Piston eccentricity and friction force measurement in a hydraulic cylinder in dynamic conditions considering the form deviations on a piston
TL;DR: In this article, a test rig is designed and fabricated to measure the piston eccentricity and friction in a dynamic condition, and cylinders of defined geometric profiles such as elliptic and three-lobe are fabricated using a machining center.
Abstract: Geometrical imperfections on pistons cause an asymmetric pressure distribution in the clearance between the piston and cylinder bore. Due to this, the piston attains different eccentricity positions during a stroke. The eccentricity of the piston affects the performance of the cylinder by influencing the frictional and leakage aspects. A compact mechatronic test rig is designed and fabricated to measure the piston eccentricity and friction in a dynamic condition. Pistons of defined geometric profiles such as elliptic and three-lobe are fabricated using a machining center. These pistons have been introduced into the test rig. The eccentricity and dynamic friction tests are conducted at various operating conditions and the results are presented and analysed.
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TL;DR: A finite volume based Reynolds equation model has been formulated for the piston-cylinder clearance which considers the piston eccentricity and the relative tangential movement between piston and barrel as mentioned in this paper, and different grooves configurations have been evaluated in search of finding minimum leakage, minimum appearance of cavitation and maximum restoring torque.
Abstract: In the design of high pressure piston pumps/motors, some manufacturers use pistons which have grooves being cut along the piston length, while others do not use grooves at all. The present paper clarifies the effect of grooves cut along the pistons surface via studding the effect of the number of grooves and their location over the piston surface. Piston force, torque, leakage, areas where cavitation might appear and piston stability, will be, in the present paper and for a set of piston/grooves configurations, carefully evaluated. A finite volume based Reynolds equation model has been formulated for the piston–cylinder clearance which considers the piston eccentricity and the relative tangential movement between piston and barrel. Different grooves configurations have been evaluated in search of finding minimum leakage, minimum appearance of cavitation and maximum restoring torque. Design instructions to optimize the piston behavior are also given, therefore the information and methodology presented in the present paper, is expected to be used as a designing tool for future machines. The piston/cylinder leakage is considered as laminar under all working conditions. The Fluid used is hydraulic oil ISO 32.
60 citations
Cites background from "Piston eccentricity and friction fo..."
...[2] examined experimentally the pressure distribution in the clearance piston–cylinder and concluded that the eccentricity of the piston affected the performance of the piston by influencing the frictional and leakage aspects....
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TL;DR: In this paper, a non-Lipschitz friction force compensator based on periodic adaptive learning control (PALC) is proposed for the compensation of a state-dependent external disturbance of electromechanical systems.
Abstract: This paper uses the periodic adaptive learning control (PALC) for the compensation of a state-dependent non-Lipschitz external disturbance of electromechanical systems. Theoretically, we are interested in designing a non-Lipschitz friction force compensator, where the friction force is considered position-dependent external disturbance. The key idea of the proposed scheme is to make use of state-periodicity of an external disturbance on the iterative state domain. The state-periodical adaptive compensator designed based on Lyapunov stability analysis guarantees an asymptotical stability of the system after the first iterative trajectory and onwards. The designed-adaptive compensator is verified through an actual DC motor control test.
16 citations
Cites background from "Piston eccentricity and friction fo..."
...It is supposed that the non-Lipschitz discontinuity arises at zero velocity as commonly observed in electromechanical systems [20]....
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01 Jan 2009-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this paper, a 3D surface modelling approach is presented using random process modelling as the basis to model the grinding and honing processes which are commonly employed for the manufacture of the hydraulic assemblies.
Abstract: Friction in servo hydraulic assemblies reduces the response characteristics of the system. The friction is influenced by various factors including the geometry (form and surface errors) of the sliding surfaces. In this work, functionally significant 3D surface parameters from the Birmingham parameters are investigated for reduced friction. A 3D surface modelling approach is presented using random process modelling as the basis. An exponential decay areal autocorrelation function is used to model the grinding and honing processes which are commonly employed for the manufacture of the hydraulic assemblies. Honed surface is modelled with the crosshatches of appropriate angle. Method of surface modelling is validated using the data obtained through measurements on a practical surface. Different surface maps with varying surface parameters of the ground and honed surfaces are generated. The fluid continuum gap geometries of the hydraulic assemblies are modelled using these surface maps as envelopes. Pressure distribution, velocity and viscous friction force are used as measurands of the frictional characteristics. Using computational fluid dynamics (CFD) approach, these measurands are evaluated for different functionally significant Birmingham parameters. Based on further analysis, negative skewness, lower kurtosis values, higher valley fluid retention index were found to have lower frictional characteristics.
