Design And Test Of Online Dynamic Balance Detection System For Multi-roller Structure Of Combine Harvester

Rotating machinery is a major structure of mechanical systems.Rotor unbalance is one of the main reasons for the vibration of rotating machinery and the faults.Although the balancing of the individual components is carried out on the balancing machine before the threshing drum of the combine harvester is assembled,a plurality of threshing drums combined with the belt drive and the chain drive will create a new unbalance.The unbalance of the threshing drum will cause the meshing shock and vibration during chain transmission,and the lateral vibration will generate a large dynamic load,which will aggravate the jitter of the chain.In view of the above problems,this paper chooses a representative chain drive,takes the threshing drum in the combine harvester as the research object,and studies the influence relationship of the balance state between the multiple rollers based on the chain drive,thus developing a multi-roller online dynamic balance detection system.The main research contents of this paper are as follows:(1)The structural characteristics of the threshing drum and its transmission characteristics were studied to determine the rotor type of the threshing drum.The force analysis of the chain drive theoretically proves that the chain tension has a certain influence on the balance state of the threshing drum.At the same time,because the tension generated by the chain in different transmission paths is also different,the transmission path will be classified according to the calculation method of the contact angle of sprocket,and the multi-roller dynamic balance test bench is designed based on this classification.(2)Understand the classification,unbalance reason,balance principle and balance method of the rotor,combine the structural and transmission characteristics of the multi-roller systems,select the dynamic balance method suitable for the threshing drum,and determine the calculation method for extracting the unbalanced amount of the threshing drum,and clarify the basic plan of the detection system design.(3)Calculate the response of the rotor to the lateral vibration of the chain drive.Based on the lateral vibration of the chain drive,the differential equation of the chain drive system is established,and the natural frequency of the free vibration of the system and the excitation response equation generated by the rotor are calculated.It is theoretically proved that the lateral vibration of the chain drive does have an effect on the vibration of the rotor.At the same time,the response equation is compared with the transmission type to find the connection between the vibration condition of the rotor and the type of transmission.(4)The relevant bench test is carried out on the multi-roller dynamic balance test bench to establish a multi-roller dynamic balance model.Complete random weight test of the radial and axial directions of the driven roller end face,and the master-slave dynamic balance test based on the transfer characteristics.The calculation method of equivalent unbalance of chain drive is proposed,and based on this,the multi-roller dynamic balance method with "multi-stage transmission and step-by-step balance" as the core is determined to verify the unbalance of the drum itself and the equivalent unbalance of the chain drive.(5)Determine the overall design,hardware and software configuration of the detection system,and design a human-computer interaction interface.With LabVIEW as the development platform,the system can realize data acquisition,data storage,signal time domain,spectrum analysis,filtering,speed measurement,unbalance measurement and other functions in single-roller and multi-roller modes.Design the chain drive equivalent unbalance calculation model,and the assist system calculates the unbalance amount in the multi-roller mode.Finally,the function test of the developed multi-roller online dynamic balance detection system is carried out.Finally,the functional test of the developed multi-roller online dynamic balance detection system is carried out to verify the effectiveness of the multi-roller dynamic balance model.