Power reduction for radar-based motion detection systems and methods

Abstract

Radar-based motion detection systems are widely used in the fields of smart homes, smart buildings, and smart cities for automatic control. This invention discloses a method, subsystem, system, and computer program for achieving radar sensor power reduction by operating the radar sensor in a sub-sampling manner in a lighting control system. By combining information about the status of the lighting device and the detection area, the sampling frequency of the radar sensor is configured according to the user scenario. From there, a balance between power reduction and motion detection performance is achieved.

Description

[Technical Field]

[0001] The present invention relates generally to radar-based motion detection systems used in control, for example, lighting control. Disclosed herein are various methods, subsystems, systems, and computer-readable media relating to, among other things, motion detection-based lighting control systems and methods. [Background technology]

[0002] Mains power standby 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 consumption requirements, which are becoming stricter with time.

[0003] In lighting applications, it is becoming increasingly common to employ sensor systems to achieve automatic lighting control that is energy efficient and improves user experience and comfort. Even when a lighting device is in standby mode, the associated sensor system is still operational to perform some control function, such as detecting certain events in order to turn on the light at the appropriate time. When a lighting device is in standby mode, the power consumption of the sensor system is added to the mains standby power consumption of the lighting device.

[0004] Furthermore, there is an increasing need to add more functionality to lighting devices. Some functions, such as RF links for remote control and occupancy sensing, operate in both standby and active modes of the lighting device. Currently, radar systems for occupancy detection are penetrating the market. A technique for reducing the power of radar systems is power cycling, in which the power supply to the radar system is switched on and off as repeatedly as possible. The power consumption of radar sensors is partially reduced by reducing their duty cycle. The minimum duty cycle of a radar sensor is typically determined by the maximum response time requirement of the system.

[0005] DALI (Digital Addressable Lighting Interface) is a standard communication protocol and network-based system for lighting control. DALI systems are defined by the technical standards IEC 62386 and IEC 60929. To meet the needs of Internet of Things (IoT) applications in the lighting field, the DALI protocol has evolved. The new DALI sensor-ready (SR) interface, standardized by ANSI C137.4, integrates power to sensors connected to the bus while simultaneously 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 consumes only a fraction of the mains power. 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 these features are used by a statistical classifier to identify the unknown object.

[0007] US2017353189A1 relates to a sub-sampling motion detector configured to detect motion information of a measured object, the sub-sampling motion detector receiving a first wireless radio frequency (RF) signal and transmitting 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, M.G. Amin, Y.D. Zhang and F. Ahmad, "Multi-window time-frequency signature reconstruction from undersampled continuous-wave radar measurements for fall detection," in IET Radar, Sonar & Navigation, vol. 9, no. 2, pp. 173-183, 2015, discloses a hybrid approach applying compressed sensing and multi-window analysis based on Slepian or Hermite functions for fall detection and classification in the case of full data or compressed observations. Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above, the present disclosure relates to methods, subsystems, systems, computer programs, and computer-readable media for further reducing the power consumption of sub-radar sensor systems through sub-sampling in lighting control scenarios. Among other things, various computer-readable media (transitory and non-transitory), methods, systems, and subsystems are provided that reduce the sampling frequency of the radar sensor to a level sufficient to meet application requirements related to the corresponding state of the lighting device. [Means for solving the problem]

[0010] Radar is a well-known detection system that uses radio waves to determine the range, angle, or velocity of moving objects. Radar systems function by emitting energy into space and monitoring echoes or reflected signals from objects within a surrounding area, or detection area. Typically, a radar system has a transmitter that emits radio waves, or radar signals, into space in a predetermined direction. When the radar signal contacts an object, it is usually reflected back or scattered in many directions, depending on the material and surface of the object and the angle of incidence of the radar signal. A portion of the radar signal penetrates the target or is absorbed by the target to some extent. The portion of the radar signal that reflects back toward the radar system is captured by a receiver in the radar system and is desired for the radar system to function. If an object is moving toward or away from the transmitter within the detection area, a corresponding change in the frequency of the reflected radio waves occurs due to the Doppler effect. In a simple example, by comparing the frequency shift of the emitted signal and the echo received from the detection area, a radar system can derive the relative velocity of a moving object based on the Doppler effect. In addition to the velocity measurement, the distance from the moving target and the orientation of the moving target can also be derived. Depending on the mechanism of operation, different methods may be used to derive certain types of information. For pulse radar, the distance measurement can be based on the time-of-flight principle, while for continuous wave radar, the frequency shift of the received signal compared to the transmitted signal is proportional to the distance traveled. The orientation of a moving target relative to the radar sensor may be derived by using some kind of antenna or antenna array.

[0011] In a more realistic scenario, the echoes received by a radar system may be mixed signals resulting from two or more moving objects. Furthermore, due to the different surfaces of the moving objects and the different angles of incidence of the signal emitted from the radar system to each of the moving objects, the echoes captured by the radar system are hybrid signals including directly reflected signals and scattered signals that may bounce back to the radar system after tracing several surfaces of stationary or other moving objects. The different echoes combine constructively or destructively at the receiving antenna of the radar system. Therefore, signal processing can be quite complex and power-consuming in a radar system.

[0012] One modern use of radar systems is presence detection based on radar sensing, which is widely used for automatic control in smart building and smart city scenarios. Presence detection can be as simple as providing binary information indicating the presence of people or moving objects within a detection area. Presence detection can also be more sophisticated, providing detailed motion information such as the number of objects within a detection area, the object's location, the object's trajectory, and even coarse or fine classification of the motion involved.

