Heel impact contributes to the stability of bipedal locomotion: the change of trajectory induced at heel strike has a stabilizing effect, and the phase-space volume contraction to which heel strike contributes is a necessary condition for stability. For a given passive walker, there is a slope limit to obtain stable limit cycles. However, this limit can be surpassed if extra dissipation is introduced. This stabilizing mechanism can be used or be present in bipedal locomotion. In this paper, it is proposed that heel strike can be accommodated to absorb more or less energy, and then that it is used as a regulation or control mechanism in bipedal locomotion. From a biomechanical point of view, dissipation through heel impact is the most efficient way to lose energy, any other way requires an active participation of muscles. This signifies the importance of the proposed regulation mechanism. In this work, some of the control possibilities of heel impact are briefly analyzed related to the energetics in order to claim its role and importance as a control mechanism in bipedal locomotion. This study can be valuable in several areas, for example, in control, prosthetics, shoe design, and generally in further understanding of bipedal locomotion.

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This paper proposes a method to determine model parameters of a numerical vibration model for railway vehicle carbodies by updating the model parameters using genetic algorithm (GA) together with measurement results. To analyze the three-dimensional elastic vibrations of recent light-weighted and structurally-simplified railway vehicle carbodies, a box-type analytical model was proposed. In this model, the carbodies are modeled as a box-type structure consisting of flexible plates and beams. These elements are connected each other by means of artificial springs. The model parameters such as the mass and stiffness properties of the beams and plates, and spring coefficients of the artificial springs must be specified to carry out a numerical calculation by the box-type model. The mass properties are relatively easy to determine, however, the choice of the stiffness parameters have not been well established, and the trial and error method is often adopted. Therefore, a reasonable and efficient methodology is strongly required. In this paper, an approach is proposed to determine the model parameters automatically using GA. In this method, the frequency response functions (FRFs) at the several points on the carbody are used to evaluate fitness between calculation and measurement results. By considering the FRFs at the points on the roof together with those for the floor, appropriate model data can be obtained both for FRFs and modal characteristics. Two different cases, a Shinkansen and commuter type vehicle, are employed as examples to evaluate the method. Good agreements between measurement and calculation results are observed for both cases and the validity of the proposed method is confirmed.

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This paper is on the development of Multibody Dynamics Analysis Education Tools. To achieve this, the authors investigated the basic features which are required for this purpose. The authors also investigated the best environment to satisfy these features, and found that Java Applet is very useful for this purpose. Java Applet is free to install on a common PC, and every student can make use of the developed tools only if he/she can make use of a Web Explorer through Internet. Based on this idea, the authors have been developing the education support tools: especially for the education on vibration. The students can set the parameters on the Webpage, calculate the motion, and display the results as the Animation of the motion and Graphs of the motion at a point of interest. The transactions are very simple and the students make use of these tools at almost any place where they can make use of Internet. However, the development of these tools is not so easy because coding programs by Java Applet is not so easy. It is very important and valuable to customize/ improve the program, but it is not so easy especially for students. Recently, the authors found that EXCEL+VBA is very useful and powerful not only to overcome this shortcomings but also to have good performance. So, they are shifting the development of the tools to this side. The students can make use of EXCEL on almost all the PC's as almost standard, and they also can use VBA (Visual Basic for Applications) as a powerful language with Excel. The authors developed an educational tool for Planar MBD by using EXCEL+VBA. As the MBD analysis method, the authors adopted the augmented method in this tools.

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The objective of this investigation is to develop a systematic procedure that can be effectively used for modeling joint constraints for the absolute nodal coordinate formulation. To this end, the non-generalized intermediate coordinates are introduced to derive a mapping between the generalized slope coordinates and the non-generalized rotational coordinates used for defining the orientation constraints with rigid bodies. With this mapping, a wide variety of joint constraints can be defined for a flexible body modeled using the absolute nodal coordinate formulation in terms of the non-generalized intermediate coordinates, and existing constraint libraries formulated for the rotational coordinates can be employed for the absolute nodal coordinate formulation without modifications. Furthermore, in order to define a rigid cross-section at the joint definition point, orthonormality condition are imposed on the generalized slope coordinates and, as a result, the generalized slope vectors at this point can be defined as an orthonormal triad. This leads to a simpler form of constraint equations defined between the generalized slopes and the non-generalized rotational coordinates. It is also demonstrated in the paper that this set of constraint equations can be used to eliminate the non-generalized coordinates as well as the dependent Lagrange multipliers from the equations of motion. Several numerical examples are presented in order to demonstrate the use of the systematic joint constraint formulation developed in this investigation.

