The hydro-pneumatic suspension, known for enhancing vehicle ride comfort and stability, finds widespread use in engineering vehicles. Presently, the majority of mining trucks employ hydro-pneumatic suspension with a fixed damping hole, underscoring the critical importance of selecting appropriate damping hole parameters. Initially, an equilibrium mathematical model of the ¼ hydro-pneumatic suspension is established, and the influencing factors of the damping characteristics are analyzed. Subsequently, the simulation model and experimental bench for the hydro-pneumatic suspension are constructed. Sinusoidal signals with different frequencies and amplitudes serve as the excitation signals to analyze the variation trend of the force on the rod with displacement changes. The simulation and experimental results demonstrate a high degree of consistency, validating the rationality and validity of the simulation model. Building upon this foundation, various damping apertures are then selected to study the damping characteristics of the hydro-pneumatic suspension. The research indicates that as the damping aperture increases, the setting time of the hydro-pneumatic suspension system after excitation extends, accompanied by a decrease in the acceleration overshoot. As a result, a comprehensive evaluation index is developed, considering various factors, such as different weight setting times and peak longitudinal accelerations to assess the ride comfort of the suspension. This approach is then employed to determine the optimal damping aperture under both full-load and no-load conditions. The findings of this research offer valuable insights for the development of adaptive variable damping hydraulic suspensions, especially under variable load conditions.

Automated operations are widely used in harsh environments, in which position information is essential. Although sensors can be equipped to obtain high-accuracy position information, they are quite expensive and unsuitable for harsh environment applications. Therefore, a position soft-sensing model based on a back propagation (BP) neural network is proposed for direct-driven hydraulics (DDH) to protect against harsh environmental conditions. The proposed model obtains a position by integrating velocity computed from the BP neural network, which trains the nonlinear relationship between multi-input (speed of the electric motor and pressures in two chambers of the cylinder) and single-output (the cylinder’s velocity). First, the model of a standalone crane with DDH was established and verified by experiment. Second, the data from batch simulation with the verified model was used for training and testing the BP neural network in the soft-sensing model. Finally, position estimation with a typical cycle was performed using the created position soft-sensing model. Compared with the experimental data, the maximum soft-sensing position error was about 7 mm, and the error rate was within ±2.5%. Furthermore, position estimations were carried out with the proposed soft-sensing model under differing working conditions and the errors were within 4 mm, but the periodically cumulative error was observed. Hence, a reference point is proposed to minimize the accumulative error, for example, a point at the middle of the cylinder. Therefore, the work can be applied to acquire position information to facilitate automated operation of machines equipped with DDH.

In order to improve the environmental adaptability and sealing performance of the rotating seal, the principles and failure mechanisms of the rotating seal in ambient pressure in deep-sea is researched. It is proposed that the excessive friction caused by the ambient pressure and the magnitude of interference is the main reason for rotating seal failure. To reduce friction effect, a combined lip seal is designed, whose structure consists of a rotating seal made of polytetrafluoroethylene (PTFE) and an O-shaped fastening ring. The finite element analysis results indicate that the contact pressure in sealing surface increases with the growing magnitude of interference, but decreases when it exceeds the value 0.65mm. A suitable range (0.5×10 m ~0.6×10m) for the magnitude of interference is concluded for this combined seal. Finally, the designed PTFE rotating seal is tested in a deep-sea imitating hull, and the experimental results show that the seal is able to work reliably without leaking for more than 10 hours in the ambient pressure less than 30MPa, and verifies the design of the rotating seal is rational, which displays that the seal is available for the special requirement of deep-sea environment in short periods.

In this study, a theoretical model was established for longitudinal braking stability (LBS) of a lightweight liquid storage mini-track vehicle to investigate its behaviors. The influence of the tank liquid filling ratio (TLR), initial velocity (IV), and initial braking deceleration (IBD) on the LBS of the tracked vehicle was studied via FLUENT simulation. The simulation results showed that when the IV and the IBD were constant, the TLR significantly affected the braking efficiency. Conversely, when the TLR was 0.7, the braking efficiency decreased by 32%, resulting in the worst LBS. The braking efficiency at different IVs decreased by ~30% when using a constant IBD and TLR, and the braking stability exhibited little difference. Further, the braking efficiency decreased noticeably with increasing IBD; meanwhile, the braking longitudinal stability worsened. When the IBD was increased to 5 m⋅s⁻², the braking efficiency decreased by 48.4%. The road experiment showed that when the tracked vehicle was accelerated and braked under limit conditions, the stability requirements were met. Finally, by combining the simulation and road experiment, the driving parameters of the tracked vehicle that could satisfy the LBS were obtained.

Variable pumps are important hydraulic power units in deep-sea exploitation due to their good energy-saving and high precision capabilities. However, their application in such hostile environment suffers from the risk of control failure. Moreover, developed throughout trials and error in onshore simulation experiment, it is thus not just a time-consuming and expensive task but also required to implement an adaptive scheme capability to be used in deep-sea application. In this paper, a self-adaptive pressure sensing scheme and a novel close-loop control structure involved oceanographic environment adaptive variable pump (OEAVP) are proposed to autonomously adapt to the variable seawater conditions. Furthermore, based on environmental and fluid models, dynamic performances of the OEAVP model for pressure and flow-rate controls are analyzed. MATLAB/Simulink pack tool is used to perform the OEAVP system stability and comparative deep-sea water and shallow-water stability control are addressed. It reveals oceanographic environment influences on control performances of OEAVP from the direct effect of ambient pressure and the indirect effect of hydraulic fluid properties changes. Ultimately experimental tests including SPSS performances, control characteristics and dynamic responses of OEAVP’s are performed in a simulation hull, which demonstrates consistent performances in oceanographic environment and confer to the proposed OSVP with high adaptive capability.