Semi-analytical approach to trajectory optimization for stacker cranes regarding energy saving

The aim of this study is to give insights into the trajectory optimization with respect to energy consumption and recuperation for stacker cranes in a high-bay warehouse. Based on an analytical necessary optimality condition, a targeted numerical implementation is set up to perform systematic computations of optimal trajectories which are further categorized. Particularly, the differences between energy consumption and energy recuperation as well as for up and down movements are pointed out. Although examined for a concrete, experimentally validated model of stacker cranes, the methodical approach could be adapted to other electrical machines possessing a power flow model, that is a functional relation between the kinematics (velocity, acceleration and load mass for instance) and the resultant power. In addition, boundaries of the velocity, the acceleration and the jerk are incorporated. Such a systematic analysis of energy optimal trajectories can be further used for improving the job scheduling in a warehouse. • Energy consumption and energy recuperation are optimized and related. • Optimizing the trajectories saves about 10% of the energy on average, up to 32%. • The optimization is real-time capable due to the combination of analysis and numeric. • Optimal travels are categorized allowing fast decisions in scheduling and operation. • The approach is adaptable to other recuperative electrical drives.