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This study deals with the nonlinear dynamic behavior and the stability of a flexible cable structure with large sag subjected to the periodic excitation. The dynamic behavior of the flexible cable becomes unstable because of the restoring force of the gravity acting on the flexible cable. Both ends of the flexible cable are supported at the same height. One supporting end of the flexible cable is fixed rigidly, the other supporting end of the flexible cable is subjected to the periodic excitation in the vertical direction. We developed an analytical model of the flexible cable by using the finite segment method. This analytical model is divided into some rigid bodies which are connected by hinged joints. The each rigid body has the restoring force of gravity. From this analytical model, differential algebraic equations of the flexible cable are derived as a finite segment formulation. We calculated the nonlinear dynamic behavior and the parametric instability region by the numerical simulations. Moreover, the validity of the presented analytical model is verified by the experiments, and the nonlinear behavior and the parametric instability region of the flexible cable are discussed by the numerical simulations and the experiments.

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This paper proposes a derailment detection system in early signs of a railway vehicle. The proposed system detects abnormal vehicle signs before derailment using micro-electromechanical system acceleration sensors for automobiles. The new derailment detection algorithm was proposed in the former report. In this paper, a real-scale vehicle simulation is performed to apply the new derailment detection algorithm to an actual vehicle. At first, 1/10-scale vehicle simulation results are verified by using experimental results to indicate a reliability of the real-scale vehicle simulation. Finally, the real-scale vehicle results are performed in some derailment conditions.

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A coupling calculation method of dynamics and lubrication for rotor and floating bush bearing system has been developed to predict self-excited oscillations and unbalance oscillations using a flexible multibody dynamics technique with hydrodynamic lubrication theory. Based on experimental results of floating bush bearing, an accurate and numerically efficient lubrication model is proposed to calculate the hydrodynamic force, the bush rotating speed and the temperature of the oil film. In the multibody dynamics analysis, the rotor is modeled by a finite element method including bending elasticity and gyroscopic effect. The bearing bush is modeled by a rigid body. The coupling analysis between the rotor dynamics and the oil film force of the bearing is performed by an in-house flexible multibody dynamics solver. Then, the detailed mechanism of the rotor oscillation and the influence of some design parameters are investigated by numerical simulations and experiments.

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Many mobile robot navigation methods utilize laser scanners, ultrasonic sensors, vision cameras, and so on for detecting obstacles and path following. However, human utilizes only vision (e.g. eye) information for navigation. In this paper, we propose a mobile robot control method based on machine learning algorithms which use only the camera vision. To efficiently define the state of the robot from raw images, our algorithm has the image processing and feature selection steps to choose the feature subset for a neural network and uses the output of the neural network learned by the supervised learning. The output of the neural network is utilized the state of reinforcement learning algorithm to learn the obstacle avoiding and path following strategy from the camera vision image. The algorithm is verified by two experiments which are the line tracking and the obstacle avoidance.

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The design of mechanical systems involves the synthesis of mechanisms in order to meet a set of kinematic requirements. Several synthesis methods, graphical, analytical and computer-aided technique, have been proposed for selecting and scaling mechanical devices. The objective is to guide a rigid body through a specified position, or to force a point on a linkage to trace out the desired trajectory curve, or to perform a specific input/output relationship. This paper is based on the last task, function generation, although the proposed method can be applied to any of them. In function generation, rotation or sliding motion of input and output links must be correlated. Extensive research has been given to the synthesis of mechanisms for the purpose of function generation based on candidate mechanism layout. However, in the initial design stage, the designer has to synthesize a combination of linkage topology and type of joints which may be best suited for a particular task. This problem may be solved by means of experience, intuition of designers. So, the systematic determination of the optimal topology and dimension of mechanisms is very important in the mechanism design process. In this paper, unified mechanism synthesis which covered the problem of type and dimensional synthesis of planar mechanisms with respect to the functional requirement of output motion is proposed. To perform the unified synthesis for function generation, a planar linkage is modeled as a set of size-variable three rigid blocks connected by zero-length translational springs with variable stiffness. The values of spring stiffness and size of rigid blocks yielding a desired output motion related to input motion at the end-effecter are found by using an optimization method. If spring stiffness values are appropriately chosen, any linkage mechanism connected by revolute and translational joints can be represented. A linkage dimensions are determined by related block size during the synthesis process.

