WO2005074754A1

WO2005074754A1 - Posture sensing

Info

Publication number: WO2005074754A1
Application number: PCT/GB2005/000352
Authority: WO
Inventors: John Burkitt
Original assignee: Eleksen Limited
Priority date: 2004-02-03
Filing date: 2005-02-02
Publication date: 2005-08-18
Also published as: GB0402316D0

Abstract

Posture sensing apparatus comprising a position detector for use with a seat, a data processing device configured to receive input data derived from said position detector representative of the position of a mechanical interaction with the position detector, and having access to reference data, and a feedback device configured to receive an input from said data processing device; said data processing device configured to compare input data with reference data to identify an unsatisfactory postural condition and to supply an input to said feedback device in response. The feedback device may generate a visual alert, an audio alert, a tactile alert and/or an input to a motor. An unsatisfactory postural condition may be identified on identification of a posture of low initial ergonomic value, a posture of high initial ergonomic value maintained for a predetermined period or a period of occupancy maintained for a predetermined period.

Description

Posture Sensing

Background of the Invention

1. Field of the Invention The present invention relates to monitoring mechanical interactions, in particular to monitoring mechanical interaction between an occupant of a seat and the seat in order to assess the posture of the occupant.

2. Description of the Related Art The field of ergonomics involves the study of the physical interaction between the human body and workplace equipment, in order to improve safety and efficiency in the workplace. Several designs of furniture are available that are advertised as offering good ergonomic value. However, the degree of benefit provided to the user of the furniture depends upon how the occupant actually sits in the chair during each sitting period. An unsatisfactory sitting pattern is considered to be a contributing factor in the development of some occupational/work-related disorders or injuries, for example Repetitive Strain Injury (RSI). Monitoring the sitting pattern of an occupant of a seat is therefore regarded as an important concern when formulating a preventive measure programme to reduce the incidence of such conditions. The leading elements of a sitting pattern are the ergonomic values of different postures adopted over a particular period of observation, how long each posture is maintained and the frequency and duration of rest periods from occupancy. It is to be appreciated that whilst some postures are considered to offer unsatisfactory ergonomic value when first adopted, other postures are considered to offer satisfactory ergonomic value when first adopted but that value diminishes over time. Thus, in some cases, a posture that is considered to be satisfactory at one time can become unsatisfactory if maintained for too long. Ideally, an occupant posture sensing system would provide a clear indication as to whether a postural condition is satisfactory or unsatisfactory, taking into account posture adopted, the time the posture has been maintained and the time since the last break from occupancy. However, available systems that may be used to monitor posture, for example pressure measurement systems, are arranged to provide an overly detailed output and are also prohibitively expensive.

Brief Summary of the Invention According to a first aspect of the present invention there is provided posture sensing apparatus comprising: a position detector for use with a seat, a data processing device configured to receive input data derived from said position detector representative of the position of a mechanical interaction with the position detector, and having access to reference data, and a feedback device configured to receive an input from said data processing device; said data processing device configured to compare input data with reference data to identify an unsatisfactory postural condition and to supply an input to said feedback device in response. According to a second aspect of the present invention an unsatisfactory postural condition is identified on identification of one of: a posture of low initial ergonomic value, a posture of high initial ergonomic value maintained for a predetermined period, a period of occupancy maintained for a predetermined period. According to a third aspect of the present invention said data processing device is configured to receive input data derived from said position detector representative of the magnitude of pressure of a mechanical interaction with the position detector. According to a fourth aspect of the present invention, the feedback device is configured to generate a visual alert, an audio alert, a tactile alert and/or an input to a motor.

Brief Description of the Several Views of the Drawings Figure 1 shows an individual sitting in a chair having an occupant sensing area; Figure 2 shows a position detector; Figure 3 shows the scenario of Figure 1 after an elapsed period; Figure 4 shows a visual representation of characteristics of a mechanical interaction; Figures 5 and 6 show visual representations of data derived from a

mechanical interaction; Figure 7 shows a flow chart of method steps for a posture sensing

application; Figure 8 shows a step in the flow chart of Figure 7 in further detail; Figure 9 shows a visual display of data derived from mechanical interactions plotted on a map; Figure 10 illustrates a feature of an application supporting a visual display of data derived from mechanical interactions plotted on a map; Figure 11 shows a computer generated application window displaying

different data plots on the map of Figure 8; Figure 12 illustrates a feature enabling modification of the map of Figure 9 Figure 13 shows a flow chart of method steps for a calibration routine; Figure 14 shows a plurality of occupant sensing areas connected to a network; Figure 15 illustrates an alternative use of an occupant sensing area; Figure 16 shows different arrangements of occupant sensing area; Figure 17 shows a portable occupant sensor; Figure 18 illustrates use of a posture sensing application to provide an input to a motorised element of equipment.

Written Description of the Best Mode for Carrying Out the Invention Figure 1 Figure 1 shows a chair 101, which forms part of a workstation along

with a desk 102, a personal computer 103, a monitor 104 and a keyboard

105. The workstation is available for use by person 106, shown sitting in

chair 101. Whilst in the chair, person 106 sits with a posture that feels natural and comfortable. Often, individuals sit without conscious regard to the benefit or detriment of the way they are sitting. A posture that is deemed to offer actual or potential health related benefits can be considered as a posture having a high ergonomic value, whilst a posture that is deemed to be actually or potentially detrimental to health can be considered as a posture having a low ergonomic value. In the course of everyday activity, a person may sit with a posture offering low ergonomic value, whether from the outset or after a period of time, and thus that person may unknowingly be contributing negatively to a current or potential physical complaint. In many circumstances it is desirable to monitor the sitting pattern of an individual and to use the observation to encourage the individual to consciously adopt a posture offering a relatively favourable ergonomic value. A desirable feature of an occupant posture sensing system is the provision of feedback to draw attention to postural conditions warranting corrective action. In an optimal arrangement, an individual is encouraged to incorporate different postures having a relatively high ergonomic value and frequent intervals from occupancy into their sitting pattern. In the scenario of Figure 1, person 106 is adopting a posture

considered to have a good initial ergonomic value. As will be described in further detail, chair 101 is provided with an occupant sensing area and is arranged to detect characteristics of mechanical interactions with the occupant sensing area. As will also be explained in further detail, chair 101 is utilisable in an occupant posture sensing system in which the posture of an occupant of the chair is monitored over an observation period to identify unsatisfactory postural conditions. Chair 101 has an occupant support portion 107 that provides a

support surface 108 for an occupant of the chair. The occupant support

portion 107 is provided with a position detector (not shown) configured to detect mechanical interactions therewith. The position detector provides an occupant sensing area, in Figure 1 the sensing area is the area bound by dotted line 109.

