Test Yard Research Articles

UAV-assisted autonomous mobile robot navigation for as-is 3D data collection and registration in cluttered environments

Abstract This paper discusses enabling autonomous mobile robots to operate in unstructured terrain and environments and gather data in a time-efficient manner. In rugged environments such as construction sites and disaster sites, spatiotemporal data is difficult to acquire since these environments are potentially hazardous to humans. Autonomous robot systems represent a reasonable solution to provide topographic and surveillance data that can assist human activity in these environments, whether for exploration, mapping, or search and rescue. However, automatically operating the mobile laser scanning robots at cluttered environments is challenging because as-is geometrical conditions of the site are difficult to comprehend from the ground level due to the blocked line-of-site views. To address the issue, this paper introduces a new framework for operating mobile robots equipped with a laser scanning system in cluttered outdoor environments with the aid of an unmanned aerial vehicle (UAV). To obtain an initial map from the current field, this method first deploys UAV to collect photographic images of a site and builds a point cloud of a3D terrain of the site including obstacle information. A voxel grid is then created from the UAV-generated point cloud, and simulation for laser scan planning is conducted to determine the stationary laser scan positions at which a mobile robot can collect data with less occluded views while capturing crucial geometric information as much as it can. Finally, optimal paths for the mobile robot to navigate among the estimated scan positions are generated. Promising test results were obtained from a real-world outdoor structural material test yard as an example of a cluttered environment. It is expected that the proposed UAV-assisted robotic approach can significantly reduce human intervention and time for data collection and processing and provide technologies to enable cluttered environments to be frequently monitored, updated, and analyzed to support timely decision-making.

Imported wood decomposition by termites in different agro-eco zones of India

Some imported timbers are well known for their durability and their reputation has carried them far from their original homes, although some have not maintained their reputation under different conditions or where new varieties of termites have appeared. It is necessary to know the behaviour of wood species under different environmental conditions and their durability class before the timber or timber product is put into use. The degree of wood deterioration is dependent on conditions such as soil, rainfall, altitude, temperature, and other environmental conditions under which the timber is put to use. Natural durability refers to the ability of wood species to resist attack by different agents, especially biological ones. This paper describes the natural resistance of important imported timber species of India against termites in different agro-eco zones. Field experiments were carried out at six locations falling under five Indian agro-eco zones with the aim of evaluating the natural resistance of 20 species of imported woods. Wood stakes measuring 30.5 × 3.8 × 3.8 cm as per IS:401-1982 standards were implanted in the soil and observed for a period of 4 yr, and visual damage assessment was done. The termites active in the test yard and on the test stakes were collected, preserved in 70% ethanol, and identified using taxonomic keys. Results revealed significant variation in rate of degradation of wood species with climatic zones producing significant variation as well. The tested timbers were categorized into three groups: susceptible, resistant, and moderately resistant. Termites collected belonged to nine species under four genera and the single family Termitidae. Odontotermes obesus was the dominant species in most of the locations.

Development of Fault Location Algorithm and Its Verification Experiments for HVDC Submarine Cables

A new fault location algorithm based on stationary wavelet transform and its verification experiment results are described for HVDC submarine cables in this paper. For wavelet based fault location algorithm, firstly, 4th level approximation coefficients decomposed by wavelet transform function are superimposed by correlation, then the distance to the fault point is calculated by time delay between the first incident signal and the second reflected signal. For the verification of this algorithm, the real experiments based on various fault conditions and return types of fault current are performed at HVDC submarine cable test yard located in KEPCO(Korea Electric Power Corporation) Power Testing Center of South Korea. It proves that the fault location method proposed in this paper is very simple but very quick and accurate for HVDC submarine cable fault location.

