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(11) | EP 0 452 130 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Controlling door dwell time |
| (57) The present invention is directed to controlling the door dwell time of an elevator
car door based on traffic conditions. In the present invention, a door dwell sensor
emits radiation and senses reflected radiation in the presence of a potential passenger.
As an elevator car arrives at a floor, its door is preferably initially held open
a first predetermined time period (300). Thereafter, if boarding traffic is detected,
the door is further held open a second predetermined time period (306). If the total
amount of time that the elevator car door has been open (310) is less than a predetermined
maximum amount of time, the present invention again detects for the presence of boarding
traffic. If boarding traffic is detected, the door is again held open a second predetermined
time period. This process continues until either boarding traffic is not detected,
or the door has remained open for the predetermined maximum amount of time. When boarding
traffic is not detected, or when the door has remained open for the predetermined
maximum amount of time, the elevator car door will begin to close (312). The predetermined
maximum amount of time can be a fixed value, a variable based on the reason the elevator
car stopped at the floor, or a variable based on a predicted door dwell time, which
takes into account predicted number of boarding and deboarding passengers at the floor. |
[0001] The present invention is directed to controlling the operation of an elevator car door. More particularly, the present invention is directed to controlling door dwell time of an elevator car door.
[0002] As used herein, door dwell time means the time between when the door of an elevator car is commanded to open and when the door is commanded to close.
[0003] In a building having a plurality of floors, each floor typically has a set of buttons located in the hallway at or near the elevators. These buttons, commonly referred to as hall call buttons, enable users to request elevator car service in a predetermined direction, i.e., up and/or down. Additionally, the interior of an elevator car is generally equipped with a plurality of buttons, commonly referred to as car call buttons, which enable users to request service to specific floors.
[0004] In simplified terms, an elevator control system, also referred to in the art as an elevator dispatching system, monitors the status of the hall call buttons at the floors and car call buttons in the elevator cars, assigning elevator cars to the floors in response to hall calls registered at the floors and/or car calls registered in the elevator car.
[0005] In order to increase the efficiency of passenger traffic flow through the elevator car, elevator control systems are commonly provided with an advanced door opening feature. In this feature, the elevator control system commands the elevator car door to begin opening when the elevator car commits to a floor, i.e., when it begins to decelerate in order to stop at the floor. In this way, the elevator car door is almost completely open by the time the elevator car stops at the floor.
[0006] In prior art systems, the door remains open for a fixed period of time, based on whether the elevator car is responding to a car call or a hall call. Typically, it is assumed that only one passenger will deboard the elevator car in response to a car call and that only one passenger will board in response to a hall call. Additionally, it is assumed that it takes less time to deboard an elevator car than to board. Based on these assumptions, the fixed period of time is typically about 4 seconds for a car call and typically about 6 seconds for a hall call.
[0007] At the end of this fixed period of time, the elevator control system commands the elevator car door to begin closing. Door reversal occurs where passenger transfer is not fully accomplished at the time the door begins closing. Door reversal is commonly initiated either when a passenger breaks a beam located at the entrance of the elevator car, when the edge of the door contacts a passenger, or when the edge of the door is held by a passenger.
[0008] It is not uncommon for door reversal to occur more than once in relatively heavy traffic conditions. The resulting interference of the closing door on a passenger can further delay passenger transfer, thereby exacerbating the situation.
[0009] Additionally, there are situations where no passenger is waiting to board the elevator car, despite there being a registered hall call at the floor. For example, a passenger registered a hall call in both directions when the intent is to go only in one direction, either through accident or impatience. Also, a passenger registered a hall call but subsequently changed their mind about service, either by taking the stairs or by being preempted by another matter.
[0010] The fixed door dwell time is either too short, e.g., in relatively heavy traffic conditions, or is too long, e.g., where no passenger is waiting to board the elevator car.
[0011] Accordingly, it is an object of the present invention to control the door dwell time of an elevator car door in a manner to increase the efficiency of an elevator control system.
