Research on contact characteristic of a manipulator configuration with adjustable finger pad curvature for grasping the fragile thin-walled cylindrical inner wall workpiece with radii changed

To solve the problem of grasping the fragile, thin-walled cylindrical inner wall workpiece with different radii by using the same manipulator, a kind of manipulator configuration is put forward in this paper. The manipulator comprises an external cylindrical palm and a grasping finger system installed in the palm. The key to a structure is that an adjustable finger length and an adjustable finger elastic regulating plate are designed. For the curvature of the adjustable finger elastic adjustment plate, the effects of different adjustment point distributions on the fitting accuracy of gripping workpiece surfaces are discussed, including the adjustment point arrangements with equal-interval interpolation distributions and Chebyshev interpolation distributions. Furthermore, under different fitting accuracy of the grasped workpiece surface, for analyzing the contact force between the manipulator finger working surface and the workpiece surface, the finite element model is established. Compared to the equal-interval interpolation distribution, when the curvature adjustment points for the finger elastic regulating plate are distributed by Chebyshev interpolation distribution, the calculation example shows that the maximum static contact stress of the workpiece is reduced by an average of 17.39% under the same grasping parameters. The Dynamic simulation analysis of the grasping workpiece process is performed using LS-DYNA, which shows that the maximum impact stress on the workpiece is reduced by up to 19% when the curvature adjustment points of the finger elastic regulating plate are distributed by Chebyshev interpolation distribution compared to the equal-interval interpolation distribution. The theoretical analysis results are verified by the actual prototype to capture the workpiece. The results show that when the curvature adjustment points for the finger elastic regulating plate are distributed by Chebyshev interpolation distribution, it is more suitable for grasping fragile, thin-walled cylindrical inner wall workpieces. The manipulator structure is low-cost to use and provides new ideas for designing specialized gripping manipulators.