[0013] In terms of lighting control, more advanced radar sensing capabilities are desirable but may conflict with power consumption requirements. Therefore, the present invention aims to reduce the power consumption of radar sensors by operating the sensors in sub-sampling mode whenever possible, and to adapt the sampling frequency to the lighting device conditions and application scenario.

[0014] For ease of explanation, two operating states are defined for a lighting device: standby mode and active mode. The standby mode of a lighting device includes a situation where the lamp is off or at a minimum dimming level, e.g., ≦10%. The active mode of a lighting device includes a situation where the lamp is at full power or in a dimmed state with a dimming level >10%. However, such definitions are for illustrative purposes only and do not exclude other possibilities of 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, there is provided a subsystem for controlling illumination of a lighting device through motion detection, the subsystem including: a radar sensor configured to detect motion in a detection area by sampling a derived signal from the detection area at a sampling frequency; and a controller communicatively coupled to the radar sensor and the lighting device, the controller configured to set the sampling frequency of the radar sensor when the lighting device is in a standby mode to an initial value that is lower than twice a first Nyquist frequency, and to control the lighting device based on sensor data obtained by the radar sensor at a specified sampling frequency, wherein the first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected in the detection area by the radar sensor when the lighting device is in standby mode.

[0016] As explained above in connection with the operating principle of a radar system, a radar sensor functions by comparing the frequency shift of an emitted signal with a received echo from a detection area. The claimed derived signal from the detection area is a downconverted signal obtained by mixing the reflected signal from the detection area with an originally emitted radar signal that is known to the radar sensor. The derived signal therefore corresponds to a baseband signal at the radar sensor that is ready for sampling by an analog-to-digital converter (ADC).

[0017] In a typical digital signal processing system, the sampling frequency of the ADC should be at least twice the Nyquist frequency to recover the original signal according to the Nyquist sampling criterion. 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 lower than twice the first Nyquist frequency, the power consumption of the radar sensor is reduced by operating in sub-sampling mode, with the penalty being that aliasing may exist due to sub-sampling, resulting in signal distortion.

[0019] In Doppler radar, the signal bandwidth of the baseband signal is equivalent to the Doppler shift. Although accurately deriving the actual Doppler shift, which depends on many factors related to the moving object and the environment, can be quite complicated, a rule of thumb estimation of the maximum Doppler shift can be made depending on the detection area and the type of motion to be detected within the detection area.

[0020] It is more advantageous if the first Nyquist frequency is tailored not only to the detection area but also to the state of the lighting device. For example, in an indoor environment, when a lamp is in standby mode, this typically indicates that there is no person in the area. Therefore, when the lighting device is in standby mode, the first motion to be detected by the radar sensor is typically a large motion, such as a person entering the room. In contrast, when the lighting device is in active mode, which typically indicates that there is already someone in the room, the radar sensor may only detect minor human motion, such as typing on a keyboard or talking on a phone, most of the time. Because the Doppler shifts caused by large and small motions can be quite different, a more accurate estimation of the first Nyquist frequency according to the motion to be detected can be made by taking into account the detection area and the state of the lighting device. This reduces the possibility that the sampling frequency will be set unnecessarily high, resulting in unnecessary power consumption.

[0021] Furthermore, when the lighting device is in standby mode, it is important to detect whether there is motion within the detection area, in addition to deriving detailed motion information, in order to turn on the lamp in time. Therefore, the radar sensor may only provide basic binary presence detection. The processing of a binary presence detection radar sensor is similar to that of a baseband energy detector, and therefore the Doppler shift distortion caused by subsampling will not lead to a degradation of system performance. By operating in subsampling mode at a sampling frequency lower than twice the first Nyquist frequency, the radar's power consumption can be significantly reduced, which is an extremely beneficial feature for lighting control in standby mode.

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

[0023] Preferably, the subsystem is contained in a lighting fixture, and a controller (communicatively coupled to the radar sensor and lighting device) is used for both motion detection and lighting control. As an example, a lamp / lighting fixture may have a radar sensor integrated into the same housing as the lighting device.

[0024] Alternatively, the subsystem may not be included in a lighting fixture, and the radar sensor, lighting device, and controller may be physically distributed. Sensor data from the radar sensor and status information of the lighting device may be exchanged with each other via a controller communicatively coupled to the radar sensor and lighting device. Thus, the lighting device may have a separate local controller for lighting control, and the radar sensor may have a separate processor for local signal processing. In this sense, the 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] Because radar sensor power consumption scales with sampling frequency and binary presence detection when the lamp is in standby mode is not vulnerable to distortion due to aliasing, it is desirable to further reduce the sampling frequency below the first Nyquist frequency in a deep sub-sampling mode to save more energy.

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

[0028] Motion can be confirmed by detecting a Doppler shift in the reflection from the detection area compared to the originally emitted radar signal. In binary presence detection, if energy is detected in the baseband, this also confirms presence in the detection area. Processing can be performed in a local processor of the radar sensor itself. It can also be performed in a controller included in the subsystem if the radar sensor does not have a local processor or if it is determined that performing the calculations in the controller included in the subsystem is more efficient. A control signal is generated in response to confirmation of presence detection, thus triggering a state change of the lighting device from standby mode to active mode.

