Standalone docking station with combined charging methods for agricultural mobile robots

One of the biggest concerns in the field of agriculture is around the energy efficiency of robots that will perform agriculture’s activity and their charging methods. In this paper, two different charging methods for agricultural standalone docking stations are shown that will take into account various variants as field size and its irregularities, work’s nature to which the robot will perform, deadlines that have to be respected, among others. Its features also are dependent on the orchard, season, battery type and its technical specifications and cost. First charging base method focuses on wireless charging, presenting more benefits for small field. The second charging base method relies on battery replacement being more suitable for large fields, thus avoiding the robot stop for recharge. Existing many methods to charge a battery, the CC CV was considered the most appropriate for either simplicity or effectiveness. The choice of the battery for agricultural purposes is if most importance. While the most common battery used is Li-ion battery, this study also discusses the use of graphene-based new type of batteries with 45% over capacity to the Li-ion one. A Battery Management Systems (BMS) is applied for battery balancing. All these approaches combined showed to be a promising method to improve a lot of technical agricultural work, not just in terms of plantation and harvesting but also about every technique to prevent harmful events like plagues and weeds or even to reduce crop time and cost.Project PrunusBotinfo:eu-repo/semantics/publishedVersio

Fast return path planning for agricultural autonomous terrestrial robot in a known field

The agricultural sector is becoming more critical than ever in view of the expected overpopulation of the Earth. The introduction of robotic solutions in this field is an increasingly researched topic to make the most of the Earth's resources, thus going to avoid the problems of wear and tear of the human body due to the harsh agricultural work, and open the possibility of a constant careful processing 24 hours a day. This project is realized for a terrestrial autonomous robot aimed to navigate in an orchard collecting fallen peaches below the trees. When it receives the signal indicating the low battery, it has to return to the docking station where it will replace its battery and then return to the last work point and resume its routine. Considering a preset path in orchards with tree rows with variable length by which the robot goes iteratively using the algorithm D*. In case of low battery, the D* algorithm is still used to determine the fastest return path to the docking station as well as to come back from the docking station to the last work point. MATLAB simulations were performed to analyze the flexibility and adaptability of the developed algorithm. The simulation results show an enormous potential for adaptability, particularly in view of the irregularity of orchard field, since it is not flat and undergoes modifications over time from fallen branch as well as from other obstacles and constraints. The D* algorithm determines the best route in spite of the irregularity of the terrain. Moreover, in this work, it will be shown a possible solution to improve the initial points tracking and reduce time between movements.Project PrunusBot - Sistema robótico aéreo autónomo de pulverização controlada e previsão de produção frutícola (autonomous unmanned aerial robotic system for controlled spraying and prediction of fruit production), Operation n.º PDR2020-101-031358 (leader), Consortium n.º 340, Initiative n.º 140 promoted by PDR2020 and co-financed by FEADER under the Portugal 2020 initiative.info:eu-repo/semantics/publishedVersio

Modeling the heat transfer and the pressure loss in flat fin-and-tube compact heat exchangers

This work has been supported by the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors wish to thank the opportunity and financial support that permitted to carry on this project.Fin-and-tube heat exchangers (HX) have wide application in the industry. The study of HXs with reduced tube diameter has allowed the development of more compact and equally efficient equipment. Most of the HXs of this type are composed of flat fins, not only due to the ease of construction but also to their reliability in long-term operation and reduced friction characteristics. The formulation of mathematical equations that predict the effect of the geometric characteristics on the heat transfer and friction factors of the HXs lead many researchers to try to establish correlations that approximate the experimental results. In this paper is developed a computational tool based on literature correlations is used to evaluate the Colburn and friction factors for flat fin-and-tube compact HXs. The results of predictions show the Colburn and friction factors behavior for different geometrical parameters (fin pitch, tube diameter, tube number) and typical Reynolds number.info:eu-repo/semantics/publishedVersio

A review

It is widely known that defrosting operation on commercial refrigerators is one of the main causes of inefficiency on these systems. Several defrosting methods are used nowadays, but the most commonly used are still time-controlled defrosting, usually by either electric resistive heating or reverse cycle, as most demand defrost methods are usually complex, expensive or unreliable. Demand defrost can work by either predicting frost formation by processing measured conditions (fin surface temperature, air humidity and air velocity) and/or frost accumulation symptoms such as pressure drop and refrigerant properties. Other way of knowing when to defrost is to directly measure the frost formation using sensors such as photoelectric, capacitive or resistive. This review gathers some of the methods that can be used for directly measuring frost accumulation on the evaporator fin surface.info:eu-repo/semantics/publishedVersio

Further development and experimental testing of a resistive sensor for monitoring frost formation in refrigeration systems

