WO2019068852A1

WO2019068852A1 - Pressure measuring and adjusting system for force absorbing and force distributing systems

Info

Publication number: WO2019068852A1
Application number: PCT/EP2018/077100
Authority: WO
Inventors: Bjorn VAN KEYMEULEN
Original assignee: P2Solutions Cvba
Priority date: 2017-10-06
Filing date: 2018-10-05
Publication date: 2019-04-11

Abstract

The invention relates to a force absorbing and force distributing system, comprising a force absorbing and force distributing article, such as for example a foam or rubber article, provided with integrated sensor system for monitoring the static pressure within the force absorbing and force distributing article.

Description

PRESSURE MEASURING AND ADJUSTING SYSTEM

FOR FORCE ABSORBING AND FORCE DISTRIBUTING SYSTEMS

Technical field

The invention relates to force absorbing and force distributing systems, e.g. mattresses, comprising of force absorbing and force distributing articles such as for instance foam or rubber articles. A system and method is described for monitoring static as well as dynamic pressure within such force absorbing and force distributing systems. Hence, the force absorbing and force distributing system further comprises of a sensor system enabling such monitoring. A production process is described for manufacturing such force absorbing and force distributing system and article provided with a sensor system for mentioned monitoring purposes. Finally, a system and method is described to use the measured static and dynamic forces in order to steer actively a pressure adjusting system. A production process for such pressure adjusting system is also part of the invention.

Background of the invention

Currently a lot of systems are on the market that can perform pressure measurements, all having their specific disadvantages. These systems are, to the author's knowledge, based upon piezoresistive local measurements, piezoelectric measurements and/or movement measurements by means of using accelerometers or gyroscopes.

Piezoresistive measurements need typically a conductive electrode layer on top and bottom of a resistive material from which the resistance (P) is a function of the applied pressure P. The conductive electrode layers need to have a very good conductance and the conductive material has to be applied over the entire area of the force-dependant resistive material in order to achieve effective and reproducible results. For this reason, the sensors are produced on (flexible) foils, whereas such foils are cut out in a certain sensor shape, and provided with a conductive circuit herewith generating the sensor foil end product. This type of sensor is e.g. used for flat button applications, and can be used to measure pressure inside the force absorbing articles. However, due to the typical dimension and cost of the sensor foil based product, the measurement area for performing static measurements is always limited. As an example, in the art PET foils with printed silver electrodes as conductive path on top and carbon in between are used, being rather expensive.

Piezoelectric and accelerometer measurements can inherently only perform dynamic measurements.

Currently available off-the-shelf technologies mainly have disadvantages for large surface applications, such as for instance monitoring a bed mattress, due to the fact that for achieving absolute values of pressure and pressure differences, they typically can only perform local measurements. The idea of covering the entire surface of a force absorbing article (such a mattress foam) with a piezoresistive sensor layer, is practically not done because of cost reasons. Such product, although being rather reliable, could never be sold on the market. Moreover, from a usage point of view, adding plastic-like foils to a bed article product would introduce large discomfort for the end user, especially because the sensing layer has to be rather close to the surface of the article. Considering dynamic measurement solutions, the piezoelectric and accelerometer products can only measure relative values or differences of forces and are therefore also very limited regarding end applications. As an example, dynamic measurements may lead to monitoring heartbeat and breathing, although performing a body (pressure) profile within a mattress would not be feasible. Next to this, piezoelectric sheets have the same cost and discomfort issues as the piezoresistive technology. The accelerometer and gyroscope solution can only measure local movements, which implies that a lot of sensors have to be integrated in order to achieve reproducible results. This brings along significant budget need and discomfort.

Aim of the invention

The aim of the invention is to provide a force absorbing and force distributing system, comprising a force absorbing and force distributing article, with integrated sensor system for monitoring the absolute pressure within this force absorbing and force distributing article. In particular, large surface, high volume or large-scale sensing integrated applications or systems and accompanying measurement methods are aimed at in an improved manner, delivering a large variety of monitoring data. Due to the possibility of measuring static pressure a pressure regulating system can be built by means of actuators, e.g. air pillows, which adjusts the measured pressure distribution towards a predefined pressure distribution.

