Analysis of Load-Carrying Capacity for Redundant Free-Floating Space Manipulators in Trajectory Tracking Task

Qingxuan Jia,Yong Liu,Gang Chen,Hanxu Sun,Junjie Peng

doi:10.1155/2014/125940

Abstract

The aim of this paper is to analyze load-carrying capacity of redundant free-floating space manipulators (FFSM) in trajectory tracking task. Combined with the analysis of influential factors in load-carrying process, evaluation of maximum load-carrying capacity (MLCC) is described as multiconstrained nonlinear programming problem. An efficient algorithm based on repeated line search within discontinuous feasible region is presented to determine MLCC for a given trajectory of the end-effector and corresponding joint path. Then, considering the influence of MLCC caused by different initial configurations for the starting point of given trajectory, a kind of maximum payload initial configuration planning method is proposed by using PSO algorithm. Simulations are performed for a particular trajectory tracking task of the 7-DOF space manipulator, of which MLCC is evaluated quantitatively. By in-depth research of the simulation results, significant gap between the values of MLCC when using different initial configurations is analyzed, and the discontinuity of allowable load-carrying capacity is illustrated. The proposed analytical method can be taken as theoretical foundation of feasibility analysis, trajectory optimization, and optimal control of trajectory tracking task in on-orbit load-carrying operations.

Highlights

Space manipulators are playing increasingly important roles in space exploration
Considering the influence of maximum load-carrying capacity (MLCC) caused by different initial configurations for the starting point of given trajectory, a kind of maximum payload initial configuration planning method is proposed by using PSO algorithm
Simulations are performed to analyze load-carrying capacity of 7-DOF free-floating space manipulators (FFSM) when tracking a given straight line in Cartesian space. xb ini = [0, 0, 0, 0, 0, 0]T; initial pose of the end-effector is set as xe ini = [−4.55 m, −6.7 m, 7.85 m, 1.5 rad, 0, −3 rad]T, while the desired pose of the end-effector is xe des = [−2 m, −7.5 m, 4 m, 1.6 rad, −0.5 rad, −3 rad]T; the angular velocity and linear velocity of the end-effector are determined by conventional trapezoidal-velocity profile [21], in which the total time is set as 80 s and acceleration and deceleration times are both set as 20 seconds; Δt = 100 ms

Summary

Introduction

In particular for load-carrying operations of large structures during maintenance of satellites [1] and construction of space station [2], using space manipulators to replace astronauts can improve economy and security of on-orbit operations. Jia et al [7] and Liu et al [8] presented trajectory planning methodologies to achieve the goal of payload maximization, in which optimal joint trajectories were obtained to improve load-carrying capacity of FFSM in point-to-point motion. These studies only focused on optimization of dynamic performance for space manipulators and lacked intuitive and systematic analysis of load-carrying capacity

Objectives

Results

Conclusion