Figure 2 Figure 2 shows a position detector suitable for use with a chair in an occupant posture sensing system. Preferably, a position detector having a flexible and/or fabric construction is utilised, with the latter in particular offering the advantages of being durable and breathable. GB Patent No 2 341 929 describes a suitable detector that is configured to determine the positional co-ordinates of a mechanical interaction within a sensing area, and also to determine an additional property of the mechanical interaction, for example pressure. The contents of GB Patent No 2 341 929 are incorporated herein by reference. Thus, a position detector may be utilised that is configured to determine X-axis and Y- axis co-ordinates of a mechanical interaction within a sensing area only, or that is also configured to determine an extent of mechanical interaction in the Z-axis. Position detector 201 has two electrically conducting fabric planes,

having electrically conductive fibres therein, in the form of a first plane 202

and a second plane 203. In the no press condition of the detector 201 , the conducting planes are separated from each other, and thereby electrically insulated from each other, by means of a mesh 204 fabricated from insulating material. When force is applied to one of the outer planes, the two conducting planes are brought together, through the mesh 204, thereby creating a position at which electrical current may conduct between planes 202 and 203. It is then possible to identify the occurrence and position of a mechanical interaction with the detector 201. When a voltage is applied across terminals 207 and 208, a voltage gradient appears over plane 202. When a mechanical interaction takes place, plane 203 is brought into electrical contact with plane 202 and the actual voltage applied to plane 203 will depend upon the position of the interaction. Similarly when a voltage is applied between connectors 211 and 212, a voltage gradient will appear across plane 203 and mechanical

interaction will result in a voltage being applied to plane 202. Similarly, the

actual voltage applied to plane 202 will depend upon the actual position of the interaction. In this way, for a particular mechanical interaction, it is possible to identify locations within the plane with reference to the two aforesaid measurements. Connectors 207, 208, 211 and 212 are

connected to a control circuit 221, which is configured to apply voltage

potentials to the detector 201 and to make measurements of electrical properties in response to mechanical interactions. Control circuit 221 includes a micro-controller having read-only and

random access memory. Control circuit 221 identifies electrical

characteristics of the sensor 201, and hence mechanical interactions with the sensor, and in response data relating to the characteristics of the environment is supplied to a data processing device, such as a portable computer 231 , via a serial interface 232.

Control circuit 221 is configurable to supply data relating to the position of a mechanical interaction (XY data) and/or the extent of a mechanical interaction (Z data). Data may be supplied to a data processing device, by one or more physical connectors, such as wires and cables, or by a wireless transmission link, for example via an infra-red, bluetooth or wi-fi link. Positional XY data derived from a position detector is representative of the centre of applied pressure. Thus, when a position detector is located to act as an occupant sensing area of a seat, positional XY data derived from the detector is representative of the centre of gravity of an occupant. Extent Z data derived from a position detector is representative of the extent of pressure. Thus, when a position detector is located to act as an occupant sensing area of a seat, extent Z data derived from the detector is representative of the pressure applied by an occupant.

Figure 3 Figure 3 shows the scenario of Figure 1, following an elapsed period. By considering positional XY and extent Z data derived from the occupant sensing area of a seat with reference to the physical environment and human biomechanics, it is possible to derive a framework to identify unsatisfactory postural conditions arising during a period of occupancy of the seat. As previously described, positional XY data derived from an occupant sensing area of a seat is representative of the centre of gravity of an occupant. This data is referenced spatially to the sensing area of the position detector and in turn this sensing area can be referenced spatially to the physical structure of the seat. By observing sitting individuals it is possible to derive empirically or otherwise to derive reference data outlining a boundary between an occupant posture offering satisfactory initial ergonomic value and an occupant posture offering unsatisfactory initial ergonomic value. This reference data is then utilisable in providing feedback that is indicative of whether the benefit of a postural condition is considered to be positive or

negative. In Figure 3, person 106 is shown sitting with a posture offering

unsatisfactory initial ergonomic value. The detection of this unsatisfactory postural condition, by processing of data derived from the occupant sensing area of chair 101 , has resulted in the raising of an alert. An alert may

function to prompt the occupant of the chair 101 to take curative action, or to actively initiate curative action in the form of an automatic adjustment, for example by providing an input to a motor of a motorised element of a chair or table. An alert may comprise a visual and/or audio and/or tactile alert. The alert may originate from an integrated or separate feedback device located on or within chair 101, desk 102, computer 103, monitor 104, keyboard 105 or another location about the occupant of the chair 101 or workstation. For example, as shown, computer generated graphics 301 may be displayed on monitor 104, an audible beep 302 may be sounded from computer 103 and/or a vibration alert 303 may be propagated through chair 101.

Figure 4 A visual representation of characteristics of a mechanical interaction with an occupant sensing area is shown in Figure 4. A mechanical interaction is represented as a circle 401 with cross hairs 402 at the centre thereof. The circle 401 is plotted in a Cartesian co-ordinate system with reference to X- axis 403 and Y-axis 404. The XY co-ordinates of the intersection of cross

hairs 402 represent a position of the centre of force of the mechanical

interaction, whilst the magnitude of the radius 405 of the circle 401 represents the extent of pressure experienced under the mechanical interaction. Figures 5 and 6 illustrate visually how data derived from a mechanical interaction can be utilised in the determination of satisfactory and unsatisfactory postural conditions.

