scholarly journals Degradation Status Recognition of Axial Piston Pumps under Variable Conditions Based on Improved Information Entropy and Gaussian Mixture Models

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1084
Author(s):  
Chuanqi Lu ◽  
Zhi Zheng ◽  
Shaoping Wang
Keyword(s):  
Information Entropy ◽  
Gaussian Mixture ◽  
Operating Conditions ◽  
Processing Variable ◽  
Axial Piston Pumps ◽  
Failure Data ◽  
Status Recognition ◽  
Axial Piston ◽  
Variable Operating Conditions ◽  
Instantaneous Energy

Axial piston pumps are crucial for the safe operation of hydraulic systems and usually work under variable operating conditions. However, deterioration status recognition for such pumps under variable conditions has rarely been reported until now. Therefore, it is valuable to develop effective methods suitable for processing variable conditions. Firstly, considering that information entropy has strong robustness to variable conditions and empirical mode decomposition (EMD) has the advantages of processing nonlinear and nonstationary signals, a new degradation feature parameter, named local instantaneous energy moment entropy, which combines information entropy theory and EMD, is proposed in this paper. To obtain more accurate degradation feature, a waveform matching extrema mirror extension EMD, which is used to suppress the end effects of EMD decomposition, was employed to decompose the original pump’s outlet pressure signals, taking the quasi-periodic characteristics of the signals into consideration. Subsequently, given that different failure modes of pumps have different degradation rates in practice, which makes it difficult to effectively recognize degradation status when using the modeling methods that need the normal and failure data, a Gaussian mixture model (GMM), which has no need for failure data when building a degradation identification model, was introduced to capture the new degradation status index (DSI) to quantitatively assess the degradation state of the pumps. Finally, the effectiveness of the proposed approach was validated using both simulations and experiments. It was demonstrated that the defined local instantaneous energy moment entropy is able to effectively characterize the degree of degradation of the pumps under variable operating conditions, and the DSI derived from the GMM is able to accurately identify different degradation states when compared with the previously published methods.

Improving the Volumetric Efficiency of the Axial Piston Pump

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Shu Wang
Keyword(s):  
Operating Conditions ◽  
Volumetric Efficiency ◽  
Valve Plate ◽  
Piston Pump ◽  
Efficient Design ◽  
Axial Piston Pumps ◽  
Definition Of ◽  
Engineering Practices ◽  
First Time ◽  
Axial Piston

The volumetric efficiency is one of the most important aspects of system performance in the design of axial piston pumps. From the standpoint of engineering practices, the geometric complexities of the valve plate (VP) and its multiple interactions with pump dynamics pose difficult obstacles for optimization of the design. This research uses the significant concept of pressure carryover to develop the mathematical relationship between the geometry of the valve plate and the volumetric efficiency of the piston pump. For the first time, the resulting expression presents the theoretical considerations of the fluid operating conditions, the efficiency of axial piston pumps, and the valve plate designs. New terminology, such as discrepancy of pressure carryover (DPC) and carryover cross-porting (CoCp), is introduced to explain the fundamental principles. The important results derived from this study can provide clear recommendations for the definition of the geometries required to achieve an efficient design, especially for the valve plate timings. The theoretical results are validated by simulations and experiments conducted by testing multiple valve plates under various operating conditions.

Applicability of Pump Models for Varying Operational Conditions

2003 ◽  
Author(s):  
Heikki O. J. Kauranne ◽  
Jyrki T. Kajaste ◽  
Asko U. Ellman ◽  
Matti T. Pietola
Keyword(s):  
Rotational Speed ◽  
Operating Conditions ◽  
Fluid Temperature ◽  
Limited Information ◽  
Operational Conditions ◽  
Axial Piston Pumps ◽  
Pump Construction ◽  
Temperature And Pressure ◽  
Axial Piston ◽  
Type Pressure

It is commonly known that the characteristics of a fluid power pump depend on pump type, pressure, rotational speed and displacement. But in addition to these, also all the other parameters or factors associated with the operating conditions may have a significant effect on the characteristics. The most important of these are the pump construction and size, operating point temperature and the characteristics of the oil, which also depend on temperature and pressure. The aim of this study is to show the effects that the varying operational conditions have on the characteristics of a axial piston pump, to compare the measured characteristics with other published characteristics of axial piston pumps and to study the capability of pump models to represent these characteristics. The results include information of the effects of fluid temperature, type of fluid and the setting value of the displacement on the pump characteristics along with the effects of pressure and rotational speed. The sensitivity of the pump to each of the parameters is discussed. The effect of limited information of pump characteristics on the reliability of simulation results is studied using the Schlo¨sser models.