Summary of the invention

In a first aspect of the invention a system is provided, comprising a force absorbing and force distributing article, and a sensor system, for monitoring absolute value pressure within the force absorbing and force distributing article. A force absorbing and force distributing article is an article or device comprising of a material having force absorbing and force distributing characteristics. As an example, foam or rubber have strong force absorbing characteristics, but also other materials may be considered. Moreover, the materials as referred to, not only absorb large or heavy, or heavy impact forces, but also further distribute the absorbed forces within the material of the article itself, due to its material structure and physical characteristics.

In a second aspect of the invention a monitoring method is provided, for monitoring absolute value pressure within a force absorbing and force distributing article, being part of a force absorbing and force distributing system with integrated sensor system for monitoring purposes.

In a third aspect of the invention a sensor system is provided, for monitoring absolute value pressure within a force absorbing and force distributing article.

In a fourth aspect, a system is disclosed comprising and using actuators in order to rearrange the measured pressure distribution to a predefined pressure distribution. A method accordingly for rearranging the pressure distribution to a predefined pressure distribution by means of such system is also provided.

In a fifth aspect, a system is disclosed wherein the damping ratio of the system can be adjusted on the fly, by means of actuators and preferably combined with the fourth aspect of the invention. As everything in our environment becomes smarter also force absorbing articles have opportunities to support the ecosystem with additional sensor data. Such force absorbing system is for instance a smart mattress or a smart mattress topper. With the present invention, a measurement is provided enabling monitoring the static and dynamic pressure inside the mattress and identifying the pressure points of a person's body (lying or sitting on the mattress) together with its position and movement. A lot of applications become possible with the force absorbing and force distributing system having an integrated sensor system in accordance with the present invention, e.g. respiration and heartbeat measurements, detection of symptoms of sleep disorders like restless legs, including detecting which type of mattress fits the best for a certain person based upon the measured pressure distribution.

With the force absorbing and force distributing system and accompanying measurement method for monitoring force within a force absorbing and force distributing article according to the present invention, systems, methods and/or products are provided that are useful for, but not limited to, the consumer as well as the healthcare and medical segment of the mattress and foam market. For instance, in the health market, a possible application or product could be a mattress detecting the presence of a human body in bed, together with its position, activity, and heartbeat and respiration rate. All this together brings along a monitoring system for nurses, herewith actively preventing e.g. pressure ulcers problems etc. With respect to the consumer as well as the medical market, an active feedback system may be provided, wherein the pressure sensors monitor the pressure relief of a person and steer actuators which are able to modify the pressure distribution in order to have an optimal stress distribution or profile over the mattress leading to improved sleep quality. Moreover, assistance to stand up, to avoid snoring, to avoid pressure ulcers, to wake up, etc may herewith be provided. Examples of such actuators are for instance regulating bed bases, mattresses including air pillows, etc. Next to the adjustable local pressure, also the damping ratio can be chosen on the fly by means of these actuators, e.g. pneumatic elements.

One of the advantages of the system in accordance with the present invention is that it is cost effective to produce. Furthermore, the sensors are integrated within textile, which is already commonly used in bedding, mattress and foam products. In other words, no additional manufacturing processes are needed and no discomfort is added in comparison with the current product range according to the art. Next to economical and manufacturing advantages, the performance is also improved, due to the fact that this system makes it possible to monitor static force (cfr. absolute values) and dynamic force by means of one single sensor technology in contrary with the most other systems, particularly for large scale or big surface applications. Regarding this latter it is further noted that the system is more in particular not a local system, meaning that the system is distributed over an entire area, which is very beneficial for our large application and especially when considering a system regulating the bed base. A particular manufacturing process is provided with the invention, for the production of such large-scale sensor systems. Depending on the application, a roll-to-roll or either sheet based production process can be chosen.

Compared to state-of-the-art systems, the invention provides in a simple and fast measurement solution. Very small changes in force applied down to IN and lower, or the associated applied pressure,can be measured very rapidly, e.g. every 5ms, resulting in the fact that a dynamic as well as a static measurement can be interpreted. Static measurement is possible due to the remaining steady state value of the sensor when a load is applied. Dynamical measurements are possible due to the high sensitivity in combination with the high sample rate, which makes it possible to see minor vibrations, movements, etc. According to the prior-art, either a dynamic or a static measurement is performed accurately by one sensor technology. Advantages in consumer, medical and healthcare applications can be observed with the force absorbing and force distributing system and article in accordance with the present invention.

