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Title
Abstract
FAQs
Figures
Introduction 1.OVERVIEW
Introduction
Hydraulic Circuit Analysis
References

Fluid Power System Dynamics

Profile image of Jesus OrtizJesus Ortiz

Abstract
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AI

Fluid power systems utilize confined, pressurized fluids for the transmission of forces and motion, primarily employing oil in hydraulic systems and air in pneumatic configurations. This technology excels in applications requiring high power density, precision, and rapid response times. However, fluid power systems come with challenges such as leakage, noise, complexity in modeling, and contamination risks. The paper discusses various examples of fluid power applications from industrial machinery to precision tools, emphasizing ongoing research aimed at enhancing performance and expanding application areas.

FAQs

sparkles

AI

What explains the efficiency differences between hydraulic and pneumatic systems?add

Hydraulic systems typically exhibit higher efficiencies than pneumatic systems due to the incompressibility of liquids, resulting in reduced energy losses during operation.

How do bulk modulus variations affect hydraulic system performance?add

The bulk modulus of typical hydraulic oils ranges between 2×10^5 to 3×10^5 psi, and variations can significantly impact the responsiveness and stability of hydraulic control systems.

What role do control valves serve in fluid power systems?add

Control valves govern fluid flow and pressure in hydraulic systems, and their position directly influences the operational efficiency and effectiveness of pneumatic and hydraulic actuation.

When did innovations in pneumatic control theory emerge for precision control?add

Recent advancements in pneumatic control theory have opened new applications for precision control, as reported in Popular Mechanics in March 2007.

How does diameter affect force output in hydraulic cylinders?add

Force output from hydraulic cylinders increases as the square of the bore diameter; for example, a shift from a 7/16 inch bore to a 4 inch bore significantly escalates pushing force.

