METHOD AND SYSTEM FOR ESTIMATING AN AREA OF OCCUPIED FLOOR SPACE

Abstract: A method for estimating an amount of occupied area of floor space within a predetermined floor area, comprising the steps of dividing the predetermined floor area into a grid of sensing points and determining a pressure profile of occupied sensing points corresponding to those sensing points which are in effective contact with one or more objects placed on the floor area. This allows an estimated fraction of the total number of sensing points which are occupied to be determined which may be multiplied by the total floor area in order to estimate the amount of occupied and free area. Transient effects owing to movement over the floor area may be suppressed by storing successive pressure profiles at increments of time and then relating only to those sensing points which are occupied in each successive profile. A system (75) employs several interconnected modules (24) each comprising a pressure pad (26) having switch contacts (32, 33) which are short-circuited when pressure is applied thereto. Such a method and system may be employed within an elevator car dispatcher (94).

Description: Method and system for estimating an area of occupied floor space FIELD OF THE INVENTION This invention relates to a method and system for estimating an area of occupied floor space within a confined area of floor space. In particular, the invention finds application for estimating the number of additional occupants which can be allowed entry to an elevator car. BACKGROUND OF THE INVENTION The floor space in an elevator car and in all other confined areas can comfortably accommodate a limited number of passengers. Specifically, the number of people who can be crowded into an elevator car depends partly on their weight, since elevators are designed to carry no more than a maximum safe load; and partly on the actual floor space which they occupy. An elevator full of young children, for example, may well allow for the entry of yet more passengers without exceeding the safe load, and yet be physically so crowded that the entry of additional passengers would be uncomfortable for those passengers already in the elevator car. It often happens that somebody calls an elevator from a landing stage causing the elevator car to stop at that landing stage, only to find that the elevator car is already so crowded that the person calling the elevator is denied entry. The fact that the elevator car nevertheless has slowed down and stopped at the landing stage, opened its doors in vain and then closed its doors prior to continuing its journey, significantly slows down the despatch rate of the elevator, increases the waiting time for people awaiting the elevator at a landing stage and, of course, inconveniences those passengers who are already in the elevator car. This inconvenience would be reduced, and the overall efficiency of the elevator despatch rate would be increased, if the elevator car were to ignore a landing stage call if the elevator car were already full to capacity. More generally, the despatch rate would be improved if the elevator stopped at a landing stage only if there were sufficient free space in the elevator to accommodate the additional passengers. Specifically, if the elevator despatch system "knows" the available space in each elevator car, it can use this information to optimize the allocation of cars to a required landing stage. For example, the lobby and restaurant floors in hotels are usually crowded and would therefore be allocated a less crowded car. Of course, such an approach would not prevent a passenger within the elevator car from stopping the elevator car at any desired landing stage in order to allow the passenger's exit from the elevator car. It would also be desirable to allocate an elevator car based on prior knowledge of the number of passengers waiting at a given landing stage. Were such information available to the despatch system as well as the occupancy of each elevator car, then the despatch system could be more discriminating in which elevator car is despatch to each floor: specifically, an elevator car with nearly full occupancy would not be allocated to a floor having a large number of awaiting passengers. Some modern elevator systems attempt to estimate the number of passengers in an elevator car simply by dividing the payload weight by 75 Kg which is considered a reasonable average passenger weight. The accuracy of such an approach is inevitably poor for several reasons. First, a child weighing only 25 Kg nevertheless occupies more than one-third the living space of the so-called average adult passenger. Secondly, the payload may be made up of packages such as luggage, boxes and the like for which the ratio between their weight and the floor area which they occupy is indeterminate. For example, a suitcase weighing only 10 Kg may occupy an area sufficient for accommodating two passengers. It will be equally apparent that merely measuring the combined weight of the passengers does not provide a reliable estimation as to whether the elevator car is full because large numbers of passengers each having less than an average adult weight may well not exceed the permitted loading of the elevator, whilst nevertheless the elevator car may be so congested as not to permit the entry of yet more passengers. European Patent Application No. 544 540 in the name of the OTIS Elevator Company discloses an elevator system having improved crowd service based on empty car assignment. The current passenger load of the elevator car is determined and a special bonus is assigned to an empty car so that, in response to a call signal from a landing stage, preference is given to an empty car over one which is already in service. As explained in EP 544 540, car load measurement is periodically read by a door control subsystem which is responsive to the number of people entering and leaving the elevator car for determining whether or not the car is empty. In the specific example recited in EP 544 540, the measured car load is converted into boarding and deboarding passenger counts by a motion control subsystem. Typically, an electronic eye is used which permits the number of bodies entering and exiting from the elevator car to be tallied. However, such an approach takes no account of the actual space occupied by a body entering the elevator. For example, young children occupy less room than do adults and, consequently, more children can be accommodated in the elevator car than adults. Furthermore, a long object which maintains eye contact with the electronic eye on entry to the elevator car is registered as a single "passenger" even though it might have a broad base area and therefore effectively occupies the equivalent space of several passengers. Alternatively, a passenger who takes in with him, for example, a side rail from a baby crib whose rails make intermittent contact with