Figure 5 Figure 5 illustrates, by the use of visual mapping, how data relating to the position only of a mechanical interaction position can be utilised to distinguish between satisfactory and unsatisfactory postural conditions. At 501 , the perimeter 502 of an occupant sensing area 503 is plotted in a Cartesian co-ordinate system with reference to X-axis 504 and Y-axis

505. Within the occupant sensing area 503 is illustrated a first zone 506 to the interior of a boundary line 507 and a second zone 508 to the exterior of boundary line 507 and the interior of perimeter 502. Boundary line 507 represents a border between data corresponding to a posture that is considered to have a "high" (satisfactory or greater) initial ergonomic value and data corresponding to a posture that is considered to have a "low" (less than satisfactory) initial ergonomic value. In the example of Figure 5, boundary line 507 delineates a circle located substantially centrally of occupant sensing area 503. Inner first zone

506 is representative of postures of high initial ergonomic value whilst outer

second zone 508 is representative of postures of low initial ergonomic value.

It is to be appreciated that the shape of a boundary line may vary between different applications and according to the sophistication of the data processing utilised. In addition, the number of different zones defined by boundary lines may also vary between different applications and according to the sophistication of the data processing utilised. At 509, input data derived from a mechanical interaction with occupant

sensing area 503 is plotted superimposed onto the map of 501, with a

mechanical interaction represented as a circle 510 with cross hairs 511 at the

centre thereof. It can be seen that the cross hairs 511 fall within the first zone

506, and hence this data plot is deemed to indicate an occupant posture of high initial ergonomic value. At 512, input data derived from a second different mechanical interaction with occupant sensing area 503 is plotted superimposed onto the

map of 501. The cross hairs 511 at the centre of circle 510 fall within the second zone 508, and hence this data plot is deemed to indicate an occupant posture of low initial ergonomic value. It can be seen that the circumference of circle 510 extends over boundary line 507 into the first zone

506.

In some applications, it is preferable for the orientation of the visual map to reflect the orientation of the occupant sensing area being observed, and for the dimensions of the visual map to be to scale of those of the occupant sensing area. If the former is implemented and the orientation of the map of the occupant sensing area 503 is known, the position of the cross

hairs 511 relative to boundary line 507 provides an indication as to which way the occupant could move to achieve a posture of high ergonomic value. For example, by identifying X-axis 504 as corresponding to the back of a seat, it

can be seen from plot 512 that the position of the centre of force applied to

the occupant sensing area 503 is towards the front of the occupant sensing

area 503. The circle 510 around the cross hairs 511 aids visual identification of the position of the centre of gravity of the occupant relative to the first zone 506 of the map 501.

At plot 513, input data derived from a third different mechanical interaction with occupant sensing area 503 is plotted superimposed onto the map of 501. It can be seen that the cross hairs 511 fall within the second zone 508, indicating an occupant posture of low initial ergonomic value. It can be seen that the cross hairs 511 plot to the front left corner of the occupant sensing area 503. Assuming that the occupant sensing area is located wholly beneath the occupant, the data plotted at 513 may be indicative of the occupant leaning over to pick an object up from the floor. To prevent such a brief movement leading to identification of an unsatisfactory postural condition, a time delay function may be incorporated into the data processing of data derived from the position detector. A time delay function may require that data that would otherwise lead to identification of an unsatisfactory postural condition be received over a predetermined period before an unsatisfactory postural condition is recognised. It is to be appreciated that an occupant sensing area may extend across all or part of a seat, and that if the occupant sensing area extend across only part of the sitting surface of the seat then the occupant sensing area may not be central to sitting surface. It is considered that the primary practical position to locate an occupant sensing area is where the flesh under the bony protuberances of the pelvis of an occupant will press against the seat. It is found that the size of the pelvic bones of different individuals varies relatively insignificantly in adults regardless of the weight of an individual, and that an occupant sensing area of dimensions 270mm by 270mm will be suitable in many practical applications. In practice, the optimum position for the occupant sensing area of a seat is dependent upon the physical shape of the seat, taking into consideration whether the seat has a backrest and/or arm rests, and the physical shape of an individual occupant. It is hence to be appreciated that the location and shape of a boundary line within a visual map may also vary depending on the position of the occupant sensing area relative to the physical structure of the seat and the physical characteristics of the occupant. Figure 6 Figure 6 illustrates, by the use of visual mapping, how the input data relating to pressure only of a mechanical interaction can be utilised to distinguish between satisfactory and unsatisfactory postural conditions. At 601 , the perimeter 602 of an occupant sensing area 563 is plotted

in a Cartesian co-ordinate system with reference to X-axis 604 and Y-axis 605. Within the occupant sensing area 603 is visually illustrated cross hairs

606 within a boundary line 607. In this example, boundary line 607 delineates

a circle with the cross hairs 606 at the centre.

At 601 , cross hairs 606 are located at the centre of the occupant

sensing area 603, and the boundary line 607 is indicative of a magnitude of

pressure under a mechanical interaction. Thus, boundary line 607 is representative of a pressure threshold. At 608, input data derived from a mechanical interaction with occupant sensing area 603 is plotted superimposed onto the map of 601, with the mechanical interaction represented as a circle 609 with cross hairs 610 at the centre thereof. It can be seen that the cross hairs 610 are plotted directly onto cross hairs 606 with the circumference of circle 609 falling inside the circumference of circle 607. This data plot is deemed to indicate that the magnitude of pressure applied to the occupant sensing area 603 by the occupant is less than the magnitude of pressure visually indicated by boundary line 607.

