Actuation Systems Chapter
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Questions and Answers

What is the primary function of actuation systems?

  • To provide power to a machine or device
  • To transform output from a microprocessor into a controlling action (correct)
  • To interpret system drawings
  • To process information in a control system

    • What is a disadvantage of hydraulic systems compared to pneumatic systems?

  • Higher cost (correct)
  • More complex design
  • Lower power control
  • Less hazardous

    • What is the purpose of an accumulator in a hydraulic system?

  • To pump oil from a sump
  • To smooth out short-term fluctuations in oil pressure (correct)
  • To drive an electric motor
  • To increase oil pressure

    • What type of pump is used to provide pressurized oil in a hydraulic system?

    <p>Gear pump</p> Signup and view all the answers

    What is a common type of hydraulic pump?

    <p>All of the above</p> Signup and view all the answers

    What is the source of power for a hydraulic pump?

    <p>Electric motor</p> Signup and view all the answers

    What is a potential hazard associated with hydraulic systems?

    <p>Oil leaks</p> Signup and view all the answers

    What is the purpose of a non-return valve in a hydraulic system?

    <p>To prevent backflow of oil</p> Signup and view all the answers

    What is a characteristic of servo valves?

    <p>Accurate position control</p> Signup and view all the answers

    What type of system is a servo valve often used in?

    <p>Closed-loop control system</p> Signup and view all the answers

    What is the advantage of servo valves in hydraulic systems?

    <p>Higher reliability</p> Signup and view all the answers

    What is a characteristic of proportional control valves?

    <p>Less expensive</p> Signup and view all the answers

    What is the purpose of process control valves?

    <p>To control the rate of fluid flow</p> Signup and view all the answers

    What is a characteristic of servo valves in terms of flow?

    <p>It can give a continuous variation of flow</p> Signup and view all the answers

    What is a characteristic of servo valves in terms of responsiveness?

    <p>Highly responsive</p> Signup and view all the answers

    What is a characteristic of servo valves in terms of repeatability?

    <p>High repeatability</p> Signup and view all the answers

    What happens to a transistor when the input voltage is sufficiently high?

    <p>Very little of the VCC voltage appears at the output</p> Signup and view all the answers

    What is the voltage called that is applied to the base of an NPN transistor?

    <p>VBE</p> Signup and view all the answers

    What is the purpose of making the collector more positive than the emitter in an NPN transistor?

    <p>To allow the transistor to function</p> Signup and view all the answers

    What is the main advantage of using a Darlington pair configuration?

    <p>It is used for higher power requirements or more amplification</p> Signup and view all the answers

    What does a MOSFET stand for?

    <p>Metal-Oxide-Semiconductor Field-Effect Transistor</p> Signup and view all the answers

    What is one of the functions of a MOSFET?

    <p>To switch a circuit on and off based on voltage</p> Signup and view all the answers

    What is the purpose of a MOSFET in electronic devices?

    <p>To act as an electronic switch and amplify signals</p> Signup and view all the answers

    What is the typical application of a MOSFET?

    <p>In modern electronic devices</p> Signup and view all the answers

    What is the basic principle of operation of a 2-way ball valve?

    <p>The ball is rotated 90 degrees to open and close the valve.</p> Signup and view all the answers

    What is the purpose of the seats in a 2-way ball valve?

    <p>To lead the inlet and outlet of the fluid flow.</p> Signup and view all the answers

    What is unique about the obstructer in a butterfly valve?

    <p>It is a thin disc.</p> Signup and view all the answers

    What is the advantage of butterfly valves compared to ball and plug valves?

    <p>They are lighter and less expensive.</p> Signup and view all the answers

    What is the primary use of butterfly valves?

    <p>As a basic on/off valve.</p> Signup and view all the answers

    In what position is the flow of fluid completely blocked in a butterfly valve?

    <p>When the disc is perpendicular to the flow.</p> Signup and view all the answers

    What is the primary function of finite position valves?

    <p>To switch actuators on or off</p> Signup and view all the answers

    What is the main characteristic of infinite position valves?

    <p>They can control flow anywhere between fully on and fully off</p> Signup and view all the answers

    What is the primary function of directional control valves?

    <p>To direct the flow of fluid through a system</p> Signup and view all the answers

    What is a common type of directional control valve?

    <p>Spool valve</p> Signup and view all the answers

    What is the normal condition of a poppet valve?

    <p>Normally closed</p> Signup and view all the answers

    What do arrow-headed lines indicate in valve symbols?

    <p>The direction of flow in each position</p> Signup and view all the answers

    What do blocked-off lines indicate in valve symbols?

    <p>Closed flow lines</p> Signup and view all the answers

    What is the label for the pressure supply port in valve symbols?

    <p>1 or P</p> Signup and view all the answers

    Study Notes

    Actuation Systems

    • Actuation systems transform the output of a microprocessor or control system into a controlling action on a machine or device.

    Hydraulic Systems

    • Hydraulic systems can be used for high-power control devices but are more expensive than pneumatic systems and have hazards associated with oil leaks.
    • Pressurized oil is provided by a pump driven by an electric motor, and an accumulator smooths out short-term fluctuations in output oil pressure.
    • Commonly used hydraulic pumps include gear pumps, vane pumps, and piston pumps.

    Directional Control Valves

    • Directional control valves are used to direct the flow of fluid through a system in pneumatic and hydraulic systems.
    • Common types of directional control valves include spool valves and poppet valves.
    • Valve symbols use arrow-headed lines to indicate flow directions, with blocked-off lines indicating closed flow lines.

    Servo and Proportional Control

    • Servo valves are capable of infinitely variable positioning and controlling the direction and amount of flow.
    • They have internal feedback for better valve operation with high reliability.
    • Proportional control valves are less expensive and have the spool position directly controlled by the size of the current to the valve solenoid.
    • Characteristics of servo valves include:
      • Higher oil capacity
      • Accurate position control
      • Closed-loop control system
      • Continuous variation of flow with changing input signal
      • Highly responsive
      • High repeatability
      • High frequency response
      • Perfect flow changes handling

    Process Control Valves

    • Process control valves control the rate of fluid flow and are used in applications such as controlling the rate of flow of a liquid into a tank.
    • 2-way ball valves are extremely common and simple in design, with a ball that rotates to open or block the flow.
    • 3-way ball valves are also available.

    Butterfly Valves

    • Butterfly valves operate by rotating an obstructer 90 degrees from open to closed position.
    • The obstructer is a thin disc that turns sideways to open, and the flow travels around the disc when rotated 90 degrees.
    • These valves are commonly used as basic on/off valves, but are also suited for proportional flow control by stopping the disc at intermediate positions.

    Transistors

    • NPN BJT (Bipolar Junction Transistor) has a collector, emitter, and base.
    • When a voltage is applied to the base, the transistor turns on, allowing current to flow from the collector to the emitter.
    • Darlington pair configuration is used for higher power requirements or when more amplification is needed.

    MOSFETs

    • A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a type of transistor widely used in electronics for switching and amplifying signals.
    • Functionality includes switching (turning a circuit on and off) and amplification (controlling the flow of current between the drain and source terminals).

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    Description

    This chapter covers the basics of actuation systems, including interpretation and design of sequential control systems, hydraulic and pneumatic directional control valves, and cylinders, as well as process control valves and their characteristics.

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