Transcript Elevator Scheduling

Elevator Scheduling
Lingfeng Luo
Zhao Han
S
Elevator Scheduling Problem
S Elevator as a control System
S
Behavior depends on programmed algorithms
S
Different solution depending on building type and
number of elevators working together
S Assignment of job
S
External elevator request
S
Internal floor request
The Building
Setting:
15 floor building
2 elevators
Goal:
Simulate and analyze three
major elevator scheduling
algorithms by JAVA
Use simulation results to find
optimal algorithm.
Tools we used
S Use JAVA to program different elevator scheduling
algorithms.
S Use Excel to analyze simulated results and plot chart.
Algorithm A
S FCFS ( First come first
serve)
S Elevators work depends
on the order of every
request. The first one who
sends the request can take
the elevator first.
Algorithm B
S SSTF- Shortest Seek time first
S 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.
Algorithm C
S Scan
S SCAN makes elevators
moving from top to the
bottom. Elevators turn
back when they reach
the top or the bottom.
Performance Metrics
S We will evaluate these metrics below for simulated outcome
of 3 different elevator scheduling algorithms.
S Waiting time of a client: the time in between the client
makes a outer request till he gets to the destination floor
S C: Total passenger carried in given time interval.
Results – Original Data (FCFS)
Imperfections of the program
and things need to improve
S 1. the arrival rate is the same for day and night, hour to
hour.
S 2. requested rate is the same on every floor
S 3. the client is always patient
S 4. no interface
Limitation of each Strategies
S FCFS: not efficient, slows down the process for accessing
the floor than it must
S SCAN: takes longer for the average request, (won’t starve
the process for the sake of others
S SSTF: leave some request for very long time
Result Pattern
3 Algorithm Comparison
FCFS
SSTF
SCAN
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95
Avg Waiting Time
Total Average Waiting Time
275
270
265
260
255
250
245
240
FCFS
SSTF
SCAN
Thank you!
Questions