DE102020115759A1 - Contactless detection of at least one vital parameter - Google Patents

Abstract

Method for the contactless determination of at least one vital parameter of a living being (3), the living being (3) being located in or on a storage device (1) and at least three sensors (2) being arranged in or below the storage device (1), which Plane (E), the sensors (2) detecting a change in a weight over time and/or a change over time in a center of gravity of the living being (3) within the plane (E), the sensor signals (m1, m2, m3, m4) the at least three sensors (2) are forwarded to a controller and are recorded over a defined period of time, with the recorded sensor signals (m1, m2, m3, m4) being pre-processed by the controller and the sensor signals (m1, m2, m3, m4) are converted into a two-dimensional intermediate signal (4), a one-dimensional signal (5) then being generated from the two-dimensional intermediate signal (4) and from the one-dimensional signal (5) at least one vital parameter of the living being is determined.

Description

FIELD OF THE INVENTION

The present invention relates to a method for the contactless determination of at least one vital parameter of a living being, the living being being in or on a storage device.

TECHNICAL BACKGROUND

Various approaches are already known from the prior art in order to determine contactless vital function characteristics from a contactlessly recorded measurement signal, in particular when the living being, in particular the human being, is stored on a corresponding storage device or is located on such a device.

On the one hand, systems and methods are already known in which signal curves from sensors, preferably force deformation sensors or strain gauges, which are arranged at different positions of the mounting device and at least indirectly detect the movements of a person on the mounting device, are transformed into a frequency space by means of a Fourier transformation and the vital function characteristics, in particular the characteristic frequencies and harmonics of a heartbeat, are detected or identified on the basis of an evaluation of the signal in the frequency domain. The disadvantage of using the Fourier transformation when evaluating the signal curves of the sensors is that the Fourier transformation becomes more effective and more accurate the longer the recorded signal or the longer the signal curve (over the period). As a result, the vital function characteristics can only be determined with a relatively low repetition rate or frequency. In addition, the Fourier transformation is computationally expensive, so that the requirements to be placed on the system, in particular on the computing power, in order to carry out such methods are great. One approach to determining vital function characteristics using Fourier transforms is, for example, the publication EP 2 040 614 B1 refer to.

Another approach that avoids the transformation of signal curves into a frequency domain is, for example WO 2017/056 476 A1 which provides for the contactless determination of vital function characteristics based on a measurement signal or from a measurement signal that, based on signal curves from sensors, preferably force deformation sensors or strain gauges, the forces are determined which a person on a support device, in particular on a hospital or nursing bed, exercises, with the determination of a body mass vector based on the signal profiles, and with the aid of the temporal change in the body mass vector a recognition of vital function characteristics, for example a determination of a heartbeat, takes place. This approach is also relatively complex and computationally intensive.

Devices that can be used in corresponding methods from the prior art are, for example, from EP 1 937 148 B1 or the DE 20 2008 018 439 U1 known.

DESCRIPTION

It is therefore the object of the invention to propose a method for the contactless determination of at least one vital parameter, in particular a heartbeat, of a person in or on a positioning device, in particular a hospital or nursing bed using a contactlessly measured or generated measurement signal, which method is based on the prior art Technology overcomes predominant problems and in particular enables a simple, effective and resource-saving determination of the vital parameter.

This object is achieved in a method of the type mentioned at the outset in that at least three sensors are arranged in or under the storage device, which span a plane, the sensors changing a weight force over time and / or changing a center of gravity of the living being over time Detecting the plane, the sensor signals of the at least three sensors being passed on to a controller and recorded over a defined period of time, the recorded sensor signals being preprocessed by the controller and the sensor signals being converted into a two-dimensional intermediate signal, a one-dimensional signal then being derived from the two-dimensional signal Intermediate signal is generated and at least one vital parameter of the living being is determined from the one-dimensional signal.

berechnet.The one-dimensional signal is obtained from the two-dimensional intermediate signal by the formula $$\mathrm{\kappa }\left(\text{t}\right)=\text{b '}\left(\text{t}\right)\ast \text{a ''}\left(\text{t}\right)-\text{a '}\left(\text{t}\right)\ast \text{b ''}\left(\text{t}\right)$$

calculated.

The two-dimensional intermediate signal corresponds to the change in weight and / or the change in the center of gravity of the living being.

Alternatively, the one-dimensional signal can be generated from the curvature of the two-dimensional intermediate signal.

The method according to the invention enables a signal improvement or signal amplification to be achieved in the individual signals of the sensors without complex Fourier transformation or determination of a body mass vector, which overall makes it possible to measure at least one vital parameter, in particular the heartbeat, with high reliability and high accuracy. to determine or to make determinable.

