Patent Publication Number: US-2012046875-A1

Title: Method and system for processing a physiological signal

Description:
FIELD OF THE INVENTION 
     The invention relates to a method of signal processing, including: 
     obtaining at least one physiological signal from a system arranged to monitor at least one user. 
     The invention also relates to a signal processing system, including an interface for obtaining at least one physiological signal from a system arranged to monitor at least one user. 
     The invention also relates to a computer program. 
     BACKGROUND OF THE INVENTION 
     US 2008/0200774 relates to a healthcare system comprising a shell configured to be worn around an ear of a subject. At least one physiological sensor is provided to the shell for measuring and outputting a physiological variable representing a physiological condition of the subject. At least one activity sensor is provided to the shell for measuring and outputting an activity variable representing activity of the subject. At least one environment sensor is provided to the shell for measuring and outputting an environment variable representing the subject&#39;s environment. The system comprises a processing module for processing the physiological, activity and environment variables and for generating an output signal based on the physiological, activity and environment variables. The activity sensors can continuously monitor the subject&#39;s physical activity in XYZ dimensions for motion detection, including fall detection. In an embodiment, the environment sensor outputs an environmental temperature. 
     A problem of the known device is that it only uses motion sensors to interpret the physiological data. This is less of a problem where the object of such a device is to monitor a person&#39;s physical health. However, when it comes to making inferences about a person&#39;s mental state, an interpretation based only on further data characterizing the person&#39;s motion can be inadequate. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a method, system and computer program of the types mentioned above that enable an automated system more accurately to discern between changes in physiological signal values due to changes in a person&#39;s mental state and those due to other influences. 
     This object is achieved by the method according to the invention, which includes: 
     obtaining at least one physiological signal from a system arranged to monitor at least one user, 
     obtaining data at least based on data representative of at least one characteristic of electrical current drawn by at least one appliance in an environment in which the at least one user is present, and 
     using the data to determine an output based on the at least one physiological signal. 
     Physiological signals representative of certain physiological phenomena such as heart rate, skin conductance and changes therein are quite highly correlated to a person&#39;s mental state (mood or emotional state). Thus, obtaining such signals contributes to the accuracy with which an automated system infers a person&#39;s mental state. However, some signal artifacts are due to other influences, for example the type of activity the person is engaging in or has recently engaged in. By obtaining data representative of at least one characteristic of electrical current drawn by at least one appliance in an environment in which the at least one user is present, an inference about the person&#39;s activity can be made. An automated system using the data to interpret the at least one physiological signal is therefore capable of identifying changes in mental state more effectively, and to adjust its output accordingly. 
     In an embodiment, the data representative of at least one characteristic of electrical current is obtained by means of at least one monitoring device for monitoring at least one characteristic of electrical current provided through a socket associated at least temporarily with the monitoring device. 
     This embodiment can be implemented without major adaptation of the electrical appliances in the environment. In particular, the system that processes the physiological signals need not be provided with a communication link to each of the appliances. 
     In a variant of this embodiment, each monitoring device is comprised in an insert, the insert including a plug for insertion in a wall-mounted socket and at least one socket for receiving a power plug of an electrical appliance. 
     This variant can be implemented without major adaptation of the environment, in particular alterations to the mains supply in a building. A further effect is that inferences can be made as to the location or locations of the users in the environment, since a wall-mounted socket has a fixed location, and devices plugged into it via the insert will be within a limited distance of that location under normal circumstances. 
     In a further variant, at least one of the inserts analyses characteristics of current drawn by at least one of a number of appliances drawing current through the insert to identify those of the number of appliances drawing current. 
     This variant is able to cope with power strips connected to the wall-mounted socket via the insert, in that it can distinguish between current use by the individual appliances plugged in to the respective sockets of the power strip. 
     In an embodiment, the data representative of at least one characteristic of electrical current is obtained from each of a number of monitoring devices in association with data identifying the monitoring devices from which they originated. 
     In this embodiment, users can be located, in that the data identifying the monitoring device can include data representative of the monitoring device&#39;s (relative) location or can be cross-referenced to a database associating each identifiable monitoring device with a (relative) location. 
     An embodiment of the method includes: 
     providing a user interface for entering data relating to a monitoring device and 
     storing entered data in association with an identification of the monitoring device to which it relates. 