Brief description of the drawings

Figure 1 illustrates schematically an embodiment of a sensor integrated and force absorbing system in accordance with the invention.

Figure 2 illustrate schematically an embodiment of a sensor integrated and force absorbing system in accordance with the invention, (a) in case no pressure is applied, (b) when a pressure is applied by a load LI, (c) when a larger pressure is applied by load LI + L2, and (d) depicts the graphical representation of the effect of the three cases.

Figure 3 shows a possible configuration of sensor electrodes provided within a woven textile in accordance with the present invention.

Figure 4 illustrates an embodiment of a woven textile with integrated sensor electrodes in accordance with the present invention, further provided with measurement electronics and interconnection guidelines.

Figure 5 shows an embodiment of a woven textile with integrated sensor electrodes in accordance with the present invention, further illustrating a connected bus system.

Figure 6 graphically represent embodiments of (a) an applied pressure profile and (b) measured capacitance profile, including (c) schematic representation of pressure distribution onto a sensor integrated woven textile, in accordance with the invention.

Figure 7 illustrates an embodiment of a two-person mattress, or another force absorbing article, for which a (limited) two-dimensional pressure measurement can be performed in accordance with the invention.

Figure 8 illustrates another embodiment of a two-person mattress, or another force absorbing article, for which a (limited) two-dimensional pressure measurement is performed in accordance with the invention.

Figure 9 illustrates yet another embodiment of a two-person mattress, or another force absorbing article, for which a (limited) two-dimensional pressure measurement is performed in accordance with the invention. Figure 10 illustrates how the signals within a particular zone of the mattress or force absorbing article can be calculated in accordance with the invention. Figure 11 shows the embodiments of Figure 7-9 and possible corresponding sensor zones for measuring the pressure applied on these particular zones of a mattress, or another force absorbing article, in accordance with the invention.

Figure 12 illustrate an embodiment of a two-person mattress, or another force absorbing article, based on Figure 9's architecture, but implementing parts with a large amount of small sensor zones, as well as parts with little amount of large sensor zones in accordance with the invention. Figure 13 illustrates how the measured signals can be related to the pressure in the different zones of toppers, foams, mattresses or other force absorbing articles in accordance with the invention.

Figure 14 illustrates schematically a roll-to-roll process for a production method of a mattress or force absorbing article in accordance with the invention.

Figure 15 illustrates schematically a sheet-based process for a production method of a mattress or force absorbing article in accordance with the invention. Figure 16 illustrates particular production method processes of a mattress or force absorbing article according to the application (e.g. where the electronics are to be applied) and in accordance with the invention.

Figure 17 shows an embodiment of how an air cell based pressure adjusting system can be built in accordance with the invention.

Figure 18 shows another embodiment of how an air cell based pressure adjusting system can be built, in accordance with the invention. Figure 19 shows yet further embodiment of how an air cell based pressure adjusting system can be built in accordance with the invention. Figure 20 illustrate embodiments of possible air bag profile shapes within possible air gap profile shapes in accordance with the invention. Figure 21 shows an embodiment of the combination of a pressure sensing absorbent article with an integrated pressure regulating system in accordance with the invention.

Figure 22 illustrates schematically how the regulation system can work in case a uniformly distributed pressure profile is required in accordance with the invention. Figure 23 shows an embodiment of how air can be accumulated or discharged in the airbags in accordance with the invention.

Detailed description of the invention The developed sensor integrated system 100 exists of two main parts, as can be seen in the Figure 1. The top part is a so-called force or pressure absorbing layer 101, which can be e.g. a latex or a polyurethane (PU) foam material. Under this layer the sensor layer 102 is applied. The sensor layer 102 typically contains an electrode system. The electrodes are made of a good conductive material, such as copper, stainless steel, aluminium, etc. Preferably a textile carrier is used to apply the electrodes, but also other embodiments are possible including but not limited to, printing ink electrodes or glueing yarn or wire electrodes directly on the force absorbing layer. Several methods can be used to apply electrodes on textile, for instance by means of printing, sewing, etc. But the most straightforward way is weaving the electrodes in the textile during the weaving process. One of the advantages of using a woven textile is that this type of textile is currently already used to pour foam, e.g. latex, on top of it for some known applications. Making use of state-of-the-art pouring techniques onto textile, and providing the woven textile with woven sensors, some production steps, including the sensor integration, can occur during the current production process. Furthermore, with the present invention, problems arising during aligning and accurate positioning of sensors, is no longer an issue now, because of the sensor integration in the roll-to-roll process, wherein a full automated sensor alignment process is foreseen. So, regarding manufacturability, there is a clear advantage due to the fact that the sensor integration can easily become part of a roll-to-roll process, i.e. during the production of the mattress itself, whereas referring to systems in the art the sensor integration is applied afterwards (after-placement). Moreover, according to the state-of-the-art, the sensing components are not applied within the mattress itself, but underneath in the bedframe or between the bedframe and the mattress. With the invention, the sensors can be integrated closer to the upper surface of the mattress, and hence closer to a person's body resulting in a more accurate representation of the pressure experienced by the body, when person is lying down on the mattress.

