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Piezo Impact Drive motor/stick slip motor

http://www.piezo-motor.net/?onl_goog_lin_piez_mot

Introduction

Impact Drive Mechanism (IDM) is a method for moving an object under friction by impulsive

force. It utilizes static friction and impulsive force caused by the rapid displacement of an

actuator. The motion mechanism basically consists of three parts: the main body, actuator and

the inertial weight. When the actuator makes rapid extension or contraction, a strong inertial

force is generated and the main body is moved against static friction. When the actuator makes

slow retraction, the inertial force could be smaller than static friction so that the main body keeps

the position. Repeating those fast and slow actuator displacements carries out the motion.

The mechanism is able to control the minute motion of several nanometer and at the same time

has virtually unlimited movable range. The mechanism can be extended to multiple degree-of-

freedom systems with multiple actuators and counter weights. The IDM is considered to be a

suitable mechanism for micro systems since its construction is quite simple.

The mechanism generates impulsive force when moving. We have utilized such impulsive force

to develope a printed board positioning device, a centering system for workpieces on rotating

supports, and a piezo-electric maicro manipulator.

Operation Principle

Figure 1 shows a basic motion principle of the Piezo Impact Drive Mechanism. The motion

mechanism consists of three components: the main body, the actuator and the inertial (counter)

weight. The main body is laid down on the guiding surface with only the friction acting between

the surface. On the one end of the main body an actuator is attached. The weight does not touch

the surface.

The processes of the motion are described as follows:

(a) The cycle starts with the actuator in extended state.

(b) The actuator makes slow contraction so that the inertial force caused by the contraction

should not exceed the static friction. The main body keeps the position.

(c) At the end of contraction process, a sudden stop of the motion is made to small move the

main body.

(d) Then, a rapid expansion of the actuator causes impulsive inertial force, which results in the

step-like motion of the main body.Making slow extension and rapid contraction can carry out

motion toward the other direction. The motion amplitude of the actuator can control the step size

of the motion. Repeating those processes through (a)-(d) a long distance motion is made

possible.

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Figure:1 (duplicate)

Motion characteristics

Figure 2 shows a linear motion device of Impact Drive Mechanism for basic experiments.

Employed piezo-electric element has size of 10 x 10 x 20 [mm]. It generates 16m displacement

at 150V applied voltage.

Fig. 3 shows a nanometer-scale continuous step motion. The size of the steps is about 4nm.

Controlling voltage amplitude applied to the piezoelectric actuator, nanometer motion can be

controlled. The maximum load capacity of the Impact Drive Mechanism depends on the static

friction. If the static friction is large enough, the Impact Drive Mechanism can climb up the

vertical surface.

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Features

Some remarkable features are listed in the following.

1. Simple structure 2. Nano meter positioning, long movable range, and high-speed motion can be realized at

the same time

3. Ease of making multi degree of freedom mechanism(eg. figure 4) 4. No energy requirement for keeping constant position

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Inch worm motor

http://en.wikipedia.org/wiki/Inchworm_motor

The inchworm motor is a device that uses piezoelectric actuators to move a shaft

with nanometer precision.

In its simplest form, the inchworm motor uses three piezo-actuators (2 and 3, see Figure 1.)

mounted inside a tube (1) and electrified in sequence to grip a shaft (4) which is then moved in a

linear direction. Motion of the shaft is due to the extension of the lateral piezo (2) pushing on

two clutching piezos (3).

Working principle:

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The actuation process of the inchworm motor is a six step cyclical process after the initial

relaxation and initialization phase. Initially, all three piezos are relaxed and unextended. To

initialize the inchworm motor the clutching piezo closest to the direction of desired motion

(which then becomes the forward clutch piezo) is electrified first then the six step cycle begins as

follows (see Figure 2.):

Step 1. Extension of the lateral piezo.

Step 2. Extension of the aft clutch piezo.

Step 3. Relaxation of the forward clutch piezo.

Step 4. Relaxation of the lateral piezo.

Step 5. Extension of the forward clutch piezo.

Step 6. Relaxation of the aft clutch piezo.

