Lecture 7: DES Flashcards
What are the two types of Systems?
- Discrete
- system where status variable change instantenously at discrete intervals of time
- > IT systems, manufacturing system, traffic regulation systems - Continous
- status variables change continously during time of simulation
- > flow of fluids heat
What is the difference between analytical and experimental models?
→ simple systems can u can use mathemtical models (algebral, calculus, or linked to probability)
→ if its too complex (to many variables having interdependancies) u need experemental models throught simulation
Explani deterministic and stochatic models
- Deterministic
- no uncertainty in simulated phenomena (e.g. customers arriving at regular times) - Stochastics
- correlation between variables and probabilities
Types of Simulations
- Statis vs Dynamic
→ does time play a role? (do some parameters change in generell) - Continous vs Discrete
→ do changes take place continously or instantenously at certain points - Deterministic vs Stochastic
-is there randomness in the inputs or operations of the model (how likely is it for a mashine to go out?)
What is SImulation
→ Simulation is the imitation of the operation of a real-world process or system over time.
→ Computer simulation is a methode where experiments are conducted on a computer in order to tecreate over time the functioning of a system
→ experimental tequnique allows to predict the behaviour of a system under certain conditions that most likely will manifest while the system
→
Whats the function of Simulation?
→ recreate behaviour of a system over an extended period of time, in a shorter time
input X → model → output Y
How does Simulation supports in the industrial sector?
- Desgin of new systems/solution (e.g. factory)
- improvment of actual systems/solutions
- Performance analysis (e.g. productivity, bottlenecks, resources saturation)
- WHAT-IF analysis (new order from customer into system)
- Training
What are Discrete event systems? + Examples
→ dynamic systems (over time) which update their values only at discrete number of points
- no continously changing states are of importance
Examples: call center, gas station, restaurant factory, warehouse
(restaurant: customers enter at certain time, they sit at certain etc.)
What is the Approach of DES
- focus on times between events
- with full knowledge we can update the system only at this specific time point
- full info about history, cause nothing happened between t1 and t2
What is an Entity of DES?
-thing with distinct and temporary existence that passes through a system (e.g a piece that should be assemblet, client to the bank office)
→ created to simulate a process and then destroyed
What is a Resource of DES?
thing with active and permanent existence that provides a service to entities (e.g. machine tool, conveyor, a banker, …)
What is a queue of DES?
a thing with temporary and passive existence that is formed by entities which are waiting for a resource (that is not free at that time).
→ always there, but can be empty or full, so temporary
What are Variable and Attributes of DES?
data and information about entities or resources (e.g. warehouse capacity, cycle time).
What is the Status of DES?
Description of all the values attributes of an entity or a resource, in a specific instant of time.
What is an event in DES?
Instant of time in which the model status is changing (change of status of entity or resource).
