Showing papers in "Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing in 2002"

Development of Power Assisting Suit for Assisting Nurse Labor

Abstract: In order to realize a power assisting suit for assisting a nurse caring a patient in her arm, a hardness sensor of muscle using load cell and a pneumatic rotary actuator utilizing pressure cuffs have been developed. The power assisting suit consists of shoulders, arms, waist and legs made of aluminum, and is fitted on the nurse body. The power assisting suit is originated with the concept of a master and slave system in one body. The arms, waist and legs have the pneumatic rotary actuators. The pneumatic rotary actuators are constructed with pressure cuffs sandwiched between thin plates. The action of the arms, waist and legs of the nurse are sensed with the muscle hardness sensor utilizing load cell with diaphragm mounted on a sensing tip. The dent of the sensing tip corresponds to the hardness of the muscle so that exerting muscle force produces electric signal. This paper gives the design and characteristics of the power assisting suit using the cuff type pneumatic rotary actuators and the muscle hardness sensor verifying its practicability.

Investigation of the Impedance Characteristic of Human Arm for Development of Robots to Cooperate with Humans

Abstract: In the near future many aspects of our lives will be encompassed by tasks performed in cooperation with robots. The application of robots in home automation, agricultural production and medical operations etc. will be indispensable. As a result robots need to be made human-friendly and to execute tasks in cooperation with humans. Control systems for such robots should be designed to work imitating human characteristics. In this study, we have tried to achieve these goals by means of controlling a simple one degree-of-freedom cooperative robot. Firstly, the impedance characteristic of the human arm in a cooperative task is investigated. Then, this characteristic is implemented to control a robot in order to perform cooperative task with humans. A human followed the motion of an object, which is moved through desired trajectories. The motion is actuated by the linear motor of the one degree-of-freedom robot system. Trajectories used in the experiments of this method were minimum jerk (the rate of change of acceleration) trajectory, which was found during human and human cooperative task and optimum for muscle movement. As the muscle is mechanically analogous to a spring-damper system, a simple second-order equation is used as models for the arm dynamics. In the model, we considered mass, stiffness and damping factor. Impedance parameter is calculated from the position and force data obtained from the experiments and based on the Estimation of Parametric Model. Investigated impedance characteristic of human arm is then implemented to control a robot, which performed cooperative task with human. It is observed that the proposed control methodology has given human like movements to the robot for cooperating with human.

Modelling of folding patterns in flat membranes and cylinders by Origami

Abstract: This paper describes folding methods of thin flat sheets as well as cylindrical shells by modelling folding patterns through Japanese traditional Origami technique. New folding patterns have been devised in thin flat squared or circular membrane by modifying so called Miura-Ori in Japan (one node with 4 folding lines). Some folding patterns in cylindrical shells have newly been developed including spiral configurations. Devised foldable cylindrical shells were made by using polymer sheets, and it has been assured that they can be folded quite well. The devised models will make it possible to construct foldable/deployable space structures as well as to manufacture foldable industrial products and living goods, e. g., bottles for soft drinks.

Geometric Analysis of Overconstrained Parallel Manipulators with Three and Four Degrees of Freedom

Abstract: This paper investigates the constraint characteristics of parallel manipulators with three and four degrees of freedom. An analytical method of using equivalent screw groups is developed in the study based on the linear independence of screw systems and reciprocal screw systems. A procedure for determining overconstraints in spatial parallel mechanisms with fewer six degrees of freedom is given. With this method, the constraint characteristics of four parallel mechanisms with three or four degrees of freedom, i. e. 3-RRC, 3-CPR, 3-URU/SPS and 4-UPU mechanisms, are revealed. The constraint characteristics of three types of parallelogram linkage unites are then discovered, which gives the corresponding equivalent representations in terms of serial mechanisms. The approach is further applied to the geometric analysis of parallel mechanisms with hybrid limbs including 3-R(4U)RPP and 3-R(4S)RRRP mechanisms.