     This embodiment can be used to locate users in that the data stored in association with an identification of the monitoring device can include data for locating the monitoring device. The embodiment can also be used to make the interpretation of the physiological signal or signals more accurate, because an indication of the types of appliances connected to the monitoring device can be included in the data stored in association with the identification of the monitoring device. Thus, for example, the monitoring device to which a television set is connected can be identified as such. The fact that it is drawing current informs the system executing the method of the fact that someone is watching television. The current levels may even enable the system to infer the volume at which the television is playing. 
     In an embodiment, the data at least based on data representative of at least one characteristic of electrical current is received by a portable device through at least one wireless communications link. 
     In this embodiment, the physiological signals need not necessarily be transmitted over a relatively long range. Instead, a body sensor network can relay physiological signals to a signal processing device that is carried by the user or in close vicinity. The data at least based on data representative of at least one characteristic of electrical current can be communicated to the portable signal processing device over a longer distance. 
     A variant, wherein the data representative of at least one characteristic of electrical current is obtained by means of at least one monitoring device for monitoring at least one characteristic of electrical current provided through a socket associated with the monitoring device, further includes 
     determining a position of a user based on characteristics of wireless communication links between the portable device and each of a number of devices including at least a respective one of the monitoring devices. 
     This variant takes account of the fact that the directionality or strength of wireless signals can be used to advantage to locate a receiver of such signals. 
     An embodiment of the method includes at least one of: 
     a) causing current supply to at least one appliance to be cut off when an absence in the environment of systems for obtaining the at least one physiological signal is detected; and
 
b) causing current supply to at least one appliance to be restored when a presence in the environment of at least one system for obtaining the at least one physiological signal is detected.
 
     This embodiment uses the absence or presence of devices typically carried on the human body in a particular environment as a trigger for switching appliances on and off. An added energy-saving effect is thus obtained using the same components as are used to process physiological signals for the purpose of adapting outputs of devices in that environment. 
     According to another aspect, the signal processing system according to the invention includes: 
     an interface for obtaining at least one physiological signal from a system arranged to monitor at least one user, and 
     an interface for obtaining data from a system for monitoring at least one characteristic of electrical current drawn by at least one appliance in an environment in which the at least one user is present, 
     wherein the signal processing system is configured to use the data to determine an output based on the at least one physiological signal. 
     The system can provide, or cause to be provided, an output more appropriate to the state of the user characterized by the physiological signal values. 
     In an embodiment, the system is configured to carry out a method according to the invention. 
     According to another aspect of the invention, there is provided a computer program including a set of instructions capable, when incorporated in a machine-readable medium, of causing a system having information processing capabilities to perform a method according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in further detail with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an environment in which a body sensor network and current monitors are present; 
         FIG. 2  is a perspective view of an insert including a current monitor; 
         FIG. 3  is a flow chart of a method of initializing a device including a current monitor; and 
         FIG. 4  is a flow chart of a method of processing physiological signals. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an embodiment of a system for interpreting physiological signals, which is arranged to adjust its operation appropriately or causes the operation of an external device to be adjusted appropriately. In particular, the output of the system or external device can be adjusted in a manner appropriate to a particular mental state, especially the mood, of a user. For example, perceptible output of a content rendering device can be adjusted or caused to be adjusted, for example by selecting different content data or by adjusting settings of the device rendering the content data in perceptible form. Similarly, an ambient system can be adjusted at least partly on the basis of the mental state of at least one user as determined by interpreting physiological signals. The outputs of such an ambient system include, depending on the embodiment, at least one of ambient lighting parameters (color, intensity, direction, for example), air flow, temperature, humidity, haptic feedback and the like. 
     In the illustrated embodiment, a user is provided with a portable data processing device  1 , e.g. a Personal Digital Assistant (PDA), smart phone or a dedicated device. The portable device  1  includes a central processing unit  2  and main memory  3 , as well as a data storage device  4  (e.g. a solid state or magnetic non-volatile memory device). In the illustrated embodiment, it also includes a display driver  5  and a display  6 , as well as a user input device  7 , e.g. at least one of a keyboard, pointing device and touch-sensitive device combined with the display  6 . Through these components, the portable device  1  is capable of providing a Graphical User Interface (GUI). 
     The portable data processing device  1  is generally battery-powered. It will generally be carried on the user&#39;s person. The portable data processing device  1  also has a network interface  8  to a personal area network (PAN  9 ), e.g. implemented according to the IrDA, Bluetooth, UWB, Z-Wave or ZigBee standard. 