the electronic eye may possibly be registered as several discrete objects even though the complete side rail when held upright occupies very little actual floor space. Furthermore, door control systems perform a differential measure- ment and determine the number of passengers in the elevator on the basis of the difference between those passengers entering and those leaving the elevator car. The difference is then added to a "base count" which is initialized to zero when the elevator car is empty, in order to calculate the actual number of passengers currently in the elevator car, this figure being stored in a memory and being used as the "base count" in the next computation. This approach is prone to error if the "base count" becomes corrupted, for any reason, and also the errors tend to accumulate. It is apparent, then, that merely counting the number of boarding and deboarding passengers by means of an electronic eye, for example, is unsatisfactory. SUMMARY OF THE INVENTION It is an object of the invention to provide a method for estimating an amount of free area of floor space within a predetermined floor area, in which the above-mentioned drawbacks are significantly reduced or eliminated. It is a particular object of the invention to provide a more reliable estimate as to whether more passengers can be permitted entry into the confined space of an elevator car and to estimate how many. It is a further object of the invention to estimate the combined area of passengers and luggage waiting for an elevator car at a landing stage thereof. According to a broad aspect of the invention there is provided a method for estimating an amount of occupied area of floor space within a predetermined floor area, the method comprising the steps of: (a) dividing said predetermined floor area into a known plurality of sensing points, (b) determining all occupied sensing points as contacting sensing points corresponding to all of said plurality of sensing points which are in actual contact with an object, (c) dividing said occupied sensing points by said known plurality so as to determine an estimated fractional occupied area, and (d) multiplying said fractional area by said predetermined floor area in order to estimate the amount of occupied area. The method may be extended to estimate a number of additional people who may be allowed to enter the floor space, by dividing the estimated amount of free area of floor space by an average body area being equal to the area of an average person's torso at shoulder height plus a comfortable boundary area to allow for a reasonable spacing between passengers. This assumes that each person is standing substantially upright with his or her feet comfortably, but not too far, apart. Such a method finds application for estimating the number of additional passengers who may be allowed entry into an elevator car. According to a preferred embodiment of the invention, step (b) comprises: (bl) determining all contacting sensing points corresponding to all of said plurality of sensing points which are in actual contact with an object, (b2) for every pair of contacting sensing points, determining a corres¬ ponding inter-sensing point spacing, (b3) comparing each of the inter-sensing point spacings with a predetermined base size threshold, and (b4) for each inter-sensing point spacing which is no greater than the base size threshold, identifying all intermediate sensing points which lie on an imaginary line joining the respective pair of contacting sensing points or on either side thereof as associated sensing points; said occupied sensing points being equal to the union of contacting sensing points and associated sensing points. When the invention is employed for estimating the number of additional passengers who may be allowed entry into an elevator car, the predetermined base size threshold corresponds to the distance between an average person's pair of feet when standing substantially upright with his or her feet comfortably, but not too far, apart. By such means, an area surrounding both the passenger's feet is identified as occupied. If a passenger stands with his legs spread so far apart that the inter-feet distance exceeds the base size threshold, then an area surrounding each of the feet separately is identified as occupied but the intermediate area between the passenger's feet is not identified as occupied. This correctly allows for the entry of more passengers into the elevator car, possibly requiring that any passengers whose feet are too far apart, draw their feet together. Furthermore, in order to prevent adjacent passengers from encroaching on each other's territory, a boundary area is preferably added around the space associated with each passenger so as to provide a comfortable spacing between passengers. This additional step is not necessary if the invention is used, for example, to estimate the number of packages which can be accommodated in a storeroom, when there is no need to provide a fixed boundary spacing between adjacent packages. The same approach may be employed in order to determine an estimate of the floor area occupied by passengers and their floor-mounted luggage awaiting entry to an elevator car at a landing stage thereof. Such information may then be fed together with the estimated availability of the elevator car to the car despatch system so as to provide better discrimination and more efficient allocation. BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment relating to the estimation of free floor space in an elevator car will now be described, by way of non¬ limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic plan view of a person useful for explaining the principle of the invention; Figs. 2a, 2b and 2c are flow diagrams showing the principal steps associated with a method according to the invention; Fig. 3 is a block diagram showing the principal components associated with a system for carrying out the invention; Fig. 4 shows schematically a plurality of interconnected modules each comprising a pressure pad for monitoring an area of interest using the system shown in Fig. 3; Fig. 5 shows pictorially an exploded view of the module shown in Fig. 4; Fig. 6 shows schematically a detail of the pressure pad within the module shown in Fig. 4; Fig. 7 shows schematically a detail of a switch element forming the basis of each pressure pad shown in Fig. 6; Fig. 8 illustrates schematically a first approach to connecting the switch elements shown in Fig. 7 to the processing unit shown in Fig. 3; Fig. 9 is a detail of a circuit arrangement for interconnecting the switch elements shown in Fig. 8 so as to allow for proper discrimination therebetween; Fig. 10 illustrates schematically a second approach to connecting the switch elements shown in Fig. 7 to the processing unit shown in Fig. 3; Fig. 11 shows schematically the modules of Fig. 4 connected to a common bus; Fig. 12 shows pictorially an exploded view of the pressure pad shown schematically in Fig. 6; Fig. 13 is a pictorial representation of footprint pairs identifiable by the pressure pad shown in Fig. 4; Fig. 14 is a schematic representation of a grid having a plurality of sensing points some of which have been identified as "occupied" in accordance with the invention; Fig. 15 is a block diagram showing functionally the principal components in a system according to the invention; Fig. 16 is a block diagram showing functionally a first detail of the system illustrated in Fig. 15; Fig. 17 is a block diagram showing functionally a second detail of the system illustrated in Fig. 15; and Fig. 18 is a block diagram showing functionally additional components for converting the system of Fig. 15 to a dynamic system in an elevator despatch system. