WO2009138955A2

WO2009138955A2 - Indoor child monitoring system

Info

Publication number: WO2009138955A2
Application number: PCT/IB2009/051963
Authority: WO
Inventors: Arvid Randal Nicolaas
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2008-05-14
Filing date: 2009-05-13
Publication date: 2009-11-19
Also published as: WO2009138955A3

Abstract

A monitoring system is disclosed for monitoring a child in a home environment, the system comprising a wireless sensor unit and a plurality of tag units. The wireless sensor unit comprises distance measurement means for measuring a distance from the wireless sensor unit to a tag unit, a logic unit configured to compare the measured distance to the tag unit with an operating range for the tag unit, and an alarm unit configured to alert a user of the wireless sensor unit in the event that the measured distance is less than or equal to the operating range.

Description

Indoor child monitoring system

FIELD OF THE INVENTION

The present invention relates to a child monitoring system, and more specifically, to a child monitoring system to monitor a child in an indoor environment.

BACKGROUND OF THE INVENTION

Parents would like to allow their children to freely move and play in a home environment, but the home environment contains many objects which may pose a danger to an unsupervised child. One of the main purposes of parental supervision may be to ensure that a child only plays in safe areas of the home, and in particular that they do not stray too close to or attempt to play with dangerous objects. However, it is not practical for a parent to pay close attention to their children 100% of the time, yet the consequences of a simple slip of attention may be dramatic; for example, a child may touch the hot surface of an oven and consequently suffer burns, or the child may fall down a staircase and suffer an injury.

Hence, it would be advantageous to have an indoor child monitoring system that is capable of warning a child when they approach a dangerous object, without requiring parental intervention, and also capable of detecting when an accident has occurred and alerting a parent of the child, so that early treatment may be provided for any injury sustained during the accident. By issuing a warning to a child every time they approach a potentially dangerous object, such a system may be used over time to train a child to associate certain objects with a danger signal. This may advantageously result in the child making the association that similar objects may be dangerous, and self-regulating their own behavior accordingly in environments not monitored by the system.

US patent document 2007/0132578 discloses a system for monitoring people in swimming pools and other similar environments.

SUMMARY OF THE INVENTION

The present invention aims to address the drawbacks inherent in known arrangements. According to the present invention, there is provided a wireless sensor unit according to claim 1, a monitoring unit according to claim 9, an operating range setting unit according to claim 12, a method of alerting a user of a wireless sensor unit according to claim 20, a wireless wearable child unit according to claim 25, and a wireless parent unit 26. According to the present invention, there is provided a wireless sensor unit comprising distance measurement means configured to measure a distance from the wireless sensor unit to a tag unit; a logic unit configured to compare the measured distance to the tag unit with an operating range for the tag unit; and an alarm unit configured to alert a user of the wireless sensor unit in the event that the measured distance is less than or equal to the operating range. The wireless sensor unit can therefore detect when a child wearing the wireless sensor unit approaches closer to a tag unit than an operating range for the tag unit, and automatically provide a warning to the child without requiring parental intervention.

The wireless sensor unit may further be configured to receive operating range data from the tag unit. Each tag unit may thus have an individual operating range as appropriate for an object to which the tag unit is attached.

The wireless sensor unit may further comprise a communications unit, the logic unit being configured to control the communications unit to transmit an alert message to a monitoring unit in the event that the measured distance is less than or equal to the operating range. In this way, a parent using the monitoring unit may be informed when the child has approached closer to a tag unit than an operating range for the tag unit.

The wireless sensor unit may further comprise a plurality of sensors configured to measure at least one of environmental and physiological parameters, the logic unit being configured to compare an output from each sensor to at least one threshold value for said sensor, and further configured to control the transmitter to transmit an alert message to the monitoring unit in dependence on the result of said comparison. These sensor units may therefore be used to monitor the child's health and environment in real-time, and a parent using the monitoring unit may be notified as soon as any of the measured parameters deviate from a predetermined safe range of values. This may allow early detection of an accident or injury suffered by the child, and enable the parent to respond promptly. The wireless sensor unit may yet further comprise an audio/video unit, the wireless sensor unit being configured to transmit at least one of audio and video signals to the monitoring unit.

The wireless sensor unit may be configured to be worn by the user. The wireless sensor unit may yet further comprise a power supply and an induction coil, the induction coil being operable in conjunction with an induction coil of a charging unit to charge the power supply.

The distance measurement means may further comprise an ultrasonic transducer and a radio-frequency communication unit.

According to the present invention, there is also provided a monitoring unit comprising a communications unit configured to receive an alert message from a wireless sensor unit; an alarm unit; and a logic unit configured to control the alarm unit to alert a user of the monitoring unit in response to the received alert message. The monitoring unit may further comprise a user interface unit configured to reproduce at least one of an audio signal and a video signal received from the wireless sensor unit.

The monitoring unit may yet further comprise a power supply and an induction coil, the induction coil being operable in conjunction with an induction coil of a charging unit to charge the power supply.

According to the present invention, there is also provided an operating range setting unit comprising operating range user input means configured to receive an operating range selected by a user; a communications unit; and a logic unit configured to control the communications unit to transmit said received operating range to a tag unit. The operating range setting unit may further comprise a power supply and an induction coil, the induction coil being operable in conjunction with an induction coil of a charging unit to charge the power supply.

According to the present invention, there is also provided a monitoring system comprising a plurality of tag units each having a preset operating range; and at least one wireless sensor unit.

The monitoring system may further comprise at least one of a monitoring unit and an operating range setting unit.

The monitoring system may comprise an operating range setting unit and a monitoring unit provided in the same physical device. The tag units may be active radio -frequency tags.

Each one of the tag units may further comprise an ultrasonic transducer arranged to transmit an ultrasonic signal to the at least one wireless sensor unit.

Additionally, each one of the plurality of tag units may include operating range setting means for inputting an operating range of the tag unit. According to the present invention, there is also provided a method of alerting a user of a wireless sensor unit, the method comprising measuring a distance from the wireless sensor unit to a tag unit, comparing the measured distance to the tag unit with an operating range for the tag unit, and alerting a user of the wireless sensor unit in the event that said measured distance is less than or equal to said operating range.

The method may further comprise transmitting an alert message to a monitoring unit in the event that the measured distance is less than or equal to the operating range.

