Evolving Design Challenges with Piezoelectric Motion Devices (Part 2 of 3)
Read next: Evolving Design Challenges (Part 3 of 3)
Piezo motors require no power when inactive and maintain full blocking force and torque in this condition. At one revolution per minute a rotary motor requires less than 0.1 Watts and linear motors only need 0.06 Watts to drive at 1mm/second. This can lead to low overall power demand and is especially applicable in portable instrument applications with a battery supply; it can also be beneficial in reducing heat generation inside equipment. For the same power as a comparable sized stepper motor the piezo motor has a stall torque up to 10x greater for the same power rating.
Designed with housings made from high-performance engineering polymers and containing no magnets, copper coils or iron laminations, piezo motors are lightweight, which is a further benefit for designers of portable and handheld devices.
The monolithic piezoceramic resonators are hard materials, and the resonator drive tip pushes against surfaces with specific controlled characteristics to achieve optimized motion transfer and long life. Testing has yielded more than 15 million full cycles on linear motors still maintaining performance within specification, which equates to 450 kilometers of linear travel. Rotary motors are operational at over 40 million revolutions.
Piezo motors have very fast response times. From the applied signal they commence motion within 30 to 50 microseconds. The applied voltage leads to a rapid reaction in the piezoceramic, unlike electromagnetic motors which must generate a magnetic field and an applied force before motion can commence. This benefit has application in the automation of microscopy where up to several thousand high resolution images of a slide need to be taken to be processed and built into a single image—for example, in pathology imaging. Fast response times enable much-reduced overall processing time leading to faster throughput.
With the direct drive characteristics of the technology and the design philosophy, OEM versions of piezo motors can be made to optimize motion assemblies. This can give the designer the opportunity to greatly simplify the motion control system drivetrain and avoid rotary to linear translations and gearing.
Piezo motors can be designed with non-magnetic or low permeability materials, which make them suitable for use in MRI field applications. Application examples include motion control for medical surgical robots, precise pump control for infusion pumps and valve control for use in ventilators.