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An ergonomic approach for front foldable ROPS fitted on agricultural tractors
No full textTractor rollover is one of the main causes of fatal accidents in agriculture. Driver’s injuries increase considerably if the Roll-Over Protective Structure (ROPS), designed to provide a clearance zone for the driver in the event of tractor rollover, is not correctly fitted on the tractor and used properly during normal field operations. Front-mounted folding ROPSs are widely used on narrow-track tractors because a front foldable ROPS makes the tractor more versatile than a cabin tractor for orchard and vineyard use, allowing it to better adapt to a reduced clearance area in the crop inter-rows. Front ROPS was conceived to be used in the upright position for driver protection in the case of unstable tractor conditions; nonetheless, to use the tractor in narrow spaces the driver is allowed to lower the ROPS only when strictly necessary and in safe conditions with respect to a rollover risk. Folding down the ROPS could be essential for operating in specific conditions such as greenhouses or specially trained vineyards. Lowering and raising the ROPS is a manual operation normally performed by the driver with effects on the working capacity of the tractor since additional time is needed for this. The manual handling of the foldable ROPS, often difficult due to its heavy mass, is considered a potential cause of incorrect ROPS use, being left in the lowered position during normal operations and consequently with a lack of protection for the driver in the event of rollover. A feasible approach to encourage the correct use of the foldable ROPS is to assist the driver in handling the ROPS, allowing quick folding and raising actions, with efforts suitable for a medium-sized person. A test panel, mainly composed of skilled drivers, was selected to perform an evaluation on five tractors fitted with front foldable ROPS to analyse the ROPS handling with the aim of obtaining feedback allowing the design of foldable ROPSs to be improved in terms of easier, quicker and safer handling
Effects of rubber tracks on narrow-track tractors on the non-continuous rolling prediction model
No full textTractor rollover is one of the most hazardous events for the driver. The rollover protective structure (ROPS) was introduced to passively protect the driver. In the specific case of two-post protective structures fitted in front of the driver on narrow-track wheeled agricultural tractors, the ROPS has to avoid non-continuous rolling in the event of a lateral rollover. In order to check non-continuous rolling behavior in narrow-track wheeled agricultural tractors, a mathematical model is included in the preliminary ROPS tests of the standardized testing procedures issued by the Organization for Economic Cooperation and Development (OECD). A recent approach in the design of narrow-track tractors is the fitting of rubber tracks. A safety issue consequent to this new arrangement is that the standardized calculation does not cover narrow rubber-tracked tractors because it was originally developed assuming only the behavior of the tire in a lateral rollover. The aim of this study was to extend the field of application of the standardized calculation for non-continuous rolling behavior, allowing rubber-tracked tractors to be fitted with a front ROPS suitable for operation in narrow orchards and vineyards. The effect of track-ground interaction compared to tire-ground interaction was evaluated. The track shape and nondeformed behavior of the rubber track at a state of unstable equilibrium under full load caused the tractor to rotate around the outer edge of the track; therefore, the tipping axes and wheel characteristics in the original mathematical model were revised. The tracked tractor checked with the revised model required a higher ROPS with respect to the equivalent wheeled tractor to obtain non-rolling behavior. The ROPS needed to be increased by 0.28 m to meet the safety requirement
Tractor stability parameters as affected by ROPS type
No full textTractor overturns are a major cause of death in agriculture. Many variables are involved. To minimise the risks of driver injuries in an overturn a Roll-Over Protective Structure (ROPS) has been invented. Narrow track tractors for orchard and vineyard operations are mainly available with two different ROPS types: an enclosed cab frequently fitted with filters and air conditioning system or a simple front two post ROPS designed to be folded down allowing the tractor to operate in a reduced space. Concerning stability, the tractor unstable equilibrium angles are the result of the tractor configuration and position with respect to the ground slope. The aim of the paper was to study the effect of ROPS type on tractor stability performance. The tractor stability parameters were evaluated on 18 modern narrow track tractors measuring the