[0012] According to the invention, there is provided a method of controlling the operation of an elevator car door, said method comprising the steps of:
(a) opening the elevator car door;
(b) maintaining the door in the open position for a predetermined time period;
(c) detecting for the presence of passenger traffic flow at the end of the predetermined time period; and
(d) repeating steps (b) through (d) if passenger traffic flow is detected; otherwise,
(e) begin closing the door of the elevator car.
[0013] Thus, the present invention is directed to controlling the door dwell time of an elevator car door based on traffic conditions. In the present invention, a door dwell sensor is preferably mounted on a door frame of an elevator car. The sensor emits radiation and senses reflected radiation in the presence of a potential passenger.
[0014] The sensor preferably determines in what direction the passenger is moving based on the time between reflected radiation signals. For example, where the time between reflected signals is decreasing, it is indicative of a passenger moving towards the elevator car. Where the time between reflected signals is increasing, it is indicative of a passenger moving away from the elevator car.
[0015] As an elevator car arrives at a floor, its door is opened to allow passengers to board and deboard. The door is preferably initially held open a first predetermined time period to allow passengers to exit and to allow passengers who wish to board a chance to move towards the elevator car. Thereafter, the present invention detects for boarding traffic, based on passenger movement toward the elevator car. If no boarding traffic is detected, the door of the elevator car begins to close.
[0016] If boarding traffic is detected, the door is further held open a second predetermined time period. If the total amount of time that the elevator car door has been open is less than a predetermined maximum amount of time, the present invention again detects for the presence of boarding traffic. If boarding traffic is detected, the door is again held open a second predetermined time period. This process continues until either boarding traffic is not detected, or the door has remained open for at least the predetermined maximum amount of time. When boarding traffic is not detected, or when the door has remained open for at least the predetermined maximum amount of time, the elevator car door will begin to close.
[0017] The predetermined maximum amount of time can be a fixed value or variable, based on the reason the elevator car stopped at the floor. Alternatively, the predetermined maximum amount of time can be based on a predicted door dwell time, which takes into account the number of passengers that are predicted to be boarding and deboarding the elevator car at the floor, as well as the status of the particular elevator car.
[0018] The present invention, therefore, preferably uses information received from the door dwell sensor to control the door dwell time of the elevator car door based on traffic conditions. For example, when no boarding traffic is detected, the door is held open a minimum door dwell time. As boarding traffic volume increases, the door dwell time is also increased. Thus, the efficiency of the elevator control system is improved.
[0019] An embodiment of the invention will now be described by way of example only, and with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 2 illustrates a preferred embodiment of the sensor to sense the presence of passenger traffic flow through the elevator car door.
[0022] Figure 3 illustrates a preferred embodiment of a process for controlling the door dwell time of an elevator car door based on traffic conditions.
[0023] Elevator control systems are well known in the art. For example, US 4,363,381 to Bittar discloses an elevator control system employing a group controller connecting individual car controllers. Additionally, EP 0,239,662 discloses an elevator control system employing individual car controllers communicating via a bi-directional ring communication system. Reference is made to these publications for specific details.
[0024] An exemplary elevator control system employing individual car controllers communicating via a bi-directional ring communication system is shown with reference to Figure 1. It is to be understood, however, that the present invention can be used with any other elevator control system.
[0025] Turning now to Figure 1, an exemplary elevator control system is shown, wherein each elevator car has operational control subsystem (OCSS) 101 which communicates to every other OCSS in a ring communication system via lines 102, 103. It is to be understood that each OCSS has various circuitry connected thereto. However, for the sake of simplicity, the circuitry associated with only one OCSS will be described.
[0026] Hall call buttons and their associated lights and circuitry (not shown) are connected to an OCSS via remote station 104, remote serial communication link 105 and switch-over module 106. Car buttons and their associated lights and circuitry (not shown) are connected to an OCSS via remote station 107 and remote serial communication link 108. Hall lanterns, indicating e.g. the direction of travel of the car which is to stop and/or which set of doors will be opened to accommodate the elevator car which is to stop, and their associated lights and circuitry (not shown) are connected to an OCSS via remote station 109 and remote serial communication link 110.
