incomplete, and they are categorized by mission type. A successful mission means that it was able to fly the mission duration without a critical part failure, otherwise the mission is aborted. An incomplete mission is one that was not assigned due to the lack of aircraft which could fly that particular mission.
3.6. Incorporating Randomness
Incorporating randomness in a simulation is an important feature in quantifying the uncertainty in the process. Most of the values used in the simulation can be defined as a random variable. Some of these variables include mission length, part life time, replacement time of failed parts on the vehicle, repair time of parts, and transit times between the part repair depot and inventory location.
3.7. Model Features
Currently, VE-OPS has several features to perform sensitivity studies and to analyze the impact of different strategies. To study the impacts of the constraints imposed by workers and workstations, the model can limit the number of hours the workers can work as well as the total number of workers and workstations. Depending on the vehicle, it can have different modes of operation or missions it can perform. For example, a multi-role fighter can be used for an air-to-air engagement, an air-to-surface mission or an intelligence, surveillance and reconnaissance mission as well as training operations. The vehicle can also be in partial mission capable status where it can perform some of the mission types but not all. The current model can handle a table of parts with different characteristics such as part life, time to replace a part on a vehicle, time to repair the broken part, and time to transport the part between the depot and local inventory. The amount of parts in the inventory can also be set as an input to simulate a shortage of parts. Some vehicle repairs can be performed in parallel while others must be performed in series, and to capture this constraint, the parts can be designated into repair groups where each part in the group can be replaced in parallel. Some parts are critical to certain missions but not critical to flight, and if these parts fail, the vehicle can still perform other missions and complete them. Because the simulation is object-oriented, multiple instances of the model can be connected to simulate contingency events and to study the transitional behavior. For example, air cargo transport vehicles are important for humanitarian aid in places that are difficult to reach, and it is useful to understand how the vehicle sustainment requirements change when supporting these missions. The transition between the normal and contingency operation can be simulated by creating one model for the normal operation and another for the contingency operation, and the two models are connected so that the vehicles and parts can be transferred from one model to the other. To enable this analysis, there are two additional process classes that move the vehicles and distribute spare parts between inventories.
3.8. Future Development
This simulation model environment VE-OPS supports future research in the area of maintenance and logistics. One area of interest is to investigate repair policies of partial mission capable (PMC) vehicles. A vehicle that can perform multiple types of missions does not necessarily need to be repaired to full mission capable (FMC) status depending on the future mission requirements and the fleet-wide capability. It may be more beneficial to the overall mission effectiveness if it forgoes the unscheduled maintenance for certain mission specific components until there is a more opportunistic time in the future. Another area is to research part allocation schemes between the central and forward supply depots. There are several additions to VE-OPS that will enhance its analysis capabilities and widen its application areas. Some of these include the ability to cannibalize vehicles for parts, an option for three-level maintenance, a prognostics health management (PHM) system, and a supply chain network for spares. Another goal is to create process classes with different levels of fidelity and complexity so that users can choose and customize features of their models. Not all studies need the maximum fidelity in all segments of the simulation. It would be better if the model is composed of modular segments, with each having different variants. By making the segments modular, thedevelopment can also occur heterogeneously and in parallel, and to support this, standards are necessary to ensure compatibility between the components.
