•Based on power spectral entropy (PSE), a novel method of PSE-Autogram is proposed.•Fault feature information can be made highlighted by PSE.•PSE can select the node that is rich in fault feature ...information.•PSE-Autogram performs much better than Autogram and fast kurtgram.•PSE-Autogram is testified using both simulated and measured signals.
Autogram is a good tool to extract the fault feature information from a fault vibration signal of rolling element bearings. Structure of a hydraulic pump is more complicated than the rolling element bearings, and its vibration signal is more contaminated by heavy Gaussian and non-Gaussian noises if slipper wear fault happens, and too many noise amplitudes can be introduced into computation of kurtosis in the time domain, and a data source of containing rich fault feature information cannot be successfully selected by the kurtosis, and it is ineffective application of the hydraulic pump. Aiming to resolve the above problems, an improved Autogram called PSE-Autogram is proposed. Its key and different selection of the data source is completed by the power spectral entropy (PSE) rather than the kurtosis, and the fault feature information can be made highlighted and noise can be suppressed by PSE in the frequency domain, and shortcomings of the original Autogram can be effectively overcame. A simulated signal and a slipper wear fault signal are tested and verified, and results demonstrate that PSE-Autogram performs better than Autogram and traditional fast kurtogram based on the assessment criterion of feature energy ratio.
•Failure causes of O-ring based on floating bush of pump are analyzed.•The effect of the alternative change of clearance size is considered.•The effect of the abrupt change of fluid pressure is ...considered.•The operating conditions of the O-ring are simulated by finite element analysis.•The dynamic equivalent stress and contact stress are obtained.
The sealing structure of the floating bush is used to connect the cylinder barrel and the valve plate and compensate for the inconsistency of the motion, which is caused by the offset of the cylinder barrel under the external load and the dynamic pressure of the water film. In the process of compensation, the alternative change of clearance size between closing ring and piston bush and the abrupt change of fluid pressure on O-ring make the O-ring extrude and occlude continuously, leading to seal failure and reduced service life. The sealing performance and service life of the O-ring directly affect the working performance of water hydraulic pump. Failure of the O-ring will lead to lower efficiency of water hydraulic pump. In this paper, the geometric relationship of the O-ring is obtained by analyzing the force and motion of cylinder barrel in offset state. Based on Mooney-Rivlin constitutive relation of the rubber material, a two-dimensional finite element model is established. The fluid pressure load and the swing load of the piston bush are applied. The dynamic equivalent stress and contact stress are analyzed, under the limit conditions of the O-ring assembly, loading fluid pressure and swing occlusion. The failure parts and causes are determined, which provides a theoretical basis for the optimization of the sealing structure of the floating bush.
Multi-sensor fusion technique is used to combine the complementary information source from the multiple sensors. However, the multi-sensor data are obviously different with the characteristics of ...complex types, different dimensions or different weights, which is easy to cause the difficulty of the fusion and the decline of the ability of information representation although the fault information is enriched. Therefore, a new multi-sensor information fusion technique using processed images is proposed. The core of this technique is to convert the information from different sensors (especially for heterogeneous sensors) into images for weighting feature matrix and constructing image fusion to realize fault diagnosis. In the technique, the processed images can enhance the weak signal in a complex environment and avoid the weak applicability caused by multi-sensor sampling differences. The proposed algorithm is based on improved data-enhanced Gramian Angular Sum Field (DE-GASF) and multi-channel dual attention convolutional neural network (MC-DA-CNN). And the performance of the algorithm is validated by experiments on basic hydraulic components, taken axial piston pump and hydraulic reversing valve as an example. The experimental results show that the average fault diagnosis accuracy of axial piston pump and hydraulic reversing valve is 97.6% and 99.4% respectively, but the traditional monitoring method and single-sensor intelligent method are difficult to detect their faults due to their bad working environment. In addition, a comparative analysis of the image processing method and the time domain signal processing method confirms the effectiveness of the proposed technique.
Multisensor fusion technique is used to combine the complementary information source from the multiple sensors. However, the multisensor data are obviously different with the characteristics of ...complex types, different dimensions, or different weights, which is easy to cause the difficulty of the fusion and the decline of the ability of information representation although the fault information is enriched. Therefore, a new multisensor information fusion technique using the processed images is proposed. The core of this technique is to convert the information from different sensors (especially for heterogeneous sensors) into images for weighting feature matrix and constructing image fusion to realize fault diagnosis. In the technique, the processed images can enhance the weak signal in a complex environment and avoid the weak applicability caused by multisensor sampling differences. The proposed algorithm is based on an improved data-enhanced Gramian angular sum field (DE-GASF) and multichannel dual attention convolutional neural network (MC-DA-CNN). Also, the performance of the algorithm is validated by experiments on basic hydraulic components, taking axial piston pump and hydraulic reversing valve as an example. The experimental results show that the average fault diagnosis accuracy of axial piston pump and hydraulic reversing valve is 97.6% and 99.4%, respectively, but the traditional monitoring method and single-sensor intelligent method are difficult to detect their faults due to their bad working environment. In addition, a comparative analysis of the image processing method and the time-domain signal processing method confirms the effectiveness of the proposed technique.