[0027] The operation of the elevator car door is controlled by door control subsystem (DCSS) 111. Optionally, a sensor (not shown) can be mounted on the elevator car door frame to sense passenger traffic flow through the elevator, thereby controlling door dwell time via the DCSS based on the presence of passenger traffic flow.
[0028] The movement of the elevator car is controlled by motion control subsystem (MCSS) 112, which operates in conjunction with drive and brake subsystem (DBSS) 112A. Dispatching is determined and executed by the OCSS under the supervisory control of advanced dispatching subsystem (ADSS) 113, which can be housed, e.g., in computer 115, communicating via information control subsystem (ICSS) 114.
[0029] In the preferred embodiment, the DCSS also determines the load of the elevator car, the load being converted into user boarding and/or deboarding counts by the MCSS. This information can be sent to the ADSS for recordation and prediction of traffic flow in order to increase the efficiency of elevator service. Alternatively, user boarding and/or deboarding counts can be determined by a people sensing/counting arrangement as shown, e.g., in US 4,799,243.
[0030] Turning now to Figure 2, a preferred embodiment of a door dwell sensor to sense the presence of passenger traffic flow through the elevator car door is illustrated. Door dwell sensor 200 is preferably mounted on door frame 202 of elevator car 204, thus requiring only one sensor per elevator car. Alternatively, however, a sensor can be provided at each floor for each elevator.
[0031] The sensor can be based on infrared or other radiation technology, e.g., ultrasound, which emits radiation and senses reflected radiation in the presence of potential passenger 206. The sensor preferably emits radiation outwardly towards the area where a potential passenger would wait for an elevator car after registering a hall call. The sensor preferably determines in what direction the passenger is moving based on the time between reflected radiation signals. For example, where the time between reflected signals is decreasing, it is indicative of a passenger moving towards the elevator car. Where the time between reflected signals is increasing, it is indicative of a passenger moving away from the elevator car.
[0032] The elevator control system preferably receives information regarding passenger traffic flow on a periodic basis, e.g., every 100 milliseconds. In the preferred embodiment, when the sensor detects the presence of traffic, a signal is sent to the OCSS for controlling the operation of doors 208 of the elevator car via the DCSS.
[0033] Turning now to Figure 3, a preferred embodiment for controlling the door dwell time of an elevator car door based on traffic conditions is illustrated. The present invention uses information received from the door dwell sensor (Figure 2) to control the door dwell time of the elevator car door based on traffic conditions. For example, when no boarding traffic is detected, the door is held open a minimum door dwell time. As boarding traffic volume increases, the door dwell time is also increased. Thus, the efficiency of the elevator control system is improved.
[0034] At step 300, the elevator control system commands the door of the elevator car to open, either when an elevator car commits to a floor, i.e., when it begins to decelerate in order to stop at the floor, or when the elevator car has stopped at the floor. In the preferred embodiment, the elevator car door is initially held open for a time period of △t₁ to allow passengers to exit and to allow passengers who wish to board a chance to move toward the elevator car.
[0035] The value of △t₁ is preferably a fixed value, e.g., 1 second. Alternatively, the value of △t₁ can be variable, based on the reason the elevator car stopped at the floor. For example, if the elevator stopped in response to a car call, △t₁ can be, e.g., 3 seconds. If the elevator stopped in response to a hall call, △t₁ can be, e.g., 1 second. If the elevator stopped in response to a coincident call, defined herein as when the elevator car is responding to both a car call and a hall call at same floor, △t₁ can be, e.g., 3 seconds.
[0036] At step 302, the value representing the total time the elevator car door has been open, tTotal, is initialized. In the preferred embodiment, the value of tTotal is initialized to the value of △t₁.
[0037] At step 304, the system detects for the presence of boarding traffic. In the preferred embodiment, if the system detects passenger movement toward the elevator car, it will assume that those moving toward the elevator car do so with the intention of boarding.
[0038] Where boarding traffic is detected, the door is further held open for a time period of △t₂ at step 306. The value of △t₂ is preferably a fixed value, e.g., 1 second. At the end of △t₂, the system at step 308 updates tTotal, the total time the elevator car door has been open. At step 310, if tTotal is less than a predetermined maximum amount of time, tMax, steps 304 through 310 are repeated.
