Research On Design And Motion Performance Of Spherical Parallel Leg Mechanism For Quadruped Mobile Robot

There are abundant mineral resources in the bottom of the ocean,but it is impossible to carry out artificial exploration and exploitation.In order to meet the requirements of intelligent operation of seabed mineral resources exploration and adapt to the complex and changeable seabed environment,a quadruped mobile robot with spherical parallel mechanism for its legs is designed in this thesis.For this robot and its spherical parallel leg mechanism,analysis and research are carried out on the following aspects:Kinematics and dynamics modeling of spherical parallel mechanism of robot legs are carried out.Firstly,the degree of freedom of the mechanism is analyzed by screw theory,and its basic motion condition is obtained.Then,the mathematical mechanization solving process of forward and inverse position of the mechanism is given based on algebraic elimination method.The influence coefficient matrix of velocity and acceleration is obtained based on the influence coefficient method.Finally,the dynamic equation of the mechanism is obtained by Lagrange method.The analysis results provide a theoretical basis for subsequent trajectory planning and motion control.The stepping process of the stable and unstable gait of the robot model is analyzed,as well as the changing rules of center of gravity(COG)point and zero moment point(ZMP).Then,the COG points in the stable gait process are calculated,and the SLIP model is established.The dynamic equation and the specific coordinates of ZMP in the unstable gait are obtained.Then,the trajectory of the robot is determined to be a compound cycloid,and on the basis of the constraints established,the motion trajectory equation of the foot reference point in the swing phase and the supporting phase is solved.Finally,according to the established kinematics model and motion trajectory equation,the driving function of the driving branch chain is obtained,and its function change curve is obtained.Based on the limit boundary search algorithm,the workspace of the parallel leg mechanism of the robot is analyzed.On the basis of setting three constraints,the three-dimensional scatter plot of the workspace is calculated on MATLAB,and the maximum reachable space is a subset of spherical surface.Secondly,the singularity of the mechanism is analyzed and calculated from the two aspects of boundary singularity and internal singularity.The boundary singularity condition and the conclusion that there is no internal singularity position are obtained.Thirdly,the reciprocal of Jacobian matrix condition is used as a measure of dexterity,and the distribution characteristics of dexterity degree are analyzed.Finally,based on the finite element analysis method,the static stiffness and multi-mode of the mechanism are obtained by using ABAQUS software.The kinematics and dynamics models are compared and validated.The results show that the parameters curve obtained by the theoretical model basically coincides with the parameters curve obtained by the virtual prototype simulation.The correctness of the theoretical model is verified.Then,the PID control system is built on MATLAB/Simulink and simulated joiintly with ADAMS,and the optimal PID control parameters are determined.Finally,the experimental prototype of the robot is assembled and the motion control system is built.The single-leg walking motion of the robot is studied experimentally.The results show that the single-leg walking motion of the robot is stable and the actual working state is good.