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

[0030] If the subsystem is distributed in nature and the radar sensor, controller, and lighting device are not co-located in one lighting fixture, it is advantageous to use a wireless transceiver to enable connectivity. Preferably, the sensor data from the radar sensor and the control signals generated therefrom can also be wirelessly shared to a remote control device for other control purposes besides lighting control, such as control of entrances, HVAC, blinds, etc. The same sensor data and control signals can also be shared remotely with a user via a smart electronic device, such as a smartphone or wearable device with wireless communication capabilities. For example, an owner can have real-time occupancy or intrusion information of their home while at work or on the move.

[0031] Alternatively, if mobility is not that important, such connections may be realized via wired links, for example the controller is connected to the lighting devices via a cable or bus.

[0032] In another embodiment, the controller is further configured to determine an operation mode of the radar sensor to be either a normal operation mode or a power saving mode depending on a power supply condition when the lighting device is in the active mode, and to set a sampling frequency of the radar sensor when the lighting device is in the active mode to be at least twice the second Nyquist frequency in the normal operation mode and to be lower than twice the second Nyquist frequency in the power saving mode, wherein the second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in the active mode.

[0033] As mentioned above, it is beneficial to tune the Nyquist frequency to the combination of the lighting device state and detection area. Considering that there are only small movements with small amplitudes most of the time when the lighting device is in active mode, the sampling frequency should be increased to obtain a good signal-to-noise ratio in order to detect these signals. 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 mode or standby mode, it is also beneficial to decouple the sampling frequency setting of the radar sensor when the lighting device is in different states.

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

[0035] However, if the radar sensor is powered by a DALI SR interface and shares the same bus with multiple other sensors, it may still be desirable for the radar sensor to remain in power-saving mode. In this case, the sampling frequency of the radar sensor is lower than twice the second Nyquist frequency in sub-sampling mode. In this case, the sampling frequency can be set slightly lower than twice the second Nyquist frequency or even lower than twice the second Nyquist frequency to accommodate the actual power supply conditions.

[0036] Advantageously, the controller is further configured to derive detailed motion information by Doppler analysis based on samples of sensor data obtained by the radar sensor when motion is detected, the detailed motion information including at least one of the number of motion sources, the distance from the motion sources to the radar sensor, the orientation of the motion sources relative to the radar sensor, the direction of motion of the motion sources relative to the radar sensor, the speed of the motion, and a classification of the motion, and to control the lighting device in a more advanced mode in response to the detailed motion information.

[0037] Detailed motion detection based on Doppler or micro-Doppler analysis can be used to derive more sophisticated presence information. Such detailed motion information can enhance lighting control to a more advanced level, such as switching a lighting device to a scene based on the classification of the motion. For example, if the motion detection indicates that a person is lying on a sofa, the controller may send a control signal to trigger the lighting device to switch to a relaxing scene. In another example, if the motion detection indicates that a person is playing a video game, the controller may send another control signal to trigger the lighting device to switch to a stimulating scene by manipulating the light spectrum in a different way.

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

[0039] It is also disclosed that if no motion is detected by the radar sensor after a first predetermined period of time, the controller is further configured to generate another control signal to trigger the lighting device to switch from an active mode to a standby mode. The first predetermined period of time can be determined according to power saving requirements in terms of green building or according to certain expectation regarding user experience.

[0040] Detailed movement information may also be sent to a remote control device for other control purposes, or to a smart electronic device belonging to the user for more advanced monitoring.

[0041] In one embodiment, the radar sensor further includes an analog front-end (AFE) configured to be powered on and off separately from the rest of the radar sensor, and the controller is further configured to control the power cycle of the AFE of the radar sensor at the same frequency as the sampling frequency by turning on the AFE before a sampling moment at which the radar sensor takes a sample and turning off the AFE once the sample has been taken.

[0042] Further advantageously, sub-sampling can be used in combination with other power saving techniques in the radar sensor, such as power cycling. The AFE of the radar sensor uses a clock that operates at the same frequency as the sampling clock, but can be subjected to duty cycling with a slight phase shift to ensure stable sampling operation of the radar sensor.

[0043] In one embodiment, there is provided a system for controlling lighting by motion detection, the system comprising a subsystem according to a first aspect, the subsystem configured to generate a control signal for triggering a lighting device to switch from a standby mode to an active mode if motion is detected, and for triggering the lighting device to switch from the active mode to the standby mode if no motion is detected after a first predetermined period.

[0044] Preferably, the system further includes a remote control device or a smart electronic device belonging to a user. Also, sensor data and / or control signals may be transmitted to the remote control device or the smart electronic device belonging to a user for other control or monitoring purposes besides pure lighting control. In another example, there may be other sensors co-located with the remote control device or the smart electronic device belonging to a user. Thus, the radar sensor and other sensors included in the subsystem may remotely cooperate or coordinate by sharing sensing data from different modalities.

[0045] It is further disclosed that the system includes another lighting device. The subsystem is used to collectively control two or more lighting devices in the system.

[0046] According to a second aspect of the present invention, there is provided a method for controlling illumination of a lighting device by motion detection, the method comprising: detecting motion in a detection area by a radar sensor, wherein the radar sensor samples a derived signal from the detection area at a sampling frequency; setting the sampling frequency of the radar sensor when the lighting device is in a standby mode to an initial value that is 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 in the detection area by the radar sensor when the lighting device is in the standby mode; and controlling the lighting device based on sensor data obtained by the radar sensor at the specified sampling frequency.