[0039] The value of tMax represents the desired door dwell time, defined herein as the time between when the door of an elevator car is commanded to open and when the door is commanded to close. The value of tMax can be a fixed value, e.g., 10 seconds. Alternatively, the value of tMax can be variable, based on the reason the elevator car stopped at the floor. For example, if the elevator stopped in response to a car call, tMax can be, e.g., 4 seconds. If the elevator stopped in response to a hall call, tMax can be, e.g., 6 seconds. If the elevator stopped in response to a coincident call, tMax can be, e.g., 8 seconds.
[0040] Alternatively, the value of tMax can be determined based on a predicted door dwell time, which takes into account the number of passengers that are predicted to be boarding and deboarding the elevator car at the floor, as well as the status of the particular elevator car.
[0041] As is known in the art, historical information regarding the number of passengers boarding and deboarding each elevator car, on a per floor basis, for predetermined time intervals, e.g., 1 minute, can be obtained over the course of several days. This information can then be used to determine historical boarding and deboarding rates, and to predict the number of passengers which will be boarding and deboarding at the floor where the elevator car will stop.
[0042] A predicted door dwell time can be determined based on the following empirically derived equation:
wherein:
x represents the total number of predicted passengers transferring;
r represents the spare capacity after passenger deboarding and before boarding (e.g., total capacity - current load + predicted to deboard);
s represents about 1/4 the car capacity; and
a, b, c represent constants which depend upon car size and transfer mode.
Based on a typical transfer mode where entry of boarding passengers follows exit of deboarding passengers, a is 1.08, b is 2.36 and c is 0.62.
[0043] For example, assume a coincident call stop in which 3 passengers are predicted to board and 2 passengers are predicted to deboard, and where the load sensors indicate 8 passengers are aboard the elevator car just prior to it stopping at the floor. Additionally, assume a 4000 lb. elevator car with a 28 passenger capacity at 142.85 lbs. per passenger. Thus, x is 5, r is 22 and s is 7.
[0044] Thus, the predicted door dwell time is:
which is equal to 6.25 seconds. In the preferred embodiment, if the value of the predicted door dwell time is greater than a predetermined maximum value, e.g., 10 seconds, the value of tMax is set to the predetermined value. Alternatively, the value of tMax can be set to the value of the predicted door dwell time.
When determining the predicted door dwell time, if a car call is not registered in the elevator car, the number of passengers deboarding is preferably set equal to zero, regardless of the predicted value. Similarly, if a hall call is not registered at the floor, the number of passengers boarding is preferably set equal to zero, regardless of the predicted value. Additionally, the value of r is preferably no greater than the elevator car's spare capacity, regardless of the predicted value.
[0045] If boarding traffic is not detected at step 304, or if tTotal is greater than or equal to tMax at step 310, the elevator control system commands the door of the elevator car to close at step 312. In the preferred embodiment, the system commands the elevator car door to close if the door has been open at least the predetermined maximum amount of time tMax, despite further detection of boarding traffic. In this way, the elevator door will begin to close in spite of a faulty sensor or traffic which is moving toward the elevator car merely as a coincidence and not with the intention of boarding. However, the door could be commanded to close only when boarding traffic is no longer detected.
[0046] The elevator door will reopen if passengers are still boarding after the elevator door begins to close, either due to the edge of the door contacting a passenger, due to the edge of the door being held by a passenger or due to the "open door" button located inside the elevator car being depressed.
[0047] As discussed above with reference to step 302, the value of tTotal is preferably initialized to the value of △t₁, ensuring an accurate value for the total time determined at step 308. Alternatively, the value of tTotal can be initialized to zero, provided the value of tMax is adjusted to ensure the desired door dwell time.
[0048] The present invention, therefore, controls the door dwell time of an elevator car door based on traffic conditions.
