Mitsubishi Heavy Industries (Japan)

The thermomechanical properties of a thin film of shape memory polymer of polyurethane series were investigated experimentally. Based on the experimental results, the dynamic mechanical properties, cyclic deformation properties at high temperature, thermomechanical cycling properties, creep and stress relaxation are discussed. The shape fixity with loading above the glass transition temperature followed by unloading below does not change under thermomechanical cycling. The residual strain is recovered in the vicinity of during the heating process. Several applications of the polymer are introduced.

Controlling robots in contact with the environment is an important problem in industry applications. Generally, a force sensor is used for sensing the external force. It is well known that information of a force sensor has much noise. Furthermore, unstable state is also caused by the narrow bandwidth of force information by a force sensor. This paper shows that stable contact with the environment is difficult when a force sensor is used because of its soft mechanical structure and narrow bandwidth of force sensing. In order to solve the instability of force control, the disturbance observer is implemented instead of the force sensor. The disturbance observer can observe the external force without force sensors. When the disturbance observer is implemented in a robot, a force control system does not include a soft mechanism between a robot and the environment. Since a robot can detect the environmental information directly, a wide bandwidth of force sensing is attained. In this way, this paper solves the problems of force control by considering the force sensing method without changing the control architecture, and the ability of force control is improved. Experimental results show viability of the proposed method

In order to describe the thermomechanical properties in shape memory polymer of polyurethane series, a thermomechanical constitutive model was developed by modifying a standard linear viscoelastic model. The model involved a slip element due to internal friction and took account of thermal expansion. In order to describe the variation in mechanical properties due to the glass transition, coefficients in the model were expressed by a single exponential function of temperature. Several kinds of thermomechanical tests were carried out. The proposed theory expressed well the thermomechanical properties of the material, such as shape fixity, shape recovery and recovery stress. The proposed model is useful for design of shape-memory polymer elements, in which the amount of recovery deformation, the tightening force and the working start and completion temperatures are specified.

In the zero-emission electric power generation system, a multiple-input DC-DC converter is useful to obtain the regulated output voltage from several input power sources such as a solar array, wind generator, fuel cell, and so forth. A new multiple-input DC-DC converter is proposed and analyzed. As a result, the static and dynamic characteristics are clarified theoretically, and the results are confirmed by experiment.

Shape memory polymers (SMP) are lightweight, have a high strain/shape recovery ability, are easy to process, and required properties can be tailored for variety of applications. Recently a number of medical applications have been considered and investigated, especially for polyurethane-based SMP. SMP materials were found to be biocompatible, non-toxic and non-mutagenic. The glass transition temperature (T(g)) can be tailored for shape restoration/self-deployment of clinical devices when inserted in the human body. Newly developed SMP foams, together with cold hibernated elastic memory (CHEM) processing, further broaden their potential biomedical applications. Polyurethane-based SMP are described here and major advantages are identified over other medical materials. Some SMP applications are already used in a clinical setting, whereas others are still in development. Lately, several important applications are being considered for CHEM foams as self-deployable vascular and coronary devices. One example is the endovascular treatment of aneurysms.

Fatigue crack initiation behavior of low-alloy steel in 90 C deionized water was investigated. It was observed that the corrosion fatigue process composed three stages, namely, pit growth, crack formation from the pit, and corrosion fatigue crack propagation. The pit size was found to increase with time (t) following the relation: pit size ∝ t1/3. The crack formation from the pit was determined from the stress intensity factor (linear elastic fracture mechanics parameter), which was calculated by assuming that the pit was a sharp crack. The critical pit condition (ΔK)P was 1.2 MPam for 2.5NiCrMoV and 3.5NiCrMoV in 90 C water containing dissolved oxygen. Using these results, a residual life prediction method for fatigue crack initiation based on in-service inspection was proposed.

The development of system-on-silicon large-scale integration (LSI) devices has significantly influenced the demand for higher wiring connectivity within LSI chips. Currently, increasing the number of metal layers in a multilevel metallization as the device size decreases increases wiring connectivity. In the future, however, designers will have difficulty catching up with the rising demand for higher wiring connectivity by merely increasing the number of metal layers. We propose a new three-dimensional integration technology to overcome future wiring connectivity crises. In our solution, several vertically stacked chip layers in 3D LSI chips or 3D multichip modules (MCMs) are fabricated using our new integration technology. More than 10/sup 5/ interconnections per chip form in a vertical direction in these 3D LSI chips or 3D MCMs. Consequently, we can dramatically increase wiring connectivity while reducing the number of long interconnections.