4. Case Study
To demonstrate how this tool can be used, a sensitivity case study is presented. The case study focuses on the impact of extending the supply chain on the mission capable rate of a fleet of F-16. The model simulates the sortie generation of a fleet of 16 aircraft, and there are four parts on the vehicle that can break and be replaced. There is also a supply chain that replenishes the local inventory from a nearby depot. Most of the values and distributions for the process steps were taken from Faas thesis [42] which looks at the impact of ALS to the overall mission capable (MC) rate. The model was calibrated to 80% MC rate by varying the part reliability. For this case study, the time to deliver the part from the depot to the local inventory is varied from an average of 0.3 days to 2.2 days. The delivery time is given a triangular distribution with low and high values set at 0.2 days apart from the mean. The baseline value is 0.3 days. The maximum level for the local inventory is set at 7 parts, and a new part is requested from the depot every time a part is taken from the local inventory. Fig. 3 shows the impact of delivery time to the MC rate, and Fig. 4 shows how the local inventory level of one of the parts varies with simulation time and delivery time. The gray lines in Fig. 4 are the maximum and minimum inventory levels per day, and the black line shows the average inventory level. Inspecting Fig. 3, the MC rate begins to decrease after the delivery time grows beyond 1.0 day, and flattens off at a MC rate of 0.7 from 1.4 to 1.9 days. After this point, the MC rate falls rapidly. Looking at Fig. 4, the minimum daily inventory level becomes consistently 0 with an average delivery time of 1 day, which explains the first drop. There is at least one vehicle waiting for this part to arrive from the depot for any given day. The maximum daily inventory level begins to hit 0 with an average delivery time of 2.0 days, which indicates that there are times when the delivery from the depot is not enough to overcome the backlog.
ไม่สมบูรณ์ และพวกเขาจะแบ่งตามชนิดของภารกิจ ภารกิจสำเร็จหมายความ ว่า มันสามารถบินระยะภารกิจไม่สำเร็จส่วนที่สำคัญ หรือ ยกเลิกภารกิจ ภารกิจไม่สมบูรณ์เป็นหนึ่งที่ไม่มีกำหนดเนื่องจากมีเครื่องบินที่สามารถบินภารกิจที่เฉพาะ 3.6 การเพจ Randomness เพจ randomness ในการจำลองเป็นคุณลักษณะสำคัญใน quantifying ความไม่แน่นอนในกระบวนการ ส่วนใหญ่ค่าที่ใช้ในการจำลองสถานการณ์สามารถกำหนดเป็นตัวแปรสุ่ม ของตัวแปรเหล่านี้มีภารกิจยาว เวลาชีวิตส่วน เวลาทดแทนส่วนที่ล้มเหลวบนรถ เวลาซ่อมชิ้นส่วน และระยะเวลาการขนส่งระหว่างส่วนซ่อม depot และคงตำแหน่ง 3.7 การจำลองลักษณะการทำงาน Currently, VE-OPS has several features to perform sensitivity studies and to analyze the impact of different strategies. To study the impacts of the constraints imposed by workers and workstations, the model can limit the number of hours the workers can work as well as the total number of workers and workstations. Depending on the vehicle, it can have different modes of operation or missions it can perform. For example, a multi-role fighter can be used for an air-to-air engagement, an air-to-surface mission or an intelligence, surveillance and reconnaissance mission as well as training operations. The vehicle can also be in partial mission capable status where it can perform some of the mission types but not all. The current model can handle a table of parts with different characteristics such as part life, time to replace a part on a vehicle, time to repair the broken part, and time to transport the part between the depot and local inventory. The amount of parts in the inventory can also be set as an input to simulate a shortage of parts. Some vehicle repairs can be performed in parallel while others must be performed in series, and to capture this constraint, the parts can be designated into repair groups where each part in the group can be replaced in parallel. Some parts are critical to certain missions but not critical to flight, and if these parts fail, the vehicle can still perform other missions and complete them. Because the