The method may further comprise the operating range for the tag unit being an operating range selected by a user.

The step of alerting a user of the wireless sensor unit may comprise controlling an alarm unit to generate at least one of an audible warning sound or a physical vibration.

The step of measuring the distance from the wireless sensor unit to the tag unit may further comprise controlling the tag unit to transmit a radio-frequency signal and an ultrasonic signal in synchronization with each other to the wireless sensor unit, measuring a time difference between arrival of the radio-frequency signal and arrival of the ultrasonic signal at the wireless sensor unit, and calculating the distance travelled by the ultrasonic signal on the basis of the measured time difference. Since ultrasonic waves cannot penetrate solid objects such as floors, walls, or ceilings, this has the benefit that distances can only be measured to tag units in the same room as the child wearing the child unit 102; hence, only tag units in the same room as the child may cause an alarm to be activated.

According to the present invention, there is also provided a wireless wearable child unit comprising a distance measurement unit configured to periodically measure the distance between the child and a wireless proximity tag to an object; a logic unit configured to check whether the child is within the desired operating range based on the measured distance; and an alarm unit configured to activate an alert message if the child is within the set desired operating range.

According to the present invention, there is further provided a wireless parent unit comprising receiving means to receive an alert message from a wireless wearable child unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of reference to the accompanying drawings, in which: Figure 1 schematically illustrates a child monitoring system according to an embodiment of the present invention;

Figure 2 schematically illustrates a child unit and a tag unit attached to an object, according to an embodiment of the present invention; Figure 3 schematically illustrates the structure of a tag unit according to an embodiment of the present invention;

Figure 4 schematically illustrates the structure of a child unit according to an embodiment of the present invention;

Figure 5 schematically illustrates the structure of a charging unit according to an embodiment of the present invention;

Figure 6 schematically illustrates a child monitoring system according to an alternative embodiment of the present invention;

Figure 7 schematically illustrates the structure of a parent unit according to an embodiment of the present invention; Figure 8 schematically illustrates the structure of a child unit according to an alternative embodiment of the present invention;

Figure 9 schematically illustrates the structure of an operating range setting unit according to an embodiment of the present invention;

Figure 10 schematically illustrates the structure of a tag unit according to an embodiment of the present invention;

Figure 11 is a flow diagram illustrating the steps performed in measuring distances from a child unit to a plurality of tags and determining whether any tags are closer than their operating range, according to an embodiment of the present invention;

Figure 12 is a flow diagram illustrating the steps performed in setting an operating range of a tag unit according to an embodiment of the present invention;

Figure 13 is a flow diagram illustrating the steps performed in using sensor outputs to determine whether to transmit an alarm to a parent unit, according to an embodiment of the present invention; and

Figure 14 schematically illustrates a structure of a child unit according to an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to Figure 1 , a child monitoring system according to an embodiment of the present invention comprises a wireless, wearable child unit 102 (hereinafter referred to as a "child unit") in wireless communication with a plurality of tag units 104, 106, 108, 110, 112. The child unit 102 is configured to be worn by a child, and detect when the child approaches closer than a preset safe distance to any of the tag units 104, 106, 108, 110, 112. The tag units 104, 106, 108, 110, 112 are themselves secured to various objects around the home which may pose a risk of injury to a child, such as an electric iron 114, kitchen knife 116, fireplace 118, washing machine 120 and food processor 122.

A home environment typically comprises a plurality of objects, appliances, furniture etc. which may pose a danger to a child as they play and move around in the home. According to the present invention, a parent identifies the objects that may pose a danger to the child, and secures wireless tag units onto such objects. A tag unit can be removably fixed at a suitable position on an object. Examples of such objects are found in Figure 1 (objects 114, 116, 118, 120, 122); other types of hazardous objects to which a parent may wish to attach tag units include, but are not limited to, microwave ovens, electric hot plates used in the kitchen, electric gadgets, or tools such as scissors, shaving blades and drills. Each tag unit 104, 106, 108, 110, 112 has an associated operating range, the operating range being used to define a region around the tagged object, within which there is a risk of injury to the child. In the present example, the operating range is a default value stored in the tag unit itself; the plurality of tag units may be divided into groups having different default operating ranges, such that the parent can select a tag unit with an appropriate default operating range for the object to which the tag unit is to be attached. In alternative embodiments the operating range may be a default value stored in the child unit 102; a user-defined value set by the parent and stored in the tag unit; or a user-defined value stored in the child unit 102, in which case the child unit 102 should be provided with means for setting the operating range. In the present example, the tag units 104, 106, 108, 110, 112 are similar to active radio -frequency identification (RFID) tags, with the addition of ultrasonic transducers which are used when measuring a distance to each tag unit. A parent or guardian of a child affixes the tag units 104, 106, 108, 110, 112 to objects 114, 116, 118, 120, 122 in the home environment which may pose a danger to the child. The child unit 102 is configured to periodically measure the distance from itself to each tag unit 104, 106, 108, 110, 112, and to activate an alert mechanism if it is detected that the child approaches any tag unit closer than the set operating range for that tag unit.

Figure 2 schematically illustrates a situation in which the child unit 102 communicates with a tag unit 104 according to an embodiment of the present invention. In the present example, the child unit 102 is provided with a strap and designed to be attached on a convenient position on the child's body, such as around the wrist of a child 202. In alternative embodiments, the child unit 102 may be provided with other attachment devices such as bands, clips, ties, buttons and buckles. Alternatively, the child unit 102 can be integrated into the child's clothing.

The tag unit 104 is attached to an object 204; in the present example, the object 204 is a filing cabinet, but as previously discussed, it is envisaged that tag units may be affixed to any object as required.

In the present example, the tag unit 104 is attached to the filing cabinet 204 by a magnet integral to the tag unit 104, but alternative fixing methods may be substituted as required for different objects. The child unit 102 is configured to communicate wirelessly with the tag unit 104, and to measure a distance d to the tag unit 104.

