20-10-2010, 04:19 PM
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Introduction
An elevator is a device designed as a convenience appliance that has evolved to become an unavoidable feature of modern day urban life. The Oxford Dictionary [2] defines an elevator as, “A machine that carries people or goods up and down to different levels in a building or mine”. While a standalone elevator is a simple electro-mechanical device, an elevator system may consist of multiple standalone elevator units whose operations are controlled and coordinated by a master controller. Such controllers are designed to operate with maximum efficiency in terms of service as well as resource utilization. This chapter details the design of a dual elevator controller.
2.2 Basic Principle – Dual Elevator Controller
Dual elevator controller is an elementary system consisting of two elevator cars serving two floors. Each of the elevator cars has a pair of control buttons (up / down) for moving the elevator up and down. Each of the floors also has call buttons to call for the service of the elevator system. The following principles have been applied during the design of the dual elevator controller:
• The floors are defined as ground floor (gndFlr) and first floor (fstFlr).
• The elevator cars are designated as elevator-A (elvtrA) and elevator-B (elvtrB).
• Elevator-A gives priority to ground floor and elevator-B gives priority to first floor.
• A floor call is serviced using the nearest available elevator.
• Upon arrival at a floor, the doors open immediately.
• Doors remain open for approximately 20 seconds, before closure.
• If an obstruction is detected when door is about to close, it remains open
• Each elevator car is treated as a sub-system controlled by the controller.
• Elevator Up / Down buttons are connected to individual elevator units.
• Elevator units depend on floor sensor inputs to determine the current status.
• Each door unit is treated as a sub-system controlled by the respective elevator car.
• Timing and obstruction detection systems act as slave systems to the door units.
• Floor call buttons are connected to the elevator controller.