Aiming for a result to improve fatigue strength, “cutting and rubbing process” which is a kind of surface treatment was used for forming a round-bar smooth-specimen, showing drastically enhanced rotating-bending fatigue strength. On the other hand, actual machine components and structures invariably contain geometrical irregularities, such as fillets, keyways, screw threads, and holes. Fatigue cracks initiated from such stress raisers, indicating that the validity of the cutting and rubbing process on fatigue strength of specimen with a stress raiser should be examined. In this study, fatigue tests of smooth and notched specimens finished by the cutting and rubbing process were conducted under some loading types including rotating-bending, tension-compression and torsion loading. Results showed that fatigue strength of notched specimens was significantly enhanced compared to that of smooth specimens under rotating-bending and tension-compression loads. In other words, the cutting and rubbing processing was more effective in stress raisers than the smooth surface. The physical background on the effect of loading type on the fatigue strength of the cutting and rubbing processed specimen was discussed based on the fracture origin, microstructure in the surface layer, stress gradient caused by both loading type and notch.

The oil film thickness of the piston ring at the sliding surface affects oil consumption, friction loss and wear of the ring and liner in internal combustion engines. It is important to know the oil film thickness on the piston ring sliding surface in order to improve the engine efficiency. Accurate measurement of oil film thickness on the piston rings is difficult because the oil film thickness is extremely thin. A modified method is proposed for measuring thin oil film. The authors have measured the oil film thickness on the piston skirt and land to contribute. The optical measurement system and analytic method are improved. The presented method present the oil film thickness on the sliding surface of the top ring from the oil film visualization images. The verification of the measured oil film thickness carried out by comparing with the data obtained from the numerical calculation. For evaluating the effect of the oil characteristics, 0W-20 oil and #8 oil were tested with different engine speeds and different crank angle where different ring loads. It was confirmed that the top ring oil film thickness became thick due to the high engine speed. A large load on the top ring reduces the oil film thickness. The oil film became thick when the oil viscosity was high. The effect of oil viscosity on the oil film thickness of the top ring was clarified. The effect of the viscosity index improver was also discussed. It is shown from the experimental results that the present measurement system for the top ring oil film thickness has enough accuracy.

There are many pipes in factories, chemical plants and houses, whose insides are inaccessible by human. These pipes must be continuously inspected and repaired to prevent severe accidents. To realize robots which can inspect inside of such pipes, we have developed a simple and compact cylindrical crawler robot based on amoeba locomotion. In this study, we propose a steering mechanism that enables the robot to pass through T-shaped curves in pipes. Many of conventional steering mechanisms for crawler robots use single geared motor per single crawler belt to drive the crawler belts. On the contrary, the proposed mechanism can use a much larger geared motor than conventional steering mechanisms to drive all the crawler belts. Therefore, the crawler robot using the proposed steering mechanism can generate higher torque than one using conventional steering mechanism. This paper presents descriptions of the proposed steering mechanism design, comparison between proposed and conventional steering mechanisms with respect to the torque of the geared motor, and experiments using a 75A pipe with a T-shaped curve. In the experiments, the proposed steering mechanism was evaluated steering performance in a T-shaped pipe of 75A with three routes. The results demonstrated that the robot could pass through all the routes.

In our previous research, we had used a linear bicycle model as a tool to evaluate the basic functions of robust steering control laws. Since, we have researched a dynamic bicycle model considered the parameter varying on the linear bicycle model. Especially, just after steering transient, the center of rotation of the vehicle is not at the center of gravity but near the rear tires on this model. The influence of the parameter varying of the plant should be considered that the center of rotation is transferred from near the rear tires to the center of gravity on the vehicle turning. There is few researches regarding the reverse action phenomenon of the sideslip system occurred at initial steering period. Rarely, it has only been noted that the time constant of the numerator of the transfer function of side slip system becomes negative at high velocity, but the physical meaning of that negative time constant has not been explained. In our previous research, we have researched the mechanism of inverse action phenomenon using linear bicycle model. We have clarified the relationship between the unstable zero, which is the cause of inverse action phenomenon, and each element of bicycle model, and considered the practical effects of inverse action phenomenon through linear analysis. At the time, we have not considered the effect of the zero of the plant on the lateral and directional control system of the vehicle, therefore we have not demonstrated the practicality of this research. Based on this research, we have developed the dynamic nonlinear bicycle model (DBM) varying the instantaneous center of rotation just after steering transient from near the rear tires to the center of gravity. By comparing the characteristics of this DBM with those of a conventional linear bicycle model (CBM), we report the effects of the inverse action phenomenon just after the inverse action and the unstable zero as characteristics of the plant.

