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Riduzione dell'impatto ambientale dei motori agricoli grazie ad un cambio di alimentazione
No full textDefinition of the Layout for a New Facility to Test the Static and Dynamic Stability of Agricultural Vehicles Operating on Sloping Grounds
Full text linkIn this study, a new rig for investigating the static and dynamic stability of agricultural machines was conceived: its architecture was studied and its layout was designed following a specific conceptual approach. The first part of the proposed design process specifically addresses the test equipment and follows a ‘top-down’ logic starting from the requisites of the tests to perform. This approach alternates analysis and synthesis phases and exploits two important principles of the creative design process: functional analysis and decomposition, and kinematic inversion. During this process, many solutions (kinematic mechanisms, actuators) were proposed and discussed based on their advantages and disadvantages towards the definition of an optimal configuration. Therefore, the layout of a new mechanical system has been developed, which is supposed to steer subsequent and more detailed design-phases appropriately. The proposed facility has many innovative features compared to traditional test systems, in which vehicles are tested for lateral overturning under static conditions with the steering components (wheels/central joint for conventional/articulated vehicles) usually in a configuration corresponding only to a straight-path trajectory. Indeed, the present test rig is a mechanical installation with three degrees of freedom. It presents a wide plane, which can be tilted, composed by two semi-platforms connected by a central articulation hinge, operated by hydraulic jacks which allow the different angulations of the semi-platforms. It is specifically thought for performing dynamic stability tests of vehicles, especially on circular trajectories. An additional subsystem embedded in one of the two semi-platforms, configured as a rotating platform (‘turntable’), can test the global (static) stability of motionless vehicles placed on it
Stability tests of agricultural and operating machines by means of an installation composed by a rotating platform (“turntable”) with four weighting quadrants
Full text linkThe stability of agricultural machines, earth-moving machines, snow-compaction machines and, in general, of all vehicles that may operate on sloping terrains is a very important technical feature and should not be underestimated. In fact, it is correlated, above all, to the safety of the operators, but also to the preservation of the structural integrity of these vehicles, to the prosecution of the activities and to the preservation of the economic investment. Although these facts are well-known, the international legislation and technical standards do not yet have a sufficient level of detail to give an all-inclusive quantification of the stability of the vehicle under examination in all its working conditions, e.g., at different inclination angles of the support surface, at different climbing angles of the vehicle on the slope, with different tires and inflating pressures, and on different terrains. Actual standards limit the stability tests to the experimental measurement of the lateral rollover angle only. Furthermore, the realization of unconventional test equipment able to widen the usually-tested scenarios could not be simple, due to the necessary size that such equipment should have (to perform tests not in scale) and to the related difficulties of handling full-scale vehicles. This work illustrates the applications of a new rig for testing the stability of vehicles, able to address all the above-illustrated issues and of possible future adoption to certify the stability performance of machines and perform homologations. This installation, named “rotating platform” or “turntable”, has the peculiarity of being able to move the machine positioned on it according to two rotational degrees of freedom: (1) overall inclination of the support plane, (2) rotation of the support plane around an axis perpendicular to the plane. The same installation is also designed to record the weight supported by each wheel of the machine placed on it (by means of four sensorized quadrants), both when the platform is motionless and while the above-described movements of tilt and rotation are being carried out, thus locating precisely the spatial position of the vehicle center of gravity. The presented physical-mathematical models highlight the great potential of this facility, anticipate the outcomes of the recordings that the experimenters will have at disposal when the test rig will be effectively active, and help the future understanding of trends of data, thus maximizing the available information content
Proposal of a system to perform dynamic tests of stability on agricultural machines