Referring now to Figure 3, a structure of a tag unit 104 is schematically illustrated, according to an embodiment of the present invention. The tag unit 104 comprises tag securing means 302, and a power supply 310 supplying power to each of an antenna 304, a memory 306, an ultrasonic transducer 308, a logic unit 312, and a low-battery indicator 314. In the present example, the tag securing means 302 comprises a magnet for affixing the tag unit 104 to metallic objects capable of being magnetized, such as the filing cabinet 204 of Figure 2; however, other securing means such as Velcro or adhesive pads are well-known in the art and may readily be substituted. Also in the present example, the memory 306 is a nonvolatile computer-readable and rewritable memory such as a Flash memory chip. The memory stores a unique ID number for the tag unit 104, and may further be configured to store an operating range for the tag unit 104. Still in the present example, the power supply 310 is provided as a conventional battery, which may have a lifetime of several years since only a low current is required to power the components of the tag unit 104. The battery may be sealed into the tag unit, or may be provided in a user-accessible compartment in order that a user can replace the battery when needed.

Also in the present example, the low-battery indicator 314 is provided as an LED, which is configured to only be illuminated when the stored power in the battery drops below a preset level. In an alternative embodiment, the logic unit 312 may be configured to periodically measure a power level of the power supply 310, and a child unit 102 or a parent unit 602 (see later embodiments) may be used to periodically contact each tag unit to check its power level, alerting a user if the power level of a tag unit falls below a preset level. The logic unit 312 may control the antenna 304 and the US transducer 308 to both transmit and receive radio-frequency (RF) and ultrasonic (US) signals respectively. In the present example, a combination of RF and US signals are used when measuring a distance from the tag unit 104 to a child unit 102, as will be described later. However, other methods of wireless distance measurement are known in the art; in the event that an alternative wireless distance measurement technology is used, different transmitters and receivers may be substituted for the antenna 304 and US transducer 308 as required.

Referring now to Figure 4, a structure of a child unit 102 is schematically illustrated, according to an embodiment of the present invention. The child unit 102 comprises a power supply in the form of a battery 406, for which there is provided an induction coil 408 for charging the battery 406 wirelessly, i.e. without a wired connection between a charging unit and the battery 406. The child unit 102 further comprises a logic unit 404 for controlling various other components, the logic unit being connected to a distance measurement unit 402 for measuring distances to a plurality of tag units (not shown), an alarm unit 410 for activating an alarm in the event that a measured distance to a given tag unit is less than or equal to a set operating range for that tag unit, and a low-battery indicator 420. In the present example, the low-battery indicator 420 is provided as an LED, which is configured to only be illuminated when the stored power in the battery 406 drops below a preset level. In the present example, the alarm unit 410 comprises a conventional speaker for playing a sound to attract the child's attention and inform them that they are too close to a hazardous object. Alternative embodiments may employ other techniques to prevent the child approaching any closer to the hazardous object; for example, playing a sound in order to draw the attention of the child to another object such as a toy, playing a song or rhyme, or alternatively generating a loud noise that encourages the child not to approach closer to the object. In further embodiments, the alarm unit comprises an electric motor instead of or as well as the conventional speaker, to cause the child unit 102 to vibrate as an alert mechanism; for example, this may be particularly desirable when the child is partially or completely deaf. The distance measurement unit 402 further comprises a distance measurement control unit 416 connected to the logic unit 404, as well as an US transducer 414 and RF communication unit 418 connected to the distance measurement control unit 416. In order to measure a distance to a tag unit 104, the distance measurement control unit 416 controls the RF communication unit 418 to transmit an RF signal to the tag unit 104. In the present example, since there may be a plurality of tag units within a transmission range of the child unit 102, the RF signal transmitted by the RF communication unit 418 contains an ID of the tag unit for which it is desired to measure a distance. Accordingly, each one of the plurality of tag units is arranged to only respond to received RF signals which contain its own unique ID. The tag unit 104 receives the signal, and in response transmits both an RF signal and an US signal, which are received by the RF communication unit 418 and US transducer 414 respectively. Since the travel time for the RF signal is negligible in comparison to the travel time of the US signal, it can be assumed that the time of reception of the RF signal by the RF communication unit 418 corresponds to the time of transmission of the US signal by the tag unit 104. The difference in arrival times of the RF and US signals at the distance measurement unit 402 can then be taken as the travel time of the US signal, and since the propagation speed of an US wave in air is known, a distance travelled by the US signal can be calculated by the distance measurement control unit 416. In the present example, the RF signal transmitted by the tag unit 104 contains information about the operating range for the tag unit 104, so that the child unit 102 can compare the measured distance with the operating range.

Although in the present example the RF and US signals are transmitted simultaneously by the tag unit 104, the signals may alternatively be transmitted separately. In this case, the child unit 102 must have access to information regarding the time interval between the transmissions; this may either be a predetermined time known to both the tag unit 104 and child unit 102, or a time selected by the tag unit 104 and communicated to the child unit 102 in the RF transmission.

Using ultrasonic distance measurement may give several benefits over alternative RF-based distance measurement methods. For example, since the travel time of an US wave (e.g. 1 ms for 34 cm) is long compared to the operating speeds of electronics (typically ns or μs), the travel time and distance travelled may be calculated with a high degree of accuracy. Additionally, the US waves cannot penetrate walls, ceilings, or floors, meaning that US waves are confined to the room occupied by the tag unit; hence, only tag units in the same room as the child unit 102 may activate an alarm. Nonetheless, the present invention is not limited to the US method of distance measurement; various other methods of wireless distance measurement are known in the art, including but not limited to: multilateration; received signal strength; and RFID-radar. The person skilled in the art will substitute appropriate components for the US transducer 414 and RF transmitting unit 418 of the distance measurement unit 402, as required by their chosen technique.

Referring now to Figure 5, a structure of a charging unit 502 is schematically illustrated, according to an embodiment of the present invention. The charging unit 502 is provided for wirelessly charging the battery 406 of the child unit 102.

As shown in Figure 5, the charging unit 502 comprises a recess 504 for receiving the child unit 102, the child unit 104 comprising a battery 406 connected to an induction coil 408 and a plurality of other components 402, 404, 410, 420. The charging unit 502 further comprises an induction coil 506 connected to a power conversion unit 508, the power conversion unit 508 being configured to connect to a mains power supply 510 and convert the alternating current mains power into a waveform suitable to be supplied to the induction coil 506.

