DE102011113100A1 - Method for detection of ballistocardiogenic or respiratory-caused movements of person on motor vehicle seat, involves designing sensor as ballistographic sensor for detection of ballistocardiogenic or respiratory-caused movements of person - Google Patents

Abstract

The method involves designing a sensor (21) as a ballistographic sensor for detection of ballistocardiogenic or respiratory-caused movements of a person (20), where the sensor emits a ballistographic signal. Another sensor (22) generates a vibration signal as noise reference for the ballistographic signal, where the ballistographically formed sensor is used as latter sensor, which is arranged in a vehicle seat (10) isolated from the vibrations against the person. An algorithm is used for minimizing noise signals of the ballistographic signals by using the vibration signal. An independent claim is included for a measuring arrangement for a vehicle seat of a motor vehicle for monitoring of heart beat or heart rate or respiratory or respiration rate, for fatigue detection and for detecting seat occupancy.

Description

The invention relates to a method for detecting ballistocardiogenic and / or respiratory movements of a person located on a vehicle seat of a motor vehicle according to the preamble of patent claim 1 and a measuring arrangement for carrying out the method according to the invention.

The non-contact monitoring of the heart activity of a person is carried out by recording the on the heartbeat, d. H. The minimal cardiac movements due to the cardiac recoil movements, so-called ballistic movements of the heart by means of ballistographically acting sensors. The breathing of a person also generates a movement in his body, which can also be detected with ballistic sensors.

A generic method is from the WO 2010/045455 A1 known, which generates a ballistocardiogram for monitoring the cardiac function of a person by means of a ballistographic sensor, wherein by means of a second sensor physiological features of the person and noise or interference signals are detected in the vicinity of the first sensor. The signals of the two sensors are fed to a processor unit, which generates from this an interference-signal-reduced ballistic signal which indicates the heart condition of the person. The first sensor is arranged in a vehicle seat of a motor vehicle and generates a ballistographic signal due to the ballistocardiogenic movement of a person sitting on the vehicle seat, while the second sensor is located on the floor of the motor vehicle and serves as a noise signal reference for the ballistic signal. The second sensor is designed as a seismic sensor (geophone) or as an acceleration sensor.

Furthermore, in the WO 2008/102298 A1 a ballistic measuring system described which comprises at least one ballistographic sensor for detecting ballistocardiogenic movements of the body of a person and another sensor for measuring interference, this further sensor from the body of the person vibration-isolated and designed as a seismic sensor which on the floor or is placed on a bed of the person. The noisy ballistographic signal is processed by means of the signal of the vibration-isolated sensor to produce a noise-reduced or noise-free ballistic signal.

The disadvantage of these known methods according to the WO 2010/045455 A1 and the WO 2008/102298 A1 This is because different sensor types are used for the first and second sensors. The use of different types of sensors inherently leads to the generation of different measurement signals, even with the same excitation by the interference signals, whereby the elimination of the interference signals from the ballistic signal is made difficult by suitable calculation methods, ie the evaluation requires the provision of high computing capacity and thus leads to high costs.

The US Pat. No. 7,417,536 B2 describes a method for detecting living beings, in particular a human by detecting the pressure wave generated by the heartbeat or the breathing of the human body in the body by means of a pressure transducer. To generate such ballistic signals, strain gauges, load cells, acceleration sensors, geophones, laser vibrometers, fiber optic sensors or microwave radiometers are proposed as sensors for these pressure transducers. Since the sensor signals contain the ballistographic signals with only low signal strength and low signal-to-noise ratio, an elaborate mathematical algorithm is used for the evaluation. With this algorithm, the signals of different types of sensors are processed in order to perform, for example, a seat occupancy detection for a motor vehicle.

As a measuring arrangement for such a seat occupancy detection two sensors are arranged in the seat frame of a vehicle seat, which detect the pressure acting on the vehicle seat. Furthermore, two further sensors are provided inside the vehicle as well as a further sensor outside the interior of the vehicle. The signals from these sensors are fed to a processor for processing, which uses data from a memory for this purpose. For example, this memory for seat occupancy detection contains first data indicating an occupied seat and second data indicating an unoccupied seat. Also, data can be stored in such a memory with which a certain characteristic condition of a person on the vehicle seat can be detected, such as, for example, their waking state.

This known method and the associated measuring arrangement also require more than two sensors of different types in a cost-disadvantageous manner and a complex mathematical algorithm for which a high computing capacity must be made available. Furthermore, a sufficient data base must be provided in order to achieve a high recognition reliability required for vehicle applications, which in turn leads to a high storage space requirement and thus also entails high costs.

