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RISS 인기검색어
- 검색키워드
- 저자 : Meseret, S. (검색결과 12 건)
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Meseret, S.,Tamir, B.,Gebreyohannes, G.,Lidauer, M.,Negussie, E. Asian Australasian Association of Animal Productio 2015 Animal Bioscience Vol.28 No.9
The development of effective genetic evaluations and selection of sires requires accurate estimates of genetic parameters for all economically important traits in the breeding goal. The main objective of this study was to assess the relative performance of the traditional lactation average model (LAM) against the random regression test-day model (RRM) in the estimation of genetic parameters and prediction of breeding values for Holstein Friesian herds in Ethiopia. The data used consisted of 6,500 test-day (TD) records from 800 first-lactation Holstein Friesian cows that calved between 1997 and 2013. Co-variance components were estimated using the average information restricted maximum likelihood method under single trait animal model. The estimate of heritability for first-lactation milk yield was 0.30 from LAM whilst estimates from the RRM model ranged from 0.17 to 0.29 for the different stages of lactation. Genetic correlations between different TDs in first-lactation Holstein Friesian ranged from 0.37 to 0.99. The observed genetic correlation was less than unity between milk yields at different TDs, which indicated that the assumption of LAM may not be optimal for accurate evaluation of the genetic merit of animals. A close look at estimated breeding values from both models showed that RRM had higher standard deviation compared to LAM indicating that the TD model makes efficient utilization of TD information. Correlations of breeding values between models ranged from 0.90 to 0.96 for different group of sires and cows and marked re-rankings were observed in top sires and cows in moving from the traditional LAM to RRM evaluations.
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Meseret A. Tadese,Francisco Yumbla,Nabih Pico,Hyungpil Moon 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
A precise dynamic model is critical for collaborative robots to achieve satisfactory performance in modelbased control or other applications such as dynamic simulation and external torque estimation. However, due to nonlinear friction behavior in robot actuation, it is difficult to identify precise dynamic parameters. In this paper, a reliable dynamic friction model, which incorporates the influence of temperature fluctuation on joint friction, is utilized to increase the accuracy of identified dynamic parameters. First, the friction of the joint module is investigated. Extensive test series are performed in the full velocity operating range at temperatures ranging from 23 ℃ to 51 ℃ to investigate friction dependency on joint module temperature. Then, dynamic parameter identification is performed using the inverse dynamics identification model and weighted least squares method. Based on the friction model identified in the first step, friction toque is computed, and the effect is eliminated by subtracting it from experimental data for dynamic parameter identification. Finally, the proposed notion is verified experimentally, and the results demonstrate that using a precise dynamic friction model improves the accuracy of dynamic parameters identification.
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Meseret Hadgu,Habtamu Taddele Menghistu,Atkilt Girma,Haftu Abrha,Haftom Hagos 한국생태학회 2019 Journal of Ecology and Environment Vol.43 No.4
Background: Climate change is believed to be continuously affecting ticks by influencing their habitat suitability. However, we attempted to model the climate change-induced impacts on future genus Rhipicephalus distribution considering the major environmental factors that would influence the tick. Therefore, 50 tick occuance points were taken to model the potential distribution using maximum entropy (MaxEnt) software and 19 climatic variables, taking into account the ability for future climatic change under representative concentration pathways (RCPs) 4.5 and 8.5, were used. Results: MaxEnt model performance was tested and found with the AUC value of 0.99 which indicates excellent goodness-of-fit and predictive accuracy. Current models predict increased temperatures, both in the mid and end terms together with possible changes of other climatic factors like precipitation which may lead to higher tickborne disease risks associated with expansion of the range of the targeted tick distribution. Distribution maps were constructed for the current, 2050, and 2070 for the two greenhouse gas scenarios and the most dramatic scenario; RCP 8.5 produced the highest increase probable distribution range. Conclusions: The future potential distribution of the genus Rhipicephalus show potential expansion to the new areas due to the future climatic suitability increase. These results indicate that the genus population of the targeted tick could emerge in areas in which they are currently lacking; increased incidence of tick-borne diseases poses further risk which can affect cattle production and productivity, thereby affecting the livelihood of smallholding farmers. Therefore, it is recommended to implement climate change adaptation practices to minimize the impacts.
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Hadgu, Meseret,Menghistu, Habtamu Taddele,Girma, Atkilt,Abrha, Haftu,Hagos, Haftom The Ecological Society of Korea 2019 Journal of Ecology and Environment Vol.43 No.4
Background: Climate change is believed to be continuously affecting ticks by influencing their habitat suitability. However, we attempted to model the climate change-induced impacts on future genus Rhipicephalus distribution considering the major environmental factors that would influence the tick. Therefore, 50 tick occuance points were taken to model the potential distribution using maximum entropy (MaxEnt) software and 19 climatic variables, taking into account the ability for future climatic change under representative concentration pathways (RCPs) 4.5 and 8.5, were used. Results: MaxEnt model performance was tested and found with the AUC value of 0.99 which indicates excellent goodness-of-fit and predictive accuracy. Current models predict increased temperatures, both in the mid and end terms together with possible changes of other climatic factors like precipitation which may lead to higher tick-borne disease risks associated with expansion of the range of the targeted tick distribution. Distribution maps were constructed for the current, 2050, and 2070 for the two greenhouse gas scenarios and the most dramatic scenario; RCP 8.5 produced the highest increase probable distribution range. Conclusions: The future potential distribution of the genus Rhipicephalus show potential expansion to the new areas due to the future climatic suitability increase. These results indicate that the genus population of the targeted tick could emerge in areas in which they are currently lacking; increased incidence of tick-borne diseases poses further risk which can affect cattle production and productivity, thereby affecting the livelihood of smallholding farmers. Therefore, it is recommended to implement climate change adaptation practices to minimize the impacts.