Electrification of the piezo actuators is accomplished by applying a high bias voltage to the

actuators in step according to the "Six Step" process described above. To move long distances

the sequence of six steps is repeated many times in rapid succession. Once the motor has moved

sufficiently close to the desired final position, the motor may be switched to an optional fine

positioning mode. In this mode, the clutches receive constant voltage (one high and the other

low), and the lateral piezo voltage is then adjusted to an intermediate value, under continuous

feedback control, to obtain the desired final position.

Linear motor:

http://www.etel.ch/linear-motors/principle/

Principle:

Linear motors are a special class of synchronous brushless servo motors. They work like torque

motors, but are opened up and rolled out flat. Through the electromagnetic interaction between a

coil assembly (primary part) and a permanent magnet assembly (secondary part), the electrical

energy is converted to linear mechanical energy with a high level of efficiency. Other

common names for the primary component are motor, moving part, slider or glider, while the

secondary part is also called magnetic way or magnet track. Since linear motors are designed to

produce high force at low speeds or even when stationary, the sizing is not based on power but

purely on force, contrary to traditional drives.

The moving part of a linear motor is directly coupled to the machine load, saving space,

simplifying machine design, eliminating backlash, and removing potential failure sources such as

ballscrew systems, couplings, belts, or other mechanical transmissions. Finally, the bandwidth

and the stiffness of the motion system are much higher, giving better positional repeatability and

accuracy over unlimited travel at higher speeds. Given that frameless linear motors do not

include a housing, bearings, or feedback device, the machine builder is free to select these

additional components in order to best fit the application requirements.

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Ultrasonic motor:

http://www.seminarsonly.com/Labels/How-Ultrasonic-Motor-Works.php

Construction:

Ultrasonic motor construction tends to be simpler than EM type motors. Fewer assembly parts

mean fewer moving parts and consequently less wear. The number of components required to

construct an USM is small thereby minimizing the number of potential failure points. As the

ultrasonic motor uses ultrasonic vibrations as its driving force, it comprises a stator which is a

piezoceramic material with an elastic body attached to it, and a rotor to generate ultrasonic

vibrations. It therefore does not use magnets or coils. Therefore there is no problem of magnetic

field and interference as in the case of electric motors. In ultrasonic motors, piezoelectric effect

is used and therefore generates little or no magnetic interference.

Principle Of Operation

PIEZOELECTRIC EFFECT

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

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material to change dimensions. This is known as Electrostriction or Reverse piezoelectric effect.

Current ultrasonic motor design works from this principle, only in reverse.

When a voltage having a resonance frequency of more than 20KHz is applied to the piezoelectric

element of an elastic body (a stator),the piezoelectric element expands and contracts. If voltage is

applied, the material curls. The direction of the curl depends on the polarity of the applied

voltage and the amount of curl is determined by how many volts are applied. Eg:Quartz,Rochelle

salt,Tourmaline,Lead Zirconium Titanate. Therefore does not make use of coils or magnets. It is

a motor with a new concept that does not use magnetic force as its driving force. It also

overcomes the principles of conventional motors. The working principle is based on a traveling

wave as the driving force. The wave drives the comb of the piezoelectric ring. When applied, the

piezoelectric combs will expand or contract corresponding to the traveling wave form and the

rotor ring which is pressed against these combs start rotating.

Typical Applications for PiezoWalk Motors / Actuators

Semiconductor Technology

Nanoalignment Systems with Long Travel Ranges

Nano imprint

CD Testing

Mask and Wafer Alignment

Objective Precision Positioning

Lithography

Optics Testing

Biotechnology, Life Science, Medical Design, Medical Technology

Flow Cytometry

Cell Sorting

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Electrophysiology, Patch Clamp

Intra-Cell Metrology

Cell Penetration

Microdosing

Handling

OCT, WLI

Diagnostics

Dermatology

Ophthalmology

Nanotechnology, Nanofabrication, NanoAutomation

Nanoimprint

Nanoassembly

Nanofabrication

Nanojoining

Nanomechanics

Nanomaterials Testing

Microgrippers, Manipulators

Aeronautics, Image Processing, Cryogenic & Vacuum Environments

Microwave Antenna Precision

Alignment

Precision Linear Actuators

Beamline Experiments

Angular Alignment

Sample Positioning