From the article "The Potential of EMFi Sensors in Heart Activity Monitoring"; Jarmo Alametsä J., Värri V., Koivuluoma M., Barna L., 2nd Open ECG Workshop "Integration of the ECG into the EHR & Interoperability of ECG Device Systems", 1-3. April, 2004, Berlin, Germany For example, a study on the use of electromechanical film sensors as ballistographic sensors is known. These sensors are made according to the EP 0 182 764 B1 as a dielectric element made of a flexible and thin plastic film of biaxially oriented polypropylene, which converts mechanical energy into an electrical signal and conversely electrical signals into mechanical energy. This plastic film is coated with a permanent polarized electrically conductive layer. As the pressure on this plastic film changes, electrical charges are generated on the conductive surface which can be measured as current or voltage. The sensitivity of such film sensors is much greater than that of conventional piezoelectric sensors. In the cited article is pointed to the low stability in terms of sensitivity at temperatures above 50 ° C. Therefore, in the application, the ambient temperature should be kept constant at 50 ° C. However, this limits the use in vehicle construction, since such temperatures can not be excluded in a motor vehicle.

The object of the invention is to provide a method for the detection of ballistocardiogenic and / or respiratory movements of a person located on a motor vehicle person of the type mentioned, with a ballistic signal with minimized interference signals and a high signal-to-noise ratio can be generated, which is simple and thus is inexpensive to carry out. It is another object of the invention to provide a measuring arrangement for a vehicle seat of a motor vehicle for carrying out the method according to the invention, which is simple and therefore inexpensive to implement.

The first object is achieved by a method having the features of patent claim 1.

• – ein ballistographisch ausgebildeter Sensor als zweiter Sensor verwendet wird,
• – der zweite Sensor gegenüber der Person schwingungsisoliert in dem Kraftfahrzeugsitz angeordnet wird, und
• – ein Algorithmus zum Minimieren von Störsignalen des ballistographischen Signals mittels des Schwingungssignals verwendet wird.

Such a method for detecting ballistokardiogener and / or respiratory movements of a person located on a vehicle seat of a motor vehicle, in which a first sensor is designed as a ballistographic sensor for detecting the ballistokardiogener and / or respiratory movements of the person and provides a ballistic signal and a second Sensor generates a vibration signal as interference reference for the ballistic signal, according to the invention is characterized in that

• A ballistographically designed sensor is used as the second sensor,
• - The second sensor with respect to the person vibration isolated in the vehicle seat is arranged, and
• An algorithm is used for minimizing interference signals of the ballistic signal by means of the vibration signal.

This method according to the invention utilizes the knowledge that with the use of two ballistographic sensors arranged in the vehicle seat, preferably pressure sensors both for the detection of the ballistic movements and for detecting the vehicle vibrations, sensor signals are generated which have a substantially identical interference signal structure, whereby only a small amount Expenditure is required with respect to an algorithm evaluating the signals and thus only little computing capacity is required. Furthermore, a high signal-to-noise ratio of the processed ballistographic signal of the first sensor is achieved by the almost identical interference signal structure of the two sensor signals.

A method that is particularly easy to implement is obtained if, according to an embodiment of the invention, the first and second sensors are each designed with a directional dependence with regard to the measured variables to be detected. Such with respect to the pressure to be detected a directional characteristic having sensors are arranged in the vehicle seat, that the first sensor is sensitive to pressure only in the direction of a person sitting on the vehicle seat and the second sensor only in the direction of the vehicle floor for measuring vehicle vibrations, so the noise ,

Furthermore, the noise-to-signal ratio of the ballistographic signal processed by the algorithm using the signal of the second sensor is further improved when, according to an embodiment of the invention, the first and second sensors operate according to the same measurement principles. Because so that the signals of these two sensors on a nearly identical Störsignalstruktur.

The second object is achieved by a measuring arrangement for a vehicle seat of a motor vehicle having the features of patent claim 5.

• – der zweite Sensor als ballistographischer Sensor ausgebildet ist,
• – der erste und zweite Sensor im Bereich eines Sitzkissens des Fahrzeugsitzes angeordnet ist, und
• – der zweite Sensor gegenüber der Person schwingungsisoliert angeordnet ist.

