Power reduction in radar-based motion detection systems and methods

Abstract

Radar-based motion detection systems are widely used in smart homes, smart buildings, and smart city areas for automated control. This invention discloses methods, subsystems, systems, and computer programs for reducing radar sensor power by operating the radar sensor in a subsampling manner within a lighting control system. By combining information related to the lighting device's status and detection area, the radar sensor's sampling frequency is configured based on the user scenario. This achieves a balance between power reduction and motion detection performance.

Description

Technical Field

[0001] The present invention generally relates to a radar-based motion detection system for controlling, for example, lighting control. More particularly, various methods, subsystems, systems, and computer-readable media related to motion detection-based lighting control systems and methods are disclosed herein. Background Art

[0002] Mains standby power consumption is becoming an increasingly important feature for many products. Certain new products must comply with national and international standards and regulations regarding standby power requirements, which are becoming more stringent over time.

[0003] In lighting applications, the use of sensor systems for automated lighting control is becoming increasingly common, offering improved energy efficiency, user experience, and comfort. When a lighting device is in standby mode, the associated sensor system continues to operate, performing some control functions to detect certain events and activate the light. While in standby mode, the sensor system's power consumption contributes to the lighting device's mains standby power consumption.

[0004] Furthermore, there is a growing demand for adding more functionality to lighting devices. Some functions operate during both the lighting device's standby and active modes, such as the RF link for remote control and occupancy sensing. Currently, radar systems for occupancy detection are penetrating the market. One technique for reducing radar system power is power cycling, where the radar system's power is repeatedly turned on and off as much as possible. Radar sensor power consumption is reduced in part by reducing the duty cycle. The minimum duty cycle of a radar sensor is typically determined by the system's maximum response time requirements.

[0005] The Digital Addressable Lighting Interface (DALI) is a standard communication protocol and network-based system for lighting control. The DALI system is specified in technical standards IEC 62386 and IEC 60929. To cater to the application of the Internet of Things (IoT) in lighting, the DALI protocol is evolving. The new DALI sensor-ready (SR) interface, standardized by ANSI C137.4, integrates power supply to sensors connected to the bus while enabling digital bidirectional communication. However, the maximum supply current that can be drawn from the DALI bus is limited by the DALI SR specification, typically up to 250 mA. Therefore, when a sensor system is connected to a DALI SR interface, it approaches the mains power consumption. The total power consumption of a multi-sensor system is also limited by the DALI SR specification.

[0006] US2007052578A1 discloses a method for identifying moving objects by first transmitting a signal at a predetermined frequency. The unknown object reflects the signal, and the reflected signal is detected. The frequency of the reflected signal is modulated according to the movement of the unknown object. General features are extracted from the reflected signal, and a statistical classifier uses these features to identify the unknown object.

[0007] US2017353189A1 relates to a subsampling motion detector configured to detect motion information of a measured object, receive a first wireless radio frequency (RF) signal, and transmit a second wireless RF signal, the first wireless RF signal being generated by reflecting the second wireless RF signal from the object.

[0008] B. Jokanovic, MG Amin, YD Zhang, and F. Ahmad, “Multi-window time-frequency feature reconstruction from undersampled continuous wave radar measurements for fall detection,” IET Radar, Sonar & Navigation, vol. 9, No. 2, pp. 173-183, 2015: A hybrid approach for fall detection and classification based on compressed sensing and multi-window analysis using Slepian or Hermite functions in the presence of full data or compressed observations is disclosed. Summary of the Invention

[0009] In light of the foregoing, the present disclosure is directed to methods, subsystems, systems, computer programs, and computer-readable media for further reducing the power consumption of a radar sensor subsystem through subsampling in lighting control scenarios. More specifically, various computer-readable media (transitory and non-transitory), methods, systems, and subsystems are provided to reduce the sampling frequency of a radar sensor to a level sufficient to meet application requirements related to the corresponding state of a lighting device.

[0010] Radar is a well-known detection system that uses radio waves to determine the distance, angle, or speed of moving objects. A radar system operates by radiating energy into space and monitoring for echoes or reflected signals from objects in the surrounding area or within the detection zone. Typically, a radar system has a transmitter that transmits radio waves, or radar signals, into space in a predetermined direction. When radar signals strike an object, they are typically reflected or scattered in a variety of directions, depending on the object's material and surface, as well as the angle at which the radar signal is injected. Some of the radar signal penetrates the target or is absorbed to a certain degree by the target. Some of the radar signal reflected back to the radar system is captured by the radar system's receiver and is the desired signal that enables the radar system to operate. If an object moves toward or away from the transmitter within the detection zone, the Doppler effect causes a corresponding shift in the frequency of the reflected radio waves. In a simple example, by comparing the frequency shift between the transmitted signal and the received echo from the detection zone, the radar system can derive the relative speed between the radar system and the moving object based on the Doppler effect. In addition to speed measurements, the distance to the moving target and the direction of the moving target can also be derived. Depending on the operating mechanism, different methods can be used to derive specific types of information. For pulse radars, distance measurements can be based on the time-of-flight principle, while for continuous wave radars, the frequency shift of the received signal compared to the transmitted signal is proportional to the distance traveled. The heading of a moving target relative to the radar sensor can be derived by employing a specific type of antenna or antenna array.

[0011] In a more realistic scenario, the echoes received by a radar system can be a jumble of signals generated by more than one moving object. Furthermore, due to the different surfaces of the multiple moving objects and the different injection angles of the signal transmitted from the radar system relative to each of the multiple objects, the echoes captured by the radar system are a mixture of directly reflected signals as well as scattered signals that can propagate along several surfaces of a stationary object or another moving object to bounce back to the radar system. The different echoes are constructively or destructively combined at the radar system's receiver antenna. Consequently, signal processing in the radar system can be quite complex and also consumes power.

[0012] One of the modern uses of radar systems, radar-based presence detection is widely used for automated control in smart buildings and smart cities. Presence detection can be as simple as providing binary information indicating the presence of a person or moving object in the detection area. It can also be more complex, providing detailed motion information such as the number of objects in the detection area, their locations, and their trajectories, and even involving coarse or fine classification of motion.

