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空间机器人双臂捕获卫星力学分析及镇定控制

MECHANICAL ANALYSIS AND CALM CONTROL OF DUAL-ARM SPACE ROBOT FOR CAPTURING A SATELLITE

  • 摘要: 随着航天技术的发展,空间机器人要求具有对非合作卫星的在轨捕获能力. 双臂空间机器人与单臂空间机器人相比在这方面显然更具有优势. 然而由于太空环境的复杂性,使得空间机器人双臂捕获非合作卫星操作过程的动力学与控制问题表现出下述特点:非完整动力学约束,动量、动量矩与能量传递变化,捕获前后结构开、闭环变拓扑,与闭环接触几何、运动学约束多者共存. 因此空间机器人双臂捕获卫星技术相关动力学与控制问题变得极其复杂. 为此,讨论了双臂空间机器人捕获自旋卫星过程的动力学演化模拟,以及捕获操作后其不稳定闭链混合体系统的镇定控制问题. 首先,利用拉格朗日第二类方程建立了捕获操作前双臂空间机器人的开环系统动力学模型,利用牛顿-欧拉法建立了目标卫星的系统动力学模型;在此基础上基于动量守恒定律、力的传递规律,经过积分与简化处理分析、求解了双臂空间机器人捕获目标卫星后受到的碰撞冲击效应,给出了合适的捕获操作策略. 根据闭链系统的闭环约束几何及运动学关系获得了闭合链约束方程,推导了捕获操作后闭链混合体系统的动力学方程. 最后基于该动力学方程针对捕获操作结束后失稳的闭链混合体系统,设计了镇定运动模糊H 控制方案. 提出的方案利用模糊逻辑环节克服参数不确定影响,由H 鲁棒控制项消除逼近误差来保证系统控制精度;通过最小权值范数法分配各臂关节力矩,以保证两臂协同操作. 李雅普诺夫稳定性理论证明了系统的全局稳定性. 最后通过数值仿真实验模拟、分析了碰撞冲击响应,并验证了上述镇定运动控制方案的有效性.

     

    Abstract: As the technology of space science develops rapidly, space robot system is expected to capture the noncooperative satellite on-orbit. Space robot with dual-arm obviously has more comparative advantage in this respect compared with the one with single arm. Because of the complicated condition in outer space it makes the dynamics and control problems related to satellite-capturing operation by space robot system with dual-arm to be extremely complicated, and there are some unique characteristics, such as, nonholonomic dynamics restriction, change of system configuration, transfer of linear momentum, angular momentum and energy, topology transfer from open to closed loop system, and the constraints of closed-loop geometry and kinematics during satellite-capturing operation. In this paper, the dynamic evolution for space robot with dual-arm capturing a spin satellite and calm control for unstable closed chain composite system are discussed. At first, with the Lagrangian approach, the dynamic model of open chain space robot with dual-arm before capture operation is established, and dynamic model of satellite is derived by Newton-Euler method. On that basis, based on the law of conservation of momentum and the law of force transfer, the impact effect after collision of space robot with dual-arm to capture the target is analyzed and solved by the process of integration and simplification, and the suitable capture operation strategy is given. Closed chain constraint equations are obtained by the constraints of closed-loop geometry and kinematics of closed chain system. With the closed chain constraint equations, the composite system dynamic model is derived. For the unstable closed chain composite system after the capture, the fuzzy H control scheme for calm motion is designed. The fuzzy logic system is applied to overcome the influence of uncertainty part and the robust H control item is used to eliminate the approximate error, to guarantee the tracking precision. The global stability of the system is proved by the Lyapunov theory. The weighted minimum-norm theory is introduced to distribute torques guaranteeing that the cooperative operation between manipulators. At last, numerical examples simulated the response of collision are used to verify the efficiency of the control scheme.

     

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