Swash Plate Research Articles

Output speed control for hydro-mechanical continuously variable transmission of tractor.

In order to improve the speed stability of tractors equipped with hydro-mechanical continuously variable transmission (HMCVT) during field operations, the speed regulation characteristics, torque characteristics, and power diversion characteristics of HMCVT are analyzed. And a comprehensive control strategy for HMCVT output speed is proposed by analyzing the factors affecting the fluctuation of output speed, which combines engine speed control and displacement ratio control of hydraulic speed control system. This strategy adopts fuzzy control to regulate the engine speed to maintain the stability of engine operation. Moreover, adopting feed forward compensation control for speed compensation enhances the anti-interference ability of the hydraulic speed control system. And combined with model predictive control, adjust the swash plate swing angle of the variable pump to reduce the fluctuation of HMCVT output speed. By establishing joint simulation model, the effectiveness of the control strategy was verified using tractor acceleration mode and step load disturbance mode. The results show that the strategy can reduce the fluctuation rate of engine speed and impact degree, shorten the adjustment time, and improve the stability of tractor operating speed.

Comparison of Advanced Multivariable Control Techniques for Axial-Piston Pump

This article is devoted to a comparison of two advanced control techniques applied to the same plant. The plant is a certain type of axial-piston pump. A linear-quadratic (LQR) controller and an H-infinity (H∞) controller were synthesized to regulate the displacement volume of the pump. The classical solution to such a problem is to use a hydro-mechanical controller (by pressure, flow rate, or power) but, in the available sources, there are solutions that implement proportional-integral-derivative (PID), LQR, model predictive control (MPC), etc. Unlike a classical solution, in our case, the hydro-mechanical controller is replaced by an electro-hydraulic proportional valve, which receives a reference signal from an industrial microcontroller. It is used as the actuator of the pump swash plate. The pump swash plate swivel angle determines the displacement volume, respectively, and the flow rate of the pump. The microcontroller is capable of embedding various control algorithms with different structures and complexities. The developed LQR and H∞ controllers are compared in the simulation and real experiment conditions. For this purpose, the authors have developed a laboratory experimental test bench, enabling a real-time function of the control system via USB/CAN communication. Both controllers are compared under different pump loading modes. Also, this paper contributes an uncertain model of an axial-piston pump with proportional valve control that is obtained from experimental data. Based on this model, the robust stability of the closed-loop system is investigated by comparing the structure of a singular value (μ). The investigations show that both control systems achieved robust stability. Moreover, they can tolerate up to four times larger uncertainties than modeled ones. The system with the H∞ controller attenuates approximately at least 30 times the disturbances with frequency up to 1 rad/s while the system with the LQR controller attenuates at least 10 times the same disturbances.

Incremental fully actuated system approach-based prescribed-time fault-tolerant formation control of helicopters under multiple faults

Helicopter formation is characterized by intricate dynamics, complex mechanics, and challenging scenarios, raising the necessity for agile, robust, and convenient controller design. This paper explores the prescribed-time fault-tolerant formation control of multiple helicopters through the incremental fully actuated system approach, which addresses multiple faults in sensors and swash plate struts. First, the helicopter model encompassing aerodynamic, flapping dynamic, swash plate dynamic, actuator faults, and sensor faults is established and further partitioned into attitude and position subsystems. Then, in the attitude subsystem, a prescribed-time attitude controller based on the incremental fully actuated system approach is proposed to track the desired attitude with robustness against actuator faults, aerodynamic drags, inter-axis coupling, and non-linearity. Next, in the position subsystem, the faults of velocity and position sensors are estimated and compensated through the prescribed-time fault-estimation observer, and a prescribed-time formation controller through the incremental fully actuated system approach is designed to achieve distributed leader-follower formation control. A Task-Fault dual-driven scheduling mechanism of the parameters of the prescribed-time technique is developed to promptly activate the prescribed-time function, and the control scheme is proven to be prescribed-time convergent via Lyapunov stability theory. Finally, numerical simulations are conducted to illustrate the efficiency of the algorithm.

