GB2083659A - Method of elevator group control - Google Patents

Abstract

In a method of elevator group control, which selects a service elevator from among a plurality of elevators with respect to a new call made at one of a plurality of floors on the basis of a weighting equation, with respect to each elevator, estimated waiting periods at floors at which new calls are made, at floors at which calls have already been made and at floors to which the elevator is destined by calls made thereinside are calculated. The estimated waiting periods thus calculated for each elevator are converted into corresponding weighted values. The conversion to the weighted values is effected according to a function having a minimum value corresponding to a reference estimated waiting period. From the weighted values the average weighted value is calculated for each elevator. The elevator for which the average weighted value is least among the average weighted values calculated for the individual elevators is selected as a responding elevator. <IMAGE>

Description

SPECIFICATION Method of elevator group control This invention relates to an elevator group control method for determining one of the elevators which is to respond to a new call made outside the elevators.

In most large buildings two or more elevators are installed. To enhance the elevator service, more specifically in order to reducing waiting time, the elevators are controlled in various methods, in which one of the elevators is selected and responds to a new call made outside the elevators. One of the known methods is to assign an elevator to a new call, which seems to be the first to arrive at the floor where the new call has been made. This method is considered one of the best methods for controlling a group of elevators.

To determine which elevator may arrive first at the floor where a new call has been made, the periods of times which may lapse until the elevators reach the floor after the new call has been made are calculated.

The elevator that may arrive the floor in a shorter time than any other elevator is selected according to the periods calculated (hereinafter called "waiting periods").

The above-mentioned method has a drawback, however. Suppose an elevator is moving up in response to a call made at the six floor and that the elevator is passing the third floor when a new call is made at the fourth floor or a person in the elevator pushes the "4th floor" button. Then the elevator stops at the fourth floor unless any other elevator is nearer to the fourth floor when said new call is made or the person pushes the "4th floor" button. If this happens, the waiting period for the people on the six floor will be lengthened. In some cases one elevator responds to several new calls and stops at several floors until it reaches the floor where the first call assigned to it has been made. Particularly, during the busy hours the waiting periods will be very long with respect to some of the elevators. This would lower the reliability of elevator service.

Accordingly, an object of the invention is to provide an elevator group control method for making as uniform as possibie the waiting periods at the floors no matter whether. calls are made inside or outside the elevators, thereby improving the elevator service.

To achieve the object, the method according to the invention comprises a step of calculating, with respect to each elevator, the waiting periods at the floors where new calls have just been made, the waiting periods at the floors where calls have long been made and the waiting periods at the floors to which the elevator is destined by calls made therein; a step of converting the waiting periods thus calculated with respect to each elevator into weighted values according to a function having a minimum value corresponding to a reference estimated waiting period; a step of calculating the average of the weighted values for each elevator; and a step of selecting the elevator whose average weighted value is less than that of any other elevator.

Even if the status of the elevators is drastically changed by calls made inside and outside the elevators, the method of this invention can make the waiting periods at the floors and in the elevators less different to improve the elevator service and enhance the reliability thereof.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figure 1 is a block diagram showing a control mechanism, with which to carry out the method of elevator group control according to the invention; Figure 2 is a view showing a specific construction of a reference value determining circuit shown in Figure 1 and its connection to an input register in a microcomputer; Figure 3 is a view schematically showing an elevator system with three elevators serving in a ten-story building, with calls being made inside and outside the elevators at various floors; Figure 4 is a graph showing an example of the function serving as a reference for converting the estimated waiting period until arrival at destination floor into a weighted value;; Figure 5 is a flow chart illustrating the whole routine for selecting a responding elevator as an embodiment of the invention; Figure 6 is a flow chart illustrating a routine of selecting elevator responding to a call shown in Figure 5; and Figure 7 is a flow chart illustrating a routine of converting the estimated waiting periods for each elevator into weighted values, using a function table.

