9-DOF Serial Robotic Arm for Space Environments and Its Inverse Kinematics Analysis*

In the context of long-term experiments within a space experimental module, the assistance of space robotic arms becomes crucial for astronauts. Considering the significant contributions of redundant robotic arms in various fields, a compact, hyper-redundant, and highly flexible robotic arm is designed for these space missions. To address the inverse kinematics problem for this specific structure, a C-IK algorithm is proposed, which combines the Non-Dominated Sorted Genetic Algorithm-II (NSGA-II) and Sequential Quadratic Programming (SQP) methods for multi-objective optimization. By modifying the algorithm's structure, C-IK retains global search capability, significantly improves runtime efficiency, and meets accuracy and continuity requirements. Experiments involving C-IK, NSGA-II, and an improved version of NSGA-II were conducted on 7-Degrees-of-Freedom (DOF), 8-DOF, and 9-DOF robotic arms to evaluate their performance. The results demonstrate that C-IK outperforms NSGA-II in terms of both algorithm runtime and accuracy, especially for the 9-DOF robotic arm, with the runtime reduced from over 37 seconds to just over 2 seconds and the accuracy increasing from less than 10% to higher than 95%. The findings highlight the significance of the proposed C-IK algorithm in achieving efficient and accurate inverse kinematics solutions for hyper-redundant robotic arms in space missions.