The emergency collision avoidance and trajectory planning are investigated in this paper. These are considered to be essential technologies for self-driving cars, which are important in regional revitalization. The collision avoidance by braking is called AEB (Autonomous Emergency Braking), whereas collision avoidance by steering is called AES (Autonomous Emergency Steering). The present research focuses on AES and aims to develop effective control theory based on EOC (Energy Optimal Control theory) with trajectory planning. A theoretical design method for EOC's virtual physical quantities and a method for accurately specifying the target trajectory were proposed. An emergency collision avoidance problem was designed to avoid collisions with vehicles crossing the center line and bicycles encroaching on the roadway on a two-lane road, and the effectiveness of proposed control theory and trajectory planning method are examined. It is found that the present theory can track the specified target trajectory very accurately. And the trajectory planning method proposed here is very simple and can define discontinuous trajectory which is critical for the design of complicated collision avoidance trajectory.

Overhead cranes are widely used to transport heavy loads, and their efficient operation requires fast and accurate positioning. However, residual vibration which prevents positioning accuracy generally tends to be induced by fast transportation. In previous paper, we proposed a control method which is based on the characteristic that the residual vibration is completely suppressed in a linear undamped system when excited by an external force which does not contain the natural frequency component of the system. To apply this characteristic to nonlinear damped systems, we defined the apparent external force which includes the influence of system nonlinearity and damping. It was confirmed that the residual vibration of a double pendulum type system model of crane can be suppressed by eliminating two natural frequency components from each the apparent external forces. In this paper, in addition, to improve the robustness for a double pendulum type system against the estimation error, new conditions are added to reduce the component around the natural frequencies from each of the two apparent external forces. The effectiveness of these conditions for robustness is verified through numerical simulations. Furthermore, changes in the robustness are examined when the position of the mass point near the support point of the double pendulum is changed. The results showed that the robustness can be improved in many cases except when the control time is short and the mass point is close to the support point.

Lure fishing is a well-known type of fishing that uses artificial lures instead of traditional live baits. Vibratory lure is a kind of lures performs greater vibration behavior than other kinds of lures. In common, more excellent vibration behavior of vibrating lure can attract carnivorous fish more efficiently. Up to now, lure design is generally based on the intuition of the designer, and there is little academic research on vibrating lure. In this study, we build the finite element model of a commercial vibration lure using a 3D scanner at first. Then, fluid–structure interaction (FSI) analysis is carried out to reproduce underwater motion of the vibration lure, where we can calculate the frequency of the flow induced vibration (FIV). Finally, in order to obtain the best FIV behavior of the vibration lure, based on the simulation results of FSI analysis, we perform structural design optimization of the vibration lure using the Box-Behnken design method, which belongs to the response surface methodology. In the structural design optimization, we set three design variables, which are the positions (x and z) of the weight placed in the lower part of the lure, and the eye position (i.e., the knot position between fishing line and lure) along the lure body. According to optimal results, the highest frequency of the FIV can reach 7.07 Hz. However, the present work is still in the early stage of the academic research on lure design, we aim to develop more optimization method for lure design that make lure fishing more interesting for both beginners and anglers.

In the super-aged society, the social role of nursing care industries is increasing. Many workers in the industries have the low back pain. Countermeasures to prevent it in the field of nursing care are urgent issues. One of the causes of the low back pain is known as an increase in lumbar intervertebral pressure. However, it is very difficult to measure the lumbar intervertebral pressure in a non-invasive manner. The goal of this research is to develop a human body finite element (FE) model to estimate physical burden such as the low back pain. In this paper, we investigated the validity of model prediction such as muscle activity and intervertebral disc pressures in a half-crouching position, which is a common posture causing the low back pain. An experiment using a human adult male volunteer was conducted to compare with the prediction results. The participant kept a half-crouching position while holding a box with his both hands. Activity of 16 superficial muscles was measured in three conditions of 0.6 kg, 9.2 kg, and 18.0 kg as the weight of the box. Under three conditions similar to the experiment, the muscle activity and intervertebral disc pressures when holding a box in a half-crouching posture were calculated using the human body FE model. The trend of change in the calculated muscle activation levels for each box weight generally showed good agreement with the experimental data. Predicted results of intervertebral disc pressures from the third lumbar to the fifth lumbar spine vertebra generally agreed with test data obtained from the literature. Muscle activity and distributions of intradiscal pressures, muscle contractile forces, and tensile strains of muscle and tendon changed according to the weight of the box. These results demonstrated that this model has the possibility of evaluating physical burden when holding a box.