1,721,071 research outputs found
Corrigendum to: Modelling and handling dynamics of a wind-driven vehicle (Vehicle System Dynamics, (2019), 57, 5, (697-720), 10.1080/00423114.2018.1479529)
No full textWhen the above article was first published online, Figure 3 and Figure 4 were erroneously interchanged. This has now been corrected online. The authors apologise for this error
On the Mobility of All-Terrain Rovers
No full textIn this paper, a robot with advanced mobility features is presented and its locomotion performance is evaluated, following an analytical approach via extensive simulations. The vehicle features an independently controlled 4-wheel-drive/4-wheel-steer architecture and it also employs a passive rocker-type suspension system that improves the ability to traverse uneven terrain. An overview of modeling techniques for rover-like vehicles is introduced. First, a method for formulating a kinematic model of an articulated vehicle is presented. Next, a method for expressing a quasi-static model of forces acting on the robot is described. A modified rocker-type suspension is also proposed that enables wheel camber change, allowing each wheel to keep an upright posture as the suspension conforms to ground unevenness
Locomotion Performance Evaluation of an All-Terrain Rover
No full textIn the last few years, mobile robots are increasingly being used in natural outdoor terrain for applications such as forestry, mining, rescuing, precision farming, and planetary exploration. Future tasks will require robotic vehicles to travel over longer distances through challenging terrain, with limited human supervision. To accomplish this objective, a higher degree of mobility will be primarily required, ensuring, at the same time, the safety of the vehicle. In this paper, a robot with advanced mobility features is presented and its locomotion performance is evaluated, following an analytical approach. The proposed vehicle features an independently controlled 4-wheel-drive/4-wheel-steer architecture that allows the robot to perform maneuvers such as turn-on-the-spot and crab motion. It also employs a passive rocker-type suspension system, improving the ability to traverse uneven terrain, while ensuring good traction performance. An overview of modeling techniques for rover-like vehicles is introduced. First, a method for formulating a classical kinematic model of an articulated vehicle is presented. Next, a method for expressing a quasi-static model of forces acting on the robot is described. Note that quasi-static models are appropriate due to the relative low speed and acceleration of those vehicles. Two optimization methods are also proposed to control the rover's motion, minimizing slip and power consumption, respectively. These models are used to reproduce the behavior of the robot in typical obstacle-climbing scenarios, pointing to the advantages compared with conventional architectures
Agricultural Robot for Radicchio Harvesting
No full textIn the last few years, robotics has been increasingly adopted in agriculture to improve productivity and efficiency. This paper presents recent and current work at the Politecnico of Bari in collaboration with the University of Lecce in the field of agriculture robotics. A cost effective robotic arm is introduced for the harvesting of radicchio, which employs visual localization of the plants in the field. The proposed harvester is composed of a double four bar linkage manipulator and a special gripper, which fulfills the requirement for a plant cut approximately 10 mm underground. Both manipulator and end-effector are pneumatically actuated and the gripper works with flexible pneumatic muscles. The system employs computer vision to localize the plants in the field based on intelligent color filtering and morphological operations; we call this algorithm the Radicchio Visual Localization (RVL). Details are provided for the functional and executive design of the robotic arm and its control system. Experimental results are discussed, obtained with a prototype operating in a laboratory testbed showing the feasibility of the system in localizing and harvesting radicchio plants. The performance of the RVL is analyzed in terms of accuracy, robustness to noises and variations in lighting, and is also validated in field experiments
An Adaptive Suspension System For Planetary Rovers
No full textThis paper presents an innovative suspension system with variable wheel camber to improve mobility of robots on rough-terrain. The system is optimized for planetary rovers that employ conventional rocker-type suspensions. The main advantage of the proposed system is that each wheel keeps an upright posture as the suspension system adapts to terrain unevenness, maximizing tractive and climbing performance, and reducing energy consumption. The synthesis of the variable camber mechanism is described along with details of the mechanical design, showing the feasibility of this solution
On wind-driven land vehicles
No full textThis paper deals with the study of a land-yacht, that is a ground vehicle propelled by wind energy. There is a large interest in exploring alternative source of energy for propulsion and wind energy could be a feasible solution being totally green, available and free. The idea envisaged by a land-yacht is that of using one or several flexible or rigid vertical wing-sails to produce a thrust-force, which can eventually generate a higher travel velocity than its prevailing wind. A model of a three-wheel land-yacht is presented capturing the main dynamic and aerodynamic aspects of the system behaviour. Simulations are included showing how environment conditions, i.e. wind intensity and direction, influence the vehicle response and performance. In view of a robotic embodiment of the vehicle, a controller of the sail trim angle and front wheel steer angle is also discussed for autonomous navigation