Computer Simulation Study of Human Locomotion with a Three-Dimensional Entire-Body Neuro-Musculo-Skeletal Model

Abstract: A model having a three-dimensional entire-body structure and consisting of both the neuronal system and the musculo-skeletal system was proposed to precisely simulate human walking motion. The dynamics of the human body was represented by a 14-rigid-link system and 60 muscular models. The neuronal system was represented by three sub-systems: the rhythm generator system consisting of 32 neural oscillators, the sensory feedback system, and the peripheral system expressed by static optimization. Unknown neuronal parameters were adjusted by a numerical search method using the evaluative criterion for locomotion that was defined by a hybrid between the locomotive energy efficiency and the smoothness of the muscular tensions. The model could successfully generate continuous and three-dimensional walking patterns and stabilized walking against mechanical perturbation. The walking pattern was more stable than that of the model based on dynamic optimization, and more precise than that of the previous model based on a similar neuronal system.

Computer Simulation of Blood Flow, Left Ventricular Wall Motion and Their Interrelationship by Fluid-Structure Interaction Finite Element Method

Abstract: To simulate fluid-structure interaction involved in the contraction of a human left ventricle, a 3D finite element based simulation program incorporating the propagation of excitation and excitation-contraction coupling mechanisms was developed. An ALE finite element method with automatic mesh updating was formulated for large domain changes, and a strong coupling strategy was taken. Under the assumption that the inertias of both fluid and structure are negligible and fluid-structure interaction is restricted to the pressure on the interface, the fluid dynamics part was eliminated from the FSI program, and a static structural FEM code corresponding to the cardiac muscles was also developed. The simulations of the contraction of the left ventricle in normal excitation and arrhythmia demonstrated the capability of the proposed method. Also, the results obtained by the two methods are compared. These simulators can be powerful tools in the clinical practice of heart disease.

Biomechanics of Rowing

Abstract: A new control model for the study of biomechanical simulation of human movement was investigated using rowing as an example. The objectives were to explore biological and mechanical alternatives to optimal control methods. The simulation methods included simple control mechanisms based on proportional and derivative (PD) control, consideration of a simple neural model, introduction of an inverse dynamics system for feedback, and computational adjustment of control parameters by using an evaluative criterion and optimization method. By using simulation, appropriate rowing motions were synthesized. The generated rowing motion was periodic, continuous, and adaptable so that the pattern was stable against the mechanical force and independent of the initial condition. We believe that the simulation model is not only practical as a computational research tool from a biomechanical-engineering viewpoint but also significant from the point of view of fundamental biological theories of movement.

A Study on the Surface Shape of Fish Scales

Abstract: This paper is concerned with the functional design and hydrodynamic characteristics of fish scales. The rough surfaces of fish scales were measured with a three-dimensional, optical shape measuring system. The measurement was carried out on embiotocid fish Ditrema temminck, rockfish Sebastes inermis, and dogfish Mustelus manago Bleeker. Some scales of a dogfish Mustelus manago Bleeker were also observed microscopically making use of the scanning electron microscope as a faster fish. From the viewpoint of hydrodynamics, the microscopic structure and morphological characteristics of fish scales were discussed.

A Magnetic Tracking System based on Highly Sensitive Integrated Hall Sensors

Abstract: A tracking system with five degrees of freedom based on a 2D-array of 16 Hall sensors and a permanent magnet is presented in this paper. The sensitivity of the Hall sensors is increased by integrated micro- and external macro-flux-concentrators. Detection distance larger than 20cm (during one hour without calibration) is achieved using a magnet of 0.2cm3. This corresponds to a resolution of the sensors of 0.05µTrms. The position and orientation of the marker is displayed in real time at least 20 times per second. The sensing system is small enough to be hand-held and can be used in a normal environment. This presented tracking system has been successfully applied to follow a small swallowed magnet through the entire human digestive tube. This approach is extremely promising as a new non-invasive diagnostic technique in gastro-enterology.

Microcomputer-based Acceleration Sensor Device for Swimming Stroke Monitoring

Abstract: The purpose of this study was to develop a microcomputer-based acceleration logger device for the swimming stroke monitoring. The authors measured the swimmer's tri-axial wrist acceleration and applied this device for the fatigue evaluation of the swimmers. The experimental protocol led the swimmers exhausted after the crawl stroke interval training. Every single stroke was determined by the impact acceleration peak, which appeared on the x and z-axis acceleration. The change of the underwater stroke phases was identified by the characteristics of the acceleration peaks. In their exhaustion, the y-axis acceleration, which was longitudinal forearm acceleration decreased at the beginning of the upsweep phase. At that time, the swimmer could not extend his elbow joint. Since the developed acceleration data logger could provide us the information about the underwater stroke phases and it would be a helpful tool in the swimming training.