Effects of the cross angle on output characteristics and tilting behaviour for 750 mL/r axial piston pumps

Large displacement axial piston pumps (>500 mL/r) are the core power components of large construction machineries' hydraulic system. The demand for higher power in large construction machinery is increasing. High pressure and large displacement are the primary areas of focus for enhancing the power of piston pumps. However, this may exacerbate issues with the pumps' output characteristics, such as flow or pressure pulsation and leakage. This paper uses a cross angle of the swash plate to optimize the pulsation and leakage for the 750 mL/r axial piston pumps. Piston and cylinder dynamics affect flow and pressure pulsations, and leakage is related to cylinder tilting behaviour. The pumps’ flow distribution, kinematics and dynamics of the piston and cylinder, output flow and pressure are analysed. A virtual prototype is built based on the rigid-flexible-hydraulic coupling model. The oil film flexible body of the valve plate pair is added. The maximum principal stress and strain of the oil film flexible body are used as indicators of tilting behaviour. Effects of the cross angle on output characteristics and tilting behaviour are investigated through the numerical solution. Results show that the cross angle of −0.5° can effectively reduce the pressure pulsation rate by 0.89% and the flow pulsation rate by 3.77% while optimizing the tilting behaviour of the cylinder. In addition, the cylinder’s tilting behaviour is verified by the wear detection on the valve plate surface.

A novel wear prediction method and wear characteristic analysis of piston/cylinder pair in axial piston pump

The wear of the piston/cylinder pair in the axial piston pump is a significant factor that adversely affects pump performance. To conduct a thorough investigation into the wear characteristics of the piston/cylinder pair, a dynamic model based on the equivalent load method is established. Then, a novel wear prediction method for the piston/cylinder pair is proposed by integrating the Archard wear model. The validity of the proposed method is confirmed through experimental verification. The results demonstrate that specific circumferential areas of the cylinder bore exhibit severe wear, and the distribution of these areas remains relatively stable over time. At the swash plate side, the most severe wear area along the circumference direction is concentrated in the range of approximately 200°–320°, which means the area that deviates from the extreme position in the radial direction of the pitch circle by a specific angle, with the deviation direction being opposite to the rotational speed. Conversely, at the valve plate side, the most severely worn circumferential area is situated in the range of about 0°–120°, which is opposite to the area at the swash plate side. The proposed wear prediction method offers improved computational efficiency, providing valuable support for analyzing the wear characteristics and failure mechanisms of piston pumps.

Effect of Structural Parameters on Output Characteristics of a Novel Self-Supplied Aviation Intelligent Pump

The aviation intelligent pump system is an effective solution to aircraft hydraulic systems’ inefficient power consumption and temperature increase. A self-supplied aviation intelligent pump (SAIP) has a high power-to-weight ratio and compact structure, making it the optimal choice for an intelligent pump. To analyze the output characteristics of a novel aviation intelligent pump, it is crucial to establish an accurate mathematical model that describes its dynamic characteristics. This can be achieved by analyzing the working principle and exploring the influence of critical parameters. The paper introduces the composition and working principle of a self-supplied electro-hydraulic servo variable displacement pump. It then establishes a mathematical model of the whole pump, with a detailed analysis and modeling of the critical variable mechanism and the swash plate assembly’s load moment. A simulation model was created to examine the impact of crucial structural parameters, such as the offset spring’s stiffness and control piston’s diameter, on the output characteristics of the intelligent pump. An experimental platform was also constructed, and the experimental results confirm the accuracy of the SAIP model presented in this paper. The investigation of the output characteristics fully reveals the dynamic performance of the SAIP. This provides the basis for the subsequent design of high-performance flow and pressure control strategies and aids in researching intelligent aircraft hydraulic systems.