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S. Meseret,B. Tamir,G. Gebreyohannes,M. Lidauer,E. Negussie 아세아·태평양축산학회 2015 Animal Bioscience Vol.28 No.9
The development of effective genetic evaluations and selection of sires requires accurate estimates of genetic parameters for all economically important traits in the breeding goal. The main objective of this study was to assess the relative performance of the traditional lactation average model (LAM) against the random regression test-day model (RRM) in the estimation of genetic parameters and prediction of breeding values for Holstein Friesian herds in Ethiopia. The data used consisted of 6,500 test-day (TD) records from 800 first-lactation Holstein Friesian cows that calved between 1997 and 2013. Co-variance components were estimated using the average information restricted maximum likelihood method under single trait animal model. The estimate of heritability for first-lactation milk yield was 0.30 from LAM whilst estimates from the RRM model ranged from 0.17 to 0.29 for the different stages of lactation. Genetic correlations between different TDs in first-lactation Holstein Friesian ranged from 0.37 to 0.99. The observed genetic correlation was less than unity between milk yields at different TDs, which indicated that the assumption of LAM may not be optimal for accurate evaluation of the genetic merit of animals. A close look at estimated breeding values from both models showed that RRM had higher standard deviation compared to LAM indicating that the TD model makes efficient utilization of TD information. Correlations of breeding values between models ranged from 0.90 to 0.96 for different group of sires and cows and marked re-rankings were observed in top sires and cows in moving from the traditional LAM to RRM evaluations.
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Preliminary Connector Recognition System Based on Image Processing for Wire Harness Assembly Tasks
Francisco Yumbla,Meseret Abeyabas,Tuan Luong,June-Sup Yi,Hyungpil Moon 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
In this paper, we analyze and propose a recognition process of plug-in cable connectors for wiring harness assembly tasks using image processing. For manipulation and routing of wire harness, knowing the accurate pose of the cable connector is very critical in the grasping moment. The recognition process is crucial to minimize the error in the manipulation of the connectors. Nowadays, we notice that collaborative robot manipulators or small size industrial robot manipulators attain high accuracy and repeatability levels (sub-millimeter); thus, demonstrate very precise position control capabilities. Using those capacities and with the correct recognition system, we can apply to the automation of the wire harness assembly process. For that reason, we propose a connector recognition system to obtain the precise position of the connectors on a work table; which is necessary to obtain a successful grasping and manipulation of the connectors in a wire harness. The system and the recognition process are explained in detail, and validated experimentally.
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Francisco Yumbla,Meseret Abayebas,June-Sup Yi,Jeongmin Jeon,Hyungpil Moon 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.4
In this study, we propose the use of a distribute manipulator for repositioning and alignment process of cable connectors to obtain the accurate pose of the connector. The accurate pose is critical for a successful mating process in wiring harness assembly tasks. Conventional actuators such as robotics grippers rely on active manipulations; for example, they uses belts and, rollers for the repositioning of the cables, and others such as parallel grippers used directly to grasping the connector. However, all these systems need a lot of many pieces and mechanisms to manipulate the cables or high accuracy control process for grasping the connector in a certain position, thus increasing the difficulty when the cables and connectors are smaller. Therefore, we present a vibrating plate to perform in-hand manipulation to reposition the cable and align the connector. We modeled and analyzed the relationship between the vibration frequency and the velocity of the cable. Furthermore, we experimentally show that the moving velocity of the cable is proportional to the vibration system frequency, and the proposed vibrating plate can reliably move the connector to the desired pose.
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Nabih Pico,Hong-ryul Jung,Juan Medrano,Meseret Abayebas,Dong Yeop Kim,황정훈,Hyungpil Moon 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2
The objective of this work is to control a delivery robot equipped with a passive bogie that can successfully climb up steps of various sizes and move on uneven terrain in outdoor environments. The kinematic model of a six-wheel mobile robot is described in detail. Jacobian matrices and inverse kinematics are obtained to get the velocity of each wheel based on the desired velocity of the robot center of mass in conjunction with the terrain information obtained by the onboard sensors according to the contact angle estimation between the wheel and ground. A slip control is implemented based on slip ratio to adjust the wheel velocity when the slip is detected. Simulation and experimental results verify the effectiveness of the approach that enables the robot autonomously climbing up on different steps and uneven terrain.
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Analysis of the mating process of plug-in cable connectors for the cable harness assembly task
Francisco Yumbla,June-Sup Yi,Meseret Abayebas,Hyungpil Moon 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10
In this paper, we analyze the mating process of plug-in cable connectors for wiring harness assembly tasks by showing the challenging difficulties around this task including the possible solutions: a new gripper design concept and analyzing the permissible error range (tolerance) between the connectors. For wiring harness assembly tasks, knowing the accurate pose of the grasped cable connector in the gripper is very critical for the successful mating process, and conventional mating processes rely on force control or mechanical passive compliance. Nowadays, we notice that collaboration robotic manipulators or small size industrial robotic manipulators attain high accuracy and repeatability levels (sub-millimeter) thus demonstrate very precise position control capacities. Using those capacities of the robotic manipulator, we analyze the permissible error range of connector for the mating process. For that reason, we propose a new design of a gripper for an accurate alignment and holding of the position between the cable and the gripper. Therefore, if we know the exact position of the connector in reference to the gripper, and the tolerance between the connectors is larger than error position of the robot arm, the mating process can be achieved by just using position control of conventional industrial robots.
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