Nonlinear Analysis of Friction Induced Vibrations of a Two-degree-of-freedom Model for Disc Brake Squeal Noise

Abstract: This paper is based on the two-degree-of-freedom nonlinear model for brake squeal. The phase space analysis is performed to understand complicated dynamics of the nonlinear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, not only the existence of limit cycle but also the size of limit cycles is examined to demonstrate the nonlinear dynamics that leads the squeal state. The results not only describe the existence of limit cycle, but also show an additional important fact that it may make the system worse when too much damping is added in only the pad or the disc.

Extended Assemblability Evaluation Method (AEM) : Extended Quantitative Assembly Producibility Evaluation for Assembled Parts and Products

Abstract: The Assemblability Evaluation Method (AEM) is an effective tool developed by Hitachi, Ltd. to improve design quality for better assembly producibility. The AEM has been widely used by the Hitachi Group as well as by more than 20 other well-known companies around the world. Using this method, in the early design stage, product design quality is analyzed quantitatively and weaknesses in the design's assembly producibility are highlighted. In addition, the effects of design improvements are confirmed with respect to assembly cost. Through these activities, design improvement is realized. In order to improve the functionality and the accuracy of the method to allow a wide variety of use, the extended AEM has been developed. Based on a constructed product and process model, a new evaluation system has been developed and part-based cost estimation has been realized. In this paper, the concept, theory, evaluation procedure, and accuracy of the extended method are described.

Micro-Control Actions of Segmented Actuator Patches Laminated on Deep Paraboloidal Shells

Abstract: Deep paraboloidal shells of revolution are common components for horns, nozzles, rocket fairings, etc. This study is to investigate the micro-control actions and distributed control effectiveness of precision deep paraboloidal shells laminated with segmented actuator patches. Mathematical models and governing equations of the paraboloidal shells laminated with distributed actuator layers segmented into patches are presented first, followed by formulations of distributed control forces and micro-control actions including meridional/circumferential membrane and bending control components based on an assumed mode shape function and the Taylor series expansion. Distributed control forces, patch sizes, actuator locations, micro-control actions, and normalized control authorities of a deep paraboloidal shell are analyzed in a case study. Analysis indicates that 1) the control forces and membrane/bending components are mode and location dependent, 2) the meridional/circumferential membrane control actions dominate the overall control effect, 3) there are optimal actuator locations resulting in the maximal control effects at the minimal control cost for each natural mode.

Decentralized Job Shop Scheduling by Recursive Propagation Method

Abstract: A new information exchange method named recursive propagation is proposed in order to solve job shop scheduling problems in decentralized manufacturing systems. Each machine only has to notify the change of its plan to other machines which are directly influenced by the change. The effect of the change in the plan is directly fed back to the machine which notified the change. The change in the plan is notified to all the machines concerned by simple one-to-one communication among the machines, and the influence of the change caused by its action can be reported to the initiator through the same communication path. The proposed method is applied to a 20×10 job shop scheduling problem, and the feasibility of this approach is verified by simulations.

Morphological and Mechanical Properties of Bone Structural Units: A Two-Case Study

Abstract: Motivated by an improved understanding of skeletal fragility, the objective of this study was to investigate the relationships between morphological and mechanical properties of bone structural units (BSU). The average orientation of collagen fibers was classified using polarized light microscopy (PLM) and the mean degree of mineralization (MDMB) was quantified by microradiography for a collection of BSU from two donors. The mechanical properties of the same BSU were then measured by nanoindentation and scanning acoustic microscopy (SAM). Surprisingly, the indentation modulus and hardness quantified by nanoindentation were only weakly correlated to MDMB. The longitudinal wave modulus measured by SAM was better related to MDMB but did not correlate with the indentation modulus. There is increasing evidence that the collagenous phase and its bonding to the mineral phase play a significant role in the mechanical properties of bone tissue and deserve more attention in our understanding of bone fragility.