[0013] In lighting control environments, more advanced radar sensing capabilities are desirable, but this can conflict with power consumption requirements. Therefore, the present invention aims to reduce radar sensor power consumption by operating the sensor in subsampling mode when possible, and adapting the sampling frequency to the state of the lighting device and the application scenario.

[0014] For ease of description, two operating states are defined for lighting devices: standby mode and active mode. The standby mode of a lighting device includes situations where the light is off or at a minimum dimming level (e.g., ≤10%). The active mode of a lighting device includes situations where the light is at full output or dimmed (with a dimming level >10%). However, this definition is for illustrative purposes only and does not exclude other possibilities for setting different dimming levels to distinguish between states, such as setting the minimum dimming level to 5% or 15%.

[0015] According to a first aspect of the present invention, a subsystem for controlling illumination of a lighting device via motion detection is provided, the subsystem comprising: a radar sensor configured to detect motion in a detection area by sampling a derived signal from the detection area at a sampling frequency; a controller communicatively coupled to the radar sensor and the lighting device, the controller configured to, when the lighting device is in a standby mode, set the sampling frequency of the radar sensor to an initial value lower than twice a first Nyquist frequency, and to control the lighting device based on sensor data obtained by the radar sensor at the specified sampling frequency; and wherein when the lighting device is in the standby mode, the first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area.

[0016] As described above, regarding the radar system's operating principle, the radar sensor operates by comparing the frequency shift between the transmitted signal and the received echo from the detection zone. As described in the patent claims, the derived signal from the detection zone is down-converted by mixing the reflected signal from the detection zone with the original transmitted radar signal known to the radar sensor. The derived signal thus corresponds to the baseband signal in the radar sensor, ready for sampling by an analog-to-digital converter (ADC).

[0017] In a typical digital signal processing system, according to the Nyquist sampling criterion, to reconstruct the original signal, the ADC sampling frequency must be at least twice the Nyquist frequency. The power consumption of the ADC and subsequent digital processing circuits is proportional to the sampling frequency.

[0018] Advantageously, by setting the sampling frequency to an initial value below twice the first Nyquist frequency, the radar sensor's power consumption is reduced by operating in subsampling mode. The trade-off is that aliasing may occur due to subsampling, which can cause signal distortion.

[0019] For Doppler radar, the signal bandwidth of the baseband signal is equivalent to the Doppler shift. Although accurately deriving the actual Doppler shift can be quite complex—depending on many factors related to the moving object and the environment—it is possible to make a rule of thumb for estimating the maximum Doppler shift based on the detection area and the type of motion to be detected within it.

[0020] Advantageously, the first Nyquist frequency applies not only to the detection zone, but also to the state of the lighting device. For example, in an indoor environment, when a light is in standby mode, it typically indicates the absence of people in the area. Therefore, when the lighting device is in standby mode, the first motion detected by the radar sensor is often large movement, such as a person entering the room. In contrast, when the lighting device is in active mode, which typically indicates the presence of a person in the room, the radar sensor may only detect minor movements, such as typing on a keyboard or making a phone call. Because the Doppler shifts caused by large and minor movements can vary significantly, by considering the lighting device's state and detection zone, a more accurate estimate of the first Nyquist frequency can be made based on the motion being detected. This reduces the chance of setting the sampling frequency unnecessarily high, resulting in excessive power consumption.

[0021] Furthermore, when a lighting device is in standby mode, detecting any motion in the detection area is more important than deriving detailed motion information to enable the light in a timely manner. Therefore, the radar sensor is limited to providing basic binary presence detection. The radar sensor processes binary presence detection similarly to a baseband energy detector, and thus, the distortion caused by Doppler shift due to subsampling does not degrade system performance. Operating in subsampling mode, where the sampling frequency is less than twice the first Nyquist frequency, can significantly reduce the radar's power consumption, a highly advantageous feature for lighting control in standby mode.

[0022] Advantageously, motion detection can be accomplished by processing a signal sampled at a sampling frequency and obtained from a radar sensor, wherein the radar sensor samples a signal derived from the detection area at the sampling frequency. The processed signal is provided as sensor data for further control purposes.

[0023] Preferably, the subsystem is included in the luminaire and is communicatively coupled to the radar sensor and the controller of the lighting device for controlling both motion detection and illumination. In one example, the lamp / luminaire may include an integrated radar sensor in the same housing as the lighting device.

[0024] Alternatively, the subsystem is not included in the luminaire, and the radar sensor, lighting fixture, and controller are physically distributed. Via a controller communicatively coupled to both the radar sensor and the lighting fixture, sensor data from the radar sensor and status information from the lighting fixture can be exchanged with each other via the controller. Thus, the lighting fixture can have a separate local controller for lighting control, while the radar sensor can have a separate processor for local signal processing. In this sense, control of both motion detection and lighting is distributed between the controller included in the subsystem and a separate local controller or processor.

[0025] Advantageously, the initial value of the sampling frequency is set to be lower than the first Nyquist frequency.

[0026] Since the power consumption of a radar sensor varies with the sampling frequency, and binary presence detection is less susceptible to distortion caused by aliasing when the light is in standby mode, it is desirable to further reduce the sampling frequency below the first Nyquist frequency in a deep subsampling mode where even more energy is saved.

[0027] In one embodiment, the controller is further configured to generate a control signal to trigger the lighting device to change from the standby mode to the active mode when motion is detected from the sensor data obtained by the radar sensor.

[0028] Motion can be confirmed by detecting the Doppler shift of the reflection from the detection area compared to the originally transmitted radar signal. In binary presence detection, if energy is detected within the baseband bandwidth, this also confirms presence in the detection area. This processing can be performed in the radar sensor's own local processor. If the radar sensor does not include a local processor, or if it is determined that performing the calculations in a subsystem controller is more efficient, it can also be performed in the subsystem controller. A control signal is generated based on the confirmation of presence detection, thereby triggering a state change of the lighting device from standby mode to active mode.

