Piezomotors are a Better Alternative in Many Applications

Background

The word piezo comes from the Greek word piezein, which means to squeeze or press. The piezoelectrical effect is best described as the ability of some materials (e.g. piezo ceramics) to generate an electrical charge in response to a mechanical force (e.g. being squeezed or pressed). The piezoelectric effect is reversible, in that materials exhibiting the effect also exhibit the reverse and/or inverse piezoelectric effect. Thus they change shape or size when excited by an electric charge.

Although, the inverse piezoelectric effect has been well known and studied for some years, it is only relatively recently that commercial devices incorporating piezo technology have begun to find practical applications in everyday devices (e.g. focusing mechanism of certain digital cameras, industrial valves, toys etc.).

This situation is now changing rapidly as an increasing number of companies search for alternatives to conventional electromagnetic motors, in order to solve modern day problems associated with the growing demand for; better performance, energy efficiency, miniaturization, and green technology.

In a growing number of instances companies are finding that piezomotor technology offers the only efficient and cost-effective answers to these problems.

Piezomotors offer a high performance, cost-effective, and reliable solution in many precision motion and flow control systems. Applications are numerous within diversified industries, including aerospace, industrial, medical device, optics, telecommunications, semiconductor, and nanotechnology.

Technology

While there are several types of piezomotor on the market, the design and technology employed by DTI in its standing wave-type piezomotors is quite unique and provides certain key advantages in both use and manufacturability. Available in a variety of sizes and configurations, DTI's full line of rotary and linear piezomotors and piezoelectric valves address many of the modern-day requirements for motion control systems.

DTI's piezomotors, whether rotary or linear, work on the same principle of electrically induced excitation of ultrasonic standing wave(s) within a piezoelectric resonator/ceramic. A schematic of one of DTI's rotary piezomotors with a ring-shaped piezoresonator (1) and stainless steel pushers (3) is shown in the figure. Pushers (3) are attached to the piezoresonator through a vibrational shell (2). An ultrasonic radial standing wave is electrically excited in the resonator causing the ring to expand and contract in radial direction, stimulating movement of the pushers along the radius. Because of their elasticity, the pushers vibrate with the same frequency, although phase shifted, in a direction orthogonal to the radius of the ring. The superposition of the two orthogonal movements results in elliptical movements (5) of the pushers. Because the pushers are held pressed (spring loaded) against the rotor (4), their movement, via friction at the pusher contact area, causes rotation of the rotor.

Key Benefits of Piezoelectric Motors vs. Electromagnetic Motors

Performance	Scalable Design	Low Cost
• 1000 X’s Better Resolution. • 100 X’s Faster Reaction Time. • 10 X’s Greater Torque/Force.	• 1 m O.D. to < 10 mm O.D. • Rotary and Linear Designs.	• Competitive pricing for most models.
Unique Properties	Low Voltage & Efficient	Environmental
• No gear-head required. • Non-magnetic (options available). • Wide temperature tolerance. For further information visit: http://www.discovtech.com	• 12 V DC, miniature PCB design accommodates many applications. • Low Energy Requirements.	• Ceramic Design Eliminates Ferrous or Copper Metals