To address the challenge of precise control in mechanical ventilation, this paper constructs a unified framework for positive and negative pressure and proposes an adaptive gain-negative pressure collaborative control method. This strategy adaptively adjusts control gains based on flow rate and lung elastance, while treating negative pressure as a load for feedforward compensation. Simulation data indicate that, compared to the 8~9 L/min peak flow oscillations caused by fixed-parameter PI control, the proposed method stabilizes the inspiratory flow peak within 6~8 L/min and yields smooth waveforms. The results confirm that this method significantly reduces pressure tracking errors under various working conditions and decreases driving pressure while guaranteeing tidal volume, providing an intelligent control approach for aviation and medical respiratory support.

In order to gain a deeper understanding of the causes of head erosion, pressure signal, rotor torque and stator-rotor gap and flow rate of shear valve slurry positive pulse generator in the working process, this paper takes the complete structure of a certain type of pulse generator as a simulation object, considers the non-Newtonian nature of the slurry fluid and its influence on the flow field, and solves the flow field under different working conditions through numerical simulation methods. The results show that the turbulence and reflux phenomenon near the stator and rotor are the main reasons for the erosion of the rotor and its neighboring parts; the pressure and rotor torque increase when the flow rate increases, and the pressure and rotor torque decrease when the gap between the stator and rotor increases. This study provides and verifies the reliability of the original data of this pulser, improves the efficiency and performance of the mud positive pulse generator by providing an effective means of simulation and analysis, and provides a reference for the design and optimization of the mud pulse generator under different working conditions.

The dynamic performance of the pressure regulation system in hydraulic-driven high-pressure water pumps directly affects cleaning quality and efficiency. This paper constructs a digital simulation model of the pilot-operated relief valve pressure regulation system based on the power bond graph theory, and its validity is verified through experiments. The study focuses on the dynamic response characteristics of the system under step pressure conditions. Through numerical simulations, the effects of parameters such as valve spool structure, spring stiffness, and hydraulic damping on the system's overshoot, pressure stability, and response speed are analyzed. By optimizing the valve overlap and the diameter of the damping orifice in the pilot valve seat, the system's inlet pressure overshoot was reduced from 90% to approximately 75%, while also improving the pilot valve's dynamic displacement process and the overall stability of the system.

Aiming at the shortcomings of poor stability, difficult quality assurance and time-consuming connection of steel bar binding and welding connection in large bridges, high-rise buildings and steel structures, a high-neutral hydraulic steel bar sleeve extrusion connection equipment is designed. Through theoretical calculation and engineering experience, the size of each key part is determined. Based on Workbench software, the static analysis of the whole equipment at the beginning and end of extrusion is carried out. The simulation results show that the structural strength and stiffness meet the design requirements. Then the prototype of the equipment is processed, and the tensile test of No.32 steel bar after extrusion connection is carried out. The results show that the sleeve is well connected. Finally, it is preliminarily applied in a construction site. The designed hydraulic steel sleeve extrusion connection equipment can quickly and efficiently complete the steel bar connection and the joint quality is good, which provides a reference for the development of other types of steel bar extrusion connection equipment.

To achieve high-frequency driving of a discrete coil magnetostrictive direct drive valve, an eight channel switch type constant current power driver was designed based on SPWM modulation principle, and its mathematical model was established. The output characteristics of the power driver when driving a single coil were analyzed using the mathematical model. Process a prototype and build an experimental system for experimental research. The experimental results show that the frequency response of the power driver can reach 2072 Hz when driven by a single coil. When driven by multiple coils, the output capability decreases due to the induced current between the coils, but the driving frequency response still exceeds 550 Hz. When using this power driver to drive a discrete coil magnetostrictive direct drive valve for pressure regulation, it can achieve oscillation pressure regulation of 200 Hz and 0.66 MPa at an oil supply pressure of 2 MPa and an average flow rate of 2 L/min.

