As tractors mainly transit rural roads, drivers can suffer from harmful vibrations transmitted though their seats. Thus, the driving comfort in tractors with agricultural equipment should be evaluated. To investigate the effects of forward motion and front-wheel steering on the driving comfort of two-wheel-drive tractors with agricultural equipment, we establish a man–machine–road virtual prototype for simulations and validate it experimentally. First, a tractor that has suspended agricultural equipment and is operating at front-wheel steering angles of 0°, 12°, 24°, and 36° is driven on a random level-D road. Simultaneously, the vibration accelerations experienced by the driver are obtained along the X, Y, and Z axes with the coordinate system defined according to the ISO 2631-1 standard. The combined weighted root-mean-square (RMS) acceleration corresponding to the driver’s whole-body vibration increases from 0.205 to 0.909 m/s2 when increasing the steering angle. Then, considering the forward speed as the variable, the front-wheel steering angle is set at 30°, and the vibration accelerations experienced by the driver are obtained when the tractor travels at 4, 5, and 6 km/h on a random level-D road. The combined weighted RMS acceleration corresponding to the driver’s whole-body vibration increases from 0.68 to 1.03 m/s2 when increasing the speed. Therefore, we found that the velocity of a tractor should be reduced while steering, and excessively large front-wheel steering angles should be avoided to increase driving comfort.
The hatchway structure and operating mode were described according to the key technology of elevator safety device test tower. According to mounting structure of the ascending hatchway, the constraints of car-rail were proposed. According to constrains, the car-rail coupling dynamics models of moving and rotating were proposed at x-axis, y-axis and z-axis, and the vibration models were simplified to moving and rotating at z-axis. Based on simplified model, the dynamic characteristics of car were simulated when safety gear broken.
According to the failure features of amusement rides, the Fault Tree Analysis model of risk assessment for amusement rides was built based on technology risk, operation risk and management risk. Using Boolean algebra, the minimum cut set of fault tree and 24 kinds of accident way from top to bottom were obtained. In the fault tree, the failure probability of the bottom event was obtained according to triangular fuzzy probability. The failure probability and risk of amusement ride subsystem were obtained according to Boolean algebra method. The weights of the risk of each subsystem were obtained with successive analysis method, and the quantitative risk of amusement ride was obtained with the weight and risk of subsystems. According to the quantitative risk assessment model of fault tree, the quantitative risk assessment steps were introduced.
The entity model of gearbox for construct machinery was created with Por/E. The entity model was imported into ANSYS with IGES. The displacements, strains and stresses of the upper cover and lower box were calculated with finite element method. The gearbox was optimized on structure and material according to the calculation results. The weight of gearbox was reduced 16kg. The calculation results show that the strength and stiffness of optimized gearbox change little.
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