An Inverse Kinematic Optimization Method for the S-R-S Redundant Manipulator Considering Joint Limit and Singular Position Avoidance

Aiming at the problem of how to avoid the joint limit and singular position in continuous trajectory planning of the S-R-S redundant manipulator, a new inverse kinematics optimization algorithm is proposed in this paper. Firstly, according to the special geometry of S-R-S manipulator, we take the arm angle as the redundant parameter to obtain the joint angle expressions under the given tip pose and arm angle. Then we discuss the feasible arm angles under joint limit in nonsingular and singular cases, and give a complete method to obtain the effective arm angles. Finally, we introduce the concept of virtual force to represent the degree that the joint is far from the limit, and define the optimization objective function with the virtual force as the weight to avoid joint limit, the complex relationship between the arm angle and joint angles is linearized by the difference method to simplify the objective function to quadratic function, combine with the feasible arm angle range, we realize singularity avoidance and joint limit avoidance at the same time. The simulation result shows that compared with the traditional algorithm, the algorithm proposed in this paper has better joint limit avoidance ability on the premise of avoiding singularity which reflects the superiority of the algorithm and can be used for the motion planning of the manipulator in practical engineering.