This paper describes an active electromagnetic levitation conveyance system incorporating a two-degree-of-freedom optimal servo controller. The system uses a mobile stage with an active electromagnet. A state observer estimates the horizontal and vertical position of the levitated object from two Hall voltages and the current and input voltage to the electromagnet. The magnetic levitation uses a state-feedback control based on the estimated vertical position. A conveyance controller must give desired movement while damping undesired sway using the estimated horizontal position. In order to realize it, a two-degree-of-freedom controller combining an optimal servo control with an integral compensator for disturbances is applied to the magnetic levitation conveyance system. In addition it is possible to design the optimal servo gain and the integral compensator gain independently. Sway is minimized by a designed velocity input based on the acceleration and deceleration time of the integral multiple of the natural period. The validity of the proposed method is confirmed by simulation and experiment results.

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Seismic isolation is one of effective and widespread technology that can reduce response acceleration of superstructure. The most popular isolation device is laminated rubber bearing. In general it has linear stiffness against seismic load in the design deformation range. However it has nonlinear stiffness in case of large deformation. That is a hardening property in horizontal direction and a softening property in vertical direction. In the meantime, application of probabilistic safety assessment to seismic evaluation is attracting attention in order to improve seismic resistant reliability. In seismic PSA, accurate numerical simulation is required for not only design basis earthquake but also huge earthquakes that exceed design level. Therefore to express above-mentioned nonlinearity of rubber bearings is required. Thus this paper describes nonlinear simulation of a seismic isolated structure. Both the hardening characteristics of horizontal direction and the softening characteristics of vertical direction are expressed by multilinear models. Additionally the analysis model of horizontal direction considers a habituation effect of rubber. Response of nonlinear simulation is compared with linear simulation. As a result, it was confirmed that nonlinearity of rubber bearings debases the isolation performance.

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In order to prevent and treat arterial sclerosis, a quantitative measurement method is required. The measurement results in daily environment give important information for diagnosis and treatment. In medical institutions, pulse wave velocity (PWV) is used for screening of arterial sclerosis. However, a measurement device for daily environment was yet to be developed. Therefore, the purpose of this research is to develop an easy to use device for PWV measurement in order to perform the screening index of arterial sclerosis for daily use, and to confirm a relationship between PWV that measured with our device and the existing index for screening. We proposed using only an electrocardiogram (ECG) and a photoplethysmogram (PPTG) for the PWV measurement in order to develop an easy to use device. And the device used wireless communication in order to be the least restraintful as possible. We carried out two experiments with the device. An experiment is to confirm the measurement accuracy. Another is to confirm the relationship between the PWV and the existing index. As a result of the experiment of the measurement accuracy on 8 subjects, the average of the coefficient of variation was 2.34%. And result of the experiment of the relationship on 28 subjects showed a significant correlation (r=0.707, p<0.001) between the PWV and existing index for screening. Hence, we developed the easy to use and non-restraint device and the device was able to measure the PWV with high accuracy, conformed by the high correlation with existing index.

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This paper presents an improved formulation on the evaluation of the axial elastic force in three-dimensional Bernoulli-Euler beam element based on the absolute nodal coordinate formulation. An accurate measure of mean axial strain for evaluating the axial elastic forces characterizes the presented formulation. The presented formulation evaluates the mean axial strain accurately by calculating the length of deformed beam element along its neutral axis. A comparison of the conventional formulations of the axial elastic force and the presented formulation of that is performed in some numerical examples which contain large rotation and large deformation of flexible beam. As a result, it is verified that the presented formulation can express large deformation accurately with smaller number of elements than the conventional formulation which calculates the mean axial strain with straight-line distance between both element nodes. Moreover, it is also verified that the presented formulation can avoid excessive increase in computing time to simulate the dynamic behavior of flexible beam.