[0047] Preferably, the method further comprises detecting movement by processing signals sampled at a sampling frequency and derived from a radar sensor, the radar sensor sampling a derived signal from the detection area at the sampling frequency, the processed signals being 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 includes generating a control signal to trigger the lighting device to switch from a standby mode to an active mode when motion is detected from the sensor data obtained by the radar sensor.

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

[0051] When the radar sensor operates in deep subsampling mode, the false positive rate may increase. If the lighting device is turned on due to a false positive motion detection, it also introduces undesirable power consumption into the system. Therefore, it is preferable to use additional steps to reduce the likelihood of false positives. The controller sets the sampling frequency of the radar sensor to an increased value after motion is detected from sensor data obtained by the radar sensor operating at an initial sampling frequency. If motion is confirmed by a new set of sensor data obtained by the radar sensor operating at the increased sampling frequency, a control signal is generated to trigger a state change of the lighting device; otherwise, the controller determines a false positive and resets the sampling frequency of the radar sensor to the initial value to save power.

[0052] Advantageously, the method further includes sweeping a sampling frequency when the lighting device is in standby mode to a plurality of different discrete sampling frequencies that are lower than twice the first Nyquist frequency, and setting the sampling frequency to each of the plurality of different discrete sampling frequencies for a second predetermined period to enable stable detection by the radar sensor, and recovering the motion-related Doppler frequency signal from aliasing by comparing sets of sub-sampled outputs of sensor data obtained by the radar sensor sampled at each of the plurality of different discrete sampling frequencies.

[0053] In most cases, only binary presence detection is expected for radar sensors operating in sub-sampling mode. However, in some cases, it is desirable to derive a little more information from sub-sampling radar, such as the speed of motion, the number of motion sources, etc. The motion-related Doppler frequency signal may be recovered from aliasing by sweeping the sampling frequency to multiple different discrete sampling frequencies that are lower than twice the first Nyquist frequency and comparing the sub-sampled outputs of the sensor data sampled at each of the multiple different discrete sampling frequencies. In some cases, this method can be time-consuming to derive the desired signal, and therefore, this approach represents a trade-off between latency and power consumption.

[0054] In one embodiment, the method further includes determining an operation mode of the radar sensor to either a normal operation mode or a power saving mode depending on a power supply condition when the lighting device is in the active mode, and setting a sampling frequency of the radar sensor when the lighting device is in the active mode to be at least twice the second Nyquist frequency in the normal operation mode and lower than twice the second Nyquist frequency in the power saving mode, wherein the second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in the active mode.

[0055] Preferably, the method further includes deriving detailed motion information by Doppler analysis based on a sampled output of sensor data obtained by the radar sensor when motion is detected, wherein the detailed motion information includes at least one of the number of motion sources, the distance from the motion sources to the radar sensor, the orientation of the motion sources relative to the radar sensor, the direction of motion of the motion sources relative to the radar sensor, the speed of the motion, and a 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 include generating another control signal to trigger the lighting device to switch from the active mode to the standby mode if no motion is detected by the radar sensor after a first predetermined period when the lighting device is in the active mode.

[0057] The present invention may further be embodied in a computer program or computer program product comprising code means for causing a computer to carry out the above-mentioned method of a subsystem for controlling lighting by motion detection. [Brief explanation of the drawings]

[0058] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. [Figure 1] 1 illustrates an exemplary lighting control system based on motion detection. [Figure 2] 1 illustrates a schematic diagram of exemplary components of a subsystem disclosed herein for controlling lighting through motion detection. [Figure 3] 1 shows the sampling frequency settings that meet the Nyquist sampling criterion for a given set of signals. [Figure 4] Indicates the sampling frequency setting in subsampling mode. [Figure 5]1 shows a power cycling control. [Figure 6] 1 shows a system for controlling lighting by motion detection. [Figure 7] 1 shows a flowchart of a method for controlling lighting by motion detection. [Figure 8] 1 shows a flowchart of a method for controlling lighting by motion detection that takes precautions against false positives. DETAILED DESCRIPTION OF THE INVENTION

[0059] Adopting radar-based motion detection systems to achieve automatic control is desirable for many control systems in various scenarios, such as smart homes, smart buildings, and smart cities. Automatic control based on motion or presence detection makes human interaction with the surrounding environment more intuitive and spontaneous. Some products, such as lighting devices, must comply with increasingly stringent regulations regarding standby power consumption. Because sensor systems operate even when the lighting device is in standby mode, the power consumption of the sensor system directly adds to the standby power consumption of the lighting device. Therefore, it is important to reduce the power consumption of the sensor system without compromising control functionality.

[0060] FIG. 1 shows an example of a motion detection based lighting control system including a subsystem 100 as disclosed, at least one lighting device 300′, 300″, a remote control device 320, and a smart electronic device 330 belonging to a user. When a person enters the detection area, a radar sensor included in the subsystem 100 detects the motion, and the subsystem may then share the sensor data and / or control signals derived from the sensor data with multiple nearby devices, such as the lighting devices 300′, 300″ and the remote control device 320. The subsystem may also share the sensor data and / or control signals with remote smart electronic devices over a network.

