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In recent years, the speed of express train has been raised by the improvement of technology about the vehicle, truck and electric. However, the speedup of railway vehicle caused high frequency vibration, and thus riding comfort is deteriorated by the resonance of the back seat. In this study, a passenger model with multi-body dynamics (MBD) was established a seat design guideline to reduce the vibration including high frequency. First, in order to construct the passenger model, the authors investigated the vibration characteristics of the passenger and the seat by a vibration test. The vibration test was performed under inputting linear sweep wave from 0.2 Hz to 40 Hz in the front-back or the vertical directions, and accelerations of the passenger's head, shoulders, chest, belly, thighs and the seat were measured. Next, a passenger model with 13 masses and 23 degrees of freedom was constructed by using MBD. Afterward, simulation studies were carried out under linear sweep wave, and the authors compared the simulation result with the experimental one. The simulation result shows the good agreement with the experimental one, and therefore the validity of the passenger model is verified.

Human foot is a complex musculoskeletal system. As it is inconvenient to directly measure tension forces of muscles attaching on limbs, a new quantitative method for dynamics analysis of muscle forces of ankle joint was presented based on a developed wearable motion, ground reaction force (GRF) sensor system and AnyBody Modeling System. In the AnyBody Modeling System, which professionally concerns on musculoskeletal kinematic modeling and analysis, quantitative results of muscle forces can be calculated through an inverse dynamics method. In this study, a musculoskeletal model composed of the shank and multiple-units foot was established in the AnyBody Modeling System, and an experiment was implemented with the wearable sensor system on eight volunteers during their normal gait. Tension forces of muscles of ankle joint were calculated through the inverse dynamics analysis, and the results matched the muscle activation level tendency of electromyography (EMG) method, which was implemented in the experiment as a contradistinction. The method for estimating muscle forces of ankle joint in the study appears to be a practical means to determine muscle forces in musculoskeletal analysis of human limb, and the system may be used as a convenient instrument for on-the-spot medical applications.

A numerical study of undulatory locomotion is presented. Unsteady hydrodynamics around an undulatory swimming body is solved using an integrated modeling method combining a 3D Computational Fluid Dynamics (CFD) method and a Computational Swimming Dynamics (CSD) method. A larva fish, zebrafish, Danio rerio, is modeled, which “swims” by sending a laterally compressed, sinusoidal wave down its body. Hydrodynamics of the three-dimensional larva fish model in terms of the burst, the continuous and the coast swimming modes were then analyzed and compared with conventional hydrodynamic theories, which provide a general understanding of the relationship between the dynamics of vortex flow and the jet-stream propulsion associated with the undulatory locomotion of vertebrates. As a result this analysis demonstrates a detailed picture of the structure of vortex wake behind a zebrafish larva and its correlation with force-generation.

The present state and future of “nonlinear dynamics” is explained in this review. First, chaotic vibrations of nonlinear beams are used as a material to demonstrate our present understanding of chaos, compared with the situation of the early stage of its research. Second, two topics, microcantilever dynamics of tapping-mode atomic force microscopy and design of Earth to the Moon transfer trajectories of spacecrafts, are chosen for describing the importance and usefulness of “nonlinear dynamics” in new technologies. Moreover, two applications of “nonlinear dynamics” to biped walking robots and nonlinear optimal control are briefly addressed.

Two problems were numerically analyzed for an unmanned aerial vehicle for aerial photography. Height control in backside of drag curve was studied, using optimal regulator and optimal control theories. It was shown that the optimal solution without limitations of terminal velocity was different from that with limitations. The optimal regulator from a given initial lateral deviation going back to the reference flight course was also presented. When a large roll angle is allowed, the wider camera view is lost but less deviation from the reference course is realized. The design trade-off was then discussed between camera view and deviation from the reference flight course.

Rhonrad is a gymnastic equipment that is interesting in terms of dynamics and control. We presented an analytical model and governing basic equations of the Rhonrad mechanism with a human body model. Then, a control method named as Synchronous control was proposed. In this control method, the human body moves synchronously with the rotation angle of the Rhonrad. The motion caused by Synchronous control was numerically analyzed. After that, a standalone miniature Rhonrad robot that consisted of three gyro sensors, an actuator, a micro-computer and batteries was manufactured. The validities of the Synchronous control were shown by experiments with the robot.

Force and torque induced by motions of a mobile manipulator effect dynamically to the objects being carried on it. If the induced inertia force and torque are bigger than the static friction force and torque, the carrying objects stary slipping motion on the mobile manipulator. As the result of it, the movement of carrying object may cause a collapse of all carrying objects, since a start of slipping makes the traveling acceleration of the mobile manipulator increase, furthermore it interferes with accurate traveling operations. A final purpose of this research is to propose a navigation controller of mobile manipulator that prevents the carrying objects from slipping. As a first step of this destination, we propose a model of n-link Power Wheeled Steering (PWS) mobile manipulator including the slipping motion of plural carrying objects. Using the proposed model, dynamical influences of the slipping are analyzed and the model is justified through several simulations.