The Economic Lot Scheduling Problem (ELSP) is the problem for determining the production
schedule of many products to single production facility where the setup times, production and demand rates of
each product are different. Due to its practical importance in the field of production and inventory
management, this problem has been attracted many researchers and lead to many problem variants. Some
exact and heuristics approaches had been proposed in the past for solving the ELSP and its variants, however,
each approach is usually intended to solve a particular ELSP variant. This paper tries to develop a new and
unified solution methodology for solving the ELSP and its variants using the particle swarm optimization,
especially by proposing the solution representation and its decoding method. The computational results show
that the proposed algorithm is able to find good solution of ELSP.