Figure 2 illustrates schematically a sensor integrated and force absorbing system 200, 210 in accordance with the invention, in relaxation phase depicted in Figure 2a, and in pressed phase respectively as shown in Figure 2b and Figure 2c. According to an embodiment the pressure absorbing layer 201 - onto which a pressure sensor 202 is applied - is made for instance of latex foam and characterized by a certain capacitance as schematically represented in dashed lines 203 in Figure 2a. Whenever a load LI, L2 or weight is put onto the foam 204, 214, a force is applied, and hence the inherent capacitance of the absorbing layer 204, 214 will increase towards a capacitance 206, 216 as depicted in Figure 2b and Figure 2c respectively. The more weight is applied, as in Figure 2c with load LI and L2, the more the foam is pressed, and hence the larger the capacitance 216 will become. Figure 2d illustrates the measured discretely increasing capacitance 230 in case no load or pressure is applied as depicted by block 231, in case an intermediate load LI is applied as represented by block 232 and in case a large load L1+L2 is applied as shown with block 233. This is only a conceptual representation of the sensing mechanism, meaning that all intermediate applied forces could also be measured by means of this system, see further.

According to an embodiment of the present invention, a typical configuration of woven sensor electrodes 301, measuring the applied force in one direction onto a woven textile 300 is drawn Figure 3.

Referring now to Figure 4, next to the electrodes 401 we need measurement electronics 402 to read the information of the sensors within the sensor substrate, e.g. a woven textile, 400. This measurement electronics 402 within the dashed line comprise of an impedance measurement system, according to a particular embodiment of the invention a capacitive measurement, which can be implemented by means of e.g. a microcontroller circuit 405 onto a PCB. In order to interconnect the electrodes 401 with the measurement circuit 405, crimp connectors 403 can be used, combined with electrical interconnection means 404. In one embodiment these interconnections means 404 can be a flexible printed circuit board where the crimp connectors are soldered on top of this flexible printed circuit board. . In order to access the electrodes in an efficient way a woven textile can be produced as depicted schematically with representation 410 zoomed out from drawing above. In the centre of this schematic representation 410 the conductive electrode 401 is surrounded locally with free space 415 within the dotted-line canvas, such that a proper electrical interconnection between said electrode 401 and the crimp connector 403 can be established. This free space 415 can be created by means of removing some non- conductive yarns in weft and warp direction, or visa versa, 411, 412 during weaving. It is an advantage to create a free space 415 (around the conductor 401) which is rectangular shaped with y > x, in order not to disturb the stability of the weaving structure. The stability of the structure is needed to keep the conductive electrodes 401 on their initial position during all further processes. In an embodiment, it is preferable to have a ratio of y/x of 2 to 4 with for instance a length y of 5mm to 10 mm and a width x of 2mm to 5mm.

As an example, in Figure 4 four measurement zones 406 are included. For some applications, we need significantly more zones. The number of measurement zones 406 can be increased either by increasing the number of electrodes 401 for one microcontroller 405, and/or by increasing the number of microcontrollers 405. The number of electrodes 401 per microcontroller 405, and the distance d between the microcontroller 405 and the electrode 401, are limited due to the influence of the distance d on the accuracy of the capacitive measurement. According to an embodiment, the distance d between the measurement equipment and the respective electrodes is preferably limited to 20cm to maintain measurement accuracy. According to a further embodiment, an example of a woven textile 500 with sensor grid comprising of 20 measurement zones is illustrated in Figure 5. The system works as follow. An electrode 501 measures the capacitance of the environment. Non-compressed foam has a certain basic capacitance C as shown in Figure 2. If one compresses this foam a change in capacitance is noticed due to the fact that the foam particles become denser because of the suppression. A pressed foam capacitance Cp can now be measured. Due to the fact that the foam its suppression is a function of the applied pressure one can say that the measured capacitance is a function of the applied pressure or compression. Further depicted in Figure 5, is a master microcontroller 502 and three slave controller boards 503, all connected to a bus system 504 - such as for instance I2C (Inter-Integrated Circuit) being a multi-master, multi-slave, packet switched, single-ended, serial computer bus - for further transferring the acquired and measured data from the sensor electrodes 501 and connected electronic circuit.