This paper describes the design of a swash plate axial piston pump and the theoretical models describing the bulk modulus of aerated and non-aerated fluids. The dead space volume is defined and the ...influence of this volume and the fluid compressibility on the volumetric efficiency of the pump is considered. A displacement of the swash plate rotation axis is proposed to reduce the dead space volume for small swash plate swing angles. A prototype design of a pump with a displaced axis of rotation of a swash plate with two directions of delivery is presented, in which the capacity is changed by means of a valve follow-up mechanism. Comparative results for a pump with a displaced and a non-displaced swash plate rotation axis are presented, which confirm that displacement of the swash plate rotation axis causes an increase in volumetric efficiency that is apparent for high pressure discharge and small swash plate angles. The determined characteristics were compared with a mathematical model taking into account the compressibility of the fluid in the dead space volume and a satisfactory consistency was obtained.
One of the elements that affect the reliability and service life of a hydraulic pump is the stability level of oil viscosity as a power successor. The stability level of oil viscosity is affected by ...changes in temperature. The compression and friction process that the oil receives to move the hydraulic pump will increase the oil temperature so that its viscosity level will decrease. To maintain the performance of the hydraulic pump, the oil temperature must be maintained at room temperature. In the case study at PLTA Ir. H. Djuanda, Lurah Kawi Street No.1 Jatiluhur-West Java, to cool the oil, a shell and tube heat exchanger type JPK 13699068 (single tube) is used. This research was conducted to test whether the heat exchanger is still working properly, the parameter is that the cooled oil exit temperature must be close to room temperature. The effectiveness of the heat exchanger will be tested by comparing the test results with the condition of the heat exchanger without impurity factors. The test was carried out by measuring the temperature of the HX intake oil at 44 0C with a discharge of 0.437 kg/s, and the temperature of the HX inlet water at 28 0C with a discharge of 0.498 kg/s. The results showed that, for the coefficient of U between 110 to 350 W/m2 oC with a water impurity factor of 0.0001 m2 oC/W and an oil impurity factor of 0.0002 m2 oC/W, there was a decrease in effectiveness from an average of 74.5% to 73.7%, and there was an increase in oil temperature out of the heat exchanger from an average of 32.07 oC to an average of 32.21 oC.
In hydraulic pump system various states can occur caused by mechanical and physical phenomena. To detect them, the Short Time Fourier Transform (STFT) is applied. This paper will consider an ...application of STFT to monitor and evaluate hydraulic pump system operation in different states of operation. For measurements of pressure and flow changes in pump, hydraulic tester and DAQ card was used for evaluation of qualitative and quantitative changes in the system. Results of hydraulic pump’s operation will be shown on Fast Fourier Transform (FFT) charts and STFT spectrograms plots.
The paper presents a method on the basis of Elasto Hydrodynamic Lubrication (EHL) model to analyze the wear behavior of swash plate/slipper pair. Based on the analysis of film thickness, the ...associated internal factors affecting the wear behavior are identified by considering comprehensively parameters of structure, working conditions and material properties. The comparison of the wear masses of theoretical analysis and wear tests verifies the proposed method. The relationships between wear rate of the friction pair and associated parameters are analyzed. Research results can be utilized to compile the accelerated test load spectrum and contribute to optimizing the pump design.
•Elasto Hydrodynamic Lubrication model is applied to analyze pump wear behavior.•The wear behavior influencing factors are identified by analyzing film thickness.•The effects on wear rate for associated parameters are illustrated thoroughly.
In this paper, the vibration characteristics of a parallel hydraulic hybrid vehicle (PHHV) powertrain are investigated. A powertrain model is built to capture the natural frequencies and mode shapes ...before model reduction is conducted to simplify the system complexity. The natural frequencies and the mode shapes of the PHHV are compared with the original vehicle. Results show that with a hydraulic pump/motor (HPM) added on the powertrain, the dynamic response to engine excitation is increased only at the first natural frequency. Due to the minimum engine excitation frequency being higher than the first natural frequency of the system, resonance is avoided. The HPM also introduces excitation to the PHHV powertrain due to its instantaneous torque fluctuations. As HPM excitation is much smaller than the engine excitation, it does not produce excessive vibrations even though the powertrain frequency response is near its lowest resonant frequency. These results indicate that the NVH characteristics of the powertrain are not significantly influenced by the significant changes to the system architecture resulting from the addition of the HPM. Additionally, the HPM is not exposed to significant sources of vibration from the forced responses of the engine. Consequently, the need for substantive vibration isolation for the HPM is reduced.
Low pressure fluid transport (1) applications often require low and precise volumetric flow rates (2) including low leakage to reduce additional costly and complex sensors. A peristaltic pump design ...(3) was realized, with the fluid’s flexible transport channel formed by a solid cavity and a wobbling plate comprising a rigid and a soft layer (4). In operation, the wobbling plate is driven externally by an electric motor, hence, the soft layer is contracted and unloaded (5) during pump-cycles transporting fluid from low to high pressure sides. A thorough characterization of the pump system is required to design and dimension the components of the peristaltic pump. To capture all these parameters and their dependencies on various operation-states, often complex and long-lasting dynamic 3D FE-simulations are required. We present, here, a holistic design methodology (6) including analytical as well as numerical calculations, and experimental validations for a peristaltic pump with certain specifications of flow-rate range, maximum pressures, and temperatures. An experimental material selection process is established and material data of candidate materials (7) (liquid silicone rubber, acrylonitrile rubber, thermoplastic-elastomer) are directly applied to predict the required drive torque. For the prediction, a semi-physical, analytical model was derived and validated by characterizing the pump prototype.
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