Flow pulsation characteristics of variable displacement piston pump considering coupling effects cavitation bubble and swash plate inclination angle vibration

Variable-displacement piston pumps, in comparison with quantitative pumps, offer high volumetric efficiency, energy savings, and variable displacement advantages. The outlet flow pulsation of these pumps is influenced by several factors, including swash plate inclination angle vibration, cavitation bubbles, flow distribution structure, and valve control structure. This complexity poses challenges in accurately predicting the flow pulsation at the outlet of variable-displacement piston pumps. In response to this challenge, a novel outlet flow pulsation model for variable-displacement piston pumps is proposed, taking into account the coupling effects of cavitation bubbles and swash plate inclination angle vibration, building upon an existing model. Initially, the effects of cavitation bubbles and swash plate inclination vibrations on flow pulsation were analyzed. Subsequently, a comprehensive flow pulsation model for variable-displacement piston pumps was developed, considering the coupling effects of cavitation bubbles and swash plate inclination angle vibrations. This model was compared with three other existing flow pulsation models. The accuracy of the results was validated using a constructed test bench, with an accuracy improvement of approximately 12% compared to traditional theoretical models. Finally, an optimization model for outlet flow pulsation was proposed. The structural parameters of the valve plate, aimed at minimizing flow pulsation, were determined using the multi-agent particle swarm optimization algorithm. These findings underscore the importance of considering the coupled effects of cavitation bubble and swash plate inclination angle vibration in the design optimization process for reducing low-flow pulsation. This study provides a theoretical foundation for the design of variable-displacement piston pumps with minimized vibration and noise levels.

Noise Analysis and Optimization Design of an Electric–Mechanical–Hydraulic Power Coupler for the Vehicle

This article proposes a new electric–mechanical–hydraulic power coupler (EMHPC). The EMHPC is integrated by a swash plate axial piston pump and permanent magnet synchronous motor, which can realize the conversion of electric, mechanical, and hydraulic energy. To analyze the noise characteristics of the EMHPC, the mathematical models of fluid noise and electromagnetic noise are established, respectively. An optimization model is built based on Isight, and the multi‐island genetic algorithm is used to optimize the triangular groove structure. The optimization results show that the sound pressure level of sound field monitoring points decreases at different frequencies, and the vibration displacement of the cylinder block decreases. The maximum sound pressure level of the directivity curve of the radiated sound field decreases by 9 dB. For the electrodynamic structure optimization of the EMHPC, this article establishes a combination approximation model with higher accuracy. The structure of the stator and rotor is optimized based on the combined approximate model. The optimization results show that the sinusoidal property of the radial air‐gap magnetic density curve is better after optimization, and the harmonic amplitude of the radial electromagnetic force decreases. The maximum sound pressure level in the air domain of the external sound field is reduced from 69 to 60 dB. Moreover, the superposition analysis of fluid noise and electromagnetic noise is carried out, and the main noise sources of the EMHPC in different working modes are determined.

Optimization of swash plate multistage compressor based on dynamics

The swash plate compressor can provide high-pressure gas through multistage compression using its different cylinders, which is an ideal structure for high-pressure compressor miniaturization. The swash plate multistage compressor (SPMC) with variable sections cylinder and inter-stage cooler is proposed and its complex structure results in complex multi-body dynamics and thermodynamics. To research the dynamic characteristics of SPMC, the dynamic model of SPMC is established, which includes the thermodynamics of compression and inter-stage cooler and the dynamics of all the check valves and pistons. The optimization objective function considering the dynamic characteristics and efficiency is proposed. The constraint conditions and sensitivity of the optimized parameters are studied and the final parameters are achieved through an optimization algorithm. Based on the above work, it can be found that the optimization way has high convergence and accuracy, and the comprehensive performance of SPMC is improved significantly.

Failure analysis of non-rotating control rod of a helicopter

The paper presents findings of the failure analysis of a control rod that resulted in accident to a helicopter during a routine flight. The helicopter crashed due to several events that led to loss of control. Post-accident wreckage examination showed that failure in the non-rotating control rod connecting the swash plate and bell crank was the primary component that led to the accident. The control rod was manufactured from Ti-6Al-4V alloy. Fractography studies revealed that the control rod failed by fatigue mechanism. The fatigue crack initiated at the rod-to-eye-end transition fillet. Fatigue crack initiation was associated with presence of deep machining marks on the fillet surface. After initiation at the machining marks, the crack propagated through the thickness as well as along the machining mark over a length on either side of the crack origin. Study revealed presence of multiple fatigue cracks on the machining marks on the fillet surface. Analysis showed that the primary cause of the fatigue failure of the non-rotating control rod was the stress concentration effect arising from the deep machining marks at vulnerable location, which is the rod–to–eye transition fillet surface. Issues related to the fitment of the bearing in the control rod led to fretting on the inner bearing surface, and this damage contributed to the initiation of the fatigue cracks.

