Compression loss is one of the volumetric losses of bent-axis piston pumps, and its accurate evaluation is the basis for predicting the effective flow rate and volumetric efficiency of bent-axis piston pumps. The effect of changes in gas content on the effective bulk modulus rarely is considered in the existing compression loss models, which does not apply to the compression loss of bent-axis piston pumps under cavitation. However, cavitation exists in the actual work, especially in increasing the speed of the bent-axis piston pump. To solve this problem, a compression loss model is proposed. Firstly, the modified Henry’s law and the simplified transport equations of gas are used to describe the oil gas content under cavitation, and the effective bulk modulus equation is established. Then, combined with the definition of compressibility, the compression loss model of the bent-axis piston pump is proposed. Finally, the compression loss of the bent-axis piston pump under different operating conditions is analyzed through simulation, and the results are verified by experiment. The results show that the model prediction results are a good agreement with the experimental results under different operating conditions. The conclusions provide a new method for evaluating the effective flow rate and volumetric efficiency in the bent-axis piston pump.

为提高变频调速液压系统的调节范围和响应速度,提出一种变频液压泵和定速液压泵组合的液压调速方案.建立系统数学模型,结合液压泵许用转速范围,给出两个液压泵的流量分配关系.以泵控马达液压系统为例,建立基于转速PID控制的系统仿真模型,对其调速性能进行验证.结果表明:采用所提的调速方案可实现转速连续平稳调节,液压泵的流量分配符合设计要求.

Purpose This paper aims to revel the leakage characteristics of the bent-axis piston pump considering elastohydrodynamic deformation via a dynamic leakage model. Design/methodology/approach A dynamic leakage model of bent-axis piston pump based on elastohydrodynamic lubrication theory is proposed, which is used to present the leakage characteristics of bent-axis piston pump. The model is composed of three parts. First, the dynamic gap in the piston ring-cylinder bore interface (PRCB) is described via the elastohydrodynamic lubrication equations. Then, the PRCB leakage is presented based on the dynamic gap. Finally, combined with leakage equation of the valve plate-cylinder block interface (VPCB), the total leakage model is proposed. Through the numerical simulation and experiment, the leakage characteristics of bent-axis piston pump considering elasto-hydrodynamic deformation are studied. Findings The PRCB leakage is negatively correlated with VPCB leakage under the range of 800–1400 r/min and 1–25 MPa. When the discharge pressure is less than the critical pressure, the PRCB leakage is the main factor affecting the total leakage in bent-axis piston pump. On the contrary, the VPCB leakage is the main factor. The critical pressure increases with increasing speed Originality/value The effect of operating parameters has a significant effect on the elastic deformation of piston ring without considering wear of friction pairs in bent-axis piston pump. There is a critical phenomenon in the leakage, which is related to the operating parameters, and provides a novel idea for extracting wear information from leakage and evaluating the status of bent-piston pump.

The bent-axis piston pump is the core component of electrohydrostatic actuators (EHA) in aerospace applications, and its wear of key friction interfaces is greatly related to the healthy operation of pumps. The leakage of the piston ring-cylinder bore interface (PRCB), as the important part of the return oil flow of the pump house that commonly assesses the wear of key friction interfaces in piston pumps, is changed with the rotation speed. Thus, the wear of key friction interfaces is usually inaccurate by using the leakage of PRCB. In order to obtain the relationship between the PRCB leakage and the rotation speed, an elastohydrodynamic lubrication model is proposed. First, the proposed model includes a minimum film thickness model of PRCB to analyze the dynamic change of oil film of PRCB when subject to the elastohydrodynamic lubrication. After that, a mathematical model of PRCB is induced by combining the minimum film thickness model with the flow equation, which helps produce the effects of the oil film on the leakage of PRCB. The proposed model is verified by numerical simulation and experiment. The results show that the leakage of PRCB has a negative effect on the return oil flow of the pump case in the range of rotation speed of 700–1300 r/min and discharge pressure of 10–20 MPa. Furthermore, the leakage of PRCB is proportional to the rotation speed, but the return oil flow of the pump case is decreased. The effects of rotation speed are enhanced under the high discharge pressure conditions.

The opportune fault detection of the rolling element bearings can avoid serious equipment accidents or even casualties. However, the early fault features of the bearings are weak and often submerged in heavy background noise and interferences. This paper proposes a novel approach for bearing fault diagnosis based on the hard thresholding fast iterative filtering (HTFIF), IMF selection index integrating L- kurtosis, correlation coefficient and autocorrelation function impulse harmonic to noise ratio (L-KCA), and improved k-value symmetrical difference analytic energy operator (k-SDAEO). As an adaptive and fast time-frequency analysis method, HTFIF is first adopted to process the bearing vibration signal and obtain a series of IMFs. After that, an alternative fusion index L-KCA is developed to select the sensitive IMF. Finally, a novel k-SDAEO with strong noise robustness is presented to process the selected IMF. With this method, the weak bearing fault signatures can be identified from the energy spectrum. The performance of the proposed method comparing to the traditional methods are investigated by numerical simulation and experimental studies. The results show that the proposed method has better fault feature extraction capability and higher efficiency, which can be implemented in the on-line and real-time fault detection.