It is thereby achieved in a particularly advantageous manner that a contactless determination of the vital parameter, for example the heartbeat frequency, can be determined simply, effectively and reliably within a short time and accordingly with a high possible repetition rate. In this way, in particular, the person stored in or on the positioning device can be observed or monitored without the need for any particular effort and, moreover, also without the immediate proximity of a person being monitored to the person being monitored or the person being monitored in or on the storage device must be made.

According to a further embodiment of the method, a recurring signal sequence is present in the one-dimensional signal which corresponds to the vital parameter, the controller performing a pattern recognition in order to identify the recurring signal sequence. The recurring signal sequence can correspond to the vital parameter per unit of time, in particular one heartbeat per minute. For example, the controller can carry out an autocorrelation for this purpose.

According to a further embodiment of the method, the sensors span the plane, the living being being arranged above the plane. The two-dimensional intermediate signal detects or represents the temporal change in weight and / or the temporal change in the living being's center of gravity along a longitudinal axis and along a transverse axis of the plane. The two-dimensional intermediate signal preferably corresponds to the movement of the living being's center of gravity on the plane. As a result, the slightest changes in the living being's center of gravity can be detected. In particular, the veins of the living being's center of gravity, which are detected by preferably four sensors, which are arranged in or below the level of the storage device, are the contraction of the myocardium or the ejected blood volume that is ejected when a heartbeat occurs. Due to the ejected blood volume, the center of gravity of the living being on the storage device, which is detected by the sensors, changes. The center of gravity of the living being changes not only in one direction of the plane, but also along a longitudinal axis and along a transverse axis of the plane.

The controller preferably determines the center of gravity of the living being using the formula $$\frac{\text{m1}\left(\text{t}\right)=\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m2}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ -\text{x0}\end{array}\right)+\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ -\text{x0}\end{array}\right)+\text{m4}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ \text{x0}\end{array}\right)}{\mathrm{4th}}\text{.}$$

bestimmt.The temporal change in the center of gravity of the living being is given along the longitudinal axis of the plane by the formula $$\text{a}\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m2}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ -\text{x0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ -\text{x0}\end{array}\right)-\text{m4}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ \text{x0}\end{array}\right)$$

definitely.

bestimmt, wobei sowohl die Veränderung des Schwerpunkts des Lebewesens entlang der Längsachse der Ebene als auch die Veränderung des Schwerpunkts des Lebewesens entlang der Querachse der Ebene über die Zeit detektiert wird.The temporal change in the center of gravity of the living being along the transverse axis of the plane is given by the formula $$b\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m4}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ \text{x0}\end{array}\right)-\text{m2}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ -\text{x0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{y0}\\ -\text{x0}\end{array}\right)$$

determined, wherein both the change in the center of gravity of the living being along the longitudinal axis of the plane and the change in the center of gravity of the living being along the transverse axis of the plane are detected over time.

According to a further embodiment of the method, the controller determines a center of gravity and / or a total weight of the living being on the storage device. The total weight and / or the center of gravity of the living being is determined before the actual measurement of the vital parameter takes place. Furthermore, the determination of the vital parameter can be ended when the change in the center of gravity and / or in the total weight of the living being is greater than a defined limit value. In particular, if the center of gravity and / or the total weight of the living being changes by at least 2%, the control can interrupt a determination of the vital parameter. On the basis of the limit value, both movements of the living being can be detected and presence detection can be carried out in order to detect occupancy of the storage device. For example, the The storage device can be a bed and a vital parameter, preferably a heart rate, is to be determined from the living being, in particular a person, who is lying in the bed. As soon as a second person sits down on the bed, reliable detection of the heartbeat frequency can no longer be guaranteed because two heartbeats are detected and these can lead to a wrong result.

According to a further embodiment of the method, the sensor signals of the at least three sensors are recorded in a time-synchronous manner. As a result, the change in weight and / or the center of gravity can be precisely detected.

According to a further embodiment of the method, it can also be provided that the preprocessing of the signal curves of the individual sensors includes the removal of a DC voltage offset and / or the use of a high-pass filter and / or the use of a low-pass filter.

The aforementioned preprocessing steps of the respective individual signal curves can form an even better starting basis for creating the two-dimensional intermediate signal. For example, it can be provided that each individual signal of the, preferably four, sensors is freed from a DC voltage offset which reproduces or represents the weight of the mounting device and of the body as such without the movement of the body. Four sensors are preferably arranged in or under the storage device.