Tensile properties of contractile and synthetic vascular smooth muscle cells

Abstract: Tensile properties of vascular smooth muscle cells (VSMCs) of synthetic and contractile phenotypes were determined using a newly developed tensile test system. Synthetic and contractile VSMCs were isolated from the rabbit thoracic aorta with an explant and an enzymatic digestion method, respectively. Each cell floated in Hanks' balanced salt solution of 37°C was attached to the fine tips of a pair of micropipettes with a cell adhesive and, then, stretched at the rate of 6µm/sec by moving one of the micropipettes with a linear actuator. Load applied to the cell was measured with a cantilever-type load cell; its elongation was determined from the distance between the micropipette tips using a video dimension analyzer. The synthetic and contractile VSMCs were not broken even at the tensile force of 2.4µN and 3.4µN, respectively. Their stiffness was significantly higher in contractile phenotype (0.17N/m) than in synthetic one (0.09N/m). The different tensile properties between synthetic and contractile cells are attributable to the differences in cytoskeletal structures and contractile apparatus.

Three-Dimensional Vibration Analysis of Paraboloidal Shells

Abstract: A method of analysis is presented for determining the free vibration frequencies and mode shapes of open paraboloidal shells of revolution having arbitrary thickness. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. The ends of the shell, as well as the inner and outer curved surfaces, may be free or may be subjected to any degree of constraint. The strain energy of deformation, as well as the kinetic energy of motion, are formulated in terms of three displacement components which are tangent or normal to the shell middle surface. The displacements are taken as periodic in the circumferential coordinate and in time, and as polynomials of arbitrary degree in the other two coordinates, and the Ritz method is used to formulate the eigenvalue problem. Convergence studies are presented, and frequencies are given for moderately thick and thick, moderately deep and deep, paraboloidal shells of uniform and variable thickness.

Cross-Coupling Control for a Direct-Drive Robot

Abstract: This paper presents a cross-coupling (CC) controller for tracking contours to effectively reduce the contouring error of a direct-drive robot. Because contouring performance is a primary target over point-to-point tracking performance in a contour-tracking task, a cross-coupling control (CCC) algorithm design based on Lyapunov stability criteria and the recursive updating technique is proposed to enhance the contouring performance by coordinating the motion of multiple axes in spite of considerable model uncertainties and external disturbances. Furthermore, the proposed CCC design, which is a typical MIMO system with nonlinear time varying characteristic, has been verified as being locally stable. The control algorithm developed in tracking a circular and an elliptic contour is experimentally implemented on a two-axis direct-drive manipulator for various payload configurations. It is seen that the controller exhibits a certain degree of robustness, with the contouring performance being only slightly affected by changes in the payload. A comparison of the experimental results with those obtained by a tracking control law, which has no contouring consideration, and a conventional PID-type CCC tuned with the learning automata technique indicates that the proposed CCC can significantly enhance the contouring performance under different contouring commands and various payload configurations.

Adaptive Unbalanced Vibration Control of Magnetic Bearing Systems with Rotational Synchronizing and Asynchronizing Harmonic Disturbance

Abstract: In this study, we focus on the error in the estimated frequency of disturbance and present a new method of adaptive multiple frequency tracking and a new modification law after examining the relationship between the frequency error and output level in detail. We also develop a multiple frequency estimation algorithm which is insensitive to observation noise and theoretically prove the asymptotic stability for an adaptive nonlinear algorithm and adaptive frequency tracking method. The results of simulation show that when the frequency estimated by the difference equation method approaches the true value, the output error asymptotically converges to zero (or an equilibrium point). This corresponds to the asymptotic stability condition. The effectiveness of this method and the theoretical proof are verified by simulation. The experimental results show that the proposed algorithm is effective for achieving unbalanced vibration suppression.

Modeling of the Human Aortic Arch with Its Major Branches for Computational Fluid Dynamics Simulation of the Blood Flow

Abstract: We devised a method that combines the differential geometrical technique and overset grid formation to construct an aortic arch model for computational fluid dynamics (CFD) simulations. The simulations incorporate both non-planarity and the major branches at the top of the arch, using a set of magnetic resonance (MR) images, and we discuss their combined effects on blood flow. The results show that flow along the arch consists of a large right-handed rotational flow in the descending part of the arch, and a large left-handed rotational flow at the end of the arch. Although these characteristics of the global flow were similar to the results obtained using our previous arch model without branches, backward flow was found near the inner wall at the top of the arch due to the flow into the branches.

