| This thesis presents the isotropic conditions for the H4 topological class of parallel manipulators with articulated travelling plate and four degrees of freedom. First, a kinematic model of this class of manipulators is developed, then we impose isotropic conditions on the jacobian matrix. From the newly obtained equations, design constraints and a design procedure permitting the determination of all isotropic geometries are obtained. The proposed design procedure allows the successive choice and calculus of all geometrical parameters of an isotropic manipulator of the H4 class. Moreover, the procedure always produces design. A genetic algorithm is used to find optimal isotropic geometries. The performance criteria are the volume of the workspace and the condition number of the jacobian matrix. The evaluation of each isotropic geometry during the optimization process is done in a discrete way by solving the inverse kinematic problem for a number of positions of the evaluated space. The best geometries found during the optimization process are shown. |
