An analytical inverse kinematics solution with joint limits avoidance of 7-DOF anthropomorphic manipulators without offset

Abstract

The inverse solution calculation speed and the configuration control are very important for anthropomorphic manipulators with 7 degree-of-freedom (DOF). In order to realize the combined control of global arm configuration manifolds and local self-motion of 7-DOF anthropomorphic manipulators without offset, an analytical inverse kinematics solution method is proposed in this paper. By defining a new arm reference plane for 7-DOF anthropomorphic manipulators, it uses arm angle to deal with local self-motion and orientation control to deal with global arm configuration manifolds. All possible inverse kinematics solutions for target pose can be intuitively expressed with the assistance of the parameters of arm angle and orientation control. Meanwhile, the corresponding singularity is also taken into account and a detection metric is provided. Furthermore, the problem of joint limits avoidance is mapped to the selection of arm angle in null space, and the Self-Adaptive Particle Swarm Optimization algorithm is introduced to obtain the optimal arm angle that can maximize the avoidance of joint limits. Simulation results show the proposed method has such advantages as fast calculation speed, high precision and high stability.