Experimental and Theoretical Consideration on Nonlinear Vibration of the Japanese Head-feeding combine

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Experiments under the stationary and harvesting conditions of the Japanese head-feeding combine, were performed in order to investigate whether the vibration characteristics of the combine featured periodic or semi-periodic or chaotic.Therefore, 6 degrees of freedom components of acceleration at the location of the center of the gravity, and 3 degrees of freedom of acceleration at the location of the operator seat were measured independently. Finally, vibration characteristics of the combine were estimated with the power spectrum density, phase trajectory, Poincare section, and Lyapunov index of the time series data of accelerations.From this research, the following results were obtained.1.Vibration of the combine under the stationary condition (engine, thresher and cutter are driven without harvesting) are mainly influenced by the engine. Further, 1/2,1/3 (subharmonics) frequency components of the engine are observed besides engine driving frequency component (45Hz). From these result … More s, Vibration characteristics under the stationary condition are estimated to indicate semi-periodic nonlinear vibration.2.Vibration of the combine under the harvesting condition are influenced by the engine, threshing unit and driving unit. Namely, some kinds of vibration frequency components in harvesting are observed compared with stationary condition. Further, 1/2,1/3 (subharmonics), 2/3 frequency components of the engine are observed besides engine driving frequency component as same as stationary condition. From existence of these low frequency components, Vibration characteristics under the harvesting condition are estimated to indicate semi-periodic nonlinear vibration with some kinds of frequency components.3.Existence of the chaotic vibration was not recognized due to Lyapunov index whose valuse are -1.0 - -3.0*10^<-3> and due to without existence of period doubling bifurcation.4.Low frequency components such as subharmonics should be reduced from the viewpoint of the human technology in order to design combine harvester with comfortable ride quality. Less