Browsing by Author "Chiang, Luciano E."

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    A 3D FEM methodology for simulating the impact in rock-drilling hammers
    (PERGAMON-ELSEVIER SCIENCE LTD, 2008) Chiang, Luciano E.; Elias, Dante A.
    A three-dimensional (3D)finite element approach for modeling impact as it occurs in impact tools used in rock drilling is presented. The model permits one to simulate the energy transmission to the rock, the bit-rock interaction, and the process of rock fragmentation, all of which are important in the study and evaluation of such tools. The finite elements method (FEM) analysis allows one to simulate the impact in 3D stress-strain problems, to consider linear material properties, and to include post failure fracture propagation. Anisotropic elements have been used to model the rock post failure behavior. Infinite domain elements have been used to characterize boundary conditions far away from bit-rock interaction. The accuracy of the model has been evaluated both theoretically by comparing the result to those obtained with a model based on impulse-momentum principle as well as experimentally. (C) 2007 Elsevier Ltd. All rights reserved.
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    A packing problem approach to grasping with a two-finger gripper with application in forest harvesting
    (2024) Caicedo, Yesid A.; Chiang, Luciano E.
    Robotic Hand Grasping is a challenging task that is studied by different researchers, with contributions made to topics such as grasping quality measuring, synthesis, and mathematical models. However, these works usually consider grasping of only one object at time, which is not applicable when the hand must carry multiple objects. Multiple objects grasping problem can be approached as a packing problem, which consists in filling a container with objects of a determined geometry, using the space available in the most efficient way. The aim of this work is to obtain a design methodology for a two-finger gripper that optimizes the grasping capacity of slender cylindrical multiple objects, applying packing problem concepts. This case is of practical importance in grapple claws used in forest harvesting for picking logs. A mathematical model is presented that allows to obtain an optimized geometric configuration of the grapple claw for maximum grasping capacity and packing density for given numbers and sizes of logs. This model is analytically solved for the maximum radius of a set of logs that can be grasped. Alternatively, for a number of logs with a given diameter, the geometric dimensions of an optimized grapple claw can be obtained. The solutions are evaluated using packing density and Active Force Closure (AFC) as quality metrics, to show the benefits of adding them as design criteria in the design multiple objects grapple claws.
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    Automatic dynamic modeling and simulation of underwater vehicles for virtual prototyping
    (JOHN WILEY & SONS INC, 2008) Chiang, Luciano E.; Nunez, Javier A.
    This article describes the theoretical foundations of a software intended for the virtual prototyping of underwater vehicles (UV). The software called Voyager, has a powerful graphics interface for generating the model and subsequently visualizing the results of the simulations. It is written in C++, using the OpenGL graphics engine. (c) 2007 Wiley Periodicals, Inc.
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    Fast Power Coefficient vs. Tip-Speed Ratio Curves for Small Wind Turbines with Single-Variable Measurements following a Single Test Run
    (2024) Corbalan, Patricio A.; Chiang, Luciano E.
    Small wind turbines (SWTs) face tremendous challenges in being developed into a more reliable and widespread energy solution, with a number of efficiency, reliability, and cost issues that are yet to be resolved. As part of the development stages of an SWT, testing the resulting efficiency and determining appropriate working ranges are of high importance. In this paper, a methodology is presented for testing SWTs to obtain characteristic performance curves such as Cp (power coefficient) vs. TSR (tip-speed ratio), and torque vs. omega, in a simpler and faster yet accurate manner as an alternative energy solution when a wind tunnel is not available. The performance curves are obtained with the SWT mounted on a platform moving along a runway, requiring only a few minutes of data acquisition. Furthermore, it is only required to measure a single variable, i.e., the generator output voltage. A suitable physics-based mathematical model for the system allows for deriving the desired performance curves from this set of minimal data. The methodology was demonstrated by testing a prototype SWT developed by the authors. The tested prototype had a permanent magnet synchronous generator, but the methodology can be applied to any type of generator with a suitable mathematical model. Given its level of simplicity, accuracy, low cost, and ease of implementation, the proposed testing method has advantages that are helpful in the development process of SWTs, especially if access to a proper wind tunnel is prevented for any reason. To validate the methodology, Cp vs. TSR curves were obtained for an SWT prototype tested under different test conditions, arriving always at the same curve as would be expected. In this case, the test prototype reached a maximum power coefficient (Cp) of 0.35 for wind velocities from 20 to 50 km/h for a TSR of 5.5.