No full textThe tests that are normally proposed to characterize the stability of agricultural machines suffer from evident limitations, first of all being limited to static conditions only, thus neglecting the presence of the centrifugal force or not considering at all the load transfers that can occur in real situations. The critical analysis of actual tests and test-facilities has been therefore the starting point for a conceptual-design process aimed at defining an innovative dynamic-stability test solution, named the tiltable and angleable plaftorm. This facility is wide enough to let vehicle travel on it and has two half-platforms that can assume different inclinations, hence resulting to be aligned or forming an angle. It will be installed within the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano. The different tests that can be performed with this facility will simulate better the real conditions that a vehicle in motion undergoes, thus helping the analysts to study new active safety devices
Concept of a safety system to be used when performing dynamic tests of stability on agricultural machines
No full textAn innovative test facility to be installed within the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano, located at the upcoming “NOI - Technology Park”, has been developed with the aim of performing new stability tests on agricultural machines. It is basically a large tiltable platform (about 15×15 m), and it is composed by two test systems integrated together, (1) the tiltable and angleable plane and (2) the tiltable turntable. During the tests at this facility, machines are given some specific motions (rotation around a vertical axis, translation on circular trajectories). The considerable masses (up to 5000 kg) of the tested machines have raised the need to equip the facility with a safety system able to retain the vehicles when they reach the overturning. Studying the possible motions and trajectories of tested vehicles, a system that can provide up to 6 selectively-lockable degrees of freedom has been proposed. It can be named to as: system with rotating-translating pincer-cage and carousel-like arm
Proposal of an advanced facility for testing the static stability of agricultural machinery
No full textA critical analysis of actual tests and test-facilities used for inquiring the static stability of agricultural machines has been the starting point for a conceptual-design process: it has allowed defining an innovative test solution named the tilting turntable. This test device is composed by a circular support, installed on a tiltable structure and capable to rotate around a vertical axis by 360° with a vehicle positioned on it. Some sensors allow: (1) localizing the vehicle’s centre of gravity, (2) measuring the load distribution/transfer at different positions of the vehicle’s longitudinal axis with respect to the maximum slope direction and, even, (3) quantifying the trim change and downstream-tire(s) flattening. The tilting turntable is part of the test facility that will be installed within the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano, located at the upcoming “NOI - Technology Park”
La Meccanica Agraria oggi: Un confronto aperto su concetti, idee e aspettative di una disciplina in continua evoluzione
No full textIncreasing the safety of agricultural machinery operating on sloping grounds by performing static and dynamic tests of stability on a new-concept facility
No full textUsing agricultural machines on slopes is very risky for operators: drivers difficultly have a correct perception of the stability condition of their vehicles when travelling, especially because it is impossible to instantly check the ground elevation and harshness in correspondence of each wheel. Moreover, the tests that are usually performed to characterize these machines’ stability are scarcely helpful in real conditions: these tests check the lateral overturning (maximum angle) in two static configurations only. Evidently, these do not cover most of real situations, do not locate its centre-of-mass and do not consider the centrifugal force (causing load-transfers and dynamically-variable readjustments of the machine’s trim in turnings), thus making impossible the setup of eventual active/passive safety-systems to be installed on vehicles.
Therefore, with the aim of overcoming the limitations of actual tests, giving a higher level of information to the tractors’ manufacturers and users, we have conceived a completely-new test-apparatus to be installed within our laboratory: the Tiltable Platform. It integrates two subsystems, illustrated hereinafter.
(1) The tiltable/angleable plane is a wide flat structure (15×15 m), able to simulate different ground- gradients, allowing a vehicle to manoeuvre/travel on it along circular paths in a controlled and safe environment. It can also generate an angle at half of its width, transversal to the maximum-slope direction (simulating the exits of an agricultural machine from the inter-rows).
(2) The tilting turntable: has a circular shape and is divided into quadrants, each capable of measuring the weight sustained due to a motionless vehicle positioned on them; it is installed on a tilting structure and can rotate around a vertical axis, thus allowing to vary the angular position of the vehicle’s longitudinal axis with reference to the maximum-slope direction.
