Robust control of a dual-arm space robot to capture a non-cooperative target in 3D space

Non-cooperative objects in space, like defunct spinning satellites, are potentially dangerous to subsequent space missions. Thus, this paper proposes a new capture strategy by a dual-arm space robot to improve the efficiency of the capture operation. Compared with single-arm space robots, dual-arm space robots can carry out more complex missions, like capturing a spinning target in three-dimensional (3D) space, with a higher probability of success. Considering the possible model uncertainties of a space robot and a non-cooperative target, a sliding mode controller (SMC) with good robustness against the model uncertainties was developed. However, due to frequent switches in the controller, the SMC usually has chattering effects causing uncontrolled vibrations of the spacecraft structure. For comparison, a smoothed quasi-continuous second-order sliding mode controller (SQC2S) can provide the same high accuracy level as the SMC and remove the chattering effects caused by the SMC. In addition, the SQC2S can deliver better robust performance against the model uncertainties than the SMC. Finally, the proposed capture strategy is validated and compared in the numerical simulations by the SMC and the SQC2S.