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This research proposes reduction in the amplitude of the primary resonance combined with the parametrically excited horizontal oscillation in a High-Tc superconducting levitation system. High-Tc superconducting levitation systems have very low damping and stable levitation without control. However, in such low-damped systems, complicated phenomena of dynamics can be easily generated by nonlinearity of the magnetic force. Our previous research showed that, when the frequency of vertical excitation is in the neighborhood of double the natural frequency in the horizontal direction, horizontal oscillation can occur parametrically through nonlinear coupling between vertical motion and horizontal motion. This research discusses on effects of the parametrically excited horizontal resonance on the primary resonance. We discussed possible nonlinear interaction called internal resonance between the vertical motion and the horizontal motion whose natural frequency is chosen as half that of the vertical motion. The primary resonance reduction based on this mechanism was successfully verified numerically. This kind of nonlinear oscillation can be useful for reducing resonance of a high-Tc superconducting levitation system.

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Damping in acoustics means sound absorption. In this paper, a theoretical analysis of the one-dimensional wave propagation in the damping medium is discussed. First, it is shown that density in complex number is derived by adding the viscous damping force and the inertial force of the fluid. This results in that the propagation velocity and the wave number are also complex numbers, and the imaginary part of the complex wave number is always negative. Therefore, distance decay occurs in the damping medium. In case of undamped medium, natural modes are formed while traveling wave and the reflected wave are superimposed in one-dimensional acoustic tube. Both the eigenvalues and natural modes are real numbers. If the damping is assumed to be Rayleigh damping, complex eigenvalues and real natural modes occur. However, if the excitation vibration pattern is not valid, natural mode is never excited. So, excitation vibration pattern is considered to excite the natural modes. Numerically calculations are achieved in different two ways of measuring propagation speed. One is time decay of damped natural mode, and the other is distance decay of forced vibration.

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A waveform of a pulse wave in a blood vessel often changes because of nonlinear effect. To analyze this nonlinear phenomenon, the finite difference method has been used. However, the treatment of the method is cumbersome. In order to overcome this problem, we propose a concentrated mass model to analyze the nonlinear pulse wave problems. This model consists of masses, connecting nonlinear springs, connecting dampers, base support dampers, and base support springs. The characteristic of connecting nonlinear spring is derived from the relationship between pressure and diameter of a blood vessel, and the base support damper and the base support spring are derived from the shear stress from a wall of a blood vessel. The pulse waves in the blood vessel of the dog measured by Laszt are analyzed numerically by using the proposed model in order to confirm the validity of the model. Numerical computational results agree very well with the experimental results. Especially, “steepening phenomenon” generated by the nonlinear effect of fluid is numerically reproduced. Therefore, it is concluded that the proposed model is valid for the numerical analysis of nonlinear pulse wave problem.

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This paper presents the kinematic analysis of a log-rolling robot which controls its attitude angle and position of the log by frictional forces between the wheels and the log. In order to analyze the influence of the frictional forces, equations of motion including normal forces and friction forces are obtained by setting a small displacement to the contact point between the wheels and the log. Upper limits of the control input are derived from no-slip conditions. The control gains are set in order not to exceed the upper limits. Experimental studies have been executed to verify the proposed control algorithm.

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Wheels have high movement efficiency, simple structures and low cost. So various wheeled mechanisms are used in the living space. However, wheels have low traveling performance. Therefore, there are areas that wheeled mechanism can't move in. In order to solve this problem, various movement mechanisms are developed. Yet, they have many problems. For example, complicate, heavy, large, expensive, and so on. Because of these reasons, the spread of these movement mechanisms are blocked. Then, we propose TFW that have high performance of driving on level surface and traveling over a single step. Movement mechanisms that are equipped with TFW can travel over steps that conventional wheeled vehicle can't travel over. Consequently, we showed that TFW have high performance movement mechanism of level running and traveling over steps by experiments with a vehicle “SRIDER-II”.

