Showing papers in "Transactions of the Japan Society of Mechanical Engineers. C in 1997"

Relationship between structure of finger tissue and location of tactile receptors

Abstract: There are several tactile receptors at specific locations in the tissue of human fingers. In this study we calculate in detail the deformation of finger tissue when a finger comes into contact with a rigid plate using a FE (finite element) model in order to clarify the reason for the precise location of the receptors. The FE model is constructed using the measured geometry and properties. As a result, we found that the strain energy is concentrated at tactile receptor locations. When a frictional force is applied, the stress/strain is concentrated near the edge of the contact area. By calculating using models with/without epidermal ridges/papillae, we found that the shape of the epidermal ridges/papillae influences the stress/strain distribution near the tactile receptors.

自動車運転時の眠気の予測手法についての研究 : 第1報, 眠気表情の評定法と眠気変動の予測に有効な指標について

Abstract: An automobile simulator experiment was carried out in order to develop a method of prediction of sleepiness based on mainly physiological parameters. Twelve subjects participated in the study. First, criteria variables of sleepiness were investigated since such variables have not been clear in many previous studies. Rated sleepiness based on facial expression was examined as a criteria variable in this research. Rated sleepiness by two examiners gave high correspondence (0.755), and mean correlation coefficient between this rated sleepiness and the subjects' self-rating sleepiness was also high (0.794). These results show that this rated sleepiness is considered to be reliable and valid as a criteria variable. Second, both physiological parameters and the driving performances were adopted as explanatory variables. Cross-correlation analysis between the rated sleepiness and these parameters showed that α/β at posterior-midline (Pz), blink duration, the rate of long blink and heart rate were relevant as general indexes of slepiness. Methods of prediction of sleepiness based on these results are mentioned in our second report.

Design of a Dynamic Vibration Absorber for Minimization of Maximum Amplitude Magnification Factor. Derivation of Algebraic Exact Solution.

Abstract: Fixed points design methods for dynamic vibration absorbers are very well-known in the field of vibration control and commonly applied for practical absorber design. However, they must be understood to be approximation methods from the point of view of their design criterion that the resonance amplitude magnification factor is minimized. In this study, the exact algebraic expressions of optimum tuning and damping parameters for the minimization of the largest resonance amplitude magnification factor of linear dynamic vibration absorbers have been derived for undamped primary systems. The existence of two equal height resonance points is reduced to a multiple root condition of an algebraic equation. The determinant is handled as an equation with respect to the resonance amplitude. It has became very clear that the fixed points theory design by Brock is highly accurate. In particular, it exhibits very small error in the practical mass ratio range, e.g., below unity. Algebraic solutions also exist for the resonance frequencies and the anti-resonance frequency. A numerical extension of the method is introduced in order to investigate the optimization problem for damped primary systems.

Identification of alignment errors in five-axis machining centers using telescoping ball bar

Abstract: This paper deals with the identification of alignment errors in five-axis machining centers. There are thirteen alignment errors in each five-axis machining center. Three alignment errors in the three translational slideways are identified by circular tests using a Telescoping Ball Bar. In this paper, assuming the use of a Telescoping Ball Bar, identification methods for the other ten alignment errors in five-axis machining centers are proposed. The theoretical background for identification is given by a form-shaping theory. The validity of the proposed identification method of alignment errors is confirmed by experiment.

Functional Coordination Control of Pairs of Antagonistic Muscles.

Abstract: The antagonistic pairs of mono- and bi-articular muscles of the upper extremity demonstrated perfectly coordinated muscular functions during arm push and pull movements with maximal effort in all round directions (360°) in the horizontal plane, which has been already observed in the sagittal plane through our experiments. Analysis of a proposed neural network suggested that the tightly coordinated functional patterns could be induced using only force direction information via the spinal level, and also that the tight coordination can be applied in mechanical engineering and robotics.

Self-Sensing Magnetic Bearing Using the Differential Transformer Principle.