The charging unit 502 and child unit 102 are designed such that when the child unit 102 is seated in the recess 504 of the charging unit 502, the induction coils 408 and 506 are brought into close proximity. The induction coils then function as a conventional transformer, with an alternating current in induction coil 506 inducing an alternating current in induction coil 408 which may be used to charge the battery 406.

Referring now to Figure 6, a child monitoring system according to a further embodiment of the present invention comprises a wireless, wearable parent unit 602 (hereinafter referred to as a "parent unit") in addition to the child unit 102 and plurality of tag units 104, 106, 108, 110, 112. The parent unit 602 is designed to be worn by a user, typically a parent or guardian of the child, in a manner similar to the child unit 102; the parent unit 602 may receive information from the child unit 102 and thereby allow the user to monitor the child's status from a remote location. In an alternative embodiment, the parent unit 602 may connect to a plurality of child units (not shown) to monitor a plurality of children. For attaching the parent unit 602 to a user, various attachment means such as bands, clips, ties, buttons and buckles may be provided, or the parent unit 602 may be integrated into the user's clothing.

In this example, the child unit 102 and plurality of tag units 104, 106, 108, 110, 112 function in a substantially similar manner to that described previously (see Figure 1 and earlier description), whilst the child unit 102 communicates with the parent unit 602 in addition to the plurality of tag units 104, 106, 108, 110, 112.

As in the previously described example, the child unit 102 is configured to periodically measure the distance from itself to each tag unit 104, 106, 108, 110, 112 and to activate an alert mechanism if it is detected that the child approaches any tag unit closer than an operating range for that tag unit. In the present example, when the alert mechanism is activated, the child unit 102 may also select to transmit an alert message to the parent unit 602, notifying a user of the parent unit 602 that an alarm has been activated as a result of a child straying too close to a tagged hazardous object.

Figure 7 schematically illustrates a structure of a parent unit 602, according to an embodiment of the present invention. Like the child unit 102, the parent unit 602 comprises a power source in the form of a battery 706, for which there is provided an induction coil 708 for charging the battery 706 wirelessly, i.e. without a wired connection between the charging unit 502 and the battery 706. It is envisaged that the parent unit 602 is configured such that the battery 706 may be charged by the same charging unit 502 as previously described in Figure 5 for charging the child unit 102.

The parent unit 602 further comprises a logic unit 704 for controlling various other components, the logic unit connected to a communications unit 702 for communicating with a child unit (not shown), an alarm unit 712 for activating an alarm in response to a signal received from the child unit, and a low-battery indicator 714. In the present example, the low-battery indicator 714 is provided as an LED, which is configured to only be illuminated when the stored power in the battery 706 drops below a preset level. The parent unit 602 further comprises user interface components 710 allowing the parent to control various functions of the parent unit 602; note that such user interface components are not present in the example embodiment of a child unit shown in Figure 4, since it is envisaged that young children would not understand how to control functions of the child unit.

In the present example, the user interface components 710 comprise a display allowing the user of the parent unit 602 to view information transmitted from a child unit 102; for example, an ID associated with the child unit 102 in the case that the parent unit 602 is used to monitor a plurality of child units worn by different children (e.g. 'child John'). Information displayed at the parent unit 602 may further comprise detailed information about the transmission received from the child unit 602, such as the ID of the nearest tag unit to the child unit 102 at the present time. Referring now to Figure 8, a structure of a child unit 102 is schematically illustrated, according to an embodiment of the present invention. The components 402, 404, 406, 408, 410 and 420 function in a manner substantially similar to the components 402, 404, 406, 408, 410 and 420 previously described with reference to Figure 4. However, in this embodiment the child unit 102 further comprises a plurality of sensor units 802, 804, and a communications unit 806. Such an embodiment of a child unit 102 may be provided for use in conjunction with a parent unit 602, since outputs from the sensor units 802, 804 may be transmitted via the communications unit 806 to the parent unit 602. This allows the parent using the parent unit 602 to build a more complete picture of the child's current environment and situation.

The sensor units 802, 804 may comprise any environmental or physiological sensor, for detecting changes in environmental conditions which may either result in injury to a child, or changes in physiological parameters which may be indicative of an injury to the child. Examples of possible sensors include but are not limited to, 3D accelerometers, fluid sensors, temperature sensors, oxygen sensors, gas compound sensors, voltage or current meters, microphones, position sensors, heart rate sensors, and light sensors.

In addition to the distance measurement, this embodiment provides sensors to sense other parameters that may be indicative of an injury or a risk of injury to the child. As an example, a child may fall down and suffer an injury whilst trying to sit on a chair; a position sensor can sense the body position of the child, and an accelero meter and/or air- pressure sensor can sense the child falling. The outputs from these sensors may be analyzed together with the outputs from physiological sensors (e.g. heart rate sensor, body temperature sensor), in order to determine whether the child has suffered an injury as a result of falling. Based on the result of such an analysis of sensor outputs, the logic unit 404 may determine that it is necessary to transmit an alert message to the parent unit 602.

Figure 9 schematically illustrates a structure of an operating range setting unit 902, according to an embodiment of the present invention. Such an operating range setting unit 902 may be provided for use with either of the systems illustrated in Figures 1 and 6, to allow a user to independently set an operating range for each individual tag unit. Like the child unit 102 and the parent unit 602, the operating range setting unit

902 comprises a power source in the form of a battery 906, for which there is provided an induction coil 908 for charging the battery 906 wirelessly, i.e. without a wired connection between the charging unit 502 and the battery 906. It is envisaged that the operating range setting unit 902 is configured such that the battery 906 may be charged by a charging unit 502 as previously described in Figure 5 for charging the child unit 102.