Experimental Tests of the Piston Axial Pump with Constant Pressure and Variable Flow

Constant pressure variable flow reciprocating axial pumps (CPAP) are used in various applications, where a constant output pressure is maintained when the flow rate changes. When the hydraulic system is at rated pressure or less, the swash plate has maximum tilt, and the pump delivers maximum flow. The swash plate comes into this position thanks to the action of a reactive piston in which there are two springs. However, when the pressure rises above the nominal pressure value, the piston of the hydraulic pressure transducer (HPT) distributes the fluid under pressure to the hydraulic cylinder (HC), which causes a decrease in the tilt angle of the swash plate and a decrease in flow. The CPAP was selected as a component of the hydraulic system of the aircraft for the experimental tests in this paper. The experimental tests covered the structural and working parameters of the pump and analyzed their performance, efficiency and reliability. Experimental tests of structural and operating parameters of the CPAP were carried out in the Laboratory for Hydraulics and Pneumatics “PPT-Namenska” Trstenik on the hydraulic system, which simulated the real conditions prevailing in the hydraulic system of the aircraft. A system was used for data acquisition and recording of pump characteristics, which were obtained during experimental testing. The results of the measurement and testing of the structural parameters of the CPAP are shown in tabular form, and the experimental tests of static characteristics and dynamic behavior are shown diagrammatically.

Lubrication characteristics of valve plate pair of balanced large flow pump based on elastic deformation

In this paper, the balanced large flow pump is taken as the research object. Considering the elastic deformation of the surface of the valve plate pair, the oil film dynamic model and the power loss model of valve plate pair are established, and the influence of different working conditions on the lubrication characteristics of valve plate pair is analyzed. The results show that the oil film parameters and performance parameters of valve plate pair change periodically. The power loss of valve plate pair is mainly viscous friction power loss, and the leakage power loss is small; considering the elastic deformation, the viscous friction power loss is reduced by 2.73 %–3.61 %, and the leakage power loss is increased by 21.8 %–25.3 %. The increase of working pressure and rotating speed will increase friction and leakage power loss. The increase of internal and external swash plate inclination will reduce the friction power loss and increase the leakage power loss. Compared with the traditional single-row axial piston pump, the viscous friction torque of the balance pump decreases and the leakage increases, but the total power loss decreases, which makes the balance pump more efficient than the traditional pump.

Study on the Lubricating Characteristics of the Oil Film of the Slipper Pair in a Large Displacement Piston Pump

Due to the large size of the bottom surface, the slipper pair of the large displacement piston pump (LDPP) will form a larger linear speed difference in the inner and outer positions of the slipper relative to the center of the swash plate during high-speed rotation. It is more likely to lead to the slipper overturning, which makes the slipper partially worn. To make improvements, the comprehensive performance of the slipper pair of the LDPP, the motion law of the slipper pair of the LDPP was explored. Firstly, a mathematical model of the oil film thickness of the slipper pair of the LDPP under the state of residual compression force is established, based on the consideration of the linear velocity difference formed by the high-speed rotation of the large bottom surface slipper and the theory of dynamics and thermodynamics. Secondly, the impact of rotational speed, piston chamber pressure and oil temperature on the oil film thickness of the slipper pair was simulated and analyzed. Finally, to measure the oil film thickness of the slipper pair, oil film thickness measuring equipment was created, and the accuracy of the mathematical model was verified. The study revealed the changing rules of the oil film thickness and tilt angle of the bottom surface of the slipper pair under various working conditions. The consistency of the simulation and test findings demonstrates that the mathematical model can accurately describe influencing elements and changing rules of the LDPP slipper pair’s oil film lubrication characteristics.

