Based on the investigation on vibration characteristics of certain off-road vehicle, a new type of damping-adjustable hydro-pneumatic suspension was put forward. After the analysis of its working principle, the nonlinear dynamic mathematical models of this suspension were set up. Using the method of theoretical calculation and simulation by MATLAB/Simulink, the nonlinear vibration characteristics of this damping- adjustable hydro-pneumatic suspension were studied, including static and dynamic stiffness, dynamic output force and damping force.

Based on the mathematical model of quarter car body model being put forward, the indoor platform experiment of quarter car body with hydro-pneumatic suspension system was done. During test, the parameters of dynamic wheel load along with the change of vibration amplitude and frequency were investigated. The results show that: the cycle of acceleration of sprung mass has half cycle lag than unsprung mass, and the main parameters of dynamic wheel load has increased significantly along with the increase of vibration amplitude and frequency. At the same time, through analysis the acceleration time responses of sprung and unsprung mass, it can be shown that hydro-pneumatic suspension has good anti-vibration performance.

Because of the problem of key joint or spline joint, the isometric polygonal profile connection was put forward, and the mathematical model of isometric polygonal curve was analyzed in this paper. Based on the periodicity characteristics of equivalent effective stress and total displacement in the whole structure through preliminary analysis, 1/3 structure of isometric polygonal profile shaft and hub was adopted during geometry model being established. The shearing strength in isometric polygonal profile hub and shaft, the main stress in hub and the total strain in shaft were calculated and analyzed based FEM.

From the NC machining principle of spiral bevel gear, the motion relationship of machine tool, cutter and workpiece during machining spiral bevel gear was analyzed. Based on the machine coordinate system, the tooth surface equation and the cone equation of cutting edges of spiral bevel gear were put forward. 3D solid model of spiral bevel gear was constructed using Pro/E Wildfire2.0 software. The NC milling simulation was carried out by the VERICUT software, and at the same time, the experiment was researched. Simulation and experimental results show that the spiral bevel gear can adopt the method of CNC machining, and can ensure the high quality, especially for single or small batch production.

Based on the analysis of vibration characteristics of certain off –road vehicle, and research of effect of front axle suspension to vehicle and parameter matching, a new type of damping-adjustable hydro-pneumatic suspension was put forward. After the analysis of its working principle, the nonlinear dynamic mathematical models of this suspension were set up. Using the method of theoretical calculation and simulation by MATLAB/Simulink, the characteristics of damping force of this damping-adjustable hydro-pneumatic suspension were studied.