20 July 2026, Volume 50 Issue 7

    

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  Discussion on Future Development of Airborne Electromechanical Systems

  JIAO Zongxia

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 1-10. https://doi.org/10.11832/j.issn.1000-4858.2026.07.001

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  In March 2026, Academician JIAO Zongxia, a member of the Chinese Academy of Engineering, a professor at the School of Automation Science and Electrical Engineering at Beihang University, and a leading expert in airborne electromechanical systems and flight control systems, was invited to deliver a distinguished presentation titled“Discussion on Future Development of Airborne Electromechanical Systems” at the 14th National Conference on Fluid Power Transmission and Control held in Wuhan, Hubei Province. The report begins with an overview of aircraft composition and the positioning of airborne systems, highlighting the core role of electromechanical systems in aircraft energy flow, actuation and support functions. It then focuses on three major technological threads of high-temperature and high-pressure hydraulics, multi-electrification and intelligence, and analyzes the new requirements imposed by next-generation aviation platforms on power density, reliability, maintainability and intelligent control capabilities. Finally, from the perspective of the integration of “energy-information-control”, the report offers forward-looking insights into the development trends of airborne systems in the contexts of green aviation, unmanned operations, swarm cooperation, and extreme-environment applications. The following text has been transcribed and edited from Academician JIAO's lecture.
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  Intelligent Pneumatic Radial-artery Hemostasis Device Based on Multisource Information Fusion

  LIU Guoqing

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 22-29. https://doi.org/10.11832/j.issn.1000-4858.2026.07.003

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  After transradial intervention, real-time monitoring of puncture-site bleeding is difficult. Conventional hemostasis relies on operator experience, and the compression force is hard to quantify. Complication detection is delayed, and patient comfort is difficult to ensure. To address these problems, an intelligent pneumatic radial-artery hemostasis device based on multisource information fusion is designed. The system builds a basic pressure-feedback loop using an intracuff pressure sensor, and achieves precise pneumatic regulation through an air pump and solenoid valves. Bioimpedance, photoplethysmography, and electrodermal activity sensing are further integrated to quantify bleeding in real time, monitor distal perfusion, and assess the patient's pain and stress level, respectively. On this basis, an intelligent closed-loop control strategy is formed that balances hemostatic safety, distal blood supply, and patient comfort. Experiments show that the device ensures reliable hemostasis while achieving precise pressure regulation and multisource signal acquisition. It improves patient comfort and reduces complication risks, and provides a feasible solution for intelligent and multi-objective coordinated hemostasis management after interventional procedures.
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  Flow Field Regulation and Enhanced Lubrication and Heat Dissipation Capability Analysis of Oil Guide Shrouds in Commercial Vehicle Gearboxes Transmission

  CHAI Bosen

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 30-37. https://doi.org/10.11832/j.issn.1000-4858.2026.07.004

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  Inadequate lubrication and insufficient heat dissipation cause performance degradation in heavy-duty commercial vehicle gearboxes. To solve this, an oil guide shroud with spatial confinement and pumping effect is designed. This design uses an interactive approach combining CFD simulations and flow visualization experiments. The study investigates the regulatory mechanism of the shroud on the flow field structure and its efficacy in forced lubrication and heat dissipation in the high-temperature meshing zone under various speeds. The results show that the shroud achieves directional oil regulation and resolves high-speed oil starvation. Compared to the unshrouded baseline, the oil volume fractions in the meshing zones of the driving and driven helical gears increase by approximately 417% and 367%, respectively. Spatial confinement suppresses chaotic oil splashing. This yields a maximum reduction of 17.5% in system churning torque across the speed range and minimizes power loss. The shroud enhances convective heat transfer in the high-heat zone. The average convective heat transfer coefficients of the driving and driven helical gears increase by 41.8% and 24.1%, respectively. The oil guide shroud effectively optimizes spatial oil distribution and enhances thermal-lubrication performance. It provides a technical reference for improving the thermal equilibrium of transmission systems.
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  Analysis and Optimization Design of Pressure Drop Characteristics of Proportional Pressure Relief Valve

  ZHANG Kepeng

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 38-46. https://doi.org/10.11832/j.issn.1000-4858.2026.07.005