This measuring arrangement according to the invention for a vehicle seat of a motor vehicle with a first sensor which is designed as a ballistographic sensor and detects ballistokardiogene and / or respiratory movements of a person located on the vehicle seat person and a second sensor for detecting vibrations of the Motor vehicle is provided according to the invention is characterized in that

• The second sensor is designed as a ballistographic sensor,
• - The first and second sensor is arranged in the region of a seat cushion of the vehicle seat, and
• - The second sensor is arranged vibration isolation with respect to the person.

Since both sensors, which are each preferably designed as pressure sensors, are installed in the vehicle seat, compared with the prior art, in which the second sensor is mounted outside the motor vehicle seat, assembly costs can be reduced since both sensors can be mounted simultaneously, only one Wiring harness must be guided to the vehicle seat and only one connector is required.

In one embodiment of the invention, it is provided that the first and second sensor is each formed with a directional dependence with respect to the measured variables to be detected; the first sensor is arranged in the region of the seat cushion such that the ballistocardiogenic and / or respiration-related movements of the person are detected, and the second sensor is arranged in the region of the seat cushion such that only the vibrations of the motor vehicle are detected, but not the ballistographic movements the person.

The use of such directionally sensitive pressure sensors, it is no longer necessary to equip the vehicle seat with special vibration isolation means.

According to a development of the invention, it is particularly advantageous if the first and second sensors operate according to the same measuring principles, whereby the noise signal ratio of the ballistographic signal processed with the algorithm using the signal of the second sensor is further improved, since the signals the two sensors have a nearly identical Störsignalstruktur.

In a further embodiment of the invention, the vehicle seat for vibration isolation of the second sensor relative to the person on a vibration-isolating means, which is preferably designed as a damping mat. Thus, the ballistographic movements of a person sitting on the vehicle seat can be specifically isolated from the second sensor.

A cost-effective development of the invention results when the second sensor is arranged in the edge region or in a corner region of the seat cushion of the vehicle seat. Thus, such an arrangement of the second sensor in the vehicle seat already achieves a largely vibration-isolated position for this sensor since the ballistographic movements are largely no longer detectable in the edge region of the seat cushion since the sensitivity of the second sensor is insufficient for this purpose.

Finally, according to a last advantageous development of the invention, an evaluation unit is provided for evaluating the sensor signals of the first and second sensors, which generates a ballistographic signal with minimized interference signals by means of the sensor signal of the second sensor, for which purpose also a control unit of a suitable assistance system of the vehicle is usable.

The measuring arrangement according to the invention can advantageously be used for monitoring the heartbeat and / or the heartbeat frequency and / or the respiration and / or the respiratory frequency, for which purpose a corresponding control device is provided, which upon detection of a life-threatening cardiac condition or lack of breathing of the vehicle driver the vehicle automatically performs an emergency stop and additionally sends an emergency signal to an external emergency station.

Furthermore, it is possible to use the measuring device according to the invention for fatigue detection of a vehicle driver by the processed ballistic signal is evaluated with minimized interference signals with regard to the fatigue of the driver.

Finally, a seat occupancy detection can be realized with the measuring arrangement according to the invention, since the detection of a heartbeat movement or a respiratory movement indicates the occupancy of the vehicle seat with a person.

The invention will now be described in detail by means of embodiments with reference to the accompanying figures. Show it:

1 a schematic representation of a measuring arrangement in a vehicle seat of a motor vehicle for carrying out the method according to the invention as an exemplary embodiment,

2 a schematic representation of a vehicle seat according to 1 with an alternative measuring arrangement, and

3 a schematic representation of a vehicle seat according to 1 with a further alternative measuring arrangement.

The 1 to 3 show a vehicle cab shown schematically 1 a motor vehicle with a vehicle seat 10 which of a person 20 is occupied.

This vehicle seat 10 , which consists of a seat cushion 11 and a seat back 12 exists is on a basis 13 , for example, mounted on seat side rails. The seat cushion 11 includes a first sensor 21 and a second sensor 22 in different measuring arrangements according to 1 to 3 , where both sensors 21 and 22 are designed as ballistographic pressure sensors.

According to 1 become the sensor signals of these two sensors 21 and 22 a functional block 30 fed, in turn, with other functional blocks 31 to 34 is connected and whose functions will be explained below.

Also the sensors 21 and 22 in the according to the 2 and 3 shown vehicle seats 10 be with such function blocks 30 to 34 connected, however, are for the sake of simplicity in these 2 and 3 not shown.

