FAX: +1.412.253.9378. Lab 6_Simio_Calculations - 3-Server Model Expectations Arrival Rate(per hour IAT(min Capacity Process Rate(per hour Process Time(min Utilization Number. The ranking rule for allocation queues may be specified with either static or dynamic ranking. The Time Offset property (usually set to 0) determines when the initial entity is created. The numerical values used to generate the SMORE plot, like the confidence-interval endpoints, are also available by clicking on the Raw Data tab at the bottom of the SMORE plot window, so you can see what they actually are rather than eyeballing them from the graph. Figure 5.28: Placement resource state results after adding failures. \] To test the model, create an Experiment by clicking on the New Experiment icon in the Project Home ribbon. Clearly, the question at this point is What now? We have a choice between two basic options: Declare that we have eleven good configurations, or do additional experimentation. Before continuing we must point out that you cant replicate away startup bias. Youll see the first screen of hundreds of symbols that have ATM in their name or description, something like Figure 4.36. The characteristics of the exponential distribution probably make it ill-suited for modeling the transaction or processing time at an ATM. Switchboard (Toll Free): +1.877.297.4646 Figure 9.26: Results for the initial OptQuest run (OptQuest1) after running Subset Selection Analysis. We use that same mechanism here we defined a list (DoctorNurse) that includes the Doctor and Nurse objects (with the Doctor objects being first in the list) and seize a resource from this list in the Seize step in the add-on process. Figure 4.38 illustrates these windows in a typical use. Instead a token is created as a delegate of the entity to execute the process. You can repeat all this for the WIP Responses, where smaller is once again better, so you would again choose Minimize for the Objective property; wed actually done this, and happened to get the same subsets of possible best and rejects as we did for the TIS responses, though such agreement for all responses is generally not to be expected. Note that objects appearing in a library and in the Navigation Window are often confusing to new users just remember that objects are placed from the library and are defined/edited from the Navigation Window. Figure 9.52 shows the properties for the Status Pie charts for Server1 and Server3. Figure 9.33: Properties for the Worker1 object. As with most complex mechanical devices, the placement machine is subject to failures where it must be repaired before in can continue processing boards. Splits a batched group of entities or makes copies of a single entity. . When the simulation time reaches 10 (the run length that we set), the model run will automatically pause. In particular, lets change our entity picture from the default green triangle to a more realistic-looking person. Although simulation and animation have been around for many years, Simio makes modeling minutes. Look through all of your objects, especially the ones that you have added or changed most recently. Compared to our models in Chapter 4, Model 5-1 includes two basic enhancements: sequential processes (inspection follows component placement); and branching (after inspection, some boards are classified as good and others are classified as bad). The queueing analysis gives us the exact steady-state values of \(\rho\), \(L\), \(L_q\), \(W\), and \(W_q\). With the OptQuest add-in, we can specify the optimization constraints using either the experiment controls or Constraints well use the experiment controls for the current model since each of the constraints involves limiting the values of a single control (a Referenced Property in the model). Set gbl_InstantaneousUtilization = [Activity 1.Count Contents/Activity 1.Replication]*100. dramatically easier by providing a new object-based approach. improve your business performance. We accomplish this duplication and routing using the Server1_Processing add-on process for Server1. We also set the Value Type property to Expression to indicate that well be using an expression to be evaluated and recorded. So, for our simple model, the expected number of entities in the queue when the first entity arrives after the warm-up period would be \(3.2\) (\(L_q=3.2\) at steady state). What are the maximum number of customers in the system and the maximum average number of customers in the system (recall that we mentioned that our model would not consider the physical space in the ATM). \textrm{Subject to:}\\ When the final Pizza object arrives to the Combiner object, it will be combined with the other Pizza objects and the Customer object and the order will be complete. and then use the results from the 30 replications to compute a confidence interval for our performance As such, you definitely want to know how to tell the model to track these types of user-defined statistics yourself. The model also has a Source object (CustomerCall) and Server objects for the order taking (TakeOrder), making (Make), and boxing (Box) processes and the oven (PizzaOven). While we cant say with any certainty that OptQuest finds the best solution, its quite likely that OptQuest can do better than you (or we) could do by just arbitrarily searching through the feasible region (especially after youve reached your 37th scenario and are tired of looking at the computer). Now we can return to the question of why our initial simulation results are not equal to our queueing results in Table 4.2. For Model 9-1, our goal is to demonstrate a model that can be used for decision-making and to demonstrate simulation-based optimization using Simio. Unfortunately, even though we ran ten times more scenarios, we still dont really know how good our new best solution actually is with respect to the true optimum. Finally, select the Elements icon from the model Definitions Panel and add the three Output Statistics to compute the proportion of processing steps completed by each machine. they are processed one at time, and then travel to a Sink and depart the system. \[\begin{align*} Let a Simio Expert show you more about our products and how we can help. arrival processes that are purely random and independent. consulting services to assists you with your project. Of course, the discussion of warm-up in the previous paragraphs assumes that you actually want steady-state values; but