Figures (42)
Figure 1.3.: MAST Laboratory for earthquake simulation. Source: MAST Lab.
Figure 1.3.: MAST Laboratory for earthquake simulation. Source: MAST Lab.
Figure 1.2.: 40,000 ton forging press. Source: Shultz Steel.
Figure 1.2.: 40,000 ton forging press. Source: Shultz Steel.
Figure 1.6.: Hypersonic XLC roller coaster with hydraulic lanuch assist. Source: Wikipedia image.
Figure 1.6.: Hypersonic XLC roller coaster with hydraulic lanuch assist. Source: Wikipedia image.
Figure 1.7.: Mercedes-Benz automatic transmission model.
Figure 1.7.: Mercedes-Benz automatic transmission model.
Figure 1.8.: A dental handpiece. Source: Wikipedia image.
Figure 1.8.: A dental handpiece. Source: Wikipedia image.
Figure 1.9.: Hydraulic microdrive for neural recording electrode placement. Source: Stoelting Co.
Figure 1.9.: Hydraulic microdrive for neural recording electrode placement. Source: Stoelting Co.
Table 1.1.: Element analogies in several domains.
Table 1.1.: Element analogies in several domains.
Table 2.1.: Conversions between pressure units Uilito, VU LY sae coisa Catt VE CALIMA ULI CULV ELI ad ian © auiimemanamei = Uilit. Pressure is an across type variable, which means that it is always measure with respect to a reference just like voltage in an electrical system. As show in Figure 2.1, one can talk about the pressure across a fluid power elemer such as a pump or a valve, which is the pressure differential from one sid to the other, but when describing the pressure at a point, for example th pressure of fluid at one point in a hose, it is always with respect to a referenc pressure. Reporting absolute pressure means that the pressure is measure with respect to a perfect vacuum. It is more common to measure and repo! gage pressure, the pressure relative to ambiant atmospheric pressure (0.1013 mPA, 14.7 psi at sea level). The distinction is critical when analyzing th dynamics of pneumatic systems because the ideal gas law that models th behavior of air is based on absolute pressure. eS ee a : ee ane i ne.
Table 2.1.: Conversions between pressure units Uilito, VU LY sae coisa Catt VE CALIMA ULI CULV ELI ad ian © auiimemanamei = Uilit. Pressure is an across type variable, which means that it is always measure with respect to a reference just like voltage in an electrical system. As show in Figure 2.1, one can talk about the pressure across a fluid power elemer such as a pump or a valve, which is the pressure differential from one sid to the other, but when describing the pressure at a point, for example th pressure of fluid at one point in a hose, it is always with respect to a referenc pressure. Reporting absolute pressure means that the pressure is measure with respect to a perfect vacuum. It is more common to measure and repo! gage pressure, the pressure relative to ambiant atmospheric pressure (0.1013 mPA, 14.7 psi at sea level). The distinction is critical when analyzing th dynamics of pneumatic systems because the ideal gas law that models th behavior of air is based on absolute pressure. eS ee a : ee ane i ne.
Figure 2.2.: Dial pressure gauge and electronic pressure transducer.
Figure 2.2.: Dial pressure gauge and electronic pressure transducer.
Table 2.2.: Conversions between volume flow rate units
Table 2.2.: Conversions between volume flow rate units
Figure 2.3.: Types of flowmeters. Top row: turbine, digital paddle, variable area. Bot- tom row is a dual-rotar turbine flowmeter with a cutaway.
Figure 2.3.: Types of flowmeters. Top row: turbine, digital paddle, variable area. Bot- tom row is a dual-rotar turbine flowmeter with a cutaway.
Figure 2.5.: The viscosity of hydraulic oils varies with temperature.
Figure 2.5.: The viscosity of hydraulic oils varies with temperature.
Figure 2.6.: Fluid bulk modulous. Liquids are nearly incompressible (left), except when there is trapped air, as shown on the right.
Figure 2.6.: Fluid bulk modulous. Liquids are nearly incompressible (left), except when there is trapped air, as shown on the right.
Figure 2.7.: Pascal’ Law. Fluid at rest has same pressure everywhere and acts at righ angles against the walls.
Figure 2.7.: Pascal’ Law. Fluid at rest has same pressure everywhere and acts at righ angles against the walls.
Figure 2.10.: Force in a cylinder acting at 60 psi. goes up with the square of the bore. Force can be increased two ways, raising the pressure or increasing the bore of the cylinder. Force is proportional to pressure but goes as the square of the bore, which means small increases in cylinder size results in large increases in force. For example, consider a small pneumatic cylinder with a 7/16 in. bore running at 60 psi. This cylinder can push with 9 lbs of force. But, as shown in Figure 2.10, force goes up as bore squared and a 4 in. bore cylinder at the same 60 psi can push with 754 lbs of force. Of course the extra force does not come free. A larger cylinder requires a ~aanainas en lana Attia 4a wenn La lASaA bhaw & eemal law Reelin aw Laem siivr!
Figure 2.10.: Force in a cylinder acting at 60 psi. goes up with the square of the bore. Force can be increased two ways, raising the pressure or increasing the bore of the cylinder. Force is proportional to pressure but goes as the square of the bore, which means small increases in cylinder size results in large increases in force. For example, consider a small pneumatic cylinder with a 7/16 in. bore running at 60 psi. This cylinder can push with 9 lbs of force. But, as shown in Figure 2.10, force goes up as bore squared and a 4 in. bore cylinder at the same 60 psi can push with 754 lbs of force. Of course the extra force does not come free. A larger cylinder requires a ~aanainas en lana Attia 4a wenn La lASaA bhaw & eemal law Reelin aw Laem siivr!
Figure 2.12.: Laminar and turbulent flow through a pipe.
Figure 2.12.: Laminar and turbulent flow through a pipe.
Figure 2.13.: Moody Diagram showing the experimental friction factor for pipes.
Figure 2.13.: Moody Diagram showing the experimental friction factor for pipes.
Solution: The Sun Hydraulics DAAA valve is a 2-position, 2-way cartridge valve. When the solenoid is energized the valve switches from blocking the flow to a fully open flow. The data sheet is at www.sunhydraulics.com. Some of the key valve specs are: Max flow = .25 gpm (1 L/m), Max pressure = 5000 psi (350 bar), Response time = 30 ms. The figure below shows a photo of the valve, the valve schematic and the experimental pressure vs. flow character- istics for the valve in its open position. These are cartridge valves, designed to screw into a manifold with the solenoid on top.
Solution: The Sun Hydraulics DAAA valve is a 2-position, 2-way cartridge valve. When the solenoid is energized the valve switches from blocking the flow to a fully open flow. The data sheet is at www.sunhydraulics.com. Some of the key valve specs are: Max flow = .25 gpm (1 L/m), Max pressure = 5000 psi (350 bar), Response time = 30 ms. The figure below shows a photo of the valve, the valve schematic and the experimental pressure vs. flow character- istics for the valve in its open position. These are cartridge valves, designed to screw into a manifold with the solenoid on top.
ylinders convert fluid power pressure and flow to mechanical translationa ower force and velocity (Fig. 3.1). Cylinders are linear actuators that cai ush and pull, and when mounted around a joint, for example, as is don 1 an ecavator, can actuate rotary motion. Cylinders come in single actin: oush only), single acting with spring return and double-acting (push-pull he rest of the section will focus on double acting cylinders, which are mos ommon in hydraulic applications. ! A cutaway illustration of a typical double-acting cylinder used for indus
ylinders convert fluid power pressure and flow to mechanical translationa ower force and velocity (Fig. 3.1). Cylinders are linear actuators that cai ush and pull, and when mounted around a joint, for example, as is don 1 an ecavator, can actuate rotary motion. Cylinders come in single actin: oush only), single acting with spring return and double-acting (push-pull he rest of the section will focus on double acting cylinders, which are mos ommon in hydraulic applications. ! A cutaway illustration of a typical double-acting cylinder used for indus
Figure 3.2.: Cut-away view of a welded body, industrial double-acting hydraulic cylinder. Source: Hyco International
Figure 3.2.: Cut-away view of a welded body, industrial double-acting hydraulic cylinder. Source: Hyco International
gure 3.5.: Pumps, motors and their schematic symbols. The difference between the two symbols is the direction that the triangle is pointing; out for pumps, in for motors
gure 3.5.: Pumps, motors and their schematic symbols. The difference between the two symbols is the direction that the triangle is pointing; out for pumps, in for motors
3.11.: (a) Pushbutton hydraulic 4/2 valve. In the nominal position, the cylin- der is held in the retracted postion because supply line P is connected to the rod side. When the button is pushed, the rod extends because supply line P is now connected to the cap side. When the button is released, the valve spring returns the valve to the nominal position, re- tracting the rod. (b) Solenoid 4/3 valve with center closed position and spring return to center. A computer can control extension and retraction of the cylinder by actuating the valve solenoids. (c) Same as b, but with a continuously variable proportional valve.
3.11.: (a) Pushbutton hydraulic 4/2 valve. In the nominal position, the cylin- der is held in the retracted postion because supply line P is connected to the rod side. When the button is pushed, the rod extends because supply line P is now connected to the cap side. When the button is released, the valve spring returns the valve to the nominal position, re- tracting the rod. (b) Solenoid 4/3 valve with center closed position and spring return to center. A computer can control extension and retraction of the cylinder by actuating the valve solenoids. (c) Same as b, but with a continuously variable proportional valve.
Figure 3.12.: Accumulator and ISO symbol. During use, hydraulic oil picks up contaminating particles from wear of slid- ing metallic surface that add to residual contaminants from the oil manufac- turing process, rust from metal and polymer particles from seal wear. These dirt particles are tiny grit that cause additional abrasive wear. Clumps of par- ticles can clog tiny clearances in precision valves and cylinders and can lead to corrosion.
Figure 3.12.: Accumulator and ISO symbol. During use, hydraulic oil picks up contaminating particles from wear of slid- ing metallic surface that add to residual contaminants from the oil manufac- turing process, rust from metal and polymer particles from seal wear. These dirt particles are tiny grit that cause additional abrasive wear. Clumps of par- ticles can clog tiny clearances in precision valves and cylinders and can lead to corrosion.
Figure 3.13.: Hydraulic filter and ISO symbol.
Figure 3.13.: Hydraulic filter and ISO symbol.
Figure 4.1.: A basic hydraulic circuit with fixed-displacement pump, pressure relief valve, 4/3 solenoid valve and cylinder. NN EEE Hydraulic circuit static and dynamic analysis involves first developing the appropriate mathematical models for each component in the circuit and then using Pascal’s Law (pressure same at all points for fluid at rest) and conserva- tion of flow to connect the components into a set of equations that describes the complete system. For a static analysis, the set of equations will be alge- braic while a dynamic analysis a set of differential equations. For example, the circuit shown in Figure 4.1 could be modeled as a constant
Figure 4.1.: A basic hydraulic circuit with fixed-displacement pump, pressure relief valve, 4/3 solenoid valve and cylinder. NN EEE Hydraulic circuit static and dynamic analysis involves first developing the appropriate mathematical models for each component in the circuit and then using Pascal’s Law (pressure same at all points for fluid at rest) and conserva- tion of flow to connect the components into a set of equations that describes the complete system. For a static analysis, the set of equations will be alge- braic while a dynamic analysis a set of differential equations. For example, the circuit shown in Figure 4.1 could be modeled as a constant