Examples of applied pressure profile 602 and measured capacitance profile 605 are illustrated in the graphs of Figure 6. On the left side in Figure 6(a) the force 602 [in Pascal] applied by normalized equipment is shown as a function of time 601 [in minutes or seconds]. Applied pressure 602, and thus peaks 606 occur for with a period 603 of 5 minutes in our test profile. On the right side in Figure 6(b) the measured capacitance 605 is given as a function of time 604. Further in this figure, three curvatures 607, 608, 609 are present due to the fact that the pressure was applied with a stamp having a pressure impact profile 611 of 20cm diameter ds while every sensor (or electrode 610) zone has a width w of only 10cm, as shown in Figure 6(c). The black curve 607 in Figure 6(b) represents the measured capacitance (which can be mapped with corresponding applied pressure) just beneath or under the stamp, while the red 608 and blue 609 curves illustrate measurements at the sides 612, 613 of the stamp. Further referring to Figure 6, there is a clear relation between the input of the system, i.e. pressure 602, and the measured output of the system, i.e. capacitance 605.

Table 1 summarizes the outcome of the performance test. On the left side of the table the specimen comprising particular type of material is defined. When no sensor layer is indicated in this column the sensor layer is provided on top of the defined specimen.

Following values are displayed in this table:

• hO: gives us the initial height of the mattress stack.

• F65%: gives the force applied for in Newton to suppress the stack with 65%.

• meas: indicates the measured value at the moment when the mattress is suppressed by 65%.

• N/meas: gives a preliminary indication how accurate the system is by indicating how many Newton corresponds with one measurement step. The higher this value the less accurate the system is. Specimen : hO(mm) Hw% F25% F40 F65% meas N/mea s

SP000M 178,9 23,09 . 89,39 178,1 492,42 279 1,76

SP000M+sensor+2xUA050F#4T 257,3 23,09 63,19 138,46 448.69 270^"* 1,66 sensor+2xUA050F#4T+2xTN3110#4P 235,6 32,7 42,03 70,37 240,36 275 0,87

HR35-150N mid 233,8 ^" 23,55 187,63 365,96 848.69 360 2,36

HR35-125N mid 232,8 26,97 169,41 339,34 807,92 259 3,12

LA0001 zone mid 237 28,85 93,53 207,82 705,8 392 1,80

LA0001 zone head 229,8 28,64 99,2 209,43 675,55 297 2,27

LA0073 zone mid 1 243.1 28,84 112,68 255,36 832,29 259 3,21

LA0073 zone head 243,3 28,39 101,27 224,56 702,52 270 2,60

LA0052 zone mid 241,9 27,82 108,78 240,55 784,23 356 2,20

LA0052 zone head 237,7 28,04 95,75 210,3 680,83 296 2,30

HR35-125+ ^~ 300.9 30,22 109,6 265,68 733.24 314 ^" sensortopper+viscoblue4+viscoyellow2,5 2,34

HR35-125 315,3 29,8 104,89 254,65 721,6 334 sensortopper+viscoblue4+viscoyellow4 2,16

HR35-125+ 314,2 133,54 301,2 803,85 309 sensortopper+viscobleu4+vxxxab4 2,60

Table 1: summarized measurement results

As can be seen in Table 1 the accuracy of the system (N/meas) depends upon the test specimen. Nevertheless, the variance amongst the different samples is not large (this due to a calibration step of the hardware), the accuracy value is in general between 2 and 3 Newton per measured digit. Furthermore, it can be seen that adding other foam materials on top of the smart latex does not influence the accuracy in a negative way. While comparing the measurement accuracy of specimen HR35-125N+sensor with the stack HR35-125N+sensor+viscoblue4+viscoyellow4, the measurement accuracy is initially 3,12 Newton per measurement step whereas in the case with polyurethane (PU) on top the accuracy is calculated as 2,16 Newton per measurement step, or else the measurement is about 33% more accurate by applying visco-elastic PU on top of the initial stack.

