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Joined: Dec 2008
17-09-2009, 01:22 AM
All of us know that motor is a machine which produces or imparts motion, or in detail it is an arrangement of coils and magnets that converts electric energy into mechanical energy and ultrasonic motors are the next generation motors.
In 1980,the world's first ultrasonic motor was invented which utilizes the piezoelectric effect in the ultrasonic frequency range to provide its motive force resulting in a motor with unusually good low speed, high torque and power to weight characteristics.
Electromagnetism has always been the driving force behind electric motor technology. But these motors suffer from many drawbacks. The field of ultrasonic seems to be changing that driving force.
DRAWBACKS OF ELECTROMAGNETIC MOTORS
Electromagnetic motors rely on the attraction and repulsion of magnetic fields for their operation. Without good noise suppression circuitry, their noisy electrical operation will affect the electronic components inside it. Surges and spikes from these motors can cause disruption or even damage in nonmotor related items such as CRTs and various types of receiving and transmitting equipments. Also , electromagnetic motors are notorious for consuming high amount of power and creating high ambient motor temperatures. Both are undesirable from the efficiency point of view. Excessive heat energy is wasted as losses. Even the efficiently rated electromagnetic motor has high input to output energy loss ratios.
Replacing these by ultrasonic motors would virtually eliminate these undesirable effects. The electromagnetic motors produce strong magnetic fields which cause interference. Ultrasonic motors use piezoelectric effect and hence no magnetic interference.
PRINCIPLE OF OPERATION
Many polymers, ceramics and molecules are permanently polarized; that is some parts of the molecules are positively charged, while other parts are negatively charged. When an electric field is applied to these materials, these polarized molecules will align themselves with the electric field, resulting in induced dipoles within the molecular or crystal structure of the material. Further more a permanently polarized material such as Quartz(SiO2) or Barium Titanate(BaTiO3) will produce an electric field when the material changes dimensions as a result of an imposed mechanical force. These materials are piezoelectric and this phenomenon is known as Piezoelectric effect. Conversely, an applied electric field can cause a piezoelectric material to change dimensions. This is known as Electrostriction or Reverse piezoelectric effect. Current ultrasonic motor design works from this principle, only in reverse.
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Joined: Apr 2012
04-07-2012, 02:36 PM
Ultra Sonic Motor
Ultra Sonic Motor.doc (Size: 347.52 KB / Downloads: 62)
Ultra sonic motor is a newly developed motor, and it has excellent performance and many useful features, e.g.: high-torque density, low speed, compactness in size, no electromagnetic interferences, and so on. USM is a kind of piezo motor. The proposed speed control scheme is assumed for these applications because they require quick and precise speed control of actuators for various load conditions. A speed control method of USM using adaptivecontrolisproposed.
Artificial Neural Network (ANN), which follows the biological neural cells in brain, consists of a number of neurons and weighted links, and it has a good potential for control applications because it can approximate the non-linear input-output mapping of the plant. Accordingly, ANN has been applied widely in the field of power electronics control.
Piezoelectric ultrasonic motors (PUMs) have a number of advantages over electromagnetic motors. PUMs can achieve positioning accuracies in the range of several tens of nanometerrs.
They hold their positions even when powered down and thus consume less energy. PUMs can be constructed with significantly fewer parts.
The efficiency of electromagnetic motors falls as their dimensions are reduced, but that of PUMs stays virtually constant . Linear electromagnetic motors are very difficult to design; in contrast linear PUMs are quite simple.
Interest in PUMs is growing, especially for use as miniature drives in mass-produced consumer electronic products.
Miniaturized Piezoelectric Ultrasonic Motors
Physik Instrumente (PI) has been active inpiezoelectric ultrasonic motor R&D for many years.Minature PUMs have also been subject to at PI. Several years ago PI developed a piezoelectric rotary traveling-wave motor with a stator measuring only 3x3 mm . That motor uses what is known as the tangential-axial oscillation mode of the piezoelectric hollow cylinder.
A traveling wave is set up in the stator with the help of three electrical signals which are 120° out of phase. In addition to rotary ultrasonic motors, PI is also developing linear ultrasonic motors.
Working Principle and Design of the NewUltrasonic Motor
Fig. 3a shows a CAD model of the newly developed ultrasonic motors . These motors are of very simple design, consisting of two basic parts: the actuator (stator) and the sled (spring bonded to two sliders), the moving part of the motor.
The actuator consists of a rectangular piezo-ceramic plate of size L×W×0.5L polarized in the thickness direction. The two large faces of the plate are covered by electrodes. On one (top, in Fig. 3a) are the two exciter electrodes, each covering half of the surface. The “bottom” surface (not visible) has a single electrode that serves as a common drain
The actuator plate has guide grooves cut in the long edges. The sled has two sliders which are pressed against the ceramic actuator by the integrated spring. The entire motor consists of the piezoceramic plate and the moving sled, guided along the integrated grooves in the plate.
. Measurement with 3D Scanning Vibrometer
Finite Element Method (FEM) programs have proven to be essential tools for the development of ultrasonic motors. All the simulations, calculations and the optimization of ultrasonic motors were done with the help of ANSYS FEM software. Fig. 4a shows an FEM simulation of the stator of a 9 mm motor.
Drive Circuitry for the Motor
Fig. 5a shows the impedance characteristic curve of the motor with and without the sliders. The resonant frequency used was 470 kHz. The fact that the resonant frequency is influenced by external conditions like temperature, makes necessary the development of electronics that automatically adjusts to the motor’s resonant frequency.
Joined: Apr 2012
22-08-2012, 10:59 AM
ultrsoinc ppt.pptx (Size: 194.92 KB / Downloads: 30)
It has been known for more than 30 years.
The first ultrasonic motor was introduce by v.v lavrinko in 1965.
Conversion of electric energy into motion by inverse piezoelectric effect.
This motor achieves high speed and drive forces,while still permitting the moving part to be positioned with high accuracy.
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.
Piezoelectric material- quartz(SiO2), barium titanate (BaTiO3).
PIEZOELECTRIC MOTOR NOTION
Change in shape of piezoelectric material when electric field is applied.
It can be abbreviated as USM.
It is driven by ultrasonic vibration of transducer.
The ultrasonic vibration is transformed into output torque (in rotary USM) or thrust (in linear USM) by the friction between the stator and the rotor (in rotary USM) or the moving part (in linear USM).
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
For linear motion bidirectional drives are required .
More than two actuators are used.
These actuators must have some phase difference
It can be obtained by superimposing to oscillations in a single resonator.
Stator is hybrid construction consisting of several actuators.
These motors are very advantageous.
Electromagnetic interference is not there.
It is in great demand in the area automation and miniaturization.
These motors are low cost
Joined: Oct 2012
10-12-2012, 12:09 PM
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