Takayoshi Tamura

A Sequencing Problem to Level Part Usage Rates and Work Loads for a Mixed-Model Assembly Line with a Bypass Subline

Abstract To meet the diversification of consumers preferences, mixed-model assembly lines were installed in many manufacturing plants. For example, in the manufacturing of trucks, a large variation exists in assembly times among different product types. The large variation reduces production efficiency and may cause a line stoppage. The variation in the assembly times can be reduced by installing a bypass subline which processes a portion of assembly operations of products with relatively longer assembly times. This paper deals with a sequencing problem with a bypass subline. The sequencing problem with goals of levelling the part usage rates and work loads is formulated, and three different algorithms based on goal chasing method, tabu search and dynamic programming are developed to solve the problem.

New approximate dynamic programming algorithms for large-scale undiscounted Markov decision processes and their application to optimize a production and distribution system

Undiscounted Markov decision processes (UMDPs) can formulate optimal stochastic control problems that minimize the expected total cost per period for various systems. We propose new approximate dynamic programming (ADP) algorithms for large-scale UMDPs that can solve the curses of dimensionality. These algorithms, called simulation-based modified policy iteration (SBMPI) algorithms, are extensions of the simulation-based modified policy iteration method (SBMPIM) (Ohno, 2011) for optimal control problems of multistage JIT-based production and distribution systems with stochastic demand and production capacity. The main new concepts of the SBMPI algorithms are that the simulation-based policy evaluation step of the SBMPIM is replaced by the partial policy evaluation step of the modified policy iteration method (MPIM) and that the algorithms starts from the expected total cost per period and relative value estimated by simulating the system under a reasonable initial policy.

A Sequencing Problem in a Mixed-Model Assembly Line with Bypass Subline. To Level Part Consumption Rates and Work Loads.

There exists a large variation in the assembly times among different product models, for example, in the manufacturing of trucks and prefabricated houses. This reduces production efficiency and may cause a line stoppage. The variation of the assembly times can be reduced by installing a bypass subline which processes a part of assembly operations of products with relatively longer assembly times. Even if installing the bypass subline, both the part usage rates and work loads should be leveled by sequencing different products. In this paper, the sequencing problem with goals of levelling both the part usage rates and work loads is formulated as a nonlinear integer programming problem. Two algorithms based on dynamic programming and goal chasing method are developed to solve the problem and their efficiency is discussed through numerical examples.