maybe you dont. Figure 5.7: Using add-on processes to add a repair resource. Set the Triggering Event property to be the newly created timer event (see Figure 4.16). We first discussed the concept of dynamic-simulation events in Section 3.3.1. The objective function that wed like to minimize is TotalCost, and the lines after Subject to are constraints (the first six on input controls, and the last one on another, non-objective-function output). For our initial model, we used Connectors to connect the objects and specify the entity flow. This will bring up a dialog box where you enter the Reference Property name (we used InitialCapacityFast). Figure 4.14 shows the completed Simio process. We chose the name Model_04_01.spfx (spfx is the default file-name extension for Simio project files), following the naming convention for our example files given in Section 3.2; all our completed example files are available on the books website, as described in Appendix C. Before we continue constructing our model, we need to mention that the Standard Library objects include several default queues. However, for simulation, this predictability is a good thing. Sink1 InputBuffer.Contents Used to store entities waiting to enter the Sink object. Since the expected percentage of time that the placement machine is idle (\((1 - 0.9010) \times 100 = 9.91\%)\) is greater than the expected percentage of failed time, wed expect the system to remain stable. Consider the simple case where we have a zero-capacity buffer (e.g., no buffer) between two stations that we model as resources. Note that the referenced properties show up as Controls in the experiment. the impact of change. In each case, first compute numerical values for the queueing-theoretic steady-state output performance metrics \(W_q\), \(W\), \(L_q\), \(L\), and \(\rho\) from the results in Section 2.3, and then compare these with your simulation estimates and confidence intervals. Yet were still faced with the need for model verification. Do you want to continue? If you need to keep the undo history (and we cant think of a reason why this would ever be the case, but you never know! model for this system is shown below. In an experiment, the values for these properties can be set, and we can define a scenario by specifying the number of replications to run and values for each of the three referenced properties. Instead, we have to create and run a Simio Experiment. The time between the start of the run and the point at which the model is determined to have reached steady state (another one of those judgment calls) is called the initial transient period, which well now discuss. To create our work schedule, select the Model in the Navigation pane, select the Data tab, and the Schedules icon in the Data panel. New users will often unnecessarily resort to using more complex add-on processes in order to implement this type of logic. As you get further into modeling, youll find yourself spending significant time debugging your models so this behavior will prove useful to you (see Section 4.9 for detailed coverage of the debugging process and Simios debugging tools). Next, click on the Source object in the Standard Library, then drag and drop it into the Facility Window. \end{align*}\]. A Simio project consists of one or more models or objects, as well as other components like symbols and experiments. a variable and complex dynamic system. Processing Count Based the uptime is based on the number of times the server processes an entity and you specify the number of times that the server processes between failures. When you do model experimentation from the Experiment window, referenced properties automatically (unless you set its Visible value to, Complete the Seize step properties: Double click on the Rows property, Complete the Release step properties: Double click on the Rows property. A minimal number of entities help all of the other debugging processes and tools work better. If you run the model and look at the interactive results you should see the server failed for 10% of the time and likewise the Worker utilized for a corresponding 10% of the time. Determining the appropriate distribution(s) to use is part of input analysis, which is covered in Section 6.1. A zero-time connection between two nodes. Instead it potentially has a cost each time it carries an entity, as well as a transportation cost while it is moving. In this case, each arriving entity contributes a single observation (the time that entity spends in the system) and Simio tracks and reports the summary statistics for these values (\(\widehat{W}\), in this case). The Server object has properties that specify things such as the capacity (i.e. Properties cant change definition during a run. But we ran for only 10 hours, which for this model is evidently not sufficiently close to infinity. by scheduling arrivals, eliminating variation in processing, etc.) In most cases these windows open automatically as a result of some action. Given that all customers must insert their ATM card, correctly enter their personal identification number (PIN), and select their transaction, and that the number of ATM transaction types is generally limited, a bounded distribution is likely a better choice. At this point we have a simple model using the Standard Library objects that incorporates failures. Limit your model to just a single entity and see if you can reproduce the problem. For example, if the user defined the value of 5.3 for a ProcessTime property, it will always return 5.3 and it cant be changed without stopping the run. Step 7 sets up this statistic and step 15 records each observation. Why or why not? The output statistics for the medium and slow machine are similarly defined except we replace the NumFast in the numerator with NumMedium and NumSlow, respectively. b What is the server utilization rate 3 pts Sol 8 0 20 16 5 Simio Analysis 20. The final step for setting up OptQuest is to define the objective function i.e., tell OptQuest the criterion for optimization. If not, add a second entity. The length of the path can also be estimated using the drawing grid. The basic concept of marking an entity with the simulation time at one point in the model, then recording the time interval between the marked time and the later time in a tally statistic, is quite common in situations where we want to record a time interval as a performance metric.
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