elevator scheduling lingfeng luo zhao han. elevator scheduling problem elevator as a control system...

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Page 1: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

S

Elevator SchedulingLingfeng Luo

Zhao Han

Page 2: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Elevator Scheduling Problem

Elevator as a control System

Behavior depends on programmed algorithms

Different solution depending on building type and number of elevators working together

Assignment of job

External elevator request

Internal floor request

Page 3: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

The Building

Setting:15 floor building2 elevators

Goal: Simulate and analyze three major elevator scheduling algorithms by JAVA

Use simulation results to find optimal algorithm.

Page 4: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Tools we used

Use JAVA to program different elevator scheduling algorithms.

Use Excel to analyze simulated results and plot chart.

Page 5: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Algorithm A

FCFS ( First come first serve)

Elevators work depends on the order of every request. The first one who sends the request can take the elevator first.

Page 6: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Algorithm B

SSTF- Shortest Seek time first

It will find out which floor is the closest to the elevator. Then, the elevator goes to that floor, and search the next requested floor according to their distance.

Page 7: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Algorithm C

Scan

SCAN makes elevators moving from top to the bottom. Elevators turn back when they reach the top or the bottom.

Page 8: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Performance Metrics

We will evaluate these metrics below for simulated outcome of 3 different elevator scheduling algorithms.

Waiting time of a client: the time in between the client makes a outer request till he gets to the destination floor

C: Total passenger carried in given time interval.

Page 9: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Results – Original Data (FCFS)

Page 10: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Imperfections of the program

and things need to improve

1. the arrival rate is the same for day and night, hour to hour.

2. requested rate is the same on every floor

3. the client is always patient

4. no interface

Page 11: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Limitation of each Strategies

FCFS: not efficient, slows down the process for accessing the floor than it must

SCAN: takes longer for the average request, (won’t starve the process for the sake of others

SSTF: leave some request for very long time

Page 12: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Result Pattern

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94

3 Algorithm Comparison

FCFS SSTF SCAN

Page 13: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Avg Waiting Time

FCFS SSTF SCAN240

245

250

255

260

265

270

275

Total Average Waiting Time

Page 14: Elevator Scheduling Lingfeng Luo Zhao Han. Elevator Scheduling Problem  Elevator as a control System  Behavior depends on programmed algorithms

Thank you!

Questions