| Researches show that vibration has great influence on health of human body. For off-road vehicles’ drivers, who work and run in bad environment commonly, bear vibration of high strength and low frequency for a long time will have their lumbar vertebrae, backbone, thorax and viscera injured, even cause fatigue and reduce work efficiency. In order to improve the ride environment of off-road vehicles, seat vibration reduction seams the most direct, simple and economic method, and the magneto rheological damper is an important guarantee to damping of driver suspension. A new type damper named magneto rheological damper, which can provide vibration isolation of three directions, was proposed. In this study, a ride comfort analysis test of ordinary driver seat and driving cab was concluded to find natural frequency range of human-seat system and driving cab system. Structure parameters of MRD were designed and calculated based on vibration isolation theory and damper design theory. By using Ansys, the magnetic circuit of MRD was simulated and studied. Then the MRD was manufactured and through performance test on bench, the damping characteristics of MRD were studied. The specific contents including:1. A ride comfort test for driver seat and driving cab of off-road vehicles was made to evaluate acceleration time history at speed of8km/h, lOkm/h,12km/h respectively. By utilizing the dynamics analytical software ADAMS to deal with test data, the natural frequency range of driver seat and driving cab were valued. The natural frequency of human-seat was reasonably matched based on study of excitation frequency, vehicle and driving cab natural frequency, and human body sensitive frequency.2. By studying vibration isolation theory, the vibration differential equation of the system was established. Damping force of MRD in three directions was calculated according to the natural frequency of human-seat system. And structure parameters of MRD were designed and calculated by studying damper design theory.3. Ansys simulation was done to analyzing magnetic circuit characteristics in condition of different wall thickness, different core diameter, different damping channel length, different damping channel clearance and different coil current. Then the change rule of magneto rheological fluid flux density in damping channels at different parameters was concluded, the feasibility of magnetic circuit design was verified, and the structure parameters were optimized.4. The MRD was manufactured and it’s characteristics test was made on bench. Using LMS acoustic vibration analyzer to record displacement sensor’s and pressure sensor’s data. The damper damping force change rule in different vibration speed and coil current was analyzed. Actual damping force range and damping force controlled multiple range were concluded.Researches show that the MRD indicator diagram is mellow and full, that means MRD overall performance is good. The damping force of MRD keeps growth with vibration speed and coil current. The actual maximum damping force of205N is less than the theoretical calculation value. But magnetic circuit simulation conclusion shows, when the coil current of2A, vibration speed of0.5m/s, MRF magnetic flux density value is0.231T, which do not attain to MRF saturation flux density, in real vehicle applications, it can improve coil current if coil current allowed in order to adapt to the seat suspension vibration isolation demand. The MRD damping force controlled multiple can be up to a maximum of3, which means MRD damping force adjustable scope is wide. The damping force controlled multiple decreases with increase of vibration speed. This MRD on driver seat can meet the vibration isolation requirements of seat suspension.The research of this project has important theoretical and practical value because it not only can promote the scientific research of driver’s suspension for off-road vehicles, but also can improve vehicle ride comfort and decrease the occurrence risk of occupational disease caused by vibration. |
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