It should be noted at this point that the DC voltage offset can be used to detect the presence and / or determine the weight or mass of the person on or in the storage device, in which case the known properties of the storage device itself and their precipitation in the signals the sensors is taken into account, so for example the weight of the storage device can be calculated. The presence detection can serve, for example, as an initiator or as a termination criterion for carrying out the method according to the invention. The determination of mass or weight can be further used or used in the context of the monitoring or observation of people in or on the storage device.

Subsequent to this, the individual signals can be pre-filtered, whereby it can preferably also be provided that a signal from an individual sensor is processed or filtered with different filters, the filtering not being able to take place one after the other but rather independently of one another. It can therefore be particularly preferably provided that the preprocessing of the signals provides for different filter processes for each individual signal from the sensors. For example, it can be provided that after a DC offset has been removed, the signal of at least one sensor or the signal curve of a sensor is fed to a high-pass filter and, independently thereof, to a low-pass filter, or filtered with the corresponding filters, and then merged as part of a difference between the two filtered signal curves of the filtered signal curves takes place.

As an alternative to this, however, it can be provided that the filtering of the signal curves for the signal curve of a sensor or channel is carried out successively one after the other or one after the other. For example, it can be provided that a low-pass filter is first applied to the signal profile and then a high-pass filter is applied to the signal profile.

Furthermore, a method step can be provided in which an automatic classification of the automatically determined vital parameters, in particular the heartbeat frequency, takes place in a standardized interval classification, preferably in the international classification of the American Heart Association (AHA). This enables the heartbeat frequency to be classified into corresponding intervals, which in turn can be evaluated particularly well and particularly intuitively in the context of observation or monitoring with regard to any need for action or reaction requirements that may be present, in particular if the heartbeat frequency is classified in a correspondingly high or low interval class.

According to a further, particularly advantageous embodiment of the method, it can be provided that an adaptive sensitivity of a recognition algorithm is used in the context of the peak value or maximum value determination. In other words, this means that within the scope of the peak value determination, an adaptive limit value can be set which changes with the signal curve, in particular after the detection of a local maximum, the adaptive limit value being influenced by various factors in order to ensure that only successive or adjacent maximum values are identified or recognized. The following can serve as an influencing factor or as an influencing variable for the adaptive sensitivity or the adaptive limit value, for example: (normalized) value of the last determined maximum value, width of the last determined peak value or maximum value taking into account zero crossings, turning points or special slope characteristics, time factor or delay factor for linear or non-linear reduction of the threshold or the limit value with increasing distance or with increasing time progress based on the time of the last determined peak and the like.

In particular, it can be provided that the signal curves of the sensors are recorded with a length of 2 seconds to 60 seconds, preferably from 5 seconds to 30 seconds, particularly preferably from 7 seconds to 15 seconds and stored in a buffer for preprocessing and / or further processing .

In a further refinement of the method, the at least three sensors are force sensors and / or weight sensors and / or acceleration sensors which are arranged in and / or under the storage device. The sensors are preferably arranged in the immediate vicinity of the living being.

Figure list

• 1 eine schematische Darstellung einer Lagerungsvorrichtung
• 2 die über eine definierte Zeit aufgenommenen Signale der Sensoren
• 3 das eindimensionale Signal

Further advantageous aspects emerge from the following description of preferred exemplary embodiments with reference to the drawings, in which:

• 1 a schematic representation of a storage device
• 2 the signals from the sensors recorded over a defined period of time
• 3 the one-dimensional signal

DETAILED DESCRIPTION OF THE EMBODIMENTS

1 shows in a highly schematic manner a plan view of a storage device 1 , for example a sick bed or nursing home bed. In the 1 it is indicated that at the four corners of the storage device 1 , for example in the area of the four bed posts, four sensors 2 are arranged, which are preferably designed as force sensors, weight sensors or strain gauges and which apply the force to support elements of a support of the storage device 1 detect or measure. The storage device 1 shows one level E. on. Above the plane E. is the living being 3 or a person 3 arranged. The human being 3 is thus parallel to the plane E. arranged. Furthermore, the longitudinal axis Y and the transverse axis X particularly preferably correspond to the plane E. the longitudinal axis and the transverse axis of the person 3 . The sensors 2 whose measured values also make available four input channels of a controller used in the process, can measure signals or sensor signals m1 , m2 , m3 , m4 that a static load or a weight of the storage device 1 , through parts of the storage device 1 itself and through man 3 , reflect, be measured. At the same time, the sensor signals include m1 , m2 , m3 , m4 , the sensors 2 but also signal elements, which are caused by one-off or repetitive movements of the person 3 and associated changes in the loading of the storage device 1 be brought about.

