Piezoelectric motors are used in many industrial and commercial applications. Various piezoelectric motors are available in the market. All of the piezoelectric motors use the inverse piezoelectric effect, where microscopically small oscillatory motions are converted into continuous or stepping rotary or linear motions. Methods of obtaining long moving distance have various drive and functional principles that make these motors categorized into three groups: resonance-drive (piezoelectric ultrasonic motors), inertia-drive, and piezo-walk-drive. In this review, a comprehensive summary of piezoelectric motors, with their classification from initial idea to recent progress, is presented. This review also includes some of the industrial and commercial applications of piezoelectric motors that are presently available in the market as actuators.
Piezoelectric motors use the inverse piezoelectric effect, where microscopically small periodical displacements are transferred to continuous or stepping rotary or linear movements through frictional coupling between a displacement generator (stator) and a moving (slider) element. Although many piezoelectric motor designs have various drive and operating principles, microscopic displacements at the interface of a stator and a slider can have two components: tangential and normal. The displacement in the tangential direction has a corresponding force working against the friction force. The function of the displacement in the normal direction is to increase or decrease friction force between a stator and a slider. Simply, the generated force alters the friction force due to a displacement in the normal direction, and the force creates movement due to a displacement in the tangential direction. In this paper, we first describe how the two types of microscopic tangential and normal displacements at the interface are combined in the structures of different piezoelectric motors. We then present a new resonance-drive type piezoelectric motor, where an octagonal plate, with two eyelets in the middle of the two main surfaces, is used as the stator. Metallization electrodes divide top and bottom surfaces into two equal regions orthogonally, and the two driving signals are applied between the surfaces of the top and the bottom electrodes. By controlling the magnitude, frequency and phase shift of the driving signals, microscopic tangential and normal displacements in almost any form can be generated. Independently controlled microscopic tangential and normal displacements at the interface of the stator and the slider make the motor have lower speed-control input (driving voltage) nonlinearity. A test linear motor was built by using an octagonal piezoelectric plate. It has a length of 25.0 mm (the distance between any of two parallel side surfaces) and a thickness of 3.0 mm, which can produce an output force of 20 N.
14ï43dç14nIn manufacturing integrated circuits, the tendency is toward smaller and smaller structures.Therefore the requirements for accurate micropositioning in lithography and wafer handling are growing more stringent. In many cases even a positioning accuracy of 0.1 micron is not good enough.But traditional precision mechanical positioners come to their limits in this range. Play, backlash, elasticity, friction and temperature changes can only be partially eliminated.One possible way to overcome these problems is with positioners based on the inverse piezo effect. Elazskl.eçirig_trAnalAlsszPiezoelectric translators convert electrical energy directly in a linear movement without any gear heads or spindles.The electrical circuit response of the piezoelectric translator in quasi-static operation is the same as a capacitor with a capacitance of 3 nF to 3 uF, depending on the maximum travel and load capability of the piezoelectric translator.Equation (1) describes the relationship between the mechanical movement of the piezoelectric translator and the applied electrical field. This equation is valid for small amplitudes and slow variations of the electric field. S = sT + dE (1) S -strain d -piezoelectric constant s -elastic constant E -electric field T -stress Piezo electric translators offer many advantages in micropositioning applications: -Unlimited resolution because of analog operation -Very fast response time for the motion (us -ms range) -Compact and very stiff structure in a sandwich -type structure -High efficiency -No energy consumption when expanded But they also have some disadvantages: -Limited range of movement (about 0.15% of the total length) -Non -linearities and hystersis at higher electric fields (about 15%) -Creeping in a constant applied electric field -Temperature dependence of the expansion SPIE Vol. 565 Micron and Submicron Integrated Circuit Metrology (1985) / 41In manufacturing integrated circuits, the tendency is toward smaller and smaller structures. Therefore the requirements for accurate micropositioning in lithography and wafer handling are growing more stringent. In many cases even a positioning accuracy of 0.1 micron is not good enough. But traditional precision mechanical positioners come to their limits in this range. Play, backlash, elasticity, friction and temperature changes can only be partially eliminated. One possible way to overcome these problems is with positioners based on the inverse piezo effect.Piezoelectric translators convert electrical energy directly in a linear movement without any gear heads or spindles.The electrical circuit response of the piezoelectric translator in quasi-static operation is the same as a capacitor with a capacitance of 3 nF to 3 uF, depending on the maximum travel and load capability of the piezoelectric translator.Equation (1) describes the relationship between the mechanical movement of the piezoelectric translator and the applied electrical field. This equation is valid for small amplitudes and slow variations of the electric field. S = s...
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