Shoichiro Takehara

Tethers (strings and wires) are used in various mechanical systems because they are lightweight and have excellent storability. Examples of such systems include elevators and cranes. In recent years, the use of tethers in special environments, such as outer space, is expected, and various systems have been proposed. In this study, we propose a mobility system using a tether that moves a human by winding a tether attached to a wall. However, the method has a problem whereby the attitude of the human can lack stability during the winding of the tether. We developed the attitude control method of the Tether Space Mobility Device during tether winding while focusing on fluctuations in the rotational kinetic energy of systems. The effectiveness of the control method was shown using numerical simulation. In this paper, the proposed control system is installed in the experimental device for validating the numerical simulation model. Then, we verified the effectiveness of the proposed control method through experiments using an actual system. The experimental results confirm that the angular velocity of the Tether Space Mobility Device converges to 0 deg/s when control is applied. In addition, it was shown that the proposed control method is effective for automatically winding the tether.

Advances in space technology have opened up opportunities for human beings to work in outer space. It is expected that the upsizing of manned space facilities, such as the International Space Station, will further this trend. A unique means of transportation is necessary to ensure that human beings can move about effectively in microgravity environments. Here, we propose a tether-based mobility system that moves the user by winding a tether attached to a structure at the destination. To overcome the attitude instability of the user during tether winding, the Tether Space Mobility Device (TSMD) attitude control method for winding a tether is applied and examined through numerical analysis. The proposed analytical model for motion analysis consists of one flexible body and three rigid bodies. The contact force between the tether and the TSMD inlet is determined. Using the numerical analysis model, we investigated the effect of slit shape during tether extension and winding.

<p>This study aims to create a system that can be used to evaluate vehicle characteristics while simultaneously controlling human body behavior through numerical simulations. The proposed system consists of a vehicle model, a human body dynamics model, and a musculoskeletal model. In the present paper, a human body dynamics model using multibody dynamics is proposed. However, attempting to implement a whole-body model would necessitate dealing with multiple degrees of freedom and give rise to problematic phenomena. Furthermore, the influences of human motion are uncertain and difficult to parameterize. Accordingly, in the present research, the human model is limited to the head and trunk of a human body riding inside a vehicle. This human body dynamics model is composed of an internal model and an external model. The internal model incorporates a motion control model. The internal model, which is composed of an inverse model and a forward model, generates commands to control body motion, while the external model simulates the actual body motion. Then, in order to identify the parameters of the motion control model, the motion of maintaining posture is measured using a simple experimental device that can simulate horizontal acceleration applied to a subject. In order to demonstrate the effectiveness of the proposed human body dynamics model, a simple human dummy model (which simulates the experimental model used for experiments such as automobile collisions) that consists of only a spring and a damper was created. Comparing this dummy model with the human body dynamics model reveals that the human body dynamics model can simulate details of human motion that the simple dummy model cannot.</p>

<p>In this paper, we discuss the motion of a tethered system during winding a tether in microgravity. When the tether is being wound, it comes into strong contact with the feeding section of the system. Accordingly, both are expected to undergo complex motion as they interact with each other. We have therefore carried out both a numerical and an experimental study to clarify the motion of such a system using a mobility device using the tether named TSMD proposed by us as an example. We first developed a numerical model composed of three rigid bodies and a flexible body that serves as the tether. To take into account the large deformation and displacement of the tether, the flexible body was modeled using the absolute nodal coordinate formulation. It is important for the tethered system to consider the motion of winding the tether. In this model, the flexible body which is pulled into the rigid bodies contacting with its feeding section is formulated. This numerical model allows the interaction between the rigid and flexible bodies to be investigated as the tether is being wound. To verify the numerical results obtained using the proposed model, experiments were performed for a tethered system in a microgravity environment, where the tether was being wound. Good agreement was found between the numerical and experimental results. The tension in the tether was shown to influence the motion of the rigid bodies when the tether was under strain, and the rigid bodies were moved by an inertial force when the tether had a deflection. It was also found that the tension in the tether could be controlled by the winding speed, so allowing rotation of the rigid bodies to be suppressed.</p>

