Kinematic analysis of a novel 2P4R 6DoF manipulator of 9DoF heavy duty arm having less average error than 6R 6DoF

Abstract High-radiation environments within fusion reactors, such as the complex internal structure of the divertor, necessitate remote maintenance with extreme precision. Even minor errors from the robotic manipulators can lead to catastrophic cost overruns and prolonged reactor down-time. While heavy duty 9DoF arm provides reach, its inherent scale introduces significant errors, necessitating a highly accurate multi-joint end effector. This paper addresses the critical challenge of error reduction in this final manipulator by proposing a novel 2P4R kinematic architecture. Through rigorous theoretical analysis and simulation, we demonstrate that the strategic placement of prismatic joints minimizes the number of active errors contributing joints during typical trajectories. A comparative study against a conventional 6R manipulator on the same path confirms that the proposed design achieves a substantially lower cumulative Cartesian error. The results conclusively show that this kinematic configuration provides an inherent advantage in achieving the sub-millimeter accuracy required for fusion reactor maintenance.