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This paper proposes SSM (Sensor Steering Mechanism) for a lateral guided vehicle with an articulated body which is allowing the vehicle to change moving directions. Authors demonstrate the geometry of SSM for a front wheel steer type, reverse phase four-wheel steer type and rear wheel steer type vehicle. SSM presents the stable lateral guiding performance for automated vehicle which follows a straight and curved path created by guideway. The other hand, SSM is not established for articulated vehicles such as wheel loaders and dump tracks used in the mine and construction site. SSM for an articulated vehicle enables a wheel loader to automated moving on every space. This paper leads SSM for an articulated vehicle and constructs an experimental robotic vehicle with proposed SSM. Simulated and experimental data show the advantages of proposed SSM.

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The governing equations for multibody systems are often formulated in the form of differential algebraic equations (DAEs) involving the Lagrange multipliers. As a method to solve the DAEs by eliminating the Lagrange multipliers, there is a method called the null space method. In a previous report, one of the authors presented procedure to formulate the governing equations of multibody systems by using the variational principle called the modified Hamilton's principle. The governing equation obtained by the presented procedure involves the Lagrange multipliers. In this report, use of the null space method in the modified Hamilton's principle is discussed. Then, a new method to obtain the null space matrix is presented. Finally, numerical examples are shown.

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Hemming is a process in which inner and outer panels of automobiles are joined by bending the edges of the outer panel over the inner one. The robot roll hemming process is highly suitable for increasing production volumes and varying product shapes in automobile flexible assembly line. Due to the deformation of the panels, a large fluctuation of the trajectory of a hemming robot's end-effector in the pre-hemming process affects the final hem quality. In order to analyze the fluctuation, the dynamics simulation considering the time-varying external forces is presented. The multi-body dynamics model is established by the Schiehlen's method. The external loads from robot roll pre-hemming in a specific path are computed by finite element analysis (FEA) method. The simulation results show that the end-effector of the hemming robot goes through an unexpected and fluctuant path. Therefore, to obtain good hem quality, dynamics simulation under 'real' external loads is necessary and provides the basis for active control of roll hemming robots.

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The dynamic modeling and analysis of rigid multibody systems that experience contact-impact events is presented and discussed in this study. The methodology is based on the nonsmooth dynamics approach, in which the interaction of the colliding bodies is modeled with multiple frictional unilateral constraints. The generalized contact kinematics is formulated in terms of gap functions and normal and tangential relative velocities. The dynamics of rigid multibody systems are stated as an equality of measures, which are formulated at the velocity-impulse level. The equations of motion are complemented with constitutive laws for the normal and tangential directions. In the present work, the unilateral constraints are described by a set-valued force law of the type of Signorini's condition, while the frictional contacts are characterized by a set-valued force law of the type of Coulomb's law for dry friction. Then, the resulting contact-impact problem is formulated and solved as a linear complementarity problem, which is embedded in the Moreau's time-stepping method. This method is considered here mainly due to its simplicity and robustness. The effectiveness of the methodologies presented in this study is demonstrated throughout the dynamic simulation of a planar multibody system.

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In optical systems with extremely high accuracy demands the dynamics of the individual components often restrict the technical feasibility. To be able to solve this problem one must know the influence of the motion within the optical system on the projected image. This requires a coupled dynamical-optical analysis with an observation of several different cases. Focusing on lens systems, an approach will be introduced which utilizes the motion of a lens to compensate the error produced by the motion of other lenses. The foundations needed for the development to solve these matters will be presented in the context of modelling the components of the lens systems with rigid bodies.