The operating range setting unit 902 further comprises a logic unit 904 connected to a communications unit 912, a distance measurement unit 910, and a plurality of user interface components 914. The plurality of user interface components 914 further comprise an operating range input unit 916, a tag deactivation input unit 918, and a selected tag indicating unit 920. The distance measurement unit 910 may comprise similar components to the distance measurement unit 402 of the child unit 102. In the present example, the selected tag indicating unit 920 is provided as a conventional alphanumeric LCD, and the operating range input unit 916 and tag deactivation input unit 918 are provided as push-buttons. However, the person skilled in the art may readily substitute alternative components as appropriate, such as analogue or digital dials, touch screens, LEDs etc. The operating range setting unit 902 further comprises a low-battery indicator 922; in the present example, the low-battery indicator 922 is provided as an LED, which is configured to only be illuminated when the stored power in the battery 906 drops below a preset level. The operating range setting unit 902 is controlled by a user in order to communicate with a plurality of tag units and set an individual operating range for each tag unit. An appropriate operating range for a tag unit may be chosen by the user depending on the object to which that tag unit is attached; for example, in the case of an open fireplace, a minimum safe distance from the fireplace for a child may be judged to be 1 m, in which case a user sets the operating range for a tag unit affixed to or near the fireplace as 1 m. However, for other objects a lower operating range may be deemed appropriate, in order to provide the child with a greater freedom of movement around the home environment; for example, a minimum safe distance from a food processor may be judged to be 0.5 m, in which case an operating range of a tag unit affixed to the food processor may be set accordingly. The tag deactivation input unit 918 may be controlled by a user to deactivate a selected tag unit, when that tag unit is no longer required. In the present example, this is achieved by setting the operating range of that tag unit to zero, meaning that the tag unit will never trigger an alarm, but alternative methods of deactivating tags may readily be substituted. A method by which the operating range setting unit 902 may be controlled by a user to set an operating range of a tag unit, will be described later with reference to Figure 12.

Although in the present example the operating range setting unit 902 is illustrated as a separate unit to the parent unit 602, in an alternative embodiment the components and functionality of the operating range setting unit 902 may be integrated into the parent unit 602. Referring now to Figure 10, a structure of a tag unit 1002 is illustrated according to an alternative embodiment of the present invention. As in the examples discussed above, the tag unit 1002 is similar to an active RFID tag, and comprises tag securing means 302, an antenna 304, a memory 306, an US transducer 308, an internal power supply 310, a logic unit 312 and a low-battery indicator 314. The tag unit 1002 further comprises a user interface 1004 to allow the user to set an operating range of the tag unit 1002 directly at the tag unit 1002 itself; this obviates the need in this embodiment for an operating range setting unit 902, although one may optionally be provided to allow users to change the operating ranges of any tag units affixed in inaccessible locations. Various forms may be chosen for the user interface 1004, including but not limited to LCDs, push buttons, switches and dials.

Referring now to Figure 11 , a method is illustrated for measuring distances from a child unit 102 to a plurality of tag units and determining whether any tag units are closer than their operating range, according to an embodiment of the present invention. Such a method is performed periodically at the child unit 102 in order to check whether the child wearing the child unit 102 has approached too close to any tag units within range.

Initially, the child unit 102 obtains a list of nearby tag units (step 1102). In the present example, this is achieved by transmitting an open (i.e. addressed to all tag units) identification request which is received by any tag units within transmission range. Any tag unit receiving the request accordingly transmits a response containing its ID and operating range to the child unit 102, which stores the received ID and operating range in a list of nearby tag units.

The child unit 102 then proceeds to select the first tag unit from the list obtained previously (step 1104), selecting a tag unit comprising controlling any subsequent operations to be performed for the tag ID and operating range of the selected tag unit. The distance measurement unit 402 of the child unit 102 then measures the distance to the tag unit selected in step 1104 (step 1106).

As discussed earlier, in the present example the distance measurement is performed by measuring the travel time of an ultrasonic signal transmitted from the tag unit to the child unit 102. Since ultrasonic waves cannot penetrate solid objects such as floors, walls, or ceilings, distances can only be measured to tag units in the same room as the child wearing the child unit 102; hence, only tag units in the same room as the child may cause an alarm to be activated.

However, since RF signals can penetrate solid objects, the list generated in step 1102 may comprise tag units in different rooms to the child unit 102. In this event, during distance measurement for such tag units no ultrasonic signal will be detected by the child unit 102, but the RF signal will be received. The distance measurement unit 402 of the child unit 102 may therefore be arranged to wait for a predetermined time after the expected transmission time of the ultrasonic signal, and if no ultrasonic signal is detected during this time, determine that the tag unit is in a different room.

This predetermined time may be chosen based on the time taken for an ultrasonic wave to travel a distance corresponding to a maximum desired operating range. For example, if the maximum desired operating range is 5 m, and taking the speed of sound as 340 m/s, then the predetermined time should be set to be 5/340 s, i.e. 15 ms. If no ultrasonic signal has been received by the predetermined time, the tag unit may be removed from the list generated in step 1102, and the next tag unit selected instead for distance measurement. Next, the operating range for the selected tag unit is retrieved from the list generated in step 1102 (step 1108), and the logic unit 404 of the child unit 102 compares the measured distance with the operating range (step 1110). In the event that the measured distance is greater than the operating range, it is determined that the child wearing the child unit 102 is at a safe distance from the selected tag unit, and the process continues to step 1114. However, in the event that the measured distance is less than or equal to the operating range, it is determined that the child wearing the child unit 102 is dangerously close to the object to which the selected tag unit is attached, and accordingly an alarm is activated (step 1112), before continuing to step 1114.

It is then determined whether there are any more tag units in the list, i.e. whether the currently selected tag unit is the last tag unit in the list (step 1114). In the event that there are no more tag units remaining in the list, the process is complete, but if there are further tag units in the list then the next tag unit in the list is selected (step 1116). The process then returns to step 1106 and continues as before.

This method enables the child unit 102 to periodically contact all tag units within transmission range and determine whether the child has strayed dangerously close to any hazardous object marked by a tag unit.

In an alternative embodiment of the method, the child unit 102 may be configured to wait for a predetermined time after determining that a measured distance to a tag unit is less than the operating range (step 1110), and measure the distance again. The alarm is then only activated (step 1112) if the measured distance is still less than the operating range. This embodiment may prevent an alarm being activated when a child simply walks by a dangerous object. In a further embodiment, this predetermined time may be linked to danger level information (see description of Figure 13), so that an alarm is only activated immediately when a child approaches an object posing a high risk of injury; for tag units with lower danger levels, the child may have to remain near the object for a longer time in order to activate an alarm.

Referring now to Figure 12, a method is illustrated for setting an operating range of a tag unit according to an embodiment of the present invention. The method steps are divided between those performed at an operating range setting unit 902 and a tag unit 104.