Finally, this test-rig will be useful to develop new test-methodologies to certify the agricultural machines’ stability in real operating-conditions (e.g. operating with ballast/mounted-implements)
Proposal of an advanced facility to perform static and dynamic tests of stability on agricultural machines
No full textThe tests that are normally proposed to characterize the stability of an agricultural machine are substantially of two types: (1) static tests of lateral overturning of a vehicle in a straight-ahead configuration, (2) static tests of lateral overturning of a vehicle in a specific steering configuration. These tests have as output the maximum angle of lateral overturning of a vehicle, measured when all the vehicle’s tanks are completely filled with their operating liquids and some weights are placed on the seat, to simulate the presence of the driver. There is also a third category of tests, less used, carried out via a system oscillating like a pendulum; the output of this test is the distance of the tractor’s centre-of-gravity (COG) from the oscillation point, and, thus, the vertical position of the COG. All these tests suffer from evident limitations, hereinafter briefly explained, and stimulate us to conceive a completely-new test apparatus that can overcome these shortcomings. Limiting the attention to the conditions of static stability only, the above-presented tests do not allow providing the complete spatial position (in Cartesian coordinates) of the COG in relation to the vehicle’s supporting base and, therefore, they prevent the prediction of the stability conditions of that vehicle when it travels on variously-inclined slopes and at angles with the maximum-slope direction different from the test conditions. Hence we design a first new-concept device, the tilting turntable, having the following characteristics: (1) the turntable has a circular shape and it is divided into quadrants capable of measuring the weight sustained by each of them due to the motionless vehicle positioned on them; (2) the turntable is installed on a tilting structure, and therefore it is able to simulate different gradients of the ground on which the vehicle is placed; (3) the turntable can rotate around an axis perpendicular to the surface supporting the vehicle, thus allowing to vary the angular position of the vehicle’s longitudinal axis with respect to the maximum-slope direction of the tiltable structure. This equipment will allow precisely locating the COG of a vehicle and making many experimental (static) tests simulating a lot of working conditions of agricultural machines on slopes. Moreover, common stability tests do not take in any way into account the load-transfer phenomena related to the velocity factor, concerning not only the appearance of a centrifugal force applied on the COG, but also a readjustment of the machine’s trim due to all the components having a certain elasticity (tires, suspensions where present, supports of the cabin) or having a degree of freedom in the plane transversal to the machine’s longitudinal axis (suspended loads, liquids, inconsistent solids such as grain products, stacked solids such as pseudo-spherical fruits). The behaviour of a mobile system of this type, having a dynamically-variable trim, could be difficult to predict a priori by only knowing the position of the COG inquired under static conditions. For these reasons, we propose a second system that allows to investigate experimentally also these dynamic aspects by reproducing any real-scale manoeuvres in a controlled and safe environment. The proposed system is a tiltable plane with dimensions (about 15 x 15 m) allowing an agricultural vehicle to travel on it along complete circular paths.
By integrating the tilting turntable and the tiltable plane, a new innovative test rig has been created: the tiltable platform. It will be installed within the “Agroforestry Innovation Laboratory” of the Free University of Bozen-Bolzano, located at the upcoming “NOI - Technology Park”
Morphometry as a Key to Investigate the Stability to a Wind-Induced Rollover of Agricultural Equipment for Irrigation
No full textA problem that is common in agriculture but not very publicized, thanks to the absence of victims, is the rollover of Centre Pivot and Lateral Move irrigation systems. These accidents are due to particularly-strong winds acting on the spans, and they are potentially very destructive for the installations. Also, the restoration phase of the installations requires always an intervention of lifting of the machinery on the field, with a potential further damage to crops (setting) and land (compaction). Given the basic inevitability of the phenomenon, due to atmospheric events, these rollovers could be however limited e.g. by proposing a system design granting a higher stability. Therefore, we have firstly modelled the rollover dynamics of these systems, considering the geometry, the masses, the forces acting on them (wind, gravity), the position of the centre of gravity. Then, thanks to morphometry, we have investigated booms’ stability as a consequence of a proportional or not-proportional alteration of the system sizes, in particular: the upscaling of supports, done by some manufacturers, and the lengthening of spans, often required by customers. Morphometry is a method born in biology, typically used to describe and analyse statistically the shape variations within and among samples of organisms as a result of growth, experimental treatments or evolution. As the idea of evolutionary adaptation is intrinsic in the technical evolution of human-made systems (models, variants) operated by manufacturers, also artificial systems can be studied or improved via the morphometry, as operated here. The output of this study is a physical model of rollover and a sensitivity analysis of a reference configuration for an irrigation boom. Thanks to these analyses, we were able to demonstrate, for example, how a scaling-up of boom supports, respectful of geometric ratios, can increase the system stability despite the elevation of the pressure point of the wind on the frame
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