The aim of this thesis is the comparison of different farm tractors cab suspension systems and the description of the techniques to evaluate their ride comfort. Most of the farm tractors have a cab suspension system and a suspended seat to increase the driver's comfort. Starting from an analysis of the cab suspension systems on the market, it is possible to analyze the pros and cons of every configuration. The different analytical models of the suspended seat are described. A multibody model of the tractor is implemented in SimMechanics, by means of a block diagram. This model can describe the global dynamics of a farm tractor and the vibration filtering efficiency of its subsystems. This model can be modified to evaluate the dynamics of different farm tractors; furthermore this model can be simplified in order to decrease the computational time. An experimental benchmark test is conducted to evaluate different cab suspension systems while considering different manoeuvres. Five tractors are instrumented to evaluate their dynamics. The objective comfort is evaluated applying the multibody theory during the signal processing; the subjective comfort is evaluated by statistically analysing the questionnaires filled by ten different drivers. A correlation analysis is conducted between objective and subjective evaluations. The results are synthesised. Finally six comfortable cab suspension systems are proposed and they are implemented in SimMechanics. Even if the subject of ride comfort and of cab suspension systems is extensively analysed in the scientific literature, this thesis describes a methodology to evaluate comfort with both subjective and objective approaches, and their correlation.
La presente tesi si prefigge l'obiettivo di confrontare i diversi sistemi di sospensione cabina di un trattore agricolo e descrivere i metodi per valutarne il comfort vibrazionale. Infatti la maggior parte dei trattori agricoli ha un sistema di sospensione cabina e un sedile ammortizzato per aumentare il comfort del guidatore. Partendo dall'analisi dei sistemi di sospensione cabina presenti sul mercato, è possibile analizzare vantaggi e svantaggi delle diverse configurazioni. Vengono inoltre descritti i vari modelli analitici di sedile ammortizzato presenti in letteratura. Un modello multibody del trattore è stato implementato in SimMechanics, con modellazione a blocchi. Questo modello serve a valutare il comportamento dinamico del trattore completo e il livello di filtraggio delle vibrazioni dei suoi sottosistemi. Il modello può essere modificato per valutare la dinamica di diversi tipi di trattore agricolo e può inoltre essere semplificato per ridurre il tempo di calcolo. E' stata condotta una campagna sperimentale per valutare diversi sistemi di sospensione cabina in diverse condizioni di utilizzo. Cinque diversi trattori sono stati strumentati per valutarne il comportamento dinamico e gli stessi sono valutati soggettivamente da dieci diversi operatori. Il comfort oggettivo è stato valutato applicando la teoria multibody per l'analisi dei segnali disponibili; il comfort soggettivo è valutato analizzando i questionari compilati dai diversi operatori. La correlazione tra questi due tipi di risultati è valutata in modo sintetico. Infine sei diversi prototipi di sistemi di sospensione cabina sono proposti e implementati in SimMechanics. Sebbene il tema del comfort vibrazionale e dei sistemi di sospensione cabina sia abbondantemente trattato in letteratura, questa tesi sviluppa una metodologia per valutare il comfort con approccio oggettivo e soggettivo effettuando una completa analisi di correlazione.
Comparative analysis of farm tractor cab suspension systems. Numerical and experimental ride comfort evaluation
SCHERINI, MARCO
2011/2012
Abstract
The aim of this thesis is the comparison of different farm tractors cab suspension systems and the description of the techniques to evaluate their ride comfort. Most of the farm tractors have a cab suspension system and a suspended seat to increase the driver's comfort. Starting from an analysis of the cab suspension systems on the market, it is possible to analyze the pros and cons of every configuration. The different analytical models of the suspended seat are described. A multibody model of the tractor is implemented in SimMechanics, by means of a block diagram. This model can describe the global dynamics of a farm tractor and the vibration filtering efficiency of its subsystems. This model can be modified to evaluate the dynamics of different farm tractors; furthermore this model can be simplified in order to decrease the computational time. An experimental benchmark test is conducted to evaluate different cab suspension systems while considering different manoeuvres. Five tractors are instrumented to evaluate their dynamics. The objective comfort is evaluated applying the multibody theory during the signal processing; the subjective comfort is evaluated by statistically analysing the questionnaires filled by ten different drivers. A correlation analysis is conducted between objective and subjective evaluations. The results are synthesised. Finally six comfortable cab suspension systems are proposed and they are implemented in SimMechanics. Even if the subject of ride comfort and of cab suspension systems is extensively analysed in the scientific literature, this thesis describes a methodology to evaluate comfort with both subjective and objective approaches, and their correlation.| File | Dimensione | Formato | |
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2012_12_Scherini.pdf
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Descrizione: Testo della tesi
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https://hdl.handle.net/10589/71902