable device can be used more efficiently, and the power consumption and implementation cost of the wearable device can be reduced at the same time.

Although the present invention has been disclosed above through embodiments, they are not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make some modifications and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the appended patent application scope.

100:Wearable devices 101:PPG signal transceiver 101a:PPG signal transmitter 101b:PPG signal receiver 102:Accelerometer 104: Processor 210:PPG signal waveform 210a, 210b, 210c, 511, 512, 711~714: waveform TH: reference threshold S1: first PPG signal S2: Second PPG signal T, T1, T3, T4: time points D1, D2: time S410~S450: steps

FIG. 1 is a schematic diagram of a wearable device according to an embodiment of the present invention. FIG. 2 is a schematic diagram of PPG signal changes based on FIG. 1 . FIG. 3 is a diagram illustrating activity count changes according to an embodiment of the present invention. FIG. 4 is a flow chart of a wear detection method according to an embodiment of the present invention. 5A and 5B are schematic diagrams of estimating the zero-crossing rate of a signal according to an embodiment of the present invention. FIG. 6 is a diagram illustrating the change of the zero-crossing rate of the PPG signal according to an embodiment of the present invention. FIG. 7 shows various waveform diagrams according to an embodiment of the present invention.

S410~S450: steps

Claims (17)

A wear detection method, suitable for a wearable device, including: in response to determining that the wearable device is in a stationary state, emitting a plurality of first light volume signals, and detecting a plurality of first light volume signals corresponding to the first light volume signals. a second light volume signal; obtaining a zero-crossing rate corresponding to the second light volume signals; in response to determining that the zero-crossing rate of the second light volume signals is higher than a reference threshold, determining that the wearable device is in an unworn state; and in response to determining that the zero-crossing rate of the second light volume signals is not higher than the reference threshold, it is determined that the wearable device is in a worn state; wherein the method of determining the reference threshold includes : Acquire a plurality of historical light volume signals, and estimate a reference zero-crossing rate based on the historical light volume signals, wherein the historical light volume signals are obtained when the wearable device is in a wearing state; and based on a correction factor The reference zero-crossing rate is corrected to the reference threshold value. The wear detection method of claim 1 further includes: detecting multiple acceleration values of the wearable device through an accelerometer of the wearable device, and determining a movement energy parameter of the wearable device based on this; In response to determining that the movement energy parameter is not higher than an energy threshold, it is determined that the wearable device exhibits the stationary state; and in response to determining that the movement energy parameter is higher than the energy threshold, it is determined that the wearable device exhibits a moving state. The wear detection method according to claim 1, wherein the step of detecting the second light volume signals corresponding to the first light volume signals includes: responding to determining that the wearable device appears at the i-th time point In this static state, a plurality of light volume signals between the i+N-th time point and the i+N+M-th time point are detected as the second light volume signals, where i is the index value, N, M is an integer. The wearing detection method as claimed in claim 3, further comprising: increasing N after the step of determining that the wearable device is in the wearing state. The wear detection method of claim 1, wherein the step of obtaining the zero-crossing rate corresponding to the second light volume signals includes: a first frequency estimate based on a sampling frequency and the second light volume signals Corresponding to the zero-crossing rate of the second light volume signals. The wear detection method as described in claim 5, wherein the zero-crossing rate corresponding to the second light volume signals is characterized by:

, where f ₁ is the first frequency of the second light volume signals, and f _s is the sampling frequency. The wear detection method of claim 1, wherein the reference threshold is adjusted according to the user's heart rate. The wearing detection method according to claim 1, wherein after the step of determining that the wearable device is in the unworn state, it further includes: stopping emitting or receiving other light volume signals. A wearable device including: An optical volumetric signal transceiver; a processor coupled to the optical volumetric signal transceiver, wherein: in response to the processor determining that the wearable device presents a stationary state, the processor controls the optical volumetric signal transceiver to emit A plurality of first light volume signals, and controls the light volume signal transceiver to detect a plurality of second light volume signals corresponding to the first light volume signals; the processor obtains a plurality of second light volume signals corresponding to the first light volume signals a zero-crossing rate; in response to the processor determining that the zero-crossing rate of the second light volume signals is higher than a reference threshold value, the processor determines that the wearable device is in an unworn state; and in response to determining that the If the zero-crossing rate of the second light volume signals is not higher than the reference threshold, it is determined that the wearable device is in a wearing state; wherein the method of determining the reference threshold includes: obtaining a plurality of historical light volume signals, and based on estimating a reference zero-crossing rate at a sampling frequency and a second frequency of the historical light volume signals, wherein the historical light volume signals are obtained when the wearable device is in a wearable state; and based on a correction factor, the The reference zero-crossing rate is corrected to the reference threshold value. The wearable device of claim 9, further comprising an accelerometer coupled to the processor for detecting a plurality of acceleration values of the wearable device, and the processor is configured to: based on these The acceleration value determines a movement energy parameter of the wearable device; In response to determining that the movement energy parameter is not higher than an energy threshold, it is determined that the wearable device exhibits the stationary state; and in response to determining that the movement energy parameter is higher than the energy threshold, it is determined that the wearable device exhibits a moving state. The wearable device of claim 9, wherein the processor is configured to: in response to determining that the wearable device exhibits the stationary state at the i-th time point, control the light volume signal transceiver to detect between the i-th time point and the i-th time point. Multiple light volume signals between the +N time point and the i+N+M time point are used as the second light volume signals, where i is the index value, and N and M are integers. The wearable device of claim 11, wherein the processor is further configured to increase N after determining that the wearable device is in the wearing state. The wearable device of claim 9, wherein the processor is configured to estimate the zero crossing corresponding to the second light volume signals based on a sampling frequency and a first frequency of the second light volume signals. Rate. The wearable device of claim 13, wherein the zero-crossing rate corresponding to the second light volume signals is characterized by:

, where f ₁ is the first frequency of the second light volume signals, and f _s is the sampling frequency. For the wearable device of claim 9, the reference threshold is adjusted according to the user's heart rate. The wearable device of claim 9, wherein after determining that the wearable device is in the unworn state, the processor is further configured to: control the light volume signal transceiver to stop transmitting or receiving other light volume signals. A computer-readable storage medium records an executable computer program. The executable computer program is loaded by a wearable device to perform the following steps: in response to determining that the wearable device is in a stationary state, emitting A plurality of first light volume signals, and detecting a plurality of second light volume signals corresponding to the first light volume signals; obtaining a zero-crossing rate corresponding to the second light volume signals; reacting to determining the The zero-crossing rate of the second photovolume signal is higher than a reference threshold, and the wearable device is determined to be in an unworn state; and in response to determining that the zero-crossing rate of the second photovolume signals is not higher than the reference threshold. value to determine that the wearable device is in a wearing state; wherein, the method of determining the reference threshold value includes: obtaining a plurality of historical light volume signals, and estimating a reference zero-crossing rate based on the historical light volume signals, wherein the historical light volume signals The light volume signal is obtained when the wearable device is in a wearing state; and the reference zero-crossing rate is corrected to the reference threshold based on a correction factor.

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