According to 1 is the first sensor 21 in the seat area adjacent area of the seat cushion 11 of the vehicle seat 10 arranged so that the ballistocardiogenic and respiratory movements of the person 20 be detected by generating appropriate ballistic signals. This ballistic signal also contains the interference caused by vibrations of the vehicle. On the seat side facing away from the seat cushion 11 is the second sensor 22 arranged by a mechanical damping mat 23 from the first sensor 21 is vibration isolated, so this second sensor 22 essentially only the vibrations originating from the vehicle can be detected and thus an interference reference signal for the ballistic signal of the first sensor 21 represents.

According to 1 are both sensors 21 and 22 formed as sensor pressure mats and therefore extend almost over the entire seat of the seat cushion 11 ,

The sensor signals of the two sensors 21 and 22 be according to 1 an evaluation unit 30 supplied to the signal processing to the interference signals from the second 22 Sensor are detected from the ballistographic signal of the first sensor 21 to eliminate as far as possible and to obtain a large signal-to-noise ratio. In the simplest case, the signals of both sensors 21 and 22 subtracted from each other in the time domain or in the frequency domain, thereby canceling out the interfering signals in the ballistic signal. This is therefore extremely effective, since on the one hand both sensors in principle at the same location, ie in the seat cushion 11 of the vehicle seat 10 are mounted and therefore exposed to identical vibrations or interference signals and on the other hand, two pressure sensors, in particular on the same measuring principle working sensors 21 and 22 are used and therefore their Störsignal structures are largely identical. In addition to the method of subtracting the sensor signals for the purpose of signal processing, it is also possible to use other mathematical methods or algorithms known to the person skilled in the art.

As ballistographic sensors 21 and 22 can according to 1 Directionally sensitive sensors, so sensors are used with a directional characteristic with respect to the measured variables to be detected. This is the first sensor 21 in the seat cushion 11 mounted so that it is only "up", ie in the direction of the person 20 pressure sensitive, while the second sensor 22 is arranged so that it is only "down", ie in the direction of the vehicle floor pressure-sensitive. This can be done on a damping mat 23 be waived.

According to 1 are the two sensors 21 and 22 inside the seat cushion 11 arranged. In contrast, a measuring arrangement of these sensors 21 and 22 according to 2 also between the base 13 of the vehicle seat 10 and the vehicle seat 10 , so below the seat cushion 11 to be assembled. With such a measuring arrangement, it is sufficient to use sensors 21 and 22 with only a small surface area compared to the seat surface of the seat cushion 11 to use. Also in this measuring arrangement are the two sensors 21 and 22 through a mechanical damping layer 23 separated, with the first sensor 21 seated and the second sensor 22 is arranged base side.

Another measuring arrangement with two sensors 21 and 22 in the seat cushion 11 a vehicle seat 10 shows 3 where the first sensor 21 as a sensor mat substantially in a central region of the seat surface of the seat cushion 11 is arranged while the second sensor 22 in the area of the front edge of the seat cushion 11 There, there is no or only slight ballistic movements of the person 20 can be detected. Thus, from this second sensor 22 essentially only interference signals or the vibrations of the vehicle detected. This second sensor 22 can be over the entire width of the seat cushion 11 extend, or only in a corner region of the seat cushion 11 to be ordered. Also, the side edge area of the seat cushion 11 for receiving such a second sensor 22 suitable.

The sensor signals of the sensors 21 and 22 in the 2 and 3 shown measuring arrangements are accordingly 1 as well as an evaluation device 30 supplied for signal processing to produce a noise-minimized ballistic signal.

So according to 1 such a ballistic signal to a controller 31 be supplied to an emergency stop assistant to detect a faulty heart or respiratory activity or a missing heartbeat or lack of respiration on the vehicle seat 10 sitting person 20 , possibly a driver's inability to drive 20 means to have a secured automatic emergency stop maneuver of the vehicle carried out. At the same time, in such an emergency via a transmitting device 33 a corresponding emergency call to a rescue center be dropped, in addition, also position data of the vehicle can be transmitted.

Furthermore, this noise-minimized ballistic signal for a seat occupancy detection for pilot control of an airbag control unit 32 be used because a detected heart or breathing activity indicates a vehicle seat occupied by a person.

Finally, the noise-minimized ballistic signal for fatigue detection can be used, so that a display 34 an optical and / or audible warning signal with a detected fatigue of the driver 20 is produced.

As ballistographic pressure sensors are in addition to piezoresistive and piezoelectric sensors and capacitive sensors.

