25-08-2017, 09:32 PM
Project Report FPGA IMPLEMENTATION OF ELEVATOR CONTROL
1ELEVATOR CONTROL.doc (Size: 4.17 MB / Downloads: 59)
Abstract
The elevator control system is one of the important aspects in electronics control module in automotive application. In this project the elevator control system is designed with different conditions. First the elevator control system is implemented for multi-storage building. This implementation is based on FPGA based logic for intelligent control of elevator group system.
This proposed approach is based on algorithm which is developed to reduce the
amount of computation required by focusing only on relevant rules and ignoring those
which are irrelevant to the condition for better performance of the elevator system. Here eight inputs are considered. Here two floor elevator systems have been considered and every floor has two switches, one switch is used for up movement and another switch is used for down movement. Based on the switch pressed, the elevator can move either in upward or downward direction. Here two sensors are used in every floor. One sensor is used for detecting the elevator when elevator reaches its destination floor. Another sensor is used for opening and closing the door.
Elevators have not changed substantially in many years and are unlikely to do so in the near future. Electronic controls will continue to improve in ways that are evolutionary and not very dramatic. Control systems are being developed that will learn from past traffic patterns and use this information to predict future needs in order to reduce waiting times. Laser controls are coming into use, both to gauge car speed and distance, as well as to scan building floors for potential passengers.
Introduction
FPGA would be exactly the right way to do things if we have an elevator that could move from one floor to the next 100-1000 nanoseconds. Since that implies an elevator that's only moving between 1/3 and 1/30th the speed of light we suppose it's not totally impossible, as long as you don't mind accelerations that can reach between 2 and 200 trillion times gravity.
As long as you have an elevator that takes a few seconds between floors the sensible way to build an elevator controller out of an FPGA. In this total design using FPGA we used FSM(Finite state machine) logic to implement the Elevator Control System.
Waiting for elevator car is a major situation with this we all are familiar. When we press a button and wait for an elevator, we may have to wait for a long time, if there are too many passengers or not enough elevator car is present in particular situation. Important thing is that, how much time we wait, which depends on the dispatching strategy of the elevator car in particular time instance. Efficiencies of multiple elevators installed in an office building may increase if a central
dispatcher is used to group passengers going to the same floor to the same elevator.
Figure 1: shows the two elevator dispatching strategy. Here each elevator has a position, direction and speed. It has also set of buttons to indicate where passengers want to get off. Dispatching algorithm for elevator is generally designed primarily for the different periods that is for morning and evening rush hours.
Statement of Problem
The main objective of designing a Elevator is mentioned before itself. The main aim is to design a Elevator which works with the inputs and the state transition occurs after the inputs are satisfied.
Design Objectives
The main objective is to Design a Elevator in such a way that one has to be more sufficient of using these cars instead of going up and descending. In order to decide how it will react when the input or clock signal satisfies.
There is a "request" push-button on each floor (REQ1 and REQ2) beside the elevator door. When the elevator arrives at your floor, the doors open for a set period of time to let passengers on or off and then close automatically. Inside the elevator you press either the FLOOR2 or the FLOOR1 push-button switches. If you are on the first floor, you press the FLOOR2 push-button to go to the second floor; and if you are on the second floor, you press the FLOOR1 push-button to go to the first floor. Pressing the Open push-button inside the elevator will cause the door to reopen or stay open longer than the preset time as long as the elevator is not moving. If none of the push-button switches is activated, the elevator waits at the last floor serviced. A very slow clock signal controls both the movement of the elevator and the time that the door remains open when the elevator stops at a floor.
The state control logic consists of clock-independent latches that store a momentary closure of the push-button switches and a state machine that produces three elevator control outputs synchronized with the clock: DOOR, MOTION, and DIR (direction).
Project Assumptions and Constraints
We have designed this with FSM logic in this because its very ease to design and very much useful for real time implementation. State machines or FSM are the heart of any digital design; of course a counter is a simple form of FSM
There are two types of state machines as classified by the types of outputs generated from each. The first is the MOORE STATE MACHINE where the outputs are only a function of the present state, the second is the MEALY STATE MACHINE where one or more of the outputs are a function of the present state and one or more of the inputs.
Behavioral and RTL Description
This section contains the behavioural description of our FSM logic state diagram and explanation of the working of the each and every block in the state diagram
W1 (Wait1)
The system is in the W1 state in which the elevator is waiting on the first floor with the door open. If, after a period of time established by the clock, there is no request from the second floor and the FLOOR2 button is not pressed (DELAY), the system goes to the CL1 state in which the elevator remains waiting on the first floor with the door closed. When the system is in the W1 state and there is a request from the second floor or the FLOOR2 button is pressed (REQ2 + FLOOR2), the system bypasses the CL1 state and goes to the UP state on the next clock pulse. In the UP state, the door closes and the elevator moves upward.
CL1 (Close1)
When the system is in the CL1 state, it remains there until there is a request from the second floor or the FLOOR2 button is pressed (REQ2 + FLOOR2), which causes the system to go to the UP state. Alternatively, it remains in the CL1 state until there is a request from the first floor or the OPEN button is pressed (REQ1 + OPEN), which causes the system to return to the W1 state.
UP (Upward)
Now in this the system remains in the UP state until the ARRIVE signal is received. An ARRIVE signal is produced when the elevator reaches the second floor and activates a switch, putting the system into the W2 state.
W2 (Wait2)
In the W2 state, the elevator is waiting on the second floor with the door open. If, after a period of time established by the clock, there is no request from the first floor and the FLOOR1 button is not pressed (DELAY), the system goes to the CL2 state in which the elevator remains waiting on the second floor with the door closed. When the system is in the W2 state and there is a request from the first floor or the FLOOR1 button is pressed (REQ1 + FLOOR1), the system bypasses the CL2 state and goes to the DOWN state on the next clock pulse. In the DOWN state, the door closes and the elevator moves downward.
CL2 (Close2)
When the system is in the CL2 state, it remains there until there is a request from the first floor or the FLOOR1 button is pressed (REQ1 + FLOOR1), which causes the system to go to the DOWN state. Alternatively, it remains in the CL2 state until there is a request from the second floor or the OPEN button is pressed (REQ2 + OPEN), which causes the system to return to the W2 state.
DOWN (Downward)
Now the system remains in the DOWN state until an ARRIVE signal is received when the elevator reaches the first floor, which activates a switch and puts the system back into the W1 state.
The above mentioned are the constraints by which one comes to know how the states works. By the satisfaction of inputs namely(Req2,Floor2,Req1,Floor1,Arrive,Open,Delay,Reset)
RTL Description:
This describes the RTL Functional description ie The block diagram of the Elevator System with the specified inputs and outputs.