Energy Efficiency Improvement of Hydraulic Manipulator Through Flow-Optimal Redundancy Resolution With Path Following

For hydraulic manipulators, utilizing the redundant degrees of freedom to optimize the allocation of pump flow is beneficial for the reduction of energy consumption. However, a higher priority task should be considered to follow the reference path under the constraints of actuators and pump. A hierarchical redundancy resolution method is proposed in this study for real-time flow optimization of redundant hydraulic manipulator, which takes into account the path following task under constraints of flow, position, velocity, and acceleration. A constraint reconstruction method is proposed to determine the hard constraints while eliminating redundant ones, such that the computational efficiency is improved. The tasks of path following and flow optimization are addressed hierarchically. Moreover, a feasible region partitioned solution algorithm is designed to simplify the flow optimization problem with a non-smooth cost function into linear programming sub-problems. Four sets of comparative tests under different paths and speeds are carried out on a redundant hydraulic manipulator. The results show that the proposed method enables the hydraulic manipulator to execute tasks accurately and efficiently in real-time. Note to Practitioners—This work was motivated by the need to develop an efficient computational method for reducing the energy consumption of redundant hydraulic manipulators while following a reference path under the constraints of the actuators and pump. The objective was to operate the manipulator effectively and accurately in real-time. In this article, a hierarchical redundancy resolution method is proposed to reduce energy consumption by optimizing pump flow allocation, while considering the path following task and hard constraints. It is different from the off-line methods that pre-planning the trajectories before execution in a structured environment. A constraint reconstruction method and a feasible region partitioned solution algorithm are designed to accelerate the solution procedure. The proposed method enables the hydraulic manipulator to execute the given reference path accurately and energy efficiently in real-time. Energy consumption optimization considering dynamic constraint boundaries and hydraulic system pressure needs to be further investigated.