Durability of timber of Grevillea robusta (A. Cunn. ex R. Br.) at different ages, grown in dry and wet regions of Karnataka

Experiments were conducted as per BIS Standards to assess the natural durability of timber from 5,10,15 and 20 year old trees of silver oak, Grevillea robusta grown in wet and dry regions (high and low rain fall area) of Karnataka, against brown and white rot fungi under laboratory conditions and against termites under soil burial exposures. All the age group timbers from both the regions fell within the resistant to moderately resistant class when tested against decay fungi under laboratory conditions. Timber from 5 year old trees was destroyed completely by termites within 4 years of exposure in test yard. While 10 year samples showed retention between 35 and 50 %, 15 and 20 year timber samples showed good resistance (80–100 %) up to 3 years of exposure. The susceptibility to termite attack reduced as the age of the tree increased. The termite attack was relatively more in the timber obtained from high rain fall area when compared to that of timber obtained from low rain fall area.

Fault Location Test for HVDC Submarine Cables

The simplified fault location method which is described in this paper is tested at HVDC submarine cable test yard located in KEPCO Power Testing Center of Korea. The total length of tested submarine cable is 194 m, and it has 4 earth points, each point is grounded between shield layer and seawater under the sea respectively. The tested fault location method uses the time delay of the travelling wave signals reflected from the fault point. Firstly, the signals are measured by oscilloscope at the end of test cable when the grounding fault occurs on the system, then the distance to fault point can be calculated using the time delay of the first two signal and propagation velocity.

AC losses of the 5 m BSCCO cables with shield

In order to research the AC loss characteristics of a multi-layered conductor and a shield in a high temperature superconductor (HTS) cable, we prepared two short cable samples, which are the same as the 22.9kV/50MVA HTS-cable installed at Gochang test yard of Korea Electric Power Corporation, and attached voltage-leads to both the conductor and the shield. To investigate the effect of transport period on their AC losses, we also applied current with the same magnitude and opposite direction to the conductor and the shield from a few cycles to several minutes.The tests show that the AC loss measured from the lead attached to the shield (shield-lead) is constant regardless of transport period. But the measured loss from the lead attached to the conductor (conductor-lead) is greatly dependent on transport period. It seems to be caused by difficulty in heat transfer to the surrounding coolant due to thick insulator around the conductor. As transport period becomes longer, the conductor’s temperature rises and thus the AC loss measured from the conductor-lead increases. In addition, the measured loss from the conductor-lead is 1.5 times larger than that from the shield-lead, particularly for the transport period of a few cycles.

Transport characteristics of the 100 m KEPCO HTS cable system for balanced three-phase currents

Since a 100m, 22.9kV/50MVA high temperature superconductor (HTS) cable system was installed at the Gochang test yard of Korea Electric Power Corp. (KEPCO) in 2005, a long-term test has been performed. In this paper, the transport characteristics of the KEPCO HTS cable system were examined by the electrical and calorimetric methods. To analyze the shield current in this system, an equivalent circuit model for the KEPCO HTS cable was suggested, and the calculated shield current compared with the measured one.The results show that the electrically measured total loss, which includes the AC and ohmic losses, corresponds well with the loss measured from the calorimetric method. The measured AC loss of the HTS cable is proportional to the 2.5th power of transport current, and four times larger than the conductor loss calculated from the monoblock model. This is because the conductor’s geometry in the HTS cable is not identical to a cylindrical superconductor in the monoblock model, its temperature rises due to a thick insulator, and the shield loss is included in the measured AC loss. In addition, the measured AC resistance of the current-lead is constant regardless of transport current, particularly in the low current region. Finally, the shield current calculated from our equivalent circuit model is in good agreement with the measured one.

The Results of Installation and Preliminary Test of 22.9 kV, 50 MVA, 100 m Class HTS Power Cable System at KEPCO

As high temperature superconducting (HTS) power cables have some merits over conventional cables, several demonstration projects on the HTS cable system are presently under way around the world. Korea Electric Power Corporation (KEPCO) also initiated an HTS cable project in 2002 with the Korean government's support. A three phase 100 m HTS cable system with a capacity of 50 MVA has been installed at Gochang test yard, located in Chonnbuk province, Korea. The HTS cable system is composed of a 100 m-long cable, two terminations and a cooling system. The rated current is 1,250 A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> and the rated voltage is 22.9 kV considering compatibility with the conventional power distribution system in Korea. Main purposes of this project are to verify the performance of an HTS cable system and to evaluate the potential of the HTS cable system from the viewpoint of power utilities. The real grid application of the HTS cable system requires the demonstration of system reliability, accumulated operation experiences, and it has to meet the practical needs of the utilities. In such a meaning, this project provides various challenges for KEPCO, and the feedback will be delivered to cable manufacturers. This user initiative test will facilitate the introduction of HTS cable systems into a real grid network. The installation process of the HTS cable system and some results of the preliminary test were presented in this paper.