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows schematically in plan view a person 10 having a head 11 and two feet 12 and 13 spread apart a comfortable distance D , constituting a predetermined base size threshold. The principle of the invention requires that the person 10 stands on a sensing point grid so as to apply foot pressure thereto, whereby the location of those grid sensing points to which pressure is applied may be sensed. By such means, pressure will be applied within the area of the person's feet 12 and 13. However, as will be explained below with particular reference to Fig. 14 of the drawings, owing to variations in people's shoes, pressure is not uniformly applied to grid sensing points even within the area of the feet 12 and 13. For example, no pressure is applied within the area of a shoe's arches, causing discrete pressure points to be sensed relating to the heel and toe portions of the shoe although it is not immediately apparent from the resulting pressure profile which sensing points relate to the same shoe. The purpose of the invention is to determine from the actual pressure points a plurality of boundary areas designated by the dotted line 14 as being "occupied" whereby the total area of occupied space in the elevator car may be calculated. This, of course, allows the area of free space to be calculated since the actual floor area of an empty elevator car is known. By dividing the calculated area of free space by an average body area such as the boundary area 14, the number of additional passengers who can be accommodated within the elevator car may be determined. If required, this figure can be fed to a conventional elevator despatch algorithm such as discussed in the opening section of the specification. In order for the invention to achieve its objective, it is necessary to determine the boundary area 14 from a knowledge of discrete grid sensing points to which foot pressure is applied. Specifically, the areas 12 and 13 must be located, and an area 15 between the areas 12 and 13 must be pcχ/IL96/00038 - 10 - associated therewith so as to designate it too as "occupied". This permits determination of a periphery 16 corresponding to the effective floor space occupied by the passenger 10. However, the actual area 14 occupied by the passenger 10 is somewhat greater than the periphery 16 since it is his torso area at shoulder height which occupies the greatest area. In order to allow for this and also to provide a comfortable boundary between adjacent passengers, the boundary area 14 is derived by constructing circles 17 of radius R around the periphery 16. This approach is summarized in Figs. 2a and 2b of the drawings. Located on the floor of the elevator car (not shown) is a pressure pad which is described in greater detail below with particular reference to Figs. 4 and 5 of the drawings. In order to understand the method, it is sufficient at this stage to appreciate that the pressure pad employs pressure elements at each sensing point so as to allow for the location of all sensing points on the floor of the elevator car which are subjected to pressure. This allows for determination of specific grid sensing points within the feet area 12 and 13 shown in Fig. 1. The inter-sensing point spacing between each pair of grid sensing points is now calculated and compared with the predetermined base size threshold D . For each pair of grid sensing points which are separated by a distance no greater than D j , an imaginary line is constructed between the two sensing points and all grid sensing points which intersect or lie on either side of the line between the two end sensing points, are also marked as "occupied". This step is repeated for all sensing point pairs and allows the periphery 16 shown in Fig. 1 to be defined. Thereafter, imaginary circles 17 of radius R are constructed around each grid sensing point on the periphery 16 so as to derive the extended boundary area 14. All grid sensing points within the boundary area 14 are thus designated as being "occupied". Since the total number of grid sensing points as well as the actual floor area of the elevator car are known, the average floor area per grid sensing point may easily be computed. Likewise, the number of available grid sensing points, and thus free floor space, may be determined. This is then fed to an elevator despatch algorithm for further processing in order to optimize elevator despatch according to the number of awaiting passengers at each landing stage and the number of additional passengers who can comfortably be accommodated in the elevator car. Fig. 2c shows an extension to the above method for estimating the floor area occupied by passengers and their floor-mounted luggage awaiting entry to an elevator car at a landing stage thereof. In such case it is necessary to discriminate between people who are actually waiting for the elevator and people who just happen to have passed the landing stage en route to other locations. In other words, only the static situation represented by the genuine passengers is of interest and not the transient situation represented by passing trade. This is not the case within the elevator car itself because the passengers are confined therein and even if they move around within the elevator car, the net occupied area remains unchanged. As seen in Fig. 2c, after initialization of variables M and N, a pressure profile of the floor area of the landing stage is repeatedly measured and stored as a matrix j y for N j times with a slight delay ΔT between each successive measurement. Each pressure profile in effect is a matrix whose values are either 0 when no pressure is applied to the pressure element, or 1 when pressure is applied thereto. When N- j > pressure profiles have thus been measured and stored, the N j pressure profiles are logical ANDed: the resulting matrix indicating which pressure elements were constantly depressed throughout all N j measurements. By such means the effect of transient movements across the pressure pad may be suppressed. The resulting pressure profile is now fed to the algorithm