[0061] The lighting devices 300′, 300″ may be co-located with the subsystem 100 in the same area, such as in the same room or nearby, and may be communicatively coupled to the subsystem via wires or wirelessly. The subsystem may also communicate wirelessly to a remote control device, which may be used for other control purposes besides lighting control, such as controlling entrances, HVAC, blinds, etc. The same sensor data and control signals can also be shared with a user remotely via a smart electronic device, such as a smartphone or wearable device with wireless communication capabilities. In one example, an owner can have real-time occupancy or intrusion information of their home while at work or on the move.

[0062] Exemplary components of a subsystem 100 for controlling lighting through motion detection as disclosed herein are shown schematically in FIG. 2. The 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. Using knowledge of the detection area and feedback from the lighting device regarding the lamp status, the controller is configured to set the sampling frequency of the radar sensor to an initial value lower than twice the first Nyquist frequency when the lighting device is in standby mode. Furthermore, the controller is configured to control the lighting device based on sensor data obtained by the radar sensor at the specified sampling frequency. The first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in standby mode. Thus, the radar sensor operates in a sub-sampling mode when the lighting device is in standby mode to reduce power consumption.

[0063] To better understand the concept of sampling in digital signal processing, Figure 3 shows the setting of sampling frequencies that meet the Nyquist sampling criterion for a given set of signals. In this example, the set of signals is band-limited and their frequency components are band-limited by f BW We focus on the following: Following the Nyquist sampling criterion, half the sampling rate F is used to avoid folding or aliasing. s / 2 is the signal bandwidth f BW By definition, it should be no smaller than half the sampling rate F s / 2 is the Nyquist frequency F Ny Therefore, to prevent aliasing, the sampling frequency is typically set to F s =2F Ny , F Ny ≧f BW is set to

[0064] Figure 4 shows the sampling frequency settings in subsampling mode. Here, F Ny =f BW , Fs<2F Ny The power consumption of the ADC and subsequent digital processing circuitry is proportional to the sampling frequency, therefore, by operating in sub-sampling mode the power consumption of the radar sensor is reduced accordingly.

[0065] Therefore, to configure a radar sensor to operate in sub-sampling mode, the first step is to estimate the potential bandwidth of the signal. In the case of a Doppler radar used for motion detection in this case, the signal bandwidth of the baseband signal is equivalent to the potential Doppler shift to be detected. Although accurately deriving the actual Doppler shift can be quite complicated, depending on many factors related to the moving object and the environment, an empirical estimate of the maximum Doppler shift can be made depending on the detection area and the type of motion to be detected within the detection area. For example, in an indoor environment, it is typically assumed that the maximum walking speed of a person is 3 m / s or 10.8 km / h or less. In an outdoor environment, depending on the detection area, the typical maximum speed limit for a vehicle may be 130 km / h on a highway or 50 km / h on a local road. Using knowledge of the maximum speed of motion to be detected for a certain detection area, the subsystem can estimate the maximum Doppler shift of motion to be detected within the detection area, taking into account the carrier frequency of the radar signal emitted by the radar sensor and the principles of Doppler shift.

[0066] As an example, consider a 24 GHz Doppler radar deployed to detect motion in an indoor environment. The maximum Doppler shift to be detected by the radar sensor can be estimated based on the following parameters: maximum speed of movement, Here, the maximum indoor casual walking speed of a person (Δv max ):3m / s, Radar signal carrier frequency (f0): 24 GHz, and · Speed ​​of light (c): 3e8m / s. Using these parameters, the maximum Doppler shift can be calculated. TIFF0007767269000001.tif12117

[0067] By linking with the lamp status, a more accurate estimation of the maximum Doppler shift can be made. Typically, a certain state of the lamp (active or standby) also indicates whether an area is occupied or not. Therefore, when the lighting device is in standby mode, the motion to be detected by the radar sensor at the first time is typically a large motion, such as a person entering a room. In contrast, when the lighting device is in active mode, which typically indicates that a person is already present in the room, the radar sensor may detect only small human motions, such as typing on a keyboard or talking on a phone, most of the time, although the instantaneous velocity may be much higher than that of large body movements. Because the Doppler shift and echo amplitude due to large and small movements can behave very differently, a more accurate estimation of the first Nyquist frequency can be made by linking the detection area and the lighting device status. This reduces the possibility that the sampling frequency will be set unnecessarily high, and thus, unnecessary power consumption can be avoided.

[0068] Figure 5 shows the power cycling control. As a commonly used technique for power saving, power cycling control is also widely used in radar detection systems. The whole system is alternately switched on and off, and the whole period T cycle Compared with the on-period T on The intention is to keep T as small as possible. on and T cycle The ratio of the sampling frequency to the sampling clock is called the duty cycle. Subsampling can be used in combination with other power-saving techniques in radar sensors, such as power cycling. The radar sensor's AFE uses a clock that operates at the same frequency as the sampling clock but can undergo duty cycling with a slight phase shift to ensure stable sampling operation of the radar sensor.

[0069] An example of how this can be implemented is shown below. The subsystem or radar sensor further includes a clock generation system. The clock generation system generates a sampling clock, or a first clock, according to a sampling frequency specified by the controller. For power cycling of the AFE of the radar sensor, the clock generation system may generate another clock from the first clock previously used to control the sampling frequency of the radar sensor, where the another clock operates at the same frequency as the sampling frequency but with a phase delay, where the phase delay ensures that the AFE portion of the radar sensor is stabilized 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 first clock has an advanced phase compared to the another clock. Furthermore, the on-period T of the AFE is on should be long enough to allow the signal from the analog front end to be properly sampled by the ADC.