Verification test of 22.9 kV underground HTS cable

Several verification tests are being underway world widely in order to apply HTS cable to real grid. KEPCO (Korea Electric Power Corporation) has initiated HTS cable project since 2002 with the aid of MOCIE (Ministry of Commerce, Industry and Energy), Korea. The HTS cable system with the specification of three-phase, 1.25kArms, 22.9kV and 100m was installed at the KEPCO’s Gochang test yard. In consideration of economical efficiency on retrofit for typical underground cable, the HTS cable was designed to be applicable for 175mm ELP duct and 55m-long cable was laid on underground trench in the same manner as the conventional pulling method. Cool-down to LN2 temperature and warm-up to room temperature were performed several times to investigate the influence of thermal cycle.The main objectives of this project are to verify performance of the HTS cable system and evaluate the economical and technical feasibility from all angles. Expected pros and cons of HTS cable including reliability and maintainability will be assessed with the view point of utilities. This paper summarizes some results of installation and after-laying tests.

Field Test of 3 phase, 22.9kV, 100m HTS Cable System in KEPCO

Starting from investigation of feasibility and basic studies, KEPCO/KEPRI has carried an enterprising project for HTS cable system since 2002. The objectives of this project are to demonstrate HTS cable system and evaluate the feasibility in electricity utility's view. The installation of 100m/3phase/22.9kV/50MVA HTS cable system is undergoing in KEPCO's test yard, located in Gochang, Korea. The HTS cable system consists of 100m long cable, two terminations and a cooling system. To simulate the actual cable installation, the 55m section of the 100m long cable was installed into an underground tunnel. Commissioning test is scheduled at the end of September, 2005 and followed by long term operation test. In this paper, the installation of HTS cable system and initial results of system operation will be summarized

UHV設計送電線への雷撃現象の観測

UHV designed transmission lines have already been in operation at 500kV since 1992. UHV substation equipments have also been energized in the test yard since 1996. For rationalization in insulation design and cost reduction, it is important to evaluate the phenomena of lightning for the UHV designed transmission lines. Some studies to observe current waveshapes have been conducted before, but they were ones conducted on independent towers and do not provide many data in a large-current region. So, we have been observing lightning currents on 60 transmission towers (mainly 500kV lines) since 1994. On UHV-class transmission lines with sections of 500kV-class insulation, lightning observations have been made to study the generation and the propagation of overvoltages into substations. Voltages and currents were recorded at the substations and at junction-tower footings on the UHV system. This paper describes the study of lightning phenomena and EMTP calculations on the UHV transmission lines.

１００ｍ超電導ケーブル実用性検証試験の概要

Since the discovery of High-Tc superconducting (HTSC) materials, elementary technologies of an HTSC cable system have been developed such as the manufacturing technology of a conductor wound with HTSC wires, cold dielectric properties, and thermally insulated pipes. HTSC cable models have also been constructed to evaluate these technologies. As a next step, new test project of a 100m, 66kV/1, 000A/100MVA class, three-core HTSC cable system, integrating these elementary technologies, are planned to verify the practicability of an HTSC cable system as an actual power system equipment. It is a joint project of Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd., and is being conducted in collaboration with the Central Research Institute of Electric Power Industry. The purposes of this project are to prove newly developed technologies satisfying the requirement as actual deployments, to prove manufacturing abilities and installation technologies, and to conduct long-term current-voltage loading tests. The cable consists of three-core conductors placed in thermally insulated pipes having a vacuum insulation layer between them. Each conductor consists of a copper former, superconducting layers, PPLP/LN2 composite insulating layer, and superconducting shielding layers. The cable is placed at a CRIEPI test yard and is bent into U-shape at its center, partially installed into a duct 150mm in inner diameter. The following tests are scheduled, using this cable system, such as an initial cooling test, continuous rated current-voltage loading tests, load fluctuation tests, cooling cycle test between room temperature and LN2 temperature, and overloading and overvoltage withstand tests. Through these tests, problems are expected to be extracted that may be difficult to foresee in individual part tests for development of an actual level HTSC power cable system.