On wind-driven land vehicles
No full textThis paper deals with the study of a land-yacht, that is a ground vehicle propelled by wind energy. There is a large interest in exploring alternative source of energy for propulsion and wind energy could be a feasible solution being totally green, available and free. The idea envisaged by a land-yacht is that of using one or several flexible or rigid vertical wing-sails to produce a thrust-force, which can eventually generate a higher travel velocity than its prevailing wind. A model of a three-wheel land-yacht is presented capturing the main dynamic and aerodynamic aspects of the system behaviour. Simulations are included showing how environment conditions, i.e. wind intensity and direction, influence the vehicle response and performance. In view of a robotic embodiment of the vehicle, a controller of the sail trim angle and front wheel steer angle is also discussed for autonomous navigation
Non-Performing Loans and Macroeconomics Factors: The Italian Case
Full text linkThe purpose of this work is to investigate the influence of macroeconomics determinants on non-performing loans (NPLs) in the Italian banking system over the period 2008Q3–2020Q4. We mainly contribute to the literature by being the first empirical article to study this relationship in the Italian context in the recent period, thus providing fresh evidence on the macroeconomic impact on NPLs, i.e., on the credit risk of Italian banks. By employing the Autoregressive Distributed Lag (ARDL) cointegration model, we are able to investigate the short and long-run effects of macroeconomic factors on NPLs. The empirical findings show that gross domestic product and public debt have a negative impact on NPLs. On the other hand, we find that the unemployment rate and domestic credit positively influence impaired loans. Finally, we find evidence of the “gamble for resurrection” approach, i.e., Italian banks tend to support “zombie firms”
A Test Bed for the Experimental Study of a Cylindrical Shaped Robot on rough-Terrain
No full textA testbed for the characterization of the dynamic behavior of a cylindrical robot in motion on deformable soil is described. The mobile robot consists of a cylindrical rigid shell which can roll on rough terrain thanks to an internal device. The test-bench was designed and optimized to experimentally test the interaction between the external shell and the soil with different mechanical characteristics. A LabView based software to lead and acquire the necessary data for the experiments was developed. Pc-based boards with general purposes A/D I/O ports were used for the rotative and linear encoders and the internal device d.c. motor. The goal is to build a big sensor to estimate the forces system arising from the interaction between a rigid cylindrical shell and rough terrain. Experimental results show the testbed can give a good measure of the travelling resistance that the mini-vehicle meets on rough terrain
Analisi multitemporale dell’uso del suolo della dorsale appenninica marchigiana nel XIX e XX secolo
Full text linkQuesto studio ha permesso di ricostruire, per la prima volta nell’Appennino Umbro-Marchigiano, l’evoluzione temporale dell’uso del suolo lungo un arco di tempo di 150 anni e su una superficie di vasta estensione (circa 8000 ettari). Il dato principale che emerge è la sostanziale discontinuità ecologica di tutti gli ecosistemi naturali e seminaturali, fatte salve alcune importanti patches pascolive e, in misura molto minore, boschive. In totale neanche il 20% del territorio dell’area considerata è rimasto stabile nel corso degli ultimi 150 anni; queste
aree rappresentano, dal punto di vista floristico, dei potenziali siti di rifugio per le specie erbacee di prateria e per quelle sciafile di bosco. Si tratta quindi di siti estremamente importanti per la conservazione della biodiversità e serbatoi genetici da cui può ripartire la colonizzazione degli ambienti antropizzati e non più utilizzati come le aree agricole abbandonate. È interessante annotare, ad esempio, come proprio in corrispondenza della
più ampia patch forestale stabile (Monte Fiegni) sia presente una delle più importanti stazioni dell’Appennino Umbro-Marchigiano di tasso (Taxus baccata) ed agrifoglio (Ilex aquifolium), all’interno di
una faggeta basso-montana. Si evidenzia, inoltre, una tendenza
alla semplificazione del mosaico ambientale di queste aree montane. Tale semplificazione risulta bene evidente per gli ecosistemi di prateria (stabili e neoformati) che tendono a conservarsi prioritariamente all’interno delle classi di pendenza minore. Questo fenomeno riassume
in se il senso dei mutati input che l’economia contemporanea offre alle attività zootecniche; nel corso dei secoli, infatti, si è passati da forme di economia basate sulla transumanza ovina ad un’attività zootecnica di tipo stanziale e dedita soprattutto all’allevamento bovino. Questa
differente tipologia zootecnica richiede habitat diversi e, in particolare per quanto concerne i bovini, sono assolutamente
indispensabili praterie di elevata produttività e moderata stasi estiva, condizioni che nell’Appennino si verificano solo in corrispondenza delle aree caratterizzate da morfologie a bassa energia di rilievo e in cui si sono anche conservati suoli profondi. Permanendo queste tendenze socio-economiche, dunque, in futuro tenderanno sostanzialmente a scomparire gli ecosistemi di prateria aperta sostituiti da boschi. Questo, se da un lato rappresenta un aspetto che va nel senso della naturale dinamica degli ecosistemi, dall’altro potrebbe comportare dei problemi per la conservazione della biodiversità floristica e faunistica
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