<p>The purpose of the present study is to propose an analytical model for tires and to examine the mechanism of polygonal wear based on numerical results obtained using this model. Polygonal wear is an abnormal phenomenon that occurs in time-delay systems. A number of studies on polygonal wear of tires have been conducted. However, investigation of the growth process of polygonal wear is not sufficient because the surface shape of the tire changes constantly with wear. Therefore, a numerical simulation model that can examine transient behavior is necessary. In the present paper, we propose a tire model composed of mass points. The wheel is simulated as a rigid body, and the tire tread as a number of masses positioned around the circumference of the wheel. The tire masses are connected to points around the circumference of the wheel by rotational and translational Voigt elements, and the tire masses are connected by rotational and translational Voigt elements. The contact between the tire and the road surface is assumed to be elastic. Numerical simulations are carried out under several conditions using the proposed model. The distributions of the stress and the slip ratio are obtained, and the wear shapes of tires are examined using the proposed model. We show that polygonal wear occurs under certain conditions. Finally, a tire model that expresses these basic characteristics is proposed and its usefulness is demonstrated.</p>

<p>Accurate modeling of a flexible body must take into account motion with large deformation, rotation and time-varying length. Numerical analysis, employing a variable-domain finite element model and the absolute nodal coordinate formulation, has been used to model such motion. Unfortunately, the calculation cost of this approach is very high due to the use of nonlinear finite elements with time-varying length. In order to the reduce calculation cost without sacrificing accuracy, we apply the multiple timescale method to the equation of motion. We define three timescales for the multiple timescale method, and refer to them as Cases 1, 2, and 3. Case 1 is based on longitudinal vibration, Case 2 is based on lateral vibration, and Case 3 is based on motion of the rigid pendulum. We compare these three sets of timescales and evaluate the analysis range for each of the sets. The numerical results show that Case 1 delivers the best accuracy when the velocity of the time-varying length is high, whereas Case 2 delivers the quickest calculation time.</p>

In this study, we construct an evaluation system for the muscular activity of the lower limbs when a human pedals an electric power-assisted bicycle. The evaluation system is composed of an electric power-assisted bicycle, a numerical simulator and a motion capture system. The electric power-assisted bicycle in this study has a pedal with an attached force sensor. The numerical simulator for pedaling motion is a musculoskeletal model of a human. The motion capture system measures the joint angles of the lower limb. We examine the influence of the electric power-assisted force on each muscle of the human trunk and legs. First, an experiment of pedaling motion is performed. Then, the musculoskeletal model is calculated by using the experimental data. We discuss the influence on each muscle by electric power-assist. It is found that the muscular activity is decreased by the electric power-assist bicycle, and the reduction of the muscular force required for pedaling motion was quantitatively shown for every muscle.

In this research, the dynamic characteristics of bicycles are investigated focusing on small wheels. Multibody dynamics is used for the formulation of the bicycle model. The effects of the parameters of tire diameter and head angle are examined by focusing on a small wheel bicycle. The straight-ahead stability and upstanding stability are evaluated at each parameter. The results show the tendency of stability at each parameter and the influential parameter to the small wheel bicycle is found. The driving experiment using the small wheel bicycles with variable head angle is evaluated by the subjects. It is confirmed that varying head angle increases the stability of the small wheel bicycle. The results are corresponding with the simulation results and it is shown that the simulation captures the tendency of the stability and expresses the characteristic of the small wheel bicycle. Furthermore, the simulation using the effective parameters for small wheel bicycle was shown at the end. It showed the possibility of increase of the stability of a small wheel bicycle.

This paper deals with the motion of a submerged tethered system subject to large deformations and displacements. A tethered system usually employs a cable or wire rope to tether an attached piece of equipment to the ground or to a vehicle, e.g., a remotely operated vehicle (ROV) in the sea. The motion of a tether was modeled using the Absolute Nodal Coordinate Formulation in which absolute slope of elements are defined as nodal coordinates. Herein, this formulation is adapted to account for hydrodynamic drag, buoyancy and added mass. By using the slope coordinates, the hydrodynamic drag acting on the curved shape of the deformed elements can be accurately calculated. Three kinds of experiment were conducted into the fundamental motion of the submerged tether when subject to large deformations and displacements. The numerical results from the proposed model agreed well with the experimental results.

