代写IMSE3107 Systems Modelling and Simulation Assignment 2代做留学生SQL语言

IMSE3107

Systems Modelling and Simulation

Assignment 2

Objective

The objective of this assignment is to assess the ability of the students to build Excel and FlexSim simulation models to solve typical industrial or logistics engineering application problems.

Problem 1 (20 marks)

An operation of a company relies on a machine which has 3 different bearings with identical distribution of the lifetime as shown in Table 1. The machine will fail to operate if any one of the bearings fails. In case of machine failure, a mechanic is called to repair the machine and the delay time for the mechanic to arrive is random with a distribution shown on Table 2. The time for a mechanic to repair the machine depends on the total number of bearings that need tobe replaced. The mechanic can replace one bearing at a time, taking 20 minutes for each, or that the total time for replacing all bearings at once is fixed at 38 minutes. Table 3 lists all the costs associated with the maintenance of the machine.

Table 1

Table 2

Table 3

There are 2 maintenance policies for the management to consider.

Policy 1: Replace only the bearing that fails, and other operable bearings remain unchanged.

Policy 2: Replace all 3 bearings whenever any one of the 3 bearings fails.

For policy 1, it is assumed that the bearings are never fail at the same time. Hence, there is no more than 1 bearing that need to be replaced at the same time.

The performance measures of the policies are defined as the total cost per 10,000 bearing-hours. Assume that the performance measures for both policies are normally distributed.

(a)   Based on the template (Q1_template.xlsm), which can be downloaded from Moodle, build Monte Carlo simulation models for the 2 policies to simulate the lift times of 90 bearings.  In the simulation models, include experiment of 10 replications for both policies. Estimate the performance  measures for both policies  and give your estimations together with 90% confidence intervals.  Save the macro-enabled Excel file as “Q1a.xlsm”.       (10 marks)

(b)  It is expected that, if a bearing is cheap, the total cost per 10000 bearing-hours will be lower for policy 2. The management is interested to know the decision point of the cost of bearing, i.e., if the cost is lower than the decision point, the result will favour policy 2. However, if it is higher than or equal to the decision point, policy 1 will be preferable. Modify the models in

(a) for both policies to 10 experiments with different costs of bearing from HK$500  to HK$5000 with a separation of HK$500. Summarize the mean values of the experiments of both policies in a single worksheet for comparison. Indicate the decision point of the cost of bearing in the worksheet. Save the macro-enabled Excel file as “Q1b.xlsm”. Moreover, write a description of your observations comparing the two policies used in the simulation models. Limit your description to 100 words. Save the document as “Q1b.docx” in Microsoft Word format.          (10 marks)

Figure 1 is a schematic diagram of a parcel sortation system. The system consists of a main conveyor and 6 evenly separated lane conveyors. The arrows indicate the direction of flow for each conveyor. Parcels are first moved into the system onto the main conveyor at position A and then diverted to the lanes or the end buffer.  The inter-arrival time of parcels is uniformly distributed between 1 and 5 seconds.  Each parcel has a unique destination code,  which corresponds to one of the 6 codes shown in Table 1. After entering the system, a parcel is diverted to one of the 6 lanes based on its destination code. If a parcel reaches  the entrance  of  its designated lane and that lane is filled, the parcel is diverted to the end buffer. The simulation begins when the first parcel arrives at position A. The capacity of the end buffer is large enough to accommodate any number of parcels; therefore, no parcels will accumulate at the end of the main conveyor.

Figure 1

Table 1

Each lane has a conveyor connected to a buffer atthe end, with a workstation located next to each buffer. When a parcel reaches the end of the conveyor, it is stopped in the buffer, where it is held until it can be moved to the workstation. Each buffer can accommodate a maximum of 4 parcels, while each conveyor can hold up to 6 parcels. When the buffer is full, any additional parcels will wait until space becomes available.

An operator moves parcels from the buffer onto a pallet at the workstation.  The  size of a workstation is the same as the size of a pallet. Once 8 parcels have been placed on the pallet, the operator wraps them together. After wrapping, the pallet with the wrapped parcels is moved to the staging area by a forklift, with an assigned number  (see Table  1). When  a filled pallet is released from the workstation, an empty pallet is immediately replaced. It can be assumed that there is no shortage of empty pallet. The wrapping process takes between 8 and 30 seconds, but most likely, about 20 seconds to complete.

The speed of the input main conveyor is 1ms-1 . The lane conveyors run at 0.4ms-1 .  All conveyors have a width of 1 m and the   lengths are shown in Figure 1. The size of a parcel   is 0.4 × 0.4 × 0.2 m! .  The  size  of  a  pallet  is  1 × 1 × 0.1 m! .  The  input  main  conveyor  is  non- accumulative, but all other conveyors are accumulative. The maximum travelling speed of an operator is 3ms-1  and the acceleration or deceleration are both 1ms-2 . Both the load and unload time of an operator are assumed to be zero. Also, it is assumed that an operator can handle only one movement of a parcel at a time. The path of the forklift should not cross the buffers, conveyors or the staging areas. The following is the specification of the forklift:

Load Time = 2                                  Unload Time = 10

Assume that there are 2 operators and  1 forklift.  One of the operators is responsible for the processes of Lanes 1 to 3, and the other operator is responsible for the processes of Lanes 4 to 6.

(a)   Use FlexSim 2020 Update 1 to simulate the system for 2000 parcels. Set up a dashboard with pie charts to monitor the utilizations ofthe operators, and bar chart to monitor the number of parcels in the end buffer. Save the FlexSim model as “Q2a.fsm”.      (10 marks)

(b)  Ideally, the utilization of the operators should be equal. Also, the number ofunsorted parcels in the end buffer should be minimized. Improve the system by re-assigning the destination codes to the lanes. Use FlexSim 2020 Update 1 to simulate the improved system for 2000 parcels. Save the FlexSim model as “Q2b.fsm”. Write a description of the observed problem and your suggestion for improvement. Limit your description to 100 words. Save the document as “Q2b.docx” in Microsoft Word format.     (10 marks)

Assessment

Assessment will primarily be based on whether the models are properly and accurately built.

Mark

•     The total mark for this assignment is 40.

•     This assignment contributes 20% of the total marks in this course.

Submission

•     Upload all the files (Q1a.xlsm, Q1b.xlsm, Q1b.docx, Q2a.fsm, Q2b.fsm and Q2b.docx) to Moodle on or before 26 March 2025.

•     Late submissions are not accepted.

•     By submitting files through Moodle, you declare that the submitted files represent the work done by yourself only and that you have not committed plagiarism and/or collusion in the submission.