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Landstown High School Governors STEM & Technology Academy Advanced Robotics Chapter 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. © Goodheart-Willcox Co., Inc. Fluid Power Systems • All fluid power systems consist of: – Controls, – An energy source, – A transmission path, – A load, – Indicators, © Goodheart-Willcox Co., Inc. 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, © Goodheart-Willcox Co., Inc. Hydraulic System Model • 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. © Goodheart-Willcox Co., Inc. Basic Hydraulic System LS 6-1 © Goodheart-Willcox Co., Inc. Hydraulic System Model • 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. © Goodheart-Willcox Co., Inc. Hydraulic Control Devices LS 6-2 © Goodheart-Willcox Co., Inc. 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. © Goodheart-Willcox Co., Inc. Pneumatic System LS 6-3 © Goodheart-Willcox Co., Inc. 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, © Goodheart-Willcox Co., Inc. 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. © Goodheart-Willcox Co., Inc. 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. © Goodheart-Willcox Co., Inc. Pressure Drops in a Fluid System LS 6-4 © Goodheart-Willcox Co., Inc. 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. © Goodheart-Willcox Co., Inc. 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. © Goodheart-Willcox Co., Inc. Pascal’s Law LS 6-5 © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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). © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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. © Goodheart-Willcox Co., Inc. Fluid Pumps LS 6-6 © Goodheart-Willcox Co., Inc. Principles of Fluid Power • Examples – – – – Reciprocating pumps- Positive displacement, Rotary Gear Pumps- positive displacement, Rotary Vane Pumps- positive displacement, Centrifugal pumps- non-positive displacement, © Goodheart-Willcox Co., Inc. Operation of a Reciprocating Pump LS 6-7 © Goodheart-Willcox Co., Inc. Rotary Gear Pumps LS 6-8 © Goodheart-Willcox Co., Inc. Rotary Vane Pump LS 6-9 © Goodheart-Willcox Co., Inc. Centrifugal Pumps LS 6-10 © Goodheart-Willcox Co., Inc. Pressure Regulator Valve Operation LS 6-11 © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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. © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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. © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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. © Goodheart-Willcox Co., Inc. FRL Unit LS 6-12 © Goodheart-Willcox Co., Inc. 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 © Goodheart-Willcox Co., Inc. Fluid Check Valve (Pressure Control) LS 6-13 © Goodheart-Willcox Co., Inc. Four-way Valve (Flow Control) LS 6-15 © Goodheart-Willcox Co., Inc. Flow Control Valve Operation (Direction Control) LS 6-16 © Goodheart-Willcox Co., Inc. Principles of Fluid Power • Load Devices – The term actuator is often used to identify the load device. • Linear Actuators • Rotary Actuators • Fluid Motors © Goodheart-Willcox Co., Inc. Linear Actuator LS 6-17 © Goodheart-Willcox Co., Inc. Rotary Actuators LS 6-20 © Goodheart-Willcox Co., Inc. Principles of Fluid Power • 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, © Goodheart-Willcox Co., Inc.