Optimization of trajectory durations based on flow rate scaling for a 4-DoF semi-automated hydraulic rockreaker

In order to increase the overall efficiency of mines as well as improve worker safety, efforts continue to be made toward the automation of various mining operations. Rock breaking, whereby large pieces of ore are broken down into smaller pieces prior to being sent to a jaw crusher, is one such operation. In this paper, a trajectory planning algorithm destined for use in a semi-automated rockbreaker system is described. The algorithm's development is driven by the objective of minimizing the duration of rockbreaker motions. Paths between initial and final configurations are fully prescribed in the rockbreaker's task space to allow for the (future) seamless integration of collision detection algorithms. The time parameterization of these paths is then performed using motion profiles that ensure continuity at the acceleration level. Continuous flow rate scaling of the trajectory is applied in order to fully exploit the flow rate capacities of the rockbreaker's hydraulic pump and proportional valves, resulting in near time-optimal trajectories. The proposed trajectory planning algorithm is shown to lead to significant decreases in trajectory durations compared to other proposed approaches. (C) 2019 Elsevier Ltd. All rights reserved.