[0029] Preferably, the subsystem includes a wireless transceiver, and the wireless transceiver is configured to wirelessly transmit the sensor data and / or the control signal to at least one of a lighting device, a remote control device, and an intelligent electronic device belonging to the user.

[0030] When the subsystem is distributed and the radar sensor, controller, and lighting fixtures are not co-located in a single luminaire, using a wireless transceiver to achieve connectivity is advantageous. Preferably, the sensor data from the radar sensor and the control signals it generates can also be wirelessly shared with a remote control device for other control purposes beyond lighting control, such as controlling access, HVAC, blinds, and so on. The same sensor data and control signals can also be shared remotely with users via smart electronic devices (such as smartphones or wearable devices with wireless communication capabilities). For example, a homeowner can obtain real-time occupancy or intrusion information for their home while at work or traveling.

[0031] Alternatively, when mobility is less critical, the connection can also be realized via a wired link. For example, the controller is connected to the lighting device via a cable or a bus.

[0032] In another embodiment, the controller is further configured to, when the lighting device is in the activation mode, determine the operating mode of the radar sensor as a normal operating mode or a power saving mode based on a power supply condition, and when the lighting device is in the activation mode, set the sampling frequency of the radar sensor to: for the normal operating mode, at least twice the second Nyquist frequency, and for the power saving mode, less than twice the second Nyquist frequency, and wherein when the lighting device is in the activation mode, the second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area.

[0033] As disclosed above, adjusting the Nyquist frequency based on the combination of the lighting device's state and detection zone is beneficial. Assuming that when the lighting device is in active mode, most of the time only small motions with small amplitudes occur. To detect these signals, the sampling frequency should be increased to achieve a better signal-to-noise ratio. The selection of the second estimated Nyquist Doppler frequency is also a design trade-off between power consumption and motion detection performance. Given the potentially different power consumption requirements when the lighting device is in active or standby mode, it is also beneficial to decouple the radar sensor's sampling frequency setting when the lighting device is in different states.

[0034] Preferably, when the lighting device is in active mode, the radar sensor operates in normal operating mode by setting the sampling frequency to be higher than twice the second Nyquist frequency. If the lighting device is in active mode, it usually indicates that there is a person in the illuminated area and more advanced presence detection may be required. In this sense, it becomes more important to derive the correct Doppler shift of the motion involved in order to implement further radar processing. Therefore, the radar sensor no longer operates in subsampling mode. Moreover, when the lighting device is in active mode, the power consumption requirements of the radar sensor are less critical, considering its contribution to the overall system. In some scenarios, when the power consumption of the radar sensor is no longer critical, the sampling frequency can even be several times higher than the second Nyquist sampling frequency, and thus motion detection can benefit from the oversampling gain.

[0035] However, when the radar sensor is powered by the DALI SR interface and shares the same bus with several other sensors, it may still be desirable to keep the radar sensor in power saving mode. In this case, in subsampling mode, the radar sensor's sampling frequency will be lower than twice the second Nyquist frequency. The sampling frequency can then be set slightly lower than twice the second Nyquist frequency, or even lower than twice the second Nyquist frequency, to suit actual power supply conditions.

[0036] Advantageously, the controller is further configured to: derive detailed motion information via Doppler analysis based on samples of sensor data obtained by the radar sensor when motion is detected, and wherein the detailed motion information includes at least one of: the number of motion sources, the direction of movement of the motion sources relative to the radar sensor, the speed of the motion, and the classification of the motion; and control the lighting device in a more advanced mode according to the detailed motion information.

[0037] Utilizing detailed motion detection based on Doppler or micro-Doppler analysis, more complex presence information can be derived. This detailed motion information can enrich lighting control to a more advanced level, enabling the lighting device to switch to a specific scene based on motion classification. For example, if motion detection indicates that a person is lying on a couch, the controller can send a control signal to trigger the lighting device to switch to a relaxing scene. In another example, if motion detection indicates that the person is playing a video game, the controller can send another control signal to trigger the lighting device to switch to a stimulating scene by manipulating the light spectrum in a different manner.

[0038] To avoid unnecessary power consumption on radar processing, detailed motion information can be derived only for one or more major motion sources, which in practice are also the main factors in determining the lighting scene.

[0039] The invention also discloses that when the radar sensor detects no motion after a first predefined time period, the controller is further configured to generate another control signal to trigger the lighting device to change from the active mode to the standby mode. The first predefined time period can be determined based on energy conservation requirements in a green building environment or based on specific expectations for user experience.

[0040] Detailed motion information can also be sent to a remote control device for other control purposes, or to an intelligent electronic device belonging to the user for more advanced monitoring.

[0041] In one embodiment, the radar sensor further includes an analog front end (AFE) arranged to be powered on and off separately from the rest of the radar sensor; and the controller is further configured to control power cycling of the AFE of the radar sensor at the same frequency as the sampling frequency by turning on the AFE before a sampling instant at which the radar sensor performs sampling and turning off the AFE once sampling is performed.

[0042] Advantageously, subsampling can be combined with other radar sensor power-saving techniques, such as power cycling. To ensure stable sampling operation of the radar sensor, the radar sensor's AFE can be duty-cycled, where a clock operates at the same frequency as the sampling clock, but with a slight phase shift.

[0043] In one embodiment, a system for controlling lighting via motion detection comprises: a subsystem according to the first aspect; wherein the subsystem is configured to generate a control signal to: trigger a lighting device to change from a standby mode to an active mode when motion is detected, and to trigger the lighting device to change from the active mode to the standby mode when no motion is detected after a first predefined time period.

[0044] Preferably, the system also includes a remote control device or intelligent electronic device belonging to the user. Sensor data and / or control signals can also be sent to the remote control device or intelligent electronic device belonging to the user for control or monitoring purposes other than pure lighting control. In another example, other sensors may be collocated with the remote control device or intelligent electronic device belonging to the user. Thus, the radar sensor and other sensors included in the subsystem can remotely cooperate or coordinate by sharing sensory data from different modalities.

[0045] It is also disclosed that the system includes another lighting device. The subsystem is used to collectively control more than one lighting device in the system.

