Comparison of Piezo Motor Types
| Motor Type | Motion Principle | Relative Force | Holding Without Power | Speed | Precision (Resolution) | Repeatability (Closed Loop) | Pitch/Yaw Stability |
|---|---|---|---|---|---|---|---|
| Inertial (Stick-Slip) | Friction-based stick/slip motion | Low–Medium | High | Low–Medium | ~5 nm to 50 nm | ±20 nm to ±200 nm | Moderate to Poor (±25–100 arcsec) |
| Ultrasonic Piezo | Standing-wave resonant motion | Medium | Low | High | ~1 nm to 10 nm | ±10 nm to ±50 nm | Good (±10–50 arcsec, depends on guide) |
| Piezo LEGS® (Walking) | Sequential piezo-actuated steps | High | High | Medium | <1 nm possible | ±1 nm to ±10 nm | Excellent (±1–10 arcsec with flexures) |
Technical Notes
Repeatability
- Defines a motor’s ability to return to the same target position after repeated motion cycles.
- Essential in systems requiring stable and predictable positioning, such as microscopy and semiconductor alignment.
- Optimal performance is achieved through closed-loop feedback utilizing high-resolution encoders.
Precision (Resolution)
- Depends on step size and drive electronics.
- Sub-nanometer resolution is possible in Piezo LEGS and ultrasonic systems with proper feedback.
- Inertia motors have coarser steps due to stick-slip dynamics.
Pitch/Yaw Stability
- Refers to unintended angular deviations during linear motion (rotations around lateral and vertical axes).
- Important in applications involving optics, scanning, or submicron alignment.
- Flexure-guided designs offer minimal pitch/yaw error—especially in Piezo LEGS motors.
Design Factors That Influence Performance
- Mechanical Guidance: Flexures > linear bearings > unguided systems
- Load Symmetry: Off-axis or uneven loading increases angular error
- Drive Electronics: Affects smoothness, responsiveness, and noise
- Feedback Systems: Capacitive or interferometric encoders provide optimal control