Design of a Dual Elevator Controller


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INTRODUCTION

An elevator or lift is a kind of transport device used to move people between building floors. Whenever a passenger presses the call button for an elevator, a computer receives the request and logs it for future reference. There are actually two sets of doors, which allow passengers safely to exit and enter the lift. One set of doors remains shut until an elevator car's presence is detected and the elevator’s computer controls the other door. Once both doors are open, passengers should leave quickly to allow new passengers to board and more calls to be answered. Elevator doors also contain motion detectors and other presence-sensing devices to keep doors from trapping passengers. Another issue want to be considered is the weight capacity. Overload in elevator will lead to accident and using the load sensor can control it.
In modern life, elevators have become an integral part of any public or commercial complex. It does not only ease the faster movement between any two floors and provide a way for movement of disabled, but has also become a status symbol.

Elevator Controller & it’s Working

Elevator controller controls the entire operation of the Dual elevator system. The proximity sensors located to sense the positions of the cars, provide the current state storing it in register. The obstruction sensors provide the status of obstruction. The elevator controller also reads the requests, if any, from any of the request positions through the flip-flops.

DESIGN OF A DUEL ELEVATOR CONTROLLER

The dual elevator controller designing in HDL has been a great challenge. The Moore model did simplify the approach, but in order to operate the system in optimized way and accept user request by the nearest elevator, highlighted the complexities involved in it. The elevator algorithm respects the constraints defined and works in alignment to the assumptions made.
The timer implementation as a part of the code remained an unresolved issue, as the coding should also have been synthesizable. The other issues that could not be addressed were to store the request and provide to the elevator at a later stage if the elevator is in busy state at that time. As the elevator system in for only two floors, the same could also be automated that once user gets into the lift, he does not need to request for the destination.
In general, the elevator controller has to control a larger group in a multi-floor building. Then, the capabilities of designing the algorithm of the designer decide the functionality of the elevator system.
The building has two elevators that move between two floors. The first floor has a single UP button and the second floor has a single DOWN button. Inside each elevator has also two buttons, UP and Down. Normally an elevator will move when instructed to do so by the control, opening the door for 20 second. After the waiting of 20 second the door might be closed. If any obstruction detected, the door will open. The input of the system includes sensors that indicate whether the elevator is at the given floor and if a passenger moving ON or OFF on the elevator is obstructing its doors.

WORKING

Now, let us consider the basic and general block diagram of dual elevator controller which is shown below.
In this general block diagram, there are two main blocks are available. One is controller and other is door operator. A sensor is connected between these two main blocks, so that if there any sensor signal goes high, the operation on both elevators 1 and 2 will be carried out.