Sensory evaluation of ride on a railway vehicle is performed based on international standards such as ISO2631. However, it is expected that this evaluation would be insufficient because of the development of technologies of a railway vehicle. The evaluation for view and sound from the viewpoint of ergonomic and psychological perspectives might be needed as well as traditional evaluations in the future. Authors focused on the relation between view and motion of the railway vehicle. The experiment in sensory evaluation of ride on a railway vehicle using a motion simulator was performed. In this paper, the way and results of the experiment and the environmental psychological analysis are described.

Research on multibody dynamics in engineering and science is developing at a high pace in Japan and in the world. These activities provide efficient and powerful solution tools for solving complicated dynamic problems with control via theoretical or high performance in-house and/or general purpose computer programs in academic and industrial fields. Thus, advancement of research is an important index for measuring competitiveness in education and industry in terms of &ldquo;dynamics and control&rdquo;. The aim of this paper is to present an overview of the various research activities of multibody dynamics in Japan.

This paper is concerned with a quantitative classification based on driver characteristics of steering maneuvers. The evaluation indexes that can be used for quantifying differences of driver groups such as experimental driver or beginner driver are proposed. The crank course test using actual car is performed in order to find the evaluation indexes to classify the driver's steering maneuvers. Then the crank course test using driving simulator is performed when gear ratio and a course width are changed. The characteristics of driver's steering maneuvers using these indexes are classified. It is demonstrated in this investigation that the method can be effectively used for classify an important characteristics of driver's steering maneuvers.

In this paper, we discuss the difference of driver's characteristics. Nowadays, driver assist systems are developed. It is very important to develop an effective driver assist system. We focus our attention on steering maneuver. We performed the experiment using the actual car. In the experiment, we measured not only a vehicle state but also the force acting on steering wheel and the motion of driver's arm. The six-degree-force transducer on steering wheel is newly developed. The motion capture system using supersonic wave is adapted. We found three kinds of characteristic maneuvers. First, it is the difference of steer angle. A beginner driver steers with high frequency. On the other hand, an expert driver steers without high frequency. Next, we investigated the location of grabs on steering wheel of each subjects. The beginner grabs particular place of steering wheel. They don't cross their arms during cornering. Finally, we found the difference of characteristic about pushing and pulling force on steering wheel.

This paper is concerned with a quantitative classification based on driver characteristics of steering maneuvers. The evaluation indexes that can be used for quantifying differences of driver groups such as experimental driver or beginner driver are proposed. The experiment using actual car is performed in order to classify the driver's steering maneuvers. The crank course test and handling course test are performed in order to classify the driver's steering maneuvers. Experimental results show the difference of driver characteristics of steering maneuvers on various courses.

This paper is concerned with a quantitative classification based on driver characteristics of steering maneuvers. The evaluation indexes that can be used for quantifying differences of driver groups such as experimental driver or beginner driver are proposed. The slalom test and the crank course test are performed in order to classify the driver's steering maneuvers using the driving simulator that has 6 degrees of freedom motion base and turntable. It is demonstrated in this investigation that the method can be effectively used for classify an important characteristics of driver's steering maneuvers. The proposed evaluation indexes are verified by experimental test with 24 subjects.

In the present paper, the motion of a tethered system with large deformation and large displacement is discussed. In general, a tether is a cable or a wire rope, and a tethered system consists of a tether and the equipment attached to the tether. A tethered subsatellite in space is an example of a tethered system. In the present study, a tethered system consisting of a very flexible body (the tether) and a rigid body at one end is considered as the analytical model. A flexible body in planer motion is described using the Absolute Nodal Coordinate Formulation. Using this formulation, the motion of a flexible body with large deformation, rotation and translation can be expressed with the accuracy of rigid body motion. The combination of the flexible body motion and the rigid body motion is performed, and their interaction is discussed.<br>Experiments are performed to investigate the fundamental motion of the tethered system and to evaluate the validity of the numerical formulation. Experiments were conducted using a steel tether and a rubber tether in gravity space. In addition, an experiment of the motion of the tethered system with a rigid body in microgravity space was conducted.

This study is focused on dynamic behavior of a small size tire. A small size tire is used for personal mobility, for example, a bicycle, a wheelchair and so on. We made experiments device for vertical behavior on bump for small size tire. We performed experiments to investigate the vertical behavior on bump for small size tire. We measured the force, the acceleration acting on tire and the vertical displacement of tire.