Morphometry as a Key to Investigate the Stability to a Wind-Induced Rollover of Agricultural Equipment for Irrigation

Abstract

A 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.

A Novel Facility For Statically Testing The Stability Of Vehicles: Technical Features And Possibilities

“…Since these reference situations were previously inquired on the test installation and the weight supported by each quadrant (hence: by each vehicle wheel) was accurately measured, e. an incipient overturning condition; see also [33]).…”

“…12). The stability condition can be quantified by using a proper metric, such as the Roll Stability Index (RSI), spanning from 0 to 1 (or from 0% to 100%): when the RSI reaches zero, the vehicle is in a situation of incipient overturning [11], [37], meaning that the direction of the resultant of the active forces applied to the CoG intersects the support polygon close to (or on) the edge of the support polygon ('stability condition of a spatial structure or of a vehicle on a ground' [33]). The quantities of interest to be reported on the axes of the stability maps can be related to the environmental conditions (slope angle α, turning radius R) or, only if dealing specifically with a farm tractor, to the features and conditions of operation/ connection for an implement (implement mass M, height of the implement CoG above the supporting plane H, distance between the implement CoG from the rear axle L).…”

“…Figure 10: Lateral inclination in an ideal (a) and real (b) situation; in (b) the tyre flattening phenomenon, occurring mostly at the downstream tyres, increases the lateral inclination of the vehicle chassis (d 1 <d 2 → α'>α, where α' is, in this case, the vehicle roll angle φ), thus making the CoG projection reach the edge of the support polygon (i.e. an incipient overturning condition; see also[33]). …”