An Approach to Visualize Lifetime Limiting Factors in the Cylinder Block/Valve Plate Gap in Axial Piston Pumps

2017 ◽  
Author(s):  
Roman Ivantysyn ◽  
Ahmed Shorbagy ◽  
Jürgen Weber
Keyword(s):  
State Of The Art ◽  
Operating Conditions ◽  
Valve Plate ◽  
Limiting Factors ◽  
Cylinder Block ◽  
Axial Piston Pumps ◽  
First Results ◽  
Gap Height ◽  
Axial Piston ◽  
External Loads

The lifetime of axial piston pumps is depending on the application and it’s overall robustness to external loads, but even in ideal conditions pumps will fail eventually. The analytics to this problem are known to pump manufacturers. Bearing and shaft calculations paired with FEM models are invaluable tools, however the main questions remain with the rotating kit – cylinder block, pistons, and slippers. If properly designed these parts should theoretically outlast the finite lifetime parts, such as roller bearings due to their hydrostatic and hydrodynamic bearings. In reality however failures still occur due to fatigue or other factors such as contamination or wear. This paper describes an approach for the thermal analysis of the cylinder block / valve plate sealing interface. Using a state of the art test rig the temperature distribution, instantaneous gap height as well as particle wear have been analyzed across the entire operating range of an axial piston pump at the block / valve plate sealing interface. Simulations are done with cooperation of Purdue University by using their developed gap simulation model called Caspar FSTI. These simulations along with the measurements are used to locate potential lifetime reducing operating conditions and analyze them. The first results of the thermal behavior of this interface will be presented in this paper.

Half-frequency whirl of pistons in axial piston pumps and motors under mixed lubrication

2003 ◽  
Vol 217 (2) ◽  
pp. 93-102 ◽  
Author(s):  
K Tanaka ◽  
T Nakahara ◽  
K Kyogoku
Keyword(s):  
Mixed Lubrication ◽  
Operating Conditions ◽  
Axial Piston Pump ◽  
Piston Motion ◽  
Axial Piston Pumps ◽  
Supply Pressure ◽  
Oil Whirl ◽  
Lubrication Characteristics ◽  
Axial Piston ◽  
Lubrication Conditions

Dynamic lubrication characteristics between a piston and a cylinder in an axial piston pump and motor have been calculated under mixed-lubrication conditions. The calculated results have shown that half-frequency whirling of the piston occurs under some operating conditions and specifications such as low supply pressure, narrow clearance and long sealing length between the piston and the cylinder, in a manner similar to the oil whirl phenomenon in journal bearings. The whirl phenomenon has been confirmed by measurements of piston motion.

The Effects of Non-Flatness on the Performance of Slippers in Axial Piston Pumps

1983 ◽  
Vol 197 (4) ◽  
pp. 239-247 ◽  
Author(s):  
C J Hooke ◽  
Y P Kakoullis
Keyword(s):  
Film Thickness ◽  
Operating Conditions ◽  
Successful Operation ◽  
Small Deviations ◽  
Axial Piston Pumps ◽  
Satisfactory Performance ◽  
Wide Range ◽  
Minimum Film Thickness ◽  
Axial Piston ◽  
The Relationship

All previous analyses of slippers in axial piston pumps have assumed that the slipper running surface was perfectly flat and have all failed to explain the satisfactory performance of these bearings. It has been suggested, however, that slippers in axial piston pumps may depend, for their successful operation, on the small deviations from a perfect flat of the slipper surface. This paper examines the relationship between such a non-flatness and the minimum film thickness produced under steady operating conditions. It is shown that a very wide range of slipper non-flatnesses can lead to satisfactory slipper performance and that the minimum film thickness predicted is remarkably insensitive to the actual amount of deviation from flat.

scholarly journals Numerical Simulation of a Slipper Model with Multi-Lands and Grooves for Hydraulic Piston Pumps and Motors in Mixed Lubrication