Performance of Urban Rail Transit System: Vibration and Noise Study

Vibration and noise are two major factors in the performance assessment of rail transit systems, particularly in an urban environment where elevated systems are used. A program of field measurements was conducted in Singapore on an elevated section of straight tracks to monitor the rail vibrations and noise generated during the passage of trains. Field measurements included impact hammer tests to determine the driving point impedances of the train wheel and track support system. These tests are relatively easy to perform, requiring only an inverted wheel-set-and-bogie assembly at the workshop and the tracks at the test yard. An analytical train model was developed to predict the level of rolling noise at the wayside of the tracks for comparison with measured levels. The analytical predictions from the model were found to be in good agreement with field measurements. A hybrid approach involving a finite-element model of the track support system and impact hammer test results was also presented to determine the effect of using softer rails pads.

DEVELOPMENT OF TEMPERATURE CORRECTION SYSTEM FOR DEFLECTION BY FWD

Elastic modulus of asphalt mixture depends on temperature. Even though FWD test is carried out at the same point, deflection varies with temperature. Therefore, the temperature correction of deflection and elastic modulus by backcalculation is necessary to get the pavement behavior under the same temperature condition. In this study, temperature correction system with both prediction of temperature and correction of deflection in asphalt layers is developed based on the data in the test yard for FWD. After all, this system is found to be also sufficiently applicable to FWD data in site.

Chemo‐attraction between juveniles of two sympatric stocks of Arctic charr, Salvelinus alpinus (L.), and their gene frequency of serum esterases

Juvenile Arctic charr, Salvelinus alpinus (L.), from two spawning locations, Åbränna stock and Holderströmmen stock, in Lake Torrön, Sweden, were used crosswise as odour donors and receivers in fluvarium tests concerning attraction to stock‐specific odours. The momentary positions of the odour‐receiving charr were recorded with a film camera and filtered flash light (no transmittance &lt; 670 nm). One test fish at a time was placed in the test area to choose in darkness between two water qualities, viz. (i) control tests were run with pure water all over the test yard; (ii) pure water and water having passed 20 specimens of their own stock; (iii) pure water and water conditioned by the presence of 20 specimens of the sympatric stock; (iv) water conditioned by passing 20 specimens of either stock. Specimens of both stocks were attracted to water scented by either stock. The åbränna (AB) but not the Holderströmmen stock (HO) showed significantly stronger attraction to scent of their own stock than to the sympatric stock. This was supported in tests with simultaneous supply of AB and HO‐scented water, when AB significantly preferred the water having passed specimens of its own stock, while HO did not prefer any water quality. Out of 300,65 specimens from each stock were analyzed as to the gene frequency of serum esterases. The HO sample, in contrast to AB, was heterogeneous as the frequency of heterozygotes was lower than that expected under Hardy‐Weinberg equilibrium. No heterogeneity in gene frequencies was observed between AB and HO. The results of both odour attraction tests and the gene frequency analysis points to AB, in contrast to HO, as being offspring from a discrete stock.

Chemoattraction between fry of Arctic char [Salvelinus alpinus (L.)] studied in a Y-maze fluviarium

Attraction of fry of Arctic char [Salvelinus alpinus (L.)] to water conditioned by conspecifics of the same age was studied in a Y-maze fluviarium. Two types of experiments were run. In "up-swimming tests" (1), starting from the common leg of the Y-maze, a single fish was given the choice of entering one of the two upstream arms. In "gradient tests" (2), the momentary positions of a single char were time-lapse photographed in a test yard of this common shank. Strong attraction to conditioned water was observed in both types of tests.