It is noted that the tests were performed with arbitrary stacks and materials and are only given into detail to display the possibilities of the product. Furthermore, it is mentioned that the test samples were evaluated without glueing.

Abovementioned description is related to the measurement and integration principles needed for a mattress or force absorbing article with a one-dimensional pressure measurement. Figure 7, 8 and 9 illustrate embodiments of mattresses or force absorbing and force distributing articles for which a (limited) two-dimensional pressure measurement is executed. Figure 7 shows the approach where the measurement electronics 702 are fixed in the middle of the mattress substrate 700. The sensors or sensor electrodes 701 are cut at the locations where the sensor zones 706 end, in this case in the middle of the substrate 700, whereas each of the sensor zones 706 begin at the long edges left 703 and right 704 respectively of the mattress 700. Moreover, the electronic boards 705 can be used to interconnect the left as well as the right side of the sensor layer. In other words, one single board 705 can operate for left and right side sensor zones 706 (all or not clustered as described with Figure 4). In Figure 8 an alternative for the embodiment of Figure 7 is shown. The sensors 801 in Figure 8 are also cut at the end of the sensor zones 806 in the middle of the mattress 800, but the measurement electronics 802 and boards 805 are now fixed to the long edges 803, 804 of the mattress substrate 800. This has significant advantages when the substrate 800 has a longer lifetime than regular electronic equipment. With this easy- access-to-electronics design, the electronics can be exchanged and replaced on the fly. In one embodiment an electromechanical structure, comparable with the ones used for SIM-card within cell phones, can be used to exchange the electronic circuitry when it fails due to aging. Drawback with this embodiment however, is that twice as much electronics boards are needed. A further alternative is depicted in Figure 9. Now only half of the sensor electrodes are cut, i.e. whereas 50% run over the entire width, 50% will only run over the half of the mattress substrate 900 and the cut

901 and uncut 90 sensors come together in the middle of the mattress 900 whereas they end together at one of the long edges 903 - here left - of the mattress 900. Now the electronics 902 are fixed at only one long edge 903 of the substrate 900, more specifically the long edge 903 where both sensors 901, 90 are present. With the embodiment of Figure 9 only one long edge 903 needs to be provided with electronics boards 902 while enabling measurements in two dimensions. This combines the advantage of less electronic boards with the possibility to change the electronics which can break due to aging.

Figure 10 depicts how the signals for the closest zone 906 to the measurement electronics 902 are calculated and how the signals for the furthest zone 906' away from the measurement electronics

902 are calculated. If one applies a load and an associated pressure 1006 on the first zone 906, one can see that the first 901 and the second 901' sensor will sense pressure. While one applies pressure 1006' on the second zone 906', only the second sensor 90 running over the entire substrate 900 will sense the pressure. For this reason it can be interpreted that in case of a pressure applied within the first zone 906 it is sufficient to consider only the measured signal coming from sensor 901, normalized with a certain normalization factor because the length of the first sensor 901 is different (e.g. shorter here) than the length of the second sensor 901'. The pressure of the second zone 906' can be found while subtracting the signal of the first electrode 901 of the signal of the second electrode 901' after normalization. As an example two loads are applied on the same moment on both zones 906 and 906', depicted as LI, 1006, and L2, 1006', in Figure 10. The measured capacitance, according to one of the embodiments of this invention, for both lines are depicted in graphs 1007 and 1008. After applying the abovementioned calculations one can see that the applied pressure can be estimated for every zone.

Figure 11 shows the embodiments of Figure 7, 8 and 9 under each other. The amount of sensor zones M1-M12 is equal for all of them, but depending upon the application one of the different designs becomes more or less preferable.

Figure 12 shows the possibilities based on the embodiment of Figure 9, implementing a two- dimensional sensor grid with particular design freedom. If one wants at a certain area in its application more sensing zones this can be accomplished in the way as illustrated in Figure 12. As an example, if 10 sensor zones are requested on top of the substrate, 10 sensors need to be applied on top of the substrate and cut every 1/10 of the substrate, in order to have a uniform distribution. In case no uniform distribution is required, the sensors can be cut accordingly.