[0046] According to a first aspect of the present invention, there is provided a method for controlling illumination of a lighting device via motion detection, the method comprising: detecting motion in a detection area by a radar sensor, the radar sensor sampling a derived signal from the detection area at a sampling frequency; when the lighting device is in a standby mode, setting the sampling frequency of the radar sensor to an initial value lower than twice a first Nyquist frequency, and wherein the first Nyquist frequency is equal to a first estimated maximum Doppler frequency of motion that the radar sensor will detect in the detection area when the lighting device is in the standby mode; and controlling the lighting device based on sensor data obtained by the radar sensor at a specified sampling frequency.

[0047] Preferably, the method further comprises detecting motion by processing a signal obtained from a radar sensor sampled at a sampling frequency, wherein the radar sensor samples a signal derived from the detection area at the sampling frequency. The processed signal is provided as sensor data for control purposes.

[0048] Advantageously, the method further comprises setting the initial value of the sampling frequency to be lower than the first Nyquist frequency.

[0049] In one embodiment, the method further comprises generating a control signal to trigger the lighting device to change from the standby mode to the active mode when motion is detected from the sensor data obtained by the radar sensor.

[0050] In another embodiment, the method further includes: when the lighting device is in standby mode, setting the sampling frequency of the radar sensor to a value increased compared to an initial value when motion is detected from sensor data obtained by the radar sensor; when detection of motion is confirmed from a new sensor data set obtained by the radar sensor operating at the increased value of the sampling frequency, generating a control signal to trigger the lighting device to change from the standby mode to the active mode; and when detection of motion is not confirmed from the new sensor data set obtained by the radar sensor operating at the increased value of the sampling frequency, setting the sampling frequency back to the initial value.

[0051] When the radar sensor operates in deep subsampling mode, the false alarm rate may increase. When the lighting device is turned on due to a false alarm decision regarding motion detection, it also introduces undesirable power consumption to the system. Therefore, it is preferable to use further steps to reduce the possibility of false alarms. After detecting motion from sensor data obtained by the radar sensor operating at the sampling frequency of the initial value, the controller sets the sampling frequency of the radar sensor to an increased value. If motion is confirmed by the new sensor data set obtained by the radar sensor operating at the sampling frequency of the increased value, a control signal is generated to trigger a state change of the lighting device; otherwise, the controller will determine that it is a false alarm and reset the sampling frequency of the radar sensor back to the initial value to save power.

[0052] Advantageously, the method further comprises: when the lighting device is in the standby mode, sweeping the sampling frequency to several different discrete sampling frequencies lower than twice the first Nyquist frequency, and setting the sampling frequency to each of the several different discrete sampling frequencies within a second predefined time period to enable the radar sensor to perform stable detection; and recovering the motion-related Doppler frequency signal from aliasing by comparing sub-sampled output sets of sensor data obtained by sampling the radar sensor at each of the several different discrete sampling frequencies.

[0053] Although in most cases only binary presence detection is expected for radar sensors operating in subsampling mode, it is sometimes desirable to derive additional information from subsampling radar, such as motion velocity, number of moving sources, and so on. By sweeping the sampling frequency to several different discrete sampling frequencies below twice the first Nyquist frequency and comparing the subsampled outputs of sensor data sampled at each of the several different discrete sampling frequencies, it is still possible to recover the motion-related Doppler frequency signal from aliasing. This approach can sometimes take longer to derive the desired signal and therefore represents a trade-off between latency and power consumption.

[0054] In one embodiment, the method further includes: when the lighting device is in the activation mode, determining the operating mode of the radar sensor to be a normal operating mode or a power saving mode according to a power supply condition; when the lighting device is in the activation mode, setting the sampling frequency of the radar sensor to: for the normal operating mode, at least twice the second Nyquist frequency, and for the power saving mode, less than twice the second Nyquist frequency, and wherein when the lighting device is in the activation mode, the second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area.

[0055] Preferably, the method further includes: deriving detailed motion information via Doppler analysis based on a sampled output of sensor data obtained by a radar sensor when motion is detected, and wherein the detailed motion information includes at least one of the following: the number of motion sources, the direction of movement of the motion sources relative to the radar sensor, the speed of the motion, and the classification of the motion; and controlling the lighting device in a more advanced mode according to the detailed motion information.

[0056] It is also disclosed that the method may further comprise the step of: when the lighting device is in the active mode, when the radar sensor detects no motion after a first predefined time period, generating another control signal to trigger the lighting device to change from the active mode to the standby mode.

[0057] The invention may also be embodied in a computer program or a computer program product comprising code means for causing a computer to carry out the above-described method for controlling a subsystem of lighting via motion detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In the drawings, like reference numerals are used throughout the different views. Figure 1 Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0059] Figure 1 An illustrative lighting control system based on motion detection is shown;

[0060] Figure 2 schematically depicts example components of a subsystem for controlling lighting via motion detection as disclosed herein;

[0061] Figure 3 The setting of the sampling frequency is shown to satisfy the Nyquist sampling criterion for a given set of signals;

[0062] Figure 4 shows the setting of sampling frequency in subsampling mode;

[0063] Figure 5 Power cycle control is shown;

[0064] Figure 6 A system for controlling lighting via motion detection is shown;

[0065] Figure 7 A flow chart illustrating a method for controlling lighting via motion detection is shown;

[0066] Figure 8 A flow chart of a method for controlling lighting via motion detection is shown, wherein false alarms are prevented. DETAILED DESCRIPTION

[0067] Implementing radar-based motion detection systems for automated control is desirable for many control systems in diverse scenarios, such as smart homes, smart buildings, and smart cities. Automatic control based on motion or presence detection makes the interaction between humans and their surroundings more intuitive and spontaneous. Certain products, such as lighting fixtures, may be subject to increasingly stringent standby power consumption regulations. Because sensor systems also operate during the lighting fixture's standby state, the sensor system's power consumption directly contributes to the lighting fixture's standby power consumption. Therefore, reducing the sensor system's power consumption without compromising control functionality is crucial.

