Tomohiro Ito

Evaluation of the Effects of a Personal Mobility Vehicle on Multiple Pedestrians Using Personal Space

Personal mobility vehicles (PMVs) have increasingly attracted research interest as new individual transportation vehicles that are environmentally friendly, compact, and convenient to use. It is important to ensure the safety and comfort of pedestrians sharing space with PMVs. In this paper, we developed a simulation model considering the interaction between a PMV and pedestrians, and investigated the effects of a PMV in pedestrian flows using the concept of personal space (PS), which is the space in which invasion by others induces a psychological strain. To estimate the mutual effects of a PMV and nearby pedestrians, the invasion ratio and crossing time are introduced as indexes. Furthermore, to ensure pedestrians are comfortable in the presence of a PMV, we proposed an assistance system for a PMV. Simulation results revealed that the invasion of PS increases with increasing pedestrian density. Additionally, experimental results showed that the levels of discomfort and fear that pedestrians felt toward a PMV are also affected by pedestrian density. Finally, the effectiveness of the assistance system was confirmed, particularly for low pedestrian densities.

Individually specialized feedback interface for assistance robots in standing-up motion

We present a navigational interface for users of assistance robots. The interface suggests a motion that places low body load at the lower joints, carries a low risk of falls, and requires high voluntary activation of muscles. We describe an application that uses animations to provide feedback on a users sit-to-stand motion in order to demonstrate the potential benefits of such an interface.

Influence of the Size of a Personal Mobility Vehicle on the Affinity With a Pedestrian

Personal mobility vehicles (PMVs) as new individual transportation vehicles have been proposed around the world. It is important to ensure the safe operation of a PMV, especially when a PMV shares the space with a pedestrian. In this paper, in order to evaluate the influence of the size of a PMV on pedestrians, we measured the personal space of the pedestrians who walked against the PMV user. From the experimental results, it was shown that the width of the PMV and height of the step of the PMV significantly affected the personal space of pedestrians. Especially when the width and height becomes larger, the front personal space of the pedestrians expanded. In the simulation introducing the idea of personal space, the affinity between the PMV and pedestrians was quantitatively analyzed. It was found that the size of PMV affects to the affinity toward pedestrians.Copyright

Dynamic Instability of a Cylindrical Shell Structure Subjected to Horizontal and Vertical Excitations Simultaneously

Many structures such as support columns such as those for elevated expressways and towers tend to become larger and more flexible recently, thus the buckling or collapse of these structures is considered to easily occur than ever due to huge earthquakes. Actually, in the Hyogo-ken Nambu earthquake in Japan, buckling phenomena of tall support columns were observed every-where. Therefore, the evaluation technology on the dynamic stability is very important in order to ensure the seismic design reliability for these structures. The authors have ever studied the effects of the horizontal and vertical simultaneous excitations on the above-mentioned buckling phenomena of support columns experimentally. More-over, they also investigated the fundamental phenomena of the dynamic stability of the support columns subjected to the horizontal and vertical excitations simultaneously by numerical simulations using an analytical model where the support column is treated as a tall elastic cantilever beam. The purpose of this paper is on the dynamic instability, that is dynamic buckling, of a cylindrical shell structures such as those for elevated expressways, towers, containment vessels, LNG tanks and water tanks in various industrial plants so on subjected to horizontal and vertical excitations simultaneously. The coupled motion of equation with horizontal and vertical excitations simultaneously for these cylindrical shell structures is derived in this paper, and this modeling is shown to become a Mathieu type’s parametric excitation. The numerical simulation analysis is carried out for a cylindrical shell model with an attached mass on its tip. Comparing with the classical seismic analysis method, this proposed dynamic instability analysis method shows the larger deformation in horizontal direction due to the parametric excitation of the vertical seismic wave. As the results, the structures are apt to lose the structural stability more due to the coupling effects between the horizontal and vertical seismic simultaneous loadings.Copyright

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Excitation: 2nd Report — Investigation on the Nonlinear Ovaling Vibration at the Upper Wall

When a thin walled cylindrical liquid storage tank suffers a large seismic base excitation, buckling phenomena such as elephant foot bulge at the bottom portion and nonlinear ovaling vibration at the upper portion shows nonlinearity between the input and response level and suddenly occurs for the excessive input level, thus will be called as “nonlinear ovaling vibration” hereafter in this paper, may be caused. In the 1st report, the elephant foot bulge phenomena and the liquid pressure effects were investigated. In this 2nd report of the series of studies, the effect of nonlinear ovaling vibration phenomena were investigated based on the dynamic buckling tests using scaled models of thin walled cylindrical liquid storage tanks for nuclear power plants. The mechanism and the effect of vertical excitation and liquid sloshing were also studied and discussed.Copyright

Investigation on Buckling Behavior of Cylindrical Liquid Storage Tanks Under Seismic Excitation: 1st Report — Investigation on Elephant Foot Bulge

When a thin walled cylindrical liquid storage tank suffers a large seismic base excitation, buckling phenomena may be caused such as bending buckling at the bottom portion and shear buckling at the middle portion of the tank. However, the dynamic behaviors of the tanks is not fully clarified, especially those from the occurrence of buckling to some failures. In this study, bending buckling phenomena were focused which will be categorized as diamond buckling and elephant foot bulge. As ones of a series of studies, dynamic buckling tests were performed using large scale liquid storage tank models simulating thin walled cylindrical liquid storage tanks in nuclear power plants. The input seismic acceleration was increased until the elephant foot bulge occurred, and the vibrational behavior before and after buckling was investigated. In addition to the large scaled model tests, fundamental tests using small scaled tank models were also performed in order to clarify the effects of dynamic liquid pressure on the buckling threshold and deformation patterns.Copyright