[0070] The combination of sub-sampling operation of the radar sensor and power cycling of the AFE provides further power reduction compared to using either of the two techniques alone.

[0071] 6 shows a system for controlling lighting through motion detection. Subsystem 100 is configured to generate a control signal for controlling a state change of a lighting device, such as turning on a lamp when motion is detected and turning off the lamp when no motion is detected after a first predetermined period of time. Depending on the trade-off between the energy efficiency of the system and the user experience, the first predetermined period can be configured to be relatively long or short. If the first predetermined period is set too short, it may be very efficient from an energy saving perspective, but may result in a very poor user experience in which the lamp is switched off just by the user sitting still for a while.

[0072] As mentioned above, the system may further include a remote control device or a smart electronic device belonging to a user. The same information related to motion detection can be shared wirelessly to these remote devices for different use cases. Various radio transceivers compliant with various communication standards, such as 3G / 4G / 5G cellular, WiFi, Zigbee, BLE, Zwave, Thread, etc., can be deployed to enable such wireless links in indoor and / or outdoor applications. In another example, the system may further include another lighting device, or even two or more other lighting devices. These lighting devices are collectively controlled. Employing a radar sensor in one subsystem and sharing the same motion detection information for control of different nearby products (either directly by the subsystem or via a remote control device) may be a more cost-effective way to realize building automation.

[0073] 7 shows a flowchart of a method executed by a subsystem for controlling lighting by motion detection. In step S601, a radar sensor 200 included in the subsystem is configured to detect motion within a detection area by sampling a derived signal from the detection area at a sampling frequency. In step S602, a controller included in the subsystem is configured to set a sampling frequency of the radar sensor when the lighting device is in a standby mode to an initial value lower than twice a first Nyquist frequency, the first Nyquist frequency being equal to a first estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor 200 when the lighting device 300 is in the standby mode. In step S603, the controller is further configured to control the lighting device 300 based on sensor data obtained by the radar sensor 200 at the specified sampling frequency.

[0074] If motion is detected by the controller from the sensor data obtained by the radar sensor in step S604, a control signal is generated in step S607 to trigger the lighting device 300 to switch from standby mode to active mode.

[0075] When the radar sensor operates in deep subsampling mode, binary presence information is derived using an approach similar to energy detection, i.e., by detecting that the energy of the derived signal exceeds a certain threshold, instead of acquiring the original Doppler shift information. Therefore, the false positive rate may be higher compared to normal operation. If the lighting device is turned on due to a false positive determination of motion detection, it also introduces undesirable power consumption of the system. Therefore, it is disclosed to have further steps to reduce the possibility of false positives. Figure 8 shows a flowchart of a method for controlling lighting by motion detection that takes precautions against false positives.

[0076] Instead of immediately generating a control signal when motion is detected in step S604, the controller sets the sampling frequency of the radar sensor to an increased value compared to the initial value in step S605. If motion is confirmed by a new set of sensor data obtained by the radar sensor operating at the increased sampling frequency in step S606, a control signal for triggering a state change of the lighting device is generated in step S607; otherwise, the controller determines it is a false positive and resets the sampling frequency of the radar sensor to the initial value in step S602 to save power.

[0077] In most cases, only binary presence detection is expected for radar sensors operating in sub-sampling mode, where the sampling frequency is less than twice the Nyquist frequency. However, in some cases, it is desirable to derive more detailed motion information from sub-sampling radar, such as the speed of motion and the number of motion sources. The motion-related Doppler frequency signal may be recovered from aliasing by sweeping the sampling frequency to several different discrete sampling frequencies less than twice the first Nyquist frequency and comparing the sub-sampled outputs of the sensor data sampled at each of the several different discrete sampling frequencies. Of course, this method takes time to derive the desired signal, thus trading off latency and power consumption.

[0078] In the practical example above where tones are detected, the highest frequency tone is 350 Hz or f BW = 350 Hz, F s1 = 270Hz and F s2 It is assumed that there are two discrete sampling frequencies set at F = 330 Hz. According to the Fourier transform (FT) and the operation of the sampling system, the actual tone at 350 Hz appears at different positions after sampling. s1 = 270Hz, the actual tone at 350Hz is |F s1 -f BWappears at |=80Hz. On the other hand, F s2 = 330Hz, the actual tone at 350Hz is |F s2 -f BW = 20 Hz. Therefore, further processing can be used to distinguish the original frequency bins from the mirror frequencies or recover the original signal by sweeping a set of discrete sampling frequencies in the sub-sampled domain.

[0079] The method may further include determining an operation mode of the radar sensor to either a normal operation mode or a power saving mode depending on power supply conditions when the lighting device is in the active mode. In this case, the controller can determine the operation mode of the radar sensor depending on power supply conditions, such as when powered by a DALI SR interface or when very strict power regulations are imposed. In this case, a sampling frequency of the radar sensor when the lighting device is in the active mode is set to at least twice the second Nyquist frequency in the normal operation mode or lower than twice the second Nyquist frequency in the power saving mode, and the second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in the active mode.

[0080] Therefore, in a preferred configuration, the radar sensor is in a normal operating mode with a sampling frequency that meets the Nyquist sampling criterion. In this case, more reliable motion detection and richer details can be detected. If power saving is less important than more advanced motion detection-based functionality, the radar sensor may even operate in an oversampling mode with a sampling frequency much higher than twice the Nyquist sampling frequency.

