Analysis Of Vibration Source & Response And Identification Of Transfer Main Path Of Crawler Grain Combine Harvester

There are many problems in the domestic crawler-type full-feed grain combine harvesters,such as the large number of vibration sources,the complex vibration characteristics,unclear vibration transmission path,and lack of vibration control methods.In order to solve these problems,taking crawler full-feed longitudinal-axial flow combine harvester as research object,the following work has been carried out in this thesis by means of dynamic analysis,test detection,signal analysis and vibration contribution sequencing.1.By utlizing the established vibration detection system for combined harvesters,the vibration characteristics of several types of crawler combine harvesters under no-load in-situ and the vibration characteristics of longitudinal-axial-flow prototype under multi-working-conditions were measured and compared.In this part,three types of domestic combine harvesters,i.e.tangential-longitudinal axial flow combine harvesters,tangential-cross flow combine harvesters and double-cross-axial flow combine harvesters,and a longitudinal-axial flow type combine harvester made by Japanese were selected to detect the vibration under the large throttle condition without working load.The vibration under idle process,full throttle and field harvesting conditions were detected systematically with the longitudinal axial flow machine as the prototype,and the vibration of 4 excitating sources were detected by being excited separately,and the vibration of cutter and engine were also detected when they were stimulated simultaneously.The peak value and Root Mean Square value of vibration signal at each measuring point were obtained,and the frequency components and their amplitudes were obtained by frequency-domain analysis.The time-frequency domain analysis was carried out to understand the variation of each frequency component in time domain.2.Establishing the kinematics and dynamics model of the main excitation source of the combine harvester.According to the structural characteristics of the combine harvester,the excitation source transmits the vibration caused by its own motion toother structures through the reaction of alternating branches at the joints.The structure of each excitation source was analyzed comprehensively,and the kinematics vector equation and the dynamic force and moment balance equation were established.3.Analysising and sequencing method of vibration transmission paths of each source.(1)By analyzing the drive system of the cutting table,it was pointed out that the cutter and its transmission system were connected with the cutting table through three parts.It was found that the frequency components were different except the fundamental frequency,and there were weak correlation relationship between the signals of the 3 points.Therefore,the partial coherence function method was introduced.(2)The support structure of the vibrating screen is analyzed.It was shown that the vibrating sieve transmits vibration to the combine harvester body through the front slider chute and the drive shaft support.The acceleration of the connection points was detected and analyzed,and found that the excitation of the connection points was strongly correlated.A path contribution analysis method based on transfer path model was introduced.The generalized inverse matrix of the frequency response function with additional reference points was used to calculate the excitation force,and the contribution of the excitation force to the analysis of the point vibration response is further studied.(3)Through analysising of the supporting structure of threshing rotor,it was pointed out that the pulling force at the dynamic input end will increase the supporting reaction force at the input end of the rotor shaft,so this was the main path of the vibration of the threshing rotor.(4)The transmission rates of different rotational speeds and frequency components were calculated on the basis of measuring the vibration spectrum characteristics on both sides of the engine mount.4.By summarizing and analyzing the test results,the vibration response expression model was modified to the form of multi-frequency,amplitude and phase modulation harmonic signal combination.In this thesis,the vibration reduction optimization of combine harvesters was discussed from the aspects of vibration characteristic modeling,detection method and signal analysis,vibration transmission path analysis and transmission control.Theproposed transfer control method is of practical significance and lays a foundation for the future research.