Lubricants ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 55
Author(s):  
Toshiharu Kazama
Keyword(s):  
Numerical Simulation ◽  
Contact Pressure ◽  
Power Loss ◽  
Numerical Solutions ◽  
Friction Torque ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Axial Piston Pumps ◽  
Wide Range ◽  
Axial Piston

A theoretical model of a slipper with multi-lands and multi-grooves for swashplate type axial piston pumps and motors was established, including surface interactions. Further, a numerical simulation was conducted under an unsteady state and mixed lubrication conditions. Four model configurations were considered: A slipper with a single main land; a slipper with inner and main lands and a groove; a slipper with outer and main lands and a groove; and a slipper with inner, main, and outer lands with two grooves. Numerical solutions were obtained across a wide range of operating conditions in terms of center clearance, pad attitude, contact pressure, flow rate, friction torque, power loss, and stiffness. The motion and characteristics were differentiated into two groups: Slippers with a single-land and an annex inner-land; and slippers with an annex outer-land and a triple-land. The single-land and annex inner-land slippers exhibited smaller pad swing, whereas the triple-land and annex outer-land slippers reduced contact pressure and power loss.

Hydrodynamic Factors Affecting the Design of Valve Plates and Thrust Bearings

1966 ◽  
Vol 181 (1) ◽  
pp. 653-666 ◽  
Author(s):  
J. McKeown ◽  
D. A. Milner ◽  
N. A. Shute ◽  
D. E. Turnbull
Keyword(s):  
Fluid Pressure ◽  
Operating Conditions ◽  
Fluid Viscosity ◽  
Fluid Temperature ◽  
Mechanical Seals ◽  
Approximate Methods ◽  
Factors Affecting ◽  
Thrust Bearings ◽  
Axial Piston Pumps ◽  
Axial Piston

The limitations of analyses of the characteristics of viscous flow systems based on the assumption of constant fluid viscosity have been recognized for a considerable period of time and attempts to overcome them have previously been made by suggesting the use of a ‘mean effective’ value of viscosity. It has become increasingly obvious, however, that the large changes which often occur in the value of the viscosity of most hydraulic fluids suitable for use in fluid power and lubricating systems can no longer be disregarded and a more exact study of the results of the effects produced by variations of both pressure and temperature on the viscosity of such fluids is desirable. The present work contains such an analysis, and consideration is given to a system wherein combined Couette and Poiseuille flows occur. Predictions are made of the effects produced under certain operating conditions by the variation of the viscosity of the fluid with both the instantaneous values of the fluid pressure and the fluid temperature. Methods of applying these results to studies of the operation of valve plates for axial piston pumps and motors, radial face or mechanical seals and hydrostatic thrust bearing design are indicated. Approximate methods of allowing for the effects of heat losses by conduction through the rigid boundaries of the film are suggested and some results of a computer study of these conditions are described.

scholarly journals A Methodology Based on Cyclostationary Analysis for Fault Detection of Hydraulic Axial Piston Pumps

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1874 ◽  
Author(s):  
Paolo Casoli ◽  
Andrea Bedotti ◽  
Federico Campanini ◽  
Mirko Pastori
Keyword(s):  
Power Systems ◽  
Operating Conditions ◽  
Fault Identification ◽  
Hydraulic Systems ◽  
Axial Piston Pumps ◽  
Data Driven Approach ◽  
Variable Displacement ◽  
Fluid Power Systems ◽  
Axial Piston ◽  
Acceleration Signals

Condition monitoring has been an active area of research in many industrial fields during the last decades, particularly in fluid power systems. This paper presents a solution for the fault diagnosis of a variable displacement axial-piston pump, which is a critical component in many hydraulic systems. The proposed methodology follows a data-driven approach including data acquisition and feature extraction and is based on the analysis of acceleration signals through the theory of cyclostationarity. An experimental campaign was carried out on a laboratory test bench with the pump in the flawless state and in faulty states. Different operating conditions were considered and each test was repeated several times in order to acquire a suitable population to verify data repeatability. Results showed the capability of the proposed approach of detecting a typical fault related to worn slippers. Future works will include tests in order to apply the approach to a wider set of faults and the development of a classifier for accurate fault identification.

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