described above with reference to Figs. 2a and 2b of the drawings, so as to estimate the total occupied area 5^ of the elevator landing stage. This value is likewise stored. As successive cycles are repeated, the estimated occupied area may be smoothed by performing a weighted moving average S given by: W- - 1 S = / a i S M _ i i =0 where d j are weighting coefficients such that: N 2 - l Σ β , = ι i = 0 For example, for Ν2 equal to 3, ag = 0.5, a j = 0.3, (I2 = 0.2. This operation is, in fact, low-pass filtering allowing only slow movements to pass. The weighted average is then fed together with the estimated availability of the elevator car to the car despatch system so as to provide better discrimination and more efficient allocation. Fig. 3 shows schematically a system 20 for estimating an occupied area of floor space to which pressure is applied by a plurality of discrete bases (e.g. feet, objects, stroller wheels etc.). The system 20 comprises a location determination means 21 for determining all sensing points of the floor space under each base and a processing unit 22 which includes therein a memory and processes the sensing points in accordance with the method described above with reference to Fig. 1 and Figs. 2a, 2b and 2c of the drawings. The output of the processing unit 22 is used by the elevator car despatch system. Fig. 4 shows an area of interest 23 monitored by a plurality of modules 24 in the form of interconnected tiles shown in detail in Fig. 5. Each module 24 comprises a rigid base 25 for supporting thereon a pressure pad 26. The modules 24 are electrically interconnected by means of flat multi-core cables 27 accommodated within a recess 28 underneath each module 24. Figs. 6 and 7 show schematically a detail of the pressure pad 26 each of which comprises a plurality of pressure elements 30 which may be depicted as a normally open switch 31 having first and second contacts 32 and 33, respectively, which are short-circuited by a short-circuiting electrode 34 (constituting a short-circuiting means) when pressure is applied thereto. The first contact 32 of all the switches 31 is commonly connected to a source of voltage 35 so that when the corresponding switch 31 is closed, voltage is applied to the second contact 33 of the switch 31 as shown in Fig. 7. The voltage at the respective second contact 33 of each switch 31 in the pressure pad 26 is monitored by a voltage detector 36 (constituting an electrical signal detection means) in order to determine which of the switches 31 in the pressure pad 26 are closed, thus permitting the pressure profile y to be determined for use with the algorithm described above with reference to Figs. 2a, 2b and 2c of the drawings. In order to monitor the voltage at the respective second contact 33 each switch 31, each second contact 33 must be connected to the processing unit 22 shown in Fig. 3. The resolution of the pressure pad 26 is a function of the number of pressure elements 30 per unit area thereof. Thus, in order to increase the resolution, more switches 31 must be provided and this, in turn, dictates that more connections to the processing unit 22 are required. The two contacts 32 and 33 of the switches 31 are typically printed on a printed circuit board (PCB) (as shown in Fig. 12) so as to be short-circuited when an electrically conductive pad is pressed down thereon. In this case, the first contact 32 of each switch 31 is connected to a common voltage bus whilst the second switch contact 33 is connected via a respective PCB track to the processing unit 22. It is clear that in order for the processing unit 22 to recognize the status of each pressure element 30, the second contact 33 of each switch 31 must be connected to the processing unit 22 by a separate core in the multi- core cable 27. Since the number of pressure elements 30 in each pressure pad 26 should be large in order to increase the resolution thereof, this implies a correspondingly large number of cores in the multi-core cable 27, rendering the system both costly and impractical. It is therefore desirable to reduce the number of separate connections from the pressure pad 26 to the processing unit 22 without degrading the resolution of the pressure pad 26. Two different approaches towards realizing this objective will now be explained. Fig. 8 shows one possible approach wherein the switches 31 are arranged in groups 37 so that the respective second contacts 33 of each switch 31 in the group 36 are commonly connected to the processing unit 22. Thus, the number of separate connections from the second contacts 33 to the processing unit 22 is reduced by a factor equal to the number of switches 31 in each group 37. However, this must be done in a way which still allows for proper discrimination as to which of the switches 31 in each group is closed. Fig. 9 shows how this may be achieved. The group 37 contains three switches 38, 39 and 40 each having respective first and second contacts 32 and 33. The first contacts 32 are each connected to respective resistors 41, 42 and 43 having different resistances so that when they are connected across the voltage source 35 different currents flow through each of the resistors. The second contacts 33 are commonly connected to an ammeter 44 (constitu¬ ting an electrical signal detection means) which measures the total current flowing through each of the resistors 41, 42 and 43 and thus permits the processing unit 22 connected thereto to determine which of the switches 38, 39 and 40 are closed. Specifically, if the voltage of the voltage source 35 be denoted by V and the resistances of the resistors 41, 42 and 43 be denoted respectively by R j , R2 and R3 then the following table shows the ammeter readings for each combination of switch position: Thus, providing the resistances R j , R2 and R3 are sufficiently resolved, the ammeter reading permits proper discrimination as to which of the switches 38, 39 and 40 are closed. Since each switch group 37 requires only one connection to the ammeter 44, by increasing the number of switches in each group, the number of separate connections to the ammeter 44 may be reduced accordingly. The size of each group 37 is limited in practice by the accuracy tolerance of the resistors 41, 42 and 43. Fig. 10 shows the pressure pad 26 having a plurality of pressure elements 30 as shown in Fig. 6 each comprising switches 31 whose first switch contacts 32 are commonly connected to the voltage source 35. The second switch contacts 33 of each switch 31 are separately connected to a corresponding input 45 of a multiplexer 46 having a select wire 47 and an output 48 connected to the processing unit 22. Each mutliplexer 46 in the system has a unique address and may be addressed by the processing unit 22 so as to output serially (bit after bit) to the processing unit 22 the logical status ("0" or "1") of each switch 31 on the output 48. The use of the multiplexer 