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In this paper we present a novel integration strategy to solve the evolution equations of deformable, nonlinear elements that possess viscoelastic mechanical response coupled with thermal dissipation. These types of elements may be found in a large number of every-day mechanical systems, such as vehicle suspensions, vibration absorbers for structures and machinery, etc. The proposed formulation is shown to be thermodynamically consistent, in the sense that energy is preserved and entropy never decreases in isolated systems. In addition, the conservation laws of linear and angular momentum are exactly preserved in the discrete setting. The development of the proposed algorithm is presented and numerical simulations will be provided to ilustrate the excellent performance of the method in terms of stability. This characteristic is directly related to the ability to preserve the structure of the continuum evolution equations, complying rigorously with the two laws of thermodynamics. The main conclusion is that the proposed methodology clearly outperforms classical methods widely in purely mechanical problems, and it is easy to incorporate to existing multibody formulations currently employed in many commercial and research codes.

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Authors are working on the development of the neurosurgical training system based on force feedback device. In the training system, it is necessary to generate not only visual view of the surgical scene similar to the surgical field but also tactile sensation due to intraoperative interaction between the brain tissue and the surgical instruments (brain spatula, suction, forceps, scissors, etc.). The development of the neurosurgical training system will greatly contribute to neurosurgery, since it enables neurosurgeons to improve surgical technique safely at any time. Furthermore, the surgeon can repeat the practice of the operation to a few cases by using the training system. In order to predict intraoperative brain tissue deformation due to retraction of cerebellum with spatula, our research group developed three-dimensional finite element brain model. However, long computation time was required. Computation time reduction is essential for the real-time simulation based on finite element analysis. The goal of this study is developing the novel finite element model which can achieve drastic computation time reduction of brain shift simulation for surgical training system by using static condensation. Static condensation is one of the methods for reducing the degree of freedom of the finite element model. Our research group demonstrated the usefulness of linear elastic model in gravity induced brain tissue deformation simulation for the reduction of computation time in the previous work. Then, the finite element analysis in the linear elastic medium is introduced in this study. Tetrahedral mesh is generated and the simulation results obtained by the proposed finite element model is compared with that obtained by the previous developed model. Illustrative brain tissue deformation simulation results will show the availability of the proposed model.

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This paper presents motion analysis of a planar rimless wheel. A spoke that comes in contact with the ground is free to detach from the ground. Detachments may lead to various types of motion such as bouncing. However, previous works usually assumed that the spoke does not detach from the ground until the new spoke impacts with the ground. Then bouncing motions never occur in the simulations. We conducted dynamical analysis of the rimless wheel when the impact is not perfectly inelastic in order to capture bouncing motions. The dynamical analysis clarified the motions of the rimless wheel. When the coefficient of restitution is not 0, the rimless wheel bounces after the impact. The stability analysis demonstrated that the motion of the rimless wheel is stable. Simulation results indicated that the coefficient of restitution affects the walking performance.

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One of the most fundamental models of biped locomotion is a planar rimless wheel which captures the stance leg motion and the heel strike. In numerical simulations, it is usually assumed that the impact between the leg and the ground is instantaneous and the impact results in no rebound and no slipping. This paper presents an experimental study on motions of a planar rimless wheel to validate the assumptions used to model rimless wheels. We investigate mainly the impact phenomenon with the ground. We built experimental setup to capture the motion of a planar rimless wheel. In our experimental setup, the rimless wheel moves on a slope. The motion is captured by motion capture cameras and a high speed camera. The locations of markers at a spoke are calculated by the images of the motion capture cameras. The motion analysis clarifies the effects of the impact phenomenon.

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The demand for the wheelchair has increased along with the aging society of recent years. However, there are a lot of reports. It is the user of the wheelchair fell acute pain, shake of head, alarm. Then, the author worked on the improvement of the dynamic characteristics of wheelchair at railway vehicle. The goal of this study is development of the configuration design method for the wheelchair. Under the condition of sudden stop of the railway vehicle, wheelchair user makes force to the joint for keeping the posture, the wheelchair might be redesign to decrease this excessive power. First of all, the dynamical model of the wheelchair and the human body in the train vehicle is derived. It is constructed by two-dimensional rigid body model with seven degree of freedom. Joint torque at each joint is calculated when the vehicle stop suddenly. In addition, frequency response functions upper and lower dynamic excitations was obtained. As a result, it is shown that the human body did not shake easily at 2.5(Hz) or more frequencies. Changing the wheelchair shape, the angle of the foot rest, the bearing surface, and the backrest of the wheelchair, the joint torque that affects to the head part of the human body model when stopping suddenly is reduced in 0.02(Nm). It is shown that it is effective in the dynamical load alleviation to the wheelchair user.

