| Researches show that vibration has great influence on health of the human body. For off-road vehicles'driver, who works and runs in worse environment commonly, bears vibration of high strength and low frequency for a long time, his lumbar vertebrae, backbone, thorax and viscera will be injured, physical and mental health will be damaged seriously. In order to improve the ride environment of off-road vehicles, a new type seat suspension system which named hexapod suspension was proposed. In this study, the free vibration model of body and seat was set up, appropriate topology structure for hexapod suspension was chosen and parameter optimization was conducted, the vibration isolate seat based on hexapod suspension was designed and manufactured. Through real vehicle experiment, its vibration characteristic was studied. The specific contents including:(1) By means of mechanism topology theory, topology type which fit for hexapod suspension was integrated out. According to the composition theory of 6-DOF parallel mechanism which based on Single-Open-Chain units, comprehensive study for hexapod suspension structure was carried out. Appropriate Single-Open-Chain and mixed Single-Open-Chain was constructed for hexapod suspension. Eighteen types of structure and extension structure which suitable for hexapod suspension was synthesized by using permutations and combinations methods.(2) General mechanical model of driver-seat suspension system was established, the differential equations of motion was deducted. In order to obtain the driver's inertial parameters, the human body was divided into several parts when it was in a comfortable sitting position, then the inertial parameters were calculated by using quality parameters and dimension parameters of the human body provided by GB-T 17245-2004 "Inertial parameters of adult human body" and GB/T 14779-93 "Design requirements of functional template for the sitting human body". (3) According to the performance requirements of driver's seat suspension, comparison and analysis of hexapod suspension topology structure which has integrated before was proceed in three aspects, including the structure, natural frequencies and coupling degree, vibration isolate effect simulation. The Stewart double-triangular structure type was chosen finally which fit for the hexapod suspension best.(4) According to the sensitive frequency range of the human body and off-road vehicle's six natural frequencies, parameter optimization design was conducted for Stewart double-triangle hexapod suspension, including the geometry parameters, stiffness of the spring and damping of the damper. Finally, the natural frequencies of hexapod suspension not only avoid the vehicle's natural frequencies, but also away from the sensitive frequency range of the human body in six directions.(5) Physical prototype of the hexapod suspension was designed and manufactured, real vehicle experiment was executed to test the acceleration values of cushion (Z direction), seat's back (X direction) and the cab floor (X, Y, Z three directions), the dynamic of hexapod suspension system under different speeds and different loads was studied and compared with normal RS-S type seat.Researches show that the hexapod suspension seat has vibration isolation effect in all 6 directions. Compared with normal RS-S type driver's seat, the weighted acceleration RMS of hexapod suspension seat was bigger than the normal seat at low speed(2.5<υ< 4km/h), but when the speed v>4km/h, the weighted acceleration RMS of hexapod suspension seat was smaller than the normal seat. Besides, with the increase of the speed, the weighted acceleration RMS compared to the normal seat decrease more significant.The research of this project has important theoretical and practical value because it not only can promote the scientific research of driver's seat 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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