Chapter 1: Introduction to Simulation

This chapter will cover theoretical aspects and general understandings of simulation, as well as introduce you to the key capabilities of Plant Simulation. After completing this chapter, you will be able to:

• Understand what simulation is and what benefit simulation provides
• Understand different types of simulation
• Understand key capabilities and use cases of Plant Simulation

Simulation

“Simulation is the representation of a system with its dynamic processes in an experimentable model to reach findings which are transferable to reality. In particular, the processes are developed over time.” (VDI 3633-1, 2010)

The increasing complexity of products, processes, and systems is one of many reasons why simulation is increasingly used in the planning, implementation, and operation of technical systems. As an integral part of the digital factory concept, simulation helps to shorten time-to-market and supports decision-making processes. Simulation is particularly useful for analyzing a system, in which its behavior dynamically changes over time and a mathematical solution cannot be calculated at a reasonable effort.

During the planning phase, simulation can be used to:

• Determine the required amount of resources, transport systems, buffer sizes
• Validate and optimize planning parameters
• Evaluate planning alternatives based on different scenarios
• Analyze system behavior over long time periods and during ramp-ups
• Provide a proof-of-concept

During the operation phase, simulation can be used to:

• Optimize control strategies, scheduling, and order sequencing
• Verify resource and buffer utilization, batch sizes, and inventory levels
• Analyze what-if scenarios without interrupting an operating system
• Analyze the influence of failures and interruptions
• Train workers in the process and material flow

Types of simulation

Simulation can be used for physical phenomena, business processes, pedestrian and traffic flow, as well as manufacturing and logistics operations. Mainly, there are two different types of simulation:

• Continuous simulation
• Discrete-event simulation

Whereas continuous simulation view state changes in the simulation model over time in a continuous manner, discrete-event simulation only inspects certain points in time, at which a certain event takes places or a certain model component changes its states, e.g. when a station starts or finishes processing a part. As such, discrete-event simulation jumps from one event or one state change to the next and skips the time in between.

Simulation activities

The scope of simulation can range from a sub-area of a production facility to a globally distributed supply-chain network. In manufacturing and logistics, simulation helps to identify bottlenecks, high inventory levels, feasible throughput amount, and suitable control strategies. A typical process of a simulation project consists of (Rabe, Spieckermann, Wenzel, 2008):

• Problem and target description
• System analysis
• Data collection
• Model formalization and implementation
• Experiment and analysis of simulation results

Simulation is always based on a model, which is a simplified reproduction of a planned or an existing system. Thus, simulation results can only be as good as the model and the data on which the simulation experiment is based (VDI 3633-1, 2010). In order to get feasible results with reasonable efforts, the level of detail of a simulation model should be neither too detailed nor too abstracted.

Tecnomatix Plant Simulation

Plant Simulation is a discrete-event process simulation software and part of the Tecnomatix digital manufacturing solutions by Siemens PLM Software. Plant Simulation enables its user to create an object-oriented and hierarchical simulation model of production and logistics systems, including their complex control strategies. Based on these simulation models, you can perform an analysis of the system characteristics, detect potential vulnerabilities or bottlenecks, and optimize performance including resource utilization, throughput, and material handling operations.

Key capabilities of Plant Simulation

The main key capability of Plant Simulation is the object-oriented and hierarchical modeling approach. The object-oriented approach enables a child object to inherit its properties (attributes) and behaviors (methods) from a parent object. The modeling capabilities of Plant Simulation not only allows you to use standard library objects but also to develop reusable custom library elements. This allows you to define complex material flow rules and control strategies, check their performance in a simulation model, and reuse them in other simulation models.

According to Siemens PLM Software, other key capabilities of Plant Simulation are:

• Object libraries and management for standard and custom library elements
• Interactive 2D and 3D visualization with facility layout integration
• Integrated charts to visualize and analyze throughput, utilization, and bottlenecks
• Integrated neuronal networks, genetic algorithms, and experiment manager
• Open system architectures that support numerous interfaces (e.g. ActiveX, SQL, ODBC, Socket, etc.)

Before you begin

Make sure that Plant Simulation is installed and running on your computer. Plant Simulation is available with commercial and non-commercial licenses. Non-commercial licenses for academia include Educational License and Research License. If you are a student from an academic institution, you can download the free student version of Plant Simulation from Siemens PLM Software.

Note that the amount of objects that can be created in a simulation model is limited to 80 objects with Student License and 1000 objects with Educational License. You can still load a simulation model created using other license options in Student or Educational License. However, if the amount of objects exceeds the limit, you will not be able to save the model.

Also, note that simulation models created with a non-commercial license cannot be used for commercial purposes. Models created with Student or Research License can still be opened in Plant Simulation with a commercial license, e.g. Professional License. However, it is not possible to open a model created with Educational License in Plant Simulation with a commercial license.

This tutorial is created using Plant Simulation 14.0.1 with Professional License. If you use a previous version of Plant Simulation (e.g. Plant Simulation 13 and downwards), some functionalities may vary and you will not be able to open the example models provided in this tutorial due to the downward incompatibility of Plant Simulation.

Note that you can open and run simulation models created using a previous version with a newer version of Plant Simulation (e.g. from Plant Simulation 13 to Plant Simulation 14). However, if you save the model with a newer version of Plant Simulation, you will not be able to open it in the previous version of Plant Simulation anymore.