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On-skin stretchable electronic devices that can acquire electrophysiological signals for controllable human-machine interactions are of considerable importance in wearable robotics applications. The straightforward, large-area fabrication of structurally stretchable electronic sensors processed by ultrafast laser ablation techniques provides great insights into low-cost wearable stretchable sensors. In this article, a patch-based large-area frame-type stretchable sensor array system that covers a large portion (∼20 cm wide) of the human arm—processed by a simple, ultrafast (<4 min), user-accessible, mask-independent laser ablation technique—is demonstrated with resolutions down to 50 μm and 100% yield. The Ecoflex_PDMS-PEIE patch—an enabling material of soft (low modulus, ∼50 kPa), reversible adhesion to the skin (∼3.3 kPa), high permeability for water loss (∼8 gm-2h-1), and high stretchability (>100%)—allows the sensor to conformally attach to the skin for long-term usage. The patch-based sensor exhibited robust electromechanical properties under significant mechanical loadings for 10 000 cycles, a promising characteristic for product commercialization. Moreover, the results suggest that the proposed method is suitable for the fabrication of diverse materials for stretchable electronic applications. We verified the application of electromyography signals with human motion determination to control the movements of the robotic hand. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the optimal multi-modes for glucose droplet (GD) sensing depending on sample (glucose droplet) positions in a half-wavelength ($\lambda $ /2) microstrip resonator. Using two different GD positions, i.e., an edge and a center position, in the resonator, the resonant behavior of microwave multi-modes for GD sensing was investigated. GDs with three different concentrations, i.e., 0.1, 0.2, and 0.3 g/ml, were tested in the present experiment. With increasing GD concentration, the ${S}_{21}$ -level of the edge-positional GD gradually was declined at all resonant modes. For a center-positional GD, the frequency not only was deviated into the high-frequency region, but its ${S}_{21}$ -level also gradually was declined for the second and fourth modes. Based on the experimental results, the resonant behavior indicated the edge-(center-) positional GD had the resolution (~0.01/gmL−1 or ~0.05 dB/gmL−1) at the second (second) and third (fourth) modes, respectively. Furthermore, we showed that the edge-positional GD sensing is more suitable when the resonator is associated with an active circuit system, and simultaneous sensing is also possible for different positions in multi-modes. [ABSTRACT FROM AUTHOR]

Fabrication method of a fiber optic electric field sensing probe using polarization maintaining fiber (PMF) is described including a birefringent axes aligning system. The sensing probe is basically a fiber-coupled Fabry-Perot resonator where a thin birefringent wafer of LiTaO3 with an external cavity is mounted onto the end of PMF. An optical wave from a superluminescent laser diode after a linear polarizer parallel to the slow axis of the PMF is made to enter the LiTaO3 crystal with polarization parallel to its extraordinary axis and the reflected optical wave is detected after passing through a polarization analyzer. By measuring a minimum value of a ratio of the reflected optical power at 90° to that of 0° of analyzer, we successfully demonstrated that the angular accuracy of the slow axis of the PMF with respect to the extraordinary axis of the LiTaO3 can be evaluated. Aligning both axes precisely, the electro-optic effect associated with LiTaO3 and polarization is optimized with greater stability. Long term stability of the fabricated PMF sensing probe was enhanced by about 3 times compared to that of a conventional single mode fiber one. As a result of uncertainty analysis, the method we proposed has an overall angular uncertainty of 1° when the used fiber optic components have polarization angle tolerance of 1°. [ABSTRACT FROM AUTHOR]

This article presents a standard field generation system with an antenna for the calibration of a Ka-band electric-field probe. We constructed a measurement system having capability of not only rotating the azimuth angle of the probe but also changing the separation distance between the antenna and the probe. As a result, the orientation and separation distance of the probe can be suggested for minimal variation of the measurand, which reduces the overall uncertainty. For traceable electric-field strength measurements, we measured the associated quantities of the power, antenna gain, and impedance of the individual components constituting the field generation system. An evaluation of the uncertainty of the components providing traceability to the system was also conducted. The system is expected to generate a standard field higher than 10 V/m in the frequency range of 26.5–40 GHz. Uncertainty in the correction factors is quantified to determine the factors that affect the calibration, and the expanded uncertainty of the standard field generation system is found to be 5.1% at 26.5 GHz and 5.3% at both 33 and 40 GHz. [ABSTRACT FROM AUTHOR]

Footstep planning in various three-dimensional environments is formulated as an optimization problem, which is solved using a particle swarm optimi-zation. The objective function for optimization is designed to achieve real-time footstep planning considering arrival at the goal with effective not only foot placements but also walking periods, kinematic constraints: obstacle avoidance and hardware limitations, and dynamic constraints for the bipedal dynamics: stability while walking and feasibility of footsteps in a walking pattern generator. Specifically, optimization objectives are to minimize remaining distance to the goal, lateral movement, rotational movement, and walking period variation. Three penalties are also consid-ered depending on the situations. The first penalty is for obstacle collision avoidance along with prevention of unstable walking due to excessive footstep height variation. The second penalty is for walking satisfying stable zero-moment point condition along with the foot collision avoidance. The third penalty is for feasible footstep planning in a walking pattern generator. Any approxi-mation or precomputation is not required for the proposed footstep planning method. The validity of the proposed method is verified through experiments in various 3-D environments with static and dynamic obstacles. [ABSTRACT FROM AUTHOR]

This letter presents a highly stabilized planar near-field imaging system for millimeter-wave antenna characterization based on dual electrooptic sensors. The issue of system instability, which often occurs in millimeter-wave sensing, is effectively eliminated by employing error correction techniques with field-calibrated probes. This technique compensates for the phase vibration of a radio frequency source by using an additional reference probe. Detailed stabilization techniques for the phase drift are discussed. A probe is also field-calibrated on the W-band so as to provide electric field imaging with the absolute value. W-band horn antenna characterization at 95 GHz is conducted, and the absolute field distribution is compared using the proposed system and a conventional electrical near-field system. A simulation is also conducted. The radiation far-field pattern and gain, calculated from the near-field measurements, are in good agreement with each other according to a comparison of these outcomes. Moreover, a back-projection algorithm with a far electric field as input is utilized to reconstruct the aperture fields of a horn antenna. Finally, a comparison between the measured and reconstructed near-field data with different distances between the probe and the horn antenna is made. [ABSTRACT FROM AUTHOR]

Hopping motion is a prerequisite for running motion, and thus, there have been various approaches for running and/or hopping motion. However, no methods provide an optimal hopping motion for general humanoid robots although the hopping motions have been implemented successfully. Various considerations exist for the optimal hopping of the humanoid robot, and this complicated problem can be formulated as an optimization problem. In this paper, an evolutionary optimization problem for optimal hopping motion of the humanoid robot is formulated to achieve efficient hopping with maximum flight time as well as stable hopping. The validity of the proposed method is verified through a simulation and an experiment with an actual humanoid robot platform. [ABSTRACT FROM AUTHOR]