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with the details. Your claim will be investigated and, where appropriate, the item will be removed from public view as soon as possible.

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References (7)

  1. Bibliography
  2. Herbert Merritt, Hydraulic Control Systems. Wiley, 1967. The classic text on hydraulic control systems. Still useful.
  3. Noah Manring, Hydraulic Control Systems. Wiley, 2005. A modern rewrite of Merritt's text. Highly recommended.
  4. Eaton-Vickers, Industrial Hydraulics Manual. Eaton Corportation, 2001. A standard text for training fluid power technicians. Contains good,practical information. Used in the fluid power lab course at the University of Minnesota.
  5. Arthur Akers, Max Gassman and Richard Smith, Hydraulic Power System Analysis. Taylor & Francis, 2006. Good text on hydraulic system analysis.
  6. Lightning Reference Handbook. Berendsen Fluid Power Inc., 2001. Comprehensive reference information for hydraulics.
  7. Andrew Parr, Hydraulics and Pneumatics: A technician's and engineer's guide. Butterworth Heinemann, 1998. Good introductory overview of fluid power systems. http://www.hydraulicsupermarket.com/upload/db_documents_doc_19. pdf http://www.patchn.com/index.php?option=com_content&task=view&id= 31&Itemid=31 http://www.hydraulic-gear-pumps.com/pdf/Hydraulic\%20Symbols.pdf http://www.hydrastore.co.uk/products/Atos/P001.pdf http://www.scribd.com/doc/2881790/Fluid-Power-Graphic-Symbols

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