IE20120372U1 - Fall detector - Google Patents

Abstract

ABSTRACT A fall detector comprising: a power source; an accelerometer; a signal generator; a processor; the power source being arranged to power the accelerometer and being further arranged to selectively power the processor; wherein the signal generator is arranged to generate a control signal to power the processor in response to receiving trigger data from the accelerometer indicative that movement of the fall detector has terminated.

Description

FALL DETECTOR AS FIELD OF THE INVENTION The present invention relates to a fall detector. More particularlyfbut not exclusively it relates to a fall detector comprising a microelectromechanical (M EMS) accelerometer.

BACKGROUND TO THE INVENTION open to PUBLIC irisrscrinri urrnta szerseri 23 A?'».'9J RULE 23 Jrri or»?/3.

Falls can often cause injuries to a person. This can be particularly important where the person is elderly or vulnerable. In the case of an elderly person or vulnerable person the injuries sustained by them in the fall can be serious and can prevent them from requesting assistance in a timely manner. Delays in requesting assistance can lead to exacerbation of the injuries caused by the fall and even in extreme cases death of the person who has sustained the fall.

Fall detectors for automatically monitoring falls are known. Typically, these devices use vibration sensors to detect the fall of a person, with some more advanced fall detectors using at least one accelerometer to detect the fall of a person. MEMS accelerometers are configured to sense acceleration on one, two or three axes and provide analog or digital outputs in response. These current fall detectors require that a microprocessor, or other central processing unit (CPU), is active for most of the time, and therefore consuming power. This leads to a short lifetime for a power source associated with the fall detector. In these fall detectors the microprocessor is activated in response to the receipt of an initial trigger, most commonly the onset of a fall.

The graph shown in Figure 4b shows a normalised characteristic of a typical fall with time on the horizontal axis and acceleration shown on the vertical axis. Acceleration is measured on three vertical axis, indicative of a 3 axis accelerometer. As shown herein the controller is activated 410 at partial free fall 404. Partial frfalcu . for example, during a stair descent. Accordingly descending a stairs can "wake" the microcontroller and consume battery power thus reducing the life of the battery and requiring replacement of the battery or power source. False alarms may also be triggered where a person may stumble but not actually fall. Powering up the microcontroller to poll the accelerometer to determine if a trigger event or a combination of trigger events has happened leads to the additional problem of a short power source lifetime. it is therefore desirable to provide a truly low power device where the period of activity of the microcontroller is minimised and thus the power requirement is reduced.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a fall detector comprising: a power source; an accelerometer; a signal generator; a processor; and the power source being arranged to power the accelerometer and being further arranged to selectively power the processor; wherein the signal generator is arranged to generate a control signal to power the processor in response to receiving trigger data from the accelerometer indicative that movement of the fall detector has terminated.

The accelerometer may comprise a MEMS accelerometer.

This provides a low power, compact accelerometer that draws oniy a small amount of power from the power source, thereby providing a long power source lifetime.

The fall detector may comprise a transmitter. The processor may be arranged to selectively allow the power source to power the transmitter in response to the 3 control signal. The processor may be arranged to activate the transmitter upon receipt of the control signal. The processor may be arranged to generate an alarm signal and to pass the alarm signal to the transmitter upon receipt of the control signal. The transmitter may be arranged to transmit the alarm signal to a remote device. The selective powering of the transmitter reduces drain of the power source, thereby increasing the longevity ofthe power source.

The accelerometer may comprise a buffer memory. The buffer memory may be arranged to store data indicative of the output of the accelerometer prior to the generation of the control signal. The processor may be arranged to read the contents of the buffer memory in response to the control signal. The buffer memory may comprise a circular buffer. This allows the data showing what happened prior to the trigger event to be captured an analysed to provide an accurate analysis of the trigger event.

The trigger data may comprise at least one of the following: free fall, single tap, or double tap. Trigger data indicative that movement of the fall detector has terminated is a double tap.

The fall detector may comprise means for manually triggering an alert. The means for manually triggering an alert may comprise a panic button. This would allow the wearer of the panic button to manually trigger alert in the absence of a fall.

The power source may comprise a battery.

A further embodiment of the present invention includes A method of detecting fall comprising: receiving trigger data from an accelerometer and generating a control signal to power a processor in response to receiving trigger data from the accelerometer indicative that fall has terminated.