Abstract: A new method of self-sensing magnetic bearings is introduced. Magnetic bearings are intended to function both as a forcing actuator and a gap sensor. The magnet has two coils. One is a bias coil which provides constant bias flux to the air gaps. The other is a control coil which increases one gap flux and degreases the other gap flux. The magnetic force is linearized to the control coil current using this technique. The coils are also used as a differential transformer-type displacement sensor. The current of the bias coil is adjusted by changing the dusy ratio of the pulse-width modulated signal. The induced carrier frequency component in the control coil is detected and put into the demodulating circuit to obtain the rotor displacement. Two sets of driving and demodulating circuits are used to detect the horizontal and vertical displacements of the rotor. The position of the rotor is controlled using the proposed method. The rotor can run up to 12000 rpm using the self-sensing magnetic bearings.

Train Damaged by the Quake in kobe.

Abstract: Many trains were derailed and damaged by the earthquake in Kobe on January 17, 1995. At the same time, many railway girder bridges and viaducts were seriously damaged by the quake. It was postulated that serious accidents could occur as a result of trains running at high speeds into these girder bridges or viaducts. Fortunately, no fatal accidents occurred. On investigating such accidents, the authors found that they rarely occur, because a train derailed by the violent shock of a quake is so radically decelerated by the huge running resistance caused by the derailment that it stops just after the quake. On the other hand, it takes some time until the bridges or viaducts collapse after the quake.

Motion Control of an Overhead Travelling Crane with Hoisting Motion and Curve Trajectory.

Abstract: This paper presents modeling and control of an overhead travelling crane at three-dimensional complex transfer trajectory with and without hoisting motion of the straight and curved trajectories. First, the proposed model of an overhead travelling crane with respect to the sway of a suspended object is given as two models with mutual coupling projected on the travelling-vertical plane and the transverse-vertical plane. Second, in order to achieve practical control of the tracking of a reference trajectory, the suppression of sway of an object suspended by a wire and the time variation of a crane system during hoisting motion, two optimal regulator control systems with gain schedule are independently designed along the X and Y directions. Finally, the usefulness of the present approach is demonstrated through control simulations and experiments.

Stokesian Dynamics Simulations of Ferromagnetic Colloidal Dispersions in a Simple Shear Flow.

Abstract: We have investigated the behavior of clusters of ferromagnetic particles in a colloidal dispersion subjected to a simple shear flow. To do so, the Stokesian dynamics method has been used under the assumption that the effect of Brownian motions are negligible. For the case of no shear flow, the aggregate structures obtained by the Stokesian dynamics simulations agree well with Monte Carlo results qualitatively. We can, therefore, conclude that the Stokesian dynamics simulations can capture thick chainlike clusters without introducing a specific clustering algorithm, which is indispensable for Monte Carlo simulations. The behavior of the thick chainlike clusters in a simple shear flow is summarized as follows. The thick chainlike clusters decline in the shear flow direction as time advances. Since longer clusters experience larger shear forces, long clusters are difficult to survive in such a situation. The thick chainlike clusters dissociate into some short clusters. Such clusters are relatively stable in a shear flow, so that they do not dissociate significantly any more. The viscosities have a strong relationship with the internal structures of the aggregates. The instantaneous viscosities, therefore, fluctuate significantly for the case of the thick chainlike clusters.

Evaluation of Pain Tolerance Based on a Biomechanical Method for Human-Robot Coexistence.

Abstract: In this paper, we discuss human pain tolerance for the design standard of a human-robot coexistence system. Among human sensations, somatic pain is like an emergency call. It is regarded as a stable sensation having neither individual variations nor adaptations. Therefore, we adopt somatic pain which can tolerate repeated mechanical stimuli. We carry out experiments to measure the threshold of human pain tolerance using a biomechanical method and statistical analysis. Moreover, we clarify human pain tolerance when a static or dynamic stimulus is applied. Human pain tolerance is characterized uniformly in terms of the pain intensity curve (PIC) which is fitted to the minimum values of both the static and the dynamic pain tolerance. Moreover, we investigated the relationship between the deformation and velocity of the human sections of our interest, when the human subjects felt somatic pain. Human pain tolerance will be a trigger to build up an advanced safety design standard.

Data Input Device for Physically Handicapped People Operated by Eye Movements.

