Laser powder bed fusion (L-PBF), as one of the additive manufacturing technologies, has become one of the most promising techniques for producing components with complex geometries. While L-PBF enhances design freedom for aircraft hydraulic channels, challenges such as improving surface quality and oxidation behavior in overhang structures remain critical issues. This research experimentally investigates the effects of key process parameters, including laser power density, spot diameter, and layer thickness, on the surface roughness and oxidation behavior of the top overhang surfaces of hydraulic channels. The formation mechanisms of incompletely molten particles and microcracks on overhang surfaces are revealed. The microstructure of the overhang surfaces is examined using scanning electron microscopy (SEM), and the distribution of oxygen in fully and partially molten regions is examined using energy dispersive spectroscopy (EDS) to clarify the relationship between incomplete melting and oxidation. Experimental results show that higher laser power densities not only exacerbate surface roughness but also promote oxidation in incompletely molten areas. For hydraulic channels with a diameter of 10 mm, the spot diameter of 130 μm, and layer thickness of 40 μm effectively reduce surface roughness at the top of the channel. Compared to unmelted and fully molten regions, the oxygen level in partially molten regions is much higher. Both the oxygen content in molten and incompletely molten regions decreases with increasing layer count during fabrication. Using fresh powder reduces both the surface roughness of overhang structures and the oxide content. This study provides theoretical insights and practical guidance for the application of L-PBF technology in aircraft hydraulic channels.

With the continuous development of science and technology and the growing severity of energy issues, load-sensitive drive systems have attracted significant attention in the electro–hydraulic servo field due to their high energy efficiency. Currently, most research primarily focuses on introducing load-sensitive valves to achieve load-following through hydraulic-mechanical feedback. This approach has partially achieved the energy-saving goal, but issues such as reduced dynamic response speed and limited load-sensitive range due to mechanical structures remain. This paper proposes an active load-sensitive variable displacement drive system that no longer relies on mechanical structures for load-sensitive adjustment. And multiple energy efficiency mapping relationships are designed to complete the system’s load-sensitive adjustment, thereby reducing throttling losses. Additionally, a dual-loop anti-disturbance control method based on energy efficiency mapping is proposed. An appropriate Lyapunov function is selected to prove that the control system ultimately tends to be bounded and stable, successfully solving the multiplicative nonlinear coupling control problem caused by the variable mechanism, and improving the system’s position control accuracy. Experimental results show that under this control method, the active load-sensitive drive system can reduce flow by up to 60 % compared to the traditional fixed displacement hydraulic motor drive system. Compared to conventional PID control, the proposed method can improve control accuracy by up to 50 %, effectively reducing energy consumption while improving the position control accuracy of the active load-sensitive variable motor drive system.

Hydraulic servo motors are widely used in aircraft utility systems due to their high-efficiency bidirectional variable displacement drive characteristics. However, the displacement changes process leads to severe friction losses between the swashplate and the bearing, and effective solutions are currently lacking. To address this issue, a Hydrodynamic Swashplate-Bearing Pair (HSBP) structure is proposed for hydraulic servo motors, which avoids the direct contact problem of traditional structures. A numerical calculation model for the HSBP is established, the axial displacement phenomenon generated during the reciprocating motion of the swash plate is considered, and a local mobility method is introduced to solve the frictional characteristic pa-rameters of the new friction pair. The analysis and calculation results obtained the influence law of different working condition parameters and structural parameters on the friction characteristics. A quasi-actual friction test bench is developed to simulate the actual motion characteristics of the swashplate, simplifying the testing method for the friction pair. The experimental results show an error of less than 10% compared to the calculated results. Additionally, the experimental results demonstrate that the proposed hydrodynamic swashplate bearing structure can effectively reduce the friction force during the displacement adjustment process of hydraulic servo motors by more than 90% compared to traditional swashplate bearing structures.

Load sensing pumps have been widely used in diverse hydraulic systems. Studies show that structural parameters have undeniable impacts on the characteristics and efficiency of the load sensing pump. The main purpose of this article is to study the influence of load sensing pump structure parameters on flow characteristics. In the present study, a nonlinear multi-parameter model is proposed for this type of pump. In this model, different parameters, including spool clearance, spool covering amount, internal leakage are considered to reflect the displacement adjustment process of the load sensing pump. Moreover, a frequency sweep method is proposed to analyze the frequency domain of the nonlinear mathematical model. An experiment rig was built to study the influence of key structural parameters on the dynamic follow-up characteristics of the pump flow. The obtained results show that the diameter of the orifice d can significantly affect the working characteristics of the pump. It is found that a large diameter of the orifice d can improve the phase following ability of the system, while a small diameter of the orifice d can reduce the bypass flow rate and increase the amplitude following ability. This paper provides a new consideration to study the dynamic follow-up characteristics of the load sensing pump.