1 Automotive Maintenance and Repair Shop Expansion Presentation by Steve Roberson For CST 5306 Modeling and Simulation

2 Model Building Steps 1. Define the scope of the model 2. Define the data to be used in the model 3. Define any submodels that may be needed to break up the complexity 4. Build the submodels 5. Add animation 6. Run the simulation

3 Step 1 Scope - General 3 bay facility Appointments scheduled at one location Appointments made up to three working days in advance – No same day service

4 Step 1 Scope - Statistics Average service calls – 29 per day following a Poisson distribution 55% schedule for next day, 30% two days in advance and remaining 15% three days in advance If appointment can’t be scheduled for the requested day, 90% chance will be scheduled for following day 80% leave vehicles, 20% wait on service Wait time is service time + 1 hour (allowance factor) No more than five waiting customers will be scheduled in one day Standard service times are in a BETA distribution – Actual service times are in a GAMMA distribution

5 Arena Statistical Distributions Beta Continuous Discrete Erlang Exponential Gamma Johnson Lognormal Normal Poisson Triangular Uniform Weibull

6 Step 1 Scope - Costs 24 hours of availability – 3 bays at 8 hours per day Cost per bay - $45 per hour Customer charged - $78 per hour base on standard service time Overtime – Limited to 3 hours extra per day per bay – Charge is $120 per hour per bay If work not completed by end of day, customer given loaner car at a dealership cost of $35 per day

7 Step 1 Scope – Statistics Collected Daily profit Daily standard service times Daily actual service times Daily overtime Daily number appointments not completed on time

8 New Modeling Methods Multiple-way decisions Sets Variables and expressions Submodels Duplicating entities Holding entities Statistics and animation Terminating or steady-state

9 Step 2 Define the Data Define resources (3 bays) Define sets – Bay resource set – Customer entity set (customer who waits) – Vehicle entity set (vehicles left for service) Define variables (15 determined) Define expressions – Formula to determine inter-arrival time – Formula to determine service time – Formula to determine if customer has to wait for service Final statistics (costing, overtime, service times and waiting times)

10 Step 3 Define Submodels Complete Model

11 Step 4 Build Submodels Generate Appointment Calls

12 Step 4 Build Submodels Make Appointment

13 Step 4 Build Submodels Service Activity

14 Step 4 Build Submodels Update Performance Variables

15 Step 4 Build Submodels Control Logic

16 Step 4 Build Submodels In Arena, the model can be checked for errors Errors are flagged to assist with troubleshooting

17 Step 5 Add Animation Animated Service Center

18 Step 6 Run Simulation Run simulation Observe results Analyze results

19 Model Enhancements

20 Redefining the Scope Not all jobs done by all bays – Bays 2 & 3 can handle all jobs – Bay 1 can only handle 40% of the jobs Not all customers arrive at start of day – Some never show up – 60%-70% arrive on time (follows uniform distribution) – Remaining arrive randomly over next two hours

21 Sets and Resource Logic Additional Resource Set

22 Model Change Service Activity

23 Model Change Control Logic

24 Re-run Simulation Observe results Analyze results