Toyota Industries (Japan)

The high-frequency common-mode (CM) attenuation of EMI filters for power converters in electric vehicles is often degraded by the equivalent parallel capacitance between the windings of the CM choke, which limits further miniaturization of the systems. This work presents a simple method to improve CM attenuation by exploiting a metallic casing combined with an injected dielectric material to generate a compensating capacitance around the CM choke. A distributed-parameter model was developed to determine the optimal casing configuration, and the proposed concept was validated through circuit simulations and experimental measurements. The results confirmed that the method effectively enhanced CM attenuation above 1 MHz. Because the metallic casing can utilize the existing converter housing, the proposed approach requires no additional components or cost and provides a practical, compact solution for power converter design.

Owing to their high center of gravity (CoG) and small footprint, two-wheeled robots (TWRs) are expected to be used in collaborative tasks with humans. When a TWR uses its mounted arm to transport a load, its CoG shifts, deteriorating translational control performance. Conventionally, CoG shift is compensated using the torque applied to the arm by the load. However, because the load-weight information is not considered, gravity compensation is insufficient. This study aims to improve translational control performance through precise gravity compensation. The proposed method is a gravity compensator comprising a model-based compensator, which clarifies the physical characteristics, and a model-error compensator, which addresses errors caused by the load weight. A virtual point is also introduced to improve body stabilization and translational control performance. The proposed method enables precise gravity compensation for a TWR and improves its translational control performance. The experimental results demonstrate the robustness of the proposed method in maintaining translational control performance regardless of the load conditions. This compensation method significantly affects the practical deployment of TWRs in human collaborative environments, such as factories and warehouses.

An axis-symmetrical diesel spray flame model coupled with momentum flux distribution measurement was developed as a tool for nozzle orifice development. Momentum flux distributions at several distances from the nozzle orifice exit are measured by a force sensor with a small-diameter aperture which traverses a cross-section. A theoretical momentum flux profile is determined by fitting with the measured momentum flux profile at the cross-section. The spray velocity profile and equivalence ratio profiles are quantified from the theoretical momentum flux profile. By interpolating the profiles of the measured cross-sections, the axis-symmetrical diesel spray flame model can calculate the equivalence ratio and other physical values as a function of the distance from the nozzle exit ( x) and the radius from the spray axis ( r). The equivalence ratio distribution in a cross-section involving the spray axis is converted into soot formation and oxidation distribution by coupling with the improved soot ϕ -T map. The conventional soot-NOx ϕ -T map did not show the borderline between the soot formation and oxidation. To quantify the residence time of the fuel element during soot formation, the narrow soot peninsula was expanded up to its maximum by replacing the soot yield with the soot particle diameter. Instead of contour lines for the of NO mole fraction, contour lines for the OH mole fraction were implemented to reveal the border between soot formation and soot oxidation on the ϕ -T map. The borderline appears clearly, consisting of a horizontal line in the lower-temperature region and a rising line in the higher-temperature region. The converted soot formation and oxidation regions in the axis-symmetric spray flame model exhibit a strong correlation with the measured soot distributions in a quasi-steady diesel spray flame. The shear-stress, which induces turbulence affecting soot formation/oxidation, is also quantified from the velocity distribution.

We demonstrate the functioning of a high-throughput, gate-level-pipelined floating-point adder and multiplier over 50 GHz. The gate-level-pipelined floating-point adder and multiplier requires dedicated circuit blocks to wait until other circuit blocks complete calculations because of the dependence between their sign, exponent, and significand parts. We revealed that the resultant delay difference of the waiting circuit blocks hinders high-frequency operation if the predesigned circuit blocks with the fixed clock distribution are connected in a simple manner. We showed that clock distribution needs to synchronize with every pipeline stage regardless of the circuit blocks to minimize the delay difference between the circuit blocks for circuits containing the waiting circuit blocks (e.g., the floating-point adder and multiplier). We designed a 5-bit floating-point adder and multiplier to demonstrate the effectiveness of the clock distribution experimentally. The test chips were fabricated using AIST 10-kA/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{^{2}}$</tex-math></inline-formula> Advanced Process 2. We verified the high-speed operation at over 50 GHz in the floating-point adder and multiplier. The maximum clock frequency and throughput of the floating-point adder were 56 GHz and 56 GFLOPS, respectively. The corresponding values for the floating-point multiplier were 63 GHz and 63 GFLOPS, respectively.

