Piezoelectric motors

Adhesives have been classified according to their applications. Epoxy is a compatible adhesive for stainless steel and ceramics, as used in the piezoelectric motor industry. Epoxy adhesives of different characteristics are found. Epoxy-polysulfone and epoxy-phenolics both exhibit thermosetting properties, providing stronger bonding properties with ceramics. 

Piezomotors can produce elliptical motions either at the mechanical resonance (leading to ultrasonic motors) or in quasistatic (leading to stepping piezoelectric motors, so-called Inchworm ) [14]. 

The use of this motor in direct drive means that the complete function is obtained without any additional gear mechanism (for speed reduction, or for converting rotation in translation). Optics is probably the domain where the use of the piezoelectric motors is the most advanced. The most famous example, is the Canon camera, which includes an auto focus zoom based on a piezoelectric ultrasonic motor (USM) since 1992 (Fig. 6.21) [12]. 

Following a principle used in piezoelectric ultrasonic motors [60], T. Aku-ta [61] has built the first magnetostrictive friction motor. This stator is made of pairs of orthogonal actuators excited with sinusoidal 90° phase-shift currents, which produce an elliptical vibration. The modeling of such magnetostrictive stators [42] has shown that in quasi-static operation a good elliptical motion is produced. It has also been shown that there are many coupled modes, but none of them provides a satisfactory elliptical motion. Therefore, unlike piezoelectric motors, this motor cannot operate at resonance. As a consequence and in relation to the previous analysis of power (Fig. 6.34), the efficiency is comparatively weak. Its other characteristics are a speed of 40°/s and a torque of 1.8 Nm [62]. 

The first linear micromotor, based on magnetostrictive thin films deposited on a 7 pm polyamide film, was built in Japan in 1994 [66]. The 13 mm long protot3rpe used a 200 Hz vibration induced by magnetostriction to obtain one-way motion at 5 imn/s. This is a mode conversion ultrasonic motor (MCUM) according to the Japanese classification of piezoelectric motors. 

Piezoelectric motors (inchworm, standing or propagating wave modes, vibratory coupler ( woodpecker ) or surface wave ( surfing )-lype motors)... 

Closed-bore MRI manipulation requires actuators with excellent MRI compatibility because of their proximity to the image center. Piezoelectric motors have been reported to cause image distortion in closed-bore MRI [19]. Piezoelectric motors are also relatively slow, complex and expensive. Manipulators using pneumatics have had limited success in conjunction with closed-bore MRI [20, 21]. The main drawbacks to this approach are control issues due to the imprecision and compliance of pneumatics. Recent advances have been made using pneumatic stepper motors to eliminate these effects [22]. However, pneumatic systems, using continuous cylinders or step motors, tend to be complex and expensive. 

Wendt, O., Dellinger, J., Luth, T.C., et al. (2000) The effects of the use of piezoelectric motors in a 1.5-Tesla high-field magnetic resonance imaging system (MRI), Biomed Tech, 45, 20-5. 

One of the tremendous advantages of working with nanoporous platforms, particularly nanopipettes, is the ease with which they can be manipulated spatially through the use of piezoelectric motors. Piezos offer subnanometer control and can be used to move a nanoprobe in all three spatial dimensions such that the nanoporous probe is positioned extremely close to a sample or area of interest thus, extremely localized functions and measurements can be performed. This ease of 3-D positioning renders nanopores excellent tools to deliver analytes to or sample from localized regions of a sample, pattern a surface, and produce topographical and chemical maps at a sample-solution interface. 

Nanoporous systems have been applied to numerous microscopy techniques. Nanopipettes often are used as probes in SPMs due to the ease of fabrication, small nanopore dimensions at the tip, and ease of spatial positioning via piezoelectric motors. However, this review will focus briefly on SPM techniques which involve electrochemical measurements, namely, SECM, SICM, and the hybrid of the two (SECM-SICM). 

To measure friction and shear response, one has to laterally drive one surface and simultaneously measure the response of a lateral spring mount. A variety of versions have been devised. Lateral drives are often based on piezoelectric or bimorph deflection [13, 71] or DC motor drives, whereas the response can be measured via strain gauges, bimorphs, capacitive or optical detection. 

Medical Ultrasound Micro-positioning and Micro-motors Piezoelectric Transformers Active Noise and Vibration Damping SUGGESTED READING References on Silicon Devices Problems for Chapter 6... 

Electricity production, using hydrothermal steam, 12 529-530 Electricity supply, operation and maintenance of, 10 159 Electric melting, 23 253 Electric motors, 10 149 Electric polarization, in piezoelectric materials, 22 709-710 Electric potential, 9 739 Electric potential difference, exponents of dimensions, 8 585t Electric power. See also Electricity production... 

We have to make a distinction here between electric controllers (e.g. PID controllers) with a proportional valve as actuator and mechanical diaphragm controllers. In a regulation system w/ith electric controllers the coordination between controller and actuator (piezoelectric gas inlet valve, inlet valve A/ith motor drive, butterfly control valve, throttle valve) is difficult because of the very different boundary conditions (volume of the vessel, effective pumping speed at the vessel, pressure control range). Such control circuits tend to vibrate easily when process malfunctions occur. It is virtually impossible to specify generally valid standard values. 

Fig. 12.8. The Inchworm . It consists of an alumina shaft, slid inside a piezoelectric tube, which consists of three sections. Top, a photograph of the Microlnchworm Motor, actual size. Right, walking mechanism (1) Clamp the left-hand side by applying a voltage to section 1. (2) Extend section 2. (3)...

Uchino, K. (1997) Piezoelectric Actuators and Ultrasonic Motors, Kluwer Academic Publishers, London. 

In the SFA, the distance between the surfaces is controlled by use of a three-stage mechanism of increasing sensitivity a coarse motor, a fine motor and a piezoelectric crystal tube, the latter allowing for distance control with an accuracy of 0.1 nm. The movement of the piezoelectric crystal tube is calibrated at large surface separations where no force is acting between the surfaces. For calibration it is an acceptable approximation that the expansion of the piezoelectric crystal (AD) is linear in response to an applied voltage (AF) ... 

---