The study investigates the impact of textured surface parameters and pump operating parameters on the friction performance of slipper pairs in axial piston pumps. The orthogonal experimental scheme was developed, and the influence of several factors was explored, such as rotational speed, area ratio, micro-pit shape, diameter, depth-to-diameter ratio and film thickness. Optimal dimension combinations of the micro-pit were identified by numerical simulation and standard pin–disk friction experiment. In the pin–disk friction pair test, the friction coefficient of the textured surface compared to the smooth surface showed a maximum average friction reduction rate of 26.974%. Under various pump pressures (4, 8, 12 MPa) and pump displacements (10, 20, 35 L/min), the friction reduction rates of the textured surface slipper pairs (texture diameter 500 µm, depth 250 µm, area ratio 20%) ranged from 0.78% to 18.13%. The study underscores the importance of surface texture in enhancing the operational efficiency and reliability of axial piston pumps, offering valuable insights for the design and maintenance of hydraulic pumps.

The film temperature distribution of the valve plate pair in axial piston pumps affects its lubrication, leakage, and friction. In order to investigate the film temperature distribution of the valve plate pair in axial piston pumps, a test platform was constructed including three displacement sensors for the oil film thickness and eleven thermocouples for the film temperature distribution of the valve plate pair. An accurate film shape model of the valve plate pair was built according to the three-point film thickness test data. Based on the film shape model, the film temperature model of the valve plate pair was developed considering the viscous oil temperature characteristics, the energy loss caused by leakage and viscous friction in the film, and the heat conduction among the oil, cylinder block, and valve plate. The influence of different swash plate tilt angles and operating pressures on the valve plate film temperature was studied. The test results indicate that the film temperature of the valve plate pair increases as the working pressure and swash plate tilt angle increase. The theoretical and experimental absolute errors of the film temperature in the circumferential range [−60°, 60°] of the valve plate high-pressure side are less than 3.5 °C. As the swash plate tilt angle varies from 12° to 16° and working pressure from 3 MPa to 7 MPa, the minimum film thickness position and the maximum temperature point move accordingly in the circumferential range [−15°, 5°] of the valve plate pair.

The electro-hydraulic power source with an electro-hydraulic variable pump driven by a servo motor is suitable for electrified construction machinery. To achieve better energy efficiency in different working conditions, the multi-mode control scheme was proposed for the electro-hydraulic power source. The control scheme includes pressure control, flow control, and torque control modes. The switching rule among the three control modes was formulated based on the minimum pump pressure. The fuzzy PID controller was designed, and a composite flow regulation strategy was formulated, including the load-sensitive adaptive displacement regulation and servo motor variable speed regulation. The AMESim-Simulink co-simulation model of multi-mode control was established. The test platform was built, and the experimental study was carried out. The results indicate that the fuzzy PID control has a shorter response time and a more stable control effect compared with PID control. Additionally, the composite flow regulation strategy improves the flow regulation range by 36% and reduces the flow overshoot by 20% compared with the load-sensitive adaptive displacement regulation. As the main control valve received an opening step signal, the full flow regulation (7~81 L/min) of the power source took approximately 0.5 s to rise and 0.2 s to fall. The relative error of pressure difference for the main control valve was 0.63%. When receiving the pressure and torque step signal, the pump pressure and pump input torque both took approximately 0.45 s to rise and 0.2 s to fall. The relative errors of pump pressure and torque control were 0.2% and 0.16%, respectively. In the multi-mode control, the electro-hydraulic power source could switch smoothly between flow control mode, pressure control mode, and torque control mode. These results provide a reference for the multi-mode control of an electro-hydraulic power source with an electro-hydraulic variable pump driven by a servo motor.