 Elevator Scheduling Lingfeng Luo Zhao Han

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

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  Use JAVA to program different elevator scheduling algorithms.  Use Excel to analyze simulated results and plot chart.

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.

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.

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

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.

Results – Original Data (FCFS)

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

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

Result Pattern

Avg Waiting Time

Thank you! Questions