Research On Dimensional Synthesis And Dynamic Characteristics Of A Novel Spherical Parallel Mechanism

Humanoid robots have become one of the hot spots of research in the field of robotics,and as the core of the overall structure of humanoid robots and the carrier to realize the motion function,the performance of robot joints affects the overall motion performance and load-bearing capacity.It is of great theoretical significance and research value to design a bionic joint with low coupling,high stiffness and flexible control for the current problems of low stiffness,high coupling and difficult control of robot joints.In this thesis,a new asymmetric three-degree-of-freedom spherical parallel mechanism with semi-decoupling characteristics is proposed,and a systematic study on the semi-decoupling characteristics,kinematics and dynamics of the mechanism is carried out.The spherical mechanism is optimized and analyzed with the human hip joint as the application scenario.The main research contents of this paper are as follows.1.For the proposed new spherical parallel mechanism,the screw theory is used to analyze the degrees of freedom of the mechanism,the kinematic sub-coordinate system is established based on the D-H method,and the kinematic inverse and positive solutions of the mechanism are analyzed based on the vector method,and the kinematic positive and negative solution model of the mechanism is established.The kinematic analysis verifies the semi-decoupling characteristics of the mechanism,that is,one of the three kinematic branches independently controls the rotation of the moving platform around its own coordinate system in the Z-axis direction,and the other two branches control the rotation around the moving coordinate system in the XY-axis direction.2.The velocity and acceleration transfer relations from joint space to operation space are obtained based on the differential transformation method,and the velocity and acceleration Jacobi matrices of the mechanism are calculated.Based on the velocity Jacobi matrix,the singular dislocation of the mechanism is analyzed,the human hip joint is taken as the application scenario of the mechanism,the rod interference and singular dislocation are taken as the constraints of the mechanism,and the working space of the mechanism is drawn by boundary search method using MATLAB software.3.Combining the condition number of Jacobi matrix and the semi-decoupling characteristics of the mechanism,a full-domain mean dexterity performance evaluation index with coupling coefficients is proposed,and a multi-objective optimization function is established based on the new dexterity index and the workspace index of the mechanism.The performance is good.4.Based on the analysis of the velocity and acceleration of each member of the mechanism,the kinetic energy and potential energy of each member are calculated by the kinematic rotation,the Lagrange dynamics model of the mechanism is established,and the driving moment of the mechanism is solved in the form of numerical calculation by using MATLAB software.5.The ADAMS virtual prototype model of the mechanism is established,a typical motion trajectory is planned,and the kinematics and dynamics of the mechanism are simulated and analyzed.The ADAMS simulation results are consistent with the theoretical calculation results,which verifies the correctness of the virtual prototype model,mechanism kinematics model and dynamics model.Finally,a prototype of the spherical parallel mechanism was fabricated,a motion control program was written based on ZBasic language,and then a typical trajectory motion experiment was conducted for the mechanism.The proposed spherical parallel mechanism with semi-decoupling characteristics enriches the types of spherical parallel mechanisms,lays the foundation for the theoretical analysis of spherical mechanisms with decoupling characteristics,and provides a reference for the dimensional synthesis of decoupling mechanisms.