46 on board the pressure pad 26 obviates the need to route all the connections to each pressure element 30 to the processing unit 22. Fig. 11 shows an extension to the system described above with reference to Fig. 10 wherein several modules 49, 50 and 51 each having respective on board multiplexers 52, 53 and 54 are connected to the processing unit 22 via a common bus 55. Alternatively, although less desirably, each module 24 may be connected separately to the processing unit 22 using a star like topology. Fig. 12 shows pictorially an exploded view of the pressure pad 26 for mounting on the base 25 in the module 24. For ease of understanding, identical reference numerals are employed to refer to those components which have already been described. The pressure pad 26 comprises a printed circuit board (PCB) 56 having a plurality of pressure elements in the form of normally open switches 31 whose first and second contacts 32 and 33. respectively, are printed on an upper surface 59 of the PCB 56. The second contacts 33 are connected via silver plated feed-through holes (not shown) to printed on a lower surface 60 thereof where they are separately routed to the multiplexer 46 which is mounted on the PCB 56 as shown in Fig. 10. Likewise, the voltage source 35 is commonly connected to first contacts 32 as shown schematically in Fig. 7. In order for the voltage source 35 to be connected by one of the switches 31 to the multiplexer 46 and thus to the processing unit 22, the corresponding short-circuiting electrode 34 must effect releasable contact with the first and second switch contacts 32 and 33 whenever pressure is applied to the corresponding switch 31 or within a predeteπnined radius thereof. The short-circuiting electrodes 34 are electro-plated on an electrode laver 61 of electrically insulating flexible material, such as polyethylene. having a thickness of between 200 and 600 micron which is separated from the upper surface 59 of the PCB 56 via an electrically insulating spacer layer 62. The spacer layer 62 is also formed of insulating flexible material such as polyethylene with a thickness of between 200 and 800 micron and has apertures 63 therein so that when the two layers 61 and 62 are properly aligned with the PCB 56, the short-circuiting electrodes 34 lie over the corresponding first and second switch contacts 32 and 33 of the respective switches 31. An uppermost layer 64 in the form of a rubber mat having a plurality of downwardly depending protrusions 65 aligned with the apertures 63 of the spacer layer 62 is mounted on top of the electrode layer 61. When pressure is applied to the uppermost layer 64, the protrusions 65 depress a corresponding one of the electrodes 34 into contact with the first and second contacts 32 and 33 of the respective switch 31. The switches 31 thus constitute occupied sensing point determination means for providing an indication of which of the sensing points defined by the switches 31 are subjected to contact pressure. It is necessary that the pressure pad 26 be designed and constructed in such a manner that at least one pressure element is activated even when pressure is applied over only a small area of the uppermost layer 64, for example by a woman's stiletto heal. At the same time, it is not admissible that pressure applied to one point of the pressure pad 26 will activate pressure elements 30 in any region not bordering thereon. These requirements can be met by controlling the following main parameters: (a) density of pressure elements i.e. number of pressure elements per unit area of the pressure pad; (b) shape and dimensions of the apertures 63 in the spacer layer 62; (c) material and thickness of the spacer layer 62; (d) thickness and rigidity of the electrode layer 61; (e) rigidity of the uppermost layer 64; (f) shape and dimensions of the protrusions 65 in the uppermost layer 64; Fig. 13 is a pictorial representation of an elevator car floor area on which is placed a high resolution pressure pad (not shown). Different types of footprint 66, 67 and 68 are shown corresponding, respectively, to a sports shoe or sneaker having a flat base, a lady's high heeled shoe having a toe portion and a stiletto heel and a regular man's shoe having front and heel portions. By means of the method described above with reference to Figs. 2a, 2b and 2c of the drawings, each of the footprints may be isolated and the two footprints 69 and 70, for example, having a boundary area 71 may be marked as "occupied". This, in turn, permits calculation of the estimated torso area of the person, the whole calculation being repeated in respect of all contact points so as to derive therefrom the cumulative occupied area. Fig. 14 shows a computer printout of a representation of the grid shown pictorially in Fig. 13. Those grid sensing points 72 to which pressure is applied directly are shown darkly shaded, whilst those sensing points 73 to which no pressure is applied but which are subsequently marked as being "occupied" are shown with an intermediate hue. The grid sensing points 74, corresponding to the boundary area, are shown in a light shade. The total number of dark and light sensing points, corresponding to the union of contacting sensing points and associated sensing points, define the total occupied area, thus permitting the available space to be determined as explained in detail above. Fig. 15 shows the principal components in a system 75 for estimating an amount of occupied area of floor space within a predetermined total floor area. The system 75 comprises a SENSOR 76 having a plurality of sensing points placed on the floor space so as to define an effective area of floor space per sensing point. A PROCESSING MEANS shown generally as 77 is coupled to the SENSOR 76 for processing those sensing points subjected to pressure so as to calculate the estimated occupied floor area. The PROCESSING MEANS 77 comprises an OCCUPIED SENSING POINT DETERMINATION MEANS 78 for determining all occupied sensing points which, in the simplest case, are simply those sensing points in direct contact with an object placed on the floor area. A FIRST DIVISION MEANS 79 is coupled to the occupied sensing point determination means for dividing the occupied sensing points by the known plurality of sensing points in the SENSOR 76 so as to determine an estimated fraction of occupied area. A MULTIPLICATION MEANS 80 is coupled to the FIRST DIVISION MEANS 79 for multiplying the estimated fractional area by the floor area in order to estimate the amount of occupied area. The system shown in Fig. 15 provides a reliable estimate only in those specific cases where an object makes uniform contact with the floor area. This will usually be the case, for example, with heavy cartons and similar objects having a planar lower surface which are disposed on the floor area such that all points on the lower surface of the objects are in contact with the floor