If it is determined that the fall has terminated, only at this point is the microcontroller awoken and thus power consumption is minimised.

IE‘l2il572 4 Data may be stored data in response to receiving trigger data from an accelerometer.

Generating of the control signal may further comprise retrieving stored data.

Generating a control signal may further comprise analysing stored data.

In a further step, the method may further comprise selectively powering a transmitter in response to the generated control signal. The transmitter may be activated upon receipt of the control signal.

An alarm may be generated signal and passed to the transmitter upon receipt of the control signal.

The alarm signal may be transmitted to a remote device.

Trigger data may comprise at least one of the following: free fall, single tap, or double tap. Trigger data indicative that movement of the fall detector has terminated comprises the double tap. Additionally alerts may be manually triggered.

A panic button may be used to manually trigger an alert BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a schematic diagram an embodiment of a fall detector according to an aspect of the present invention; Figure 2 is a schematic diagram of the fall detector of Figure 1 in communication with a remote mobile telephone in accordance with an aspect of the present invention; Figure 3 is a flow chart showing a method of operation of the fall detector of Figure IE 1 2 0 3 7 2 Figure 4a is a graph of data collected from an accelerometer of a fall detector of the present invention before, during and after a fall; and Figure 4b is a graph of data collected from a prior art fall detector before, during and after a fall.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Figure 1, a fall detector 100 comprises a battery 102, a control processor 104, a user interface 106, a transmitter 108 and a MEIVIS accelerometer 110. Typically, but not exclusively, the transmitter 108 comprises a Bluetoothw transmitter.

The transmitter 108 may be arranged to communicate with an external communication device 112 such as a mobile telephone, a tablet computer, a pager or a remote alarm system Alternatively, the communication device 112 may be integral to the falls detector however it will be appreciated that this would increase the power requirements of the device. When a transmission is received from the transmitter 108 at the external communication device 112 an alert message such as, but not exclusively, a text message, email or instant message may be transmitted or sent to a device administrator remote from the user or wearer of the fall detector.

The fall detector may also include a panic button 114 which when activated can trigger a transmission from the transmitter 108 to the communication device 112 to send an alert message. The transmission can include a predefined alert or can include an alert selectable from a plurality of options. Typically but not exclusively, the optional messages can be accessed by activations of the panic button 114 to scroll through a list of options.

The administrator or carer may be provided with a mobile telephone 200 or other mobile communication device. The falls detector 100 transmits a notification of a fall or other triggering event to the mobile communication device associated with the |E‘l20372 6 fall detector 204. This transmission may be, but is not exclusively restricted to a Bluetooth communication. It will be appreciated that Zigbee, Induction Wireless or Infrared Wireless communications are also suitable communication mechanisms. In a low power configuration of the fall detector, a telephone number may be obtained from the owner's mobile communication device 202 therefore eliminating the need for additional storage on the fall detector.

The user interface of the mobile communication device 202 can be used to enter a contact number and this contact number can be retrieved when an alarm is to be raised. In one configuration, the user interface is reduced to a button, a buzzer and three light emitting devices, LEDs indicating the battery state, the alarm mode and the Bluetooth pairing state. This reduced user interface provides a simple device for use by an elderly or possible impaired person.

When a fall is triggered the fall transmitter 108 sends a request 1 via the relevant communication mechanism, for example Bluetooth to the mobile device 202. A telephone number or other contact details can be transmitted 2 to the fali detector for display on the user interface 106. In response the falls detector issues an instruction 3 to the mobile communication device to send a message 4 to the carers mobile phone 200.

The falls detector provides an instruction to the mobile device 202 to transmit a message to the administrator or carers mobile communication device 200 at which point appropriate action may be taken. This transmission may be sent via any suitable communication protocol. The mobile device 202 may also be configured to send a confirmation message to the falls detector 100. it will be appreciated that steps 2 and 3 of Figure 2 are optional steps. Following 1 when an alert is sent to the mobile communication device 202 a message may be sent directly to the administrator or carers communication device 200. 15129372, In an alternative embodiment, the user interface 106 comprises a screen which, when activated, displays, for example, the status of the fall detector 100, the status of the transmitter 108 and any connection associated with the transmitter~108, the battery level, the optional messages selectable by activation of the panic button, or the time.

The screen of the user device may also be configured to display a confirmation message from the mobile device 202 that an alert message had been sent or alternatively contact information returned from the mobile communication device 202.