[0068] Figure 1An example of a motion detection-based lighting control system is shown, which includes the disclosed subsystem 100, as well as at least one lighting device 300', 300", a remote control device 320, and an intelligent electronic device 330 belonging to a user. When a person enters the detection area, the radar sensor included in the subsystem 100 will detect the motion, and the subsystem can then share the sensor data and / or control signals derived from the sensor data with several nearby devices, such as the lighting devices 300', 300" and the remote control device 320. It is also possible for the subsystem to share the sensor data and / or control signals with remote intelligent electronic devices via a network.

[0069] Lighting devices 300', 300" can be co-located with subsystem 100, such as in the same room or in close proximity, and can be communicatively coupled to the subsystem via wired or wireless communication. The subsystem also wirelessly communicates with a remote control device, which can be used for other control purposes beyond lighting, such as controlling access, HVAC, blinds, and so on. The same sensor data and control signals can also be shared remotely with users via smart electronic devices (such as smartphones or wearable devices with wireless communication capabilities). For example, a homeowner can obtain real-time occupancy or intrusion information about their home while at work or traveling.

[0070] Figure 2 Schematically depicted are example components of such a subsystem 100 for controlling lighting via motion detection as disclosed herein. Subsystem 100 includes at least a radar sensor 200, a lighting device 300, and a controller 400. The controller is communicatively coupled to the radar sensor and the lighting device. Utilizing knowledge of the detection area and feedback from the lighting device regarding light status, the controller is configured to set the sampling frequency of the radar sensor to an initial value less than twice the first Nyquist frequency when the lighting device is in standby mode. The controller is then further configured to control the lighting device based on sensor data obtained by the radar sensor at the specified sampling frequency. When the lighting device is in standby mode, the first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area. Thus, when the lighting device is in the reduced-power standby mode, the radar sensor is operating in a subsampling mode.

[0071] In order to better understand the concept of sampling in digital signal processing, Figure 3 The sampling frequency is set to meet the Nyquist sampling criterion for a given set of signals. In this example, the signal set is band-limited and its frequency content is concentrated around f BW According to the Nyquist sampling criterion, to avoid folding or aliasing, half of the sampling rate Fs / 2 should not be less than the signal bandwidth f BWBy definition, half the sampling rate, Fs / 2, is also called the Nyquist frequency, F Ny Therefore, in order to prevent aliasing, the sampling frequency is usually based on F s = 2F Ny and F Ny ≥ f BW set up.

[0072] Figure 4 shows the setting of sampling frequency in subsampling mode. Here, F Ny = f BW and F s < 2F Ny The power consumption of the ADC and subsequent digital processing circuits is proportional to the sampling frequency. Therefore, by operating in subsampling mode, the power consumption of the radar sensor is reduced accordingly.

[0073] Therefore, to configure a radar sensor for subsampling mode, the first step is to estimate the potential bandwidth of the signal. For Doppler radars used for motion detection in this context, the signal bandwidth of the baseband signal is equivalent to the potential Doppler shift to be detected. While accurately deriving the actual Doppler shift can be quite complex—depending on many factors related to the moving object and the environment—a rule of thumb for estimating the maximum Doppler shift can be developed based on the detection area and the type of motion to be detected within that area. For example, for indoor environments, it is generally assumed that the maximum walking speed of a person is less than 3 m / s, or 10.8 km / h. For outdoor environments, depending on the detection area, a typical maximum speed limit for vehicles might be 130 km / h on a highway or 50 km / h on a residential road. Knowing the maximum speed of the motion to be detected within a given detection area, given the carrier frequency of the radar signal transmitted by the radar sensor and the Doppler shift principle, the subsystem can estimate the maximum Doppler shift of the motion to be detected within the detection area.

[0074] As an example, a 24 GHz Doppler radar is deployed to detect motion in an indoor environment. We can estimate the maximum Doppler shift detected by the radar sensor based on the following parameters:

[0075] Maximum speed of movement,

[0076] Here a person's maximum indoor leisure walking speed (△v max ): 3m / s,

[0077] Carrier frequency of the radar signal (f0): 24 GHz, and

[0078] Speed ​​of light (c): 3e8 m / s.

[0079] Using these parameters, we can calculate the maximum Doppler shift:

[0080] (Equation 1).

[0081] Incorporating the light's state allows for a more precise estimate of the maximum Doppler shift. Often, the light's state (active or standby) also indicates whether someone is present in the area. Therefore, when a lighting device is in standby mode, the first motion detected by the radar sensor is typically large, such as a person walking into the room. In contrast, when a lighting device is in active mode, which often indicates the presence of someone in the room, the radar sensor may only detect subtle movements, such as typing on a keyboard or making a phone call, at an instantaneous velocity that can even exceed large body movements. Because the Doppler shift and amplitude of echoes generated by large and subtle movements can exhibit very different behavior, linking the lighting device's state to the detection zone allows for a more precise estimate of the first Nyquist frequency. This reduces the chance of setting the sampling frequency unnecessarily high, thus avoiding excessive power consumption.

[0082] Figure 5 As a common power saving technology, power cycle control is also widely used in radar detection systems. The entire system is alternately turned on and off, and the entire cycle T cycle Compared to the on-period T on As small as possible, for power reduction. on and T cycle The ratio between the sampling clock and the sampling clock is called the duty cycle. Subsampling can be combined with other radar sensor power-saving techniques, such as power cycling. To ensure stable sampling operation of the radar sensor, the radar sensor's AFE can be duty-cycled, where the clock operates at the same frequency as the sampling clock, but with a slight phase shift.

[0083] Here is an example of how this can be implemented. The subsystem or radar sensor also includes a clock generation system. The clock generation system generates a sampling clock or first clock according to a sampling frequency as specified by the controller. For power cycling of the AFE of the radar sensor, the clock generation system can generate another clock from the first clock previously used to control the sampling frequency of the radar sensor, and the other clock operates at the same frequency as the sampling frequency, but with a phase delay, and wherein the phase delay ensures that the AFE portion of the radar sensor is stable and ready for sampling. The newly generated another clock is applied to control the sampling frequency of the radar sensor; and the controller is further configured to power cycle the AFE of the radar sensor with the first clock. Note that the phase of the first clock is earlier than that of the other clock. In addition, the on-period T of the AFE onIt should be long enough to allow the signal from the analog front end section to be properly sampled in the ADC.