area. However, such a situation does not obtain when the lower surface of the object is arched as is generally the case in people's footwear, for example. In this case, the occupied points must include not only the actual contacting points but also any associated sensing points which, whilst not in pressure contact with the object, are occupied thereby. Fig. 16 shows the principal components in the OCCUPIED SENSING POINT DETERMINATION MEANS 78 allowing for more accurate estimation of the occupied sensing points even when the object in contact with the floor area does not make uniform contact therewith over the whole surface of the object. An INTER-SENSING POINT SPACING COMPUTING MEANS 81 is provided for determining corresponding inter-sensing point spacing between each pair of contacting sensing points. It may be assumed that those actual contacting sensing points which are in close proximity to one another belong to the same object and there is therefore provided a FIRST MEMORY 82 for storing therein a predetermined base size threshold. A COMPARATOR 83 is coupled to the INTER-SENSING POINT SPACING COMPUTING MEANS 81 and to the FIRST MEMORY 82 for comparing each of the inter-sensing point spacings with the predetermined base size threshold so that only those contacting sensing points whose inter-sensing point spacing is less than or equal to the threshold are associated with the same object. These points are fed to a SENSING POINT ASSOCIATION MEANS 84 which constructs an imaginary line between each respective pair of contacting sensing points and identifies all sensing points intersecting the imaginary line or lying on either side thereof as associated sensing points. The output of the SENSING POINT ASSOCIATION MEANS 84 thus provides an indication of those additional sensing points which, whilst not in actual contact with an object, are nevertheless associated therewith. In the case of cartons, packages and the like which are to be stored in a confined area, the objects can be juxtaposed to one another with no inter-object spacing. However, this is not the case with human beings who require a "breathing space" in order to avoid discomfort. Therefore, a BOUNDARY DEFINITION MEANS 85 is coupled to the SENSING POINT ASSOCIATION MEANS 84 and is responsive to the occupied sensing points which are set equal to the union of contacting sensing points and associated sensing points so as to surround each of the occupied sensing points with an imaginary circle of predeter¬ mined radius. The BOUNDARY DEFINITION MEANS 85 identifies all the occupied sensing points within the circle as boundary sensing points. In effect, the boundary sensing points define those sensing points in the floor area which, whilst not actually occupied by an object, are nevertheless surrounding an object and constitute the "breathing space" of that object. The occupied spacing points may now be set to the union of the contacting sensing points, the associated sensing points and the boundary sensing points. The system as shown in Figs. 15 and 16 provide estimates of an occupied area of floor space. In certain applications it may be important to know not the occupied area but, rather, the free, or available, area and then to determine a number of objects of average size which can be accommo- dated therein. One such application requiring such data is an elevator car despatch system. Fig. 17 shows the additional components which must be provided in the system 75 for providing these features. The PROCESSING MEANS 77 contains the same elements as shown in Fig. 15 but, in addition, comprises a SUBTRACTING MEANS 86 coupled to the MULTIPLICATION MEANS 80 for subtracting the estimated amount of occupied area of floor space from the total floor area so as to determine an estimated amount of free area of floor space. A SECOND MEMORY 87 is provided having stored therein a predeter¬ mined average body area. The SUBTRACTING MEANS 86 and the SECOND MEMORY 87 are coupled to a SECOND DIVISION MEANS 88 for dividing the estimated amount of free area of floor space by the predetermined average body area, so as to estimate a number of additional bodies which can be allowed to make contact with the floor space. The systems described above with reference to Figs. 15 to 17 of the drawings are static systems which provide reliable estimates when an object placed on an area of floor space remains in contact therewith. If desired, the system 75 can be converted to a dynamic system 89 which allows the effect of any objects having only momentary contact with the floor area to be ignored. Fig. 18 shows the additional components which must be provided in such a system 89. The SENSOR 76 is coupled to a THIRD MEMORY 90 which is responsively coupled to a TIMER MEANS 91 for sampling the contacting sensing points at discrete time intervals ΔT and storing successive pressure profiles. A LOGICAL 'AND' MEANS 92 is coupled to the THIRD MEMORY 90 for accepting as contacting sensing points only those sensing points which are contacting in each pressure profile so as thereby to suppress an effect of transient movement over the floor space. In the case where the SENSOR 76 comprises pressure elements constituted by switches which are either ON (logical "1") or OFF (logical "0"), the LOGICAL 'AND' MEANS 92 performs the logical AND operation on each respective logic state in the THIRD MEMORY 90. By such means, only those switch elements which are ON (logical "1") throughout all the successive samples are accepted as contacting sensing points. The output of the LOGICAL 'AND' MEANS 92 is a pressure profile containing only those sensing points which are contacted in each pressure profile. The output pressure profile is processed by the OCCUPIED SENSING POINT DETERMINATION MEANS 78 in the normal manner and fed to an AVERAGING MEANS 93 for performing a weighted moving average and to a DESPATCHING MEANS 94 which is responsively coupled to a STATIC SYSTEM 75, such as described above with reference to Fig. 17, and which employs a pressure pad within the elevator car for estimating the free area therein. The DESPATCHING MEANS 94 is responsive to the estimated free area within the elevator car and the estimated occupied area on the landing stage thereof for despatching the elevator car to the landing stage in accordance with the despatcher algorithm. The despatcher algorithm is not itself a feature of the present invention. Although the invention has been described with particular reference to determining the number of additional passengers who can be admitted to an elevator car, it will be understood that the method according to the invention will find more general application wherever the cumulative floor space of a number of objects in base contact with a floor area is to be determined. For example, even in the specific embodiment described, it will readily be understood that a baby carriage, for example, will still apply pressure