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在空间绳系拖曳变轨中,目标和平台形成一种哑铃型绳系系统,且仅依靠有限的平台推力和系绳张力来抑制系绳的摆动。针对此类输入受限的欠驱动控制问题,提出了一种利用受限张力的姿态稳定策略。首先,推导了组合体姿态动力学模型。然后通过数值求解姿态平衡方程得出理论面内姿态指令,再采用高斯伪谱法对其优化获得实际指令。最后,基于分层滑模理论设计欠驱动张力控制律,并嵌入抗饱和模块以缓解张力饱和。仿真表明空间平台能在正向有限的张力控制下,平滑地收放系绳使面内角和绳长跟踪实际姿态指令。此外,所提策略对目标体摆动和传感器误差也具有良好的鲁棒性。
In space tow orbit derailment, the target and platform form a dumbbell-type rope system and only rely on limited platform thrust and tether tension to suppress the tether swing. In order to solve this problem of under-driven control with limited input, a strategy of attitude stabilization using constrained tension is proposed. First, the kinematic model of the assembly is deduced. Then, the theoretical in-plane pose command is obtained by solving the attitude balance equation numerically, and then the Gaussian pseudospectral method is used to obtain the actual command. Finally, the under-actuated tension control law is designed based on the hierarchical sliding mode theory and the anti-saturation module is embedded to relieve the tension saturation. The simulation shows that the space platform can smoothly retract the tether and keep the in-plane angle and rope length to follow the actual posture command under the positive tension control. In addition, the proposed strategy also has good robustness to object swings and sensor errors.