[0084] The combination of subsampling operation of the radar sensor and power cycling of the AFE provides further power reduction compared to using either technique alone.

[0085] Figure 6 A system for controlling lighting via motion detection is shown. Subsystem 100 is configured to generate a control signal to control a state change of a lighting device, such that the light turns on when motion is detected and turns off when no motion is detected after a first predefined time period. The first predefined time period can be configured to be relatively long or short, depending on the trade-off between system energy efficiency and user experience. If the first predefined time period is set too short, this may be very effective from an energy-saving perspective, but it may result in a very poor user experience, where the light turns off because the user is sitting still for a while.

[0086] As already disclosed above, the system may also include a remote control device or smart electronic device belonging to the user. For different use cases, the same information related to motion detection can be shared wirelessly to those remote devices. Different radio transceivers compliant with different communication standards can be deployed in both indoor and / or outdoor applications to implement such wireless links, such as 3G / 4G / 5G cellular, WiFi, Zigbee, BLE, Zwave, Thread, etc. In another example, the system may further include another lighting device, or even more than one other lighting device. These lighting devices are controlled in a collective manner. Using radar sensors in one subsystem and sharing the same motion detection information to control different products in the vicinity (directly through the subsystem or via a remote control device) can be a more cost-effective way to implement building automation.

[0087] Figure 7 A flowchart illustrating a method implemented by a subsystem for controlling lighting via motion detection is provided. In step S601, radar sensor 200 included in the subsystem is configured to detect motion in a detection area by sampling a derived signal from the detection area at a sampling frequency. Furthermore, in step S602, a controller included in the subsystem is configured to set the radar sensor's sampling frequency to an initial value less than twice the first Nyquist frequency when the lighting device is in standby mode, where the first Nyquist frequency is equal to a first estimated maximum Doppler frequency of motion that radar sensor 200 will detect in the detection area when the lighting device 300 is in standby mode. In step S603, the controller is further configured to control the lighting device 300 based on sensor data obtained by radar sensor 200 at a specified sampling frequency.

[0088] When the controller detects motion from the sensor data obtained by the radar sensor in step S604 , it generates a control signal to trigger the lighting device 300 to change from the standby mode to the active mode in step S607 .

[0089] When the radar sensor operates in deep subsampling mode, binary presence information is derived using a method similar to energy detection—that is, by detecting energy in the derived signal above a certain threshold, rather than retrieving raw Doppler shift information. Consequently, the false alarm rate may increase compared to normal operation. If lighting devices are turned on due to a false positive decision regarding motion detection, this can also introduce undesirable power consumption in the system. Therefore, additional steps are disclosed to reduce the likelihood of false alarms. Figure 8 A flow chart of a method for controlling lighting via motion detection is shown, wherein false alarms are prevented.

[0090] Instead of immediately generating a control signal when motion is detected in step S604, the controller sets the radar sensor's sampling frequency to an increased value compared to the initial value in step S605. If the new sensor data set obtained by the radar sensor operating at the increased sampling frequency confirms motion in step S606, a control signal is generated in step S607 to trigger a state change of the lighting device. Otherwise, the controller determines that it is a false alarm and resets the radar sensor's sampling frequency back to the initial value in step S602 to save power.

[0091] While in most cases only binary presence detection is desired for radar sensors operating in subsampling mode, where the sampling frequency is less than twice the Nyquist frequency, it is sometimes desirable to still derive some more detailed motion information from the subsampling radar, such as motion velocity, number of moving sources, and so on. By sweeping the sampling frequency to several different discrete sampling frequencies below twice the first Nyquist frequency and comparing the subsampled outputs of sensor data sampled at each of the several different discrete sampling frequencies, the motion-related Doppler frequency signal can still be recovered from aliasing. Of course, this approach will take longer to derive the desired signal, and thus results in a trade-off between latency and power consumption.

[0092] For the practical example of detecting tones above, assume that the highest frequency tone is at 350 Hz or f BW = 350 Hz, and there are two discrete sampling frequencies set to F s1 = 270 Hz and F s2 = 330 Hz. Depending on the operation of the Fourier transform (FT) and the sampling system, the actual tone of 350 Hz will appear at different locations after sampling. s1= 270 Hz, the actual tone of 350 Hz will appear at |F s1 -f BW | = 80 Hz. And at F s2 = 330 Hz, the actual tone of 350 Hz will appear at |F s2 -f BW | = 20 Hz. Therefore, by scanning a set of discrete sampling frequencies in the sub-sampling region, further processing can be used to distinguish the original frequency bins from the image frequencies, or to recover the original signal.

[0093] The method may further include the following steps: when the lighting device is in active mode, determining the operating mode of the radar sensor as a normal operating mode or a power saving mode based on power supply conditions. Depending on the power supply conditions—such as whether it is powered by a DALI SR interface or applies very strict power regulation—the controller may determine the operating mode of the radar sensor. Furthermore, when the lighting device is in active mode, the sampling frequency of the radar sensor is set to at least twice the second Nyquist frequency for normal operating mode or less than twice the second Nyquist frequency for power saving mode, with the second Nyquist frequency being set to a second estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area when the lighting device is in active mode.

[0094] Therefore, in a preferred configuration, the radar sensor operates in normal mode, where the sampling frequency satisfies the Nyquist sampling criterion. This allows for more reliable motion detection and greater detail. When power conservation is less critical than for more advanced motion detection-based functions, the radar sensor can even operate in oversampling mode, where the sampling frequency is significantly higher than twice the Nyquist sampling frequency.