A Computation Fluid Dynamics Methodology for the Analysis of the Slipper–Swash Plate Dynamic Interaction in Axial Piston Pumps

This paper proposes a CFD methodology for the simulation of the slipper’s dynamics of a swash-plate axial piston unit under actual operating conditions. The study considers a typical slipper design, including a vented groove at the swash-plate interface. The dynamic fluid–body interaction (DFBI) model is exploited to find the instantaneous position of the slipper, while the morphing approach is adopted to cope with the corresponding mesh distortion. A modular approach is adopted to ensure high-quality mesh on the entire slipper surface and sliding interfaces provide the fluid dynamic connection between neighboring regions. The external forces acting on the slipper are included by means of user-defined lookup tables with the simulation estimating the lift force induced by fluid compression. Moreover, the force produced by the metal-to-metal contact between the slipper and the swash plate is modeled through a specific tool of the software. The pressure signal over an entire revolution of the pump is taken as an input of the simulation and a variable time step is used to manage the high-pressure gradients occurring in the regions of inner and outer dead points of the piston. The weakly compressible characteristic of the fluid is considered by a specific pressure-dependent density approach, and the two-equation eddy-viscosity k-ω SST (shear stress transport) model is used to assess the turbulent behavior of the flow. Furthermore, the transitional model predicts the onset of transition, thus solving different equations depending on whether the flow enters a laminar or turbulent regime. In conclusion, the proposed methodology investigates the motion of the slipper in response to several external forces acting on the component. The numerical results are discussed in terms of variable clearance height, pressure distribution within the gap, and lift forces acting on the slipper under specific pump operations.

The design of novel swash plate photocatalytic reactor with PAN/BiInOCl membrane photocatalyst for excellent RhB degradation

The low recovery efficiency and secondary pollution of traditional powder photocatalysts are the main problems restricting the practical application of photocatalysis technology. Therefore, PAN/BiInOCl membrane photocatalysts were prepared by simple electrospinning technology, and the swash plate photocatalytic reactor was designed according to the utilization characteristics of the membrane photocatalyst. By cooperating membrane photocatalyst with the swash plate photocatalytic reactor, the rapid and effective photocatalytic degradation of RhB simulated wastewater by PAN/BiInOCl membrane photocatalyst can be achieved, and the rapid and non-destructive recovery of photocatalysts can be realized. PAN/BiInOCl-3 membrane photocatalyst with the best photocatalytic degradation efficiency can realize the complete degradation of RhB within 30 min and has good stability under the actual sunlight irradiation. Radical trapping experiments confirmed that hydroxyl radicals and holes play a major role in the photocatalytic degradation of RhB. The preparation of PAN/BiInOCl membrane photocatalyst and the design of swash plate photocatalytic reactor lay a theoretical foundation for the design and preparation of efficient membrane photocatalyst and the application of photocatalytic technology in wastewater treatment.

An investigation into the micro-geometric tapered-shape surface design of the piston bore of a piston–cylinder interface in an axial piston motor

Abstract. In pursuit of design solutions that reduce energy loss and improve wear resistance for the piston–cylinder interface in an axial piston motor, a fluid-structure interaction numerical model and a new test rig of the friction force of the piston–cylinder pair are developed to achieve the analysis and design of the micro-geometric tapered-shape surface of a piston bore. The piston bore with the tapered-shape surface axial distribution length ratio of 49.44 % of the overall length is found to be the relatively optimized one. Furthermore, how the shaft speed, load pressure, and swash plate angle influence the performance of the two-type interface is analyzed. Numerical analysis results show that, compared with the traditional cylindrical piston bore design, the piston–cylinder interface with the optimized tapered-shape piston bore in the axial piston motor can achieve a significant reduction in leakage flow and friction force, and the experimental results are consistent with the simulation results.

