The Research Of Four Chains 3-DOF Spherical Parallel Bonic Hip With Bias Output

Humanoid robot is a class of intelligent robots which is resemble human body in the shape, structure, and function. It has become one of the most active branches of robotics. Bionic humanoid robot joint is the core of the body structure and the key to achieve function, whose performance will directly affect the performance of the entire humanoid robot and further expansion.The paper took a novel 3-DOF 3RRR+(S-P) spherical parallel bionic joint mechanism with a central spherical, bias output, high-statically indeterminate(over-constrained) as a research subject, did systematic research in the position, workspace, static stiffness and dynamics. All above provide new ideas and theoretical basis for further design and development of the bionic humanoid robot joints.The researchers established the mapping between the human and institutional space, and got the 3RRR+(S-P) bionic hip position inverse solution, considering the consistency of the workspace about the human joints and the mechanism and basing on 3RRR prototype mechanism inverse and forward solution. Meanwhile numerical calculation and analysis have been done.The paper also introduced the location, posture and motion range of human’s hip joint in detail, as well as the motion range and the interference of the mechanism. In this basis, compared the workspace of the human hip joint and determined the installation pose parameters of the mechanism in the joint humanoid robot body, taking the joint work space agency covering human hip joint actual motion space as a condition.The researchers used traditional split bar method and small deformation superposition principle to analyze the static stiffness of the high-statically indeterminate(Over-constraint) 3RRR+(S-P) bionic hip joint; obtained the diagonalizable stiffness matrix by numerical results. Comparing to the stiffness of 3RRR the research found that the introduction of the spherical center branched 3RRR+(S-P) linear displacement structure rigidity was enhanced, at the same time linear displacement and angular displacement stiffness were more balanced. Proved the novel three DOF spherical parallel bionic joint could satisfy the reality.In the basis of analyzing each component 3RRR+(S-P) speed and energy agencies, the Lagrange inverse dynamics model of the mechanism were established and a smooth drive torque expression was obtained. At the same time a numerical example to obtain a smooth drive torque curve, laying a theoretical foundation for the control.The author built a virtual 3RRR+(S-P) bionic hip joint with the mechanism and completed the dynamic and kinematic simulation using ADAMS. Comparative analysis of the external force and moment are stated between the prototype and the mechanism with the central spherical strut. Analysis found: force to 3RRR +(S-P) mechanism driving less affected; under the same load, 3RRR+(S-P) body can achieve the same trajectory in less driven, which demonstrates the advantages in dynamic performance about the novel 3RRR+(S-P) mechanism.