Now, an embodiment of the invention will be described with reference to the drawings. Figure 1 is a block diagram showing the control mechanism with which to carry out the elevator group control method according to the invention. An outside-elevator call register circuit 1 includes registers, in which calls and the directions of travel of the elevators are registered, and also which are set when a call is made. Where eight elevators are provided, in this embodiment elevator operation control apparatus 2A, 2B, . . ., 2H are provided for the respective elevators.The individual elevator operation control apparatus include respective elevator status buffers 3A, 3B, . . ., 3H, first inside-elevator call register circuits 4A, 4B, . . ., 4H, second inside-elevator call register circuits 5A, 5B, . . ., , 5H, and signal synthesizing circuit 6A, 6B, . . ., , 6H.

The elevator status buffers 3A, 3B, . . ., , 3H store data showing whether the doors at the floors are open or closed, data showing whether the elevators are moving up or down, data representing at which floors the elevators stop, data showing where in the elevator shafts the elevators are moving and data representing whether the elevators are moving or not moving.

The first inside-elevator call register circuit 4A, 4B . 4H are set when a call is registered and reset when the relevant elevator arrives at a floor of the registered call.

The second inside-elevator call register circuits 5A, 58 ..., 5H memorize calls already assigned to that relevant elevator and reset when the elevator arrives at the floor of the assigned call.

The signal synthesizing circuits 6A, 6B, . . ., 6H include each a logic addition circuits to receive the outputs of the respective first and second inside-elevator call register circuits 4A, 4B, . . ., 4H and 5A, 5B, . . ., 5H and supply their OR outputs to a wiper select circuit 7. The wiper select circuit 7 includes a rotary switch or the like, and it supplies information about a selected elevator to an input register 11 of a microcomputer 9 for writing therein in response to a select code signal supplied from an output register 10 of the microcomputer 9. A decoding circuit 8 supplies its decoded signal to the second inside-elevator call register circuits 5A, 5B, . .

., 5H in response to an output from an output register 12 in the microcomputer 9 for setting each of the second inside-elevator call registers 5A, 5B, . . ., 5H corresponding to an elevator, to which the last one of the prevailing calls has been assigned. A reference value determining circuit 14 is provided for setting the minimum value of a function used when converting estimated waiting periods to be described later into weighted values.

The registers in the microcomputer 9 each have a 12-bit construction, and the registers and interfaces (not shown) provided in the elevator status buffers 3A, 38 . . ., 3H in the respective elevator operation control apparatus 2A, 2B, . . ., 2H provided for the respective elevators are each connected through 12 lines to the wiper select circuit 7 in conformity to the 12-bit construction mentioned above although only a single line is shown in the Figure.

The construction of the reference value determining circuit 14 and the connection thereof to the input register 13 in the microcomputer 9 are as shown in Figure 2.

More particularly, the reference value determining circuit 14 is constituted by 12 relays having respective normally open switches SW1, SW2,. . . , SW12 12 resistors, R"R2, . . R2 R12 in conformity to the aforementioned 12-bit construction of the input register 13.

Now, an embodiment of the invention as a method of assigning a call to one of a plurality of elevators will be described.

Figure 3 shows a pictorial view of a ten-story building in which three elevators, namely elevators A, B and C, are installed. Here, calls from inside and outside the elevators and the positions of the elevators A, B and C are shown. Marks m and m represent car positions, marks & and V represent calls already produced and marks represents inside-elevator calls already produced. Mark A represents a call which is newly produced.

Now, how a call produced in an i-th floor is assigned to one of the elevators A, B and C shown in Figure 3 will be described. In the first place, it is assumed that the i-th floor call is assigned to the A elevator car j, and the estimated waiting period until the carj at this instant arrives at the i-th floor is calculated.

The estimated waiting period Tj' is obtained as the sum of the period which the car j needs to travel from the present position to the i-th floor and the time during which the elevator stops before arriving at the i-th floor, mainly deceleration and acceleration periods, periods for opening and closing doors and periods while the door is open.