This work has been supported by the project Centro-01-0145-FEDER-000017 - EMaDeS - Energy, Materials and Sustainable Development, co-financed by the Portugal 2020 Program (PT 2020), within the Regional Operational Program of the Center (CENTRO 2020) and the European Union through the European Regional Development Fund (ERDF). The authors wish to thank the opportunity and financial support that permitted to carry on this project.Refrigeration systems are widely accepted as a mean to prevent food degradation. These systems usually rely on fin-and-tube heat exchangers to lower the air temperature. Due to long operation times and surface temperatures below dew point, frost may form and accumulate on the evaporators fin surface. This frost accumulation reduces and may clog the airflow, decreasing the system efficiency. Usually, most systems use a time-controlled system (stopping the compressor with or without powering a heating resistor inserted among fins to heat) to melt the ice. This method does not measure or predict the amount of frost formed, thus it is not reliable. Ice sensors that are cheap, reliable and easy to implement in commercial systems are studied. A resistive sensor is purposed, that measures the voltage between two electrodes with the water phase change (condensation and solidification -freezing-), as these states have different resistive values. Different electrode materials, morphologies and configurations are studied in order to obtain the best design.info:eu-repo/semantics/publishedVersio

Current status and future trends of computational methods to predict frost formation

Nowadays, the increasing energy prices and associated environmental concerns lead the refrigeration systems’ developers and manufacturers to develop more energy efficient and sustainable equipment and devices. On the most demanding systems, intense usage results in the fast accumulation of ice on the evaporator fins that reduces the efficiency and may even clog the system. These systems often have time-controlled defrost cycles, that heat the evaporator, melting the ice and allowing the system to keep working normally after the defrost cycle. This cycle consumes extra energy and causes a thermal imbalance on the refrigerated space, that may result in a worst refrigeration quality. If it was possible to avoid the defrosting cycle passively (without energy consumption) its efficiency would greatly increase, and the refrigeration temperature would be more stable. Currently defrost cycles cannot be avoided in an economically viable way, although new designs, materials and configurations show promising results, and are currently being investigated. These studies require experimental tests that may become expensive as several geometries, topologies, materials and surface treatment combinations should be evaluated. To access the efficiency before these experimental tests, computational models that simulate frost formation could predict with some accuracy which of the most promising configurations should be then tested experimentally. The present paper aims to review the computational methods to predict frost formation and compare them for possible usage in the computational study of evaporators. Additionally, the future trends of the simulations are discussed, taking into account physical and mathematical models, numerical procedures and the accuracy of the dynamic pattern of the predictions.info:eu-repo/semantics/publishedVersio

Effects of resistance training on muscle strength of older women: a comparison between methods

O treinamento de força (TF) proporciona ganhos de força muscular (FM) em idosos. Entretanto, a magnitude pode variar consideravelmente conforme o método de avaliação utilizado. O estudo teve como objetivo comparar dois métodos de avaliação de força muscular após programa de TF em idosas. Participaram 61 idosas (idade média de 66,8 ± 5,8 anos), submetidas a um programa com duração de 24 semanas. Os exercícios contemplaram os principais grupos musculares. A FM dos extensores do joelho foi avaliada pelo teste da repetição máxima (1RM) e pelo dinamômetro isocinético (60º.s-1) antes e após o TF. Aplicou-se uma ANOVA 2X2 para comparar os métodos e a FM após o programa de TF. Observou-se que a FM aumentou significativamente após a intervenção, em ambos os métodos. Os incrementos na FM foram de 16,7% e 54,7% para o isocinético e 1RM respectivamente. Os incrementos avaliados pela 1RM foram significativamente (P<0,001) superiores aos mensurados pelo isocinético. Apesar dos valores estarem dentro dos limites de concordância, a diferença entre 1RM e Isocinético diminuiu conforme o aumento da FM pós-treinamento. Concluiu-se que, embora o TF promova aumento da FM em idosas, a magnitude desse ganho varia substancialmente em função do método utilizado. Ao que parece, o uso da 1RM pode superestimar os ganhos de FM e influenciar a interpretação funcional dos efeitos proporcionados pelo TF.Strength training (ST) increases muscle strength (MS) in the elderly, but results may vary considerably depending on the method of evaluation. Objective: This study compared two MS methods to evaluate an ST program for elderly women. METHODS: Sixty-one volunteers (mean age 66.8 ± 5.8 years) underwent ST for 24 weeks to work out the major muscle groups. Knee extensor MS was assessed using one-repetition maximum strength (1RM) and isokinetic dynamometry (60º.s-1) before and after ST. A 2x2 ANOVA was used to compare the methods and MS gains after the ST program. MS increased significantly after ST according to both methods. Increases in MS were in average 16.7% and 54.7% using dynamometry and 1RM. The improvement according to 1RM was significantly (P<0.001) greater than that measured using the isokinetic method. Although values lied within agreement limits, differences between methods (1RM vs. isokinetic) decreased as MS increased at the end of the ST program. ST increases MS in older women, but improvement varies considerably according to the method used to evaluate it. Measurements using 1RM seem to overestimate strength gains and may, thus, affect the potential results of resistance training