In view of the problem of the BP neural network's slow convergence speed, falling into local minimum easily, an adaptive RBF neural network for dexterous manipulator control is solved, combined with the dexterous manipulator the requirements of real-time control. The Neural network control method of dexterous manipulator is studied, using three layer feed forward network of RBF, based on dynamic model of the dexterous manipulator. Finally, the method of that is simulated by MATLAB software, showing that the control strategy can effectively improve the accuracy, robustness and adaptability.

In order to reveal flow characteristics of the axial piston pump with conical barrel caused by the change of operating parameters, the A4VSO40 variable piston displacement pump with conical barrel is used as the research object. The kinematics equation is established based on the spatial position relation of the plunger, and the relationship between the displacement and velocity of single plunger and the structural parameters of the axial piston pump of the inclined plunger are expounded. Then the simulation model of the axial piston pump with conical barrel is built by using AMESim platform, and the effects of swash plate angle, spindle speed and working pressure on the pul-sation characteristics of flow are analyzed. The results show that the average flow rate and amplitude of pulsation increase with the increase of the swash plate angle and spindle speed, but the pulse rate decreases. The average flow, pulse amplitude and pulse rate reduces with work-ing pressure increases.

The measurement and control system for the performance parameters of the vortex pump was researched.Based on introducing the measurement and control system's structure and working principle of the test bench,the control and data acquisition of the test process was achieved through PLC control system,the data analysis,storage and real-time display was realized by the LabVIEW software in the PC,and the data communication between the upper computer and the lower computer is realized by the OPC technology.The development of the measurement and control platform of the vortex pump testing system was completed.The platform has friendly man-machine interface,reliable operation,good opening and expansibility,and can better meet the needs of the test of the performance of the vortex pump.

In this paper, a set of monitoring system for aircraft piston pump operation condition is de-signed. Based on the working principle of simulated test bench of the aircraft piston and the design idea of the monitoring system, using PLC control system for collection and processing of key parameters of the operation status,and using LabVIEW for analysis and real-time display of data, the data communication between PLC and LabVIEW is realized by combination with OPC for monitoring operation status parame-ters of the aircraft piston pump, which is of great significance to ensure the safe and stable operation of the aircraft piston pump.

In order to solve fault in the comprehensive performance hydraulic test rig under the load simulation condition,the output characteristic curves under different rotating speed were analyzed from the low speed stabihty of hydraulic power system,the occurrence mechanism of the fault was expounded through the establishment of mechanical characteristics of variable-frequency motor model.Combined with the characteristics of the dynamic system of the hydraulic test rig,the corresponding processing method was proposed,and its validation was carried out.The results show that the method can effectively solve the fault of the comprehensive performance hydraulic test rig.It has great guidance and reference significance to protect the safe and stable operation of hydraulic test rig.

The problem for the low speed characteristics of the hydraulic power system with variable speed was studied by using AMESim and experimental verification method from the mechanical characteristics of induction motor and the efficiency of the piston pump.The results show the hydraulic power system of variable speed is low because of small maximum output torque of drive motor, weak mechanical properties and the low efficiency of the piston pump, the flow instability at low speed running state, which provide reference for improving the low speed characteristics of hydraulic power system with variable speed.

为深入了解旋转作用力对涡轮叶片多段连接通道换热特征的影响,采用三维数值模拟方法研究了多段连接内通道模型的流动换热.选取通道入口雷诺数为17 000、旋转数范围为0 ～0.09,多段连接通道3个出口的质量流量比例为25％、50％、25％,旋转半径与水力直径之比的范围为0 ～69.6,研究了旋转数、旋转半径对各段通道带肋壁面换热分布的影响.结果表明:旋转附加力造成径向出流通道沿程压力系数逐渐增大,径向入流通道的沿程压力系数迅速减小;径向出流通道后缘面的换热系数随旋转数增加而增大,径向入流通道后缘面的换热系数随旋转数增加而稍有减小,旋转作用对前缘面换热的影响情况与后缘面的情况相反;前、后缘面的换热系数沿流向均随旋转半径与水力直径比的增加稍有增大,换热增大幅度较小.

以电机拖动轴向柱塞泵为研究对象,依据液压动力系统运行时机电液参量间的耦合效应,深入分析了柱塞泵发生单柱塞泄漏故障下引起的流量、电磁转矩、电流发生故障脉动的机制.利用AMESim对其仿真分析,其结果表明:在柱塞泵发生单柱塞泄漏故障下系统流体参量出现故障脉动频率,再通过电机与泵的耦合反向作用于电机电流信号,使其出现表征发生该故障的边频分量,且特征频率幅值随着负载增大而增加,为从电流信号中提取轴向柱塞泵故障信息提供了一种新思路.