Accelerating Numerical Inverse Kinematics Methods with the Lookup Table

• Main Authors: Chan, Li-Wei, Ho, Chi-Kai, King, Chung-Ta
• Format: Conference Proceeding
• Language: English
• Subjects: Computational complexity; End effectors; Inverse kinematics; Iterative methods; Kinematics; numerical optimization; Optimization; redundant degree-of-freedom; robotic manipulator; Table lookup
• ISSN: 2379-1896
• DOI: 10.1109/CANDAR57322.2022.00010

Inverse kinematics (IK) for a robotic arm solves for the joint variables to move its end-effector to a target position with an optional orientation. IK can be solved by iterative numerical methods. However, as the degree-of-freedom (DoF) of the robotic arm increases or the applications impose extra constraints, the iterative process will be lengthened dramatically. In this paper, we study the idea of using a lookup table to accelerate the numerical IK methods. Given a target position, the table outputs a joint configuration that can move the end-effector to a position near the target, from where the numerical method can start the iterative process. This significantly decreases the number of iterations and the time in solving IK. In addition, extra constraints of the applications can be checked after table lookup, instead of "formulating into" the numerical formulations. This further simplifies the formulations and reduces the computation complexity. The proposed lookup table only needs to be built once when the robotic arm is developed and can be coupled with any numerical IK methods. Experiments based on the IKpy package show that the proposed method can accelerate different numerical IK methods up to 33% if only end-effector position is required and to 70% if both position and orientation are required.