METHOD FOR DETERMINING THE LOCATION AND POSITION OF A PERSON'S PELVIS

Abstract

A method of determining the place and location of a human pelvis, including detecting sitting pressures/contact pressures exerted on the seat, the lounger or the support by the ischial tuberosities and the coccyx of the sitting person or by the iliac crests and the pubic bone of the lying person by a surface sensor; determining, by a computer unit, a first position on the surface sensor where a first peak sitting pressure/peak contact pressure is reached; determining a second position on the surface sensor where a second peak sitting pressure/peak contact pressure is reached; determining a distance between the first position and the second position; determining a third position on the surface sensor where a third peak sitting pressure/peak contact pressure is reached, the position being between the first position and the second position; and limiting an area of the surface sensor which detects sitting and contact pressures.

Claims

1.-10. (canceled)

11. A method of determining the place and location of a pelvis of a person sitting on a seat or sitting or lying on a lounger or a support, wherein the method comprises the following operations: a) detecting sitting pressures/contact pressures exerted on the seat, the lounger or the support by the ischial tuberosities and the coccyx of the person sitting essentially upright or by the iliac crests and the pubic bone of the person lying in a prone position by a surface sensor arranged on the seat, the lounger or the support; b) determining, by a computer unit, a first position (P.sub.1) on the surface sensor at which a first peak sitting pressure/peak contact pressure exerted by a first ischial tuberosity/iliac crest of the person is reached; c) determining, by the computer unit, a second position (P.sub.2) on the surface sensor at which a second peak sitting pressure/peak contact pressure exerted by a second ischial tuberosity/iliac crest of the person is reached, the second position (P.sub.2) being within a predetermined distance range A from the first position (P.sub.1); d) determining, by the computer unit, a distance B between the first position (P.sub.1) and the second position (P.sub.2); e) determining, by the computer unit, a third position (P.sub.3) on the surface sensor at which a third peak sitting pressure/peak contact pressure exerted by the coccyx/pubic bone of the person is reached, the third position (P.sub.3) being between the first position (P.sub.1) and the second position (P.sub.2), and the third position (P.sub.3) being substantially on their common connecting line (C) or within a predetermined distance range on a line (D) running essentially perpendicularly to the connecting line (C); f) limiting, by the computer unit, an area (E) of the surface sensor which detects sitting and contact pressures; and g) evaluating, by the computer unit, the sitting and contact pressures of the pelvis in the restricted area (E) detecting sitting and contact pressures.

12. A method according to claim 11, wherein, for narrowing down the area (E) detecting sitting and contact pressures, the computer unit runs an iterative algorithm which depicts the Mandelbrot set.

13. A method according to claim 12, wherein the iteration is interrupted when a predetermined number is reached.

14. A method according to claim 13, wherein the shape and the magnitude of the restricted area (E) of the surface sensor which detects sitting and contact pressures depend on the number of iterations.

15. A method according to claim 11, wherein, for determining the first position (P.sub.1), the second position (P.sub.2) and the third position (P.sub.3), a pattern recognition of the maxima of the sitting and contact pressures is performed by the computer unit.

16. A non-transitory storage medium having stored therein instructions that are executable by one or more hardware processors to perform operations comprising prompting the computer unit to carry out the operations recited in claim 11.

17. A device for determining the place and location of a pelvis of a person sitting on a seat or sitting or lying on a lounger or a support, comprising a computer unit and a surface sensor connected to the computer unit and arranged on the seat, the lounger or the support and being operable to detect sitting and contact pressures which are exerted on the surface sensor by the pelvis, with the computer unit operable to carry out the operations of the method according to claim 11.

18. A device according to claim 17, wherein the surface sensor is an array of sensors selected from the group consisting of mechanical, electrical, pneumatic or hydraulic sensors.

19. A device according to claim 17, wherein the surface sensor is shaped in such a way that it adapts at least partially to the pelvis.

Description

[0022] The invention is now explained in further detail with reference to the drawings using non-limiting exemplary embodiments.

[0023] FIG. 1 is a block diagram which illustrates steps of a method according to claim 1 of the invention in a preferred order.

[0024] FIG. 2 shows a schematic perspective illustration of a seat with an integrated surface sensor according to claim 8 of the invention.

[0025] FIG. 3 shows a schematic illustration of a seating surface of the seat depicted in FIG. 1 in which a first position, a second position and a third position according to claim 1 of the invention are illustrated.

[0026] FIG. 4 shows an area of the surface sensor which detects sitting and contact pressures.