This study evaluates wave-atmosphere coupling effects on offshore wind farm performance through numerical simulations using the WRF-WFP and WRF-WFP-SWAN models. Focusing on a 6×10 array of 8 MW turbines in Bohai Bay, we systematically analyze how wave coupling influences atmospheric boundary layer dynamics, wake characteristics, and power generation. The results demonstrate that SWAN wave coupling enhances surface roughness, significantly altering wind load distribution patterns. The coupled simulations reveal consistent improvements in wake recovery, with velocity deficits reduced by 11~21.7% and wake lengths shortened by 39.1~48.9% across all operational heights. However, the wave coupling shows detrimental effects on energy production, causing an 8.8% decrease in total power output and a 7.1% reduction in overall farm efficiency. These findings provide critical evidence that conventional single-model approaches tend to overestimate actual wind farm performance by neglecting wave-atmosphere interactions. The study underscores the necessity of incorporating coupled modeling techniques for accurate offshore wind resource assessment and farm optimization.

pVTt gas flow standard has been widely employed due to its simple structure and high accuracy, but the traditional 2-way inlet valve will lead to the interruption of critical flow during the opening and closing process, which significantly reduces the uncertainty of the device. In this paper, a hydraulically driven fast-switching three-way valve is proposed, which can realize the dynamic start and stop of continuous critical flow of nozzles working together with a negative pressure buffer tank. To analyze the flow characteristics of the switching process, a flow field simulation model of the three-way valve was established, and the flow field was calculated by using the moving grid method, and the gas flow characteristics with different switching speeds were obtained. The results show that the proposed fast-switching three-way valve can achieve the expected dynamic start-stop effect

In a five-axis simultaneous numerical control (NC) machining center, the hydraulic pallet lifting system is influenced by a multitude of factors, leading to a complex control system where multi-factor coupling makes it challenging to identify key factors for compensation. This results in a control process that is overly intricate and lacks dynamic responsiveness. To address this, a servo control method for the hydraulic pallet lifting system in a five-axis simultaneous NC machining center is proposed. The Random Forest (RF) algorithm is utilized to intelligently identify and reduce the multiple factors affecting the lifting performance of the hydraulic pallet, selecting key factors that significantly influence the system's performance from numerous candidates. This simplifies the input of control factors and mitigates the mutual coupling effects of multiple factors. A hybrid control strategy combining Internal Model Control (IMC) and Proportion-Integration-Differentiation (PID) control is employed, leveraging IMC's predictive capabilities and PID's rapid response characteristics to analyze control factors. This effectively enhances the lifting system's adaptability to dynamic changes and its anti-disturbance capability. To further optimize the parameters of the PID controller, the Dandelion Algorithm (DA) is introduced for global optimization, leveraging intelligent search algorithms to find the optimal PID parameter combination, thereby further improving the stability and accuracy of the control. Experimental results demonstrate that the proposed method effectively enhances the control efficiency, stability, and accuracy of the hydraulic pallet lifting servo system.

Due to the strong coupling characteristics between the mechanical and hydraulic systems in the hydraulic driven six axis robot system, as well as the significant nonlinearity of the flow pressure relationship of the hydraulic actuator, traditional dynamic modeling methods based on decoupling assumptions are difficult to accurately describe the dynamic characteristics of the system. This modeling error will be transmitted to the end effector through joint drive, increasing overshoot and causing a decrease in position control accuracy. Therefore, a high-precision position control method for a hydraulic driven six axis robot based on incremental nonlinear inverse control is proposed. Construct a robot joint dynamics equation that includes the coupling characteristics of mechanical and hydraulic systems through Lagrange equations, and establish a complete hydraulic drive dynamics model by combining the physical relationships such as flow rate and pressure of hydraulic actuators; Adopting an incremental nonlinear inverse control method, the nonlinear characteristics of the system are accurately compensated through a dynamic inverse model, and the mechanical hydraulic strong coupling problem is solved by combining incremental iteration strategy, ultimately achieving high-precision control of the end effector position. Through experiments, it is known that the displacement of the hydraulic system piston and the robot speed under this method have a small difference from the expected values. When there is no interference, the rise time is 0.8 seconds, the adjustment time is 2.5 seconds, the overshoot is 5%, and the response is fast and stable; When there is interference, the rise time is 1.2 seconds, the adjustment time is 3.0 seconds, and the overshoot is 8%. In the presence or absence of interference, this method can quickly and stably control the output, with excellent dynamic stability and high control accuracy.

