Piezo Actuators & Their Limitations in Digital Microscopy

Join Kevin McCarthy, Chief Technology Officer for Dover Motion, as he covers the commercial implementations of piezo actuators and, more importantly, their limitations.

The first piezo actuator technology Kevin covers is the direct piezo stack. This product is made of small, thin piezoelectric disks. This piezo stack is very good at pushing, but cannot pull. Because of this, the piezo stack requires a spring to compress and preload the stack. Piezo stacks can be operated in an open-loop mode. However, it does not have a linear response.

Piezo actuators that operate in an open-loop mode are subject to a " creep " problem. This problem is solved by adding a position feedback device, typically either a strain gauge or a capacitance gauge allowing for closed-loop control. The addition of position feedback increases the cost and complexity of the system.

Next in the video, Kevin covers lever-amplified piezo actuators. These have a small piezo stack within them and employ lever amplification typically using a flexure to translate a small motion into a large motion. While lever amplification increases the stroke, it is still far short of the travel preferred in a positioning application.

We contrast the core technologies at the heart of direct piezo stack actuators and lever amplified piezo actuators with linear motor equivalents. In most piezo actuators, the motor is piezoelectric, the guideways are flexures, and the feedback is either a strain gauge or a cap gauge. All of these technologies are limited stroke technologies.

Dover Motion’s direct drive stages have a linear motor, crossed roller guideways, and linear encoder to provide a very accurate stage with resolution down to 1.25 nm, and travels that can exceed 1 meter.

Timeline:
0:00 - Introduction
0:23 - Direct piezo stack technology
4:10 - Piezo stage applications
4:26 - Lever amplified piezo actuators
6:38- Contrast to linear motor
8:30 - Dover Motion DOF-5 Focusing Stage
9:39 - Outro


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