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It is difficult to recognize each of coil springs randomly placed in a pile by conventional machine vision techniques because of their shape characteristics such as a succession of identical shapes and a complicated outline. In this paper, we propose a method of recognition and pose estimation of coil springs using their highlights made by illumination with stereo vision. In this method, we extract and discriminate their highlights. They are grouped into highlight groups in left and right images so that a highlight group includes highlights that belong to a coil spring. Then, we find correspondence between left and right highlight groups to estimate the pose of coil springs by stereo vision. We implemented this method as a bin-picking system with an industrial robot. Bin-picking of coil springs was almost successful on the system. A main reason for picking failure was collisions between the fingers of the hand and the part box, and those between the fingers and other coil springs. Therefore, implementation of collision avoidance would make bin-picking more reliable.

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In this study we make clear the dynamic characteristics of a vibration isolator with three degrees of freedom, two degrees of freedom in vertical rotation and one degree of freedom in vertical translation. The isolator consists of four air suspensions with slit restrictions and reservoir tanks. To minimize resonance amplitude, the damping ratio, which corresponds to the restriction coefficient of the slit restriction, has to be chosen in order to equalize the resonance amplitude when the lowest mode of vibration is excited to that of the highest mode of vibration. The resonance amplitude can be decreased by bringing the natural frequencies closer together. Furthermore, we derive a system of nonlinear equations whose solution corresponds to the damping ratio of the air suspension to decrease the resonance amplitude. It is shown that the relative difference between the analytical solution and the optimal damping ratio for minimizing the resonance amplitude is below 0.07 %.

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It is very important to understand the dynamic characteristics of machinery and experimental modal analysis is widely used as a basic tool for machine design. Various methods to identify the modal parameters of structures by the vibration test have been proposed. Recently, the frequency domain subspace method employing frequency response functions has been developed. In general, it is easier to overview the dynamic properties of structures in frequency domain than in time domain. In this paper, the modal parameters are identified by the frequency domain subspace algorithm and the residual terms derived from rigid body motions are considered. The Akaike Information Criterion is used because of the importance to determine the model order, which is related to the order of the state space model derived by the subspace method. The proposed procedure is then applied to identify the modal parameters of an aluminum circular plate with a hole.

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For the control of mechanical systems including discrete-valued devices such as discrete-level actuators and communication encoders, one of the promising approaches is to utilize dynamic quantizers. Here, the dynamic quantizer is a device which converts continuous-valued signals into discrete-valued ones depending on the past signal data. This paper focuses on a dynamic quantizer design problem which is to find a quantizer such that the output behavior of systems with quantizers is similar to that of ideal systems without quantizers. In this paper, we first formulate a design problem of fixed-order dynamic quantizers under several constraint conditions such as stability of quantizer, control input saturation, and pole assignment. Then, for getting a solution to the problem, we present an easy-to-use quantizer design method based on particle swarm optimization (PSO) which is a swarm intelligence technique and is one of the evolutionary computation algorithms. Finally, it is verified that the PSO based method gives satisfactory fixed-order dynamic quantizers through several numerical examples with a cart positioning system and an unstable mechanical system. Further we conclude that the proposed method could be an useful tool for the design of dynamic quantizers.

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Sound transmission loss is relatively small in thin louver boards with a high aperture ratio. This study investigated louver elements with a sound attenuating function. Using narrow tubes, an array silencer was built into composite louver boards and a high aperture ratio was maintained. Several constructions for such louvers were prototyped, measured, and analyzed theoretically. Sound transmission loss was measured using four-microphone impedance tube. Then, sound transmission loss was calculated by a transfer matrix based on one-dimensional axial coordinate system analysis. The attenuation of sound in tubes should be calculated because a thin louver board must comprise narrow tubes. Therefore, an accurate propagation constant and a characteristic impedance based on two-dimensional analysis were introduced to enable theoretical analysis. The calculation results, including attenuation, and the experimental results had good coincidence. Moreover, the theoretical analysis confirmed that the silencer worked effectively and could be applied to silencer designs.

