Abstract: The strategy of parallel picking and compressible order accumulation makes the automated sortation system with double picking zones have a picking efficiency much higher than that with single picking zone. Based on this, the item assignment optimization problem is presented for this strategy. The principle of the strategy is introduced, which implies that the item assignment in two picking zones affects the performance of order compression and pre-picking time. A math model for this problem is established. The objective function is the negative sum of pre-picking time. This problem can be classified as a 0-1 programming problem and a max-min ant system algorithm is adopted to solve it. The example simulation and analysis prove the effectiveness of the algorithm.

Key words: Automated sortation system, Double picking zones, Max-min ant system, Parallel picking