Influence of sugarcane harvester cutterhead axial vibration on sugarcane ratoon cutting quality

Abstract: In view of the problems of the low cutting quality of sugarcane ratoon, literatures at home and abroad mostly focus on the study of machine structures and movement parameters of harvester, neglecting possible influence of cutterhead's vibration on sugarcane cutting. Research team discovered in the earlier research stage that there were certain connections between cutterhead vibration of sugarcane harvester and ratoon cutting quality. Based on early theoretical analysis, research team gave further studies on their relationship by controlling the axial vibration of cutterhead triggered by different weights of sugarcanes on cutterhead. To realize controllable axial amplitudes of cutterhead, we analyzed the mechanism of axial vibration generated by rotor dynamics. It was concluded that during the cutting movement an eccentric mass on the cutterhead produced axial vibration: owing to the existence of eccentricity, dynamic deflection was created under the action of centrifugal force when the cutterhead was rotating, and then the axial harmonic force which related to the eccentric distance was produced, forcing the cutterhead to generate axial vibrations. This suggestion was verified by a series of single factor experiments. An unbalanced mass, the position and mass of which could be varied, was installed on the cutterhead of the self-developed laboratory platform to achieve controllable axial vibrations and measurable vibrations produced when sugarcane roots were cut and transferred on the simulating cutterhead. In this series of single factor experiments, the amplitudes at a fixed point on the edge of cutterhead on axial direction were measured by the laser displacement sensor in terms of changing unbalanced mass. The experiments also realized controllable axial vibrations of cutterhead. Based on the above results, under the controllable axial vibration conditions, a series of single-factor and orthogonal experiments of sugarcane ratoon cutting were carried out. Taking the length and width of sugarcane ratoon crack and the number of experimental ratoons as experiment indices, we completed the comprehensive evaluation on sugarcane ratoon cutting quality with the improved entropy method, and further carried out the variance analysis, correlation analysis and regression analysis. Experiment results showed that: 1) The cutter's axial vibrations could be controlled by various weights and positions of unbalanced mass. The controllable range was 0.91-2.59 mm under the experiment conditions and there is a strong positive correlation between unbalanced mass and cutterhead amplitude.2) With the statistics, the linear regression equation of sugarcane ratoon cutting quality and cutterhead axial vibration was made. It was found that there was a strong positive correlation between the axial amplitude of cutterhead and the sugarcane ratoon cutting quality, and the correlation coefficient was 0.87. The regression equation suggested the sugarcane cutting quality was sensitive to the changes of cutterhead axial amplitude. 3) Under the orthogonal test condition, unbalanced mass had the significant influence on ratoon cutting quality and axial vibration of cutterhead at the significant level of 0.05; and it was suggested that among the 3 factors i.e. cutterhead unbalanced mass, cutterhead rotation speed and sugarcane conveying speed, the first one had the most significant effect on cutting quality, the sugarcane conveying speed ranked the second, and the cutterhead rotation speed had the least influence. Due to the strong positive correlation between cutterhead unbalanced mass and cutterhead amplitude, the significant influence on cutting quality brought by cutterhead axial amplitude could be confirmed. This paper preliminarily reveals the impact rule of cutterhead axial vibration on sugarcane ratoon cutting quality, and provides the reference for further studying the breaking mechanism of root caused by cutterhead vibration during the cutting, exploring the sugarcane harvester's design method based on dynamic characteristics, and developing the sugarcane harvester suitable for hilly area.