Prioritized Multitask Flow Optimization of Redundant Hydraulic Manipulator

Abstract

For hydraulic redundant manipulators served by one pump, flow saving optimization can reduce flow saturation and energy consumption but primary tasks should be considered as a matter of priority, such as trajectory tracking and avoidance of joint limitation. In this study, a real-time redundancy resolution method is proposed for flow optimization, considering the primary trajectory tracking task and the hard joint constraints. All the joint constraints are involved in a velocity polytope, and a time-efficient polytope vertex solver is designed to obtain the velocity boundaries. The feasible task velocity that has a minimal tracking error is generated in a geometrical way considering the primary task and the hard constraints. The redundancy resolution method for flow optimization is then presented by calculating the intersection of the velocity polytope and the null space of the Jacobian matrix. Comparison tests are carried out on a 3-degree-of-freedom (DOF) planar hydraulic redundant manipulator for validation. The results show that the proposed method has the least flow consumption and smallest trajectory errors while meeting all hard constraints compared with the weighted least-norm method and the gradient projection method.