1,634 research outputs found
A Compact Optical Six-Axis Force/Torque Sensor for Legged Robots Using a Polymorphic Calibration Method
This paper presents a novel design for a compact, lightweight 6-axis
force/torque sensor intended for use in legged robots. The design promotes easy
manufacturing and cost reduction, while introducing innovative calibration
methods that simplify the calibration process and minimize effort. The sensor's
advantages are achieved by streamlining the structure for durability,
implementing noncontact sensors, and providing a wider sensing range compared
to commercial sensors. To maintain a simple structure, the paper proposes a
force sensing scheme using photocouplers where the sensing elements are aligned
in-plane. This strategy enables all sensing elements to be fabricated on a
single printed circuit board, eliminating manual labor tasks such as bonding
and coating the sensing elements. The prototype sensor contains only four
parts, costs less than $250, and exhibits high response frequency and
performance. Traditional calibration methods present challenges, such as the
need for specialized equipment and extensive labor. To facilitate easy
calibration without the need for specialized equipment, a new method using
optimal control is proposed. To verify the feasibility of these ideas, a
prototype six-axis F/T sensor was manufactured. Its performance was evaluated
and compared to a reference F/T sensor and previous calibration methods.Comment: 12 pages, 13 figures, 9 table
Flow Characteristics Around Step-Up Street Canyons with Various Building Aspect Ratios
We investigate the flow characteristics around step-up street canyons with various building aspect ratios (ratio of along-canyon building length to street-canyon width, and upwind building height to downwind building height) using a computational fluid dynamics (CFD) model. Simulated results are validated against experimental wind-tunnel results, with the CFD simulations conducted under the same building configurations as those in the wind-tunnel experiments. The CFD model reproduces the measured in-canyon vortex, rooftop recirculation zone above the downwind building, and stagnation point position reasonably well. We analyze the flow characteristics, focusing on the structural change of the in-canyon flows and the interaction between the in- and around-canyon flows with the increase of building-length ratio. The in-canyon flows undergo development and mature stages as the building-length ratio increases. In the development stage (i.e., small building-length ratios), the position of the primary vortex wanders, and the incoming flow closely follows both the upstream and downstream building sidewalls. As a result, increasing momentum transfer from the upper layer contributes to a momentum increase in the in-canyon region, and the vorticity in the in-canyon region also increases. In the mature stage (i.e., large building-length ratios), the primary vortex stabilizes in position, and the incoming flow no longer follows the building sidewalls. This causes momentum loss through the street-canyon lateral boundaries. As the building-length ratio increases, momentum transfer from the upper layer slightly decreases, and the reverse flow, updraft, and streamwise flow in the in-canyon region also slightly decrease, resulting in vorticity reduction
Measurement of Planetary Boundary Layer Winds with Scanning Doppler Lidar
The accurate measurement of wind profiles in the planetary boundary layer (PBL) is important not only for numerical weather prediction, but also for air quality modeling. Two wind retrieval methods using scanning Doppler light detection and ranging (lidar) measurements were compared and validated with simultaneous radiosonde soundings. A comparison with 17 radiosonde sounding profiles showed that the sine-fitting method was able to retrieve a larger number of data points, but the singular value decomposition method showed significantly smaller bias (0.57 m s(-1)) and root-mean-square error (1.75 m s(-1)) with radiosonde soundings. Increasing the averaging time interval of radial velocity for obtaining velocity azimuth display scans to 15 min resulted in better agreement with radiosonde soundings due to the signal averaging effect on noise. Simultaneous measurements from collocated wind Doppler lidar and aerosol Mie-scattering lidar revealed the temporal evolution of PBL winds and the vertical distribution of aerosols within the PBL
Ethyl 4-hydroxy-2,6-diphenyl-1-(2-thiomorpholinopropanoyl)-1,2,5,6-tetrahydropyridine-3-carboxylate
In the title compound, C27H32N2O4S, the thiomorpholine ring adopts a chair conformation and the tetrahydropyridine ring is in a distorted envelope conformation. The molecular structure is stabilized by an intramolecular O—H⋯O interaction and the crystal packing is stabilized by an intermolecular C—H⋯O interaction, generating an S(6) motif and a dimer of the type R
2
2(18), respectively
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