Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales

1. Simulation-based assessment of the robustness of IP-based truck schedules for cross-docking operations Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales This exchange program isfunded by

2. IP-based truck schedules for Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 assessment of the robustness of Simulation-based assessment of the robustness of IP-based truck schedules for cross-docking operations Simulation-based cross-docking operations Cross-dockingoperations IP-based truck schedule Robustnessassessment Results Conclusion - Cross-dockingoperations IP-based truck schedule Robustnessassessment Results Conclusion -

3. Anne-Laure Ladier, Allen Greenwood, GülgünAlpan, Halston Hales | EURO-INFORMS 2013 Cross-docking Lessthan 24h of temporary storage docking unloading Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion scanning transfer loading departing

4. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Schedulingproblem • Minimize • Quantity put in storage • Dissatisfaction of the transport providers • Reservation system: 6am-9am 10am-12am 6am-9am 6am-8am 11am-12am Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion 9am-12am 7am-10am 6am-7am

5. Anne-Laure Ladier, Allen Greenwood, GülgünAlpan, Halston Hales | EURO-INFORMS 2013 IP model (IESM 2013, Rabat) • Assumptions • Internal operations are done in masked time, within one time unit • The door-to-door distance for the transfer is not taken into account • The pallets unloaded on the floor can be picked in any order • Decision variables • # of unitsmovingfrom point to point (incl. storage) • Time windows for the trucks Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion

6. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Research question How do randomeventsdistort the schedule ? How to assessitsrobustness? Whatshouldbechanged in the IP model to make the schedule more robust? Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion

7. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Methodology • Discreteevents simulation • Simulatecomplexstochasticprocesses • Addlogic to react in unplanned situations • Gather data over multiple runs • Software: FlexSim (http://www.flexsim.com) Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion

8. Simulation and optimization Optimizationmodel Simulationmodel Simulationmodel Optimizationmodel Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion Optimizationmodel Optimizationmodel Simulationmodel Simulationmodel Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013

9. Principle Randomevents Simulationmodel Logic Optimizationmodel Truck schedule Logic Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion • Comparison • Truck arrival and departure time • Amount in storage • Pallettransfer Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013

10. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Model demonstration

11. Anne-Laure Ladier, Allen Greenwood, GülgünAlpan, Halston Hales | EURO-INFORMS 2013 Validity range • Someassumptions are ratherstrong Are theyreasonable? • Internal operations are done in masked time, within one time unit Simulationmodel Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion Optimizationmodel

12. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Insights from the simulation • Correlationbetweenerror in docking time and error in stay time? Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion All delayed trucks are critical No truck iscritical Somedelayed trucks are critical door1 door2 door3 Number of critical trucks a priori ≤ Nb of actualcritical trucks

13. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Robustness • EverythingisdeterministicWhat if randomeventsoccur? • Trucks arrival time (early / late) Simulationmodel Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion Optimizationmodel

14. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Robustness • EverythingisdeterministicWhat if randomeventsoccur? • Content of the inbound trucks Simulationmodel Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion Optimizationmodel

15. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Conclusion • Simulation isused to assess the robustness, but also to gatherideas on robustnessimprovement • Ideas to make the IP model more robust • Add a flexible « buffer » door • Change the model to use n-1 doors • Avoidcritical trucks Cross-docking operations IP-based truck schedule Robustness assessment Results Conclusion

16. Thankyou for your attention! Questions? Contact: Anne-Laure.Ladier@g-scop.fr

17. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 IP* • Data • Decision variables

18. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 IP*

19. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013

20. Anne-Laure Ladier, Allen Greenwood, Gülgün Alpan, Halston Hales | EURO-INFORMS 2013 Palletstransfer