Design And Experimental Study Of Self-excited Vibration Device Of Rotary Tillage Tool

As a new kind of machine,vibratory rotary cultivator can effectively reduce the energy consumption of rotary tilling and trenching.The key component is the vibration generator.In this paper,with the radius of gyration and installation spacing as constraints and considering the stroke of each freedom degree,a device and method for the rotary blade to generate self-excited vibration was proposed and a geometric topology was designed to realize the movement in the direction of the three degrees of freedom.The requirement of the intensity of the designed geometry was confirmed through the determination of the relevant stiffness connection location with the force analysis and the static analysis of key components based on ANSYS Workbench.By analyzing the dynamics equations of each degree of freedom,and according to the average force amplitude in each direction during the operation of the rotary blade,the appropriate topological connection stiffness range in each direction of the freedom degree of the self-excited vibration device was determined.Besides,the natural frequency of each order of the system was obtained by establishing a virtual prototype model of the device and conducting modal analysis.According to the actual working conditions,the suitable cutter type was selected.By establishing the tool nose path motion equation for the forward and reverse rotation of the traditional rotary tillage blade,the relationship among the cutting pitch,the traveling speed and the cutter shaft speed was analyzed,as well as the theory of how the reverse rotation could reduce the energy consumption of rotary farming and improve the quality of farming.The method of time-domain integration and frequency-domain integration of the vibration acceleration was analyzed,and the vibration amplitude was obtained by integrating the vibration acceleration of the blade,which provided a basis for the experimental study of the mechanism of vibration drag reduction.The soil bin test was performed based on the designed model machine.The results showed that the rotational speed of the rotary knife under the test conditions was in the range of 220-440(r/min),and the average input torque of the rotary cultivator was greatly reduced,with a percentage of as large as 19.3%,compared with the traditional rotary tillage method.However,under the condition of low speed(180 r/min)and high speed(500 r/min),the average input torque of the rotary cultivator was higher than that of the traditional rotary tillage method.Therefore,the use of vibratory rotary knife could help reduce the energy consumption of the tilling in a suitable rotational speed range.Its first-order natural frequency was obtained by analyzing the free vibration of the blade,which was similar to the simulation result.The analysis of the blade vibration data showed that as the rotation speed gradually increased,the blade gradually reached resonance,the vibration amplitude increased,and the input torque decreased;while as the rotation speed further increased,the soil throwing process would consume a large amount of energy and the input torque would increase.Therefore,an appropriate reduction of the natural frequency of the device can achieve resonance in a low speed range,while have a drag reduction and energy reduction effect in a large speed range.