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  As a critical component for fluid control in hydraulic systems, the proportional pressure relief valve plays a pivotal role in dynamic regulation. Investigating and optimizing its pressure drop characteristics are significant for improving system control accuracy and energy efficiency. We focus on a specific proportional relief valve. A simulation model is established using AMESim to analyze pressure drop characteristics. A multi-parameter collaborative optimization method based on experimental design and response surface methodology is proposed to balance valve port pressure drop and dynamic response. Results indicate that damping orifice diameter is the dominant factor affecting pressure drop. Reducing the diameter from 0.5 mm to 0.2 mm decreases the minimum pressure drop by 39.8%, while the maximum pressure drop changes slightly. Response surface model validation shows low sensitivity of pressure drop to half-cone angle and spring stiffness. This method effectively resolves the conflict between "low pressure drop" and "fast response" in traditional designs, providing a theoretical basis for developing high-performance proportional pressure relief valves.
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  Study on Fuzzy PID Pressure Control of Electric High-pressure Air Pressure-reducing Valve

  HUANG Hejie, ZHAO Zhixin, LI Jiacheng, GAO Longlong, LI Baoren

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 47-56. https://doi.org/10.11832/j.issn.1000-4858.2026.07.006

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  The electric high-pressure air pressure-reducing valve is a key component in high-pressure pneumatic systems, and its control accuracy and dynamic response directly affect system safety and stability. To address non-ideal gas behavior under high-pressure conditions, strong nonlinearity in pressure regulation, and the limited performance of conventional PID control over a wide outlet pressure range, a real-gas-based mathematical model is established and a fuzzy PID pressure control strategy is proposed. Simulations at outlet pressures of 5,15 and 25 MPa are conducted on a Simulink platform and compared with conventional PID control. The dynamic response characteristics under different operating conditions are systematically analyzed. Results show that the proposed method achieves shorter response time and effectively suppresses overshoot under low-pressure conditions. Experiments at an inlet pressure of 40 MPa agree well with simulations, demonstrating good dynamic regulation performance over the outlet pressure range of 0~25 MPa.
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  Analysis of Overpressure Phenomenon in Primary Buffer Chamber of Dual-chamber-controlled Hydraulic Rock Drill

  WANG Jiansen

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 57-67. https://doi.org/10.11832/j.issn.1000-4858.2026.07.007

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  During the prototype test of a dual-chamber-controlled hydraulic rock drill, an overpressure issue is observed in the primary buffer chamber pressure during the impact process. To investigate this, a mathematical model of the rock drill's damping system is established, along with a corresponding graphical simulation model in AMESim. Based on the measured structural parameters of the buffer, simulation is employed to reproduce this fault phenomenon. Analysis reveals that the fault is caused by machining errors in the return oil port of the primary buffer chamber, which reduces the pre-opening flow area of the return throttle. This leads to an increase in the gas spring stiffness of the buffer chamber accumulator, causing the buffer piston's damping behavior to transition to a hard spring, short-stroke, high-damping operating mode. The influence of axial positioning errors and angular positioning errors of the return oil passage on the gas spring stiffness and the pressure in the primary buffer chamber is discussed. It is found that the axial positioning error has a more sensitive effect. Considering the convenience and economic feasibility of the actual manufacturing process, it is recommended that the tolerances for the axial positioning and angular positioning of the return oil passage are set at ±0.2 mm and ±1°, respectively.
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  Effect of Spring Characteristics on Sealing Performance of Spring-energized Seals Under Low-pressure Conditions

  LI Jing

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 68-79. https://doi.org/10.11832/j.issn.1000-4858.2026.07.008

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  To study the influence of helical spring characteristics on the sealing performance of spring-energized sealing rings under normal temperature and low-temperature low-pressure conditions, a three-dimensional cyclic symmetrical structure finite element model of such sealing ring is established. The influences of the presence of spring, as well as spring installation interference, structural stiffness, installation position and material on the sealing performance of sealing rings under low-pressure conditions of 20 ℃ and -100 ℃ are systematically studied. The results show that the energy storage spring plays a key role in sealing under low-pressure, especially zero pressure conditions. At 20 ℃ and zero pressure, when there is a spring, the maximum contact stress of the inner lip is approximately 11.0 MPa, and it is only 2.1 MPa without a spring. At -100 ℃, when there is no spring, the contact stress of the outer lip drops to 0.4 MPa, causing the seal to fail, when there is a spring, it can still maintain an effective seal at 1.1 MPa. The installation interference has a significant impact on the contact force. The greater the spring stiffness, the wider the range of interference available. The two installation forms have no significant impact on the sealing performance. With the increase of radial stiffness, the contact stress at the lip of the polytetrafluoroethylene sheath shows an increasing trend. Under the working conditions of -100 ℃ and 0.1 MPa, the contact stress of the inner and outer lips of the 3J21 elastic alloy spring is approximately 67% and 134% higher than that of the 304 stainless steel spring respectively, and its leakage suppression effect on the outer sealing surface is particularly significant.
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  Research on Compatibility of Carbon-based Lubricating Films on Surface of Port Pair in High-pressure Piston Pump