The landing gear retraction control solenoid valve is a key component that affects the retraction time of the landing gear. In order to analyze the influence of the solenoid valve key parameters on the retraction time of the landing gear, a model of a dual redundant solenoid valve was established by combining the modeling advantages of finite element method and AMESim, and the accuracy of the model was verified through experiments. Based on the established dual redundant solenoid valve model, the influences of electromagnetic force, throttle hole size of main control valve, and oil viscosity on landing gear retraction time are analyzed, which provide theoretical basis for the development of the control solenoid valve.

The thermal decomposition behavior of flexible graphite at different heating rates were studied by the non-isothermal thermogravimetric method. Thermal decomposition kinetics parameters of flexible graphite were calculated by Kissinger method, Flynn-Wall-Ozawa method and Coats-Redfern method. The results reveal that the thermal decomposition activation energy (E) is 189.78 kJ/mol, and pre-exponential factor (lgA) is 6.75 min^-1. The reaction mechanism of flexible graphite thermal decomposition is a second order reaction, and corresponding kinetics differential equation is obtained. 1% thermal loss is used as the failure threshold for flexible graphite by the leakage detection. Furthermore, a prediction model of flexible graphite service life is established based on above kinetic equation.

To address the water hammer issue in the closing process of axial-flow check valves, the Fluent dynamic mesh technique was utilized to investigate the valve closing dynamics. By optimizing the valve disc profile and structural parameters of the internal flow channel, the valve's resistance to water hammer was enhanced. Different structural parameters were selected for orthogonal experiments, and multivariate linear regression analysis identified the primary structural parameters affecting water hammer resistance, which were then chosen as optimization targets. A Gaussian Process Regression (GPR) surrogate model was constructed, followed by multi-objective optimization using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), resulting in Pareto front solutions. The structural parameters providing optimal water hammer resistance were determined as follows: valve disc fullness coefficient α₁ of 0.696 13 and flow-hole radius R of 6.9 mm. Compared to the unoptimized axial-flow check valve, water hammer resistance improved by 14.37%, while the valve reaction speed during closure decreased by only 1.13%.

In the lifting condition of long-span and high-load bridges, it is very easy to generate eccentric loads, and the lifting system further reduces the synchronous lifting accuracy due to the interaction of multiple cylinders. Therefore, an adjacent cross-coupling synchronous scheme and an anti-eccentric load sliding mode control strategy were designed. The strategies were verified through simulation programs and a four-cylinder lifting test rig. The test results show that the maximum tracking error under sliding mode control is an average of 0.789 mm, and the multi-cylinder synchronous accuracy can be maintained within 0.2 mm after combining the adjacent cross-coupling synchronous scheme. This provides a feasible solution for the synchronous control strategy of multi-cylinder bridge lifting systems.

The hydraulic drive of the coal mine inclined shaft steel mold trolley is subject to frequent load changes and uncertain parameters such as friction resistance. The current control process tolerates this interference, resulting in problems such as poor control accuracy and insufficient stability. To solve this problem, research on hydraulic drive control method of coal mine inclined shaft steel mold trolley based on disturbance observer is carried out. Firstly, analyze the overall structure of the coal mine inclined shaft steel formwork trolley and describe the operating status of the hydraulic system of the steel formwork trolley. Then, based on this, a hydraulic drive control method is designed that integrates a disturbance observer and a backstepping control strategy. The disturbance observer observes various unknown disturbances received by the hydraulic system in real time, and finally inputs the observed results into the backstepping controller. Through the compensation of the backstepping controller, the hydraulic drive control of the coal mine inclined shaft steel mold trolley is achieved. Simulation experiment analysis shows that the application of interference observers can effectively observe different types of interference signals in hydraulic systems. When the input signals of the hydraulic system are sine signals, step signals, and ramp signals, this method can achieve precise control of the output, thereby effectively ensuring the stability of the hydraulic system.