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Measurement of pressure distribution in gaseous pipeline is important from a view point of control or safe management. In the present paper, a linear Kalman filter is developed to estimate the pressure estimation of small amplitude pressure wave in a single straight gaseous pipeline with constant circular cross section. The Kalman filter uses the linear dynamic system of the pipeline derived by using the approximation method of the unsteady friction, high speed and accurate computing method. The inputs to the Kalman filter are inlet and outlet pressures, and the pressure at the point one third of the pipe entrance is used as the observation point for feedback compensation. The performance of the developed method is tested using two experimental results by comparing with calculation results without feedback compensation. The comparison demonstrated that the developed method has better performance in the presences of measurement noise and erroneous boundary condition than does the ordinary calculation. It also showed much higher ability in error reduction than the ordinary calculation in computation with an erroneous initial condition.

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This study examines a controlled variable for the steering control of two-wheeled vehicle using Steer-By-Wire (SBW) technology. Computer simulation using a simple vehicle model with two cases, the controlled variable is the rolling angle or the yaw rate, are examined. The rolling angle control realizes the good tracking performance to the desired rolling angle, while it deteriorates the yaw rate damping and makes the transitional large steering torque input. The yaw rate control performs the good damped response, while the tracking performance to the desired yaw rate is limited. A novel controlled variable is proposed with a linear combination of the rolling angle and the yaw rate. Controlling this controlled variable realizes not only the good tracking performance, but also the damped vehicle response.

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For dynamic control of a robot, a torque/force control will be necessary because the robot model is represented by a dynamic equation. A torque/force control requires a torque/force sensor or a current sensor(for DC servo motor) for feedback loop, however, they occupy large volume and weight or have low precision and time delay. Therefore, the robot system sometimes has a local position control in the motor drivers from the safety point of view. In this paper, we propose a design method of position-based dynamic control using an autonomous control method based on an orbit attractor, which is realized by a simple deformation of the conventional algorithm. In addition, for the orbit attractor control, it is necessary that an orbit of the state variable is not crossing in the state space. When the orbit is very close, vector field of the orbit attractor along the orbit can not be defined correctly. A dimensional expansion of dynamics is also proposed to design a controller. These methods are evaluated by experiments using a two-dimensional biped robot.

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This paper focuses on the development and the feedback control of the trident snake robot which is an example of nonholonomic mobile robots. The robot is composed of a triangular body and three branches which have passive nonslide wheels. In this paper, we first develop a double-linked trident snake robot and its control experiment system. Then, we propose a feedback control algorithm for achieving rotation and translation motion of the robot by extending the feedforward control theory proposed in a previous work. Here, rotation motion is to change the orientation of the robot without changing position and joint angles; translation is to change the position of the robot by changing neither orientation nor joint angles. Finally, we evaluate the effectiveness of the proposed method by control experiments with the developed trident snake robot.

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As described in this paper, we specifically examine a point-to-point (PTP) motion task of mechanical systems and present a simple trajectory generation method for suppressing the residual vibrations. In the proposed method, a PTP motion trajectory is generated by giving the output of a power series of time as the input of a cycloidal function. The generated trajectory depends on the coefficients of the power series. To cancel unwanted vibration, the coefficients are tuned by metaheuristic algorithms. The residual vibrations of mechanical systems can be suppressed by driving along the obtained trajectory, that is, the proposed vibration control method is a feedforward control technique. We deal with the PTP motion of an overhead crane with load hoisting, and demonstrate the effectiveness of the proposed method through numerical simulations. Furthermore, the proposed method is also applied to simultaneously minimize the residual vibration and the operating energy in a single-link flexible manipulator. The results obtained from this application consolidate the validity of our approach.