At 611, input data derived from a second different mechanical

interaction with occupant sensing area 603 and an occupant is plotted

superimposed onto the map of 601. It can be seen that the cross hairs 610

are plotted directly onto cross hairs 606 with the circumference of circle 609

falling outside the circumference of circle 607. This data plot is deemed to indicate that the magnitude of pressure applied to the occupant sensing area

603 by the occupant is greater than the magnitude of pressure visually

indicated by boundary line 607. A pressure threshold may be used to detect whether the occupant sensing area is taking all the body weight of the occupant or whether the occupant is resting their legs and/or arms on an alternative support surface. A pressure threshold may also be used to detect a mechanical interaction that may damage the occupant sensing area. As previously described, the location and shape of a boundary line between postures of low and high initial ergonomic value within a visual map may vary depending on the position of the occupant sensing area relative to the physical structure of the seat and the physical characteristics of the occupant. As will be described in further detail, a boundary line between postures of low and high initial ergonomic value may be derived from factory settings, in the form of default settings that are optionally adjustable, or from a calibration routine performed for a particular individual occupying a particular seat. Thus, in practice, the boundary line between postures of low and high initial ergonomic value may vary for different individuals using the

same seat. At 612, a map is shown that has an elliptical boundary line 613 within

an occupant sensing area 614. Boundary line 613 represents a border

between an interior zone 615 corresponding to postures having high initial

ergonomic value and an exterior zone 616 corresponding to postures having

low initial ergonomic value, hence the map at 612 is similar to map 501. Considering an example with a seat having a back rest, the centre of gravity of an occupant sitting upon an occupant sensing area will vary according to the distance between the back rest and the pelvis of the occupant. Thus, input data relating to the pressure exerted on an occupant sensing area may be used to adjust the position of the boundary line 613 in the Y-axis within the

occupant sensing area 614 of the map at 612 to reflect reality, as indicated by arrow 617.

Figure 7 Figure 7 shows a flow chart 701, illustrating data processing instructions for a posture sensing application. In this example, an input is provided to a feedback device only in response to identification of an unsatisfactory postural condition. In other applications or modes of operation, an input is provided to the feedback device after each comparison to identify an unsatisfactory postural condition, or in accordance with other rules, and an alert is raised only in response to identification of an unsatisfactory postural condition.

At step 702, a session clock is started, in this example from zero. The session clock increments up a predetermined number of times, either based on real time or times a particular event occurs. The session clock serves to provide notification of the end of a period of observation. At step 703, reference data is implemented. In this example, the reference data outlines a single threshold between data representing postures having a high initial ergonomic value and postures having a low initial ergonomic value. In addition, the reference data provides any predetermined or other values utilised at step 705. In this example, at step

703, an occupancy clock is set to zero. The purpose of the occupancy clock will be described in further detail with reference to Figure 8.

At step 704, input data derived from a mechanical interaction with an occupant sensing area is received. At step 705 a comparison is made between the input data received and the reference data implemented at step 702. A question is asked as to whether the result of the data comparison is such that an unsatisfactory postural condition is identified. If the question asked at step 705 is answered in the affirmative, an input is provided to a feedback device at step 706, and then step 707 is entered. If the question asked at step 705 is answered in the negative, step 707 is entered directly. This step is described in further detail with reference to Figure 8. At step 707 a question is then asked as to whether the session clock has incremented to a value less than the maximum value for the present

running session. If the question asked at step 707 is answered in the

affirmative, step 708 is entered. If the question asked at step 707 is answered in the negative, this indicates that the present session has expired. At step 708, a question is then asked as to whether new reference

data is to be implemented. If the question asked at step 706 is answered in

the affirmative, control returns to step 703. If the question asked at step 706

is answered in the negative, control returns to step 704.

Figure 8 Step 705 of Figure 7 is illustrated in further detail in Figure 8.

At step 801, a question is asked as to whether the input data received at step 704 indicates a posture of high initial ergonomic value. If

the question asked at step 801 is answered in the negative, step 802 is entered. If the question asked at step 801 is answered in the affirmative, step

803 is entered. At step 802, a question is asked as to whether the input data received at step 704 indicates a posture of low initial ergonomic value. If the question asked at step 802 is answered in the negative, in this example indicating there the occupant sensing area is not being occupied, step 804 is entered. At step 804, the occupancy clock is set to zero and control returns to step 707. If the question asked at step 802 is answered in the affirmative, control returns to step 706.

The occupancy clock increments up a predetermined number of times, either based on real time whilst a posture of high initial ergonomic value is maintained or times a particular event occurs. The occupancy clock serves to provide notification of the end of a period of sitting with a posture of high initial ergonomic value. At step 803, a question is asked as to whether the occupancy clock

is set to zero. If the question asked at step 802 is answered in the affirmative, in this example indicating that a new period of occupancy is starting, step 805 is entered. At step 805, the occupancy clock is started, and

control returns to step 707. If the question asked at step 803 is answered in the negative, in this example indicating that a posture of high initial ergonomic value is being maintained, step 806 is entered. At step 806, a question is asked as to whether the occupancy clock has incremented to a value less than the maximum value for the present occupancy session. If the question asked at step 806 is answered in the affirmative negative, control returns to step 707. If the question asked at step 707 is answered in the negative, this indicates that the maximum period with which the occupant can sit continuously with the input data indicating postures of high initial ergonomic value has been reached or exceeded. Step 807 is then entered, and at this step the occupancy clock is set to zero and control returns to step 706.

Thus, an input is provided to the feedback device, at step 706, if either a posture of low initial ergonomic value is determined or it is determined that an occupant has been sitting with a posture of high initial ergonomic value over a predetermined period. The latter is implemented since, as previously described, the ergonomic value of a posture can diminish over time and hence the ergonomic value of a posture can deteriorate from a high initial ergonomic value to a low ergonomic value.

