Dynamic Analysis Of Spherical Parallel Bionic Ankle Joint With 2-Dof Of Humanoid Robot

Humanoid robot is one of the most active branches in robot fields and it has been the hotspot and frontier problem in both of the international science and industry fields now. As an important part of humanoid robot, the existing bionic ankle joint mechanism has some deficiencies and defects, such as weaking carrying capacity, unbalanced stiffness, smaller workspace and lower level of bionics. Therefore, this paper provides and analyzes a new 2-Dof redundancy spherical parallel bionic ankle joint mechanism U_P+R+S from the perspective of the function structure bionic. It's highly similar with human ankle joint in structure form, motor function, stiffness balance and carrying capacity. Main contents of this paper are as follows:Based on the method of closed-loop vector, the kinematics model of the new bionic ankle joint mechanism U_P+R+S with three branch chains is obtained and analyzed. The forward and inverse kinematics model is obtained, the angular displacement of each branch chain is analyzed and the linear velocity and angular velocity of each chain link are built up. Using the human natural gait equipment of Xsens MVN, the human ankle joint posture information under the actual normal motion state was captured and the moving platform's output function was achived by using Fourier formula. The kinematics calculation lays a theoretical foundation for static stiffness analysis and dynamics analysis.Based on small deformation superposition principle, the static stiffness of the new bionic ankle joint mechanism U_P+R+S with three branch chains is obtained and evaluated. The flexibility matrix and stiffness matrix were obtained according to the relationship between moving platform's displacement deformation and loading force. The six principal stiffness and direction of this mechanism were achieved by orthogonal transformation method. The stiffness results are compared between the new bionic joint mechanism and the spherical parallel prototype UP+R. The work lies a foundation for engineering design and provides a technical theory support for choosing a better workspace.The dynamic real-time control model of the new bionic ankle joint mechanism U_P+R+S was established and analysized according to Lagrange method. The velocity, acceleration and inertial force dynamic performance indexs are calculated and analysized using systems condition number. In order to meet the dynamic control requirements of calculation precision, response speed and reduces the storage space,?1? the simplified energy equation of branch chain is obtained using the approximation principle of trigonometric functions,?2? the preliminary dynamic control model is derived,?3? the numerical analysis is carried out. It provides a technical and theorical guidance for system's dynamic real time control analysis.The virtual prototype of spherical parallel bionic ankle joint mechanism U_P+R+S is built up by using the SOLIDWORKS software, which is imported into ADAMS with x_t format to carry on the simulation experiment. The theorical calculated results of kinematics and dynamics model are compared with the simulation results.