The Inverse Kinematics Solutions of Robot Manipulators with Offset Wrist Using the Offset Modification Method

It is no closed-form solutions for 6R robot manipulators without three consecutive joint axes parallel or three adjacent joint axes intersected a common point. In this paper, the offset modification (OM) method was applied to solve the inverse kinematics problem of these types of manipulators which didn’t have closed-form solutions. A robot manipulator model of TA1400 with offset wrist was built by the OM method. And then three nonlinear equations were derived from the difference between the forward kinematics equations of the model robot manipulator and the TA1400 manipulator. Eight sets of inverse kinematics solutions of TA1400 were obtained by the three nonlinear equations with the fixed-point and the Steffensen iterative method. The results show that the orientation errors of the eight sets of solutions are all less than 10

− 15

and the position errors are less than 10

− 4

mm, which meet the requirements of the industrial robot’s positions and orientations precision. The assembly experiments of TA1400 in ADAMS show that curve of each joint angle are smooth and continuous using the OM method. These results and experiments proved that the offset modification method can be applied to solve the inverse kinematics of industrial robot manipulators with front offset wrists.