Furthermore, the storage device 1 also be a seat surface of a seat, in particular a vehicle seat. The sensors can be arranged under the seat surface or on the rails of the seat. This makes it possible for a person to move micro-movements 3 to record as well as the weight and some vital signals from the driver or passengers. Furthermore, a seat recognition can also be realized in this way, it being possible to differentiate whether it is a living being or an object which is placed on a seat. As a result, the seat recognition is not tied to a limit value, but can use at least one vital parameter to recognize whether there is a living being or an object on the seat surface. Furthermore, the driver's vital parameter, in particular the heartbeat, can be detected and it can thus be determined whether the driver is still fit to drive, for example a heart attack of the driver can be detected, on the basis of which the driver can no longer control the vehicle. This detection can be coupled with other driver assistance systems so that a controller steers the vehicle to a hard shoulder, for example in the event of a heart attack in the driver, and brakes the vehicle to a standstill as well as making an emergency call and activating the hazard warning lights. This can prevent serious accidents.

For further improvement, the reaction of the driver to any vehicle movements and vibrations caused by driving can also be detected by the sensors, which show a lot of information about the state of health of the driver or passengers. Airbag settings can also be adjusted, for example, by combining size information from an additional camera installed in the passenger compartment and the determined weight.

bestimmt wird. 2 shows the sensor signals recorded over a defined period of time m1 , m2 , m3 , m4 , the sensors 2 . The a-axis shows the change in the Center of gravity of the living being 3 along a longitudinal axis, in particular a change in the center of gravity of the person 3 from a head part of the storage device 1 , in particular a bed, to a foot part of the storage device 1 . The b-axis shows the change in the center of gravity of the living being 3 along a transverse axis, in particular a change in the center of gravity of the person 3 from a left side of the body to a right side of the body. The t-axis shows the time. This results in a two-dimensional intermediate signal 4th or a flat curve 4th showing the change in the center of gravity of the living being 3 represents in two dimensions over time. This is the change in the center of gravity of the living being 3 determined along the longitudinal axis by the temporal change in the center of gravity of the living being ( 3 ) along the long axis of the plane ( E. ) by the formula $$\text{a}\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m2}\left(\text{t}\right)\left(\begin{array}{c}\text{x0}\\ \text{y0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)-\text{m4}\left(\text{t}\right)\left(\begin{array}{c}\text{x0}\\ -\text{y0}\end{array}\right)$$

is determined.

bestimmt wird.Furthermore, the change in the center of gravity of the living being 3 determined along the transverse axis by the temporal change in the center of gravity of the living being ( 3 ) along the transverse axis of the plane ( E. ) by the formula $$\text{b}\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m4}\left(\text{t}\right)\left(\begin{array}{c}x\text{0}\\ -\text{y0}\end{array}\right)-\text{m2}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ \text{y0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)$$

is determined.

berechnet wird. Das eindimensionale Signal 5 weist eine wiederkehrende Signalfolge 6 auf, welche beispielsweise alle 0,95 Sekunden wiederkehrt. Aufgrund einer Abtastungsfrequenz von beispielsweise 1,05 Hz, ergibt sich der Vitalparameter pro Zeiteinheit, insbesondere eine Herzschlagfrequenz von 64 Schlägen pro Minute. Die Steuerung kann beispielsweise aufgrund einer Mustererkennung, insbesondere aufgrund einer Autokorrelation, die wiederkehrende Signalfolge 6 erkennen und automatisch die Herzschlagfrequenz detektieren. 3 shows the one-dimensional signal 5 which is plotted over time. The one-dimensional signal 5 becomes from the two-dimensional intermediate signal 4th generated, the curvature of the two-dimensional intermediate signal being the one-dimensional signal 5 or the one-dimensional signal ( 5 ) from the two-dimensional intermediate signal ( 4th ) by the formula $$\mathrm{\kappa }\left(\text{t}\right)=\text{b '}\left(\text{t}\right)\ast \text{a ''}\left(\text{t}\right)-\text{a '}\left(\text{t}\right)\ast \text{b ''}\left(\text{t}\right)$$

is calculated. The one-dimensional signal 5 has a recurring signal sequence 6th which recurs, for example, every 0.95 seconds. On the basis of a sampling frequency of, for example, 1.05 Hz, the vital parameters are obtained per unit of time, in particular a heart rate of 64 beats per minute. The control can, for example, on the basis of a pattern recognition, in particular on the basis of an autocorrelation, the recurring signal sequence 6th and automatically detect the heart rate.