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In this paper, we deal with finite element modeling techniques for the dynamic behavior of sheet metal structures jointed by spot welds. A major requirement of spot weld finite element models is to accurately predict the dynamic characteristics of welded structures with a small number of degrees of freedom. In addition, spot weld models are easy to generate for non-congruent meshes of the jointed metal sheets. For this purpose, a model using multi-point constraint (MPC) is widely used in the automotive industry. For the model using MPC, we investigate the effect of mesh size in the area of the spot weld (patch area) on the modal properties such as natural frequency and mode shape. As an example structure, the structure that consists of two steel plates jointed by three spot welds is used. The results indicate that the proper shell element size in the patch area is dependent on the solid element size determined from the diameter of a weld nugget. The recommended range of the ratio of sizes of the shell to the solid elements is between 1.0 and 1.5.

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In this paper the design of a robust controller for position control in machining for a HEXAGLIDE type parallel robot using Quantitative Feedback Theory (QFT) is presented. The work is motivated by the insufficient vibration reduction achieved with a standard PID controller. Therefore active and passive disturbance rejection is the main objective. The linearization procedure of a detailed symbolic multibody model is presented and the disturbances -in QFT terminology- appearing as a result of the linearization shown. Uncertainties related to plant position, viscous friction coefficients and drive gains are considered. As a key step to a successful QFT design, special care is user to describe and quantify any known source of disturbances. Relative Gain Analysis is used to justify the adoption of a simplified SISO control design paradigm, and the coupling between axes quantified as a relatively small source of disturbances. Stability, control effort, disturbance rejection, and tracking performance are used to define the optimum minimum gain controller. The criteria is adjusted having in mind the capabilities of the plant and the importance of the different sources of disturbances. Virtual multibody simulations of the designed controller along with the nonlinear model of the plant are presented assessing the validity of the controller. The designed controller is intended to be deployed in the real manipulator and implemented using RTAI Linux Real Time implementation within the the EMC2 machine control software.

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Recently, an improvement of ride comfort is essential for vehicle designs to add commodity value. A technique to well estimate the ride comfort for vehicle passengers is strongly required from the above viewpoint. This paper investigates the modeling of a passenger in order to predict the ride comfort by CAE approach. A passenger model on a rigid seat is constructed by multi-body approach having nineteen degrees of freedom. Unknown parameters are rotational springs and dampers connecting body elements, which are estimated so as to explain the dynamic behavior of human body when exposed to vibration. Frequency range of interest is from 0 to 3 Hz, at which the roll and lateral vibration of human body are dominant. This model can represent the vibration characteristics of the main two natural modes that human body has below 3 Hz. And the improvement of the accuracy of the estimation in the entire model is tried by means of incorporating the rotary actuator which is considered the function of the muscle in the linear model and determining the torque of the rotary actuator by the feedback from the postural control system.

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With the increasing use of the International Space Station, humans have more opportunities to work in space. In space, a mobility device that operates efficiently is needed. But, some problems must be solved. First, the human body is suspended without the force of gravity. Second, the air cannot be polluted in the closed space of the Space Station. Thus, an air-polluting mobility device, such as a device with a gas jet using a thruster is objectionable. In this research, a mobility system called the "Tether Space Mobility Device" (TSMD) is proposed. In general, the tether is a cable or a wire rope. The tethers are expected to shift the orbit of another object without using a thruster and to move robots in space. TSMD has a mechanism that enables the tether to move an object. In this study, the TSMD model is composed of two rigid bodies and one flexible body that can express motion with large deformation and large displacement. Several modeling of TSMD is performed. An influence on motion and control of TSMD is discussed.