Segmented polyurethanes containing soft segments with lower molecular weight exhibit shape-memorizing properties. Structure and properties of shape-memorizing polyurethanes (S-PUs) were studied. S-PUs are characterized by a rather high glass transition temperature: Tg of S-PUs is usually in the range of 10–50°C. A Pplot of 1/Tm against–In XA is approximately linear, indicating that the hard segments are randomly distributed along the molecular chain. S-PUs with a hard segment of 67–80 mole % form negative spheruiites; they give a faint scattering maximum in a small-angle X-ray diffraction pattern. On the other hand, S-PUs with a hard segment of 50 mole % form fine birefringent elements, giving diffuse scattering in its SAXD pattern. A cyclic test of an S-PUs above Tg indicates that the residual strain increases and the recovery strain decreases with increasing cycle and maximum strain. It has been suggested by dynamic mechanical investigation that the shape-memorizing property of the S-PUs may be ascribed to the molecular motion of the amorphous soft segments. © 1996 John Wiley & Sons, Inc.

This paper focuses on fault-tolerant control for a battery-energy-storage system based on a multilevel cascade pulsewidth-modulation (PWM) converter with star configuration. During the occurrence of a single-converter-cell or single-battery-unit fault, the fault-tolerant control enables continuous operation and maintains state-of-charge balancing of the remaining healthy battery units. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kW·h laboratory system combining a three-phase cascade PWM converter with nine nickel-metal-hydride battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control.

Including car, truck, bus, and airplane tires, 266 million tires were scrapped in the US in 1996 (Scrap Tire Management Council (STMC), 1997.). More than three-quarters of these tires were used as fuel, recycled for material applications, or exported. The remainder accumulates in junkyards or landfills where they pose a fire hazard and provide a breeding ground for disease carrying rodents and insects. Using information on scrap tire composition and the current markets using them, we examine the technologies used to recover their value either for energy or as rubber. As the majority of scrap tires are used as fuel, we calculate their life cycle energy budget considering both the energy consumed for tire production and the energy recovered from their use as fuel. Based on our findings, we draw some preliminary conclusions on how to maximize value recovery from this ubiquitous artifact of industrial societies.

A bilateral teleoperation experiment with Engineering Test Satellite 7 (ETS-VII) was conducted on November 22, 1999. Round-trip time for communication between the National Space Development Agency of Japan ground station and the ETS-VII was approximately seven seconds. We constructed a bilateral teleoperator that is stable, even under such a long time delay. Several experiments, such as slope-tracing task and peg-in-hole task, were carried out. Task performance was compared between the bilateral mode and the unilateral mode with force telemetry data visually displayed on a screen. All tasks were possible by bilateral control without any visual information. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such a long time delay, and improves the performance of the task.

Since most processes have nonlinearities, controller design schemes to deal with such systems are required. On the other hand, proportional-integral-derivative (PID) controllers have been widely used for process systems. Therefore, in this paper, a new design scheme of PID controllers based on a data-driven (DD) technique is proposed for nonlinear systems. According to the DD technique, a suitable set of PID parameters is automatically generated based on input/output data pairs of the controlled object stored in the database. This scheme can adjust the PID parameters in an online manner even if the system has nonlinear properties and/or time-variant system parameters. Finally, the effectiveness of the newly proposed control scheme is evaluated on some simulation examples, and a pilot-scale temperature control system.

Scheduling theory holds great promise as a means to a priori validate timing correctness of real-time applications. However, there currently exists a wide gap between scheduling theory and its implementation in operating system kernels running on specific hardware platforms. The implementation of any particular scheduling algorithm introduces overhead and blocking components which must be accounted for in the timing correctness validation process. This paper presents a methodology for incorporating the costs of scheduler implementation within the context of fixed priority scheduling algorithms. Both event-driven and timer-driven scheduling implementations are analyzed. We show that for the timer-driven scheduling implementations the selection of the timer interrupt rate can dramatically affect the schedulability of a task set, and we present a method for determining the optimal timer rate. We analyzed both randomly generated and two well-defined task sets and found that their schedulability can be significantly degraded by the implementation costs. Task sets that have ideal breakdown utilization over 90% may not even be schedulable when the implementation costs are considered. This work provides a first step toward bridging the gap between real-time scheduling theory and implementation realities. This gap must be bridged for any meaningful validation of timing correctness properties of real-time applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Single-event upset (SEU) hardness varies across dies, wafers, and lots—even just after fabrication and further across time. Mechanisms of postfabrication variations include total ionizing dose (TID) effects, which are caused by long-term radiation exposure. This synergistic effect of TID on SEU hardness is a particular concern in integrated circuits used in space and nuclear radiation environments. This article shows that an electrical parameter called the data-retention voltage is useful in dealing with such TID effects on the SEU hardness of static random access memories (SRAMs), which are known to be particularly radiation-sensitive. Experiments showed that TID-induced variations in SRAM SEU hardness, i.e., variations in SEU cross sections, were predicted by measuring the data-retention voltage. In addition, these variations were canceled out by adjusting the power supply voltage according to its interesting relationship to the data-retention voltage. Results suggest that it might be possible in flight to predict and cancel out SEU hardness variations caused by TID and other synergistic effects.

