Shortly before an elevator arrives at a floor, a hall fixture (a gong, or hall lantern, or both, or any device for notifying a passenger that an elevator is on its way to serve him) can be energized to show prospective passengers which elevator in a group will respond. When an elevator arrives at the floor the doors open and remain open while passengers enter, and then they close. These three steps take time: the door opening time, the time the doors remain open (door dwell time), and the door closing time. The door opening time is the time for an opening elevator door to move from a position in which the doors are fully closed and a door fully closed switch is contacted, to a position at which the doors are fully open and a door fully open switch is contacted. The door closing time is the time for a closing elevator door to move from a position in which the door is fully open and a door fully open switch is contacted, to a position in which the door is fully closed and the door fully closed switch is contacted. Whereas the majority of passengers go to the elevator quickly, some, such as the aged or physically challenged, do so more slowly. It takes these physically challenged people longer to get to the elevator once they learn which elevator in the group will respond to the hall call. The problem is how to give these exceptional passengers an exceptionally long time to get to the elevator and enter it.
Since the issue is time, the solution to the above-stated problem would seem to lie in lengthening one of the three time periods. One way to do this is to determine an average amount of time required for one of these physically challenged passengers to get to the elevator and enter it, and then lengthen the door dwell time accordingly. Unfortunately, holding the doors open for a long time holds up the elevator service not only for passengers at the floor where the physically challenged person registered the hall call but also for passengers at floors with later hall calls. For example, a five-second longer door dwell time for an elevator traveling up with hall calls at floors 5, 6, 7, 8, and 10 will take an extra 5 seconds to get to floor 6, an extra 10 seconds to get to floor 7, an extra 15 seconds to get to floor 8, and so on.
A second way would be to announce earlier which elevator will take the hall call. An elevator commits to a given hall call when it begins to decelerate to stop at the floor registering the hall call. The point at which the elevator commits to answer a hall call is the stop control point (SCP). The distance of the SCP from a registered hall call varies and is dependent upon factors including the speed of the elevator, its deceleration rate, and its position with respect to the floor. At the SCP, the elevator starts to decelerate.
In elevator dispatching systems, such as relative system response (RSR) dispatching disclosed in U.S. Pat. No. 4,363,381, the system preliminarily assigns an elevator to respond to a hall call at the time the hall call is registered. However, thereafter the RSR system can reassign a different elevator to respond to the hall call if the subsequent assignment will provide faster response or improved system performance. The reassignment process takes place in a computer in the elevator controller and is transparent to the user. In order to improve RSR dispatching efficiency, the decision regarding possible reassignment occurs often, e.g., every second. This continual reassignment process occurs until the SCP, at which point the hall call assignment is fixed with respect to a certain elevator. The SCP is the last possible moment at which the assignment may be fixed. If an elevator receives a fixed assignment beyond the SCP, the car will not have time to slow down to the floor of the hall call. As soon as the elevator assignment is fixed, the hall fixture is energized.
What this second solution gives with one hand it takes away with the other because energizing the hall fixture before the SCP requires fixing the assignment before, the SCP, confounding the purpose of fixing the assignment simultaneously with the SCP, which purpose is to reassign until the last possible moment when the assignment must be fixed.