  YANG Xian

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 80-89. https://doi.org/10.11832/j.issn.1000-4858.2026.07.009

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  The port pair serves as the key friction pair with the largest contact area in a piston pump, and its performance directly governs the efficiency, lifespan, and reliability of the entire pump. During operation, the port pair endures not only high-speed friction and high-pressure loads, but also periodic impacts from relative motion, which often leads to wear and overheating issues. Diamond-like carbon films, possessing excellent lubrication performance and high chemical stability, offer great application potential under the complex working conditions and within the liquid working media typical of piston pumps. We focus on the commonly used Cr12MoV material for the port pair. We first treat the material with surface nitriding, hardening, and tempering. Then, we deposit two types of diamond-like carbon films onto its surface. Our research evaluates the performance of these films and their tribological behavior in a 15# hydraulic oil environment. The results indicate that the diamond-like carbon films exhibit good wettability in hydraulic oil. The lubricating diamond-like carbon film demonstrates good compatibility with all three substrates. As the film hardness increases, the friction coefficient does not rise significantly compared to the substrate material, and the wear rate drops by more than 98%. In contrast, the wear-resistant diamond-like carbon film, with its excessively high hardness, tends to aggravate the wear of the counter face. However, its compatibility with the nitrided substrate surface unexpectedly proves favorable.
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  Research on Vibration Amplitude of Civil Aircraft Pipelines Based on Beam Theory

  NIU Wenliang

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 101-108. https://doi.org/10.11832/j.issn.1000-4858.2026.07.011

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  Aircraft internal systems contain numerous pipelines. The determination of installation clearance is critical for both efficient space utilization and operational safety. We investigate a typical straight pipe with both ends fixed. Based on the "fixed-fixed beam" theory, the vibration amplitude is analyzed and the surface strain distribution is obtained. An experimental setup is developed to measure the vibration amplitude, using strain gauges for data acquisition. A fluid-structure interaction model of the pipeline is established, and the results are compared with theoretical predictions and experimental measurements. The results show good agreement among theory, simulation, and experiment, which validates the effectiveness of the vibration amplitude analysis method based on "fixed-fixed beam" theory. This method provides a reliable basis for vibration amplitude prediction and engineering parameter fitting. It also helps define the parameter boundaries of installation clearance for hydraulic pipelines and supports the determination of process windows.
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  Research on Self-excited Oscillation Mechanism and Inverse Compensation Control for Valve-controlled Hydraulic Servo Systems

  LI Jinyuan

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 109-118. https://doi.org/10.11832/j.issn.1000-4858.2026.07.012

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  Electro-hydraulic servo systems employ servo valves to regulate hydraulic motors for high-precision motion. Motion smoothness directly determines control accuracy and system reliability. However, inherent nonlinearities, including dead zone, backlash, and saturation, frequently induce undesirable oscillation. Such oscillation degrades positioning accuracy, deteriorates control quality, and shortens equipment lifespan. To reveal the underlying oscillation mechanism, we establish a linearized model of the servo valve-hydraulic motor system and applies the describing function method to analyze the nonlinear elements. The results identify backlash as the dominant source of self-excited oscillation. Accordingly, a backlash inverse compensator based on the describing function model is proposed to actively suppress this nonlinearity through feedforward compensation, achieving inverse compensation. Simulation results demonstrate that the proposed closed-loop strategy effectively suppresses self-excited oscillation, significantly improving drive smoothness and control accuracy.
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  Barrier Lyapunov Function-based Fractional-order Backstepping Adaptive Control for Electrohydraulic Servo Systems

  ZHENG Xinyang, SUN Chungeng, SUN Zeyu

  CHINESE HYDRAULICS & PNEUMATICS. 2026, 50(7): 119-128. https://doi.org/10.11832/j.issn.1000-4858.2026.07.013

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  To address the strong nonlinearity of electro-hydraulic servo systems, as well as the degradation in tracking accuracy and stability caused by parameter perturbations and position disturbances—where position, velocity, and acceleration must be strictly constrained to ensure safe system operation,a composite control solution based on subsystem error-constrained time-varying tangent barrier Lyapunov functions and fractional-order backstepping adaptive control is proposed. A fractional-order control law is derived from the system dynamics equations, and stability is verified using the time-varying barrier Lyapunov theory with an adaptive component. Simulation results show that the proposed method reduces the average displacement tracking error by 94.8%~99.7% compared to fractional-order PID, by 40.9%~87.6% compared to fractional-order backstepping control, and by 79.7%~96.1% compared to fractional-order sliding mode control. Furthermore, compared to fractional-order backstepping sliding mode control, this method effectively suppresses amplitude overshoot and chattering, while improving the robustness of the controller.