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We have been investigating small and high-strengthened single threaded worm gear. Previous our studies have shown that reducing thickness of worm tooth on addendum face enlarges elastic deformation of worm wheel. This proposed profile has advantages on improving contact ratio, gear efficiency, strength against impact force and fluctuation in torque. Though we have modified the profile of worm, we have not reported on a profile of worm wheel. In this paper, we propose the MUB theory that new profile of worm wheel improve contact ratio without increasing tip diameter of worm wheel. At first, we focused on meshing under base circle of worm wheel, and investigated geometrical shape on dedendum face manufactured by hob cutter. As a result, we derived formula of new profile of worm wheel for meshing under base circle. In addition, the MUB theory was verified by the experiment that used an actual worm wheel with MUB profile. It was shown that we obtained a new finding by the process of this research.

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In this paper, a parameter-free shape optimization method is proposed for designing the smooth optimal free-form of a 3D framed structure. A stiffness design problem where the compliance is minimized under a volume constraint is solved as an example of a shape design problem. The optimum design problem is formulated as a distributed-parameter shape optimization problem under the assumptions that each member is varied in the out-of-plane direction to the centroidal axis and the cross section is prismatic. The shape gradient function and the optimality conditions for this problem are then theoretically derived. The optimal curvature distribution is determined by applying the derived shape gradient function to each member as a pseudo distributed force to vary the frame, while minimizing the objective functional. We call this method the free-form optimization method for frame, a gradient method in the Hilbert space. The validity and practical utility of this method were verified through several design examples. It was confirmed that axial-force-carrying structures was obtained by this method.

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The transmission gear ratio of the power transmission device is determined with pair of numbers of each tooth. Since the minimum number of teeth was decided, when the center distance was fixed, change of the transmission gear ratio was difficult. In this research, it was tried to combine the gear and traction drive system utilizing commercially available angular ball bearings. The traction drive system utilizing angular ball bearing has function which reduces rotational speed and supports gear reaction force. The traction drive system features an input shaft and inner ring with a fixed outer ring and a retainer as the output shaft. The retainer of the angular ball bearing and output shaft were unified and it could reduce using the difference in the rotational speed of the inner ring and a retainer. Axial preload was added to the angular contact ball bearing with the compression spring. When both gear reaction force and axial preload were added to the traction drive system, angular ball bearing was selected so that the output torque might be to 20Nm. As a result of the experiment, by giving axial preload 1800N, theoretical transmission gear ratio was attained, and it has operated to 20Nm of output torque. The transmitting efficiency has confirmed that it was about 76.9% by the double reduction of the gear and the traction drive system.

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Recently, demand for minimally invasive surgery has rapidly increased, especially in the spinal surgery. Surgical resections of spinal column, namely, backbone are frequently conducted using a diamond grinding stone and a high-speed spindle tool in the surgery. The resections have often brought serious nerve root heat injury, because high heat is generated in grinding point close to the nerve root. To address this issue, many studies such as investigations of machining characteristics of bone have been conducted, and various medical technologies and devices such as a coolant supply method have been proposed and developed. However, requirement for suppressing the heat injury in the spinal surgery has currently exceeded the capabilities of the above technologies and devices. To overcome this problem, grinding experiments on bone were performed using commercial diamond grinding tools for clarifying the grinding characteristics. Based on the results that clogging on the tool surfaces is a dominant issue of generating high heat in wet grinding, diamond grinding tools coated by titanium oxide were developed in the hopes of decreasing the clogging by improving hydrophilic property of the tool surface. Grinding experiments showed that the newly developed grinding tools successfully suppressed the clogging and kept the grinding temperature below a critical level for the surgery operation, as compared with the commercial tool.

