In this paper, a simple and straightforward visual graphic approach for mobility and singularity analysis of mechanisms is introduced. Although the proposed method is established upon the reciprocal screw system theory, it needs no formula derivation instead knowing about a few simple rules. As a study case, mobility and singularity analysis for a class of two degrees-of-freedom (DOF) rotational parallel mechanisms i.e. well-know Omni-Wrist III with four limbs, and its two derived architectures with three limbs (named T-type and δ-type) is analyzed by the proposed method. As a result, a novel PKM derived from Omni-Wrist III is presented, which has the DOF and kinematics property close to Omni Wrist III.

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Electromagnetic railgun launch system is the part designed for launching projectile. The dynamic properties of the launch system contribute to the firing accuracy. This paper models the finite element model of a square-shaped railgun. The Ansys ACP module is used to design the layer of carbon fibre barrel of the railgun. Modal analysis of the launch system is performed using Ansys. On this basis, the modal superposition method is used to calculate the dynamic response of the launch system caused by the electromagnetic expansion force during launching. This paper analyses the steel encapsulation barrel as a comparison and verifies the rationality of using the composite material. The results provide support for the engineering design of electromagnetic railgun.

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