If there are Kn calls already assigned to the car j, the estimated waiting periods TjK1, Tit2, . . ., TjKn are generally expressed as TjK = (period elapsed from the generation of the k-th floor call) + (estimated waiting period until the car arrives at the kt-th floor) + (period required for the car to make a stop at the i-th floor) .... . . . . (1) In the equation (1), the period required for the car j to make a stop at the i-th floor is unnecessary if the ke4h floor is one at which the carj makes a stop before making a stop at the i-th floor.

Likewise, if there are already inside-elevator calis made in the car j, to which the call generated at the i-th floor is assigned, the estimated waiting periods are generaliy as expressed as: TjKm = (estimated waiting period until the car arrives at the km-th floor) + (period required for the car to make a stop at the i-th floor) The estimated waiting periods T1 and T.Kl TK2 . . ., TjKn and TjKm calculated in the above way, are converted into corresponding weighted values of a predetermined function as f(Tji), f(TjK1), f(T1K2) . . ., f(TjKn) and f(TjKm). The predetermined function -mentioned above has a requirement that its characteristic has a minimum weighted value, for instance f(Tj) = 11 as shown in Figure 4, with respect to a standard estimated waiting period (Tj = 15 sec.). This function consists of first, second and third functions. The first function has a negative slope so that the weighted vaues increase to make it harder to assign the car as the estimated waiting period becomes shorter as long as the estimated waiting period is less than 14 sec.The second function has a positive slope so that the weighted values decrease to make it easy to assign the car as the estimated waiting period becomes shorter as long as the estimated waiting period ranges from 14 sec. to 30 sec. (= Tj), within said range the car can be controlled. The third function has a steep positive slope so that the weighted values sharply increase to make it much harder to assign the car as the estimated waiting period becomes longer over 30 sec.

From the weighted values as derived in the above way, the average weighted value EA for the A elevator is obtained from an equation

Likewise, the average weighted values Es and Ec are obtained for the B and C elevators as well.

Finally, the least average weighted value EMIN among the values for the three elevators is obtained from an equation EMIN = min(EA, E5, Ec) . . . . . (3) In this way, the elevator corresponding to the value EMIN is determined to be the service elevator with respect to the call at the i-th floor, and this is displayed in the display at that floor.

The calculation as mentioned above will now be described with reference to the flow charts of Figures 5, 6 and 7.

When the calculation routine with respect to the A elevator is started, in a step 51 as shown in Figure 5, a step 52 is then executed, in which initial data are stored in the memory of the microcomputer 9. Then, after a REPEAT step 53, a step 54 is executed, in which the status of all elevators including data about and other than the group control, positions of elevators, directions of travel of elevators, state of doors, etc. is written into the elevator status buffers 3A, 38 . . ., 3H in the respective elevator operation control apparatus 2A, 28 .

2H. Then, in a step 55, whether there is a new down call made at the uppermost floor is checked. If an answer YES yields, a step 56 is executed, in which an elevator which responds to the call is selected. If an answer NO yields in the step 55, a step 57 is executed.

Figure 6 shows a flow chart of the details of the responding elevator selection routine as the step 56 between Y1 and Y2 in Figure 5. In the first place, a step 61 is executed, in which estimated waiting periods TjK at floors where new calls are made, at floors at which calls have already been made and at floors to which the elevator is destined by calls made inside it are calculated, and then a step 62 is executed. Figure 7 shows a flow chart of the step 62 between S1 and S2 in Figure 6. In the first place, a step 71 is executed, in which a reference nmerical value data B determined in the reference value determining circuit 14 shown in Figure 2 is written in the input register 13 in the microcomputer 9. Then, in a step 72, the reference addresses in a function table shown below are found by calculation.

