| Studies have shown that drivers under low frequency vibration of high strength for a long time during off-road vehicles driving and operating in the field.Vibration can cause lumbar push,spine,chest and insides damage,even cause fatigue driving,reduce the work efficiency.With the increasing of off-road vehicles driving comfort,seat suspension is one of the most simple and economic method.The semi-active seat suspension is a hot research topic in recent years.The stiffness and damping of the semi-active suspension were controlled respectively in the present research at home and abroad.Due to the nonlinear characteristics,time-variant parameters and uncertainty driving conditions of suspension system,it is difficult to actual achieve the exact match of stiffness and damping.The paddy field hard bottom roughness was measured,riding comfort of the tractor in paddy field conditions was analyzed,and the natural frequency scope of tractor front axle,rear axle and seat surface were achieved.Combining with the vibration isolation and design theory of damping pillar,this paper presents a new type of a coaxial integrated damping pillar design scheme,Introduces the basic components,damping adjustment principle and nonlinear stiffness characteristics of a coaxial integrated damping pillar based on air spring with additional air chamber and MR damper.MR damper was adopted to realize stepless regulation of damping changes.The structure parameters of a coaxial integrated damping pillar were designed and calculated,shock absorber of the magnetic circuit was simulation analyzed by using ANSYS software.A coaxial integrated damping pillar was developed,and the static stiffness and dynamic output force were studied by bench test.The main research contents and conclusions were generalized as follows:Selection the cohesive rice soil road in Nanjing Jiangpu farm agriculture test center as experimental ground.The random elevation of paddy field hard bottom roughness was obtained through a self-designed measuring device by the tire rolling method,and analyze the data.The results showed that the paddy field hard bottom contour elevation has a statistical correlation,elevation changes is a stationary random process.Road roughness coefficient Gx(0.1)=316.7×10-6m-3,frequency index w=-1.651,The road spatial frequency is below 0.7m-1(wavelength ??1.43m),the road surface grade of paddy field hard bottom roughness is C.But the road surface grade of paddy field hard bottom roughness between D and E,when the road spatial frequency is above 0.7m-1(wavelength ??1.43m).Taking the CF700 tractor as the research object,tractor 3-DOF planar vibration model in paddy field conditions was built up according to tires-soft wet paddy soil system.With measured curve of road profile as the road excitation,the vertical natural frequency of tractor front axle,rear axle and seat surface in paddy field conditions were simulated according main parameters of the tractor,and compare the simulation and experimental results.The results show that the vertical natural frequency of tractor front axle,rear axle and seat surface were 2.91 Hz?3.6Hz?2.5Hz respectively achieved by experiment,and simulation of vibration natural frequency is 3.49Hz,3.34Hz,2.9Hz respectively.The relative error of simulation and experimental results is 19.9%,7.2%and 16.0%respectively.Relative errors are in the allowed range,and it has a good consistency.The vibration isolation property of seat suspension was evaluated by simulation results.Aiming at the problem of poor vibration performance of seat suspension system,In this paper,a vibration damper for vehicle seat suspension was proposed.Air spring,auxiliary chamber,magnetorheological damper was the mainly three parts.And the three parts was designed through coaxial integrated.Among them,the main air chamber and the additional air chamber were connected with each other through a hose through a proportional flow valve to form an air spring with an additional chamber.The magnetic rheological damper adopted the mixed mode of shear flow.The gas-liquid medium of magneto rheological damper and air spring had a dynamic correlation effect.The integrated suspension strut structural features was introduced.And the working principle of the vibration damper was analyzed.According to human sensitive frequency range and the natural frequency of seat installation,the natural frequency range of seat suspension was determined.And Structural parameters of vibration damper was designed.Each component of the vibration damper's material was selected.4.According to strut magnetic structure design parameters,a magnetic circuit simulation model was establish in ANSYS simulation software.The reliability of designed magnetic circuit was verify.The ANSYS software was used to simulate the magnetic field strength of the strut's damping gap,which provided a theoretical basis for the current size of the experiment;According to the effect of orifice area on the spring stiffness,the proportional valve was selected and the input voltage of the proportional valve was set.5.A new type of integrated shock strut was produced.The static stiffness characteristics and the output force characteristics were tested respectively.The strut's static stiffness test system was constructed.When the initial pressure was 0.2MPa,0.3MPa,0.4MPa,the strut's "flexible force-stroke" and "internal pressure-stroke" curves were obtained by measurement.The strut's dynamic output force test system was constructed.When the initial pressure is 0.3MPa,The variation law of the output force of the vibration damper is analyzed under different vibration speed?line current and input voltage of the proportional valve.The results show that the output force of the vibration damper can be adjusted in a wide range,which is in accordance with the vibration isolation requirements of seat suspension.Through the research of this topic,the pavement grade of paddy hard bottom was learned.A reference model for the research of vehicle vibration working in the paddy field was provided.The validity of the tractor's 3-DOF model that working in paddy field was verified.Provide theoretical basis for designing parameter of tractor's damping system.And the dynamics of the system is grasped through the experimental study of the shock strut.Seat suspension semi-active control theory system has been further improved.The design and implementation of a semi-active air suspension system with controllable output force is realized.To promote the application of the shock strut in vehicle damping system,improve the driver has important theoretical significance and practical value on the environment. |
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