Body support apparatus having automatic pressure control and related methods
View Patent ↗A body support such as a cushion, mattress, chair or the like has at least one inflatable air chamber. A pressure sensor senses interface pressures at different locations on a surface of the air chamber. Indicators derived from the interface pressures indicate the onset of a trend toward bottoming out. A controller controls air pressure within the air chamber based at least in part on values of the indicators. The controller may be implemented as a state machine.
1. A sensor apparatus for a body support surface including an inflatable air chamber, the apparatus comprising:
a plurality of pressure-sensitive taxels underlying an air chamber of a body support surface, each of the taxels providing an output indicative of a pressure exerted by the air chamber on a substrate underlying the air chamber at a location of the taxel; and
a controller: that is connected to receive the outputs of the taxels; that comprises a state machine having a plurality of defined states and a plurality of transitions defined between the states; and that derives a plurality of bottoming out indicators from the taxel outputs, each of the bottoming out indicators indicating a degree of non-uniformity in the outputs of the taxels;
wherein, for at least one of the states:
the state machine undergoes a first transition if a first number of the plurality of bottoming out indicators indicates a trend toward bottoming out; and
the state machine undergoes a second transition if a second number of the plurality of bottoming out indicators that is greater than the first number indicates a trend toward bottoming out.
2. A sensor apparatus according to claim 1 wherein the controller is configured to:
automatically monitor the air chamber until the onset of a trend toward bottoming out is detected.
3. A sensor apparatus according to claim 1 wherein the controller is configured to compute a sum of the outputs of those of the taxels having values greater than a high-pressure threshold.
4. A sensor apparatus according to claim 1 wherein the controller is configured to identify those of the taxels having values greater than a high-pressure threshold, and compute a sum of the amounts by which the outputs exceed the high-pressure threshold.
5. A sensor apparatus according to claim 1 wherein the controller is configured to determine a number of the taxels for which the outputs of the taxels have values lower than a low-pressure threshold.
6. A sensor apparatus according to claim 1 wherein the controller is configured to compute a measure of variance of values of the outputs of the taxels.
7. A sensor apparatus according to claim 1 wherein the controller derives at least three different bottoming out indicators from the taxel outputs.
8. A sensor apparatus according to claim 7 wherein the three different bottoming out indicators include a measure of variance of the outputs of the taxels.
9. A sensor apparatus according to claim 7 wherein the three different bottoming out indicators include an indicator based at least in part on a sum of the amounts by which the taxel outputs exceed a threshold.
10. A sensor apparatus according to claim 7 wherein the three different bottoming out indicators include an indicator based at least in part on an average value of the outputs for the N taxels having the greatest outputs, wherein N is an integer.
11. A sensor apparatus comprising:
a plurality of pressure-sensitive taxels distributed over a two-dimensional area to sense an interface pressure exerted by an inflatable air chamber, each of the taxels providing an output indicative of a pressure exerted by the air chamber at the location of the taxel; and,
a controller: that is connected to receive the outputs of the taxels; that comprises a state machine having a plurality of defined states and a plurality of transitions defined between the states; and that derives a plurality of bottoming out indicators from the taxel outputs, each of the bottoming out indicators indicating a degree of non-uniformity in the outputs of the taxels;
wherein for at least one of the states:
the state machine undergoes a first transition if a first number of the plurality of bottoming out indicators indicates a trend toward bottoming out; and
the state machine undergoes a second transition if a second number of the plurality of bottoming out indicators that is greater than the first number indicates a trend toward bottoming out.
12. A sensor apparatus according to claim 11 wherein the controller is configured to:
monitor the outputs of the taxels to identify the onset of a trend toward bottoming out.
13. A sensor apparatus according to claim 12 wherein monitoring the outputs of the taxels to identify the onset of a trend toward bottoming out comprises computing a sum of the outputs of those of the taxels having output values greater than a high-pressure threshold.
14. A sensor apparatus according to claim 12 wherein monitoring the outputs of the taxels to identify the onset of a trend toward bottoming out comprises, for those of the taxels having values greater than a high-pressure threshold, computing a sum of the amounts by which the outputs exceed the high-pressure threshold.
15. A sensor apparatus according to claim 12 wherein monitoring the outputs of the taxels to identify the onset of a trend toward bottoming out comprises determining a number of the taxels for which the outputs of the taxels have values lower than a low-pressure threshold.
16. A sensor apparatus according to claim 12 wherein monitoring the outputs of the taxels to identify the onset of a trend toward bottoming out comprises computing a measure of variance of values of the outputs of the taxels.
17. A sensor apparatus according to claim 11 wherein the controller derives at least three different bottoming out indicators from the taxel outputs.
18. A sensor apparatus according to claim 11 wherein the controller computes a measure of variance of the outputs of the taxels and derives a bottoming-out indicator from the measure of variance.
19. A sensor apparatus according to claim 17 wherein the three different bottoming out indicators include an indicator based at least in part on a sum of the amounts by which the taxel outputs exceed a threshold.
20. A sensor apparatus according to claim 17 wherein the three different bottoming out indicators include an indicator based at least in part on an average value of the outputs for the N taxels having the greatest outputs, wherein N is an integer.
21. A method for monitoring gas pressure within an air chamber of a body support surface, the method comprising:
monitoring interface pressures of the air chamber at a plurality of spaced-apart locations of pressure-sensitive taxels underlying an air chamber of a body support surface, each of the taxels providing an output indicative of a pressure exerted by the air chamber on a substrate underlying the air chamber at a location of the taxel; and,
deriving a plurality of bottoming out indicators from the taxel outputs, each of the bottoming out indicators indicating a degree of non-uniformity in the outputs of the taxels;
wherein a first transition is undergone if a first number of the plurality of bottoming out indicators indicates a trend toward bottoming out, the first transition being one of a plurality of transitions defined between a plurality of defined states; and
a second transition is undergone if a second number of the plurality of bottoming out indicators that is greater than the first number indicates a trend toward bottoming out, the second transition being one of the plurality of transitions.
22. A method according to claim 21 wherein monitoring for a trend toward bottoming out comprises monitoring for an increase in maximum values of the interface pressures coupled with an increase in number of the interface pressures that have values below a low-pressure threshold.
23. A method according to claim 22 wherein monitoring for an increase in maximum values of the interface pressures comprises computing a sum of those of the interface pressures having values greater than a high-pressure threshold.
24. A method according to claim 21 comprising computing a measure of variance of values of the interface pressures.