[0081] Detailed motion detection based on Doppler or micro-Doppler analysis can be used to derive more sophisticated presence information. Such detailed motion information can enhance lighting control to a more advanced level, such as switching a lighting device to a lighting scene based on the classification of the motion. For example, if the motion detection derives that a person is lying on a sofa, the controller may send a control signal to trigger the lighting device to switch to a relaxing scene. In another example, if the motion detection derives that a person is playing a video game, the controller may 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.

[0082] If the radar sensor is powered by a DALI SR interface and shares the same bus with multiple other sensors, it may be desirable for the radar sensor to remain in power-saving mode. In this case, the sampling frequency of the radar sensor is set to less than twice the second Nyquist frequency in sub-sampling mode. In this case, the sampling frequency can be set to slightly less than twice the second Nyquist frequency or even less than twice the second Nyquist frequency, depending on the actual power supply conditions.

[0083] In some circumstances, the second Nyquist frequency may be the same value as the first Nyquist frequency, depending on the motion that is expected to be detected when the lighting device is in standby mode and in active mode.

[0084] The method according to the invention may be implemented in a computer as a computer implemented method, in a general purpose signal processor using multiple processing units, in dedicated hardware such as an FPGA or ASIC, or in a combination of both.

[0085] The executable code for the method according to the invention may be stored in a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, 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 invention when said program product is run on a computer.

[0086] 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.

[0087] Methods, systems, and computer-readable media (transitory and non-transitory) may be provided for implementing selected aspects of the above-described embodiments.

[0088] 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 numerous ways (e.g., using dedicated hardware) to perform the various functions discussed herein. A "processor" is an example of a controller that employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform the various functions discussed herein. A controller may be implemented with or without a processor, or 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).

[0089] In various implementations, 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, compact discs, optical discs, solid-state drives, etc.). In some implementations, these storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform at least a portion of the functions discussed herein. The various storage media may be fixed within the processor or controller, or may be portable such that one or more programs stored on those storage media can be loaded into the processor or controller 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 employed to program one or more processors or controllers.

[0090] 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. Additionally, it will be readily understood that the various networks of devices discussed herein may employ one or more wireless and / or wired / cable links to facilitate information transfer throughout the network.

[0091] The indefinite articles "a" and "an," as used in the specification and claims, unless expressly indicated otherwise, should be understood to mean "at least one."

[0092] As used 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" shall be construed as inclusive, i.e., including at least one, but also two or more of several elements or lists of elements, and optionally including additional unlisted items. Only terms such as "only one of" or "exactly one of," or when used in the claims, "consisting of," where the contrary is clearly indicated, refer to the inclusion of exactly one of several elements or lists of elements. In general, the term "or," as used herein, shall be construed as indicating exclusive alternatives (i.e., "one or the other, but not both") only when preceding terms of exclusivity, such as "any of," "one of," "only one of," or "exactly one of." "Consisting essentially of," when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0093] As used in this specification and claims, the phrase "at least one," referring to a list of one or more elements, should be understood to mean at least one selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each element specifically listed in the list of elements, and not excluding any combinations of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase "at least one" refers, whether related or unrelated to the elements specifically identified.

[0094] It should also be understood that, unless expressly indicated to the contrary, in any method claimed herein including two or more steps or actions, the order of the method steps or actions is not necessarily limited to the order in which the method steps or actions are recited. Also, any reference signs appearing in parentheses in the claims are provided for convenience only and should not be construed as limiting the claims in any way.

[0095] In the claims and in the above specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "consisting of," and the like, are to be understood to be open-ended, i.e., to mean including but not limited to. Only transitional phrases such as "consisting of" and "consisting essentially of" are closed or semi-closed transitional phrases.

Claims

1. 1. A subsystem for controlling illumination of a lighting device through motion detection, the lighting device operating in both a standby mode and an active mode, wherein the standby mode is when the lamp is off or when the lamp is at a minimum dimming level, and the active mode is when the lamp is at full output or when the lamp is at a dimming state above the minimum dimming level, the subsystem comprising: a radar sensor configured to detect motion within a detection area by sampling a derived signal from said detection area at a sampling frequency; a controller communicatively coupled to the radar sensor and the lighting device, setting a sampling frequency of the radar sensor when the lighting device is in a standby mode to an initial value that is less than twice the first Nyquist frequency; setting a sampling frequency of the radar sensor when the lighting device is in a normal operating mode in an active mode to at least twice the second Nyquist frequency; and controlling the lighting device based on sensor data obtained by the radar sensor at a specified sampling frequency; a controller configured to Including, the first Nyquist frequency is set to a first estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in a standby mode; The second Nyquist frequency is set to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in an active mode.

