Prolonged external force on the body surface is a cause of pressure injury, and polyurethane foam and gel-like materials are used to protect the soft tissue at protruding bone regions from the pressure injury. The aim of this study is an evaluation of the pressure redistribution and the shear resistance for two kinds of mattress, i.e., a standard mattress which is made of polyurethane mattress and a mattress with an upper layer of thin gel-like material and a thick layer of polyurethane foam. The measurement was conducted with a single condition by applying vertical and horizontal forces on the mattresses and measuring forces on the round surface of the protruding shaft and the surrounding disc of the developed device. The mattress with a gel-like layer showed a better pressure redistribution for the average pressure level of <3 kPa on the surrounding disc. It also showed a lower shear resistance. These results indicate an advantage of a usage of a gel-like material layer. Other loading conditions are necessary for better understanding of the mattresses.

The subloading surface model for the elastoplastic deformation is extended to incorporate the damage phenomenon. It is capable of describing the cyclic loading behavior under the bilateral damage.

The subloading-overstress model is formulated by incorporating the rigorous transformation rule of the similarity-center of the subloading and the normal-yield surfaces in this article. It is capable of describing not only the monotonic but/also cyclic loading behaviors in the general rate of deformation ranging from the quasi-static to the impact loading, which fulfills the continuity and the smoothness conditions exhibiting the smooth elastic-viscoplastic transition.

The exact crystal plasticity model based on the multiplicative hyperelastic-based plasticity is formulated in this article. It enables the exact description of the finite deformation with the concise formulation and the quite simple stress integration procedure.

The authors have previously proposed a control method that can significantly reduce the energy consumption of manipulators by using passive storage elements such as springs. This proposed method uses the natural vibration of the system, but the optimal spring constants change when the boundary conditions are changed or when the mass is changed by gripping the load. Therefore the spring stifnesses should be adjusted according to the operationg conditions. In order to solve this problem, we propose two methods, that is, a method using a variable stiffness mechanism and a method using a variable center of gravity mechanism. The effectiveness of the proposd methods are verified by numerical simulation.

In this study, we examine a modeling method and a trajectory planning method suitable for suppressing residual vibration in a flexible multibody system with large deformation. Here, the characteristics of the formulation and the residual vibration suppression effect are compared between the case where the floating frame of reference formulation is used and the case where the absolute nodal coordinate formulation is used to describe the flexible body. Until now, the absolute nodal coordinate formulation has hardly been used in the formulation of flexible robots, but it is shown that it is a very effective method when dealing with large deformation problems.

Since a multibody system including viscoelastic bodies is a stiff system, stable analysis is difficult with ordinary explicit numerical integration. In this research, we try to develop an approximate analysis method that can analyze the system including the viscoelastic body at high speed and stably by combining the approximate rigid link model, the recursive dynamics algorithm, the linear viscoelastic model and the implicit numerical integration method. In this paper, we explain the case where the Voigt model or Maxwell model is used as the linear viscoelastic model.

Transfer care is important to expand the range of activities of the care recipient and improve the quality of life. Therefore, in recent years, many floor-moving long-term care lifts have been developed, but many of them have an unnatural posture when used, which causes a problem that the mental and physical burden on the care recipient is large. The authors are developing a telescopic boom-type nursing care lift that reduces the burden on the care recipient by bringing the lift-up trajectory closer to the natural standing-up trajectory of the person. In this paper, we report mainly on the introduction of lumbar support wire and universal design as a further improvement of the proposed nursing care lift.

The problem of suppressing residual vibration of stacker cranes has been studied for a long time, but many of methods proposed so far have restrictions on use, such as the need to adjust the operating time to an integral multiple of the natural period of the system. In this study, a detailed dynamic model of the stacker crane is derived based on the flexible multibody dynamics theory. Then, a new control method with less restrictions that suppresses residual vibration by utilizing the coupling of the translational motion of the cart and the carriage, and the elastic vibration of the mast.

Since the mass of an vehicle occupant is not negligibly small compared to the mass of the vehicle body, it is required to establish a vehicle design method considering the dynamic interaction between the occupant and the vehicle body. For that purpose, a model that can predict the behavior of the occupant when the vehicle is running is required. Therefore, in this study, we try to construct a simple mechanical model that can simulate the physical behavior of the occupant based on the data obtained from the human vibration test. In this paper, we report the results of examining a control model that combines nonlinear PD control and deep learning.