Figure 9 Figure 9 illustrates a visual display of information gathered from monitoring mechanical interaction between an occupant sensing area and an occupant. At 901, the perimeter 902 of an occupant sensing area 903 is displayed. Within the occupant sensing area 903 is visually illustrated a first

"Green" zone 904 to the interior of boundary line 905, a second "Amber" zone 906 between the exterior of boundary line 905 and the interior of boundary line 907, and a third "Red" zone 908 between the exterior of boundary line 907 and the interior of perimeter 902. In this example, boundary lines 905 and 907 delineate concentric circles located substantially centrally of the occupant sensing area 903. The first "Green" zone 904 indicates plotted data corresponding to a posture having a greater than satisfactory initial satisfactory ergonomic value. The third "Red" zone 908 indicates plotted data corresponding to a posture having unsatisfactory initial satisfactory ergonomic value. The second "Amber" zone 906 indicates plotted data corresponding to a posture having a satisfactory initial ergonomic value. At 901, two indicators of information derived from monitoring

mechanical interaction with the occupant sensing area are displayed. Firstly, the last data regarding the actual detected position of the centre of force of the mechanical interaction is represented by an object indicating a point, in this example cross hairs 909. As this data is updated, the position of the

cross hairs 909 will correspondingly be updated. Secondly, rolling average data regarding the actual detected position of the centre of force of the mechanical interaction is represented by an object indicating a region, in this example circle 910. The rolling average data may be derived from the addition together of the last X number of logged readings and dividing by X. According to the requirements of a practical application, either or both of these moving objects may be displayed. An intentional time delay may be introduced between readings from the occupant sensing area of a seat, for example, in order to accommodate available data processing resources or to prevent rapid or extreme movements from triggering an alert routine. For example, referring to Figure 5, the plot at 513 may correspond to a posture that the occupant is adopting in motion and that the occupant would not normally sustain. According to the required sensitivity of the posture sensing system, input data indicating a centre of gravity outside of the calibrated outline may need to be consecutively received a predetermined number of times or over a predetermined period, for an unsatisfactory posture condition leading to an alert to be derived. In this way, unwanted triggering of an alert routine may be avoided.

Figure 10 Figure 10 shows the map at 901 of Figure 9. As previously described,

a posture may offer high initial ergonomic value but when the posture is maintained over a prolonged period, the ergonomic value may deteriorate over time into an unsatisfactory postural condition. Figure 10 shows a first clock 1001 associated with the first "Green"

zone 904, a second clock 1002 associated with the second "Amber" zone 906 and a third clock 1003 associated with the third "Red" zone 908. The

clocks 1001, 1002, 1003 illustrate that a timer may be used to time how long data has been plotting consecutively in a particular zone. As shown, the clocks 1001, 1002, 1003 each show a different maximum period, with clock

1001 showing the greatest length of time, clock 1003 showing the shortest length of time and clock 1002 showing an intermediate length of time. Thus, identification of a posture of unsatisfactory initial ergonomic value will trigger an input to a feedback device much sooner than identification of a posture of satisfactory initial ergonomic value. For example, data plotting into the third "Red" zone 908 may trigger a feedback device input almost instantly, data plotting into the second "Amber" zone 906 may trigger a feedback device input after one hour, and data plotting into the first "Green" zone 904 may trigger a feedback device input after three hours. It is also to be appreciated that a feedback device input trigger may be modified according to previous observation during an observation period. For example, a short period of data plotting into a different zone may be tolerated within a maximum period associated with a particular zone.

Figure 11

As illustrated in Figure 11, the visual display at 901 may be presented

in an application window 1101 on a visual display unit 1102. It is to be appreciated that in practice an application window may be dimensioned much smaller relative to a visual display unit than the example illustrated in

Figure 11. According to one mode of operation of a posture sensing application, triggering of a feedback device input is based on the plotting of data object

910 only. In other applications or modes of operation, triggering of a feedback device input is based on the plotting of data object 909 only or from a combination of processing the plotting of both data objects 909, 910. For the purposes of describing the features illustrated in Figure 11, it will be assumed that triggering of a feedback device input is based on the plotting of data object 910.

According to one mode of operation, whilst data object 910 plots within the first "Green" zone 904, no alert routine is triggered. When data object 910 plots within the second "Amber" zone 806 a first alert routine is

triggered. When data object 910 plots within the third "Red" zone 808, a

second alert routine is triggered, which is intended to present a greater distraction to the occupant than the first alert routine. Depending on the particular application, an alert routine may be triggered when data object 910 first plots into a zone or when data object 910 plots into the same zone a consecutive number of times. According to a second mode of operation, each of the three zones 904, 906, 908 has an associated time delay between alert conditions, which

in some applications is variable. For example, whilst data object 910 plots within the first "Green" zone

904, no alert routine is triggered until a time limit is exceeded, when a first alert routine is then performed. When data object 910 plots within the second

"Amber" zone 806 a first alert routine is performed and after a time limit is exceeded, a second alert routine is performed. When data object 910 plots within the third "Red" zone 808, a second alert routine is performed. It is to be appreciated that different alert routines may be performed to present alerts of different ability to distract an occupant. A distracting alert serves to make an occupant aware that action is needed to achieve a satisfactory postural condition. For example, at 1103, data object 910 plots within the first "Green" zone 904. Mo alert routine is being performed and floating application window 1101 may be minimised and represented by an icon on a toolbar 1104. At 1105, data object 910 plots within the second "Amber" zone 806

and triggers a first alert routine. The first alert may comprise the application window 1101 flashing between different colours. If the application window

1101 is minimised when the first alert routine is triggered, the alert routine

may maximise the application window 1101 to bring it to the attention of the

occupant. Thus, the individual is faced directly with a notice to spur them to take action to remedy their undesirable posture. In addition to or alternatively, the first alert may comprise an icon or toolbar in which the icon is displayed flashing between different colours. At 1106, data object 910 plots within the third "Red" zone 808 and triggers a second alert routine. The second alert may comprise a different or additional type of alert to the first alert. For example, if the first alert is a visual alert, the second alert may comprise an audio alert or an input to a motor instead of or in addition to a visual alert. Boundary lines 905 and 907 between the "Green", "Amber" and "Red"

zones 904, 906 and 908 respectively are set by reference data stored and referred to by the application supporting the visual display of application window 1101. Input data from the occupant sensing area of a posture sensing seat is received and compared to the reference data to determine whether a threshold has been exceeded and consequently a different zone of the visual display 901 entered. It is also to be appreciated that a visual display application may incorporate other types of graphical representation, for example cartoon rendering a figure to show different postures linked to different data plots. For example, if data derived from an occupant sensing area is considered to correspond to a slouching position, a visual representation of this may be displayed along with a suggested posture. A moving image may be displayed, for example showing a transition between two postures, either as part of an alert routine or on request by the occupant.