[0095] Using detailed motion detection based on Doppler or micro-Doppler analysis, more complex presence information can be derived. This detailed motion information can enrich lighting control to a more advanced level, such as switching the lighting device to a specific lighting scene based on motion classification. For example, if motion detection indicates that a person is lying on a couch, the controller can send a control signal to trigger the lighting device to switch to a relaxing scene. In another example, if motion detection indicates that the person is playing a video game, the controller can send another control signal to trigger the lighting device to switch to a stimulating scene by manipulating the light spectrum for more advanced lighting control.

[0096] When a radar sensor is powered by a DALI SR interface and shares the same bus with several other sensors, it may be desirable to keep the radar sensor in power saving mode. In this case, in subsampling mode, the radar sensor's sampling frequency will be lower than twice the second Nyquist frequency. The sampling frequency can then be set slightly lower than twice the second Nyquist frequency, or even lower than twice the second Nyquist frequency, to suit actual power supply conditions.

[0097] In some cases, the second Nyquist frequency may have the same value as the first Nyquist frequency, depending on the expected motion to be detected when the lighting device is in the standby mode and the active mode.

[0098] The method according to the invention can be implemented on a computer as a computer-implemented method, on a general purpose signal processor using multiple processing units, or in dedicated hardware such as an FPGA or ASIC, or in a combination of both.

[0099] The executable code of the method according to the present invention may be stored on a computer program product. Examples of computer program products include a memory device, an optical storage device, an integrated circuit, a server, online software, etc. Preferably, the computer program product comprises non-transitory program code means stored on a computer-readable medium for performing the method according to the present invention when the program product is executed on a computer.

[0100] In a preferred example, the computer program comprises computer program code means adapted to perform the steps of the method according to the invention when the computer program is run on a computer.Preferably, the computer program is embodied on a computer readable medium.

[0101] Methods, systems, and computer-readable media (transitory and non-transitory) may also be provided for implementing selected aspects of the above-described embodiments.

[0102] The term "controller" is used generally herein to describe various devices or subsystems associated with, among other functions, the operation of one or more light sources. A controller can be implemented in a variety of ways (e.g., such as with dedicated hardware) to perform the various functions discussed herein. A "processor" is an example of a controller that employs one or more microprocessors that can be programmed using software (e.g., microcode) to perform the various functions discussed herein. A controller can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0103] In various embodiments, a processor or controller may be associated with one or more storage media (collectively referred to herein as "memory," e.g., volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM, floppy disks, compact disks, optical disks, magnetic tape, etc.). In some embodiments, the storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform at least some of the functions discussed herein. The various storage media may be fixed within the processor or controller, or may be transportable such that the one or more programs stored thereon can be loaded into the processor or controller in order to implement various aspects of the invention discussed herein. The terms "program" or "computer program" are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be used to program one or more processors or controllers.

[0104] As used herein, the term "network" refers to any interconnection of two or more devices (including controllers or processors) that facilitates the transfer of information (e.g., for device control, data storage, data exchange, etc.) between any two or more devices and / or between multiple devices coupled to the network. Furthermore, it should be readily appreciated that the various device networks discussed herein may employ one or more wireless and / or wired / cable links to facilitate the transfer of information throughout the network.

[0105] Unless explicitly indicated to the contrary, the indefinite articles "a" and "an" as used herein in the specification and claims should be understood to mean "at least one."

[0106] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, i.e., including at least one of a plurality of elements or a list of elements, but also including more than one of a plurality of elements or a list of elements, and optionally, additional unlisted items. Only terms that clearly indicate the contrary, such as "only one of" or "exactly one of," or, when used in a claim, "consisting of," will refer to including exactly one element of a plurality of elements or a list of elements. Generally speaking, the term "or," as used herein, should only be interpreted to indicate exclusive alternatives (i.e., "one or the other, but not both") when preceded by an exclusive term such as "either," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in a claim, should have its ordinary meaning as used in the art of patent law.

[0107] As used herein in the specification and in the claims, the phrase "at least one" referring to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements and does not exclude any combination of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to those specifically identified elements.

[0108] It should also be understood that, unless explicitly indicated to the contrary, in any method claimed herein that includes more than one step or action, the order of the steps or actions of the method is not necessarily limited to the order in which the steps or actions of the method are recited. Furthermore, reference numerals (if any) appearing between parentheses in the claims are provided merely for convenience and should not be construed as limiting the claims in any way.

[0109] In the claims, as well as in the foregoing description, all transitional phrases such as "comprises," "comprising," "carrying," "having," "containing," "involving," "containing," "including," and the like are to be construed as open-ended, i.e., meaning including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

Claims

1. A subsystem (100) for controlling illumination of a lighting device (300) via motion detection, the lighting device operating in a standby mode in which the light is off or at a minimum dimming level, and an active mode in which the light is at full power or in a dimmed state above the minimum dimming level, the subsystem comprising: - a radar sensor (200) configured to detect motion in a detection area by sampling a derived signal from the detection area at a sampling frequency; - a controller (400) communicatively coupled to the radar sensor (200) and the lighting device (300), the controller (400) being configured to: - when the lighting device (300) is in standby mode, setting the sampling frequency of the radar sensor (200) to an initial value lower than twice the first Nyquist frequency, and - controlling the lighting device (300) based on sensor data obtained by the radar sensor (200) at a specified sampling frequency; and Wherein when the lighting device (300) is in the standby mode, the first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected by the radar sensor (200) in the detection area.

2. The subsystem (100) of claim 1, wherein the initial value is below the first Nyquist frequency.

3. The subsystem according to claim 1, wherein the controller (400) is further configured to: - When motion is detected from the sensor data obtained by the radar sensor (200), a control signal is generated to trigger the lighting device (300) to change from the standby mode to an active mode.

4. The subsystem according to claim 2, wherein the controller (400) is further configured to: - When motion is detected from the sensor data obtained by the radar sensor (200), a control signal is generated to trigger the lighting device (300) to change from the standby mode to an active mode.

5. The subsystem of claim 3, the subsystem (100) comprising a wireless transceiver, and wherein the wireless transceiver is configured to: - wirelessly transmitting the sensor data and / or the control signal to at least one of another lighting device (300', 300"), a remote control device (320) and an intelligent electronic device (330) belonging to a user.