[0049] It is to be understood that the ranges and the preferred values of the quantities specified above are empirical in nature and are preferably a function of the specific building configuration and its traffic patterns. As used herein, building configuration means the physical attributes of the building which impact traffic flow therethrough, including but not limited to number of floors, number of elevators, elevator speed, location of express zone(s), location of lobby level and/or parking level(s), total building population, and distribution of the population per floor.
[0050] Although illustrative embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments. Various changes or modifications may be effected therein by one skilled in the art without departing from the scope of the invention.
1. A method of controlling the operation of an elevator car door, said method comprising
the steps of:
(a) opening the elevator car door;
(b) maintaining the door in the open position for a predetermined time period;
(c) detecting for the presence of passenger traffic flow at the end of the predetermined time period; and
(d) repeating steps (b) through (d) if passenger traffic flow is detected; otherwise,
(e) begin closing the door of the elevator car.
2. The method of claim 1, wherein the predetermined time period is about one second.
3. The method of claim 1, wherein the value of the first predetermined time period after
the car stops is based on whether the elevator car stopped in response to a car call,
a hall call or a coincident call.
4. The method of claim 1, comprising the steps of:
(a) opening the elevator car door;
(b) maintaining the door in the open position for a first predetermined time period;
(c) detecting for the presence of passenger traffic flow;
(d) maintaining the door in the open position for a second predetermined time period if passenger traffic flow is detected;
(e) repeating steps (c) through (e) if passenger traffic flow is detected and if the door has been maintained in the open position for less than a predetermined maximum time period;
(f) otherwise, begin closing the door of the elevator car.
5. The method of claim 4, wherein the first predetermined time period is about one second.
6. The method of claim 4, wherein the value of the first predetermined time period is
based on whether the elevator car stopped in response to a car call, a hall call or
a coincident call.
7. The method of claim 4, 5 or 6 wherein the second predetermined time period is about
1 second.
8. The method of claim 4, 5, 6 or 7 wherein the predetermined maximum time period is
about 10 seconds.
9. The method of claim 4, 5, 6 or 7 wherein the value of the predetermined maximum time
period is based on whether the elevator car stopped in response to a car call, a hall
call or a coincident call.
10. The method of claim 4, 5, 6 or 7 wherein the predetermined maximum time period is
based on a predicted door dwell time, the predicted door dwell time being based on
a predicted number of passengers to be boarding and deboarding the elevator car.
11. The method of claim 10, further comprising the steps of:
obtaining historical information of passenger boarding rates at the floor;
predicting, based on said historical boarding information, the number of passengers which will board the elevator car at the floor;
obtaining historical information of passenger deboarding rates at the floor;
predicting, based on said historical deboarding information, the number of passengers which will deboard the elevator car at the floor;
determining the predicted door dwell time, based on the predicted number of passengers which will board and deboard the elevator car at the floor; and
assigning a value to the predetermined maximum time period based on the value of the predicted door dwell time.
obtaining historical information of passenger boarding rates at the floor;
predicting, based on said historical boarding information, the number of passengers which will board the elevator car at the floor;
obtaining historical information of passenger deboarding rates at the floor;
predicting, based on said historical deboarding information, the number of passengers which will deboard the elevator car at the floor;
determining the predicted door dwell time, based on the predicted number of passengers which will board and deboard the elevator car at the floor; and
assigning a value to the predetermined maximum time period based on the value of the predicted door dwell time.
12. The method of claim 11, wherein the step of determining the predicted door dwell time
further comprises the steps of:
determining the passenger load of the elevator car before the elevator car arrives at the floor;
predicting spare capacity of the elevator car, based on a predetermined total elevator car capacity and the determined passenger load; and
determining the predicted door dwell time, based on said predicted number of deboarding passengers which will board and deboard the elevator car at the floor, the predicted spare capacity and the predetermined total car capacity.
determining the passenger load of the elevator car before the elevator car arrives at the floor;
predicting spare capacity of the elevator car, based on a predetermined total elevator car capacity and the determined passenger load; and
determining the predicted door dwell time, based on said predicted number of deboarding passengers which will board and deboard the elevator car at the floor, the predicted spare capacity and the predetermined total car capacity.