mass, track width, wheelbase, Centre of Gravity (CoG) and Moments of Inertia (MoI). The evaluation considered pairs of tractors equipped with cab ROPS and two post ROPS. The cab fitment keeps the wheelbase and track width of the tractor unchanged with respect to the front foldable ROPS but affects the mass, position of the CoG and longitudinal and transversal MoI. Data show an increase of tractor mass and higher CoG and MoI for the cab fitment with respect to the two post ROPS. The recent debate on the safety performance of two post ROPS is consequent to the incorrect use of the foldable ROPS and the cab is often claimed to provide better driver protection. The investigation conducted denotes that on sloping fields narrow-track tractors fitted with a cab ROPS reach the unstable state at lower angle than two post ROPS tractors
Virtual test as a complement tool of the actual ROPS testing on agricultural tractors
Get PDFThe Roll Over Protective Structure (ROPS) is a key safety feature in agricultural and forestry tractors in order to minimize risks to the driver in case of rollover during normal use. The Organization for Economic Co-operation and Development (OECD) in an effort to improve operator's safety in Agricultural and Forestry Tractors has set up harmonized testing procedures for ROPS systems. The current OECD Codes for tractors relate to several features of performance.
OECD Code 7 is related to the strength of ROPS fitted on narrow-track tractors. On the one hand, Code 7 foresees a sequence of loadings that the protection system has to withstand until the prescribed energy or force is satisfied. In addition to successfully resist the loading sequence, the ROPS has to guarantee a clearance zone during the complete loading sequence. Nowadays tractor manufacturers often adopt numerical simulations for ROPS designing so as to foresee in advance the strength behaviour of the protective structure with respect to the standardized ROPS tests requirements. As a matter of fact, ROPS simulations turned out to be very useful to understand the behaviour of the protection system subjected to complex loading and get valuable insights into performance. A new approach in ROPS test standardization is evaluating the potentiality of virtual tests as a complement of the official actual tests in defined ROPS testing conditions. A numerical simulation with LS-DYNA® were carried out to virtually assess the performance of a ROPS system designed by the BCS manufacturer for a narrow-track tractor. Then the ROPS was officially tested according to the OECD Code 7 loading sequence. A comparison between the results of virtual and actual tests was performed. The main goal of the simulations was to virtually test the tractor according to the Code 7 prior to official test approval and, if necessary, introduce structural changes in order to successfully pass the ROPS strength tests. The use of numerical simulation accompanied by a robust methodology could ensure a high reliability of the virtual prediction with respect to the normalized tests
An evaluation of operator perception in manual handling of front foldable rollover protective structures mounted in narrow-track tractors
Get PDFDespite the progressive reduction of agriculture fatalities, accidents data is still alarming with 160 deaths per year in Italy, more than 60% of which involving tractor rollover with the crushing of the driver for lack of protective devices. The folding version of front rollbar (Foldable Rollover Protective Structures, FROPSs) has been designed to allow tractors to operate in low overhead clearance conditions. However, due to the discomfort in FROPS handling, the farmers often leave them in the folded-down position. Concerning this unsafe behavior and considering the growing female role in agriculture activities, the present study aimed to evaluate the perceived difficulty by users in handling the FROPS considering: i, gender of the user; ii, front ROPS mass; iii, expertise level in using the tractor (expert, casual or novice user).Five narrow tractors were evaluated. The tractors were all fitted with front foldable ROPS with a mass ranging from 17 to 55 kg.A test panel was selected to perform an evaluation on the handling of foldable ROPS. The test panel was composed of 31 operators, 20 men and 11 women. A survey was submitted to the test panel and the results were analyzed with Kruskal-Wallis Test to evaluate if the safety performance of the foldable ROPS were affected by the operator behavior and perception.The results denoted a different perception in the front ROPS handling between male and female operators. In detail, expert male operators were mainly able to perform the front ROPS handling but the ROPS mass affected the operation. For the female group, in the manual handling a non-ergonomic design approach was clear
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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