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The topological structure synthesis and optimization of 1T2R parallel mechanisms was studied herein. Applying the composition principles and constraint characteristics of planar mechanisms, the topological structure of 1T2R parallel mechanisms was regarded as consisting of a 1T1R planar parallel kinematic chain connected in series with a revolute joint and two spatial unconstrained active limbs. Then the topological structure optimization and performance verification of 1T2R parallel mechanisms were carried out by comprehensively considering the criteria such as appropriateness of mechanism's pose capability, rationality of branch-chain structure mechanics, reconfigurability of robot module, simplicity of position inverse solution, and compactness of moving platform structure,etc. Then, a new five-degree-of-freedom hybrid robot module that may inherit the advantages of Tricept robots was proposed. The module has exactly the same kinematics performance as Tricept robots, and most of the components may be interchanged with Tricept robots. [ABSTRACT FROM AUTHOR]

The trajectory-planning method for a novel 4-degree-of-freedom high-speed parallel robot is studied herein. The robot's motion mechanism adopts RR(SS)2 as branch chains and has a single moving platform structure. Compared with a double moving platform structure, the proposed parallel robot has better acceleration and deceleration performance since the mass of its moving platform is lighter. An inverse kinematics model of the mechanism is established, and the corresponding relationship between the motion parameters of the end-moving platform and the active arm with three end-motion laws is obtained, followed by the optimization of the motion laws by considering the motion laws' duration and stability. A Lamé curve is used to transition the right-angled part of the traditional gate trajectory, and the parameters of the Lamé curve are optimized to achieve the shortest movement time and minimum acceleration peak. A method for solving Lamé curve trajectory interpolation points based on deduplication optimization is proposed, and a grasping frequency experiment is conducted on a robot prototype. Results show that the grasping frequency of the optimized Lamé curve prototype can be increased to 147 times/min, and its work efficiency is 54.7% higher than that obtained using the traditional Adept gate-shaped trajectory. [ABSTRACT FROM AUTHOR]

SUMMARY: This paper proposes a set of novel indices for evaluating the kinematic performance of a 3-RRS (R and S denote revolute and spherical joint respectively, R denotes active joint.), parallel mechanism whose translational and rotational movements are strongly coupled. First, the indices are formulated using the decoupled overall Jacobian matrix, which is developed using coordinate transformation. Then, the influences of the homogeneous dimensionless parameters on these indices are investigated. In addition, the dimension synthesis of the 3-RRS parallel mechanism is carried out by minimizing the mean value of the kinematic performance indices and their standard deviation. The results demonstrate that the established approach facilitates good global kinematic performance of the parallel mechanism. [ABSTRACT FROM AUTHOR]