A Preliminary Numerical Simulation Study of Developing Ankle Foot Orthosis to Support Sit-To-Stand Movement in Children with Cerebral Palsy

The purpose of this study is to identify an effective method of support for the standing-up motion of children with cerebral palsy (CP). Experiments revealed remarkable differences in the shank and upper-body motions of children with CP compared with normally developed (ND) children. Shank tilt angles of CP children were smaller and their upper-body tilt angles were larger than those of ND children. The large upper-body tilt compensates for the smaller shank tilt but will cause back pain and/or deformation of the hip joint as they grow. It is therefore imperative to find a method of support to help CP children realize more natural motions (similar to those of ND children) to prevent these problems. The standing-up motion of ND children was adopted as the goal. Experiments identified a similarity in the angular variation between ND children’s upper bodies and shanks; the standing-up motion of children with CP under that condition was then simulated using a two-dimensional four-link model of the human body. As a result of the numerical simulation, shank angles of CP children increased and their upper-body angles decreased from those measured during the experiments, which indicates that the proposed method of support is qualitatively effective at allowing CP children to realize a more natural standing-up motion.

Adaptive control method for an undulatory robot inspired from a Leech's nervous system

Many mobile robots using undulatory locomotion have been developed for search or rescue operations in narrow or dangerous places where people cannot enter, because undulatory locomotion can be employed for locomotion in various environments. However, an environmental change will require a mobile robot to change the pattern of undulatory locomotion. Recent studies showed that a leech changes its undulatory locomotion pattern depending on changes in the environment, and this is derived from sensory feedback from the muscle strain to the central nervous system. We propose an adaptive control method for a mobile robot that is inspired by the leechs adaptive locomotion. First, we make clear the role of this adaptive behavior of a leech by using the numerical leech model proposed in the preceding study. After that, we construct the simplified adaptive control method that simulates the leechs adaptive nervous system. Finally, we evaluate the effectiveness of our proposed control method with a numerical model. Our study showed that the proposed adaptive control method achieves regulation of body load due to the fluid despite a change in the fluid viscosity. Moreover, our control method reproduced the adaptive behavior of a living leech to changes in the fluid viscosity.

Maneuverability of an Inverted Pendulum Vehicle According to the Handle Operation Methods

This study investigated what handle operation and turning gain is comfortable for people using an inverted pendulum vehicle that is changeable the handle operation. Experimental conditions were three conditions. First is a slalom course with two cones placed at an interval of 1.8 m. Second is a slalom course with five cones placed at an interval of 1.4 m. Third is a slalom course with six cones placed at 1.8m, 1.4m, 1.8m, 1.4m, 1.8m, and 1.8m interval. The first condition considered the difference of handle operation between subjects who were used to ride and not used to ride. The second condition considered the difference of maneuverability due to gains. The third condition considered the difference of maneuverability between two handle operations in real running space in a condition of 10 gains. In a result of the first condition, a subject who was used to ride run effectively and running time is short compared with a subject who was used to ride. However, in handle yaw rotation, the difference of maneuverability was small. In a result of the second condition, running mileage about the same in two handle operation, but running time of handle yaw rotation is shorter than that of handle roll rotation. In a result of the third condition, like the second condition, running time of handle yaw rotation is shorter than that of handle roll rotation. In questionnaire evaluation, the best gain is the lower gain, 0.02. At last, An experiment was carried out by 14 subjects in the best gain, 0.02 that is best both handle operation. In the result of this experiment, 12 subjects answered that handle yaw rotation is better than handle roll rotation.

Sliding and Rocking Motion Mitigation of a Rigid Body Subjected to Seismic Excitation due to High-Viscous Liquid

After the accident at the Fukushima Daiichi Nuclear Power Plant in Japan, it has steadily become more important to ensure the structural integrity of cask systems containing spent fuels or radioactive debris during seismic events. These cask systems are free-standing cylindrical structures and are believed to show rocking and sliding motions at huge seismic excitations. In the worst case, these cask systems can possibly overturn or collide with each other. Therefore, it is very important to reduce the sliding and rocking motions of the cask system in order to avoid subsequent contamination due to radioactive substances.To date, the authors have been studying the response behaviors of these motions, and have developed some types of methods that are effective at mitigating sliding or rocking motions, and confirmed the effectiveness of these methods. A system utilizing coaxial circular cylinders and high-viscosity liquid filled into the annular spaces was developed for the suppression of sliding motion. This system was installed at the bottom end of the rigid body. Previous studies show that liquids with high-viscosity provide a very large added damping effect that causes sliding motion to be suppressed significantly. For the suppression of rocking motion, the authors developed a system that utilizes a gyro system, and confirmed it’s effectiveness both analytically and experimentally.However, the gyro system is slightly complex and requires electric power even during a seismic event. Thus, some passive suppression method is required. On the other hand, the above-mentioned coaxial circular cylindrical system filled with high-viscosity liquid is thought to have a high damping effect on rocking motion, along with suppression of sliding motion.This study investigated the effect of rocking motion suppression due to the above-mentioned coaxial circular cylindrical system that is utilized for the suppression of sliding motion. First, an analytical model that can account for the coupled rocking and sliding motion was established, and then the rocking behavior of a rigid structure coupled with its sliding motion was studied. Next, shaking table tests were conducted by using a fundamental test model. By comparing the analytically obtained rocking motion with that obtained by the test results, the validity of the analytical model was confirmed. Finally, the analytical model was modified for cask systems equipped with a rocking suppression system, and the rocking motion was analyzed to evaluate its effectiveness.The proposed rocking suppression system was found to be very effective in suppressing the rocking motion of the rigid body when subjected to base excitations.Copyright