Analysis On Reconfiguration Principle And Coupling Characteristics Of Generalized Parallel Mechanisms

Because of the characteristics such as high stiffness, high precision and strong load capacity, the 6-DOF parallel mechanisms have been widely used in many fields. High stiffness plays an important role for parallel mechanisms ’ performance. However the exsitence of stiffness coupling in degrees of freedom becomes a limitation for improvement of precision. So stiffness decoupling have attacted many scholars’ attention. From the stiffness matrix, the decoupled matrix or the jacobian matrix is built relative to one point, called here the decoupled center. But away form that point, the coupling becomes severe. So for some applications in which high precision and low coupling is needed, the decoupled center(compliance center) is supposed to follow the movement of the end effector, because it will assure the robot has low coupling property in its’ global workspace.Pointed to decrease the stiffness coupling between diffenrent degree of freedoms, the research content is listed as follows:Studying the reconfiguration theory of a pair of circular hyperboloids of one sheet when constructiong a generalized parallel mech anism and the method of reconfiguration. First we raise out the reconfiguration principle of a pair of circular hyperboloids to achieve low coupling property through movement of a group of lower gimbal points and an anylitical reconfiguration algorithm when the movable platform moves along the Z axis or around the Z axis. Authenticating the algorithm through several numerical examples and getting some movement tragectories of lower gimbal points. Analyzing the relationship between the shape of tragectories and the related parameters.Studying how the parameters of a pair of circular hyperboloids influence the property indexes of a generalized parallel mechanism. Analyzing how the parameters influence the condition number of the Jacobians. Giving a definition of coupling index. Analyzing and evaluating how reconfiguration of a pair of hyperboloids influences the range of low coupling movement of a parallel robot.