Development of Concave Conical Gear Used for Marine Transmissions

Abstract: Conical involute gears used for marine transmissions are mostly helical ones These gears are available in the form of not only intersecting axis gears but also nonintersecting-nonparallel axis gears The contact between tooth surfaces of a pair of gears is the point contact Tooth surface durability is generally low In order to overcome this weak point, one of the authors invented a new type of conical gear called “Concave conical gear” Concave conical gear has higher tooth durability than the conventional conical involute gear In this paper, a method to generate the helical Concave conical gear is newly developed First, the principle of the generating method is introduced, and the tooth surface is analyzed theoretically Second, test gears are ground Tooth surfaces of the test gears are measured and compared with theoretical ones, and good agreement is observed

A Piezoelectric Micropump Using Resonance Drive with High Power Density

Abstract: As fluid power sources mounted on practical and powerful micromachines such as in-pipe working micromachines using fluid power, micropumps having high power density are required. A piezoelectric micropump using resonance drive is proposed and developed. First, a large model of the proposed micropump is fabricated and the effectiveness of resonance drive is confirmed through basic experiments. Second, a micropump having the size of 9mm diameter and 10mm length for practical applications is fabricated. Next, frequency characteristics and load characteristics of the pressure-dependent flow rate are experimentally investigated with various structural parameters for the optimal design. Through those experiments, the optimal amounts of additional mass and valve thickness are experimentally obtained for stable and high performance of the micropump. The maximum flow rate of 80mm3/s, maximum pumping pressure of 0.32MPa and maximum power of 8.7mW are obtained at the driving frequency of 2.0kHz. Finally, the feasibility of developing the piezoelectric micropump using resonance drive is confirmed through comparisons of maximum power density among conventional micropumps.

VSS Controller Design for Gap Control of EDM

Abstract: As an electrode quickly moves towards the discharge field, and then starts to discharge, the proposed variable structure system (VSS) with large switched proportional (P) gains can suddenly hold the electrode at the appropriate position. The erosion process can start quickly and stably in order to decrease the idle time of the whole eroding process. The design procedure of the VSS is presented according to a practical gap control system for an EDM. This advantage can provide high performance on the nonlinear and time-varying gap condition during eroding process. The practical experimental results of an EDM with the VSS controller show a decrease of the machining time, compared to the time required by the conventional proportional (P) controlled EDM.

A Computational Fluid Mechanical Study on the Effects of Opening and Closing of the Mitral Orifice on a Transmitral Flow Velocity Profile and an Early Diastolic Intraventricular Flow

Abstract: A computational fluid dynamics study of intraventricular flow during early diastole is carried out to examine the effect of a change in the size of the mitral orifice due to opening and closing of the mitral valve on the flow evolution in the left ventricle during early diastole. It is found that a velocity profile of a transmitral flow with maximum velocity locating at the center of the mitral orifice is generated by gradual opening of the mitral orifice, and it remains even after the mitral orifice has fully opened. This transmitral flow causes the development of a vortex ring extending from the anterior to the posterior side of the left ventricle. The vortex ring keeps the main inflow to stream linearly toward the ventricular apex. Such a flow pattern produces an elongated shape of an aliasing area in a color M-mode Doppler echocardiogram obtained clinically. It is, therefore, considered that although opening and closing of the mitral orifice occur with a short period, they play an important role in characterizing intraventricular flow during early diastole.

Analysis of Stress and Strain Distribution in the Artery Wall Consisted of Layers with Different Elastic Modulus and Opening Angle

Abstract: Bovine thoracic aorta is stiffer in the inner wall than in the outer, and its opening angle is larger in the inner layer than in the outer. A model for mechanical analysis of such a heterogeneous artery wall was developed. The wall was assumed to be made of thin, incompressible, homogeneous, and isotropic layers having different elastic properties and opening angle. Stress and strain distributions in the wall were calculated using the opening angle and stress-strain relationship measured in thin sliced layers of bovine thoracic aortas. Stress distribution was uniform under a physiological condition if elastic properties and the opening angle were set uniform. Stress distribution was not uniform under any condition when the material heterogeneity was introduced. Such non-uniformity was reduced if heterogeneity in the opening angle was considered. The opening angle may be higher in the inner wall to compensate stress concentration caused by the material heterogeneity.