to the floor area at each of its four wheel bases and, since the opposite pairs of wheel bases occupy approximately the same base as a young child, the four wheel bases associated with the baby carriage may be considered as approximately equal in area to two children each having a base area approximately half that of the baby carriage. If, on the other hand, a hospital bed or other large object were placed inside the elevator car, since no pressure contact would result from the whole area of the bed apart from the four wheel bases, this would result in the calculation of apparently more available room than actually existed. However, in environments such as hospitals and the like where elevator cars commonly transport items having bases significantly larger than those associated with people, a suitable compensation factor can be built into the calculation merely by increasing the average body area associated with each base. It will also be understood that the invention will find general application wherever there is a need to estimate the area occupied by a number of bodies or objects maintaining base contact with an area of floor space. As noted above, the objects can be inanimate and can have any number of base areas (such as wheel bases, for example) providing they have an overall maximum body size which is an approximate known function of the area of its combined base contact. It will further be appreciated that if the invention is employed to estimate the number of inanimate objects which can be accommodated in a fixed space, such as packages in a storeroom, then there is no need to provide a fixed boundary spacing between adjacent packages. It will be appreciated that, whilst the invention has been described with particular reference to the use of a pressure pad, the method according to the invention is independent of the source of contact points and it is thus envisaged that transducers other than pressure transducers might be employed in order to determine the contact points. Finally, it is to be noted that the whilst system described functionally with reference to Figs. 15 to 18 may, as described, be implemented using discrete hardware elements, it is envisaged that the processing unit will be implemented in software using a suitably programmed microprocessor and associated circuitry.

Claims: CLAIMS: 1. A method for estimating an amount of occupied area of floor space within a predetermined floor area, the method comprising the steps of: (a) dividing said predetermined floor area into a known plurality of sensing points, (b) determining all occupied sensing points as contacting sensing points corresponding to all of said plurality of sensing points which are in actual contact with an object, (c) dividing said occupied sensing points by said known plurality so as to determine an estimated fractional occupied area, and (d) multiplying said fractional area by said predetermined floor area in order to estimate the amount of occupied area. 2. The method according to Claim 1, wherein step (b) comprises the additional steps of: (bl) for every pair of contacting sensing points, determining a corres¬ ponding inter-sensing point spacing (D τ ), (b2) comparing each of the inter-sensing point spacings with a predetermined base size threshold, and (b3) for each inter-sensing point spacing which is no greater than the base size threshold, identifying all intermediate sensing points which lie on an imaginary line joining the respective pair of contacting sensing points or on either side thereof as associated sensing points; said occupied sensing points being set equal to the union of contacting sensing points and associated sensing points. 3. The method according to Claim 2, further including: (b4) surrounding each of said occupied sensing points with a circle (17) of predetermined radius (R) and identifying all sensing points within said circle as boundary sensing points; said occupied sensing points being set equal to the union of contacting sensing points and associated sensing points and boundary sensing points. 4. The method according to any one of Claims 1 to 3, wherein step (b) comprises deriving a cycle of successive pressure profiles at discrete time intervals ΔT within the cycle and accepting as contacting sensing points which only those sensing points which are contacting in each pressure profile so as thereby to suppress any effect of transient movement over the floor space. 5. The method according to Claim 1, further including the steps of: (e) from a knowledge of the estimated occupied area and the total area of floor space, estimating an amount of free area of floor space, (f) dividing the free area of floor space by a predetermined average body area equal to an area of the body at its broadest extremity projected on to the floor space so as to determine a number of additional bodies which can be allowed to make contact with said floor space. 6. The method according to any one of Claims 1 to 3, wherein each one of said plurality of sensing points is implemented by means of contact pressure with said floor space. 7. The method according to Claim 6, wherein said floor space is associated with an elevator car. 8. A system (75) for estimating an amount of occupied area of floor space within a predetermined total floor area (23), the system comprising: a sensor (76) having a known plurality of sensing points placed on said floor space so as to define an effective area of floor space per sensing point, processing means (22, 77) coupled to the sensor and comprising: occupied sensing point determination means (78) for determining all occupied sensing points as contacting sensing points corresponding to all of said plurality of sensing points which are in actual contact with an object, first division means (79) for dividing the occupied sensing points by the known plurality so as to determine an estimated fractional occupied area, and multiplication means (80) for multiplying said estimated fractional area by said predetermined floor area in order to estimate the amount of occupied area. 9. The system according to Claim 8, wherein the occupied sensing point determination means (78) comprises: inter-sensing point spacing computing means (81) for determining a corresponding inter-sensing point spacing between each pair of contacting sensing points, a first memory (82) for storing therein a predetermined base size threshold, comparator means (83) coupled to the first memory and to the inter- sensing point spacing computing means for comparing each of the inter- sensing point spacings with the predetermined base size threshold, and sensing point association means (84) coupled to the comparator means and responsive to an inter-sensing point spacing being no greater than said threshold, for constructing an imaginary line joining the respective pair of contacting sensing points and identifying all sensing points intersecting said imaginary line or lying on either side thereof as associated sensing points; said occupied sensing points being set equal to the union of contacting sensing points and associated sensing points. 