In the first step, the operating range setting unit 902 generates a list of nearby tag units (step 1202); this can be achieved by a method similar to that used in step 1102 of Figure 11 , as described previously. Next, the operating range setting unit 902 measures the distance to each tag unit (step 1204), and sorts the list of tag units according to measured distance from the operating range setting unit 902. The logic unit 904 of the operating range setting unit 902 then selects the tag unit with the lowest measured distance (i.e. the closest tag unit) (step 1206), and controls the selected tag indicating unit 920 to display the ID of the selected tag unit (step 1208). These steps have the effect of causing the operating range setting unit 902 to automatically locate and select the closest tag unit, and display the ID of the closest tag unit to a user. In an alternative embodiment, the operating range setting unit 902 may be provided with a user interface to allow a user to view the list of nearby tag units and select any tag unit from the list. Next, the user enters a desired operating range for the currently selected tag unit, using the operating range input unit 916 (step 1210). The logic unit 904 controls the communications unit 912 to transmit this operating range to the tag unit step 1212), and the tag unit receives the transmission (step 1214). The desired operating range can be selected based on several factors such as: the type of the object; the age of the child; the level of security needed; the level of safety needed; the type of danger involved with the object; and the child's affinity to play with the object.

The tag unit 104 stores the received operating range in its internal memory 306 (step 1216), replacing any pre-existing stored operating range for that tag unit 104. Next, the tag unit 104 transmits a confirmation message to the operating range setting unit 902 to confirm that the stored operating range has been changed (step 1218).

Finally, the operating range setting unit 902 receives the confirmation message from the tag unit 104 (step 1220), and displays confirmation to the user (step 1222). In the present example, in which the selected tag indicating unit 920 is provided as an LCD display, the confirmation message may be displayed to the user via this same LCD display. In an alternative embodiment of the method illustrated in Figure 12, the operating range setting unit 902 may be configured to wait for a preset time for a confirmation message to be received from a tag unit in step 1220, and if no confirmation message is received, repeat step 1212 to retransmit the operating range to the tag unit. In a further embodiment, the operating range setting unit 902 may be configured to notify the user that the operating range setting operation has failed, if no confirmation message is received after a preset number of transmission attempts.

Referring now to Figure 13, a flow diagram is provided illustrating the steps performed at a child unit in determining whether to transmit an alert message to a parent unit, according to an embodiment of the present invention. The first step 1302 encompasses the method illustrated in Figure 11, with the additional features of receiving and storing danger level data from each tag unit at step 1102, and recording the ID of any tag unit which causes an alarm to be activated at step 1112.

Danger level data is stored in the memory of each tag unit, and corresponds to a preset danger level for each tag unit. A danger level is indicative of the level of risk associated with an object to which the tag unit is attached; for example, a low danger level may be associated with a low-risk object such as a sofa, whilst a high danger level may be associated with a high-risk object such as a drawer containing kitchen knives. In the present example, the danger level is a preset default value for each tag unit; that is, a range of tag units are provided corresponding to a range of danger levels, the user selecting a tag unit with an appropriate danger level to be attached to an object, based on the level of risk associated with that object. In an alternative embodiment, the danger level may be set by a user in a manner similar to the operating range setting method of Figure 12.

Once the process of step 1302 is complete, the logic unit 404 of the child unit 102 determines whether any ID data was recorded in step 1302, i.e. whether any of the tag units activated an alarm (step 1304). In the event that no alarms were activated, the process continues directly to step 1312, but if any alarms were activated, the process continues to step 1306.

Next, for each tag unit which activated an alarm in step 1302, the danger level of that tag is compared with a threshold danger level (step 1306). The threshold danger level is stored at the child unit 102, and is used to determine whether the risk associated with a tag unit activating an alarm is sufficiently high that the parent unit 602 should be notified. For example, in the case of a drawer containing kitchen knives, there is a high probability that a child will be injured if they approach close enough to open the drawer and pick up a knife; hence, a user of the parent unit 602 may wish to be notified immediately that the child approaches closer to the drawer than a preset operating range for the tag unit attached to the drawer, and so would choose a tag unit with a danger level higher than the threshold danger level of the child unit 102. However, in the case of a low-risk object such as a sofa, a parent may decide that although they want to attach a tag unit to the sofa to prevent the child approaching and climbing on the sofa unsupervised, the actual injury risk associated with a child approaching the sofa is quite low. In this case the parent does not wish to be notified merely when the child approaches the sofa, since the likelihood that the child has actually sustained an injury and requires attention is low. In the present example, a user of the parent unit 602 sets the threshold danger level by controlling the parent unit 602 via the user interface 710 to transmit a threshold danger level to a child unit 102. However, the person skilled in the art will recognize that other methods of setting the threshold danger level may be substituted, for example providing the child unit itself with means to set the threshold danger level. Alternatively, the threshold danger level may be a default value which is not able to be changed by a user.

It will be readily apparent that by varying the threshold danger level, a user of the parent unit 602 can restrict the number and frequency of transmissions from a child unit 102 to the parent unit 602. This may help to conserve power at both units, and may also reduce the likelihood of the user of the parent unit 602 being alerted when the child 202 has not actually suffered an injury.

Accordingly, if it is determined that none of the tag units activating an alarm in step 1302 have a danger level above the threshold danger level (step 1308), no alert message is transmitted to the parent unit and the process proceeds directly to step 1312. However, in the event that at least one of the tag units activating an alarm in step 1302 has a danger level exceeding the threshold danger level, the process proceeds to transmit an alert message to the parent unit (step 1310), before continuing to step 1312. In the present example, the alert message contains information on the individual tag units which activated an alarm and which have a danger level exceeding the threshold danger level, and also contains information identifying the child unit 102 which transmitted the alert message. However, other formats may readily be substituted for the alert message as required; for example, the alert message may simply cause an alarm at the parent unit to be activated.

The logic unit 404 of the child unit 102 proceeds to compare the outputs from each of the plurality of sensor units 802, 804 with minimum and maximum threshold levels for each sensor unit (step 1312). These threshold levels are stored at the child unit 102. For example, in the case of a heart rate monitor, the maximum and minimum threshold levels define a range of safe values; if the child's heart rate deviates from this safe range, it is determined that the child is injured or unwell, and that the user of the parent unit 602 should be notified. Thus, if it is determined that the output from any sensor unit falls either below a minimum or above a maximum threshold value for that sensor unit (step 1314), an alert message is transmitted to the parent unit 602 (step 1316). Once this is done, or alternatively if all sensor outputs are within threshold values, the process is complete.

