Petri Net Assignment 

General Information

  • The due date is Thursday 22 November 2012, before 23:55.

  • Submissions must be done via Blackboard. Beware that Blackboard's clock may differ slightly from yours.

  • The assignment must be made individually.

  • Grading will be done based on correctness and completeness of the solution. Do not forget to document your requirements, assumptions, design, implementation and modelling and simulation results in detail !

The assignment:

Petri Net modelling, simulation and analysis of a simple production system (using pipe 2)

You will use the Petri net tool pipe 2.

The system to model consists of a workshop producing/assembling products. The workshop produces two types of products: boxes and cylinders. For both types of products, the production consists of two stages: the body assembly and the lid assembly. Body assembly and lid assembly are performed by two dedicated machines. These machines are flexible enough to process either boxes or cyclinders. The machines will each, independently, strictly alternate between processing boxes and processing cylinders. As they work independently, the machines do not need to be synchronized. Initially, both machines are set to process boxes. It is assumed there is an infinite supply of raw material available. This supply must be modelled explicitly. The work pieces (initially, raw material, subsequently transformed into boxes/cylinders, and finally completed by adding a lid) are transported on pallets. There are a total of 6 pallets available. To transport one box workpiece (in all its incarnations: raw-box-box with lid), two pallets are needed. To transport one cylinder workpiece, only one pallet is required. Transportation is done between the two machines (body assembly and lid assembly). There is a limited ``buffer'' space between the two machines which can hold a maximum of 4 pallets (with workpieces on them). Finished products go to a storage area. The number of finished products must be explicitly modelled.

The assignment consists of three parts.

  1. Build and document a Petri Net model of this process.
  2. Perform a few simulation steps of this process and comment.
  3. Build the coverability graph for this Petri Net and run conservation analysis (note that spurious solutions may occur). This will allow you to draw some conclusions about:
    • boundedness;
    • deadlock;
    • reachability;
    • liveness;
    • persistence;
    • strict alternation of box and cylinder processing (both in body and in lid production);
    • utilization of pallets;
    • other insights derived from the conservation analysis.