Global Energy-Optimal Redundancy Resolution of Hydraulic Manipulators: Experimental Results for a Forestry Manipulator

Abstract

This paper addresses the energy-inefficiency problem of four-degrees-of-freedom (4-DOF) hydraulic manipulators through redundancy resolution in robotic closed-loop controlled applications. Because conventional methods typically are local and have poor performance for resolving redundancy with respect to minimum hydraulic energy consumption, global energy-optimal redundancy resolution is proposed at the valve-controlled actuator and hydraulic power system interaction level. The energy consumption of the widely popular valve-controlled load-sensing (LS) and constant-pressure (CP) systems is effectively minimised through cost functions formulated in a discrete-time dynamic programming (DP) approach with minimum state representation. A prescribed end-effector path and important actuator constraints at the position, velocity and acceleration levels are also satisfied in the solution. Extensive field experiments performed on a forestry hydraulic manipulator demonstrate the performance of the proposed solution. Approximately 15-30% greater hydraulic energy consumption was observed with the conventional methods in the LS and CP systems. These results encourage energy-optimal redundancy resolution in future robotic applications of hydraulic manipulators.

Analytical, Experimental, and Numerical Investigation of Energy in Hydraulic Cylinder Dynamics of Agriculture Scale Excavators

“…Regarding model-based control of hydraulic machinery, the paper analyzes energy behaviors in hydraulic cylinder dynamics from the port-Hamiltonian point of view, which provides many links to model-based control at laboratory scale at least [12,13]. Note that the analyzed energy in this paper is not the global energy (e.g., [14][15][16][17]) defined for the whole hydraulic machinery but just one of the local energies defined for each joint whose analysis is still open [18] and critical for better understanding of the whole hydraulic machinery eventually. To the best of our knowledge, however, on agricultural scales that should be larger than the laboratory scale, such local energy is mainly analyzed in terms of statics [1] and is not fully analyzed in terms of dynamics.…”

Globally Optimal Inverse Kinematics Method for a Redundant Robot Manipulator with Linear and Nonlinear Constraints

“…Zhou and Guyen [6,7] presented an algorithm based on the Pontryagin Maximum Principle and state space augmentation method to either handle joint limits or the periodicity of the trajectory. Nurmi et al [8] used instead a penalty in the integral cost function to solve the problem of minimizing energy while tracking a trajectory with limits on joint displacements, velocities, and accelerations. Lyu et al [9] exploited Sequential Quadratic Programming (SQP) to minimize time and energy consumption with constraints on joints displacement, velocity, acceleration, and jerk.…”

Simulation-based comparison between two crane-bunk systems for loading work when considering energy-optimal motion planning

“…Although being crucial for improving performance, there is little research published on optimizing forestry cranes. Some studies exist in the area of automation, where researchers developed and applied control systems and purpose-built algorithms in an attempt to demonstrate methods that can facilitate and improve work with forestry cranes (Fodor et al, 2016;Ortiz Morales et al 2014;Kalmaria et al 2017;Nurmi and Mattila 2017). Other research has considered the performance of such control systems and algorithms (Manner et al 2017).…”