In this article, we demonstrated a high-throughput gate-level-pipelined 8-bit multiply-accumulate (MAC) unit with a long feedback loop using low-voltage rapid single-flux quantum (LV-RSFQ) logic. The long feedback loop in the MAC unit is an obstacle for high-throughput operation because the logic gates must wait for the delayed inputs from the feedback loop. The LV-RSFQ logic makes high-frequency operation even more difficult by larger and more variable feedback delay. We design the feedback loop by using counter-flow clocking and adding many D flip-flops to divide the long feedback loop into shorter paths. The target clock frequency of the MAC unit with a feedback loop was set to 30 GHz by the experimental results of the MAC unit without a feedback loop. We model the clock frequency and its circuit overhead in a feedback loop to design the feedback loop in the MAC unit achieving 30 GHz with a minimum overhead. The test chips are fabricated using the national institute of advanced industrial science and technology (AIST) 10-kA/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{^{2}}$</tex-math></inline-formula> Advanced Process 2. We have successfully obtained high-throughput 30-GHz operations in the LV-RSFQ MAC unit with a long feedback loop by using the model-based design. The maximum operating frequency of the MAC unit reaches 40 GHz.

Abstract A turbocharger is the device of a car that is used to add extra air into the combustion chambers of an engine. Recently, researches have been conducted on the use of TiAl materials in turbine wheels to replace traditional Ni-based alloys. Since TiAl material has good heat resistance and is lightweight, it is effective in reducing the moment of inertia of the turbine wheel. However, the TiAl material has a problem that it has high viscosity when it is melted and that it is not suitable for precision casting. Even when the thickness of the turbine wheel blades is increased to about 1 mm, the molten TiAl does not always flow to the tip of the mold, and the problem of chipped tip often occurs. In this study, authors investigated the method of manufacturing blades with thickness of more than 1 mm by precision casting in a yield of almost 100%, and then machining them into thin shape of about half thickness by electrochemical machining (ECM). In ECM, it is well known that the flow of the electrolyte affects the machined shape. It was difficult to finish the blade in the desired shape at first and unmachined area remained. Then authors examined the flow of electrolyte using computational fluid dynamics (CFD) analysis and tried to make it appropriate. As a result, a technology was established to machine turbine wheel blades that meet the requirements for shape accuracy and surface roughness in a short time of about 100 seconds.

Receiver tubes are the most important components in high temperature solar thermal energy systems to raise solar thermal conversion efficiency. We have been developing two advanced technologies for more efficient and durable receiver tubes: solar-selective absorber coatings for the metal tubes and hybrid anti-reflective coatings for the glass envelopes. These advanced technologies were integrated into our prototype receiver tubes for operating at 550°C, and their performance with low heat loss of 630 W/m at 550°C was demonstrated.

The addition of carbon nanotubes (CNTs) in polyacrylonitrile (PAN) precursor is an effective way to increase the electrical conductivity of derived carbon fibers. The electrical conductivity of 4.9 × 104 S/m for a PAN-based carbon fiber at room temperature increases to 9.4 × 104 S/m by adding 0.5 wt % CNTs. The measured conductivity for both PAN/CNT- and PAN-based carbon fibers monotonically increases as the temperature increases from 10 and 300 K. An attempt to explain the measured temperature dependences of electrical conductivities by various carrier transport models showed that a simple two-carrier model can give reasonable electron and hole mobility. A monopole antenna fabricated with PAN/CNT-based carbon fibers shows a gain of 2.3 dBi at 2.4 GHz, which is only 0.2 dB smaller than that of a reference (Cu-wire) monopole antenna. This result suggests the possibility of using PAN/CNT-based carbon fibers as antenna elements.

In wireless feedback control systems, reducing packet loss is critical. The use of channel coding may decrease such packet loss; however, redundancy in channel coding also decreases the packet transmission rate although the bit rate remains the same. Thus, control systems are highly affected by disturbances. To improve control system quality, channel coding should be adaptively employed on the basis of packet loss and disturbances. Herein, an on – off error control coding scheme based on the communication and control layers is proposed. In this scheme, channel coding is adaptively used to minimize tracking errors in a controlled plant. Results demonstrate that the proposed on – off error control coding scheme improves the control system’s reference tracking performance compared with that when using a fixed-rate coding scheme.