Lateral Stability and Steady State Curving Performance of Unconventional Rail Trucks

Abstract: Conventional railway vehicle systems exhibit hunting phenomenon which increases component wear and imposes operating speed limits. There is also a conflict between dynamic stability and the ability of the vehicle to steer around curves. Alternatively, independently rotating wheels (IRW) in a wheelset eliminate hunting but the wheelset guidance set capability is lost. A compromise solution is made possible by a modified design that exploits a lack of fore-and-aft symmetry in the suspension design. A comparative study on steady state curving performance and dynamic stability of some unconventional truck designs is carried out. The effects of suspension and conicity are considered to evaluate the trade-off between dynamic stability and curving performance.

Dynamic Analysis of the X-shaped Groove Aerostatic Bearings with Disk-Spring Compensator

Abstract: This paper describes the development of the modified resistance network method (RNM) for analyzing the dynamic behaviors of X-shaped grooves aerostatic bearing with a passive disk-spring compensator. The Newmark integration method and the modified RNM, which takes into account on the equilibrium of the mass flow rate and the squeeze film effect, are used to analyze the time-dependent dynamic behaviors. Results show that after impulse most of the vibrations are absorbed by the disk-spring compensator and the table can maintain a small vibration around the equilibrium position.

Optimization Approach for Reducing Sound Power from a Vibrating Plate by Its Curvature Design

Abstract: In many mechanical structures, structural design for noise reduction is becoming increasingly important. Noise reduction is often achieved through structural modifications. However, it is hard to predict the effectiveness of noise reduction by typical approaches. This paper presents an optimal design approach for reducing sound power from a vibrating plate by its curvature design. The method couples an optimization technique based on a genetic algorithm (GA) with the shape representation technique, vibration analysis and acoustic radiation analysis. It is shown that the curvature design of the plate obtained by using this method can achieve effective reductions in radiated sound power. Finally, the robustness of the optimized design candidates obtained is studied by using stochastic simulations in order to find those candidates which are least sensitive to changing design parameters.

Development of micro ultrasonic abrasive machining system: (1st report, studies in micro ultrasonic abrasive machining)

Abstract: This paper deals with the development of a micro ultrasonic abrasive machining system. The size of every component for opto-electrical devices or micro electro-mechanical systems (MEMS) has been reduced in recent years due to progress in opto-digital communications technology. The demands for micro-sized holes, slits and 3D structures of hard brittle materials such as ceramics and glass are considerable. In this study, a micro ultrasonic abrasive machining system was developed, which has an aerostatic ultrasonic vibration spindle, 3-axis NC sliding tables, dynamometer for machining pressure control and on-machine shaping system for small-diameter tools. The tools (0.03-1.0mm in diameter) and ultra-fine SiC slurry are used in the micro ultrasonic machining, and basic characteristics in micro-hole machining of glass are investigated. As the tool diameter becomes smaller, the machining speed and tool wear become the worse. However, rotating the tool doubled the machining speed, and decreased a protrusion left in the center of the machined hole due to cavitation.

Biomechanics of Rowing : I. A Model Analysis of Musculo-Skeletal Loads in Rowing for Fitness(Reviewed Papers Accepted for Publication in this Special Issue)(Special Issue on Bioengineering)

Abstract: Compared with the other exercise, such as walking and cycling, rowing was expected to have some fitness advantage, while there were some misgivings about the risk of injury. The objectives of this study were to quantify biomechanical characteristics of rowing for fitness and rehabilitation and to offer normative data for the prevention of injury and for determining effective exercise. An experiment was performed to collect the kinematic and kinetic data during rowing by experienced and non-experienced subjects. A three-dimensional whole-body musculo-skeletal model was used to calculate the biomechanical loads, such as the joint moments, the muscular tensions, the joint contact forces and the energy consumption. The results of this study indicate that rowing is an effective exercise for rehabilitation and fitness. However, the non-experienced rower should acquire considerable skill to obtain sufficient exercise. The rowing cadence should be decided according to the purpose of the exercise.