FUNCTION TABLE 1 Address Content Address Content Ao 95 31 111 15 96 30 112 14 97 29 113 13 98 28 114 12 99 27 115 11 100 26 116 12 101 25 117 12 102 24 118 13 103 23 119 13 104 22 120 14 105 21 121 14 106 20 122 15 107 19 108 18 Further address 109 17 being omitted 110 16 Using the function table, the reference addresses A are obtained by the following equation: A = T + A0 + 8 (4), where Tj is the estimated waiting period which is given as an integral value, dropping the decimal fraction, Ao is the start address in the function table, i.e. address 95, and B is "5" (= "0101") in the embodiment of Figure 2 because the switches SWlo and SW12 are closed while all the other switches are open.If the estimated waiting period calculated with respect to a call made outside the elevators is 16 sec., the reference address A is: A = 16 + 95 + 5 = 116.

Thereafter, a step 73 is executed, in which data of the weighted value f(Tj) = 12 corresponding to the address 116 mentioned above is read out using the aforementioned function table. This reading of the weighted value f(Tj) is executed with respect to all the calls which are assigned to the A elevator according to the function table. Then, a step 63 in Figure 6 is executed, in which the average EA of the weighted values for the A elevator is calculated according to the equation (2). When the average of the weighted values for the A elevator is calculated in the above way, a step 64 is executed, in which whether the average value for every elevator has been calculated is checked.If the answer is that the average value has been calculated only for the A elevator, the routine returns to the step 61 for calculating the average value for the B and C elevators through the sequence as described above. When the calculation for all the elevators is ended, a step 65 is executed, in which the elevator corresponding to the least average value EMIN among the average values for the individual elevators is selected according to the equation (3) mentioned above. When the responding elevator selecting routine as described above is ended, a step 57 shown in Figure 5 is executed. Since in this stage the search for all the floors has not yet been ended, the step 57 is followed by the step 55 again to check whether there is any down call made this time at the uppermost but no floor, and then the steps 56 and 57 and again the step 55.When the search for all the floors has been ended in the above way, an answer YES is yielded in the step 57, and the routine returns to the REPEAT step 53. Afterwards, the routine described above is repeated to select elevators responding to subsequently generated calls.

Now, a specific example of the operation described above will now be described with reference to Figure 3.

In this example, the car of the A elevator is in the course of the up travel and at the second floor, the car of the B elevator is in the course of the up travel and at the fourth floor, and the car of the C elevator is in the course of the down travel and at the seventh floor. For the A elevator, an up call g at the third floor is assigned, and also there is an inside-elevator call 0 to the eighth floor For the B elevator, up calls A at the sixth, eighth and nineth floors are assigned, and there is an inside-elevator call r, to the tenth floor. For the C elevator, down calls V to the fourth and second floors are assigned, and there is an inside-elevator call 0 to the first floor.Now, the operation of selecting the elevator, to which an up call A newly made at the fifth floor is assigned, will be described.

It is assumed that every elevator stays at a floor for 10 seconds whenever it stops and that it takes every elevator 2 seconds to move from one floor up or down to the immediately next floor. Also for simplifying the calculation it is assumed that no time elapses between the time a call is made and the time the elevator responds to the call.

If the new call made at the fifth floor as mentioned above is assigned to the A elevator, the estimated waiting period is, from the equation (1), TA5U = 2 sec. x 3 + 10 sec. = 16 sec . . . . . (5) Like the equation (5), the estimated waiting periods in case when the new call made at the fifth floor is assigned to the A, Band C elevators and also with respect to the already made calls are calculated. The results are listed in Table 2 below.

TABLE 2 A elevator B elevator C elevator T89u = 40 44 TC4D = 6 20 TA3U= 2 24 TB8U = 28 13 TC2D = 20 14 TA5U= 16 12 TB6U= 14 12 TB5U = 2 24 TC5U = 50 72 In Table 2, the weighted values for the respective estimated waiting periods are listed in the right hand column for each elevator. These weighted values can be obtained through calculation using the function table of Table 1 mentioned above, or they can be read from the function graph of Figure 4.

