Abstract. In this paper, some considerations regarding a ground vehicle oscillating system based on chaotic behaviors are studied. The vehicle system is modeled as a full nonlinear seven-degree freedom with an additional degree of freedom for each passenger. Roughness of the road surface is considered as sinusoidal waveforms with time delays for the tires. The governing di erential equations are extracted under Newton-Euler laws and solved via numerical methods. The dynamic behavior of the system is investigated by special nonlinear techniques such as bifurcation diagram, time series, phase plane portrait, power spectrum, Poincar e section, and maximum Lyapunov exponents. The time delays between the tires are used as a control parameter. First, the vehicle behavior is investigated and the chaotic regions are detected. Then, the damping and sti ness coe cients are used to return to the regular behavior. Results show that by changing the system parameters and selecting the appropriate values, one can minimize vibrations as well as eliminate chaotic behavior. The comparison of the results obtained from the proposed model and those from the vehicle without passengers show the great di erences in the dynamic behaviors of the two models.
The chaotic vibration analysis of a heavy articulated vehicle (HAV) under consecutive speed control humps (SCHs) excitation is studied. The vehicle is modeled as a nonlinear half-truck oscillatory system with three axles. The suspension system between the truck bodies and axles is equipped with passive viscous damper and magnetorheological (MR) damper. The consecutive SCHs-speed coupling excitation function is presented by a half-sine wave with constant amplitude and variable frequency. The nonlinear dynamic behavior of the system is investigated by special respective techniques. Also, the ride comfort is assessed by the RMS value of truck bodies' accelerations. The results reveal that the quasi-periodic motion is observed at lower speeds when the truck moves on SCHs without load; while in the presence of the load, the dynamic characteristics of the system confirm the chaotic vibration possibility in a widespread range at higher speeds. Further studies indicate that the chaotic behaviors can directly affect on driving comfort and lead to the ride comfort becoming lower. The obtained results can be helpful in designing the oscillatory system for the heavy vehicles to preserve the comfort of drivers and the protection of load.
In this paper, the chaotic behavior of a ground vehicle system with driver subjected to road disturbances is studied and the relationship between the nonlinear vibration of the vehicle and ride comfort is evaluated. The vehicle system is modeled as fully nonlinear with seven degrees of freedom and an additional degree of freedom for driver (8-DOF). The excitation force is the road irregularities that are assumed as road speed control bumps. The sinusoidal, consecutive half-sine and dented-rectangular waveforms are considered to simulate the road speed control bumps. The nonlinearities of the system are due to the nonlinear springs and dampers that are used in the suspension system and tires. The governing differential equations are extracted under Newton–Euler laws and solved via numerical methods. The chaotic behaviors were studied in more detail with special techniques such as bifurcation diagrams, phase plane portrait, Poincaré map and Lyapunov exponents. The ride comfort was evaluated as the RMS value of the vertical displacement of the vehicle body and driver. Firstly, the effect of amplitude (height) and frequency (vehicle’s speed) of these speed control bumps on chaotic vibrations of vehicle are studied. The obtained results show that various forms of vibrations, such as periodic, subharmonic and chaotic vibrations, can be detected in the system behavior with the change of the height and frequency of speed control bumps and present different types of strange attractors in the vehicle with and without driver. Then, the influence of nonlinear vibration on ride comfort and the relationship between chaotic vibrations of the vehicle and driving comfort are investigated. The results of analyzing the RMS diagrams reveal that the chaotic behaviors can directly affect the driving comfort and lead to the driver’s comfort being reduced. The obtained results can be used in the design of vehicle and road bumps pavement.
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