Agricultural vehicles are mostly driven on roads or off-roads characterized by important roughness. As consequence, drivers are subjected to harsh working conditions, due to high vibrations for a long period of time. Therefore, the improvement of driving comfort, in the last decades, has been object of the research studies. This thesis is the result of a collaboration between Politecnico di Milano and Argo Tractors, a well-known manufacturer of leading agricultural machinery, and aims at the development of control strategies for a four-point suspended tractor cab equipped with hydro-pneumatic actuators. In particular, this problem, to which this work is addressed, can be divided in two parts: the first one deals with the semi-active control of the suspension system. At first the optimal damping level is retrieved through the suspensions’ passive characterization. This passive configuration does not prevent the end-stop impact in the case of important road disturbances, indeed an end-stop avoidance logic is proposed and implemented on the prototype, through a static map of the damping current. The second part concerns the load levelling problem. A dynamic physical model of the suspension and the cab is developed and identified through the S.E.M (Simulation Error Method) identification algorithm. Due to the significant uncertainty of the static model an heuristic load levelling controller is proposed. It is based on cyclic acquirements of the suspensions’ stroke signals and when the latter are under or above a certain threshold the controller is activated. Experimental results validate the overall approaches both for semi-active and load levelling control.
I veicoli agricoli sono per la maggiore guidati su terreni accidentati. Di conseguenza, a causa delle vibrazioni indotte, i guidatori sono soggetti a condizioni di lavoro severe per lunghi periodi di tempo. Per questi motivi il miglioramento del comfort di guida, negli ultimi decenni, è diventato oggetto di studi di ricerca. Questa tesi è il risultato della collaborazione tra Politecnico di Milano e Argo Tractors, un nota azienda leader nella costruzione di macchine agricole, e ha come scopo quello di implementare strategie di controllo per una cabina sospesa su quattro punti. Nello specifico, tale problema si suddivide in due parti: la prima riguarda il controllo semi-attivo delle sospensioni. Dapprima, è stato ricavato il valore di smorzamento ottimo tramite la caratterizzazione passiva delle sospensioni. Tale configurazione non previene l’impatto con i fine-corsa delle sospensioni in presenza di disturbi stradali particolarmente cattivi, perciò una logica di end-stop avoidance è proposta e implementata sul prototipo, tramite una mappa statica della corrente di smorzamento. La seconda parte riguarda il problema del load levelling. Un modello dinamico e fisico, delle sospensioni e della cabina, è stato sviluppato e identificato tramite l’algoritmo S.E.M (Simulation Error Method). Per causa di una incertezza significativa sul modello statico, viene proposta una logica euristica di controllo basata su cicliche letture della corsa della sospensione e quando questa si trova al di fuori di una certa soglia, la logica viene attivata. Test sperimentali hanno validato gli approcci proposti sia per la logica semi-attiva che per il controllo load levelling.
Semi-active and load levelling control of a four-point suspended tractor cab
UGGÈ, ANDREA;MARCARINI, PAOLO
2018/2019
Abstract
Agricultural vehicles are mostly driven on roads or off-roads characterized by important roughness. As consequence, drivers are subjected to harsh working conditions, due to high vibrations for a long period of time. Therefore, the improvement of driving comfort, in the last decades, has been object of the research studies. This thesis is the result of a collaboration between Politecnico di Milano and Argo Tractors, a well-known manufacturer of leading agricultural machinery, and aims at the development of control strategies for a four-point suspended tractor cab equipped with hydro-pneumatic actuators. In particular, this problem, to which this work is addressed, can be divided in two parts: the first one deals with the semi-active control of the suspension system. At first the optimal damping level is retrieved through the suspensions’ passive characterization. This passive configuration does not prevent the end-stop impact in the case of important road disturbances, indeed an end-stop avoidance logic is proposed and implemented on the prototype, through a static map of the damping current. The second part concerns the load levelling problem. A dynamic physical model of the suspension and the cab is developed and identified through the S.E.M (Simulation Error Method) identification algorithm. Due to the significant uncertainty of the static model an heuristic load levelling controller is proposed. It is based on cyclic acquirements of the suspensions’ stroke signals and when the latter are under or above a certain threshold the controller is activated. Experimental results validate the overall approaches both for semi-active and load levelling control.File | Dimensione | Formato | |
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2019_12_Uggè_Marcarini.pdf
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Descrizione: Semi-Active and Load Levelling Control of a Four-Point Suspended Tractor Cab
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https://hdl.handle.net/10589/152524