No abstract

Two simplified methods for evaluating seismic margin due to elasto-plastic response were proposed. Generally, elasto-plastic response is evaluated by nonlinear time-history response analysis using three-dimensional FEM model (3D FEM model). It, however, takes an immense amount of time with commonly used computers. In order to evaluate it in a shorter time, this study developed seismic margin evaluation methods using Equivalent Single Degree Of Freedom (ESDOF) model and elasto-plastic response spectrum. Additionally, the accuracy of the two methods was verified by static loading tests and vibration tests. Simple cantilever test specimens with several natural frequencies were used in the vibration tests, and input waves with several frequency characteristics were applied to each vibration test. Response displacement, response acceleration of the test specimens and input acceleration were measured in each vibration test. Maximum displacement given by ESDOF model of the test specimens was compared with the corresponding measured values of each vibration test in order to verify the accuracy of ESDOF model. Difference between the maximum displacement given by the ESDOF model and the vibration tests was around 5%, and computation time of the ESDOF model was one-tenth of 3D FEM model of the test specimens. In addition, elasto-plastic response spectrum of input waves in the vibration tests were compared with measured yield accelerations of the specimens in order to verify the accuracy of elasto-plastic response spectrum. Difference between the calculated elasto-plastic response spectrum and the measured yield acceleration of the test specimens was around 10%, and computation time of elasto-plastic response spectrum was one-tenth of the 3D FEM model. As a result, it is concluded that ESDOF model and elasto-plastic response spectrum are powerful tool to evaluate seismic margin.

With increasing magnitude of design earthquake ground motions, it is necessary to develop methods of evaluating the seismic safety margin that are more exact than the current methods. However, a standard nonlinear analysis method requires step by step calculations of the numerical time integration scheme to obtain the seismic response. The authors present a new simplified analysis method of elasto-plastic seismic response. The proposed method is formulated by the energy balance between the input energy and the dissipated energy of an equivalent single degree of freedom model for actual equipment. Assuming the harmonic resonance of the single degree of freedom model, the maximum displacement response can be estimated conservatively. To verify the proposed method, static tests and vibration tests with cantilever-type specimens were performed. The vibration tests were conducted with sine, sweep down sine and random waves to verify the conservativeness of the proposed method. Comparisons of the maximum displacement between the tests and the proposed method show the conservative estimation of the displacement by the proposed method.

In ultra-compact electric vehicles, the satisfactory installation of an assist mechanism for steering operation is difficult. To address this problem, in this paper, we propose an active steering wheel system in which the steering wheel and tires are electrically connected, without a mechanical connection. Furthermore, in ultra-compact mobility vehicles where the driving position is restricted, steering burden is likely to occur depending on the physique of the driver. However, whether the effects of the steering reaction torque and the amount of steering increase the burden on the driver in such vehicles has not yet been clarified. Therefore, in this study, we developed an upper limb burden model using inverse kinematics and muscle activity to investigate the burden of steering on the driver by considering the driver physique.

This paper describes a new type planetary gear drive with the high reduction ratio. The planetary gear drive is mechanically similar to a 2S-C type planetary gear, which has two sun gears and one carrier. The planetary gear drive has two pairs of an arc tooth profile gear and a pin roller, which mesh each other. The planetary gear drive has little backlash, a high efficiency, a long fatigue limit, etc., because the tooth contact holds on concave and convex surfaces. In this study, we measured the vibration acceleration, the transmission error, the gear noise, and the efficiency on the new type planetary gear drive by the running test. We discuss and report the driving performance of the planetary gear drive.