     Physiological sensors  10 - 12  are also connected to the PAN  9 , through which they provide data representative of at least one respective physiological signal to the portable data processing device  1 . Examples of physiological parameters that can be quantified by the signals include: heart rate, respiration rate, skin conductance, number of skin conductance responses, body temperature, heart rate variability, muscle activity, coherence between the respiration rate and heart rate sinus, etc. These are parameters that have been found to be connected to the mental state, in particular the mood, of a human being. It will be appreciated that the measurements by a physiological sensor  10 - 12  can be contactless or that the sensor  10 - 12  can be maintained in direct contact to the skin, depending on the physiological signal being provided. In one variant, one or more of the physiological sensors  10 - 12  is stationary, but is integrated into the PAN  9  when the portable data processing device  1  is within range. Thus, for example, a sensor  10 - 12  can be included in a chair, and establish contact with a user&#39;s portable data processing device  1  when the user sits down. In another variant, one or more physiological sensors are integrated into the portable data processing device  1 , e.g. pressure sensors integrated into the user input device  7 . 
     The portable data processing device  1  also comprises a second network interface  13 , namely to a second wireless network  14 , which can be a wireless local area network or a wide area network. The second network  14  can include a wireless cellular network or a wireless local area network in accordance with one of the IEEE 802.11x standards. The second network  14  enables the portable data processing device  1  to exchange data with wall-socket inserts  15 - 17 , of which three are shown by way of example in  FIG. 1 . In an alternative embodiment, the wall-socket inserts  15 - 17  communicate by means of a power-line network (e.g. in accordance with the G.hn/G.9960 standard proposal) and a gateway between the second network  14  and such a power-line network. 
       FIG. 2  shows a particular embodiment  18  of a wall-socket insert, which includes a plug  19  for insertion in a wall-mounted socket and a socket  20  replicating the wall-mounted socket, for receiving a power plug (not shown) of an electrical appliance. A button  21  for activating the wall-socket insert  18  is also provided. 
     By way of example,  FIG. 1  illustrates that a first wall-socket insert  15  includes a monitoring device  22  for monitoring at least one characteristic of electrical current drawn by respective electrical appliances  23 , 24  by way of the first wall-socket insert  15 . The first wall-socket insert  15  includes a processing device  25  for processing the measured values and providing data based on these measured values. The data is communicated to the portable data processing device  1  using a network interface  26  to the second network  14 . It is noted that the first wall-socket insert  15  is used to obtain any one of a number of characteristics of the current drawn by the respective appliances  23 , 24 , including voltage, current, power, a moving average of the power consumption, frequency, phase angle between voltage and current, etc. The first wall-socket insert  15  can in particular also detect the presence of patterns in the voltage and/or current. Indeed, such patterns can be used to distinguish between the two electrical appliances  23 , 24 , for example to detect which one is operational or which characteristics (e.g. power consumption) are attributable to which one. The first wall-socket insert  15  of  FIG. 1  also includes a switch  27  for switching the power supply to the electrical appliances  23 , 24  on and off. 
     The other wall-socket inserts  16 , 17  are similar to the first wall-socket insert  15 . In the illustrated example, a third appliance  28  is connected to a second wall-socket insert  16 , whilst no appliance is plugged into a third wall-socket insert  17 . 
     In the illustrated embodiment, the wall-socket inserts  15 - 18  are initialized in the manner indicated in  FIG. 3 . 
     In a first step  29 , the wall-socket insert  15 - 18  is plugged into a wall-mounted socket, or otherwise powered up (e.g. by pressing the button  21 ). The wall-socket insert  15 - 18  polls the wireless network  14  to discover the portable data processing device  1  (step  30 ). 
     The portable data processing device  1  responds (step  31 ) according to a pre-determined protocol to set up a link to the wall-socket insert  15 - 18 . 
     In the illustrated embodiment, it also provides (step  32 ) a Graphical User Interface (GUI) on the display  6 , allowing a user to enter data relating to the wall-socket insert  15 - 18 . This data comprises at least one of a name of the wall-socket insert, one or more names of the electrical appliances  23 , 24 , 28  or of the type thereof connected to the wall-socket insert  15 - 18 , the name or the type of the room in which the wall-socket insert  15 - 18  is provided and the location (e.g. as a point on a compass). 
     Having obtained the user input (step  33 ), the portable data processing device  1  communicates the location and further relevant characteristics to the wall-socket insert  15 - 18  (step  34 ). In another embodiment, the portable data processing device  1  stores this data locally in a database. 
