Last time, we have already introduced the braking and gearing systems of a China Passenger Lift, this time, we will discuss the control system.
As a matter of fact, elevator control systems are probably the only part of the passenger elevator that has seen major improvements over the last century. It was not that long ago that every passenger elevator had an operator who controlled the elevator, starting and stopping the elevator manually, based on the requests of those riding the elevator and signals from those waiting for the elevator.
However, as time went by, this system was replaced by a set of buttons inside the passenger elevator, with a single button for each floor, and two buttons used for calling the elevator - an up button and a down button. This method enables the passenger elevator to determine whether or not the direction in which the elevator is traveling is relevant to the person waiting to board.
With the advent of very tall buildings, passenger elevators were assigned specific ranges of floors on which to operate. This allows an express elevator to 'jump' 50 floors or more before making frequent stops. This too improved efficiency.
However, drawbacks remain. If, for example, a person on the 23rd floor of a building is waiting for an elevator to take him to the 40th floor, he has no way of making this known to the elevator other that by pushing the up button. The next ascending elevator will stop regardless of the number of stops it must make between the 23rd and 40th floors.
Nonetheless, an efficient control system will enable the person waiting for a passenger elevator to signal his destination before the elevator arrives at his floor. A computerized system determines the most efficient car for him to board. In our example, the first car to pass the 23rd floor may be stopping 6 times between the 23rd and 40th floors. However, a car that will arrive only a few seconds later carrying a passenger who wants to alight from the elevator on the 23rd floor anyway, and will only make 2 stops before it reaches the 40th floor. By causing the potential rider to wait a few seconds before boarding a passenger elevator, not only can a significant amount of energy be saved, but the rider will actually reach his destination faster than he would have if he had boarded the first elevator ascending past the 23rd floor.
All in all, replacement of the control system should not be a major construction project, and may actually result in the best improvement of passenger elevator efficiency. What is more, current technology can make passenger elevators considerably more efficient than they currently are, resulting in significant savings for owners and operators of tall buildings.