Bag-type grippers capable of grasping objects of various shapes have been developed so far. However, the conventional bag-type gripper mechanism has a problem that a large sliding resistance is generated due to contact with the surrounding environment during insertion into narrow space. This large sliding resistance causes collapse of the surrounding environment and breakage of the gripper itself. The authors propose the dual layer type torus gripper mechanism with extremely low sliding resistance in this paper. We developed the prototype model of the dual layer type torus gripper mechanism and verified its basic performance by some experiments.
This paper presents a basic study to develop a new damping device against flexural vibration of railway vehicle carbody utilizing elastic deformation of an elastic body as a dynamic vibration absorber (DVA). A donut-shaped elastic body (called ”elastic torus” in this study) is proposed considering practical application to rail vehicles. Vibration measurement tests using some existing elastic tori are carried out to examine the effect by their size and infill upon natural frequency. In addition, excitation tests for a 1:5 scale model of a Shinkansen vehicle carbody are conducted, and the DVA effect by applying such elastic torus against the first mode of flexural vibration of the carbody is demonstrated. Then, numerical studies using finite element (FE) analysis are carried out and it has been found that the shape and the size of an elastic torus having desired natural frequency can be determined by the numerical model. Finally, an elastic torus dedicated as a DVA for rail vehicles made of rubber filled with water is designed using the FE model and manufactured actually.
A new vibration reduction device against flexural vibration of railway vehicle carbody utilizing deformation of a donut-shaped elastic body called elastic torus is presented in this paper. The vibration properties of the elastic torus specially designed and manifactured for rail vehicles are firstly presented, and simple one degree of freedom (1DOF) model and detailed finite element (FE) model of the elastic torus are developed. In order to check the vibration reduction effect by the elastic torus, a series of excitation tests using a Shinkansen-type test vehicle are conducted by applying up to 20 elastic tori. Large vibration reduction effect has been observed against flexural vibrations of the carbody, and multi-modal vibration reduction effect has also been demonstrated. Then, numerical studies using simple beam model applied with 1DOF torus model and detailed FE carbody and torus models are carried out to check the vibration reduction mechanism. It has been confirmed that the reduction mechanism by the elastic torus is due to the effect that the elastic torus act as dynamic vibration absorber. And it has also found that different elastic deformation modes of the torus lead to the multi-modal reduction effect.
In future space transportation technology, reentry-systems are required, which is useful, safe and low-cost. MAAC (Membrane Aeroshell for Atmospheric-entry Capsule) R&D group have been developed the flexible structure atmosphere reentry system. The paper investigates the buckling strength of the flexible membrane reentry structure under static aerodynamic pressures in terms of non-linear finite element method. Numerical results are compared with experimental data obtained from a series of low speed wind tunnel tests using scale models of the proposed membrane aeroshell system. The comparison shows that the numerical results qualitatively agree with the experimental data, although the results clearly overestimate the buckling load of the membrane aeroshell. We conjecture that the discrepancies are originated from geometrical imperfections of the scale models not accounted for in the numerical analysis and introduce plausible patterns of the imperfections into our finite element models. Numerical analysis for the modified finite element models more precisely predicts the buckling loads, indicating that the geometrical imperfections significantly affect the structural strength of the membrane aeroshell.