1. Technical Field
The present invention is directed to elevator dispatching. More particularly, the present invention is directed to assigning an elevator car to a floor in response to a hall call registered at the floor, based on a series of bonuses and penalties and remaining response time.
As used herein, remaining response time means an estimation of the amount of time required for an elevator car to reach the floor at which the hall call is registered, given the car calls and hall calls to which the elevator car is committed.
2. Background Information
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.
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 call and/or car call registration.
As used herein, relative system response, commonly abbreviated RSR, means an elevator dispatching system which employs a series of bonuses and/or penalties to determine which elevator car to assign to a registered hall call. RSR dispatching systems are well known in the art. For example, U.S. Pat. No. 4,363,381 issued to Bittar, entitled Relative System Response Elevator Call Assignments, U.S. Pat. No. 4,815,568 to Bittar, entitled Weighted Relative System Response Elevator Car Assignment System With Variable Bonuses And Penalties, U.S. Pat. No. 4,782,921 to MacDonald et al., entitled Coincident Call Optimization In An Elevator Dispatching System, U.S. Pat. No. 4,790,412 to MacDonald et al., entitled Anti-Bunching Method For Dispatching Elevator Cars, and U.S. Pat. No. 4,793,443 to MacDonald et al., entitled Dynamic Assignment Switching In The Dispatching Of Elevator Cars, herein incorporated by reference.
In RSR dispatching systems, each elevator car has associated therewith a value for each one of the bonuses and penalties, the values being dependent upon the elevator status, relative to the registered hall call. An RSR value for each elevator car is determined by cumulating the bonuses and penalties for each elevator car, and the elevator car having the most favorable RSR value is assigned to respond to the registered hall call.
Certain penalties of the Bittar systems combine to yield an estimate of the response time of each elevator car to respond to the registered hall call. Some of the various penalties used in the Bittar systems include a run time penalty (RTP) based on the time required for an elevator car to travel between hall and car stops assigned thereto; a travel-through express zone penalty (TRE) based on the time required to travel through the express zone; and a hall stop penalty (HSP) and a car stop penalty (CSP) based on the time delay incurred for each hall stop and car stop, respectively, assigned to the elevator car.
The bonuses of the Bittar systems offset the penalties, thereby favoring an elevator car based on certain conditions. Examples of various bonuses used in the Bittar systems include a coincident car call bonus (CCB) which favors an elevator car having a car call coincident with the floor registering the hall call; a contiguous stop bonus (CSB) which favors an elevator car having a commitment at a floor contiguous with the floor registering the hall call; and a previously-assigned bonus (PAB) which favors the elevator car previously assigned to the hall call.
In the Bittar systems, the RSR value is determined by subtracting the bonuses and adding the penalties, and the elevator car having the lowest RSR value is the most favorable. Similarly, in the MacDonald systems, the RSR value is determined by substracting bonuses from an estimated arrival time, based on items substantially similar to RTP, TRE, HSP and CSP, with the elevator car having the lowest RSR value being the most favorable. The bonuses employed by the MacDonald systems are similar to the CCB (see U.S. Pat. No. 4,782,921), the CSB (see U.S. Pat. No. 4,790,412), and the PAB (see U.S. Pat. No. 4,793,443) of the Bittar systems.
Although these systems are defined such that the lowest RSR value is most favorable, additions and subtractions can be reversed such that the highest RSR value is most favorable.
The RSR determination typically occurs either every cycle, e.g., every 250 milliseconds, or on an "as needed" basis, e.g., whenever an elevator car changes positions, responds to a hall or car call, or whenever a new hall or car call is registered. It is conceivable that the system can reassign the unanswered hall calls to a different elevator car quite often. In order to dampen what might otherwise be an erratic dispatching system, the previously assigned bonus (PAB) is included in the Bittar and MacDonald RSR systems to favor the elevator car which was previously assigned to the unanswered hall call.
The habits and customs of the elevator user dictate the value typically assigned to the previously assigned bonus (PAB). The user predominantly in Europe and the Americas wants to be informed which elevator car will be arriving in response to the hall call shortly before it arrives. Thus, the hall lantern located at or near the arriving elevator car illuminates and/or sounds shortly before the elevator car arrives. In these types of RSR systems, the Bittar systems typically assign a relatively low value to the PAB. Thus, if another elevator car can service an unanswered hall call by at least the PAB value before the assigned car, the unanswered hall call is reassigned to that other car.
The user predominantly in Japan, on the other hand, wants to be informed which elevator car will be responding to the hall call at the time of hall call registration. In this way, the user can wait at the door of the assigned elevator. In these RSR systems, commonly referred to as instantaneous car assignment systems, the elevator car having the most favorable RSR value is almost immediately assigned to the hall call, and the hall lantern located at or near the assigned elevator car illuminates and/or sounds upon assignment. In these types of RSR systems, the Bittar systems typically assign a relatively high value to the PAB, so as to maintain the integrity of the initial car assignment.
There are situations where the initial elevator car assignment, although the best when made, subsequently turns out to be less than satisfactory. For example, in response to an intervening car and/or hall call, the boarding passengers register a plurality of car calls. Additionally, the elevator car, while traveling through the lobby or while responding to an intervening car and/or hall call, gets delayed by boarding passengers who hold the door open, e.g., to wait for others or to finish a conversation with a non-boarding person. Further, an empty elevator car may be assigned a hall call moments before a boarding passenger registers a car call in the direction opposite the assigned hall call.
Due to the large value of PAB, in immediate car assignment systems any one of these situations can drastically extend the system's registration time, defined as the time between when the hall call is registered and when the elevator car is about to arrive in response thereto, as indicated by the hall lantern at or near the arriving elevator car. The maximum registration time is a conventional indicium of overall system responsiveness. In RSR systems employing instantaneous car assignment, some buildings have rather large maximum registration times.
Such large registration times are considered highly unacceptable for at least two reasons. First, a user's irritation level is a function of the amount of time spent waiting for an elevator car. Thus, the longer the wait, the more severe his or her irritation. Second, and more importantly, before the assigned elevator car can get to the floor to service the unanswered hall call, the floor may be bypassed, up-going hall call, by at least one of the other elevator cars; e.g., a car traveling in the up direction travels past a floor having an unanswered up-going hall call.
However, due to the relatively large PAB value, the initially-assigned elevator car remains assigned to the unanswered hall call, despite the fact that at least one other elevator car is bypassing the floor having the unanswered hall call. The other elevator cars do not stop because they do not get the assignment.