In a preferred but not exclusive configuration one or more lights, for example LED lights can used to provide indications of status of transmitter and any connection associated therewith, status of the fall detector, batter level, activation of the panic button or receipt of a confirmation that an alert message had been sent. The user interface may be reduced to a button, a ‘buzzer and three light emitting devices, LEDs indicating the battery state, the alarm mode and the Bluetooth pairing state. This reduced user interface provides a simple device for use by an elderly or possible impaired person.

The user interface may also include one or more access ports for providing updates, for example software updates for the device or alternatively for connecting the fall detector to an external computing device or reader.

Figure 3 outlines a method of operating the falls detector in accordance with the present invention. During initialisation 302 subsequent starting the device 302 the MEMS accelerometer 110 is configured. Configuration includes the setting or parameters including, but not exclusively limited to range, free fall acceleration range, free fall time, single tap amplitude and duration and double tap amplitude and duration. It will be appreciated that during this initialisation phase remaining device parameters including but not limited to Bluetooth parameters, circular buffer parameters and serial communication queues are configured. Following initialisation IE ‘£20572 8 of the falls detector 100, the MEMS accelerometer 110 is configured to continuously monitor the acceleration of the subject or wearer in order to raise an alarm when a fall occurs. The MEMS accelerometer 110 senses acceleration and stores the measured accelerations in a buffer. in a preferred embodiment the buffer is a circular buffer. The use of the buffer enables retrieval of the data several. seconds after the event.

The CPU is maintained in a sleep state 304 thereby minimising power requirements.

As outlined in Figure 3, on receipt of a trigger a decision is made 306 by the accelerometer as to whether to store the data in the buffer or to act on the trigger.

Triggers may include free fall, single tap, double tap, activity, or inactivity.

In determining whether to store the data or act on the trigger the trigger type is assessed. If free fall is detected, for example, rather than waking the CPU the decision is made to store the data 308. The accelerometer 110 continues to monitor for the next event. If for example the next event is a doubie tap, this signifies that the floor or ground has been impacted and a fall has occurred.

At this point an instruction is issued to wake up the CPU 310 and retrieve data 312 from the circular buffer. Additional data is then accessed by the CPU 314. This additional data serves to validate the orientation of the accelerometer. An analysis is made of the retrieved data. For example if the previous event to the double tap is a settling period then it can be confirmed that a fall has been detected and an alert message can be triggered as outlined above. If the previous event to the double tap is a period of inactivity then it can be determined that a fall has not occurred and an alarm with not be triggered.

The data shown in Figure 4a and b is simplified and filtered to remove normal motion artefacts. The fall detector in this instance is assumed to be aligned to the vertical gravitational field. This is for explanatory purposes, but it will be appreciated that the device can be randomly orientated with many small acceleration variations.

IE ‘lZ0372_ The graph shown includes time on the horizontal axis 401 and acceleration on the vertical axis 402. Following a fall the acceleration data on the axes is rotated relative to its position prior to the fall 408. This corresponds to the body position of the wearer of the falls detector changing from vertical to horizontal.

Prior to a fall the gravitational acceleration is parallel with a first one of the axis (Axisli. The remaining two axis, indicated as Axis2 and Axis 3 are also horizontal as indicated in area 403 of Figure 4A. As shown in Figure 4b the measurement on Axisl is -1g and the acceleration on Axis 2 and 3 is Og. At the start of a fall 404 there is a level of weightlessness. This is due to ’’partial free fall’’. As partial free fall occurs, all three axes are detecting a gravitational acceleration close to Og. This becomes more pronounced during "free fall" 404 where the vector sum of acceleration tends towards 0g. When the body makes initial contact or hits the ground there is a substantial "tap”. The acceleration curve shows this as a large shock 405. Following this shock there is a settling period where the human body after impact cannot rise immediately and slumps to the ground 406. At the end of the fall there is a final "double tap” 407.

Figure 4b is directed to the prior art wherein microprocessors are awoken from sleep at or close to the start of a fall. As a ‘consequence, the microcontroller is awake during the full fall and is therefore consuming power for a longer time.

