Online Meat Cutting Optimisation

Nortura, Norway s largest producer of meat, faces many challenges in their operation. One of these challenges is to decide which products to make out of each of the slaughtered animals. The meat from the animals can be made into different products, some more valuable than others. However, someone has to buy the products as well. It is therefore important to produce what the customers ask for. This thesis is about a computer system based on online optimisation which helps the meat cutters decide what to make. Two different meat cutting plants have been visited to specify how the system should work. This information has been used to develop a program which can give a recommendation for what to produce from carcasses during cutting. The system has been developed by considering both the attributes of the animals and the orders from the customers. The main focus of the thesis is how to deal with the fact that the attributes are only known for a small number of the animals, since they are measured right after slaughtering. A method has been made to calculate what should be made from the different carcasses, and this method has been realised with both exact and heuristic algorithms

다목적함수 접근을 사용한 상태 기반 스케쥴링

학위논문(박사) - 한국과학기술원 : 산업및시스템공학과, 2013.2, [ vi, 81 p. ]Recently, semiconductor manufacturing fabs tend to reduce the wafer lot size, down to just a few. Consequently, the wafer recipe or wafer flow pattern changes frequently. For such problems it is impossible to apply conventional prevalent cyclic scheduling methods that repeat processing of wafers in an identical cyclic tool operation sequence. We therefore consider the non-cyclic scheduling problem encountered in cluster tool scheduling. In Chapter 2 we dealt with scheduling of single armed cluster tools. Single armed cluster tools have a simpler architecture than other configurations, but can be difficult to schedule when additional requirements such as re-entrant wafer flow, parallel chambers and multiple recipes are introduced. To solve these problems we proposed a method to transforms the problem into a multi-objective problem by considering the ready times of the resources as objectives to minimize. Only feasible states were generated based on the initial state of the system. These feasible states form a multi-objective shortest path problem and give us O((r+1)mn) as an upper bound for the number of states, where r, n, and m are the number of different wafer recipes, wafers, and processing chambers. We solved this problem with implicit enumeration by making our scheduling decisions based on the Pareto optimal solutions for each state. The experimental results showed that the proposed algorithm can quickly solve large sized problems including ones with arbitrary initial tool states, changing recipes, re-entrant wafer flows, and parallel chambers. In Chapter 3 we developed a general scheduling algorithm for Petri nets. Petri nets are widely used for modelling and analysis of discrete event dynamic systems and are therefore suitable for scheduling more complex cluster tool architectures such as dual armed cluster tools. We defined a data structure for noncyclic Petri net scheduling problems and then transformed the scheduling problem into an equivalent multi-...한국과학기술원 : 산업및시스템공학과

Online Meat Cutting Optimisation

Nortura, Norway\u92s largest producer of meat, faces many challenges in their operation. One of these challenges is to decide which products to make out of each of the slaughtered animals. The meat from the animals can be made into different products, some more valuable than others. However, someone has to buy the products as well. It is therefore important to produce what the customers ask for. This thesis is about a computer system based on online optimisation which helps the meat cutters decide what to make. Two different meat cutting plants have been visited to specify how the system should work. This information has been used to develop a program which can give a recommendation for what to produce from carcasses during cutting. The system has been developed by considering both the attributes of the animals and the orders from the customers. The main focus of the thesis is how to deal with the fact that the attributes are only known for a small number of the animals, since they are measured right after slaughtering. A method has been made to calculate what should be made from the different carcasses, and this method has been realised with both exact and heuristic algorithms