Although the method illustrated in Figure 13 involves comparing sensor outputs to threshold values, in alternative embodiments of the present invention other methods of analyzing sensor outputs may be substituted. For example, the child unit 102 may analyze outputs from a plurality of sensors in cooperation with one another, in order to build a more complete picture of the child's situation. This may, as an example, comprise linking a high observed heart rate with a high observed body temperature and high acceleration measured by an accelerometer, in order to determine that the high heart rate is due to the child running and most likely not indicative of an injury. In the case of a high observed heart rate with a normal observed body temperature and low acceleration measured by an accelerometer, it may be determined that the child is stressed and requires the attention of a parent. The person skilled in the art may substitute other similar methods as appropriate. In the present example, the alert message transmitted at step 1316 contains information on the sensor units for which an output has exceeded a threshold level, and also contains information identifying the wireless wearable tag unit 102 which transmitted the alert message. However, other formats may readily be substituted for the alert message as required; for example, the alert message may simply cause the alarm unit 712 of the parent unit 602 to be automatically activated. In an alternative embodiment, the child unit 102 may be configured to wait for a predetermined time before comparing the danger levels to threshold danger levels (step 1306). After waiting for the predetermined time, the child unit 102 again measures the distance to each of the tag units in the list generated in step 1302. If the new measured distance is greater than the operating range for the tag unit, it is determined that the child is no longer in range of the dangerous object, and the tag unit is removed from the list; hence, that tag unit will not cause an alert message to be sent to the parent unit 602. This embodiment may prevent an alert message being unnecessarily transmitted to the parent unit 602 in the event that the child has already moved away from the dangerous object, following the alarm at the child unit 102. This step of waiting for a predetermined time may be performed according to a danger level of each tag unit; for tag units having a high danger level, it may be desired to always transmit an alert message, regardless of whether the child has moved away from the dangerous object.

Figure 14 schematically illustrates a structure of a child unit 1402 according to an alternative embodiment of the present invention. In this embodiment, the child unit 1402 further comprises an audio/video unit 1404. In the present example, the audio/video unit 1404 comprises a video camera, microphone and speaker; the video camera and microphone allowing audio and video signals to be captured and transmitted to a parent unit 602.

In this example, the user interface 710 of the parent unit 602 further comprises a display screen allowing a video signal received from the child unit 1402 to be displayed, and a speaker allowing an audio signal received from the child unit 1402 to be reproduced. The user interface 710 also further comprises a microphone, allowing audio to be transmitted from the parent unit 602 to the child unit 1402, where the received audio is reproduced by the speaker of the audio/video unit 1404. This embodiment of the present invention allows a user of the parent unit to view live audio and video signals from the child unit 1402, and hence directly observe the current environment and status of a child wearing the child unit 1402. Furthermore, since audio may be transmitted from the parent unit 602 to the child unit 1402, a user of the parent unit is able to speak to the child to provide reassurance if required, before the user of the parent unit 602 physically arrives at the child's location.

In the present example, a user of the parent unit 602 may control the parent unit 602 to transmit a request to the child unit 1402, requesting audio and video signals to be transmitted. Furthermore, the child unit 1402 is configured only to transmit video and audio signals in response to such a request from the parent unit 602, thus helping to conserve power by eliminating unnecessary transmissions from the child unit 1402 to the parent unit 602.

However, the person skilled in the art will readily substitute alternative methods of selecting when to transmit video and audio signals, as appropriate to particular equipment or user requirements. As examples, video and audio may be transmitted periodically, or automatically transmitted along with an alert message. Similarly, various alternative embodiments of the audio/video unit 1404 and the user interface 710 are possible, as will be readily apparent to a person skilled in the art. As examples, only audio equipment (i.e. speakers and microphones) may be provided in order to reduce bandwidth and processing requirements, or alternatively both the child unit 102 and the parent unit 602 may be provided with video cameras and display screens in addition to microphones and speakers, allowing audio and video signals to be transmitted in both directions.

In summary, a system for monitoring a child in a home environment is disclosed. The system comprises at least one tag unit and a child unit. The tag units are configured to be secured to objects within the home environment, and are further provided with an operating range, the operating range being used to define a region around the tagged object within which there is a risk of injury to the child. The child unit comprises a distance measurement unit configured to periodically measure the distance between the child and tag unit secured to an object, a logic unit configured to check whether the child is within the operating range based on the measured distance, and an alarm unit configured to activate an alert mechanism if the child is within the operating range. The disclosed system performs an early detection of a dangerous environment and can prevent injury to the child. In the event that a child has suffered an injury, the disclosed system can immediately notify a user of a parent unit of the injury to the child, allowing them to respond rapidly. Although various embodiments of the present invention have been described herein with reference to the Figures, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the invention as defined by the accompanying claims. For example, although certain methods have been described in relation to the illustrated apparatus embodiments, a person skilled in the art will readily adapt the disclosed methods as suitable for their chosen apparatus.

As examples, various alternative embodiments may comprise providing a conventional charging unit instead of the induction charging unit of the present example, with conventional rechargeable batteries being provided; providing different levels of tag units with different default operating ranges or different preset danger levels; and providing tag units to be attached to door frames or doors in order to prevent a child accessing a specific room. Furthermore, if a different method of distance measurement is used, not requiring ultrasonic transducers in the tag units, passive RFID tags (i.e. tags without an internal power supply) may be used. If passive RFID tags are used and an operating range setting unit is not provided, a passive tag unit may be provided with operating range setting means which do not require a power supply, for example a dial or switch, which may be operated by a user to set an operating range for the tag unit while the tag unit is not powered on.

In another alternative embodiment, the parent unit 602 may be provided with an US transducer and antenna similar to a tag unit; the child unit 102 may then periodically attempt to measure a distance to the parent unit 602. If it is possible to measure a distance to the parent unit 602, it is determined that the parent unit 602 and child unit 102 are in the same room; accordingly, or if the parent unit is within a certain maximum range, the child unit 102 may be further configured to not activate any alarms, nor to transmit any alert messages to the parent unit. This embodiment allows alerts to be suppressed when the parent unit is nearby, i.e. when the parent is close enough to supervise the child themselves. This feature may be 'always-on', or may be activated by the parent using means provided on either the parent unit 602 or child unit 102.

