ELEVATOR DISPATCHING

1
ELEVATOR DISPATCHING
COMPLEXITY Huge state space, Movement
constraints, non-stationary distributions, etc.
Christos G. Cassandras

CODES Lab. - Boston University
2
ELEVATOR DISPATCHING
CONTINUED
UPPEAK DISPATCHING CONTROL PROBLEM
Christos G. Cassandras

CODES Lab. - Boston University
3
ELEVATOR DISPATCHING
CONTINUED

• Can be shown that the optimal policy minimizing
  average waiting time is a threshold policy with
  thresholds that depend on
• passenger arrival rate
• service rate

Ref Pepyne and Cassandras, IEEE Trans. on CST,
1997

• WHAT DOES THIS MEAN IN PRACTICE?
• Load one car at a time
• call this car the next car to be dispatched
• Dispatch the next car when

number of passengers inside car ? q(l,m)
Christos G. Cassandras

CODES Lab. - Boston University
4
ELEVATOR DISPATCHING
CONTINUED
Variation in l over 12 5-min. intervals for 1
hour uppeak traffic (courtesy P. Powell, OTIS
Elevator)

• PROBLEM
• How to determine thresholds, one for each
• 5 min. interval of fixed traffic rate?
• How to automatically adjust them on line?

Christos G. Cassandras

CODES Lab. - Boston University