[0027] Hereinafter, reference is made to FIGS. 1 to 3. Referring initially to FIG. 2, a device 200 according to the invention for determining the place and location of a pelvis of a person sitting on a seat 10 or sitting or lying on a lounger or a support is shown. The lounger, the support and the person are not shown in the figures. The device 200 comprises a computer unit 20 and a surface sensor 11 connected to the computer unit 20. The surface sensor 11 is arranged on a seat element 12 and in a back element 13 of the seat 10, in particular integrated therein, wherein a leg element 14 of the seat 10 has no surface sensor 11. In a further embodiment, which is not shown, the leg element 14 can also have a surface sensor 11, in addition to the seat element 12 and the back element 13. In still further embodiments, which are also not shown, only the seat element 12 or the back element 13 can have a surface sensor 11. The above-mentioned embodiments are combinable, meaning that, for example, the leg element 14 and the seat element 12 have a surface sensor 11 and the back element 13 has no surface sensor 11. The surface sensor 11 exemplified in FIG. 2 has comparatively large-scale individual sensors, for which reason the determination of distances can be done only relatively roughly. Therefore, the surface sensors used in connection with the invention can also have far more individual sensors in a finer grid or array than what is shown in FIG. 2.

[0028] In order to achieve high sensitivity of the sensors 15, the surface sensor 11 is shaped in such a way that it adapts at least partially to the person's pelvis. As a result, the surface sensor 11, which is designed for detecting sitting and contact pressures exerted on the surface sensor 11 by the pelvis, coccyx and sacrum of the person, can detect the sitting and contact pressures with a high level of precision. As can be seen in FIG. 2, the surface sensor 11 is an array of sensors 15 selected from the group consisting of mechanical, electrical, pneumatic or hydraulic sensors. In particular, the surface sensor is a two-dimensional array of sensors 15 which completely occupies the seat element 12 and the back element 14 of the seat 10. The number of sensors 15 arranged in the array can vary and is not limited to a specific number. An array with 55 sensors 15 is illustrated in FIG. 3. As a result, the position of the sitting and contact pressures exerted by the pelvis, coccyx and sacrum of the person, and thus every position of the person's pelvis, can be determined with sufficient accuracy. The sensors 15 of the surface sensor 11 are preferably designed as flat chambers filled with a fluid, e.g., air or water. In this case, the surface sensor 11 is connected to the computer unit 20 via fluid-carrying channels, which are not shown in the figures. Electrical or mechanical sensors can also be used for detecting the sitting and contact pressures and are therefore not limited to the sensors mentioned above by way of example. Thus, the sensors 15 can also be strain gauges which can be arranged in an array. In this case, the computer unit 20 is electrically connected to the surface sensor 11.

[0029] Hereinafter, reference is made to FIGS. 1 and 3. In FIG. 1, a block diagram is shown which illustrates steps 101, 102, 103, 104, 105, 106, 107 of a method 100 according to the invention for determining the place and location of a pelvis of a person sitting on a seat 10 or sitting or lying on a lounger or a support. In a first step 101 of the method 100, sitting pressures/contact pressures exerted on the seat 10, the lounger or the support by the ischial tuberosities and the coccyx of the person sitting essentially upright or by the iliac crests and the pubic bone of the person lying in a prone position are detected by means of a surface sensor 11 arranged on the seat 10, the lounger or the support. In a next step 102, a first position P.sub.1 on the surface sensor 11 at which a first peak sitting pressure/peak contact pressure exerted by a first ischial tuberosity/iliac crest of the person is reached is determined by the computer unit 20. In FIG. 3, the first position P.sub.1 is detected by the sensor in row 2 and column 2 of the array by way of example. In a further step 103, a second position P.sub.2 on the surface sensor 11 at which a second peak sitting pressure/peak contact pressure exerted by a second ischial tuberosity/iliac crest of the person is reached is determined by the computer unit 20, the second position P.sub.2 being within a predetermined distance range A from the first position P.sub.1. In FIG. 3, the second position P.sub.2 is detected by the sensor in row 4 and column 4 of the array. The predetermined distance range A is defined by the geometric arrangement of the ischial tuberosities or, respectively, the iliac crests of the person and is 100 mm to 150 mm for the ischial tuberosities and 200 mm to 250 mm for the iliac crests in the prone position. The specified distance range A is considered as exemplary, since, in addition to gender-specific differences, other parameters such as age or pathological changes, especially in the area of the coccyx of a person, also have an influence on the geometry of the pelvis or, respectively, the sacral structure, and thus on the distance range A. In a subsequent step 104 of the method 100, a distance B between the first position P.sub.1 and the second position P.sub.2 is determined by the computer unit 20. In this case, this distance B corresponds to a true distance between the first ischial tuberosity/iliac crest and the second ischial tuberosity/iliac crest of the person, the distance B between the iliac crests being greater than between the ischial tuberosities. The term true distance is understood to refer to the actual distance between the ischial tuberosities or, respectively, the iliac crests which corresponds to the respective pelvis of the person and is detected by the surface sensor 11.

