Human Resource Allocation for Parallel Assembly Processes with Temporal and Spatial Constraints

Human resource allocation in parallel assembly processes (PAPs) is an important optimization problem. It can be regarded as a resource-constrained project scheduling problem with specific constraints. In this paper, a mixed-integer programming (MIP) model is established for it to minimize the maximum completion time (i.e., makespan) by comprehensively analyzing the characteristics of a PAP, including temporal constraints: worker periodic unavailability and the tail time of operations; and spatial constraints: workstation and human resource constraints. To address this problem, a heuristic rule for prioritizing idle workers that considers the precedence relationships of operations is designed as a baseline method, and an iterative greedy algorithm is further proposed to provide high-performance solutions. These methods aim to shorten the cycle and costs of a PAP. The effectiveness of the proposed algorithms is validated through extensive experiments.