10. The system according to Claim 9, wherein the occupied sensing point determination means further comprises: boundary definition means (85) for surrounding each of said occupied sensing points with an imaginary circle of predetermined radius and identifying all sensing points within said circle as boundary sensing points; said occupied sensing points being set equal to the union of contacting sensing points and associated sensing points and boundary sensing points. 11. The system according to Claim 10, further including a second memory (87) for storing therein a predetermined average body area; wherein the processing means (22, 77) further includes: a subtracting means (86) coupled to the multiplication means (80) for subtracting the estimated amount of occupied area of floor space from the total floor area so as determine an estimated amount of free area of floor space, and a second division means (88) coupled to the second memory and to the subtracting means for dividing the estimated amount of free area of floor space by the predetermined average body area so as to estimate a number of additional bodies which can be allowed to make contact with said floor space. 12. The system according to Claim 11, wherein the average body area is a function of an area of an average person's torso at shoulder height. 13. The system according to any one of the Claims 8 to 12, wherein the sensor (76) comprises: a pressure pad (26) placed on said floor space for defining a matrix of pressure elements (30) which are coupled to a voltage source (35) and are responsive to pressure applied to the pressure elements for producing an electrical signal. 14. The system according to Claim 13, further including: a third memory (90) for storing therein a cycle of successive pressure profiles at discrete time intervals ΔT within the cycle, and logical AND means (91) coupled to the third memory for accepting as contacting sensing points only those sensing points which are contacting in each pressure profile so as thereby to suppress any effect of transient movement over the floor space. 15. The system according to Claim 14, wherein: the pressure pad (26) comprises first (56) and second (61) spaced apart insulating layers, the first layer defining a plurality of switches (31) having first (32) and second (33) open switch contacts and the second layer defining corresponding short-circuiting means (34) for closing the switch contacts when pressure is applied to the pressure pad in a region of the switch, the first switch contacts (32) are commonly connected to said voltage source (35), and the processing means (22) further includes an electrical signal detection means (36, 44) coupled via a number of electrical connections (45) to the respective second switch contacts (33) of each switch (31) so as to measure a function of the current flow therethrough indicative of pressure applied thereto. - SO - lό. The system according to Claim 15, wherein the switches (31) are arranged in groups (37) each comprising an equal number of switches connected in series with a different value resistance (41, 42, 43) so that when each switch in the group is closed, the corresponding current flow through each switch in the group is different, thus permitting said number of electrical connections to be reduced. 17. The system according to Claim 15, wherein the switches (31) are connected to the processing means (22) via a multiplexing means (46), thus permitting said number of electrical connections to be reduced. 18. The system according to Claim 17, comprising at least two pressure pads (49, 50, 51) interconnected via a common bus (55) to the processing means (22). 19. The system according to Claim 17, comprising at least two pressure pads (49, 50, 51) separately connected to the processing means (22). 20. The system according to Claim 15, wherein the pressure pad (26) includes an insulating separating layer (62) disposed between the mutually displaceable insulating layers having an aperture (63) substantially coaxial with each of said switches (31). 21. The system according to Claim 20, wherein the pressure pad (26) further includes an uppermost insulating layer (64) having a protrusion (65) substantially coaxial with each of said switches (31) so as to bear down on an upper one of the insulating layers and urge the short-circuiting means (34) towards the first and second switch contacts when pressure is applied within a predetermined radius of the corresponding switch. 22. The system according to Claim 8, wherein said floor space is associated with an elevator car. 23. The system according to Claim 10, wherein: said floor space is contained within an elevator car, and a despatching means (94) is coupled to the processing means (77) and is responsive to the estimated occupied area for determining whether additional bodies can be allowed to make contact with said floor space. 24. The system according to Claim 23, including: a static system (75) using a first pressure pad disposed within the elevator car for providing an estimate of the available floor area therein, a dynamic system (89) for providing an estimate of a payload area required by said payload, said dynamic system comprising: a second pressure pad (76) disposed on a landing stage of the elevator car and responsive to a payload thereon awaiting the elevator car or to transient movement on the landing stage for determining instantaneous occupied sensing points, a timing means (90) for measuring timing increments ΔT, a third memory (91) coupled to the second pressure pad (76) and to the timing means (90) for sampling instantaneous occupied sensing points and storing in the third memory a cycle of successive pressure profiles at discrete time intervals ΔT, logical AND means (92) coupled to the third memory for producing an output pressure profile containing only those sensing points which are contacted in each pressure profile so as thereby to suppress any effect of transient movement over the landing stage, and an averaging means (93) coupled to the logical AND means for determining a weighted moving average of the output pressure profile, the despatching means (94) being coupled to the static and dynamic systems and being responsive to the estimated available area within the elevator car and to the estimated payload area on the landing stage for despatching the elevator car to the landing stage. 25. The system according to any one of the Claims 8 to 12, wherein the processing means (22, 77) is a suitably programmed microprocessor.

Inventors: SHAPIRA AHARON, SHAPIRA YAIR, SHAPIRA, AHARON, SHAPIRA, YAIR
Applicants: SHAPIRA AHARON, SHAPIRA YAIR, SHAPIRA, AHARON, SHAPIRA, YAIR
Application year: 1996
Main classification: G01G19
IPC codes: G01G19, G07C9