It is known that two primary disadvantages of parallel manipulators are the complicated forward kinematics and limited workspace. This paper mainly addressed the kinematics and workspace analyses of a 3/3-RRRS 6-DOF parallel manipulator. After a brief introduction of the 3/3 -RRRS 6-DOF parallel manipulator, a three-dimensional model and its relevant structure diagram are constituted, the forward and inverse displacement analyses of the 3/3-RRRS parallel manipulator are discussed in detail, especially, a novel geometrical method referred as equivalent mechanism is proposed for the forward displacement analysis of the manipulator under consideration. Based on the displacement analyses of the manipulator, a discretization method is proposed for the computation of the reachable position/orientation workspace of the 3/3-RRRS parallel manipulator, respectively. Examples of a 3/3-RRRS parallel manipulator are given to demonstrate these theoretical results.

This paper mainly addresses the principle of the singularity elimination of the Stewart parallel platform. By adding appropriate redundant actuation, the rank of the Jacobian matrix of the parallel platform is always full, accordingly the singular value of the Jacobian matrix of the parallel platform is nonzero. Then the singular configuration of the parallel platform can be eliminated by adding one redundant actuation. Numerical examples are taken to illuminate the principle’s effectiveness. It is shown that not only singular configurations of the Stewart parallel platform can be eliminated, but also performances of kinematics and dynamics of the parallel platform can be greatly perfected by adding appropriate redundant actuation.

Copper is widely used in the power industry due to its good electrical conductivity. However, owing to its low hardness and resistance to abrasion, copper is prone to damage when working under harsh environmental conditions. In order to protect the power equipment and improve the surface strength of the material, this study explores the feasibility of using laser cladding technology to prepare a protective layer on the copper substrate. The phase, microstructure and element distribution of the cladding layer were analyzed, and the changes in the microhardness of the cross-section were measured. The wear resistance of the two cladding layers was tested and compared with the wear resistance of pure copper. The experimental results show that the cladding layer has uniform structure distribution, fine grains, and no element segregation; the hardness of the cladding layer is greatly increased, and the average hardness of the CuCr20 cladding layer is 155.8 HV, which can reach 2.2 times that of the substrate. The average hardness of the CuCr40 cladding layer is 254.4HV, which can reach 3.6 times that of the matrix. The wear resistance of the CuCr40 cladding layer is higher than that of the CuCr20 cladding layer, which can reach three times that of pure copper. Experiments have proved that the protective effect can be achieved by preparing a laser cladding layer on the surface of pure copper.