In this thesis, a visual approach for the dimensional synthesis of planar parallel manipulators is discussed. The presented approach transforms the kinematic constraint problem to a geometric constraint manifold manipulation problem. For planar mechanisms, the kinematic constraint equations represent the limits for the motion of the links in the Cartesian space. The use of Quaternions is made in designing of this motion. The problem of motion of planar mechanisms is translated into a problem of designing of a smooth rational curve in the Quaternion space (Image space). An intuitive graphical design tool has been developed. The design tool facilitates the user for synthesis of planar parallel manipulators. The design problem has been transformed into a problem of manipulation of surfaces so as to contain the curve in the volume between the surfaces, yielding the desired mechanism.