Accuracy analysis of a novel humanoid robot shoulder joint

The shoulder joint is a typical ball and socket joint which have three degrees of freedom rotation. 3-DOF spherical parallel mechanism has the same structural feature with the shoulder joint. In this case the study of a 3-DOF shoulder joint is very interesting. In this paper, a novel humanoid robot shoulder joint based on 3-DOF spherical parallel mechanism is proposed. Accuracy analysis play an important role on the design and applications of the shoulder joint. The position and orientation error model is derived in closed forms by using differential theory. Error sensitivity evaluation index is defined based on mathematics method. Terminal platform error distribution is analyzed and discussed in detail by using the error model technique. The analytical results indicate the structure indices have great effection to the shoulder joint. So, this paper could provide a theoretical foundation for design and application of the shoulder joint for humanoid robot.