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Gyroscopes

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Title: ECE5320 Assignment#1 Subject: sensor and actuator PPT template Author: YangQuan Chen Last modified by: Eric Ruben Created Date: 12/2/2003 5:03:49 PM – PowerPoint PPT presentation

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Title: Gyroscopes


1
Gyroscopes
Eric Ruben Mechatronics Literature Survey Dept.
of Electrical and Computer Engineering Utah
State University E e.r_at_aggiemail.usu.edu T
801-916-2400
2/17/2009
2
Outline
  • Introduction
  • History
  • Basic Principle
  • Applications
  • Advantages
  • Disadvantages
  • Cost
  • Works Cited

3
Introduction
  • Most everyone has used some form of gyroscope in
    their lifetime. But perhaps they did not
    recognize it.
  • Simply put, a gyroscope consists of a rotor that
    is journaled to spin about an axis. Often the
    spinning rotor is gimbaled and allowed to move
    freely. This spinning rotor has some very useful
    physical properties.
  • One of these properties can even be seen in a
    simple 7 gyroscope toy. That is, when a rotor
    spins about an axis, that axis tends to want to
    maintain its spacial orientation.

4
Introduction
  • A second important property of gyroscopes can be
    observed from the common Bicycle Wheel Gyro
    experiment.
  • In the experiment a person sits in a pivoting
    office chair while holding a spinning bicycle
    wheel.
  • As the person tilts the spin axis to the left a
    seemingly invisible force begins to pivot his/her
    chair to the left.
  • This action is a result of a property called
    precession. This property will be discussed in
    greater detail later.

5
History
  • 1817. Johann Bohnenberger created the first know
    gyroscope, calling it simply the machine.
  • 1820. Pierre-Simon Laplace recommended the
    machine be used as a teaching aide.
  • 1852. Leon Foucault coins the name gyroscope
    when he uses Bohnenbergers machine in an
    experiment involving the earths rotation.
  • 1905 1908. The first gyroscope for marine
    navigation was developed by German inventor
    Hermann Anschutz-Kaempfe.

6
History
  • 1917. The Chandler gyroscope toy was invented
    by the Chandler Company in Indiana. It is still
    considered a classic American toy.
  • 1991. Charles Stark Draper Laboratory
    demostrated one of the first MEMS or Vibratory
    gyroscopes fabricated in silicon.

7
Basic Principle
  • Gyroscopes operate on a physical property of
    spinning objects known as precession.
  • Precession is the phenomenon observed in the
    bicycle wheel experiment. If an input force is
    applied against the spin axis the wheel will
    resist it by generating an output force
    perpendicular and proportional to the input.

8
Basic Principle
  • Precession is an interesting property of
    gyroscopes. But how can it be used to create
    useful sensors?
  • Gyroscopes can be used to measure orientation,
    tilt (gravity), and external force. Gyroscopes
    are also used to determine the position of a body
    in space, but this often requires the integration
    of additional sensors like accelerometers.
  • Some of the more common applications of
    gyroscopes will be discussed here in greater
    detail.

9
Basic Principle
  • Gimbals can be used to provide the spinning rotor
    with additional degrees of freedom.
  • The gyroscope shown here has both an inner and
    outer gimbal, allowing the rotor to pivot about 2
    different axis.
  • This is knows as a two degree-of-freedom (2DOF)
    gyroscope.

10
Basic Principle
  • Interestingly, If a 2 DOF gyroscope rotor is left
    spinning with a spin axis orientation other than
    the north celestial pole, the spin axis will
    appear to us on Earth to have rotated every 24
    hours.
  • This is due to the law of conservation of angular
    momentum.

11
Applications
Gyroscopic sensing is an older technology that is
continually finding new uses. Some or the more
typical applications include
  • Naval navigation systems and stabilizers.
  • Aircraft attitude controllers and stabilizers.
  • Inertial guidance systems for ballistic missiles.
  • Video game controllers.
  • Image stabilization systems on video cameras.

