Ultrasonic Motor Powerpoint pdf


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Ultrasonic Motor Powerpoint pdf

  2. 2. MOTOR • Device that converts electrical energy to mechanical energy. • ELECTROMAGNETIC MOTORS  Current carrying conductor kept in a magnetic field experiences a force or torque (Faraday’s law of EMI).  Electrical energy Magnetic energy Mechanical energy
  3. 3. Drawbacks of Electromagnetic Motors • Noisy operation. • Surge currents and spikes. • Electromagnetic interference. • Magnetic losses (Eddy currents & Hysteresis). • High power consumption & high temperature. • Low power factor. • Comparatively lesser efficiency.
  4. 4. ULTRASONIC MOTOR (USM) • A pressure applied across a pair of opposite faces of a crystal, results in a PD developed across the other pair. PIEZOELECTRIC EFFECT + + + + + + + + _ _ _ _ _ _ _ _ Mechanical Pressure Mechanical Pressure Potential Difference
  5. 5. • When an AC is applied across a pair of opposite faces, alternating compressions and elongations (mechanical vibrations) are obtained across the other pair of opposite faces. • As a result, a surface wave is formed over the crystal driving force of the USM Working Principle : CONVERSE PIEZOELECTRIC EFFECT
  6. 6. Construction • ACTUATOR  A piezoelectric material (Quartz, Barium Titanate, Tourmaline, Rochelle Salt) is used as actuator.  Actuator is fixed on the stator using thin metal sheets and bearings.  Actuator is directly connected to the supply mains. • STATOR  Stator is made of any malleable material Steel.  Ring, Cylindrical or Rod shaped. Contd…
  7. 7. • ROTOR  Same material as that of the stator.  Same shape as that of the stator(Ring, Cylindrical or Rod).  Frictional coupling. • CASING  Cylindrical, Disc or Box shaped.  Non- corrosive alloys or Fiber.  To provide protection against abrasion & external interferences. Contd…
  8. 8. Working
  9. 9. Linear USM with double stators Stator StatorRotor Actuator Actuator
  10. 10. Coupling of Rotor & Stator • Surface of contact b/w rotor & stator is made uneven, so that they never slip off frictional coupling. • During motion, rotor is levitated from the stator in the perpendicular direction less wear & tear. • Care is to be taken that friction doesn't cause the interlocking of rotor & stator.
  11. 11. Types of USM • Travelling Wave type If the wave produced in the stator causes the particles to experience both horizontal and vertical movement. Produced by double actuators. • Standing Wave type If the wave produced in the stator causes the particles to experience only vertical movement. Single actuator is required. NB: Both these types of USMs has got the same construction and working principles, however the Travelling Wave type USMs are found to have better operating characteristics.
  12. 12. Advantages & Disadvantages Advantages • High o/p torque & efficiency. • High power to weight ratio. • Good positioning accuracy. • Capable of working in extreme environmental conditions. • No magnetic interference. • Simple construction. • Small size, light weight, less noise. Disadvantages • Requires high frequency power supply(kHz range). • Piezoelectric material is expensive. • Ultrasonic noise occurs. • Drooping torque-speed characteristics.
  13. 13. Applications • Auto focusing & optical zooming in digital cameras & surveillance cameras. • Wrist watches & Clocks. • Power steering, Power windows, Tilt steering, ORVM, Car seat adjustment etc. • Robotics. • Aerospace. • Medicine • Hardware positioning (Hard disks, Floppy & CD Drives) etc.
  14. 14. Conclusion The above mentioned advantages and applications, concludes the scope of USMs in the day-to-day life. However the disadvantages brings up the need for further researches in the field.
  15. 15. Additional Info • Piezoelectric effect was discovered by Jacques Curie & Pierre Curie [France-1880]. • 1st Ultrasonic Motor was developed by V V Lavrinenko [Russia-1965].
  16. 16. THE END