Identification of sarcopenic obesity in postmenopausal women : a cutoff proposal

Sarcopenic obesity is the combination of reduced fat-free mass (FFM) and increased fat mass (FM) with advancing age but there is lack of clear criteria for its identification. The purposes of the present investigation were: 1) to determine the prevalence of postmenopausal women with reduced FFM relative to their FM and height, and 2) to examine whether there are associations between the proposed classification and health-related variables. A total of 607 women were included in this cross-sectional study and were separated into two subsets: 258 older women with a mean age of 66.8 ± 5.6 years and 349 young women aged 18-40 years (mean age, 29.0 ± 7.5 years). All volunteers underwent body composition assessment by dual-energy X-ray absorptiometry. The FFM index relative to FM and height was calculated and the cutoff value corresponded to two standard deviations below the mean of the young reference group. To examine the clinical significance of the classification, all older participants underwent measurements of quadriceps strength and cardiorespiratory fitness. Values were compared between those who were classified as low FFM or not, using an independent samples t-test and correlations were examined. The cutoff corresponded to a residual of -3.4 and generated a sarcopenic obesity prevalence of 19.8% that was associated with reduced muscle strength and aerobic fitness among the older participants. Also, the index correlated significantly with the health-related fitness variables. The results demonstrated reduced functional capacity for those below the proposed cutoff and suggested applicability of the approach as a definition for sarcopenic obesity

<b>Effects of resistance training on muscle strength of older women: a comparison between methods.</b> DOI: http://dx.doi.org/10.5007/1980-0037.2012v14n4p409

DOI: http://dx.doi.org/10.5007/1980-0037.2012v14n4p409Strength training (ST) increases muscle strength (MS) in the elderly, but results may vary considerably depending on the method of evaluation. Objective: This study com­pared two MS methods to evaluate an ST program for elderly women. Methods: Sixty-one volunteers (mean age 66.8 ± 5.8 years) underwent ST for 24 weeks to work out the major muscle groups. Knee extensor MS was assessed using one-repetition maximum strength (1RM) and isokinetic dynamometry (60º.s-1) before and after ST. A 2x2 ANOVA was used to compare the methods and MS gains after the ST program. MS increased significantly after ST according to both methods. Increases in MS were in average 16.7% and 54.7% using dynamometry and 1RM. The improvement according to 1RM was significantly (P<0.001) greater than that measured using the isokinetic method. Although values lied within agre­ement limits, differences between methods (1RM vs. isokinetic) decreased as MS increased at the end of the ST program. ST increases MS in older women, but improvement varies considerably according to the method used to evaluate it. Measurements using 1RM seem to overestimate strength gains and may, thus, affect the potential results of resistance training

Efeitos do treinamento resistido sobre a força muscular de idosas: uma comparação entre métodos

O treinamento de força (TF) proporciona ganhos de força muscular (FM) em idosos. Entretanto, a magnitude pode variar consideravelmente conforme o método de avaliação utilizado. O estudo teve como objetivo comparar dois métodos de avaliação de força muscular após programa de TF em idosas. Participaram 61 idosas (idade média de 66,8 ± 5,8 anos), submetidas a um programa com duração de 24 semanas. Os exercí­cios contemplaram os principais grupos musculares. A FM dos extensores do joelho foi avaliada pelo teste da repetição máxima (1RM) e pelo dinamômetro isocinético (60º.s-1) antes e após o TF. Aplicou-se uma ANOVA 2X2 para comparar os métodos e a FM após o programa de TF. Observou-se que a FM aumentou significativamente após a intervenção, em ambos os métodos. Os incrementos na FM foram de 16,7% e 54,7% para o isocinético e 1RM respectivamente. Os incrementos avaliados pela 1RM foram significativamente (P<0,001) superiores aos mensurados pelo isocinético. Apesar dos valores estarem dentro dos limites de concordância, a diferença entre 1RM e Isocinético diminuiu conforme o aumento da FM pós-treinamento. Concluiu-se que, embora o TF promova aumento da FM em idosas, a magnitude desse ganho varia substancialmente em função do método utilizado. Ao que parece, o uso da 1RM pode superestimar os ganhos de FM e influenciar a interpretação funcional dos efeitos proporcionados pelo TF