This paper deals with the kinematic calibration of a 3-DOF parallel mechanism using a double-ball-bar (DBB) system. The mechanism forms the main body of a 5-DOF reconfigurable hybrid robot named TriVariant that is a modified version of the Tricept, achieved by integrating one of its three active limbs into the passive one. The first order error mapping function is formulated to link the measured data and the geometric source errors affecting the compensatable pose accuracy. Issues to enhance the accuracy and efficiency of the calibration are investigated. The results are employed to a prototype machine calibration

This paper deals with the finite element analysis (FEA) of two 5-DOF reconfigurable hybrid robots, the Tricept and the TriVariant, by means of ANSYS parametric design language (APDL). The research interests are focused on: (1) precise FEA formulation of different types of joints by setting of contact elements, and (2) the development of an effective modeling strategy for the rapid stiffness and natural frequencies estimation associated with different configurations. The computational results show that two robots are of similar static and dynamic performances provided that they have identical geometrical dimensions, elastical and inertial parameters

This paper deals with the tolerance design of a two-degree-of-freedom translational parallel robot module for high-speed pick-and-place operations. The module is an overconstrained parallel mechanism using two sets of parallelograms in each limb. A probabilistic model of the uncompensatable pose error is formulated, together with a compatibility condition to ensure the mobility of the robot. Based upon this model, optimization of the tolerances of the geometric source errors and joint clearances is conducted, subject to a set of appropriate constraints. Simulation and experimental results are given to demonstrate the effectiveness of this approach.

This paper deals with the conceptual design and dimensional synthesis of a 3-DOF parallel mechanism module which forms the main body of a newly invented 5-DOF reconfigurable hybrid robot named "TriVariant." The TriVariant is a modified version of the Tricept robot, achieved by integrating one of the three active limbs into the passive limb. The idea leading to the innovation of the module is systematically addressed. Its kinematic performance is optimized by minimizing a global and comprehensive conditioning index subject to a set of appropriate mechanical constraints. It is concluded that the proposed hybrid system is more cost-effective and has a competitive kinematic performance in comparison with the well-known Tricept robot.

This paper presents a simple yet comprehensive approach that enables the stiffness of a tripod-based parallel kinematic machine to be quickly estimated. The approach can be implemented by two steps. In the first step, the machine structure is decomposed into two substructures associated with the machine frame and the parallel mechanism. The stiffness model of each substructure is formulated by assuming that the components in the other substructure are rigid. This is followed by the second step that enables the stiffness model of the machine structure to be achieved by linear superposition. A 3D representation of the stiffness distributions within the usable workspace are depicted with comparison to those obtained through the finite element analysis.