simulation is object-oriented, multiple instances of the model can be connected to simulate contingency events and to study the transitional behavior. For example, air cargo transport vehicles are important for humanitarian aid in places that are difficult to reach, and it is useful to understand how the vehicle sustainment requirements change when supporting these missions. The transition between the normal and contingency operation can be simulated by creating one model for the normal operation and another for the contingency operation, and the two models are connected so that the vehicles and parts can be transferred from one model to the other. To enable this analysis, there are two additional process classes that move the vehicles and distribute spare parts between inventories. 3.8. อนาคต การจำลองแบบจำลองสภาพแวดล้อมนี้ VE OPS สนับสนุนวิจัยในอนาคตในการบำรุงรักษาและโลจิสติกส์ พื้นที่หนึ่งที่น่าสนใจคือการ ตรวจสอบนโยบายซ่อมยานพาหนะ (PMC) ความสามารถในภารกิจบางส่วน ยานพาหนะที่สามารถปฏิบัติภารกิจได้หลายชนิดไม่จำเป็นต้องซ่อมแซมเต็มภารกิจสามารถ (FMC) สถานะขึ้นอยู่กับความต้องการในอนาคตพันธกิจและความสามารถทั้งกอง อาจมีประโยชน์ต่อโดยรวมประสิทธิภาพของภารกิจถ้ามัน forgoes บำรุงรักษาฐานะบางภารกิจคอมโพเนนต์เฉพาะจนกว่าจะมีเวลายกขึ้นในอนาคตได้ พื้นที่อื่นคือการ วิจัยส่วนหนึ่งแผนงานการปันส่วนระหว่างคลังกลาง และไปข้างหน้า มีเพิ่มหลายการ VE OPS ที่จะเพิ่มความสามารถในการวิเคราะห์ และขยายพื้นที่ของแอพลิเคชัน เหล่านี้รวมถึงสามารถ cannibalize ยานพาหนะ ตัวเลือกสำหรับการบำรุงรักษาสามระดับ มีระบบการจัดการ (PHM) สุขภาพ prognostics และเครือข่ายห่วงโซ่อุปทานสำหรับอะไหล่ เป้าหมายอีกประการหนึ่งคือการ สร้างกระบวนการเรียนกับระดับของความจงรักภักดีและความซับซ้อนเพื่อให้ผู้ใช้สามารถเลือก และกำหนดคุณลักษณะของรูปแบบของพวกเขาเอง ศึกษาไม่ต้องการคุณภาพสูงสุดในเซ็กเมนต์ทั้งหมดของการจำลอง มันจะดีกว่าถ้าแบบประกอบด้วยเซ็กเมนต์ modular ด้วยมีตัวแปรแตกต่างกัน โดยเซ็กเมนต์ modular, thedevelopment สามารถเกิด heterogeneously และขนาน และสนับสนุนนี้ มาตรฐานจำเป็นเพื่อตรวจสอบความเข้ากันได้ระหว่างส่วนประกอบ 4. Case Study To demonstrate how this tool can be used, a sensitivity case study is presented. The case study focuses on the impact of extending the supply chain on the mission capable rate of a fleet of F-16. The model simulates the sortie generation of a fleet of 16 aircraft, and there are four parts on the vehicle that can break and be replaced. There is also a supply chain that replenishes the local inventory from a nearby depot. Most of the values and distributions for the process steps were taken from Faas thesis [42] which looks at the impact of ALS to the overall mission capable (MC) rate. The model was calibrated to 80% MC rate by varying the part reliability. For this case study, the time to deliver the part from the depot to the local inventory is varied from an average of 0.3 days to 2.2 days. The delivery time is given a triangular distribution with low and high values set at 0.2 days apart from the mean. The baseline value is 0.3 days. The maximum level for the local inventory is set at 7 parts, and a new part is requested from the depot every time a part is taken from the local inventory. Fig. 3 shows the impact of delivery time to the MC rate, and Fig. 4 shows how the local inventory level of one of the parts varies with simulation time and delivery time. The gray lines in Fig. 4 are the maximum and minimum inventory levels per day, and the black line shows the average inventory level. Inspecting Fig. 3, the MC rate begins to decrease after the delivery time grows beyond 1.0 day, and flattens off at a MC rate of 0.7 from 1.4 to 1.9 days. After this point, the MC rate falls rapidly. Looking at Fig. 4, the minimum daily inventory level becomes consistently 0 with an average delivery time of 1 day, which explains the first drop. There is at least one vehicle waiting for this part to arrive from the depot for any given day. The maximum daily inventory level begins to hit 0 with an average delivery time of 2.0 days, which indicates that there are times when the delivery from the depot is not enough to overcome the backlog.
การแปล กรุณารอสักครู่..