Abstract: Data input devices for physically handicapped people have already been developed. One simple device detects the blowing action of the operator as input signals to select desired menu items. Another advanced device detects eyeball movements as input signals. One problem associated with these advanced data input devices is that the operator is often obliged to wear a sensor or device. In this work a data input device operated using eye movements is presented. An important feature of our system is that the operator is not obliged to wear a sensing device.

Nonaxisymmetric Aspheric Ceramic Mirror Machining Using Arc Envelope Grinding Method.

Abstract: We report a grinding technique called the "arc envelope grinding method (AEGM)" and its grinding tests. In conventional form-generation grinding, loading and dulling of a diamond wheel can easily occur, which decrease both the machining accuracy and the wheel life, since the same part of the wheel is always used. In AEGM, a diamond wheel with a round profile is used and the workpiece profile is an envelope of a family of arcs. Since the grinding point is changed along the wheel profile with every grinding pass, the entire wheel width can be used and the wheel life is prolonged. In this study, arc truing accuracy, wheel design, surface roughness and form accuracy of the ground workpiece are investigated. Using the AEGM, nonaxisymmetric aspheric mirrors of silicon carbide were successfully ground. The form error after the first grinding (without any compensation) was less than ±0.8μm, and the roughness was Rmax=0.2μm.

Influence of Atmospheric Conditions upon Adhesion between Rails and Running Wheels

Abstract: The authors investigated the adhesion coefficient between rails and wheels using a model "Slip Adhesion Test Truck" and model rails, and quantitatively evaluated factors such as rail temperature and humidity which may affect adhesion. The adhesion coefficient was measured under various conditions. As a result, they find that adhesion is strongly influenced by the rail temperature and the humidity around the running surface of rails.

Measurement of Helical Gear Using Coordinate Measuring Machine.

Abstract: A method for inspecting a helical gear using a coordinate measuring machine (CMM) is proposed. In the method, the coordinates of a large number of points on the tooth surface of the gear are measured at random using a CMM. The method is based on the idea that the pitch error, profile error, pressure angle error, and spiral angle error can be calculated from the measured coordinates because the information on various errors of the gear is included in the measured coordinates. For calculation of each error, the tooth surface is described as a function of each error item and then the values for the items are estimated from all of the measured coordinates by the method of least squares. The difference between the estimated value for the item and the corresponding design value is the error of the item. From the results of experiments, it is clarified that each error of a helical gear can be estimated using a widespread CMM instead of a specially designed measuring machine for gears.

Thermal Deformation of an Ultraprecision Machine Tool due to Environmental Temperature Change. Analysis of Thermal Characteristics by Transfer Function and Estimation of Deformation by Convolution Integral.

Abstract: The present paper deals with the thermal behavior of the main spindle system of an ultraprecision machine tool as affected by a change in the temperature of the ambient air. First, it is found that the thermal deformation increases with an increase in the rotational speed of the spindle, which is considered to be caused by an increase in the heat transfer coefficient. The transfer functions between the ambient temperature variation and the thermal deformation of the machine are obtained experimentally for various rotational speeds, and the thermal behavior of the machine is analyzed. Second, a simple method of estimating the thermal deformation for future control of machining accuracy by utilizing the measured transfer functions and the convolution integral is proposed.

Antilock Braking System Using Sliding Mode Control.

Abstract: Current control algorithms for antilock braking system (ABS) are mostly table-driven and should be frequently modified through various experiments, because the braking dynamics are highly nonlinear with system uncertaintieS. In this paper, a new control algorithm is proposed for ABS using the theory of sliding mode control based on a linearized system model, which represents nonlinearities as external disturbances. The proposed sliding mode controller guarantees a highly robust performance against large variations in the system parameters and disturbances. Furthermore, a road surface estimation scheme using a disturbance observer is proposed in order to determine the optimal reference input. Simulation results reveal the advantages of the proposed method in comparison with conventional linear controllers.

A Robot System with Safe Contact Detection and Stopping Capabilities Based on Human Pain Tolerance.