From Table 2 and also on the basis of the equation (2), the average weighted values for the elevators A, B and C are given as: EA =?(24 + 12) = 18.0 ..... . . . . (6) E5 =41(44+13+12+24) =23.2 .....(7) and Ec=-31(20+ 14 + 72) = 35.3 .... (8) 3 From these average weighted values EA, E5 and Ec and also on the basis of the equation (3), it is shown that EA = 18 is the minimum as expressed by an equation EMIN = min (18.0, 23.2,35.3) = 18.0 ... . . (9) On the basis of the equation (9), the up call newly made at the fifth floor is assigned to the A elevator.

The advantage of the invention will be apparent if compared with the result obtained by the prior art method. In the prior art method, when a call is made at a floor, the elevator nearer to the floor than any other elevator is made to respond to the call. In the method of this invention, as understood from Table 2, the elevator B is selected because the estimated waiting period with it is shortest as given by the following equation: EMIN = min(TA5U, TB5U, TC5U) = min(16,2,50) .... . . . . (1O) According to this prior art method, the elevator B is deemed to make a stop at the fifth floor, so that the estimated waiting periods with respect to the up calls at the sixth, eighth and nineth floors and inside-elevator call to the tenth floor are each increased by 10 sec. Thus it quite probable that extraordinarily long waiting periods result with respect to calls.In contrast, with the elevator group control method according to the invention the up call at the fifth floor is assigned to the elevator A, and the waiting periods are reduced and become less different.

In the above embodiment, the function shown in Figure 4 for converting the estimated waiting period Tj into a corresponding weighted value f(Tj) is by no means limitative, and any other function may be used as well so long as it satisfies the following conditions: (1) There is a minimum weighted value corresponding to a reference estimated waiting value. The reference waiting period is not zero.

(2) With increase in the estimated waiting period beyond a certain limit value, the slope of the function is suddenly increased to make the assignment to the car harder.

The minimum value B provided by the reference value determining circuit 14 shown in Figure 2 may be varied depending upon the trafic congestion. For example, it is possible to set B = 15 for a leisure time zone, B = 5 for the normal time zone and B = 0 for the lunch time zone.

While the above description of the operation of the embodiment of the invention in connection with the equation (2) for deriving the average weighted value EA for the A elevator and also with the routine of selecting the responding elevator has been based upon the calls only for the sake of simplicity of description, a similar routine applies to the selection based upon the inside-elevator calls, and actually the responding elevator is determined through a selection routine which is based upon calls both inside and outside the elevators.

Claims (3)

1. A method for controlling a group of elevators, which selects an elevator to respond to a new call made at a floor, using a weighted equation, said method comprising: calculating, with respect to each elevator, the waiting periods at the floors where new calls have just been made, the waiting periods at the floors where calls have long been made and the waiting periods at the floors to which the elevator is destined by calls made therein; converting the waiting periods thus calculated with respect to each elevator into weighted values according to a function having a minimum value corresponding to a reference estimated waiting period; calculating the average of the weighted values for each elevator; and selecting the elevator whose average weighted value is less than that of any other elevator.

2. A method according to claim 1, wherein said function consists of a first function having a negative slope so that the weighted values increase to make it harder to assign an elevator as the estimated waiting period becomes shorter as long as the estimated waiting period is less than said reference estimated waiting periods, a second function having a positive slope so that the weighted values decrease to make it easy to assign the elevator as the estimated waiting period becomes shorter as long as the estimated waiting period remains within a range above said reference estimated waiting periods, and a third function having a steep positive slope so that the weighted values sharply increase to make it much harder to assign the elevator as the estimated waiting period becomes longer beyond said range.

3. A method of elevator group control, substantially as hereinbefore described with reference to Examples.