List of reference symbols

1

Storage device

2

Sensors

3

Human being / living being

4th

two-dimensional intermediate signal

5

one-dimensional signal

6th

recurring signal sequence

E.

level

m1

Sensor signals

m2

Sensor signals

m3

Sensor signals

m4

Sensor signals

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2040614 B1 [0003]
• WO 2017/056476 A1 [0004]
• EP 1937148 B1 [0005]
• DE 202008018439 U1 [0005]

Claims (17)

Method for the contactless determination of at least one vital parameter of a living being (3), wherein the living being (3) is located in or on a storage device (1) and at least three sensors (2) are arranged in or under the storage device (1) Spanning level (E), the sensors (2) detecting a temporal change in a weight force and / or a temporal change in a center of gravity of the living being (3) within the level (E), the sensor signals (m1, m2, m3, m4) the at least three sensors (2) are forwarded to a controller and recorded over a defined period of time, whereby the recorded sensor signals (m1, m2, m3, m4) are preprocessed by the controller and the sensor signals (m1, m2, m3, m4) be converted into a two-dimensional intermediate signal (4), a one-dimensional signal (5) then being generated from the two-dimensional intermediate signal (4) and from the one-dimensional signal (5) at least one vital parameter of the living being is determined. Procedure according to Claim 1 , characterized in that a recurring signal sequence (6) is present in the one-dimensional signal (5), the controller performing a pattern recognition in order to identify the recurring signal sequence (6). Procedure according to Claim 2 , characterized in that the recurring signal sequence (6) corresponds to the vital parameter per unit of time. Method according to one of the preceding claims, characterized in that, wherein the living being (3) is arranged above the plane (E). Method according to one of the preceding claims, characterized in that the control determines a center of gravity and / or a total weight of the living being (3) on the storage device (1). Procedure according to Claim 5 , characterized in that the determination of the vital parameter is ended when a change in the center of gravity and / or in the total weight of the living being (3) is greater than a defined limit value. Method according to one of the preceding claims, characterized in that four sensors (2) are arranged in or under the storage device (1). Procedure according to Claim 7 , characterized in that the controller is the center of gravity of the living being (3) by the formula $\frac{\text{m1}\left(\text{t}\right)=\left(\begin{array}{c}\text{x0}\\ \text{y0}\end{array}\right)+\text{m2}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ \text{y0}\end{array}\right)+\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)+\text{m4}\left(\text{t}\right)\left(\begin{array}{c}\text{x0}\\ -\text{y0}\end{array}\right)}{\mathrm{4th}}$

definitely. Procedure according to Claim 7 or 8th , characterized in that the two-dimensional intermediate signal (4) represents the temporal change in weight and / or the temporal change in the center of gravity of the living being (3) along a longitudinal axis and along a transverse axis of the plane (E). Procedure according to Claim 9 , characterized in that the temporal change in the center of gravity of the living being (3) along the longitudinal axis of the plane (E) is given by the formula $\text{a}\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m2}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)-\text{m4}\left(\text{t}\right)\left(\begin{array}{c}\text{x0}\\ -\text{y0}\end{array}\right)$

is determined. Procedure according to Claim 9 or 10 , characterized in that the temporal change in the center of gravity of the living being (3) along the transverse axis of the plane (E) by the formula $\text{b}\left(\text{t}\right)=\text{m1}\left(\text{t}\right)\left(\begin{array}{c}\text{y0}\\ \text{x0}\end{array}\right)+\text{m4}\left(\text{t}\right)\left(\begin{array}{c}\text{x0}\\ -\text{y0}\end{array}\right)-\text{m2}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ \text{y0}\end{array}\right)-\text{m3}\left(\text{t}\right)\left(\begin{array}{c}-\text{x0}\\ -\text{y0}\end{array}\right)$

is determined. Method according to one of the preceding claims, characterized in that the one-dimensional signal (5) is generated from the curvature of the two-dimensional intermediate signal (4). Procedure according to Claim 10 and 11th , characterized in that the one-dimensional signal (5) from the two-dimensional intermediate signal (4) by the formula κ (t) = b '(t) * a "(t) - a' (t) * b" (t ) is calculated. Method according to one of the preceding claims, characterized in that the sensor signals (m1, m2, m3, m4) of the at least three sensors (2) are recorded in a time-synchronized manner. Method according to one of the preceding claims, characterized in that the preprocessing of the sensor signals (m1, m2, m3, m4) comprises the removal of a DC voltage offset and / or the use of a high-pass filter and / or the use of a low-pass filter. Method according to one of the preceding claims, characterized in that the at least three sensors (2) are force sensors and / or weight sensors and / or acceleration sensors. Method according to one of the preceding claims, characterized in that the vital parameter is the heartbeat of the living being (3).

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