An Optimization-Based Approach for Design Project Scheduling

Abstract

Abstract-Concurrent engineering has been widely used in managing design projects to speed up the design process by concurrently performing multiple tasks. Since the progress of a design task often depends on the knowledge about other tasks and requires effective communication, tasks and communication activities need to be properly coordinated to avoid delays caused by waiting for information or the need for rework. This paper presents a novel formulation for design project scheduling with explicit modeling of task dependencies and the associated communication activities. General dependencies are modeled as combinations of three basic types representing sequential, concurrent, and independent processes. Communication activities are also modeled as tasks, and their interactions with design tasks are described by sets of intertask constraints. The objective is to achieve timely project completion with limited resources. To improve algorithm convergence and schedule quality, penalties on the violation of constraints coupling design tasks are added to the objective function. A solution methodology that combines Lagrangian relaxation, dynamic programming, and heuristic is developed to schedule design and communication tasks, and a surrogate optimization framework is used to overcome the "inseperability" caused by nonadditive penalties. A heuristic procedure is then developed to obtain scheduling policies from optimization results and to dynamically construct schedules. Numerical results show that the approach is effective to handle various task dependencies and the associated communication activities to provide high-quality schedules.Note to Practitioners-A short product design cycle is critical for manufacturers to succeed in the era of time-based competition. To speed up the design process, concurrent engineering has been widely used where multiple design tasks are concurrently performed. As a design task can be performed with preliminary or partial information on other tasks and the information may be updated, effective communication is required. If design and communication activities are not properly coordinated, the project may be significantly delayed by waiting for information or by the need for rework. This paper presents a novel formulation for design project scheduling by appropriately modeling task dependencies and the associated communication activities. A solution methodology based on decomposition and coordination is developed to schedule both design and communication tasks to achieve timely project completion. Numerical results show that the approach is effective to handle various task dependencies and the associated communication activities to provide high-quality schedules.