An alternative embodiment of the distance measurement method may comprise the child unit 102 transmitting the distance measurement request to a tag unit as an US signal rather than an RF signal, and the tag unit only transmitting an US signal and no RF signal in response. In this embodiment, the tag unit ID number is encoded into the US signal transmitted by the child unit 102. The tag unit receives the request, and transmits a response after a known delay. The travel time is then calculated by the child unit 102 on the basis of a measured time between transmitting and receiving the respective US signals at the child unit 102, and the known delay. From this travel time, the distance can be calculated; it is assumed that the process occurs sufficiently quickly that the tag unit and child unit 102 can be considered stationary with respect to one another, so each US signal travels the same distance. This embodiment may have the advantage that it is not necessary to include an RF antenna at the tag unit, although one may still be provided for other communications, e.g. setting an operating range.

Use of the verb "comprise" and its conjugates does not exclude the presence of elements other than those stated in a claim or in the description. Use of the indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps. The Figures and description are to be regarded as illustrative only and do not limit the subject matter. Any reference sign in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A wireless sensor unit (102) comprising: distance measurement means (402) configured to measure a distance from the wireless sensor unit to a tag unit (104); a logic unit (404) configured to compare the measured distance to the tag unit with an operating range for the tag unit; and an alarm unit (410) configured to alert a user (202) of the wireless sensor unit in the event that the measured distance is less than or equal to the operating range.

2. A wireless sensor unit according to claim 1, configured to receive operating range data from the tag unit.

3. A wireless sensor unit according to claim 1 or 2, further comprising a communications unit (806), wherein the logic unit is configured to control the communications unit to transmit an alert message to a monitoring unit (602) in the event that the measured distance is less than or equal to the operating range.

4. A wireless sensor unit according to claim 3, further comprising a plurality of sensors (802, 804) configured to measure at least one of environmental and physiological parameters, the logic unit being configured to compare an output from each sensor to at least one threshold value for said sensor, and further configured to control the transmitter to transmit an alert message to the monitoring unit in dependence on the result of said comparison.

5. A wireless sensor unit according to claim 3 or 4, further comprising an audio/video unit (1404), the wireless sensor unit being configured to transmit at least one of audio and video signals to the monitoring unit.

6. A wireless sensor unit according to any one of the preceding claims, wherein the wireless sensor unit is configured to be worn by the user.

7. A wireless sensor unit according to any one of the preceding claims, further comprising a power supply (406) and an induction coil (408), the induction coil being operable in conjunction with an induction coil (506) of a charging unit (502) to charge the power supply.

8. A wireless sensor unit according to any one of the preceding claims, wherein the distance measurement means further comprises an ultrasonic transducer (414) and a radio-frequency communication unit (418).

9. A monitoring unit (602) comprising: a communications unit (702) configured to receive an alert message from a wireless sensor unit (102); an alarm unit (712); and a logic unit (704) configured to control the alarm unit to alert a user of the monitoring unit in response to the received alert message.

10. A monitoring unit according to claim 9, further comprising a user interface unit (710) configured to reproduce at least one of an audio signal and a video signal received from the wireless sensor unit.

11. A monitoring unit according to claim 9 or 10, further comprising a power supply (706) and an induction coil (708), the induction coil being operable in conjunction with an induction coil (506) of a charging unit (502) to charge the power supply.

12. An operating range setting unit (902) comprising: operating range user input means (916) configured to receive an operating range selected by a user; a communications unit (912); and a logic unit configured to control the communications unit to transmit said received operating range to a tag unit.

13. An operating range setting unit according to claim 12, further comprising a power supply (906) and an induction coil (908), the induction coil being operable in conjunction with an induction coil (506) of a charging unit (502) to charge the power supply.

14. A monitoring system comprising: a plurality of tag units (104, 106, 108, 110, 112) each having a preset operating range; and at least one wireless sensor unit (104) according to any one of claims 1 to 8.

15. A monitoring system according to claim 14, further comprising at least one of a monitoring unit (602) according to claim 9, 10 or 11 and an operating range setting unit (902) according to claim 12 or 13.

16. A monitoring system according to claim 15, wherein the operating range setting unit and the monitoring unit are provided in the same physical device.

17. A monitoring system according to any one of claims 14 to 16, wherein the tag units are active radio-frequency tags.

18. A monitoring system according to claim 17, wherein each one of the tag units further comprises an ultrasonic transducer (308) arranged to transmit an ultrasonic signal to the at least one wireless sensor unit.

19. A monitoring system according to any one of claims 14 to 18, wherein each one of the plurality of tag units includes operating range setting means for inputting an operating range of the tag unit.

20. A method of determining whether to alert a user (202) of a wireless sensor unit

(102), the method comprising: measuring a distance from the wireless sensor unit to a tag unit (104), comparing the measured distance to the tag unit with an operating range for the tag unit, and alerting the user of the wireless sensor unit in the event that said measured distance is less than or equal to said operating range.

21. A method according to claim 20, further comprising transmitting an alert message to a monitoring unit (602) in the event that the measured distance is less than or equal to the operating range.

22. A method according to claim 20 or 21, wherein the operating range for the tag unit is an operating range selected by a user.

23. A method according to claim 20, 21 or 22, wherein alerting a user of the wireless sensor unit comprises controlling an alarm unit (410) to generate at least one of an audible warning sound or a physical vibration.

24. A method according to any one of claims 20 to 23, wherein measuring the distance from the wireless sensor unit to the tag unit comprises: controlling the tag unit to transmit a radio -frequency signal and an ultrasonic signal in synchronization with each other to the wireless sensor unit, measuring a time difference between arrival of the radio-frequency signal and arrival of the ultrasonic signal at the wireless sensor unit, and calculating the distance travelled by the ultrasonic signal on the basis of the measured time difference.

25. A wireless wearable child unit comprising: a distance measurement unit configured to periodically measure the distance between the child and a wireless proximity tag to an object; a logic unit configured to check whether the child is within the desired operating range based on the measured distance; and an alarm unit configured to activate an alert message if the child is within the set desired operating range.

26. A wireless parent unit comprising: receiving means to receive an alert message from a wireless wearable child unit.