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To complete a contact model for dynamic simulation of the multibody systems besides algorithms to compute the normal forces of an elastic interaction one should implement also a model for the tangent contact forces. Here we build up an approximate model to compute resulting wrench of the dry friction tangent forces in frame of the Hertz contact problem. The wrench consists of the total friction force and the drilling friction torque. An approach under consideration develops in a natural way the contact model constructed earlier. The dry friction forces and torque are integrated over the contact elliptic spot. To implement the elastic bodies contact interaction computer model fast enough one builds up the approximate model in the direction as it was proposed by Contensou. To verify the model built the results obtained by several authors were used. The Tippe-Top dynamic model is used as an example under testing. It turned out the top revolution process is identical to one simulated using the set-valued functions approach. The ball bearing dynamic model is used to verify different approaches to the tangent forces computational implementation in details. The model objects corresponding to contacts between the balls and raceways were implemented on Modelica language for the Dymola visual compiler. Then the old friction model of the regularized Coulomb type and the new one, approximate Contensou, each embedded into the whole bearing dynamic model were thoroughly tested and compared. It turned out the simplified Contensou approach provides the computer model being even faster in compare with the case of the point contact.

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Using motion analysis technique, kinematics of steering motion as well as dynamic nature of steering motion are analyzed. During steering motion elbow pronation-supination, wrist flexion-extension, shoulder adduction-abduction, shoulder flexion-extension are major motion. For ±40° of steering wheel angle, elbow flexion-extension is the most sensitive to design parameters associated with steering wheel and seating configuration. Also through dynamic analysis, maximum joint torque is calculated and the results are compared with known values, which showed somewhat smaller values due to the multi joint evolvement of steering motion. Also there is some angle that each joint torque becomes maximum and minimum. The results can be applied to the steering system design as well as steering torque generation algorithm for active control of steering wheel.

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The motion and vibration of a moving body running on a complicated 3 dimensional (3D) trajectory considering an air resistance are investigated in this paper. A roller coaster is treated with here as a concrete example of moving body. The equations of motion of a roller coaster in which a trajectory and a vehicle are coupled are derived by using differential algebraic equation. In the previous paper, a roller coaster has been modeled as a one-wheel vehicle. In this paper, it is modeled as a two-wheel vehicle. The Baumgarte method is adopted for numerical stabilization. In this analysis, the influence of an air resistance and a rolling resistance, and the interaction between a vehicle and passengers as for a riding comfort of roller coaster are investigated. And also, the transmissibility of vibration through suspensions of roller coaster is studied in order to keep the safe security in the strength of rotating wheels and shafts. Besides, a part of simulations are compared with the experiments reported by previous paper.

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Robot assisted surgery is a new trend of development in surgery. Assimilating a robotic assistant in the surgical arena as an additional smart and precise tool bears numerous advantages. These advantages include broadening the capabilities of the surgeon in performing precise procedures and uplifting the burden of routine tasks. The intrinsic characteristics of parallel robots are discussed in this work and shown to suit the requirements of a robotic assistant better than the characteristics of serial robots.

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This paper presents a simplified approach for the forward dynamics analysis of the 6-P__-US parallel manipulator, as shown in figure.1, based on the force coupling and geometry constraint of the passive spherical joints. In the proposed method, the parallel manipulator is divided, at the passive joints, into the limbs parts and the platform part. And for both kinds of parts, the equivalent dynamic equations relating to the decomposing joints are obtained based on the transformation principles of dynamic equations between different spaces. Then, in the acceleration level, the dynamic models for both parts can be rewritten in the form of linear equations on the generalized constraint forces and the accelerations of the passive joints on the condition that the state (position and velocity) of the manipulator is specified. Thus, according to the force coupling and geometry constraints of the passive joints, the closed form solution for the generalized constraint forces can be derived readily from the linear equations system combined by the separated parts. Additionally, in the position/velocity level, the task space variables of the manipulator (the position and orientation of the platform) are chosen as the system generalized coordinates, which only results in the utilization of the inverse kinematics for the state transformation between the workspace and the passive joints space. Hence, by virtue of the constraint forces obtained from the above linear equations, the dynamic model of the parallel manipulator can be replaced by a single free rigid body (the platform) with specified external applied forces, provided by the environment through the end-effector and the limbs through the passive spherical joints, respectively. In the end, some numerical results are provided and compared to validate the correctness and effectiveness of the proposed approach.

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