Pressure Peaks in the Hydraulic Actuator

1965 ◽  
Vol 87 (4) ◽  
pp. 953-959 ◽  
Author(s):  
D. McCloy
Keyword(s):  
Fatigue Failure ◽  
Opposite Effect ◽  
Experimental Studies ◽  
Cavity Formation ◽  
Loading Conditions ◽  
Hydraulic Actuator ◽  
Cavitation Damage ◽  
Hydraulic Actuators ◽  
Valve Overlap ◽  
Severe Loading

Results are presented of theoretical and experimental studies of the pressure peaks occurring in valve-controlled hydraulic actuators operated under severe loading conditions. Oil compressibility is shown to reduce the magnitude of these peaks. Valve overlap has the opposite effect. The possibilities of fatigue failure and cavitation damage in the actuator are discussed. The two different modes of cavity formation which occur when the valve is oscillated sinusoidally are discussed in detail.

Cavity Formation in Valve Controlled Hydraulic Cylinders

1969 ◽  
Vol 184 (1) ◽  
pp. 969-982 ◽  
Author(s):  
D. Mccloy
Keyword(s):  
Dynamic Response ◽  
Good Reason ◽  
Linear Equations ◽  
Cavity Formation ◽  
Hydraulic Actuator ◽  
Cavitation Damage ◽  
Non Linear ◽  
Hydraulic Cylinders ◽  
Non Linear Equations

Solutions are developed of the non-linear equations describing the response of a valve driven hydraulic actuator to step inputs. Compressibility is neglected but cavitation is taken into consideration. It is shown that under certain conditions cavities can exist on both sides of the actuator piston. It is argued that there is no good reason why hydraulic servos should not be operated in a cavitating mode. The effects of cavitation on dynamic response and the possible effects of cavitation damage are discussed.

Cavitation in Valve-Controlled Hydraulic Actuators

1963 ◽  
Vol 30 (4) ◽  
pp. 537-546 ◽  
Author(s):  
P. K. C. Wang ◽  
J. T. S. Ma
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Close Agreement ◽  
Experimental Studies ◽  
Experimental Results ◽  
Cavity Formation ◽  
Hydraulic Actuators ◽  
Operating Modes ◽  
Analytical Work ◽  
Critical Cavitation

Results of analytical and experimental studies of cavitation in valve-controlled hydraulic actuators under various dynamic conditions are presented. The analytical work consists of deriving approximate critical cavitation conditions for various operating modes. The experimental investigation includes both a high-speed photographic study of cavity formation and tests to check the validity of the derived cavitation conditions. Close agreement between analytical and experimental results was obtained. The mechanisms governing cavity formation and cavitation effects are discussed qualitatively.

TOUGHMET 2CX

Alloy Digest ◽  
2013 ◽  
Vol 62 (6) ◽  
Keyword(s):  
Tensile Strength ◽  
Wear Resistance ◽  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Coefficient Of Friction ◽  
Loading Conditions ◽  
Severe Loading

Abstract ToughMet 2 CX is a Cu-9Ni-6Sn alloy that combines low coefficient of friction with wear resistance. ToughMet alloys are a line of spinodal hardened Cu-Ni antigalling alloys for bearings capable of performing with a variety of shafting materials and lubricants. The alloys combine a high lubricity with wear resistance in these severe loading conditions. ToughMet 2CX in the cast and spinodally hardened (CX) condition exhibits tensile strength in excess of 724 MPa (105 ksi) and hardness exceeding HRC 27 with excellent machinability. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming. Filing Code: Cu-819. Producer or source: Materion Brush Performance Alloys.

Position-Mode Haptic-Based Control of Teleoperated Hydraulic Actuators

2011 ◽  
Author(s):  
Kurosh Zarei-nia ◽  
Nariman Sepehri
Keyword(s):  
Invariant Set ◽  
Haptic Device ◽  
Position Tracking ◽  
Good Position ◽  
View Point ◽  
Hydraulic Actuator ◽  
Control Laws ◽  
Hydraulic Actuators ◽  
Control Scheme ◽  
On Line

A control scheme for teleoperation of hydraulic actuators, using a haptic device, is developed and experimentally evaluated in this paper. In the control laws, the position error between the displacement of the haptic device and the hydraulic actuator movement is used at both master and slave sides to maintain good position tracking at the actuator side while providing a haptic force to the operator. Lyapunov’s stability theory and LaSalle’s invariant set theorems are employed to prove the asymptotic stability of the system. It is shown that beside stability, the system performs well in terms of position tracking of the hydraulic actuator and providing a feel of telepresence to the operator. Proposed controller only needs system’s pressures and displacements that are easy to obtain via on-line measurements. Additionally, the controller does not need any information about the parameters of the system. These characteristics make the controller very attractive from the implementation view point.

scholarly journals Active Disturbance Rejection Position Synchronous Control of Dual-Hydraulic Actuators with Unknown Dead-Zones

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6124
Author(s):  
Lixin Wang ◽  
Dingxuan Zhao ◽  
Fucai Liu ◽  
Qian Liu ◽  
Zhuxin Zhang
Keyword(s):  
Disturbance Rejection ◽  
Position Control ◽  
Dead Zone ◽  
Lyapunov Theory ◽  
Least Square ◽  
Synchronization Control ◽  
Hydraulic Actuator ◽  
Dead Zones ◽  
Hydraulic Actuators ◽  
Active Disturbance Rejection