The amount of pressure zones can be chosen according to the needs of the designer as depicted in Figure 12 with this method. The way how the measured signals are related to the pressure in the different zones is depicted in Figure 13.

Two possible general production methods of this smart mattress material 140, 150 are displayed in Figure 14 and 15. Figure 14 refers to a roll-to-roll process to apply the force absorbing and force distributing article or substrate 141 to the sensor layer 142. As illustrated in Figure 14b, this can be done by means of casting the force absorbing product 143 (e.g. latex) on top of the textile provided with electrodes 144 and cure it or let it dry. Also, sheet-to-sheet or sheet-based process production is possible, for which different embodiments are shown in Figure 15. Process #1 displays a method where the sensor sheet 152 is glued on the force absorbing and force distributing article 151, wherein the glue 153 is represented as an additional layer or sheet in between. Process #2 shows a method where two force absorbing articles 151 are glued to the sensor layer 152, such that this layer is totally encapsulated. Process #3 shows an embodiment in which the sensor sheet 155 is smaller than the surrounding force absorbing articles 151 in order to let it disappear in the end product. Another advantage as shown here is that the force absorbing articles 151 are glued directly to each other which can result in adhesion advantages or in some occasions only one glue layer 155 (instead of two) wherein the sensor sheet 154 is embedded in case process #2 is needed. Process #4 is displaying a method where the sensor layer 156 has holes (by punching, perforating or by weaving processes) in order to increase the adhesion between upper and under force absorbing article 151, having the glue 157 flowing through the holes from one to the other force absorbing article 151.

Figure 16 illustrates particular production method processes of a mattress or force absorbing article according to the application (e.g. where the electronics are to be applied) and in accordance with the invention. For efficiency reasons and handling one or the other process will suit best and can hence be chosen as most appropriate. In case electronics only need to be applied just once per mattress and along the short edge of the mattress, or even along the long edge of the mattress but for instance in the occasion that only few and very thin sensor layer is applied as illustrated in Figure 16a, a roll-to-roll process is possibly the production process to be executed. Whenever long as well as short edges of the mattress need to be provided with electronics as shown in Figure 16b, a sheet-based process might be most preferable way to go. Mattresses, mattress toppers, foams (e.g. for chairs), transport belts, other rubber based belts can be named as examples of end products.

According to an embodiment, one can combine a pressure adjusting system in combination with the abovementioned sensor layer in order to make it possible to regulate the measured pressure towards a predefined profile. Several pressure adjusting systems can be combined with this sensor layer, such as for instance an adjustable bed base. In many occasions, a system with integrated air cells would be preferable. Figure 17, 18 and 19 show how such an air cell based pressure adjusting system can be built in e.g. mattresses. Next to the already described items from Figure 15, some other components needs to be added. The upper part 179 of Figure 17 is similar to the mattress design achieved with process #3 in Figure 15, wherein in between two foam layers 171, a pressure sensing layer 174 is glued, by means of a glue layer 175. Next to this upper part structure 179 of Figure 17, a lower part 178 needs to be created with air gaps 173 in order to put air pillows inside. This can be done by adding an additional glue layer 175' on the bottom of the abovementioned upper part structure 179 and adding local force absorbing material 176 in such a way that air gaps 173 are created at certain locations. The product can be finalized with again a glue layer 175" and a finishing sheet 177 made of e.g. force absorbing material.

Figure 18 and 19 show variant embodiments of Figure 17 with foam 181, 191, and glue 185, 195, and sensing layer 184, 194 in between. Again, air gaps 183 and 193 are created, but now by means of giving the force absorbent articles 188, 188', 199 close to the air gaps 183, 193 a predefined shape by means of e.g. moulding, cutting, saw processes, etc. Figure 18 shows an embodiment where the air gaps 183 are created by means of two preformed force absorbent articles 188, 188', whereas in Figure 19 the air gaps 193 are created by means of just one preformed force absorbent article 199. In both variants of Figure 18 and 19, the lower foam layer 171 of the upper structure 179 in Figure 17 is now replaced by a force absorbent article layer 188, 199 directly adjacent to the air gaps 183, 193.

