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配置柔顺机构空间机器人双臂捕获卫星操作力学模拟及基于神经网络的全阶滑模避撞柔顺控制

MECHANICAL SIMULATION AND FULL ORDER SLIDING MODE COLLISION AVOIDANCE COMPLIANT CONTROL BASED ON NEURAL NETWORK OF DUAL-ARM SPACE ROBOT WITH COMPLIANT MECHANISM CAPTURING SATELLITE

  • 摘要: 讨论了空间机器人双臂捕获卫星操作过程避免关节冲击破坏的避撞柔顺控制问题. 为此在关节电机与机械臂之间设计了一种旋转 型串联弹性执行器(rotatory series elastic actuator, RSEA)--柔顺机构,其作用在于:(1) 通过其内置弹簧的拉伸或压缩变形来吸收捕获操作过程中被捕获卫星对空间机器人关节产生的冲击能量;(2) 可以利用合理设计的与之配合的避撞柔顺控制策略来保证关节冲击力矩受限在安全范围. 首先,利用第二类Lagrange方程分别建 立了捕获操作前含柔顺机构双臂空间机器人的开环分系统动力学模型与目标卫星的分系统动力学模型;之后,基于系统动量 守恒关系、闭链系统位置与速度几何约束关系,获得了捕获操作后空间机器人与被捕获卫星闭链混合体系统综合动力学方程; 最后,基于RBF神经网络提出了一种捕获操作后两者混合体系统镇定运动的全阶终端滑模避撞柔顺控制方案. 所提方案结合柔 顺机构在有效吸收、缓冲被捕获卫星冲击能量的同时,还在冲击能量过大时适时开、关空间机器人关节驱动器,以避免关节驱 动器过载、破坏;此外,还通过最小权值范数法分配了机械臂各关节力矩,以保证双臂协调操作. Lyapunov稳定性理论证明了 系统的全局稳定性,系统计算机数值仿真也验证了上述避撞柔顺控制策略的有效性.

     

    Abstract: The problem of collision avoidance compliance control for dual-arm space robot to protect joint due to impact in the process of capturing satellite is discussed. For this reason, a rotatory series elastic actuator (RSEA), a compliant mechanism, is designed between the joint motor and the manipulator. It has two functions: firstly, the impact energy of satellite to robot joints can be absorbed by RSEA's built-in spring through stretching or compressing in the capture operation; secondly, the impact torque of the joints can be limited in the safe range by reasonably designing a matching collision avoidance compliance control strategy. First of all, the dual-arm space robot with compliant mechanism open-loop subsystem dynamics model and the target satellite subsystem dynamics model are established before capture operation by the second Lagrange equation. Then, based on the momentum conservation and geometric constraints of the position and velocity of the closed-chain system, the closed-chain hybrid system of the space robot and the captured satellite is obtained after the capture operation. Finally, for calm control the hybrid system, based on RBF neural network, a full-order terminal sliding mode collision avoidance compliance control scheme is proposed. The proposed scheme not only can effectively absorb and buffer the impact energy in the capture operation, but can turn on or off the space robot's joint motor timely when the impact energy is too large, so as to avoid overload and damage of the joint actuator. In addition, the joint torques are allocated by the minimum weight norm theory to ensure the coordinated operation between manipulators. The global stability of the system is proved by the Lyapunov theory. At last, the effectiveness of the collision avoidance compliance control strategy is verified by computer simulation.

     

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