Controlling robots in contact with the environment is an important problem in industry applications. In the conventional force control, much research has paid attention to develop novel force control systems and implemented force sensors to detect external force. This paper shows that narrow bandwidth of force sensor has a big influence on the force control system. Generally, to solve the instability in force control, the velocity feedback gain is enlarged. The system becomes unstable with small velocity feedback gain, and robot's response becomes slow with large one. Inasmuch as there is a tradeoff between the stability and the response, it is considered that force control by robots is difficult. This paper proposes a force control system with disturbance observer. It is possible to obtain the force information with wide bandwidth by using the disturbance observer. This paper shows that bandwidth of force sensing is very important for contact motion control. By using the wide bandwidth of force sensing, both stability and response are improved. Furthermore, force control is attainable by the construction of the easiest force control architecture. Therefore, the ideal zero-stiffness-force control is attained. The numerical and experimental results show viability of the proposed method.

In recent years, the realization of a haptic system has been strongly desired in the fields of medical treatment and expert's skill acquisition. The key point of haptics is to realize a vivid presentation of reactive force, particularly in applications that involve touching action. In this paper, a realization of the "law of action and reaction" by multilateral control is introduced. First, an analysis and a design of bilateral control based on the disturbance observer are discussed. A disturbance observer is a basic technology for quarrying of disturbance torque and attainment of robust acceleration control. This paper shows that a four-channel controller which is composed of position control and force control in the acceleration dimension is decomposed into two modes: common and differential modes. A design of bilateral control is treated as position and force control in a single joint. The proposed method generates a good realization of reactive force for the slave side at the master side in bilateral force control. Second, bilateral control is extended and multilateral control is generalized. Multilateral control is designed similarly as bilateral control based on the modal decomposition. Robots with a haptic ability will have an important role in human adaptive mechatronics.

The effect of theanine, one of the components of green tea, on the blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) was investigated by intraperitoneally administering theanine. The effect of glutamine, which is structurally similar to theanine, was also examined. When SHR were injected with various amounts of theanine (0, 500, 1000, 1500, and 2000 mg/kg), the change was dose-dependent, and a significant decrease in blood pressure was observed with the high doses (1500 and 2000 mg/kg). A dose of 2000 mg/kg of theanine did not alter the blood pressure of WKY, while the same dose to SHR decreased it significantly. On the other hand, glutamine administration to SHR did not change either the blood pressure or the heart rate. The brain 5-hydroxyindole level was significantly decreased by theanine administration to both WKY and SHR, the decrease being dose-dependent.

A numerical method employing an upwind finite-difference technique is adopted for an investigation of peristaltic pumping in circular cylindrical tubes. such as some organs in the living body. Various peristaltic flows are calculated under conditions of finite wave amplitudes, finite wavelengths and finite Reynolds numbers, and the influence of the magnitude of these quantities on the flow is investigated. The fluid mechanics of peristaltic mixing and transport are studied in detail by analysing the reflux and the trapping phenomena. The mechanical efficiency of peristaltic pumping is also discussed, with reference to engineering and physiological applications. It is shown that quantitative differences are observed between the results obtained for flows in a circular cylindrical tube and a two-dimensional plane channel. However, for both cases the appearance of peristaltic reflux depends upon the Reynolds number and the wavenumber (mean tube radius/wavelength). Much greater peristaltic mixing and transport are realized in a circular tube than in a plane channel.

Numerical simulations of dynamic stall phenomena around an airfoil oscillating in a coupled mode, in which the pitching and heaving oscillations have some phase difference, have been performed with a Navier ‐Stokes code. The propulsive efe ciency and the thrust have been calculated for various combinations of the phase difference and the reduced frequency for two different amplitude ratios. The effects of the dynamic stall phenomena on the behaviors of the propulsive efe ciency and thrust are discussed in detail by examination of each e ow pattern obtained. Highest efe ciency has been observed for the case in which the pitching oscillation advances 90 deg ahead of the heaving oscillation and the reduced frequency is at some optimum value, for which there appears no appreciable e ow separation in spite of large-amplitude oscillations. For phase angles and reduced frequency other than thisbestcondition, efe ciency israpidly degraded by theoccurrenceof thelarge-scaleleading-edgeseparation.

In order to make clear the relationship between the microstructure of the porous oxide layer and electrochemical properties of air electrodes of solid oxide fuel cells, air/porous oxide/yttria stabilized zirconia, complex‐impedance and cathodic polarization were measured on the electrodes at 900–1000°C with the porous layers of different morphology prepared by different method and different firing temperatures. From the SEM images of the cross section of the interface, the length of the triple‐phase boundary and the area of the closely contacted interface were estimated. It was shown that the reaction rate was essentially proportional to the length of the triple‐phase boundary, while the electrode capacitance was largely proportional to the closely contacted area. Although the reaction rate depended on the electrode morphology, the kinetics of the rate‐determining reaction for small overpotential was found to be essentially the same irrespective of the different morphology of the oxide layer. The electrode interface conductivity at 1000°C for a unit length of the triple‐phase boundary was calculated to be , and the electrode capacitance for a closely contacted area of the oxide/YSZ interface was about 5000 μF cm−2.