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    LOCATION AND CLASSIFICATION OF MOVING FRUITS IN REAL TIME WITH A SINGLE COLOR CAMERA
    (INST INVESTIGACIONES AGROPECUARIAS, 2009) Reyes, Jose F.; Chiang, Luciano E.
    Quality control of fruits to satisfy increasingly competitive food markets requires the implementation of automatic visual servo systems in fruit processing operations to cope with market challenges. A new and fast method for identifying and classifying moving fruits by processing single color images from a static camera in real time was developed and tested. Two algorithms were combined to classify and track moving fruits on image plane using representative color features. The method allows classifying the fruit by color segmentation and estimating its position on the image plane, which provides a reliable algorithm to be implemented in robotic manipulation of fruits. To evaluate the methodology an experimental real time system simulating a conveyor belt and real fruit was used. Testing of the system indicates that with natural lighting conditions and proper calibration of the system a minimum error of 2% in classification of fruits is feasible. The methodology allows for very simple implementation, and although operational results are promising, even higher accuracy may be possible if structured illumination is used.
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    Optimal trajectory planning for a redundant mobile manipulator with non-holonomic constraints performing push-pull tasks
    (CAMBRIDGE UNIV PRESS, 2008) Puga, Jose P.; Chiang, Luciano E.
    This work presents a method to generate optimal trajectories for redundant mobile manipulators based on a weighted function that considers simultaneously joint torques, manipulability and preferred joint angle references. This method is applicable to a group of tasks, commonly known as push-pull tasks, in which a redundant mobile manipulator subject to non-holonomic constraints moves slowly while exerting a set of forces against the environment. In practice, this occurs when the manipulator is pulling against an object such as when opening a door or unearthing a buried object. Torque is computed in a quasi-static manner, mainly taking into consideration the effect of multiple external forces while neglecting dynamic effects. The formulation incorporates a criterion for optimizing a starting configuration, and special considerations are made to account for non-holonomic constraints. The application to an existing mobile manipulator is described.
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    Socioeconomic and environmental benefits of substituting firewood with charcoal briquettes produced from biomass residues in the Forestry Belt in Chile
    (2023) Chiang, Luciano E.; Castro, Felipe A.; Molina, Fernanda A.
    An assessment of the potential economic, environmental, and health benefits of substituting firewood with charcoal briquettes as heating fuel in cities located in the Forestry Belt in Chile is conducted. Experimental results obtained by the authors allowed to determine production yields and energy packing of charcoal briquettes obtained from Eucalyptus globulus and radiata pine residues. Given the large annual harvested surface of these two species, large quantities of residual biomass are left available at very low cost. The technology proposed to produce these charcoal briquettes is based in the process of pyrolysis in retort kilns. These give better results than traditional methods used until now in Chile to produce charcoal, but a higher technology level is required. Retort kilns rendered yield ratios of 0.247 and 0.286 [kg of charcoal/kg feedstock] for eucalyptus and radiata pine respectively. Charcoal briquettes gave a LHV (lower heating value) of 7836 kcal/kg and 7975 kcal/kg for eucalyptus and pine forest residues feedstock respectively, about twice that of dry firewood. Our economics analysis renders a cost of 0.1059 USD/kWh, which is competitive against firewood and other fuel options. In terms of health and environmental impact it is estimated that using charcoal briquettes from eucalyptus and pine harvested residues would reduce PM2.5 (particle matter <2.5 mu g) air pollution, the most critical source of contamination in this geographic region, around 7.96 %, saving annually an estimated 9376 tons from being delivered into the atmosphere. An estimated 8.3 % of the annual firewood consumption (966,656 m3/year of which 2/3 is native) would be saved, so that 2041 ha of native deforestation would be avoided.