Strength prediction and experimental damage investigations of plain woven CFRPs with interacting holes using multi‐instrument measurements

AbstractComposite structures with holes have been utilized in different applications, for example, swash plates, adaptor plates, and repair patches. These notches reduce the structural performance of the composite plates. In a woven composite plate with two interacting holes, the orientation of the holes affects the stress concentration factor (SCF) and strength of the laminate. The SCF determined by finite‐element method (FEM) shows that the structural performance of the sample with a single hole is improved through drilling one more hole along the loading direction. The main purpose of this article is to investigate, numerically and experimentally, the interaction between two holes, oriented at different angles, when the plate is subjected to tension. The location of the critical region depends on the configuration of the holes. The critical region and characteristic distances are established for each sample combining the FEM and digital image correlation (DIC) techniques. Point stress criterion (PSC) and extended‐PSC (EPSC) methods are utilized to predict the final failure strength of specimens. The failure progression under the influence of interaction between the two holes is investigated by infrared thermography (IRT). Moreover, to complement the IRT and mechanical results, fractographic analysis is conducted and it is concluded that a delamination dominated fracture along loading direction takes place in samples with two holes while a transversal matrix dominated failure is observed for the single notch specimen.

ANALISIS KINEMATIK MANUVER TERBANG VERTIKAL PADA KOMPONEN SWASH PLATE, ROTOR HEAD DAN ROTOR BLADES HELIKOPTER SEJENIS NBO - 105 MENGGUNAKAN CATIA V5R16

Helicopters have a unique advantage over airplanes in that they can adjust the direction of their blades to generate lift in any direction, allowing them to perform vertical takeoffs and landings and hover in one spot. This capability makes them highly valuable for a variety of operations, including transportation. A crucial component in the helicopter control system is the swash plate, which allows for adjustments to the angle of the rotor blades to achieve specific maneuvers.To manufacture and model components such as the swash plate, rotor head, and rotor blades, CATIA V5R16 software can be used. This involves modeling the individual parts in the workbench part design, assembling them in the workbench assembly design, or conducting kinematic analysis using the DMU Kinematics workbench to obtain values for linear velocity, angular velocity, linear acceleration, and angular acceleration. When compared to manual calculations, the differences between the results produced by the CATIA V5R16 software and theoretical calculations are negligible. Therefore, it can be concluded that CATIA V5R16 software is highly capable and suitable for conducting kinematic analysis of three-dimensional components.

A Novel Fault Diagnosis Method Based on SWT and VGG-LSTM Model for Hydraulic Axial Piston Pump

Since the hydraulic axial piston pump is the engine that drives hydraulic transmission systems, it is widely utilized in aerospace, marine equipment, civil engineering, and mechanical engineering. Operating safely and dependably is crucial, and failure poses a major risk. Hydraulic axial piston pump malfunctions are characterized by internal concealment, challenging self-adaptive feature extraction, and blatant timing of fault signals. By completely integrating the time-frequency feature conversion capability of synchrosqueezing wavelet transform (SWT), the feature extraction capability of VGG11, as well as the feature memory capability of the long short-term memory (LSTM) model, a novel intelligent fault identification method is proposed in this paper. First, the status data are transformed into two dimensions in terms of time and frequency by using SWT. Second, the depth features of the time–frequency map are obtained and dimensionality reduction is carried out by using the deep feature mining capability of VGG11. Third, LSTM is added to provide the damage identification model for long-term memory capabilities. The Softmax layer is utilized for the intelligent evaluation of various damage patterns and health state. The proposed method is utilized to identify and diagnose five typical states, including normal state, swash plate wear, sliding slipper wear, loose slipper, and center spring failure, based on the externally observed vibration signals of a hydraulic axial piston pump. The results indicate that the average test accuracy for five typical state signals reaches 99.43%, the standard deviation is 0.0011, and the average test duration is 2.675 s. The integrated model exhibits improved all-around performance when compared to LSTM, LeNet-5, AlexNet, VGG11, and other typical models. The proposed method is validated to be efficient and accurate for the intelligent identification of common defects of hydraulic axial piston pumps.

A novel approach to design compensator actuators for a swash plate axial piston pump along with the experimental validation

A novel approach to design compensator actuators for a swash plate axial piston pump along with the experimental validation