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Before predicting the vibration characteristics of a tractor/implement system with front axle hydro-pneumatic suspension, it is essential to develop a dynamic model. The nonlinear stiffness and damping calculation equations for hydro-pneumatic suspension are derived and the complete three dimensional multibody dynamic model of the wheeled tractor/implement system is presented in this paper. The construction of the model considers the effect of implement and passive rub cabin suspension as well as front axle hydro-pneumatic suspension together. The vibration responses and the corresponding power spectral densities (PSD) of driver seat, cabin, chassis and implement under different forward speed and field road conditions gathered from the simulation using the models are in good agreement with experimental results, demonstrating the effectiveness of the proposed model. A comparative investigation on the dynamic effects of a passive cabin suspension, implement and front axle hydro-pneumatic suspension under four cases was made. The effects of front axle suspension and the implement on the rollover limit chart for the tractor system were also studied. Simulation results showed that the front axle hydro-pneumatic suspension will deteriorate the ride comfort of drivers but will improve pitch and roll stability. Passive cabin suspension plays a more important role in improving the ride comfort of drivers than the front axle hydro-pneumatic suspension does, while compromising the pitch stability to some extent. The implement will raise the riding comfort of drivers and the pitch stability of tractors, but dramatically worsen the roll stability. The presence of the front axle suspension and the implement improves the minimum slope angle and reduces the maximum slope angle. Furthermore, the effect of the initial nitrogen volume, the pressure of energy accumulators, and the orifice diameter of the small throttle valves on the vibration characteristics of the tractor system with the large throttle valve closed or fully opened is also investigated. Image 1 • The front axle suspension will deteriorate the ride comfort but improve the pitch and roll stability obviously. • The passive cabin suspension plays an important role in improving the ride comfort, while aggravating pitch stability. • The implement will raise the comfortableness and pitch stability of tractor, and worsen the roll stability. • The front axle suspension and implement improves this minimum slope angle and reduces the maximum slope angle. [ABSTRACT FROM AUTHOR]

It is necessary to establish a dynamic model to predict and evaluate the dynamic performance of closed high-speed press system during design procedure, when it is impossible to carry out the test of prototype. In this work, a dynamic model for the closed high-speed press system is developed to predict and evaluate its dynamic performance. Unlike in previous models where the press frame is considered to be a single mass and the effects of the transmission mechanism and complex frame structure are neglected, the present model can be used to analyze the dynamic response of a multi-body vibration-impact system treating it as a coupled one. The simulation results reveal that the dynamic responses of press under piling condition include a transient impact and a free vibration process. The vibration acceleration and velocity curves of the upper beam of the closed high-speed press decrease with the increasing speed of rotation. In contrast, vibration acceleration and velocity curves of the lower beam of the press increase with the increasing rotation speed. The experimental results demonstrate that the dynamic model proposed herein is consistent with the actual working state of the closed high-speed press and the validity of the dynamic model is verified. [ABSTRACT FROM PUBLISHER]