Figure 12

As shown in Figure 12, an application window 1201 may feature all

the visual aspects of application window 1101 , and in addition an

adjustable slide toggle display 1202. The adjustable toggle 1203 enables a user to make adjustments, within predetermined limits, to reference data stored and referred to by the application running behind the visual display of application window 1101. As described, the reference data is utilised in determining whether to raise an alert and, if so, which alert to raise. Adjusting the visual position of toggle 1203 along the bar adjustable slide toggle display 1202 in effect adjusts the tolerances between "Green" zone 904, "Amber" zone 906 and "Red" zone 908 as defined by reference data. Tolerance adjustments may be displayed visually by resizing or reshaping of the zone areas. At 1204, toggle 1203 is shown in a position corresponding to a setting of reduced sensitivity to an occupant posture of low initial ergonomic value. As shown, the effect of this is that the area of the "Green" zone 904 has been resized to cover a greater area inside the "Amber" zone 906,

whilst the area of the "Red" zone 908 is maintained the same as at 901.

At 1205, toggle 1203 has been moved to effect a setting of

increased sensitivity to an occupant posture of low ergonomic value. As shown, the effect of this is that the area of the "Green" zone 904 has been

resized to cover a smaller area inside the "Amber" zone 906, whilst the area

of the "Red" zone 908 is maintained the same as at 901. It is to be appreciated that according to the specific application of a posture sensing system, the relative areas of more than two zones and the shape of the boundary between zones may be revised. As an alternative to a slide toggle or other visual representation, the application window may be provided with a data input box to enable a user to input a specific numeric threshold value or alphanumeric identifier assigned to a graded level of sensitivity of the system. The provision of a feature enabling the sensitivity of the occupant sensing area to be adjusted is useful for accommodating different applications, different occupants of the same seat and different seat surfaces. The latter is of particular significance if the occupant sensing area of a chair is provided as retrofit equipment, however, if the occupant sensing area is manufactured into a seat this feature is useful if an occupant is required to use a cushion on the seat surface. In addition, adjustable settings provide a means for proactively training or rehabilitating an individual to adopt postures of beneficial ergonomic value whilst sitting. Thus, reference data outlining the boundaries of ranges of data

corresponding to postures having different associated ergonomic values may

be provided in the form of absolute factory settings or in the form of

adjustable factory settings. In addition, an application may be configured to

store calibrated settings for one or more individual users.

Figure 13 The provision of a calibration routine is useful to users that have specific requirements that are not satisfactorily accommodated for by default factory settings of an occupant sensing area, for example, a user having a physical injury or disability that has specific postural requirements. Thus, for example, an asymmetrical arrangement of occupant sensing area(s) may be utilised in some applications. An alternative use of a calibration routine would be in the proactive training of an individual whereby the routine is used to progressively modify the parameter settings for reference data representing postures of satisfactory and unsatisfactory initial ergonomic values, to control feedback. Figure 13 shows a flow chart 1301 , illustrating steps in a calibration routine. At step 1302, an occupant of the seat on which calibration is being

performed is prompted to adopt a first position. This step may comprise audio and visual instructions provided for example by another individual, an electronic device, a graphical representation on paper or computer generated graphics. For example, occupant 1311 of seat 1312 may be prompted to adopt a sitting position equivalent to a sitting position shown on

a visual display 1313.

At step 1303, it is confirmed that the occupant is adopting a sitting position. A calibration application may either wait to receive an input to the effect that the calibration routine is to continue or the calibration application may wait to receive data from the occupant sensing area with which calibration is being performed before continuing to the next step of the calibration routine. For example, occupant 1311 of seat 1312 may provide confirmation that they are sitting in a position for which calibration data is to be logged by pressing an input button 1314 on a hand held device or keyboard. On entering the next step, step 1304, data logging is performed for the position being adopted by the occupant. Data derived from the occupant sensing area is received and logged. An individual data sample may comprise data relating to position and/or pressure. Data logging may comprise logging sample data over a set period of time, logging a set quantity of sample data or logging sample data until instructions to terminate this process are received. Thus, the particular style of data logging will influence the duration that an individual is required to maintain a position during this step. At step 1305, it is confirmed that data logging at step 1304 has terminated. If data logging at step 1304 is continued until an input to the effect that it is to stop is received, step 1305 may comprise confirmation of expiry of a time period. This step may comprise audio and visual confirmation that data logging is complete, and that the occupant may cease to maintain a particular sitting position, provided for example by another individual, an electronic device, or computer generated graphics.

