A Two-Stage Energy-Efficiency Optimization Approach for Conflict-Free Dispatching in Open-Pit Mines

Abstract

The objective of this paper is to present a novel energy-efficiency conflict-free dispatching algorithm for autonomous mining fleets. In lieu of halting or decelerating the trucks at intersections when conflicts arise, the algorithm facilitates conflict-free dispatching for trucks to operate with the optimal speed trajectory, thereby achieving minimum fuel consumption and mining cost. This work first develops reference speed trajectories for mining trucks, considering their drivetrain characteristics, load status and geographic information pertaining to the path. Second, the total production determination model is based on the MILP model, which determines the total production of each path while taking the travel time into account with the objective of maximizing fleet production. Next, in the fleet allocation model and conflict-free scheduling model, the objectives are to reduce the fleet make span and fleet queuing time, respectively. Finally, a fleet operation timetable is eventually derived. Therefore, all trucks can operate intact according to the speed trajectory, thus minimizing fleet energy consumption and maximizing production efficiency. To verify the advantages of the model in this work, we selected DISPATCH and a multi-objective dispatching model developed by other researchers for comparison on the basis of the historical production data from an open pit coal mine. The results indicated that the proposed model exhibited the capacity to decrease the fleet size by 22.2%, thereby attaining equivalent production levels to those of a real open-pit coal mining fleet. Moreover, the model proposed in this paper can improve the production by about 36.11% to 49.75% compared to DISPATCH under the optimal speed trajectory, whereas the multi-objective dispatching model's improvement is only 9.84% to 21.89%. It also has significant advantages in terms of fleet productivity and fleet profit.