Three Degrees Of Freedom Rotation Angle Type Synthesis And Analysis Of Pyramid Mechanism

Three degrees of Freedom Parallel mechanism has many advantage,such as larger inflexibility,higher bearing load capacity,higher precision,simple structure,low cost of manufacture and maintenance, in particular where the same branch, the symmetrical structure of three degrees of freedom parallel mechanism more attention of scholars. Three degrees of freedom parallel mechanism has become one of the focuses in the field of organization, which also has broad application prospects in the industrial field. Based on the theory of reciprocal screw completed a rotation angle of three degrees of freedom table mechanism kinematic chain branches were integrated type, according to the structural requirements pyramid mechanism and the requirements of full-cycle mobility, get the branch kinematic pair as little as possible with three degrees of freedom rotation pyramid mechanism.In the first, the structure features 3-RRS pyramid mechanism is introduced, the link coordinate system is created by the D-H method and the transformation matrixes of the pyramid mechanism are described, the functions of the direct problem and the inverse problem are established. Solving inverse position, using the method of Least squares, Newton’s method and the analytical method are used for solving the direct problem of the position analysis, through the simulation software to obtain the workspace of the mechanism. On the basis of the position analysis, The Jacobian matrices of velocity and acceleration of the pyramid mechanism are obtained by the method of derivation and the theory of spiral, get-ting The relationship of the velocity and acceleration of input and output.By using the virtual work principle to obtain the force Jacobian matrix of the mechanism, To establish the dynamic equation model of the mechanism based on Newton Euler method and the kinematics and dynamics simulation of The 3D model have accomplished by Adams software. By comparing the simulation results and theoretical analysis to verify the correctness of the kinematics and dynamics analysis.The instantaneous motions of the 3-RRS pyramid mechanism are analyzed and the principal screws in the initial position and general position are identified by means of the conic section and the quadric degenerating theory, the relations between the pitches of the output spiral and the velocity inputs are described, and the spatial distribution of the axes of all the twists with the same pitch is illustrated in every configuration. The conclusion is that the mechanism belong to the first kind of special spiral of three-system in the initial position, while it belong to the general third-order screw system in the general position, the axes of all the screws with the same pitch lie in a hyperboloid.