Abstract: In this paper, we propose a human-safety-oriented design method to realize a safe robot system for human-robot coexistence. We conduct some simulations to identify problems in human-robot collision situations, and point out, based on the human pain tolerance limit which we have clarified, that a robot working next to a human should be covered with a soft material and be equipped with prompt stopping capability. First, we construct a fail-safe robot system with contact sensing and subsequent emergency stop control capabilities using a simple disturbance observer which plays an important role in checking the normal operation of a two-link DD-motor-driven manipulator. Second, we design a soft covering made of a viscoetastic material which achieves both effective impact force attenuation and high contact sensitivity, keeping impact force within the human pain tolerance limit. Finally, we demonstrate actual human-robot collision experiments to show that the contact force generated at collisions was suppressed below the human pain tolerance limit.

Improved Design Scheme of MRAC for Pneumatic Servo System with Additive External Forces.

Abstract: An improved design scheme of a model reference adaptive control (MRAC) for a pneumatic servo system with additive external forces is presented. In this design scheme, the difference process for the identification signals is adopted in the identification mechanism for elimination of the influence of the constant disturbance caused by the additive external forces. Furthermore, the controller of this design scheme is constructed with a compensator for overcoming the influence of the disturbance. As a result, the satisfactory control performance can be achieved.

Impact Analyses of Whiplash Neck Behaviors in Rear-End Collisions.

Abstract: Neck injury by rear-end collision occurs frequently in automobile accidents, yet its pathomechanical process has not been investigated. For the purpose of developing a better seat and head restraint to reduce whiplash injuries in rear-end collisions, we performed impact analyses using finite element models of the human head and neck, and a new neck model in rear-end collisions. A pseudo 3D FEM model using a rear-end collision of 5.7 km/h was prepared. The FEM results showed a higher tensile stress localized in anterior longitudinal ligaments during impact. Compressire stresses localized in soft tissues, reached its maximum value at 140 ms after collision. We also compared the results displacements of head relative to chest with and without headrestraint and head angles on sled test of the new neck model, the dummy and volunteer. It is clear that the new neck model in rear-end collision behaves closer to that of human neck than the conventional dummy neck.

Unbalance Vibration Control of Magnetic Bearing Systems Using Adaptive Algorithm with Disturbance Frequency Estimation.

Abstract: This study is concerned with the adaptive forced rejection approach for a single periodic output disturbance with an unknown period and its application to unbalance vibration suppression in rotor-magnetic bearing systems. A discrete recursive technique is applied to estimate the unknown disturbance period and then to internally and adaptively generate a pseudofeedforward reference signal such that this disturbance is eliminated. Simulations and demonstration experiments are carried out. The results indicate that both the estimation algorithm of an unknown period and reference signal adaptive generation algorithm are stable. Finally, the approach is applied to a problem of unbalance vibration suppression in rotor magnetic bearing systems. Approximately 20dB and 7dB reductions in unbalance vibrations were experimentally obtained in the horizontal and vertical directions of the front and rare sides of the rotor, respectively. The experimental results show that the proposed algorithm is effective for achieving unbalance vibration suppression.

An Approach to the Block Stacking Problem by Multi-Agent Cooperation

Abstract: In this paper we describe a distributed approach to the block stacking problem. Each block is assumed to be an autonomous mobile agent. Motion conflicts among the agents are resolved by means of ( 1 ) motivation calculation which is based on individual goal attainment request, and ( 2 ) promising destination determination by ANN-based behavior function which is trained using an evolutionary programming technique. The proposed method eliminates the necessity for a central planner and exhibits good scalability. Some experiments are carried out and the mechanism for cooperative goal attainment by multiagents is examined.

Control of an Axially Levitated Rotating Motor.

Abstract: In this paper, an axially levitated rotating motor is proposed. It is intended for a disc-type fiat motor so that it has both rotation and axial positioning functions. The rotational control is achieved using a rotating magnetic flux in the stator, while the axial air gap is controlled by changing the amplitude of the rotating magnetic flUX. Three types of disc motors are analyzed theoretically: PM synchronous, induction and reluctance. To confirm the proposed technique, a simple experimental model was setup and tested. The experimental results confirm the validity of the proposed technique that is, the PM motor rotates at up to 6 900rpm, the IM motor rotates at up to 3 835rpm and the reluctance motor rotates at up to 5 100rpm. The axial gap is also controlled by changing the amplitude of the rotating magnetic flux.