The hydraulic power source with variable displacement and variable speed control has advantages. However, this architecture poses a great challenge for system control. In this paper, a pressure/flow pump-controlled system with novel control strategy based on variable displacement and adaptive speed control is proposed. The control strategy includes an adaptive speed controller based on optimum swivel angle control, as well as p/Q controllers in parallel structure that considers the influence of variable speed. Through the control strategy, system pressure and flow are dynamically controlled; meanwhile, the output characteristics of the drive system can be adjusted to match the high-level efficiency in steady state under various load conditions. The experimental tests are carried out to validate the control performance and energy efficiency. The results show that the control strategy of adaptive speed control can work effectively according to optimum matching rule, and the dynamic flow step response from 0 to 250 L/min is 108 ms. Compared with pure variable displacement concept and pure variable speed concept, the power consumption under the pressure holding and partial load conditions can be significantly reduced. Compared with pure variable displacement concept, the energy saving ratio in pressure holding mode is 54%~80%, the maximum energy efficiency improvement under partial load condition is 23.1%. Compared with pure speed control, the maximum energy saving ratio in pressure holding mode is 39%, the maximum energy efficiency improvement under partial load condition is 15.2%.

In recent years, with the continuous growth of the demand for petroleum energy, great changes have taken place in the petroleum enterprises, and the related machinery and equipment are constantly updated and improved. Reciprocating compressor, as an essential equipment in petrochemical enterprises, most of its faults occur on the crankshaft seal. Based on this, this article for reciprocating compressor crankshaft seal failure phenomenon and causes were analyzed. The study found that crankshaft wear, O-ring aging and fracture are the causes of the aging of the equipment. Therefore, the O-ring drive is changed to the top wire drive, and the O-ring material is replaced. It is verified by operation that these measures effectively reduce the failure rate of crankshaft mechanical seal and ensure the long-term stable operation of reciprocating compressor.

This study addresses the difficulty of starting the APU at high altitudes by examining its start control system. We analyzed and checked the ignition, fuel supply, and fuel control systems during startup, ultimately tracing the issue to the startup fuel control system. By comparing data from successful low-temperature starts in flight, we determined that the main problem was insufficient fuel flow output by this system during high-altitude starts. To fix this, we improved the fuel supply by: increasing the fuel scaling factor in the ECB control algorithm during startup; the fuel reduction coefficient after the APU reaches high speed; adding autonomous fuel increase logic to prevent engine stall; introducing autonomous fuel reduction logic to respond to excessively high or rapid exhaust gas temperature rises. Based on high-altitude test results, the modified APU can now successfully start at altitudes up to 6,000 meters. Furthermore, data confirms that the fuel flow during successful in-flight starts at this altitude is significantly higher than in previous unsuccessful attempts.

By analyzing the material characteristics of XG720 cold-drawn tubes and considering the performance requirements of hydraulic cylinders for tube materials, the effects of different heat treatment parameters on the yield strength, impact toughness, and residual stress of the cold-drawn tubes were systematically investigated. The experiments revealed that annealing temperature is the most critical factor influencing the mechanical properties of XG720 cold-drawn tubes, followed by holding time, while heating time has the least impact. A regularity curve of heat treatment process for XG720 cold-drawn tubes was established. The optimal annealing process for comprehensive performance is 450 ℃ holding for 2-3 hours with a heating time of 2 hours. For individual performance optimization: the best process for yield strength is 420 ℃ holding for 2 hours; the optimal process for -20 ℃ impact energy is 500 ℃ holding for 2 hours; and the ideal process for elongation after fracture and residual stress reduction is 550 ℃ holding for 2 hours.