In this paper, an integrated control strategy of position synchronization control for dual-electro-hydraulic actuators with unknown dead-zones is proposed. The unified control scheme consists of two parts: One is adaptive dead-zone inverse controllers of each hydraulic actuator to offset the unknown dead-zones. The other is the linear active disturbance rejection controller (LADRC) for position synchronization error. First, the model of the electro-hydraulic proportional position control system (EPPS) was identified by the forgetting factor recursive least square (FFRLS) algorithm. Next, the model reference dead-zone inverse adaptive controller (MRDIAC) was developed to compensate for the delay of actuator response caused by unknown proportional valve dead-zones. Meanwhile, the validity of the adaptive law was proven by the Lyapunov theory. Therefore, the position control accuracy of each hydraulic actuator is guaranteed. Besides, to improve the precision of position synchronization control of dual-hydraulic actuators, a simple and elegant synchronous error-based LADRC was adopted, which applies the total disturbances design concept to eliminate and compensate for motion coupling rather than cross-coupling technology. The performance of the proposed control solution was investigated through extensive comparative experiments based on a hydraulic test platform. The experimental results successfully demonstrate the effectiveness and practicality of the proposed method.

scholarly journals A Review on the Control Parameters of Natural Convection in Different Shaped Cavities with and without Nanofluid

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1011 ◽  
Author(s):  
Sara Rostami ◽  
Saeed Aghakhani ◽  
Ahmad Hajatzadeh Pordanjani ◽  
Masoud Afrand ◽  
Goshtasp Cheraghian ◽  
...  
Keyword(s):  
Porous Media ◽  
Natural Convection ◽  
Free Convection ◽  
Forced Convection ◽  
Opposite Effect ◽  
Fluid Velocity ◽  
Experimental Studies ◽  
Effective Parameters ◽  
Magnetic Forces ◽  
Numerical Studies

Natural convection in cavities is an interesting subject for many researchers. Especially, in recent years, the number of articles written in this regard has grown enormously. This work provides a review of recent natural convection studies. At first, experimental studies were reviewed and, then, numerical studies were examined. Then, the articles were classified based on effective parameters. In each section, numerical studies were examined the parameters added to the cavity such as magnetic forces, fin, porous media and cavity angles. Moreover, studies on non-rectangular cavities were investigated. Free convection in enclosures depends more on the fluid velocity relative to the forced convection, leading to the opposite effect of some parameters that should essentially enhance rate of heat transfer. Nanoparticle addition, magnetic fields, fins, and porous media may increase forced convection. However, they can reduce free convection due to the reduction in fluid velocity. Thus, these parameters need more precision and sometimes need the optimization of effective parameters.

Asymptotic Impact Control of Hydraulic Actuators With Friction

2004 ◽  
Author(s):  
P. Sekhavat ◽  
N. Sepehri ◽  
Q. Wu
Keyword(s):  
Steady State ◽  
Nonlinear Control ◽  
Dry Friction ◽  
Position Control ◽  
Past Research ◽  
Hydraulic Actuator ◽  
Stick Slip ◽  
Hydraulic Actuators ◽  
Control Scheme ◽  
Control Schemes

The focus of this work is stabilization of hydraulic actuators during the transition from free motion to constraint motion and regulating the intermediate impacts that could drive the system unstable. In our past research, we introduced Lyapunov-based nonlinear control schemes capable of fulfilling the above goal by resting the implement on the surface of the environment before starting the sustained-contact motion. The hydraulic actuator’s stick-slip friction effect was, however, either not included in the analysis or not compensated by the control action. In this paper, the application of our previously introduced friction compensating position control scheme is extended to impact regulation of a hydraulic actuator. Theoretical solution and stability analyses as well as actual experiments prove that such control scheme is also effective for asymptotic impact control (with no position steady-state error) of hydraulic actuators in the presence of actuator’s dry friction.

Fatigue Analysis of Pure Waterjet Nozzle-A CFD and FEA Approach

2011 ◽  
Vol 328-330 ◽  
pp. 1359-1364
Author(s):  
Quan Chang Li ◽  
Kai He ◽  
Ru Xu Du
Keyword(s):  
Stress Distribution ◽  
Fatigue Failure ◽  
Equivalent Stress ◽  
Element Analysis ◽  
Cavitation Damage ◽  
Theoretical Predictions ◽  
Incremental Sheet Metal Forming ◽  
Failure Point ◽  
Computational Fluid Dynamics Cfd ◽  
Velocity Pressure

The utilization of pure waterjet for Incremental Sheet Metal Forming (ISMF) is growing. However, the fatigue of pure waterjet nozzle is not fully clear. In the current study, based on the computational fluid dynamics (CFD) and finite element analysis (FEA), the fatigue failure of pure waterjet nozzle was simulated and analyzed. The influence of uneven equivalent stress distribution and generation of cavitation on nozzle fatigue failure was discussed. The results obtained from two simulations (velocity, pressure) show a good agreement with the theoretical predictions, which indicates that the approach based on CFD and FEA is absolutely feasible. Due to the uneven equivalent stress distribution, there is the first failure point inside the nozzle, which reduces the whole life of the nozzle. The unreasonable nozzle structure is one of main causes of cavitation generation; cavitation damage is reduced by optimizing the structure to improve the overall life of the nozzle.

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