14 citations
TL;DR: In this article, the authors discuss the approach of isogeometric analysis (IGA) for solving the Reynolds equation in lubricated piston dynamics and show that the efficiency is improved remarkably than the traditional Finite Element Method (FEM) when the IGA approach is adopted.
Abstract: This paper discusses the approach of isogeometric analysis (IGA) for solving the Reynolds equation in lubricated piston dynamics. The simulation model consists of two parts: the differential-algebraic equations (DAE) in piston dynamics and the Reynolds equation for lubrication of piston-cylinder interface. Here, the transient positional states of piston governed by the DAE are calculated in Dymola while the friction forces together with lateral forces and their moments are computed by solving the Reynolds equation with the IGA approach in Matlab; two parts of computation are integrated through a real-time communication program. The results show that the efficiency is improved remarkably than the traditional Finite Element Method (FEM) when the IGA approach is adopted.
13 citations
TL;DR: In this article, the effect of grooves cut on the piston surface, the number of the grooves and their location over the piston surfaces on the volumetric efficiency of the hydraulic radial piston pumps was investigated.
Abstract: A radial piston pump often used in high pressure applications. The geometry of the pistons used affects the mechanical and volumetric efficiency of the pump and its long term performance. In the present study, the effect of grooves cut on the piston surface, the number of the grooves and their location over the piston surface on the volumetric efficiency of the hydraulic radial piston pumps was investigated. In order to perform the research tests, the three-piston fixed displacement pump with seven configurations was firstly designed and fabricated. The output flow rate of the pump was determined at pressure outlets of 350 and 500 bar and then the volumetric efficiency was calculated as the mean values of measured data. The results showed that the grooves cut on the piston surface produces a higher piston–cylinder overall leakage and then tend to reduce the volumetric efficiency. Also as the number of grooves being cut on piston surface increases, an increase in leakage will happen. In addition, b...
11 citations
Cites methods from "Piston eccentricity and friction fo..."
...The pressure distribution in the clearance piston–cylinder was experimentally inspected by Sadashivappa et al. (2001)....
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References
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TL;DR: In this paper, an experimental method of determining sliding friction forces in a pneumatic actuator is described, and several empirical and semi-empirical friction models are evaluated using measured friction force data.
Abstract: This paper describes an experimental method of determining sliding friction forces in a pneumatic actuator. Several empirical and semi-empirical friction models are evaluated using measured friction force data. A repeatability study is also performed to qualitatively assess friction randomness and a change in friction regimes.
30 citations
TL;DR: In this article, an attempt is made to analyse systematically the three types of profiles commonly considered for high speed actuators, using Reynolds' differential equation, and analyses are made using an analytical method for one-dimensional flow and using the finite element method for twodimensional flow.
Abstract: In a high speed hydraulic actuator the usage of seals on the piston surface causes excessive wear on the seals and positional inaccuracies owing to coulomb friction. Hence sealless pistons with sloping surfaces have been tried by some manufacturers of such actuators. Here an attempt is made to analyse systematically the three types of profiles commonly considered for high speed actuators, using Reynolds' differential equation. Analyses are made using an analytical method for one-dimensional flow and using the finite element method for two-dimensional flow. The analyses reveal that single tapered pistons have certain limitations and that double tapered pistons can function successfully under different conditions in hydraulic actuators. It is also shown that friction in these types of pistons is much less than in conventional pistons with seals.
17 citations
TL;DR: In this article, the effect of machining imperfections like out-of-roundness and taper in the piston on the mechanical and volumetric efficiency of the motor, in the speed range where the viscous friction is dominant, is studied.
Abstract: Axial piston motors rely on a close fit of piston to bore to minimise leakage past the piston due to axial pressure drop. Machining imperfections in the cylinder bore and the piston change the clearance between them, affecting the performance of the motor. The effect of machining imperfections like out-of-roundness and taper in the piston on the mechanical and volumetric efficiency of the motor, in the speed range where the viscous friction is dominant, are studied. Experiments to measure torque and leakage flow are conducted on a fixed displacement swash plate type axial piston hydraulic motor and results are presented.
16 citations
TL;DR: In this paper, a new test-rig has been developed to test the actuators, and the test results confirm the main findings of the theoretical study on three types of tapered pistons.
Abstract: Use of seals on the piston surface of servo hydraulic actuators causes, apart from excessive wear, positional inaccuracies arising out of large mechanical friction due to physical contact In order to improve their performance, modern servo hydraulic actuators use pistons with tapered surfaces When such pistons move within the cylinder there is a chance of generating sufficient oil pressure to lift the piston owing to hydrodynamic action Theoretical study on three types of such pistons was reported earlier In this paper, experimental work carried out on those tapered pistons is presented A new test-rig has been developed to test the actuators, and the test results confirm the main findings of the theoretical study
15 citations