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Recently, the issue of resources drying up and environmental problems have become more and more serious, and interest has been growing in methanol as an alternative fuel. As a result, in this paper, the cylinder tribology in a small two-stroke engine using methanol fuel and gasoline fuel was studied. An experiment was conducted with an engine and simulated sliding equipment. After the operation was repeated at regular time intervals, the amount of wear of the cylinder wall was investigated. Results show that the wear for methanol fuel was smaller than that for gasoline fuel. To investigate the difference why, the viscosity and Thermo Gravimetry (TG) properties of oils on the cylinder walls were analysed. Simulated sliding tests to imitate the engine case to test lubrication conditions were also carried out. Methanol fuel shows higher viscosity and lower friction due to sustaining the oil film on the cylinder wall. The reduced wear with methanol fuel measurements could be obtained.

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The machining of complex parts with the non-axisymmetric surface is persuaded by the conventional multi-axis milling machine and/or the grinding machine. Even though the machining is persuaded by the high speed cutting method, it takes long time to machine this process because the contact part between 3D surface and milling tool or grinding wheel is calculated for the tool pass that is just same as turning method. Therefore, to improve the productivity of this process, a new cutting process instead of the milling process or grinding process has been developed. We try to apply the turning process for 3D surface machining. The key factor for the turning of 3D surface is to speed up the motion of the tool post on the moving table compared with the one of the multi-axis milling machine or the grinding machine. To cope with the turning, the dedicate NC program for 3D surface by the original CAM system has been developed based on the proposed turning method. The creation of NC program including some data conversion processes from the 3D-CAD system are needed for building up tool trajectory. To create efficient and exact tool trajectory data, these conversion processes is calculated directory from the 3D surface in 3D-CAD system. It makes our original CAM system possible to extract the simple and reliable tool path for the NC program. In this report, a new turning method is proposed and the machining results based on the proposed method are reported. The performances of the control results of the CNC lathe are also evaluated by measuring the table behavior.

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The conical involute gears have been applied to automotive parts such as 4WD transfer. To apply for automobile, high capacity and higher quietness are required. In general, the tooth contact of conical gear pair is point contact, hence the large ease off happens even though each tooth surface has no manufacture error. From this characteristic, the tooth surface durability of conical gear pair is thought to be generally weak. To clarify the tooth surface durability of conical gears we develop the evaluation method of tooth contact stress distribution on conical gear surface taking an ease off shape and a tooth surface modification into consideration and evaluated the pitting life by the maximum contact stress with this method. The relationship between the maximum contact stress and pitting life can be plotted on the pitting S-N curve of conventional cylindrical gears. The edge contact found often cylindrical gear surface at heavy load isn't found on conical gear surface because of large ease off shape.

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As heat sources of a compact CNC lath are closely-arranged, they would cause large and complicated thermal deformation. Thus, compact CNC lathes often arrange the heat sources and so on to reduce thermal deformation. The lathes taking such arrange into consideration can show high-precision work under stable environment. On the other hand, it would cause large thermal deformation at unstable environments. Previously, we proposed a simple method to compensate thermal deformation of CNC lathes by measuring temperatures at a few points such as spindle and tool. In order to apply similar method to a compact type lathe, we evaluated its thermal deformation. As a result, the thermal deformation of the evaluated machine is affected by the hydraulic unit as well as the spindle part. Thus, we tried to approximate the thermal deformation caused by the hydraulic unit and the spindle part respectively. Then, those thermal deformations can be expressed by simple equations. Furthermore, we applied these equations to compensate thermal deformation of the lathe. As a result, it is confirmed that the work error can be reduced under various conditions.

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This paper proposes a new representation approach to magnifying the contouring errors of a polygonal planar profile composed of short linear segments. In comparison with other methods, the proposed approach requires the less computation work in date operation process and enables to employ a larger magnification constant under a condition of effectively preventing the occurrence of jumping loops in obtained error curves. The practical examples, for evaluating the motion trajectory error of a machining center and the machining error of a finished work piece, are presented together with detailed discussions. These examples sufficiently illustrate the effectiveness of the proposed approach.

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[in Japanese]

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