Ryoichi Toriumi

Tunable solid‐state blue laser differential absorption lidar system for NO2 monitoring

A differential absorption lidar (DIAL) system, based on a tun- able solid-state Ti:sapphire laser, was developed for nitrogen dioxide monitoring in the blue region. Efficient generation of blue light was real- ized by sum-frequency mixing between a Ti:sapphire laser, pumped by the second harmonic (SH) of a Nd:YAG laser, and a second Nd:YAG laser. A maximum output pulse energy of 20 mJ at 453 nm was achieved. In order to reduce the error from the change of atmospheric conditions, the laser wavelength was switched on and off resonance in every shot, and the data were averaged over 500 pulse pairs. As an example of measurement, a spatial distribution of nitrogen dioxide emis- sion from a diesel engine was measured by this DIAL system. The de- tection limit achieved was 0.2 ppm, with a spatial resolution of 12 m.

Tunable solid-state UV lidar system for NO monitoring

A differential absorption lidar (DIAL) system, based on a tunable solid-state Ti:sapphire laser, was developed for nitric oxide monitoring in the UV region. The UV light was generated through second-harmonic generation (SHG) of sum- frequency mixing between a Ti:sapphire laser, pumped by the SH of a Nd:YAG laser, and the fundamental of a second Nd:YAG laser. The output pulse energy of 4 mJ at 226.8 nm with 2 micrometers linewidth was achieved. As a demonstration of DIAL capability, the spatial distribution of nitric oxide emission from a diesel engine was investigated. The detection error achieved was +/- 0.05 ppm up to a distance of 180 m, with the spatial resolution of 20 m.

Tunable, UV Solid-State Lidar for Measurement of Nitric Oxide Distribution

A solid-state differential absorption lidar (DIAL) system was developed for nitric oxide monitoring. The ultraviolet (UV) light was generated through second-harmonic generation, subsequent to the sum-frequency mixing of the pulses from a Ti:sapphire laser, pumped by a frequency-doubled Nd:YAG laser, and from the fundamental of another Nd:YAG laser. The output pulse energy achieved in this way was 4 mJ at 226.8 nm with 2 pm linewidth. This DIAL system made it possible to measure the spatial distribution of nitric oxide emitted from a diesel engine installed at a distance of 130 m from the lidar for demonstration of stack plume, with the detection accuracy of 0.065 ppm with a range resolution of 10 m. We also measured the background nitric oxide of the order of 10 ppb in the urban atmosphere.

Analysis of atmospheric NO x distribution in an urban area by solid state DIAL technique

Atmospheric NOx distribution in an urban area of Japan in winter season were measured by a tunable solid-state lidar system based on a Ti:sapphire laser and a Nd:YAG laser. We show the possibility of long-time air pollution monitoring. We also discuss the reason of the change of NOx concentration by weather conditions.

A Prototype of a Small Tracked Robot for Gas Pipeline Inspection and Maintenance

The gas pipeline networks cover approximately 200,000 km in urban region in Japan. The risk caused by severe leakage, cracking, or corrosion will lead to a big accidence for human. Therefore, the gas pipeline robots for regular inspection and maintenance are very essential for the safe operation and supply of gas. In this paper, as a fundamental study of pipeline inspection robots, a new small wireless tracked robot for gas pipeline inspection and maintenance has been developed. Due to robot’s special kinematics, it is capable of moving in straight pipe, turn at elbow and also climb the inclined pipe flexibly and efficiently. Compared with previous robots, it owns two working modes: self-navigation (automated control) and manual control mode for pipeline inspection. Moreover, a preliminary experiment has been implemented with a typical M-pipeline in 10 cm diameter/4 m length. The experiment results revealed that self-navigation could improve the efficiency of inspection.

Preliminary measurement and analysis of microwave transmission attenuation in small gas pipeline

The gas pipelines need to be inspected in the case of existence of pipelines inner problems. Usually, inspection for leakage of gas pipeline has been carried out by wired probes or wired robots equipped with a CCD camera. However, the above inspection approaches are restricted by the cable in the pipe. This study thus focuses on an inspection approach based on microwave communication. However, obtaining the transmission properties (i.e., transmission loss, RSSI (received signal strength indication), maximum transmission distance, etc) in gas pipeline is crucial to determine which frequency is feasible to the further development. In this paper, a communication system for microwave communication in 2.4 and 5.8 GHz band is developed. Then, the transmission loss and RSSI of these microwaves in 2.5 × 100 cm (straight), 5 × 100cm (straight) and 5 × 200cm M-type curved steel gas pipe (with L-junctions) are then measured. The experimental results revealed that the microwave in 2.4 GHz band owns much stronger communication capability in complicated gas pipeline in consideration of few transmission loss, and three approximate linear functions could be modeled on the basis of the measured data.

A reliable communication and localization method for gas pipeline robot chain based on RSSI theory

Due to the huge microwave attenuation in small steel gas pipelines, the wireless in-pipe robots are unable to complete the inspection and maintenance in long distance. In this research, an approach of a reliable communication and localization method based on Received Signal Strength Indication (RSSI) theory and ultrasonic measurement for gas pipeline robot chain is proposed. Without any GPS modules in the pipe, the robots are able to measure and calculate a certain distance from the adjacent one by detecting and estimating the received wireless signal strength. Such approach enables the all members among the robot chain to cooperate and coordinate, and finally complete the pipeline inspection and maintenance. In addition, this paper describes a “leader-follower” control approach in pipe to support the RSSI-based communication. The leader robot is responsible for the task of whole pipe inspection with wireless remote control by operator, and the follower robots act as the wireless “signal relay station” for communication. Finally, such pipe robot chain cooperate and coordinate together, so that they are able to complete the inspection successfully. We evaluate the performance of the proposed method by using virtual reality simulation. The simulation result indicated that the proposed method could realize the reliable wireless communication and localization for the pipeline robots.

NO Monitoring by a Tunable Solid-State UV

A differential absorption lidar (DIAL) system, based on a tunable solid-state Ti:sapphire laser, was developed for nitric oxide monitoring in the UV region. The UV light was generated through second-harmonic generation (SHG) of sum-frequency mixing (SFM) between a Ti:sapphire laser, pumped by the SH of a Nd:YAG laser, and the fundamental of a second Nd:YAG laser. As a demonstration of DIAL capability, the spatial distribution of NO emission fromadiesel engine was investigated.

Atmospheric NOx distribution monitoring in urban areas using a tunable solid state lidar

Atmospheric NO and NO2 distribution in urban area near the capital city of Japan were measured by an all solid-state differential absorption lidar (DIAL). These were measured over 15 hours in December 1996. According to the wind speed, the concentration show temporal variation in a NO2 case. NOx analyzer data shows a similar behavior to the result measured by the lidar.

Estimation of various atmospheric constituent measurements by using solid state tunable lasers

Detectivities of differential absorption lidar (DIAL) using solid state lasers have been evaluated. Harmonic-generation and mixing of a Ti:Al/sub 2/O/sub 3/ laser and a Nd:YAG laser was considered as a light source, because of its wide-range wavelength tunability from ultraviolet to infrared. Twelve gases were selected for the evaluations because of their importance for the global environment, atmospheric pollution, and industrial gas leakage. As a result, detection limits of H/sub 2/O, CH/sub 4/, and NO/sub 2/ were 4.2 km, 4.1 km, and 1.8 km for average atmospheric concentrations, assuming that S/N=10 is the limit.<<ETX>>