Recently, to realize safer and more access-friendly environments, the accessibility evaluation for unhealthy people such as the elderly and disabled is becoming more and more important. To realize the reasonable and reliable accessibility evaluation, in the future, the human behavior simulation in 3-dimentional environments have a great potential. However, manually building such 3D environment models for the simulation is costly and time consuming, and it is sometimes inaccurate and do not necessarily capture the as-built environments. Additionally, the pedestrian model should also simulate detailed and various human motions as recent digital human simulations do. Therefore, our final goal is to realize the accessibility evaluation of “as-built” environments based on the detailed human behavior simulation. To achieve the goal, in this paper, we propose a method where as-built 3D environment models can be constructed in a fully automatic way from laser-scanned 3D point clouds measured from as-built environments. Additionally, we propose a basic walking simulation function of the digital human model (DHM) in the as-built environment models. Our proposed simulation enabled a DHM to automatically walk utilizing the functions of the global path findings, the walking path location control, the local collision avoidance and the walking motion generation. Moreover, we applied our modeling and simulation algorithms to the complex as-built environments : a two-storey indoor environment which includes caracoles and stairs, and an outdoor environment which includes slopes. The efficiency and effectiveness of the modeling and simulation were confirmed.
This paper proposes a design method for disc brake systems that aims to reduce brake squeal and improve cooling performance. The minimization of brake squeal, one of the most important issues that must be addressed when developing high-performance braking systems, can be achieved by maximizing the natural frequencies of the brake system structure. Maximizing the cooling performance of the brake system is an equally important design issue that affects braking forces and the performance of the braking system. In this paper, a topology optimization method is employed to maximize not only the natural frequencies but also the cooling performance in a simplified model of a brake disc. The optimization problem is formulated as a multi-objective problem, using a level set method in order to achieve clear structural boundaries in the obtained optimal configurations. Several numerical examples are provided to confirm the validity and utility of the presented design method.
DLC (Diamond-like carbon) films attract attentions because of their excellent tribological properties. Although DLC films are applied in various fields, there are few evaluation techniques for the surface strength of DLC films. We have been proposing our original evaluation technique, namely micro slurry-jet erosion (MSE) method. It's a new type of solid particle impact erosion test, which uses 1.2μm alumina particles as erodent. A parameter of surface strength of thin hard coating or film is determined as wear rate (μm/min) in the MSE method. In this study, the MSE test was carried out for DLC films with various hydrogen contents. As a result, it was found that the wear rate of the DLC films increased exponentially with an increase of hydrogen content from 0.001μm/min (hydrogen content : 0 at.%) to 1.28μm/min (hydrogen content : 30 at.%). The worn surface roughness measured by AFM increased with an increase of hydrogen content. Therefore, it was suggested that the increase of hydrogen content causes a decrease of surface strength of DLC films. We concluded that MSE method is useful for evaluation of the surface strength of DLC films.
Design specifications of semiconductor devices are constantly being miniaturized for increasing the integration density of the devices, which requires highly flat surfaces of silicon wafers as the starting materials of the devices. However, surface flatness significantly deteriorates near the wafer edge because of edge roll off during polishing as the final stage of the wafer manufacturing process. To address this problem, various polishing methods such as the use of polishing pads with small deformation property have been conducted and, however, cannot meet the recent demand for diminishing edge roll off in small stock removal of 10μm or less. In this study, the influence of polishing pad property such as deformation property on obtained edge surface flatness was experimentally investigated in various stock removal, and the influence on the stress distribution near the wafer edge was investigated using finite element methods. Based on the results, thin polishing pads with large deformation property were developed. Polishing experiments on silicon wafers showed that the developed polishing pads achieved high surface flatness near the edge in the overall progress of polishing including small stock removal as compared to commercial pads.
In machining processes of machine tools, guideways are subjected to the various dynamic force and moment. This paper describes the influence of the force amplitude on the dynamic characteristic of a linear rolling bearing. The carriage is excited in the feed and lateral direction respectively. The excitation force and the response acceleration of the carriage are detected respectively with a force transducer and an accelerometer. The frequency response function (FRF) is calculated based on the detected signals. To investigate the influence of the force amplitude, the FRF is measured with various force amplitude. As the result, the dynamic characteristic of a linear rolling bearing is varied with the force amplitude only when the carriage is excited in the feed direction. The frequencies and damping ratios of resonance peaks which are observed on the FRF decrease when the force amplitude increases. Then the relationship between the friction force and displacement is measured for clarifying the force amplitude dependence of the dynamic characteristic of linear rolling bearing. From the relationship between the friction force and displacement, the force amplitude dependence of the dynamic characteristic of linear rolling bearing will be due to the friction force in the pre-rolling region.
This paper proposes a friction compensation method in the frequency domain using a spectrum envelope. Friction compensation in mechanism is essential to improve the operability for haptics, the nonlinearity makes it difficult to realize high accuracy. This paper introduces the Cepstral analysis, and proposes a model-less compensation method using spectral envelopes. By using the Cepstral analysis, the feature of the system friction force can be treated as the gain characteristics of bode diagram. The proposed filter design using a spectral envelope is applied to the reaction force observer. The effectiveness of the proposal was confirmed by experiments using a linear motor.