Development of a separable search-and-rescue robot composed of a mobile robot and a snake robot

Abstract

In this study, we propose a new robot system consisting of a mobile robot and a snake robot. The system works not only as a mobile manipulator but also as a multi-agent system by using the snake robot's ability to separate from the mobile robot. Initially, the snake robot is mounted on the mobile robot in the carrying mode. When an operator uses the snake robot as a manipulator, the robot changes to the manipulator mode. The operator can detach the snake robot from the mobile robot and command the snake robot to conduct lateral rolling motions. In this paper, we present the details of our robot and its performance in the World Robot Summit.     

Range image smoothing and completion utilizing laser intensity

In this paper, we propose new denoising techniques for a deteriorated range image taken by a laser scanner. Laser scanner acquires a range value from the scanner to the target by measuring the round-trip time of the emitted laser pulse. At the same time, they can obtain the strength of the reflected light as a side product of the range value. Focusing on the laser intensity, we propose two denoising techniques for a deteriorated range image utilizing the intensity image: smoothing by extended bilateral filter, and completion by belief propagation. The extended bilateral filter makes use of laser intensity in addition to the spatial and range information in order that we can smooth a range image corrupted by noises while the geometric features such as jump and roof edges are preserved. The range image completion technique with belief propagation restores a deteriorated range image using the adjacent range values and the corresponding intensity values simultaneously. We conduct simulations and experiments using synthesized images and actual range images taken by a laser scanner and verify that the proposed techniques suppress noise while preserving jump and roof edges and repair deteriorated range images.     

Biodegradable organic acid-crosslinked alkali-treated gelatins with anti-thrombogenic and endothelialization properties

Gelatins were crosslinked with organic acids and treated with alkali to impart to them endothelialization and anti-thrombogenic properties. These matrices were characterized by biochemical and physicochemical techniques. The amounts of residual amino groups in the matrices decreased with increasing crosslinker concentration. The matrices with the highest crosslinking densities showed excellent endothelial cell adhesion and proliferation. In addition, the adhesion of platelets and formation of fibrin networks on the matrices were suppressed with increasing crosslinker concentration. The matrices also exhibited excellent biodegradability, and the degradation rate decreased with increasing crosslinking density. All the organic acid-crosslinked alkali-treated gelatins showed excellent anti-thrombogenic and endothelialization properties, superior to those of glutaraldehyde-crosslinked alkali-treated gelatins.     

Bone formation following implantation of fibrous calcium compounds (β−Ca(PO3)2, CaCO3(aragonite)) into bone marrow

Bone formation around three types of fibrous calcium-containing crystals has been examined histologically using rats. The implanted materials are (i) calcium metaphosphate (–Ca(PO₃)₂) fibers having aspect ratios of 15–80 with 2–20 m in diameter, (ii) –Ca(PO₃)₂) fibers surface-modified using dilute NaOH and (iii) calcium carbonate (CaCO₃; aragonite phase) whiskers having aspect ratios of 15–40 with 0.5–3 m in diameter. –Ca(PO₃)₂ fibers show a mechanically high strength with a low modulus of elasticity, and the surface-modified fibers have a thin layer consisting of a calcium orthophosphate phase. CaCO₃ whiskers were used for comparison reasons. The materials were implanted for 4, 8, and 12 weeks into bone defects created in the bone marrow of rat tibiae. Cancellous bone formation was observed around –Ca(PO₃)₂ fibers, the surface-modified fibers and CaCO₃ whiskers after implantation for 12, 4 and 4 weeks, respectively. CaCO₃ whiskers were scarcely observed after 12 weeks for resorbing. The calcium phosphate fibrous materials show combined advantages of mechanically high strength for toughening a matrix phase and biological activities; thus, these materials may prove to be useful for novel applications in the biomedical field.     

PLL propagation delay-time influence on linewidth requirements ofoptical PSK homodyne detection

Phase-locked loop (PLL) propagation delay-time influence on optical homodyne detection was investigated both theoretically and experimentally. Applying the Pade approximation, which is often used in the control system, to the calculation of the phase-error variance with the nonzero loop delay time, a high-accuracy analytic expression phase-error variance is obtained. The linewidth requirement with the nonnegligible loop delay time for phase-shift-keying (PSK) homodyne detection is obtained as δν=2.04×10^-3/τ where δν (hertz) is beat linewidth and τ (seconds) is the loop delay time. The linewidth requirement with small delay time approaches δν=6.2×10^-4 R_b where R_b (bits-per-second) is the system bit rate. Results were confirmed by a 10-GB/s optical PSK homodyne detection experiment using external cavity laser diodes. Receiver sensitivity degradations due to loop delay time and beat linewidth are in good agreement with theoretical results     

2 Gbit/s optical CPFSK heterodyne transmission through 200 km single-mode fibre

The amplitude distortion of a continuous phase FSK signal due to fibre chromatic dispersion is measured. We also report a 2 Gbit/s optical CPFSK heterodyne detection transmission experiment. Since there was no chirping degradation, it was possible to transmit the signal through a 200 km single-mode fibre.     

Damping factor influence on linewidth requirements for optical PSKcoherent detection systems

Spectral linewidth requirements for optical phase-shift-keying (PSK) coherent detection systems are found to depend on the phase-locked loop (PLL) parameters. Until now, the damping factor of the PLL has been assumed to be 1/√2 when deriving the required spectral linewidth of a light source, because it is at this value that an electrical PLL offers near optimum performance in many cases. By increasing the PLL damping factor above 1/√2, it is shown that there exists a maximum value of the required linewidth that achieves a received optical power penalty of 1 dB at a bit error rate of 10^-10. The required beat linewidths so obtained are 50% larger than previously reported results (which assume a damping factor of 1/√2). As for PLL frequency acquisition performance, it is shown that raising the camping factor above 1/√2 does not seriously affect the hold-in limit or the pull-in limit. It is also shown that the normalized loop gain that optimizes PLL performance is roughly one half the normalized loop gain at which the PLL oscillation commences