6. The subsystem of claim 4, the subsystem (100) comprising a wireless transceiver, and wherein the wireless transceiver is configured to: - wirelessly transmitting the sensor data and / or the control signal to at least one of another lighting device (300', 300"), a remote control device (320) and an intelligent electronic device (330) belonging to a user.

7. The subsystem according to any one of claims 3 to 6, wherein the controller (400) is further configured to: - when the lighting device (300) is in the activation mode, determining the operation mode of the radar sensor (200) to be a normal operation mode or a power saving mode according to power supply conditions, -When the lighting device is in the activation mode, the sampling frequency of the radar sensor is set to: - for the normal operating mode, at least twice the second Nyquist frequency, and - for the power-save mode, below twice the second Nyquist frequency, and Wherein when the lighting device is in the active mode, the second Nyquist frequency is set to: a second estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area.

8. The subsystem (100) according to any one of claims 1 to 6, wherein the controller (400) is further configured to: - deriving detailed motion information via Doppler analysis based on samples of sensor data obtained by the radar sensor (200) when motion is detected, and wherein the detailed motion information includes at least one of: the number of motion sources, the direction of movement of the motion sources relative to the radar sensor, the speed of the motion, and the classification of the motion; - controlling the lighting device (300) in a more advanced mode according to the detailed motion information.

9. The subsystem according to any one of claims 1 to 6, wherein the radar sensor (200) further comprises: an analog front end (AFE) arranged to be powered on and off separately from the rest of the radar sensor; as well as The controller (400) is further configured to: - Controlling a power cycle of the AFE of the radar sensor at the same frequency as the sampling frequency by turning the AFE on before a sampling instant at which the radar sensor performs sampling and turning the AFE off once sampling has taken place.

10. A system (500) for controlling lighting via motion detection, the system (500) comprising: - A subsystem (100) according to claim 1; wherein the subsystem (100) is configured to generate a control signal to: - triggering the lighting device (300) to change from the standby mode to an active mode when motion is detected, and - triggering the lighting device (300) to change from the active mode to the standby mode when no motion is detected after a first predefined time period.

11. A method for controlling illumination of a lighting device via motion detection, the lighting device operating in a standby mode in which the light is off or at a minimum dimming level and an active mode in which the light is at full power or in a dimmed state above the minimum dimming level, the method comprising: - detecting (S601) motion in a detection area by a radar sensor (200), said radar sensor (200) sampling a derived signal from said detection area at a sampling frequency; - when the lighting device (300) is in the standby mode, setting (S602) the sampling frequency of the radar sensor to an initial value lower than twice a first Nyquist frequency, wherein the first Nyquist frequency is equal to: a first estimated maximum Doppler frequency of motion to be detected by the radar sensor (200) in the detection area when the lighting device (300) is in the standby mode; - controlling (S603) the lighting device (300) based on sensor data obtained by the radar sensor (200) at a specified sampling frequency.

12. The method according to claim 11, further comprising: - When motion is detected (S604) from the sensor data obtained by the radar sensor (200), a control signal is generated (S607) to trigger the lighting device (300) to change from the standby mode to an active mode.

13. The method according to claim 11, further comprising: - when the lighting device is in the standby mode, setting ( S605 ) the sampling frequency of the radar sensor to a value increased compared to the initial value when motion is detected ( S604 ) from sensor data obtained by the radar sensor; - when detection of motion is confirmed (S606) from a new set of sensor data obtained by the radar sensor operating at the sampling frequency of the increased value, generating (S607) a control signal to trigger the lighting device to change from the standby mode to the active mode; - When no detected motion is confirmed (S606) from the new sensor data set obtained by the radar sensor operating at the sampling frequency of the increased value, setting (S602) the sampling frequency back to the initial value.

14. The method according to any one of claims 11 to 13, further comprising: - when the lighting device is in the standby mode, sweeping the sampling frequency to several different discrete sampling frequencies lower than twice the first Nyquist frequency, and setting the sampling frequency to each of the several different discrete sampling frequencies within a second predefined time period, so that the radar sensor can perform stable detection; - recovering the motion-related Doppler frequency signal from aliasing by comparing subsampled output sets of sensor data obtained by sampling the radar sensor at each of the several different discrete sampling frequencies.

15. The method according to claim 12 or 13, further comprising: - when the lighting device is in the activation mode, determining the operation mode of the radar sensor to be a normal operation mode or a power saving mode according to power supply conditions, -When the lighting device is in the activation mode, setting the sampling frequency of the radar sensor to: - for the normal operating mode, at least twice the second Nyquist frequency, and - for the power-save mode, below twice the second Nyquist frequency, and Wherein when the lighting device is in the active mode, the second Nyquist frequency is set to: a second estimated maximum Doppler frequency of motion to be detected by the radar sensor in the detection area.

16. The method according to any one of claims 11 to 13, further comprising: - deriving detailed motion information via Doppler analysis based on a sampled output of sensor data obtained by the radar sensor when motion is detected, and wherein the detailed motion information includes at least one of: a number of motion sources, a direction of movement of the motion sources relative to the radar sensor, a speed of the motion, and a classification of the motion; - Controlling the lighting device in a more advanced mode according to the detailed motion information.

17. A computer program product comprising a computer program which, when executed by a computer, causes the computer-operated lighting device to operate in a standby mode in which the light is off or at a minimum dimming level and an active mode in which the light is at full power or in a dimmed state above the minimum dimming level, wherein: - receiving samples from a radar sensor (200) that detects (S601) motion in a detection area of ​​the radar sensor (200), the radar sensor (200) sampling a derived signal from the detection area at a sampling frequency; - when the lighting device (300) is in the standby mode, setting (S602) the sampling frequency of the radar sensor to an initial value lower than twice a first Nyquist frequency, wherein the first Nyquist frequency is equal to: a first estimated maximum Doppler frequency of motion to be detected by the radar sensor (200) in the detection area when the lighting device (300) is in the standby mode; - controlling (S603) the lighting device (300) based on sensor data obtained by the radar sensor (200) at a specified sampling frequency.

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