At step 1306, a question is asked as to whether data logging is to be

performed for another occupant position. If the question asked at step 1306

is answered in the affirmative step 1302 is entered. If the question asked at

step 1306 is answered in the negative, indicating that the calibration routine

is complete, step 1307 is entered. At this step each set of data logged at step

1304 during the calibration routine is stored as reference data. Again, confirmation that this step has been completed may be provided in an audio or visual form. Thus, a calibration routine may incorporate different visual and audio prompts and/or feedback and levels of interactivity with an electronic or software application. A calibration routine may prompt an occupant to adopt a number of extreme limit positions, for example leaning severely forwards, backwards, to the left and to the right, and may prompt an occupant to adopt the same position more than once. A calibration routine provides more accurate and empirically derived data for use in identifying whether the occupant is adopting a posture of a particular initial ergonomic value at a particular time. According to one application of the described posture sensing system, a plurality of different personal settings can be stored and recalled again. A plurality of different personal settings for the same individual may be, stored and/or personal settings for a plurality of different individuals may be stored. The personal settings may be implemented in an absolute form, i.e. the calibration routine is performed again to change the settings, or an adjustable form, for example where the tolerances may be changed by the user within a predetermined extent. In a working environment where a workstation is available for use by different individuals, the personal setting for an individual may be linked to network log in settings for that individual. The personal settings for an individual may then be implemented on confirmation that the individual has logged onto the network successfully.

Figure 14

Figure 14 shows a plurality of occupant sensing areas 1401 to 1403 connected via a network 1404, for example a local area network (LAN) or wide area network (WAN) to a data store 1405 supporting a posture sensing database 1406. In this scenario, input data derived from mechanical interaction with an occupant sensing area may be logged and recorded over a period of time. Data logging may be performed continuously ^• over an observation period, regardless of the postural condition identified, and whether or not real time feedback is also provided to an occupant. A posture sensing database may be used to analyse the movements of an occupant during an observation period to: provide an alert to a third party when an occupant is adopting a posture of undesirable initial ergonomic value, to analyse how an occupant has responded to an alert routine, to identify trends in the movements of the occupant over time. In addition, a posture sensing database may be useful in identifying whether any occupational health assistance or medical examination may be required for one or more individuals, whether in advance of a particular health condition occurring or in response to identification of a health concern. The data stored in a posture sensing database may be continually updated, or may be updated less frequently by the retrieval of a set of data logged and recorded in a memory store provided for one or more occupant sensing areas. Logging and collating of data may be used to identify periods of insufficient movement and, for example, to raise an occupant alert when an occupant is detected as having occupied a seat for too long without having taken sufficient desired or mandatory intervals of vacancy. Such periods of vacancy may promote good health and alertness levels. Thus, during posture sensing, no feedback or different levels or types of feedback may be provided to an occupant. In addition, a posture sensing system may offer different degrees and types of interactivity to an occupant.

Figure 15 A posture sensing system may prompt an occupant to play a game or engage in an activity that uses an occupant sensing area as a controller.

Encouraging an occupant to undertake a period of exercise is considered to be beneficial to the general wellbeing of an individual, including circulation and skin and muscle tone. If an occupant perceives the activity as fun, this also acts as an incentive to promote health. In one application, the posture sensing system incorporates a clock to time periods of occupancy and to periodically prompt the occupant to engage in a recreational activity. In Figure 15, occupant 1501 is shown interacting with a computer

generated flight simulator application display on monitor 1502. Occupant 1501 is controlling the motion of aircraft 1503 relative to a computer generated background by moving about on occupant sensing area 1504 of chair 1505. For example, leaning from a left leaning position to a right leaning position may change the direction in which the aircraft 1503 is shown flying, and leaning from a forward leaning position to a backward leaning position may change the height at which the aircraft 1503 is shown flying. Different activities may be presented randomly or in accordance with rules. For example, activities may be correlated to different aspects of an observed sitting pattern, for example to reward an occupant for reacting quickly to alerts raised.

Figure 16 Figure 16 shows a chair 1601 having a first occupant sensing area

1602 on the seat part 1603 and a second occupant sensing area 1604 on

the back rest part 1605.

Figure 16 shows data plot 512 of Figure 5, from which it can be

derived that the centre of gravity of the occupant of the seat is towards the front of the occupant sensing area, and outside of the zone indicating a posture of high initial ergonomic value. It is found in practise that this data plot may be derived from either an occupant posture as illustrated at 1606

or an occupant posture as illustrated at 1607. At 1606, occupant 1608 is

sitting on seat 1609 in a reclining fashion, with their pelvis positioned in the

front half of the seat. At 1607, occupant 1608 is sitting on seat 1609 in a forward leaning fashion with their legs tucked underneath the chair and pressing against the front of the seat. The second occupant sensing area 1604 is utilised to distinguish between the two postural conditions, shown at 1606 and 1 607. The occupant posture at 1606 is such that the occupant 1608 is leaning against the second occupant sensing area 1604, whereas the occupant posture at 1607 is such that the occupant 1608 is not contacting the occupant sensing area 1604. According to one mode of operation of posture sensing system, data processing is performed only for data derived from the first occupant sensing area 1602 whilst the data is determined to represent a posture of satisfactory

initial ergonomic value. When data derived from the first occupant sensing area 1602 is determined to represent a posture of unsatisfactory initial ergonomic value, data processing is alternatively or additionally performed for data derived from the second occupant sensing area 1604. Alternatively,

data processing may be performed for both occupant sensing areas 1602,

1604 at all times. A plurality of occupant sensing areas of a chair may be provided as electrically separate sensing areas, as utilised by chair 1601 , or may be

provided by a single sensing area, as utilised by chair 1611.

Chair 1611 has a first occupant sensing area 1612 that extends along the seat part 1613 and up along the back rest part 1614. In addition, a second occupant sensing area 1615 is provided on right arm rest 1616 and a third occupant sensing area 1617 is provided on left arm rest 1418. An occupant sensing area 1612 may comprise a position detector having a single continuous sensing area. Alternatively, the occupant sensing area 1612 may comprise a position detector having a continuous surface area, but having a plurality of sensing regions. A sensor having a plurality of multiplexed sensing regions is disclosed in International Patent Publication No WO 01/75924. The contents of International Patent Publication No WO 01/75924 are incorporated herein by reference. The sensing regions of this type of position detector may take the form of rows only, columns only, intersections of rows and columns only or a combination of these. Providing a chair with multiple occupant sensing areas provides for more sophisticated analysis of the posture of an occupant of the chair.