In contrast, Figure 4a shows the activation of the microcontroller on detection of a "double tap”. Detection of the double tap, the accelerometer signals the microcontroller of CPU that a fall has occurred. The microcontroller awakes from sleep and then retrieves the data from the buffer and determines whether the double tap was the follow up of a fall or due to another disturbance. The microcontroller also compares the direction of the device relative to the gravitational acceleration before (403) and after (408) the candidate fall deciding if the wake up signal was due to a fall orjust a false alarm. If a fall is detected an alert message can be transmitted. lE12037g.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims (5)

Claims

1. A fall detector comprising: a power source; an accelerometer; a signal generator; a processor; the power source being arranged to power the accelerometer and being further arranged to selectively power the processor; wherein the signal generator is arranged to generate a control signal to power the processor in response to receiving trigger data from the accelerometer indicative that movement of the fall detector has terminated.

2. The fall detector according to c|a_im 1 wherein the accelerometer comprises a microelectromechanical MEMS accelerometer.

3. The fall detector according to any previous claim wherein the fall detector further comprises a transmitter. 4. The fall detector according to any previous claim wherein the processor is arranged to selectively allow the power source to power the transmitter in response to the control signal 5. The fall detector according to claim 4 wherein the processor is arranged to activate the transmitter upon receipt of the control signal. 6. The fall detector according to claim 5 wherein the processor is arranged to generate an alarm signal and to pass the alarm signal to the transmitter upon receipt ofthe control signal. 7. The fall detector according to claim 6 wherein the processor is arranged to transmit the alarm signal to a remote device. 8. The fall detector according to any previous claim wherein the accelerometer comprises a buffer memory. 9. The fall detector according to claim 8 wherein the buffer memory is arranged to store data indicative of the output of the accelerometer prior to the generation of the control signal. The fall detector according to claim 8 or 9 wherein the processor is arranged to read the contents of the buffer memory in response to the control signal. The fall detector according to any of claims 8 to 10 wherein the buffer memory comprises a circular buffer. The fall detector according to any previous claim wherein the trigger data comprises at least one of the following: free fall, single tap, or double tap. The fall detector according to any claim 12 wherein trigger data indicative that movement of the fall detector has terminated comprises a double tap. The fall detector according to any previous claim further comprising means for manually generating an alarm signal The fall detector according to claim 14 wherein the means for manually generating an alarm signal comprises a panic button. The fall detector according to any previous claim wherein the power source comprises a battery. A method of detecting fall comprising: receiving trigger data from an accelerometer; and generating a control signal to power a processor in response to receiving trigger data from the accelerometer indicative that fall has terminated. The method of claim 17 further comprising storing data in response to receiving trigger data from an accelerometer. The method of claim 18 wherein generating a control signal further comprises retrieving stored data. The method of claim 19 wherein generating a control signal further comprises analysing stored data. The method of any of claims 17 to 20 further comprising selectively powering a transmitter in response to the generated control signal. The ' method according to claim 18 further comprising activating the transmitter upon receipt of the control signal. The method according to claim 22 further comprising generating an alarm signal and passing the alarm signal to the transmitter upon receipt of the control signal. The method according to claim 23 further comprising transmitting the alarm signal to a remote device. The method according to any previous claim wherein the trigger data comprises at least one of the following: free fall, single tap, or double tap. The method according to Claim 25 wherein trigger data indicative that movement of the fall detector has terminated comprises a double tap. The method according to any previous claim further comprising manually generating an alarm signal. A fall detector as described herein with reference to the appended drawings A method of detecting a fall as described herein with reference to Figure 3. A computer readable storage medium carrying a computer program stored thereon, said program comprising computer executable instructions adapted to perform the method steps of any of Claims 17 to 27 when executed by a processing module." SQEC3 085sQec3090sQec3091 TOMKINS 8: C0. The following revised Claims were filed on 16"‘ August 2013 IE i20372T Claims

4.

5. regzl 0005 A fall detector comprising: a power source; an accelerometer; a signal generator; a processor; the power source being arranged to power the accelerometer and being further arranged to selectively power the processor; wherein the signal generator is arranged to generate a co_ntro| signal to power the processor in response to receiving trigger data from the accelerometer indicative that movement of the fall detector has terminated. The fall detector according to claim 1 wherein the accelerometer comprises a microelectromechanical MEMS accelerometer. A method of detecting fall comprising: receiving trigger data from an accelerometer; and generating a control signal to power a processor in response to receiving trigger data from the accelerometer indicative that fall has terminated. A fall detector as described herein with reference to the appended drawings A method of detecting a fall as described herein with reference to