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    Teaching Robotics With a Reconfigurable 3D Multibody Dynamics Simulator
    (WILEY-BLACKWELL, 2010) Chiang, Luciano E.
    The theoretical foundations of a software package used to teach Robotics by simulation of 3D multibody systems is described. The software called PADROB is based in a methodology that automatically assembles and solves the equations of motion of a 3D mechanism specified according to modeling conventions. The system of equations is time-integrated to simulate the behavior of a multibody mechanism subject to a set of external forces and moments. Models are constructed by specifying bodies and connections (joints) between them, and they easily reconfigurable. (C) 2009 Wiley Periodicals. Inc. Comput Appl Eng Educ 18: 108-116, 2010: Published online in Wiley InterScience (www.interscience.wiley.com): DOI 10.1002/cae.20202
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    VEMERS 2.0: Upgrading of an Emergency Use Ventilator from a Single Mandatory Volume Control Mode of Ventilation (VEMERS 1.0) to 8 Modes of Ventilation
    (2022) Chiang, Luciano E.; Castro, Felipe A.; Sanchez, Tomas F.
    The upgrading of an emergency use ventilator from a single mandatory volume control mode of ventilation (VEMERS 1.0) to 8 modes of ventilation (VEMERS 2.0) is described. The original VEMERS 1.0 was developed in the midst of the COVID-19 crisis in Chile (April to August 2020) following special but nonetheless strict guidelines specified by local medical associations and national health and scientific ministries. The upgrade to 8 modes of ventilation in VEMERS 2.0 was made possible with minor but transcendental changes to the original architecture. The main contribution of this research is that starting from a functional block diagram of an ICU mechanical ventilator and carrying a systematic analysis, the main function blocks are implemented in such a way that combinations of standard off-the-shelf pneumatic and electronic components can be used. This approach has both economical and technical advantages. No special parts need to be fabricated at all, and because of a wider variety of options, the use of extensively field-proven off-the-shelf commercial components assures better availability and lower costs when compared to that of conventional ICU mechanical ventilators, without sacrificing reliability. Given the promising results obtained with VEMERS 2.0 in the subsequent national certification process, the production of 40 VEMERS 2.0 units was sponsored by the Ministry of Science and the Ministry of Economy. Twenty units have been distributed among hospitals along the country. The purpose of VEMERS 2.0, as a low-cost but very reliable option, is to increase the number of mechanical ventilators available (3,000 for a population of 18,000,000) in the country to eventually reach a ratio similar to that of more developed countries. VEMERS is an open-source project for others to use the knowledge gained.
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    VEMERS UC: A Clinically Validated Emergency Mechanical Ventilator for COVID-19 and Postpandemic Use in Low Resource Communities
    (2021) Chiang, Luciano E.; Castro, Felipe A.
    In this article, we present a clinically validated invasive emergency mechanical ventilator developed in Chile called VEMERS UC. It has been clinically tested and validated in intubated Covid-19 patients. Once the pandemic hit Chilean soil in March 2020, it was quite clear that the number of mechanical ventilators available would not be enough. As in other parts of the world many initiatives sprung, most of them naively simple. Chilean medical societies joined engineering specialists and agreed early on in an organized and regulated open process for validating emergency mechanical ventilators, thus allowing for rapid development but with the required functionality, reliability, and safety features. VEMERS UC was one of a few that completed successfully all stages of the validating process, the final test being on five critically ill intubated Covid-19 patients for eight hours each. VEMERS UC is based on an electropneumatic circuit architecture, and its components are all low cost, off-the-shelf pneumatic, and electronic products easily obtained in industrial markets. It works in continuous mandatory volume control mode. The novel technical features of VEMERS UC are discussed here as well as the results obtained in each stage of the validating process. The validating process carried out in Chile is noteworthy by itself, and it could be used as an example in other developing countries. Furthermore, VEMERS UC can be used as a guiding design reference in other countries as well, since this design has already been thoroughly tested in human patients and has proven to work successfully.