Lateral stability analysis of the tractor/full trailer combination vehicle
This paper presents a linear dynamics model of tractor/full trailer with six degrees of freedom, and a series of simulations are performed on obstacle avoidance manoeuvers in which the combination vehicle moves at a constant forward speed. It is found that the ratio of the peak lateral acceleration of the full trailer's center of gravity (CG) to that of the tractor is 2.3, meanwhile, the articulated angle of the trailer is larger than that of the dolly. This phenomena, defined as the ‘rearward amplification ratio’(RWA), leads vehicle to rollover easily. A larger wheelbase of trailer would be useful to improve the lateral stability of the combination vehicle but it is limited by width of the road. Acting a resistive torque on the turntable can be absolutely effective in improving the dynamics stability of the tractor/full trailer combination vehicle but if acted at hitch point it has little improvement.
Simulated stability tests of a small articulated tractor designed for extreme-sloped vineyards
A new reversible wheeled articulated tractor, designed to work in terraced vineyards trained with “pergola” system, common in mountain areas, is here described in its latest version and analysed through numerical simulations. This tractor has small dimensions, necessary to operate in that environment, and its central articulation has two rotational degrees-offreedom. The described features are surely strong design points but could be critical for vehicle’s stability, as affecting the supporting base’s dimensions and shape. Therefore, the tractor was equipped with a new automatic safety system: a self-locking articulation activated by contact sensors on the wheels. This device makes the vehicle partially-rigid in case of lateral unbalancing, so that rollover can happen only by overcoming the whole vehicle mass. A mathematical description of vehicle-ground interactions was implemented to deeply inquiry the tractor behaviour in different configurations (straight, angled) at increasing values of ground slope; roll and pitch stability indexes were then computed and used for comparisons with conventional tractors. Thanks to the low centre-of-gravity, the resulting rollover angle with the vehicle in straight configuration is promising (43.8°→96%): it is greater than the maximum lateral (20°→36%) and frontal (38°→78%) slope angle ever recorded on terraced vineyards. The same rollover angle is lower when the tractor turns.
Treatment of oily wastewater by organic–inorganic composite tubular ultrafiltration (UF) membranes
A tubular UF module equipped with polyvinylidene fluoride membranes modified by inorganic nano-sized alumina particles was used to purify oily wastewater from an oil field. The membrane water permeations of the UF process were analyzed. Retentions of chemical oxygen demand and total organic carbon were more than 90% and 98%, respectively. The results indicate that after UF treatment, oil content was below 1 mg/L, suspended solids content was below 1 mg/L, and solid particle median diameters were less than 2 μm. The quality of the permeation water met the requirement by oilfield injection or drainage. Fouled membranes and washed membranes were analyzed by scanning electron microscopy, and fouled membranes were backwashed with different solutions. Results show that the addition of nanosized alumina particles improved membrane antifouling performance, and the flux recovery ratio of modified membranes reached 100% washing with 1 wt% of OP-10 surfactant solution (pH 10).