landstown high school governors stem & technology academy advanced robotics chapter 6- fluid...

Landstown High School Governors STEM & Technology Academy

Advanced RoboticsChapter 6- Fluid Power Systems

Dr. Barger

Fluid Power Systems

• Fluid power systems use air or liquid, or a combination of both, to transfer power.

© Goodheart-Willcox Co., Inc.

Fluid Power Systems

• Transfer Methods– Electrical energy is often used to drive a fluid

pump.– Electrical energy and mechanical motion are

converted into the energy of a flowing liquid.• Hydraulic systems use oil, or other liquids, while

pneumatic systems use air.


Fluid Power Systems

• All fluid power systems consist of:– Controls,– An energy source,– A transmission path,– A load,– Indicators,


Hydraulic System Model

• Hydraulic Systems are used for many applications in Robotics:– Operates motors,– Actuators,– Cylinders (load devices)

• Usally electrical energy drives a pump which provides hydraulic pressure,



• Prime Mover system– A prime mover is a component of a power

system that provides the initial power for movement in the system,,

– The motor receives electrical energy from the source and converts it to rotary energy or movement.

– The pump converts the rotary energy into fluid energy.


Basic Hydraulic System


LS 6-1



• Control Systems– A typical hydraulic fluid power system includes

a number of control devices,• Directional control valve (DCV) (cylinders),• Pressure relief valves,

– A pressure relief valve is a control device that protects the system from stress and damage caused by over pressurizing the system.

Hydraulic Control Devices


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Pneumatic System Model


• In a typical pneumatic system, the energy source powers a compressor which forces air into a pressurized storage tank.– The compressor is most often driven by an electric motor, or

internal combustion engine.– The storage tank hold the pressurized air and acts as a reservoir

for the system.– Typical uses are for:

• Power tools, and• Lifting and clamping during machining operations.

Pneumatic System


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Characteristics of Fluid Flow


• Fluid power systems do not achieve 100 percent power transfer,– Due to friction from the cylinder walls,– This friction is known as “resistance” or power

loss,– Power loss materializes primarily as heat,

Pneumatic Systems


• Turbulence– Refers to how the fluid moves through the fluid

power system.• Conditions of the system, such as:

– size and smoothness of the tubing walls,– Location and number of valves and fittings,

may cause irregular flow characteristics.

Pneumatic Systems


• Pressure drops– Restrictions within the system are also a source of

pressure drops.• These can be caused by:

– Control valves, tubing length, or small tubing size

• Energy Loss– As fluid pressure enters the system, it has the ability to

perform a specific amount of work. – Fluid energy is lost because it is changed into heat due

to friction and resistance.

Pressure Drops in a Fluid System


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Pneumatic Systems


• Compression of Fluids– A notable difference between hydraulic and

pneumatic systems is the compressibility of the fluids,

• All gases and liquids are compressible under certain conditions for each,

– Hydraulic fluid is considered incompressible,– Air in pneumatic systems is readily compressible.

Principles of Fluid Power


• Pascal’s Law– Pressure applied to a confined fluid is

transmitted, undiminished, throughout the fluid.

• This pressure acts on all surfaces of the container, at right angles to those surfaces,

• For this reason, the walls of the cylinder must be strong enough to withstand the pressure.

Pascal’s Law


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• Terminology– Force

• Is any factor that tends to produce or modify the motion of an object.

– Inertia- the amount of force needed to produce motion (or resistance to change) of the body to be moved.

– Pressure• Is the amount of force applied to a specific area.

Usally in pounds per square inch (psi).



• Fluid Power System Components– Fluid Pumps

• The heart of a fluid system. It provides an appropriate flow to develop pressure.

• Two general classifications:– Positive displacement pump,

» Has a close clearance between the moving member and stationary pump components,

– Non-Positive displacement pump» The fluid is moved by the impeller blades during each

revolution.

Fluid Pumps


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• Examples– Reciprocating pumps- Positive displacement,– Rotary Gear Pumps- positive displacement,– Rotary Vane Pumps- positive displacement,– Centrifugal pumps- non-positive displacement,

Operation of a Reciprocating Pump


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Rotary Gear Pumps


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Rotary Vane Pump


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Centrifugal Pumps


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Pressure Regulator Valve Operation


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• Fluid Conditioning Devices– Both hydraulic fluid and air must be

conditioned before being processed through a fluid power system.

– Conditioning devices prolong the life of fluid power systems by removing foreign particles and moisture.



• Hydraulic Conditioning– The number of components, types of control devices and

operating environment are major considerations in hydraulic fluid conditioning.

– Types used:• Strainers- Inline devices,• Filters- Inline device,• Heat exchangers-

– Forced-air fans,– Water-jacket coolers,– Gas coolers.



• Pneumatic Conditioning– Several types of devices are used but the most often is a filtering

device,• Filters

– Filtering must remove moisture and foreign particles, so they contain “desiccant”, which is a very dry material designed to attract moisture,

• Lubricators– Lubricators are devices that add a small quantity of oil to the air

after it leaves the regulator. The lubrication helps the valves and cylinders operate more efficiently.

FRL Unit


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Fluid Power Systems


• Control Devices– Control is achieved by devices that alter the

pressure, direction and volume of fluid flow.• Pressure Control• Flow Control• Direction Control

Fluid Check Valve(Pressure Control)


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Four-way Valve(Flow Control)


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Flow Control Valve Operation(Direction Control)


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• Load Devices– The term actuator is often used to identify the

load device. • Linear Actuators• Rotary Actuators• Fluid Motors

Linear Actuator


LS 6-17

Rotary Actuators


LS 6-20



• Hybrid Systems– A number of industrial systems produce

mechanical energy by combining fluid power and electrical power systems.

– Example:• Hoists use in car repair operations,

landstown high school governors stem & technology academy advanced robotics chapter 6- fluid...

Documents

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