It is noted that the air gaps can have different shapes. In Figure 20 four embodiments of possible air gap profile shapes 2001, 2002, 2003, 2004 are shown, combined with possible profile shapes of airbags 2005, 2006, 2007, 2008. Of course, the design of air gaps and airbags are not limited to the profile shapes mentioned, and therefore other architectures are also part of the invention. In Figure 20a a rectangular profile shaped airbag 2005 is introduced within a rectangular profile shaped air gap 2001. In Figure 20b a circular profile shaped airbag 2006 is integrated in a circular profile shaped air gap 2002. In Figure 20c two circular profile shaped airbags 2007 are integrated in a rectangular profile shaped air gap 2003. In Figure 20d two circular profile shaped airbags 2008 are integrated in a hexagonal profile shaped air gap 2004 in such a way that the circular profile air cells do not only give support to the layer on top of them but also support the structure towards the sides. Circular profile airbags can be for instance spherical, ellipsoid, or cylinder shaped.

Figure 21 shows the combination of a pressure sensing absorbent article with an integrated pressure regulating system. As an example, the sensor layer exists of three pressure sensing zones, onto which a certain force is applied respectively, resulting in a particular measured pressure 2101, 2102, 2103 respectively. Also depicted are the integrated airbags 2104, 2105 and 2106. In Figure 22 is schematically illustrated how the regulation system can work in case a uniformly distributed pressure profile is required. In the area in Figure 21 where the highest pressure 2102 is measured the air cell 2205 of Figure 22 will discharge air, whereas the area in Figure 21 where the lowest pressure 2103 is measured the air cell 2206 of Figure 22 will accumulate air. The resulting measured pressure values 2201, 2202, and 2203 after regulation are depicted in Figure 22. Furthermore, the air pressure within the airbags 2204, 2205, 2206 at regulation is shown conceptually in Figure 22. Figure 23 shows schematically an embodiment of how air can be accumulated or discharged in the airbags. In accordance with an embodiment of the invention, an active air regulating system comprises of five components: a collector 2302, air valves 2301, an air inlet 2303 (coupled to e.g. a compressor or air pump), an outlet 2304 (coupled to open air or a buffer) and the airbags 2305, 2306, 2307 themselves. If one wants to accumulate air and pressure in a certain airbag, one opens the air valve of the air inlet 2303 and the corresponding airbag and the pressure in the airbag will raise till the maximum the air inlet 2303 can deliver. On the other hand, when one needs less pressure in a certain zone, one can deflate the corresponding airbag by opening the air valve of that airbag and the air valve of the outlet 2304. The mechanism steering this on-off regulation system can be e.g. a PID or fuzzy-logic based regulation system, wherein the predefined pressure profile is the input value, and the measured pressure is the output value of the system which has to be as close as possible to the wanted predefined pressure profile.

Claims

1. A system comprising a force absorbing and force distributing article comprising a first side and a second side, and a sensor system provided onto said second side of said force absorbing and force distributing article, for monitoring absolute value pressure applied on said first side of said force absorbing and force distributing article.

2. A system according to claim 1 wherein said sensor system comprises of a textile fabric with integrated electronics.

3. A system according to claims 1 or 2, wherein said sensor system comprises of local pressure sensors interconnected with an electronic bus system.

4. A system according to claims 1 to 3, wherein said applied absolute value pressure is estimated by means of measuring capacitance.

5. A system according to claim 4, wherein said capacitance is measured by means of a microcontroller.

6. A system according to claims 3 to 5, wherein said local pressure sensors incorporate electrodes.

7. A system according to claim 6, wherein said applied absolute value pressure is measured by means of measuring capacitance of said electrodes.

8. A system according to claims 6 and 7, wherein said electrodes are in electrical connection with a measurement equipment, and wherein said electrical connection is achieved by means of crimping.

9. A system according to claims 6 to 8, wherein said electrodes are woven inside said textile fabric.

10. A system according to claims 6 to 9, where a free space is provided within said sensor system in order to make a proper interconnection between said integrated electronics and said electrodes.

11. A system according to claims 4 to 10, wherein a pressure adjusting system is applied thereon, for regulating said estimated and applied absolute value pressure to a predefined pressure.

12. A system according to claim 11, wherein said pressure adjusting system comprises air cells for regulating said pressure.

13. A monitoring method for monitoring absolute value pressure within a force absorbing and force distributing article, being part of a force absorbing and force distributing system with integrated sensor system.

14. A sensor system for monitoring absolute value pressure within a force absorbing and force distributing article.