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ULTRASONIC MOTORS

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ULTRASONIC MOTORS

  1. 1. PREPARED BY-NAWNEET KUMAR (1100121058) EE,3rd year ULTRASONIC MOTORS
  2. 2. contents
  3. 3. • It has been known for more than 30 years. • The first ultrasonic motor was introduce by v.v lavrinko in 1965. • An Ultrasonic motor is a type of electric motor formed from the ultrasonic vibration of a component, the stator being placed against another, the rotor depending on the scheme of operation. • Conversion of electric energy into motion by inverse piezoelectric effect.
  4. 4. • To obtain the levels of torque speed characteristics of USM using conventional motors we require to add a gear system to reduce the speed. • These characteristics of USM makes them attractive for robotic applications where small motions are required. • This motor achieves high speed and drive forces, while still permitting the moving part to be positioned with high accuracy.
  5. 5. • Piezoelectricity – generation of voltage in response of mechanical stress. • The word is derived from the Greek piezein, which means to squeeze or press. • This effect is also reversible. • Deformation is only 0.1 % of the original dimension. • Piezoelectric material- quartz(SiO2), barium titanate (BaTiO3) lead zirconate titanate and occasionally lithium niobate . The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry.
  6. 6. Electromagnetic motors are notorious for consuming high amount of power and creating high ambient motor temperatures respect to USM The electromagnetic motors produce strong magnetic fields which cause interference. Ultrasonic motors use piezoelectric effect and hence no magnetic interference. Electromagnetic motor has high input to output energy loss ratios USM High positional accuracy respect to Electromagnetic Motor.
  7. 7. • Generation of gross mechanical motion through the amplification and repetition of micro-deformations of active material. • The active material induces an orbital motion of the stator at the rotor contact points . • Frictional interface between the rotor and stator rectifies the micro-motion to produce macro-motion of the ROTOR. • Working frequency-20 KHz to 10 MHz • Amplitude of the actuator motion – 20 to 200nm
  8. 8. USM
  9. 9. EQUIVALENT CIRCUIT OF USM STATOR  Cd is the capacitance due to the dielectric property of piezo crystal i.e tank capacitance.  Rm,Cm,Lm are the resistance ,capacitnce & inductance of stator.  Their combined impedance is given by ( + 1 / + ).
  10. 10. OPERATING PRINCIPLE a) Based on the use of reverse piezo-electric effect for continuous conversion of electric power into mechanical energy. b) The process of energy conversion can be seperated into two parts:  Ultrasonic vibration generation  Conversion of this vibration into the slider(rotor) movement.
  11. 11. OPERATING PRINCIPLE  When a voltage is applied to a peizoelectric- ceremic element,alternating expansion and contraction occur either in the ceremic body itself or in the elastic body  The magnitude of this oscilation is very small  The conversion of ultrasonic vibration in the rotor movement is based on the elliptic motion displacement of the surface points of the contact zone between stator and rotor  The displacement can be produced independently through two individual vibrating bodies or by a single vibrator
  12. 12. ULTRASONIC MOTOR STANDING WAVE TYPE LINEAR MOTOR ROTARY MOTOR TRAVELLING WAVE TYPE LINEAR MOTOR ROTARY MOTOR
  13. 13.  This type of motors use three groups of crystals: two of which are Locking and one Motive.  First, one group of locking crystals is activated — this gives one locked side and one unlocked side of the 'sandwich'.  Next, the motive crystal group is triggered and held — the expansion of this group moves the unlocked locking group along the motor path. This is the only stage where motor movement takes place.
  14. 14. Standing wave USM  Representation u( x, t) = A coskx coswt  It is also referred as vibratory coupler type or wood pecker type.  A vibrator is connected to the piezoelectric driver,it produces bending, so its tip produces flat elliptical motion to drive the rotor.
  15. 15. LINEAR TYPE STANDING WAVE USM  Rectangular plate ultrasonic motor.  Resonant frequency- 98kHz.  Efficiency-65%  Applications- card or paper senders.
  16. 16. ROTATING TYPE STANDING WAVE USM  Torsional coupler ultrasonic motor.  Provides high speed than linear motors because of high frequency (160kHz)& amplified vibration.  Provides speed of 1500 rpm, torque of 0.08 Nm & efficiency of 80%.
  17. 17.  This type of motor commonly known under the names of Inchworm, Piezo LEGS or PiezoWalk motors
  18. 18. STANDING WAVE USM  Low cost  one vibration source  High efficiency  Unidirectional
  19. 19. TRAVELING WAVE USM  Superposition of multiple standing wave create a traveling wave.  Representation of travelling wave U(x ,t)= A cos(k x) cos(wt) + A cos(k x - 90) cos (wt-90).  Phase difference is 90 degree pressur e
  20. 20. • Superposition of multiple standing wave create a traveling wave. • Representation of travelling wave U(x ,p)= A cos(k x) cos(wt) + A cos(k x - 90) cos (wt-90). • Phase difference is 90 degree
  21. 21. •The active material excites a traveling flexural wave within the stator that leads to elliptical motion of the surface particles. •Teeth are used to enhance the speed that is associated with the propelling effect of these particles. •The rectification of the micro-motion an interface is provided by pressing the rotor on top of the stator and the frictional force between the two causes the rotor to spin.
  22. 22. TRAVELLING WAVE USM  Requires two vibrating source.  Controllable in both direction.  Silent operation, so suitable to video cameras with microphone.  Thinner design, leading to space saving.  Low efficiency.
  23. 23. ADVANTAGES DISADVANTAGES  Low cost  High efficiency  No magnetic interference  Compact size  High torque/weight ratio  Energy saving  Use of high frequency power supply  Less constancy  Drooping torque speed characteristic  Supppression of heat is required
  24. 24. • Camera auto focus lenses • Driving fluid • Watch motors and compact paper handling. • Optoelectronics area • In micro surgery and sensor scanning.
  25. 25. CONCLUSION  These motors are advantageous.  Electromagnetic interference is not there.  It is in great demand in the area of automation & miniaturiztion.  Energy efficient.  Light weight & compact size

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