LIST OF REFERENCE NUMBERS

1

cabin

10

vehicle seat

11

Seat cushion of the vehicle seat 10

12

Vehicle back of the vehicle seat 10

13

Base of the vehicle seat 10

20

person

21

first sensor

22

second sensor

30

evaluation

31

Control unit for assistance function for emergency stop

32

Airbag control unit

33

Emergency call transmission unit

34

display

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• WO 2010/045455 A1 [0003, 0005]
• WO 2008/102298 A1 [0004, 0005]
• US 7417536 B2 [0006]
• EP 0182764 B1 [0009]

Cited non-patent literature

• "The Potential of EMFi Sensors in Heart Activity Monitoring"; Jarmo Alametsä J., Värri V., Koivuluoma M., Barna L., 2nd Open ECG Workshop "Integration of the ECG into the EHR & Interoperability of ECG Device Systems", 1-3. April, 2004, Berlin, Germany [0009]

Claims (15)

Method for detecting ballistocardiogenic and / or respiratory movements of a vehicle seat ( 10 ) of a motor vehicle ( 20 ), in which a first sensor ( 21 ) as a ballistographic sensor for detecting the ballistocardiogenic and / or respiratory movements of the person ( 20 ) and supplies a ballistic signal and a second sensor ( 22 ) generates a vibration signal as a disturbance reference for the ballistic signal, characterized in that - a ballistographically formed sensor as a second sensor ( 22 ) is used, - the second sensor ( 22 ) towards the person ( 20 ) vibration isolated in the motor vehicle seat ( 10 ), and an algorithm for minimizing interference signals of the ballistic signal by means of the oscillation signal is used. Method according to claim 1, characterized in that the first and second sensors ( 21 . 22 ) is formed in each case as a pressure sensor. Method according to claim 1 or 2, characterized in that the first and second sensors ( 21 . 22 ) is formed in each case with a directional dependence with respect to the measured variables to be detected. Method according to one of the preceding claims, characterized in that the first and second sensors ( 21 . 22 ) work according to the same measuring principles. Measuring arrangement for a vehicle seat ( 10 ) of a motor vehicle with a first sensor ( 21 ), which is designed as a ballistographic sensor and ballistokardiogene and / or respiratory movements on the vehicle seat ( 10 ) person ( 20 ) and a second sensor ( 22 ) is provided for detecting vibrations of the motor vehicle, characterized in that - the second sensor ( 22 ) is designed as a ballistographic sensor, - the first and second sensor ( 21 . 22 ) in the region of a seat cushion ( 11 ) of the vehicle seat ( 10 ), and - the second sensor ( 22 ) towards the person ( 20 ) is arranged vibration isolated. Measuring arrangement according to claim 5, characterized in that the first and second sensor ( 21 . 22 ) is formed in each case as a pressure sensor. Measuring arrangement according to claim 5 or 6, characterized in that the first and second sensor ( 21 . 22 ) is formed in each case with a directional dependence with regard to the measured variables to be detected, - the first sensor ( 21 ) in the region of the seat cushion ( 11 ) that the ballistocardiogenic and / or respiratory movements of the person ( 20 ), and - the second sensor ( 22 ) in the region of the seat cushion ( 11 ) is arranged, that the vibrations of the motor vehicle are detected. Measuring arrangement according to one of claims 5 to 7, characterized in that the first and second sensor ( 21 . 22 ) work according to the same measuring principles. Measuring arrangement according to one of claims 5 to 8, characterized in that for the vibration isolation of the second sensor ( 22 ) towards the person ( 20 ) a vibration isolating agent ( 23 ) is provided. Measuring arrangement according to claim 9, characterized in that as vibration-isolating means a damping mat ( 23 ) is provided. Measuring arrangement according to claim 5 to 8, characterized in that the second sensor ( 22 ) in the edge region or in a corner region of the seat cushion ( 11 ) of the vehicle seat ( 10 ) is arranged. Measuring arrangement according to one of claims 5 to 11, characterized in that an evaluation unit ( 30 ) for generating a ballistic signal with minimized interference signals by means of the sensor signal of the second sensor ( 22 ) is provided. Use of the measuring arrangement according to one of the preceding claims 5 to 12 for monitoring the heartbeat and / or the heartbeat frequency and / or the respiration and / or the respiratory frequency. Use of the measuring arrangement according to one of the preceding claims 5 to 12 for detecting fatigue. Use of the measuring arrangement according to one of the preceding claims 5 to 12 for seat occupancy recognition.

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