2. The subsystem of claim 1 , wherein the initial value is lower than the first Nyquist frequency.

3. The controller generating a control signal to trigger the lighting device to switch from a standby mode to an active mode when motion is detected from sensor data obtained by the radar sensor; 3. The subsystem according to claim 1 or 2, configured to:

4. The subsystem includes a radio transceiver, the radio transceiver comprising: transmitting the sensor data and / or the control signal wirelessly to at least one of another lighting device, a remote control device, and a smart electronic device belonging to a user; The subsystem of claim 3 configured to:

5. The controller determining an operation mode of the radar sensor to be either a normal operation mode or a power saving mode depending on a power supply condition when the lighting device is in an active mode; and The sampling frequency of the radar sensor when the lighting device is in an active mode is at least twice the second Nyquist frequency in the normal operating mode; in a power saving mode, the frequency is lower than twice the second Nyquist frequency; Set up, 5. The subsystem of claim 1, configured to:

6. The controller Deriving detailed motion information by Doppler analysis based on samples of sensor data obtained by the radar sensor when motion is detected, the detailed motion information including at least one of a number of motion sources, a direction of motion of the motion sources relative to the radar sensor, a speed of motion, and a classification of motion; and controlling the lighting device in a more advanced mode in response to the detailed motion information; 6. The subsystem of claim 1, configured to:

7. The radar sensor an analog front end (AFE) configured to be powered on and off separately from other portions of the radar sensor; Including, The controller controlling a power cycle of the AFE of the radar sensor at the same frequency as a sampling frequency by turning on the AFE before a sampling time point at which the radar sensor takes a sample and turning off the AFE after the sample has been taken; 7. The subsystem of claim 1, configured to:

8. 1. A system for controlling lighting by motion detection, the system comprising:

10. The subsystem of claim 1 , Including, The subsystem comprises: triggering the lighting device to switch from a standby mode to an active mode when motion is detected; and triggering the lighting device to switch from an active mode to a standby mode if no motion is detected after a first predetermined period of time; a system configured to generate a control signal for:

9. 1. A method for controlling lighting of a lighting device by motion detection, the lighting device operating in both a standby mode and an active mode, the standby mode being when the lamp is off or when the lamp is at a minimum dimming level, and the active mode being when the lamp is at full power or when the lamp is at a dimming state above the minimum dimming level, the method comprising: detecting motion within a detection area with a radar sensor, the radar sensor sampling a derived signal from the detection area at a sampling frequency; setting a sampling frequency of the radar sensor when the lighting device is in standby mode to an initial value that is lower than twice a first Nyquist frequency, the first Nyquist frequency being equal to a first estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in standby mode; setting a sampling frequency of the radar sensor when the lighting device is in a normal operating mode of an active mode to at least twice a second Nyquist frequency, the second Nyquist frequency being equal to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in the active mode; controlling the lighting device based on sensor data obtained by the radar sensor at a specified sampling frequency; A method comprising:

10. The method comprises: generating a control signal for triggering the lighting device to switch from a standby mode to an active mode when motion is detected from sensor data obtained by the radar sensor; 10. The method of claim 9, comprising:

11. The method comprises: setting a sampling frequency of the radar sensor when the lighting device is in standby mode to an increased value compared to the initial value when motion is detected from sensor data obtained by the radar sensor; generating a control signal to trigger the lighting device to switch from a standby mode to an active mode when the detection of motion is confirmed from a new set of sensor data obtained by the radar sensor operating at the increased sampling frequency; resetting the sampling frequency back to the initial value if the motion detection is not confirmed from a new set of sensor data obtained by the radar sensor operating at the increased sampling frequency; 10. The method of claim 9, comprising:

12. The method comprises: sweeping a sampling frequency when the lighting device is in a standby mode to a plurality of different discrete sampling frequencies that are lower than twice the first Nyquist frequency, and setting the sampling frequency to each of the plurality of different discrete sampling frequencies for a second predetermined period to enable stable detection by the radar sensor; recovering a motion-related Doppler frequency signal from aliasing by comparing sets of sub-sampled outputs of sensor data obtained by the radar sensor sampled at each of the plurality of different discrete sampling frequencies; 12. The method of any one of claims 9 to 11, comprising:

13. The method comprises: determining an operation mode of the radar sensor to be either a normal operation mode or a power saving mode according to a power supply condition when the lighting device is in an active mode; The sampling frequency of the radar sensor when the lighting device is in an active mode is at least twice the second Nyquist frequency in the normal operating mode; in a power saving mode, the frequency is lower than twice the second Nyquist frequency; To set up and 13. The method of any one of claims 9 to 12, comprising:

14. The method comprises: deriving detailed motion information by Doppler analysis based on a sampled output of sensor data obtained by the radar sensor when motion is detected, wherein the detailed motion information includes at least one of the number of motion sources, the direction of motion of the motion sources relative to the radar sensor, the speed of motion, and a classification of motion; controlling the lighting device in a more advanced mode in response to the detailed motion information; 14. The method of any one of claims 9 to 13, comprising:

15. A computer program that, when executed by a computer, causes the computer to: Operating the lighting device in both a standby mode and an active mode, wherein the standby mode is when the lamp is off or when the lamp is at a minimum dimming level, and the active mode is when the lamp is at full output or when the lamp is dimmed above the minimum dimming level; receiving samples from a radar sensor detecting motion within a detection area of ​​the radar sensor, the radar sensor sampling derived signals from the detection area at a sampling frequency; setting a sampling frequency of the radar sensor when the lighting device is in standby mode to an initial value that is lower than twice a first Nyquist frequency, the first Nyquist frequency being equal to a first estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in standby mode; setting a sampling frequency of the radar sensor when the lighting device is in a normal operating mode of an active mode to at least twice a second Nyquist frequency, the second Nyquist frequency being equal to a second estimated maximum Doppler frequency of motion to be detected within the detection area by the radar sensor when the lighting device is in the active mode; controlling the lighting device based on sensor data obtained by the radar sensor at a specified sampling frequency; a computer program comprising code means for causing the computer to execute the

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