Figure 17 Figure 17 illustrates components of a portable posture sensing system. Position detector 1701 is electrically connected to a control circuit 1702, which is configured to identify electrical characteristics of the detector 1701. Control circuit 1702 is configured to identify the position of a

mechanical interaction with detector 1701 and is configurable to also supply data relating to the extent of a mechanical interaction. Data derived from detector 1701 may be processed by the control circuit to identify a posture of unsatisfactory initial ergonomic value, and according to the application to raise an alert on an alert device 1703, such as a device having a light source, accompanying the portable sensor. Alternatively, data derived from detector 1701 may be supplied to an external processing device, such as portable computer 1704. A computer readable medium 1705 having software application instructions, for example to support a computer generated display, a calibration routine, data logging and/or a computer generated alert, may also accompany the portable detector. It is to be appreciated that a posture sensing system may be used to monitor postures adopted in positions other than sitting positions, for example standing or lying positions. In the example shown in Figure 17, a second position detector 1706

is electrically connected to detector 1701. Second detector 1706 is of the

type described in International Patent Publication No WO 01/75924, having

a plurality of sensing regions arranged in rows 1707. In this example,

detector 1701 and second detector 1705 are permanently connected. However, a detector may be configured to be connected and disconnected to another detector. This feature enables convenient adaptation of the arrangement of occupant sensing areas of a posture sensing system. For example, third detector 1708, having a plurality of sensing regions arranged in columns 1709, is provided with a releasable electrical connector 1710. Preferably, a third detector 1708 is provided with a connection cable 1711 that is long enough for the detector to be oriented with the columns 1509 effectively acting as rows. A bag 1712, preferably having carrying handles, may be provided to facilitate transport of a portable detector or portable sensing system. Thus, a posture sensing system may comprise: a seat having one or more occupant sensing areas manufactured therein, a portable detector for overlaying a seat in combination with a separate data processing system, a completely self contained stand alone arrangement, which may be manually portable, or a combination of these.

Figure 18 A posture sensing system as described may provide an occupant with substantially real time feedback regarding the current postural condition. As previously described, feedback may comprise an input to a motor. Figure 18 shows a workstation scenario substantially similar to that of

Figure 1 however, in Figure 18, chair 1801 and desk 1802, both of which are

adjustable in height, replace chair 101 and desk 102. In this example, each

leg of chair 1801 and desk 1802 is provided with a motorised mechanism, such as mechanism 1803 or desk leg 1804, which when operated adjust the distance between parts of the leg either side of the mechanism. The motorised mechanisms may be arranged to receive an input derived from data processing of data derived from occupant portion 1805 of chair 1801. Thus, the height of the chair 1801 and or the height of the desk 1802 may be adjusted to facilitate the occupant 106 in adopting a posture of high initial ergonomic value. Adjustments may be automatically performed or required to be performed in direct response to detection of a posture of low initial ergonomic value. According to the application, one or more elements of a chair, for example back rest 1805 of chair 1801, may be moved to present different relative arrangements and angles between different parts of the chair. Thus, one or motorised elements of equipment in the immediate environment of an observed occupant may be operated to alter relative physical relationships that ergonomically influence how an individual holds themselves.

Claims

1. Posture sensing apparatus comprising: a position detector for use with a seat, a data processing device configured to receive input data derived from said position detector representative of the position of a mechanical interaction with the position detector, and having access to reference data, and a feedback device configured to receive an input from said data processing device; said data processing device configured to compare input data with reference data to identify an unsatisfactory postural condition and to supply an input to said feedback device in response.

2. Posture sensing apparatus as claimed in claim 1 wherein an unsatisfactory postural condition is identified on identification of one of: a posture of low initial ergonomic value, a posture of high initial ergonomic value maintained for a predetermined period, a period of occupancy maintained for a predetermined period.

3. Posture sensing apparatus as claimed in any preceding claim, wherein said data processing device is configured to receive input data derived from said position detector representative of the magnitude of pressure of a mechanical interaction with the position detector.

4. Posture sensing apparatus as claimed in any preceding claim,

wherein said feedback device is configured to generate at least one of: a visual alert, an audio alert, a tactile alert and an input to a motor.

5. Posture sensing apparatus as claimed in any preceding claim, comprising a seat and wherein the position detector is incorporated with the seat during manufacture of the seat.

6. Posture sensing apparatus as claimed in any preceding claim, comprising a seat and wherein the position detector is separable from the seat.

7. Posture sensing apparatus as claimed in any preceding claim, wherein reference data is derived from a calibration routine during which input data derived from the position detector during mechanical interaction with an occupant is processed by said data processing device and stored as reference data.

8. Posture sensing apparatus as claimed in any preceding claim, wherein reference data is adjustable within a predetermined extent, to modify when an unsatisfactory postural condition is identified.

9. Posture sensing apparatus as claimed in any preceding claim, wherein said position detector is a flexible and/or fabric detector.

10. Posture sensing apparatus as claimed in any preceding claim, wherein said processing device is a personal computer.

11. Posture sensing apparatus as claimed in any preceding claim,

wherein input signals are communicated to the data processing device via a wireless link.

12. Posture sensing apparatus as claimed in any preceding claim, wherein input signals are communicated to the feedback device via a wireless link.

13. Posture sensing apparatus as claimed in claim 5, wherein the seat is provided with a plurality of occupant sensing areas.

14. Posture sensing apparatus as claimed in any one of claims 5, 6 or 13, wherein the seat has at least one motorised element and the feedback device is configured to provide an input to a motor of a motorised element.

15. Posture sensing apparatus comprising: a position detector for use with a seat, a data processing device configured to receive input data derived from said position detector representative of the position of a mechanical interaction with the position detector, and having access to reference data, and a feedback device configured to receive an input from said data processing device; said data processing device configured to compare input data with reference data to identify an unsatisfactory postural condition and to supply an input to said feedback device in response, substantially as described herein with reference to and as shown in accompanying Figures 1 to 18.