This paper deals with the shape optimization of a six degree-of-freedom haptic interface device. This six-dof epicyclicparallel manipulator has all actuators located on the ground. A regular dexterous workspace is introduced to represent the mobility of user's hand. Throughout this workspace, the deviation of the mobile platform is bounded to provide a better feeling to the user and the masses in motion are minimized to increase the transparency of the haptic device. The stiffness model is written using a virtual joint method and compared with the results obtained with the finite element analysis to be validated. Finally, the shape of the links are optimized in order to minimize the masses in motion while guaranteeing a given stiffness throughout the regular workspace of the mechanism.
INTRODUCTIONThere is a large number of parallel manipulators, which have been reported over the past three decades. They can be divided into three-dof, four-dof, five-dof and six-dof parallel manipulators [1][2][3][4]. In three-dof parallel manipulators, there are three-dof translational parallel manipulators [5][6][7], three-dof rotational parallel manipulators [8,9] and three-dof parallel manipulators with mixed (translational and rotational) motion capabilities [10,11]. Among the four-dof parallel manipulators, examples include the four-dof four-URU parallel mechanism [12] and the Schönflies-motion generator [13]. There are also fivedof parallel manipulators, such as the 3T2R parallel manipulators [14][15][16]. For six-dof manipulators, the number of all possible architectures can be extremely large [17]. Six-legged six-dof parallel manipulators, such as the Gough-Stewart platform, have