12
Gyrocompasses
  • Gyrocompasses use a spinning rotor to locate true
    north, however, an additional torque is needed
    to offset forces exerted by the Earths rotation
    (discussed earlier).
  • Using weights is the most practical method for
    providing the offset torque. Weights force the
    axis of rotation to remain horizontal with
    respect to the earths surface. Being thus
    constrained the gyroscope continually realigns
    itself, pointing towards true north.

13
Inertial Navigation Systems
  • Most sophisticated aircraft and missile systems
    use INS to determine their location and
    orientation.
  • The gyroscope sensor is only one component of the
    INS but it is very important. It provides
    information about the plants orientation.
  • Combining orientation information with data
    collected from accelerometers an onboard computer
    can determine the objects location.

14
Inclinometers
  • Gyroscopes are used extensively in land, air and
    sea vehicles to take high precision tilt
    measurements, much like inertial navigation
    systems only without the accelerometers.
  • An good example would be an aircraft that uses 3
    gyroscopes to measure the pitch, roll and yaw.

15
MEMS Gyroscopes
  • The size, accuracy and cost of MEMS gyroscopes
    makes them an attractive option for many
    applications.
  • One common type of MEMS gyroscope is the
    vibrating wheel gyroscope. Vibrating wheels
    operate much like the macroscopic spinning wheel
    gyroscope but use capacitive sensors to determine
    changes in attitude.
  • The drawing to the right shows a vibrating wheel
    gyroscope with a z direction spin axis.

16
Advantages
  • Most MEMS gyroscopes are extremely small,
    lightweight, and inexpensive.
  • Sensor resolution depends largely on the spin
    rate of the rotor and can be much higher than
    other force, or tilt sensors.
  • A gyrocompass, unlike a magnetic compass,
    indicates true north as opposed to magnetic
    north. This makes gyroscopes the preferred
    sensor for high precision navigation systems.

17
Disadvantages
  • In general, gyroscopes are a more expensive
    alternative to navigation and tilt sensing.
  • A free moving gyroscope is always dependant on
    the rotation of the Earth. For this reason fast
    moving objects moving on a trajectory from east
    to west cannot use gyroscopes for navigation.

18
Cost
  • Most applications today use MEMs gyroscopes
    because they are small and relatively
    inexpensive. Here is a comparison of some
    expensive and inexpensive ones

Part Range Sensitivity Supply Current Price
ADXRS610 /- 300 deg/s 6 mV/degs 3.5mA 19.98
ADXRS150 /- 150 deg/s 12.5 mV/degs 6mA 30.36
ADIS6255 /- 80 deg/s .018 deg/secLSB 18mA 56.57
ADIS16120 /- 300 deg/s .2 deg/secmV 95mA 636.55
19
Future Work
  • Most development being done in gyroscopes as
    sensors is focused on reducing the size and
    improving the precision of MEMS gyroscopes.
  • Much of this research is fueled by DARPA and the
    military. The goal is to produce a small, light
    weight, and inexpensive 6-axis Inertial

20
Works Cited
  • Analog Devices. (2009). iMEMS Gyroscopes.
    Retrieved February 15, 2009, from Analog Devices
    http//www.analog.com/en/mems-and-sensors/imems-gy
    roscopes/products/index.html
  • Conventor. (2008, February). Gyroscope
    Application Examples. Retrieved February 15,
    2009, from Conventor http//www.coventor.com/pdfs
    /Gyro_Applications.pdf
  • Kaumualii High School. (2004). Bicycle Wheel
    Gyro. Retrieved February 14, 2009, from Kaumualii
    High http//www.kaumualii.k12.hi.us/technology/sc
    ience/pdf/forces/Bicycle20Wheel20Gyro.pdf

21
Works Cited
  • muRata. (2007). Piezoelectric Vibrating
    Gyroscopes. Retrieved February 15, 2009, from
    Gyrostar http//www.murata.com/catalog/s42e.pdf
  • Nasiri, S. (2006, July). A Critical Review of
    MEMS Gyroscopes Technology and Commercialization
    Status. Retrieved Feb 15, 2009, from InvenSense
    http//www.invensense.com/shared/pdf/MEMSGyroComp.
    pdf
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