It's easy to overlook the SQUIGGLE SQL-1.5-6 motor from New Scale Technologies because it's really, really small.
Measuring just 1.5 x 1.5 x 6 mm, this piezoelectric linear motor is in fact the smallest of its kind. “It's about two times smaller than the next smallest ultrasonic motor,” says Dave Henderson, New Scale's president and chief engineer.
Though small, the motor doesn't skimp on capabilities. It has a push force of 20 gm, which Henderson claims is about 10 times better than previous ultrasonic motors. And this SQUIGGLE motor also ups the ante on accuracy and precision with a positioning resolution of 0.5 µm. “That's about 10 times better than other piezoelectric motors and 20 times better than small electromechanical motors,” Henderson says.
Also important for engineers working on miniature motion systems, the tiny SQUIGGLE keeps things simple. Its patented design consists of a threaded nut surrounded by piezoelectric plates and a matching threaded screw. Two-phase drive signals at ultrasonic frequencies excite the PZT plates which then cause the nut to vibrate a bit like a Hula-Hoop. This vibrating motion makes the screw rotate and translate bidirectionally within the nut, providing the motor's push force and positioning capabilities.
In all, this linear motor has just seven parts, including a position sensor. By contrast, even the tiniest system based on electromechanical stepper motors and gearing components might contain dozens of components.
New Scale introduced its first ultrasonic PZT model in 2003. Since then, it has managed to substantially shrink the size of its motors. According to Henderson, the SQL 1.6-6 model occupies just 1/100 the volume of the company's first piezoelectric motor. “The fundamental nature of ultrasonic motors is that they are scaleable. They don't lose their efficiency as they get smaller the way electromechanical motors do,” Henderson says.