     The wall-socket insert  15 - 18  analyses patterns of power usage by connected electrical appliances  23 , 24 , 28  (step  35 ), learning how to distinguish between the different devices by means of their electrical signature. After this first initialization, the wall-socket insert  15 - 18  stores its settings (step  36 ), whereupon it is ready to provide context information to the portable data processing device  1  with the connected physiological sensors  10 - 12 . The context information provides valuable input for evaluating the psychophysiological signals measured by the body sensor network (BSN) comprising the physiological sensors  10 - 12 . 
     One function that the wall-socket inserts  15 - 18  can also fulfill is an energy-saving function. Having been provided (step  34 ) with information on the types of electrical appliance  23 , 24 , 28  connected to it, the first wall-socket insert  15 , for example, which is provided with a switch  27 , can switch the current supply to the electrical appliances  23 , 24  on and off in dependence on whether a portable data processing device  1  with connected BSN is detected. To this end, the first wall-socket insert  15  can simply poll the network  14  at intervals to determine whether the device  1  is present. If neither it nor a similar device is present, then the current supply is switched off. Once the portable device  1  is detected again, the current supply is restored. The wall-socket insert  15  will fulfill this function only if informed that an appropriate electrical appliance  23 , 24  is arranged to draw current via it (e.g. a lighting appliance or the like). 
     The process of evaluating the psychophysiological signals measured by the body sensor network (BSN) comprising the physiological sensors  10 - 12  is illustrated in outline in  FIG. 4 . The portable data processing device  1  obtains the physiological signals via the PAN  9  (step  37 ). It also determines the location of the user (step  38 ) by multilateration using the wireless signals received from the wall-socket inserts  15 - 18 . Other methods of determining the user&#39;s location are conceivable, but a determination based on characteristics of wireless communication links between the portable data processing device  1  and the wall-socket inserts  15 - 18  requires no additional equipment. 
     The portable data processing device  1  also receives reports of activity from the wall-socket inserts  15 - 18  (step  39 ), which are based on data representative of at least one characteristic of electrical current drawn by any appliances  23 , 24 , 28  connected to the respective wall-socket insert  15 - 18 . For example, one of the wall-socket inserts  15 - 18  can report that a coffee machine or a dish washer is being used, or has just been used. 
     The portable data processing device  1  processes the physiological signals (step  40 ) to determine the mental state, in particular the mood, of the user (step  41 ) and an appropriate response to the mental state in the circumstances (step  42 ). At least one of these steps  40 - 42  makes use of the location and activity information provided in the preceding steps  38 , 39 , to adjust the algorithms that are based on data based on or corresponding to the physiological data. 
     As an example, if the user is determined to be in the vicinity of a television set  43  and the physiological signals indicate frustration, then the signals are interpreted as meaning that the user is watching a program he or she doesn&#39;t like. The appropriate response will be to determine an output that causes a switch to a different channel (step  44 ), and providing an appropriate command to the television set  43  over the second network  14  or another communications link. In another example, the portable data processing device  1  can determine that the user is near a coffee machine (step  38 ). The appropriate output would then be a command to brew a more soothing type of coffee. 
     In another example, the portable data processing device  1  can determine that the user is near a coffee machine (step  38 ) that has just been used (step  39 ). This information is then used to adapt the process of determining the user&#39;s mental state on the basis of the physiological signals (steps  40 , 41 ), depending on the type of physiological signal. It is known, for example, that a person&#39;s galvanic skin response reacts strongly to the intake of caffeine. Thus, in this use case, the first two steps  40 , 41  in the process of providing an appropriate output are adapted to the location and activity data. 
     In yet another embodiment, the portable data processing device  1  can adapt its own output in dependence on the physiological signals using the context information it has received from the wall-socket inserts  15 - 18 , e.g. if it is provided with the resources to render audio tracks in perceptible form. Thus, the portable data processing device  1  can both provide and cause to be provided an output that the user is aware of and that is based on his or her inferred mental state. 
     It should be noted that the above-mentioned embodiments illustrate, rather than limit, the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. 
     In an embodiment, a stationary device is used instead of the portable data processing device  1 . The stationary device establishes a link to a body sensor network comprising at least one physiological sensor and a wireless transceiver when the body sensor network is in range. 
     In that embodiment, or in yet another embodiment, the GUI for providing data associated with current monitoring devices is provided by a stationary device, e.g. the television set  43 , in combination with an appropriate remote control unit (not shown). 
     In another embodiment, a wall-socket insert corresponding to the wall-socket inserts  15 - 18  described above, but adapted for use with analogue telephones and comprising a socket and plug, e.g. according to the RJ11 or BS 6312 standard is used in addition to the wall-socket inserts  15 - 17 , described.