[0030] If the first position P.sub.1, the second position P.sub.2 and the distance B between said positions P.sub.1, P.sub.2 have been determined by the computer unit 20, a third position P.sub.3 on the surface sensor 11 at which a third peak sitting pressure/peak contact pressure exerted by the coccyx/pubic bone of the person is reached is subsequently determined by the computer unit 20. In this case, the third position P.sub.3 is between the first position P.sub.1 and the second position P.sub.2, the third position P.sub.3 being substantially on their common connecting line C or within a predetermined distance range, not shown, on a line D running essentially perpendicularly to the connecting line C. In FIG. 3, the third position P.sub.3 is detected by the sensor in row 3 and column 3 of the array.

[0031] After the third position P.sub.3 has been determined, a restricted area E detecting sitting and contact pressures is determined by the computer unit 20 in a next step 106, with this area being shown schematically in FIG. 3 and in the form of a Mandelbrot set 30 in FIG. 4. In order to limit the area E detecting sitting and contact pressures, the computer unit 20 executes an iterative algorithm which maps said Mandelbrot set 30.

[0032] In a final step 107 of the method 100, the sitting and contact pressures of the person's pelvis in the restricted area E detecting sitting and contact pressures are evaluated by the computer unit 20. Sitting and contact pressures outside of this range E are not evaluated any further by the computer unit 20.

[0033] In this case, the computer unit 20 of the device 100 is designed for carrying out the steps 101, 102, 103, 104, 105, 106, 107 of the above-mentioned method 200, with the order of the method 100 not being limited to the preferred order as shown in FIG. 1. For example, the steps 102, 103 of the method 100 can also take place in reverse order.

[0034] Hereinafter, reference is made to FIG. 4. FIG. 4 shows the restricted area E detecting sitting and contact pressures or, respectively, the Mandelbrot set 30 in different shapes and sizes.

[0035] Furthermore, FIG. 4 shows the sitting and contact pressures 37, 38, 39 that occur in the restricted area E detecting sitting and contact pressures and are exerted on the surface sensor 11 by the pelvis and the coccyx or sacrum, based on which the place and, in addition, also the location of the pelvis can be determined. As already mentioned, the area E detecting sitting and contact pressures is limited by the above-mentioned iterative algorithm. For the sake of illustration, a first iteration 31 of the algorithm which forms a circular area E detecting sitting and contact pressures, a second iteration 32 which forms an elliptical area E detecting sitting and contact pressures, and a third iteration 33 should be mentioned. As can be seen in FIG. 4, the area E detecting sitting and contact pressures is increasingly restricted with increasing iterations, with the area E detecting sitting and contact pressures having essentially the shape of a cardioid or, respectively, the shape of the Mandelbrot set 30 already at five iterations 34. According to the rectangular coordinate system of the pelvic structure, the sagittal axis in the range from 2 to 0 and the longitudinal axis in the range from 0 to 2 are plotted on the abscissa, and the horizontal axis of the person's pelvis is plotted on the ordinate. An origin 35, which is illustrated at a crossing point of the abscissa and the ordinate, represents a stable equilibrium position with stress on the sacral structure and is shown at a distance G from an edge 41 of the Mandelbrot set 30. The origin 35 corresponds to the centre of gravity of the weight of the person's body section and, when the surface sensor 11 is integrated, represents a horizontal dorsal position of the person or, respectively, that point is loaded with maximum contact pressure by the sacrum, provided that the longitudinal axis or, respectively, the frontal plane of the person's upper body has a parallel orientation relative to a support structure, such as, for example, a standing board not shown in the figures.

