Unified arm angle solution and obstacle avoidance strategy for the analytical inverse kinematics of SRS robots

Abstract

This paper proposes a novel analytical inverse kinematics method for the spherical–rotational–spherical (SRS) robot. The approach unifies arm angle representation within the null space, ensuring a unique arm angle corresponds to each overall posture. A complete framework is established to determine feasible arm angle intervals, alongside a global configuration selection strategy that avoids joint singularities by appropriate configuration choices. This enables precise control of specific postures. Additionally, an explicit relationship between the elbow joint position and the arm angle is derived, improving operation in constrained and obstacle environments. The rationality and accuracy of the method were validated in both MATLAB and C++ environments, and its practicality was demonstrated through tasks performed in constrained and obstacle-filled spaces implemented in V-REP.