[0036] During a rolling process of the pelvis, i.e., a rotation of the pelvis around the horizontal axis, the ischial tuberosities first exert peak sitting pressures 37, 38 on the surface sensor 11, starting from an upright sitting position of the person on the surface sensor 11. In doing so, the peak sitting pressures 37, 38 are at the above-mentioned distance A from one another and arise outside of the restricted area E detecting sitting and contact pressures. If asymmetric stress is put on the ischial tuberosities, pressure differences between the peak sitting pressures 37, 38 can be detected by the surface sensor 11. Due to these pressure differences, an angle of rotation of the pelvis around the sagittal axis of the person can be determined by the computer unit 20, whereby the true length of the ischial tuberosities, in case of a prone position the true length of the iliac crests, and from this a radius of the circular area E of the first iteration 31 of the algorithm which detects sitting and contact pressures can be determined by the computer unit 20. In case of a tilt of the pelvis around the horizontal axis of essentially 10 and more, depending on the flexibility of the substructure and any pathological changes in the coccyx, the coccyx of the person exerts a sitting pressure 39 on the surface sensor 11, which is located essentially on the common connecting line C formed by the peak sitting pressures 37, 38. In this case, the sitting pressure 39 can be at a distance F from the peak sitting pressures 37, 38. In this location of the pelvis, the distance range A of the peak sitting pressures 37, 38 corresponds to half the radius of the circular area E of the first iteration 31 of the algorithm, which area detects sitting and contact pressures.

[0037] The sitting pressure exerted on the surface sensor 11 by the coccyx increases during the rolling process up to a transition 40 at which the sacrum of the person exerts a contact pressure on the surface sensor 11. In the horizontal reclining position of the person, i.e., a location of the pelvis tilted around the horizontal axis by 90, the contact pressure exerted by the sacrum reaches its maximum at the origin 35. Starting from the horizontal reclining position of the person, if said person moves to the side, i.e., laterally rolls his or her pelvis in a mixed movement or a rotation around the longitudinal axis so that a lateral position is adopted, the pelvis exerts contact pressures on the surface sensor 11. These contact pressures are illustrated in FIG. 4 by a line 36 showing a mixed sideways movement of the person by 30. If a person in a horizontal reclining position rotates by 180 in a mixed movement, the area detecting sitting and contact pressures would only detect sitting and contact pressures arising within the first 90 of that rotation, i.e., within the circular area E of the first iteration 31 which detects sitting and contact pressures. Sitting and contact pressures arising on the surface sensor 11 and going beyond this 90 rotation and thus beyond the circular area E of the first iteration 31 which detects sitting and contact pressures would not be detected by said area. To still detect such movements of the person, the computer unit 20 is designed for storing the area E detecting sitting and contact pressures. If sitting and contact pressures exerted by the pelvis arise on a peripheral region of the circular area E of the first iteration 31 which detects sitting and contact pressures, a second area detecting sitting and contact pressures, which is not shown in the figures, is depicted adjacent to the area E detecting sitting and contact pressures. In this case, the second area detecting sitting and contact pressures is a copy of the area E which detects sitting and contact pressures. This process can be repeated several times by the computer unit so that movements or, respectively, sitting and contact pressures exerted by the pelvis outside of the area E detecting sitting and contact pressures can be detected for every movement of the person.

[0038] With further lateral rolling of the pelvis in a movement around the longitudinal axis or a mixed movement, i.e., the person adopting a horizontal prone position, only the pelvic structure is stressed. The pubic bone and the iliac crests can exert maximum contact pressures on the surface sensor 11. In mathematical terms, these contact pressures correspond to the contact pressures of the person in a dorsal position, wherein the sacral structure is stressed in the dorsal position and the pelvic structure is stressed in the prone position. With a maximum load on the sacrum in a horizontal dorsal position at the origin 35 or, respectively, on the pubic bone in a horizontal prone position in an area of the transition 40, the stable equilibrium position is reached.

[0039] The distances F and G are essentially the same size, although they can differ, for example, due to a pathological change in the anatomy of the person in the area of the coccyx. If the distances F and G are unequal and other characteristic points or, respectively, pressure areas not shown in the figures are known, the distance F can be corrected by calculation and exact conclusions can still be drawn about an ergonomically correct or incorrect sitting or reclining position.

[0040] It may be mentioned that the method according to the invention provides mathematically exact results also when the sensitivity of the sensors is reduced to a very narrow range, for example for cost reasons, and consequently only no or maximum pressure values are detected by the sensor.

[0041] Furthermore, it may be mentioned that the surface sensor can also be integrated into the seating surface only directly in the contact area of the ischial tuberosities and the coccyx and sacrum. This is possible because, for the calculation method, based on an evaluable parameter, only geometric fixed points dependent therefrom are used for assessing the location of the pelvis, but they do not actually have to be physically present. This would be interesting, for example, for determining a location for pure seating systems.